Presentation file is attached for review papers presented at the group meeting only.

87. Laser local softening of 2.0 GPa HPF steel for self-piercing rivet joining with aluminum alloy

Jin Hyeok Joo1, Minjung Kang1, Dongkyoung Lee2,3,4,5,6, and Dong Hyuck Kam1

1 Advanced Joining & Additive Manufacturing R&D Department, Korea Institute of Industrial Technology, 156 Gaetbeol-ro, Incheon 21999, South Korea

2 Department of Mechanical and Automotive Engineering, Kongju National University, Cheonan, 31080, South Korea

3 Department of Future Convergence Engineering, Kongju National University, Cheonan, 31080, South Korea

4 Department of Semiconductor Engineering, College of Engineering, Kongju National University, Cheonan 31080, South Korea

5 Center for Advanced Materials and Parts of Powder(CAMP2), Kongju National University, Cheonan, 31080, South Korea

6 Global Institute of Manufacturing Technology (GITECH), College of Engineering, Kongju National University, Cheonan 31080, South Korea

Ultra-high-strength steel (UHSS) and aluminum alloys are increasingly replacing conventional steel because environmental regulations in the automotive industry require the adoption of lightweight materials. However, joining UHSS and aluminum alloys is challenging. This study proposes a self-piercing rivet (SPR) joining technique for 2.0 GPa Hot Press Forming (HPF) steel with aluminum alloy (Al5052-H32) using laser local softening before the SPR process. The effect of varying laser parameters, such as laser power and the number of scan passes, on interlock width and bottom thickness for SPR joint, as well as tensile shear load, Vickers hardness, and microstructures, was investigated. The results show that interlock width and tensile shear load have a strong relationship. Especially, an interlock width of 0.2 mm is required to achieve proper tensile shear load. The laser softening process yielded a hardness of less than 420 Hv and a tensile load of 8.08 kN at optimal laser parameters of 200 W and 3 scan passes, to obtain proper SPR joining. Overall, the observations in this study provide a valuable contribution to the hard and lightweight materials joining at a relatively lower energy consumption and may have practical implications for the automotive industry.

86. Effects of Laser-Assisted Thermal Treatment on Self-Piercing Riveting (SPR) of DP 1180 and CFRP

Wonjung Ju*, **, Dong Hyuck Kam*, Dongchoul Kim**, Minjung Kang*, †

* Flexible Manufacturing R&D Department, Korea Institute of Industrial Technology, Incheon, 21999, Korea

** Department of Mechanical Engineering, Sogang University, Seoul, 04107, Korea

This study investigated laser-assisted thermal treatment to enhance the self-piercing riveting (SPR) joint quality for dissimilar material joining using high-strength DP 1180 steel and carbon fiber reinforced plastic (CFRP). Laser power, irradiation time, die geometry, and rivet geometry were considered as variables, and their effects were analyzed and compared. The results indicated that laser-assisted thermal treatment enabled the SPR process for high-strength steel. Increasing laser power and irradiation time expanded the heat-affected zone and reduced hardness to approximately 250 HV in the region where rivet flaring occurred, leading to martensitic transformation into ferrite and tempered martensite. Process variables significantly influenced SPR joint quality, including failure mode and fracture load. The lean die angle resulted in stable joint formation, while the steep die angle led to lower sheet detachment due to increased deformation demand. Longer rivets improved interlock formation and fracture load; however, the fracture mode shifted from rivet pull-out to CFRP failure. The results confirmed that laser-assisted thermal treatment enabled the SPR process for high-strength steel, and its effectiveness depended on die and rivet selection in ensuring robust SPR joints. 

85. An efficient decal transfer method using a roll-press to fabricate membrane electrode assemblies for direct methanol fuel cells 

Asad Mehmood a, b, Heung Yong Ha a, b *

a Center for Energy Convergence Research, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea 

b Department of Clean Energy and Chemical Engineering, University of Science and Technology (UST), Yuseong-gu, Daejeon 305-333, Republic of Korea 

This study has focused on the development of a roll-press based decal transfer method to fabricate membrane electrode assemblies (MEAs) for direct methanol fuel cells (DMFCs). This method exhibits an outstanding transfer rate of catalyst layers from substrates to the membrane, despite hot-pressing at a considerably lower pressure and for a much shorter duration than the flat-press based conventional decal method. The MEA produced by a rollpress (R-MEA) delivers an excellent single-cell performance with power densities more than 30% higher than that fabricated using a flat-press (F-MEA). The new method considerably improves catalyst active sites in both electrodes and renders a high cathode porosity. The superior pore structure of the cathode makes the R-MEA more efficient in terms of performance and operation stability under lower air stoichiometries. Moreover, MEAs can be prepared in a continuous mode using this new method due to the unique design of the roll-press. All these advantages demonstrate the superiority of this method over the conventional flat-press decal method and make it suitable for use in the commercial manufacturing of MEAs for direct methanol fuel cells. 

84. Fabrication of super hydrophilic surface on alumina ceramic by ultrafast laser microprocessing 

Qianhui Caoa, Zhengsen Wanga, Wenting Heb,*, Yingchun Guana,c,d,e,* 

a School of Mechanical Engineering and Automation, Beihang University, 37 Xueyuan Road, Beijing 10083, China 

b School of Materials Science and Engineering, Beihang University, 37 Xueyuan Road, Beijing 10083, China 

c National Engineering Laboratory of Additive Manufacturing for Large Metallic Components, Beihang University, 37 Xueyuan Road, Beijing 10083, China 

d International Research Institute for Multidisciplinary Science, Beihang University, 37 Xueyuan Road, Beijing 100083, China eNingbo Innovation Research Institute of Beihang University, Beilun District, Zhejiang 315800, China 

In this research, super hydrophilic surface on the alumina ceramic substrate is fabricated by ultrafast laser microprocessing. The laser textured surface developed by femtosecond laser in the air atmosphere is able to maintain the super hydrophilic property for 36 h and still remains hydrophilic with the contact angle of 57.9◦after 240 h. Surface morphology and chemical composition of the laser textured surface are characterized by scanning electron microscope (SEM), 3D laser scanning confocal microscope (LSCM) and X-ray photoelectron spectroscope (XPS). Results show that femtosecond laser can provide larger surface roughness in contrast with picosecond laser. Laser microprocessing can also increase the content of oxygen element and polar functional groups on the surface of the alumina ceramic substrates. Furthermore, the mechanism of the hydrophilic behavior of droplets on the laser textured surface is discussed in details and it is noted that surface morphology plays a leading role in amplifying the inherent wettability. We envision that the laser microprocessing provides a facile and effective route to develop long-term super hydrophilic surface on alumina ceramic materials. 

83. Research on Optimization Technology of Laser Stripping Parameters for PTFE Insulation in Large-Diameter Aviation Cables Based on a Thermo-Mechanical Coupled Model

Pin Li1,*, Shiwei Wang1, Peng Gao2,+, Erlin Tang3,+ and Chunlin Tian1,+

1Changchun University of Science and Technology, School of Mechanical and Electrical Engineering, Changchun, 130022, China.

2High-end Aviation Equipment Technology Innovation Center (Sichuan) Co., Ltd., General Manager, Chengdu, 610031, China.

3Chengdu Aircraft Industrial (Group) Co. Ltd., Cable Assembly Center, Chengdu, 610073, China.

The rational selection of laser wire stripping parameters is essential for achieving both high processing quality and efficiency. This study investigates the optimal laser stripping parameters for PTFE-insulated cables commonly used in aviation, employing a 405 nm semiconductor laser. A thermo-mechanical coupled finite element model was established on the COMSOL platform by introducing an interface tracking method, applying a heat source model, and setting appropriate boundary conditions. The effects of laser power, scanning speed, and processing time on stripping quality were analyzed using a single-factor method. Results show that increasing laser power significantly enhances stripping efficiency but also causes wider kerfs, larger heat-affected zones, and greater thermal expansion displacement. Higher scanning speeds effectively reduce kerf width but may compromise efficiency, while moderately extending processing time promotes cutting depth within a certain range. By optimizing parameter combinations, stripping efficiency can be improved without sacrificing quality. A three-factor, three-level orthogonal experiment was conducted, and range analysis validated the simulation results. The optimal parameter set was determined as a laser power of 0.9 W, scanning speed of 3 r/s, and processing time of 8 s. These findings provide a reliable theoretical and practical reference for high-quality laser stripping of PTFE insulation layers in large-diameter aviation cables.

82. Effects of pretreated approaches on microstructure and mechanical properties of laser oscillating welded joints in Q235B carbon steel 

Wei Zhang 1, Guoli Zhu 1, Chunming Wang 2, Hao Chen 3, Zehui Liu 2, Zhongshun Zhao 2 , Fei Yan 3,*

1 School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China 

2 School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China 

3 School of Automobile Engineering, Wuhan University of Technology, Wuhan 430070, China 

The formation of high-temperature oxide scales presents a persistent challenge during surface cleaning operations for Q235B carbon steel, primarily due to their strong adhesion and chemical stability at elevated temperatures. The current cleaning methods are difficult to remove thoroughly them, which can directly weaken the mechanical properties of the joints and limit its application in the industrial field. In this paper, we describe oscillating laser welding of Q235B carbon steel plates treated by multiple cleaning methods. The surface morphology, weld formation, microstructure and mechanical property of welded joints were carefully investigated using laser scanning confocal microscope, scanning electron microscope, electron back-scattered diffraction and other methodologies. The mechanical properties of the joints subjected to varying cleaning methods were evaluated. The failure mechanisms of the joints were also deeply explored. The results demonstrated that integrated laser cleaning is the most ideal solution for removing oxide scale among multiple cleaning methods. It can not only remove completely the oxide scale, but also decrease the roughness (SZ) on the material surface to a certain extent. The thorough remove of the oxide scale can enhance the stability of the keyhole and prevent the occurrence of defects such as undercuts and porosities during the welding process. Compared with mechanical grinding, integrated laser cleaning assisted laser welding can further refine the grain size and reduce the average grain orientation degree in the weld zone, which can effectively enhance the mechanical properties of the joints. The tensile strength and elongation of the joints subjected to mechanical grinding decreased by 9.99% and 23.93%, respectively, compared to those treated with integrated laser cleaning. The reasons for the weakening of the joints were mainly the formation of porosities and the stress concentration caused by residual oxide scale on the surface of the material. In addition, a model was schematically proposed including crack nucleation, crack propagation and crack fracture to elucidate the failure mechanism of the joints. 

81. Drop-like dross formation patterns and modes in laser cutting of stainless steel foils 

The geometrical process conditions of thin foils in laser cutting result in higher local surface tension forces, increasing the susceptibility to dross attachment. Drop-like dross formation patterns and modes in laser cutting of 100 µm thin stainless steel foils were investigated using high-speed imaging and run length analysis. Laser power and cutting speed significantly influenced dross formation. Three distinct dross patterns were identified: an alternating side directional pattern, single-sided formation, and irregular formations on both sides. These patterns, observed via bottom-view high-speed imaging, correspond to the three melt flow modes A, S, and I respectively, each associated with different line energy regimes. Mode S tends to occur at low line energy with about 4 ms duration until solidification per drop period, while Mode A is more likely at high line energy with about 20 ms solidification. A run length was introduced, where analysis revealed up to 36 consecutive dross deposits within the single sided formation pattern. The preferred movement of the melt, either to the one or to the other cut edge, is based on details of the complex fluid mechanics, which could partially be explained aided by high-speed imaging. Occasional drops merging events were observed during single-sided formation when molten dross remained in contact with a newly formed drop before solidification. Dross diameter and kerf width were also measured as key quality criteria for controlled laser cutting. These findings offer new insights into how process parameters govern dross behavior in thin-sheet laser cutting. 

80. Functional Grid Patterning on Silicon Substrates via Femtosecond Laser Processing for Physically Enhanced Raman Spectroscopy of Polystyrene Particles 

SangSeon Lee 1 and JaeCheol Park2,,# 

1 한국생산기술연구원 에너지나노그룹 (Energy & Nano Technology Group, Korea Institute of Industrial Technology) 

2 한국생산기술연구원 목적기반모빌리티그룹 (Purpose Built Mobility Group, Korea Institute of Industrial Technology) 

The practical application of Raman spectroscopy is often limited by its inherently low signal sensitivity. While Surface Enhanced Raman Scattering (SERS) offers powerful signal amplification, it suffers from high costs, complex fabrication, and poor reproducibility. This study presents a straightforward, SERS-free platform that enhances Raman signals through the physical concentration of analytes. We utilized a femtosecond pulse laser to fabricate functional micro-grid patterns on a silicon (Si) substrate. The laser process induces localized ablation and simultaneous oxidation, creating three dimensional, hydrophilic microstructures of non-stoichiometric silicon oxide (SiO2-x). These grid structures effectively confine aqueous sample droplets via a pinning effect, acting as a microwell array to physically trap and concentrate suspended polystyrene (PS) particles. Without requiring sample dehydration, this physical concentration mechanism achieved a significant signal enhancement, with a maximum factor of 5.2 for PS particles. This work demonstrates a simple, cost-effective, and highly reproducible alternative to conventional SERS for analyzing low-concentration liquid samples, showing strong potential for integration into microfluidic systems. 

79. Numerical simulation of ablation and heat affected zone width of glass fiber reinforced polymer in laser cutting 

Chao Liua,b,c,*, Xiaoran Rena, Juanjuan Zhenga,d *, Shaofu Huanga,c, Gang Shena 

a School of Mechanical and Electrical Engineering, Anhui University of Science and Technology, Huainan, 232000, China 

b State Key Laboratory of Mechanical Transmission for Advanced Equipment, Chongqing University, Chongqing, 400030, China 

c Institute of Environment-friendly Materials and Occupational Health, Anhui University of Science and Technology, Wuhu, 241003, China 

d College of Mathematics and Statistics, Chongqing University, Chongqing, 400030, China 

Glass fiber reinforced polymer (GFRP) is employed in the upper shell of new energy vehicle batteries due to its excellent corrosion resistance and mechanical properties. The transfer of heat during laser processing causes the uncut epoxy to melt and the exposed glass fibers to form (heat affected zone) HAZ, which generates an adverse influence on the quality of the machining. In this paper, the width of HAZ and ablation of laser cutting of GFRP have been studied using numerical simulation techniques. Numerical simulation of thermal distribution was performed through FEM analysis to delineate the HAZ perimeter. A conical Gaussian heat source model has been developed and a transient thermal analysis has been executed using ANSYS software. The innovative simulation of the laser cutting process, which combines the birth-death cell and restart technique, enhances the realism of the model. A high-speed camera is employed to observe and verify the effect of cutting parameters on ablation, while an optical microscope is utilised to measure the HAZ. A comparison of experiment and simulation results on the width of HAZ indicates that the error range for the width of the HAZ is between 3.52% and 8.33%. This provides an intuitive understanding of the influence of the spot size on the cutting results during the ablation process through the width of the entrance slit. 

78. Study on material removal mechanisms and parameter influence for remote laser cutting of concrete without assist gas 

Yi Jiana,Xingwang Baia,*, Penglei Jiea, Lingfeng Luoa, Min Maoa, Changjun Qiua,Zebin Zhub, Yuguo Kangb. 

a School of Mechanical Engineering, University of South China, Hengyang, Hunan, 421001, PR China 

b Dadi Special Exploration Team of National Mine Emergency Rescue, Bei'jing 100040, China 

Remote laser cutting as a non-contact material removal method, makes it possible to be applied in long-distance rescue and demolition operations. The material removal rate in long-distance laser cutting of concrete is relatively low due to the absence of assist gases. Since there is no condition for applying assist gas in most cases, improving material removal rate mainly relies on adjusting process parameters and cutting pattern. In this study, the material removal mechanism and the influence of parameters in remote laser cutting of concrete without assist gas were investigated. Through designed experiments, the effects of laser power (laser power 2-6 kW) and focal position (±2 m) on the material removal rates and kerf morphology were analyzed. A reciprocating cutting (4 passes at 8 mm/s) was proposed, achieving a 11.3% increase in material removal rates compared to single-pass cutting. The results show that main methods of material removal are splattering and slag dripping. Material removal rates can be enhanced by increasing laser power, positive defocusing (+2 m) and reciprocating cutting. This study provides a reference for future research on remote laser cutting concrete materials. 

77. Laser cutting; Experimental measurement of fluctuations in cut front temperature and morphology

Michael Sawannia1, John Powell1, Madlen Borkmann2, Christian Hagenlocher1, Thomas Graf1 

1Institut für Strahlwerkzeuge (IFSW), Universität Stuttgart, Stuttgart, Germany

2Fraunhofer-Institut für Werkstoff- und Strahltechnik – IWS, Dresden, Germany

Simulations of laser cutting need experimental measurements of the cutting front geometry and its temperature for validation purposes. A combined polarization goniometer and quotient pyrometer was used to measure these values for a cut in 10 mm stainless steel using a framerate of 75 kHz and a spatial resolution of 36 µm. For the first time, synchronized geometric and temperature measurements are given for a laser cutting front. These measurements show that, for 1 µm wavelength laser cutting, one of the main mechanisms of thermal and material flow involves the movement of hot ‘humps’ of liquid down the cutting front. These mobile humps experience an enhanced absorption of laser radiation on their upper surface and a reduced absorbed power density on their lower part and may even cast a shadow on the cut front immediately below them. In this work these phenomena resulted in local temperature fluctuations of 800 K, including temperature drops to 200K below the melting temperature for durations of up to approximately 200 µs.     

76. Laser based processing of difficult to cut ADI material used in Mobility industry 

V Sharun 1 and B Anand Ronald 2 

1 Department of Mechanical Engineering, Panimalar Engineering College, Poonamallee, Tamil Nadu, 600123, India, 

2 Department of Mechanical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam, Tamil Nadu, 603110, India 

In modern industry, advanced engineering materials are critical in the development of innovative goods. Austempered ductile iron (ADI) has emerged and been utilized in that series in recent years. A significant factor that makes this material worth considering is the unpredictable machining characteristics due to high hardness levels. This study aims to achieve a greater rate of material removal (MRR) with a reduced surface roughness (Ra) and a minimum kerf taper angle (KTa) utilizing a Fiber laser machining method, optimized through CCD, an efficient and flexible RSM design. In this, power (P), frequency (F), Cutting speed (Cs), and gas pressure (GP) are selected as input process parameters. ANOVA, a statistical method used to analyze variance among group means to identify significant differences, is applied to determine which of the laser parameters has a major impact on various output responses. As the power (P) increases to 4500 W, the value of Ra and KTa decrease by 45.37% and 66.47% respectively, while the MRR increases by 66.47%. A surface morphological investigation employing SEM analysis along with 3D roughness analysis reveals that adjusting the working pressure of the aided gas which predominantly assists in blowing away the molten material, along with other significant parameters has changed the surface quality of the machined ADI samples 

75. Experimental study on clamping pressure distribution in PEM fuel cells

Xinting Wang a 1, Ying Song b 2, Bi Zhang c 

a Connecticut Global Fuel Cell Center, University of Connecticut, 44 Weaver Road Unit 5233, Storrs, CT 06269-5233, United States

b Environmental Research Institute, University of Connecticut, 270 Middle Turnpike Unit 5210, Storrs, CT 06269-5210, United States

c Connecticut Global Fuel Cell Center, University of Connecticut, 191 Auditorium Road, Unit-3139, Storrs, CT 06269-3139, United States

To study the effect of internal pressure distribution on the performance of a PEM fuel cell, a pressurized endplate was designed and fabricated. The endplate had a built-in hydraulically pressurized pocket with a thin wall facing the fuel cell assembly. Pressure sensitive films were used to measure the pressure distribution for both conventional and newly designed end plates. Fuel cell performance tests were conducted under selected conditions. It was found that the pressure distribution for the newly designed endplates was more uniform than for the conventional end plates, and an improved fuel cell performance was obtained with the newly designed end plates as well. 

74. 15-Fold increase in solar thermoelectric generator performance through femtosecond-laser spectral engineering and thermal management

Tianshu Xu 1, RanWei 1, Subhash C. Singh Abstract 1,✉ and Chunlei Guo 1,✉  

1 The Institute of Optics, University of Rochester, Rochester, NY 14627, USA 

Solar thermoelectric generators (STEGs) have recently gained increasing attention. However, their widespread adoption has been limited due to the lack of high-efficiency thermoelectric materials and compact heat sinks for effective heat dissipation. To address these issues, we develop a spectral engineering and thermal management strategy that significantly increases STEG power generation by 15 times with only a 25% increase in weight. At the hot side, we transform a regular tungsten (W) to a selective solar absorber (W-SSA) through a femtosecond (fs)-laser processing technique, which enhances the solar absorption while minimizing the IR emissivity, obtaining >80% absorption efficiency at elevated temperatures. We also design a greenhouse chamber for W-SSA and achieved >40% reduction in convective heat loss. At the cold side, we apply the fs laser processing to transform a regular aluminum (Al) to a super-high-capacity micro-structured heat dissipator (μ-dissipator), which improves the cold-side heat dissipation through both radiation and convection, achieving twice the cooling performance of a regular Al heat dissipator. These spectral engineering and thermal management increase the temperature difference across the STEG, resulting in a substantial increase in output power. The high-efficiency STEG can find a wide range of applications, such as wireless sensor networks, wearable electronics, and medical sensors. 

73. Multipronged heat-exchanger based on femtosecond laser-nano/ microstructured Aluminum for thermoelectric heat scavengers 

Sohail A. Jalil a,b, Mohamed ElKabbash a,*,*, Zihao li a, Jihua Zhang a, Subhash Singh a, Zhibing Zhan a, Chunlei Guo a,* 

a The Institute of Optics, University of Rochester, Rochester, NY, 14627, USA 

b Changchun Institute of Optics, Fine Mechanics, and Physics, Chinese Academy of Sciences, Changchun, Jilin, 130033, China 

Femtosecond (fs) laser processing can significantly alter the optical, thermal, mechanical, and electrical prop erties of materials. Here, we show that fs-laser processing transforms aluminum (Al) to a highly efficient and multipronged heat exchanger. By optimizing the formed surface nano- and microstructures, we increase the Al emissivity and surface area by 700% and 300%, respectively. Accordingly, we show that fs-laser treated Al (fs-Al) increases the radiative and convective cooling power of fs-Al by 2100% and 300%, respectively, at 200 0C. As a direct application, we use fs-Al as a heat sink for a thermoelectric generator (TEG) and demonstrate a 280% increase in the TEG output power compared to a TEG with an untreated Al heat exchanger at 200 0C. The multipronged enhancement in fs-Al heat exchange properties lead to an increase in the TEG output power over a wide temperature (T) range (T>50 0C). Conversely, a simple radiative cooling heat exchanger increases the TEG output power within a limited temperature range (T>150 0C). We investigate the laser processing parameters necessary to maximize the spectral emissivity and surface area of fs-Al. Fs-Al promises to be a widely used and compact heat exchanger for passive cooling of computers and data centers as well as to increase the efficiency of TEGs incorporated in sensors and handheld electronics. 

72. Fully direct written organic micro-thermoelectric generators embedded in a plastic foil 

M. Massetti a,b, S. Bonfadini a,b, D. Nava a,b, M. Butti a, L. Criante a, G. Lanzani a,b, L. Qiu d, J. C. Hummelen c,d, J. Liu c, L.J.A. Koster c, M. Caironi c,* 

a Center for Nano Science and Technology@Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milan, Italy 

b Physics Department, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133, Milan, Italy 

c Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands 

d Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands 

Organic materials have attracted great interest for thermoelectric applications due to their tuneable electronic properties, solution processability and earth-abundance, potentially enabling high-throughput realization of low- cost devices for low-power energy harvesting applications. So far, organic thermoelectricity has primarily focused on materials development, with less attention given to integrated generators. Yet, future applications will require the combination of efficient generators architectures and scalable manufacturing techniques to leverage the advantages of such promising materials. Here we report the realization of a monolithic organic micro-thermoelectric generator (μ-OTEG), using only direct writing methods, embedding the thermoelectric legs within a plastic substrate through a combination of direct laser writing and inkjet printing techniques. Employing PEDOT:PSS for the p-type legs and a doped fullerene derivative for the n-type ones, we demonstrate a μ-OTEG with power density of 30.5 nW/cm2 under small thermal gradients, proving the concrete possibility of achieving power requirements of low-power, distributed sensing applications. 

71. Recent advances in fuel cell reaction electrocatalysis based on porous noble metal nanocatalysts 

Wenjing Cheng a,b Limei Sun *,b, Xiaoyan He *,a and Lin Tian *,a,b

a University and College Key Lab of Natural Product Chemistry and Application in Xinjiang, School of Chemistry and Environmental Science, Yili Normal University, Yining 835000, China. E-mail: xzittl@xzit.edu.cn, HeXiaoYan@ylnu.edu.cn, sunlimei2000@163.com 

b School of Materials and Chemical Engineering, Xuzhou University of Technology, Xuzhou 221018, PR China 

As the center of fuel cells, electrocatalysts play a crucial role in determining the conversion efficiency from chemical energy to electrical energy. Therefore, the development of advanced electrocatalysts with both high activity and stability is significant but challenging. Active site, mass transport, and charge transfer are three central factors influencing the catalytic performance of electrocatalysts. Endowed with rich available surface active sites, facilitated electron transfer and mass diffusion channels, and highly active components, porous noble metal nanomaterials are widely considered as promising electrocatalysts toward fuel cell-related reactions. The past decade has witnessed great achievements in the design and fabrication of advanced porous noble metal nanocatalysts in the field of electrocatalytic fuel oxidation reaction (FOR) and oxygen reduction reaction (ORR). Herein, the recent research advances regarding porous noble metal nanocatalysts for fuel cell-related reactions are reviewed. In the discussions, the inherent structural features of porous noble metal nanostructures for electrocatalytic reactions, advanced synthetic strategies for the fabrication of porous noble metal nanostructures, and the structure–performance relationships are also provided.

70. Metallic material selection and prospective surface treatments for proton exchange membrane fuel cell bipolar plates—a review 

Tereza Bohackova, Jakub Ludvik *, Milan Kouril * 

Department of Metals and Corrosion Engineering, University of Chemistry and Technology Prague, Technická 5 Prague 6, 166 28 Prague, Czech Republic

*Author to whom correspondence should be addressed.

The aim of this review is to summarize the possibilities of replacing graphite bipolar plates in fuel-cells. The review is mostly focused on metallic bipolar plates, which benefit from many properties required for fuel cells, viz. good mechanical properties, thermal and electrical conductivity, availability, and others. The main disadvantage of metals is that their corrosion resistance in the fuel-cell environment originates from the formation of a passive layer, which significantly increases interfacial contact resistance. Suitable coating systems prepared by a proper deposition method are eventually able to compensate for this disadvantage and make the replacement of graphite bipolar plates possible. This review compares coatings, materials, and deposition methods based on electrochemical measurements and contact resistance properties with respect to achieving appropriate parameters established by the DOE as objectives for 2020. An extraordinary number of studies have been performed, but only a minority of them provided promising results. One of these is the nanocrystalline β-Nb2N coating on AISI 430, prepared by the disproportionation reaction of Nb(IV) in molten salt, which satisfied the DOE 2020 objectives in terms of corrosion resistance and interfacial contact resistance. From other studies, TiN, CrN, NbC, TiC, or amorphous carbon-based coatings seem to be promising. This paper is novel in extracting important aspects for future studies and methods for testing the properties of metallic materials and factors affecting monitoring characteristics and parameters. 

69. Design and manufacturing of end plates of a 5 kW PEM fuel cell 

S. Asghari*, M.H. Shahsamandi, M.R. Ashraf Khorasani 

* Isfahan Engineering Research Center, 7th Kilometer of Imam Khomeini Ave., Po. Box: 81395-619, Isfahan, Iran 

End plate is one of the main components of the proton exchange membrane (PEM) fuel cells. The major role of the end plate is providing uniform pressure distribution between various components of the fuel cell (bipolar plates, etc.) and consequently reducing contact resistance between them. In this study a procedure for design of end plate has been developed. At first a suitable material was selected using various criteria. Then a finite element (FE) analysis was accomplished to analyze end plate deflections and get its optimized thickness. After fabricating the end plates, a single cell was assembled and electrochemical impedance spectroscopy (EIS) tests were carried out to ensure their good operation. A 5 kW fuel cell assembled with these end plates was tested at different operating conditions. The test results show an appropriate assembly pressure distribution inside the stack which indicates good performance of the designed end plates. 

68. Optics for concentrating photovoltaics: Trends, limits and opportunities for materials and design 

Katie Shanks * , S. Senthilarasu, Tapas K. Mallick 

* Environment and Sustainability Institute, University of Exeter Penryn Campus, Penryn TR10 9FE, UK 

Concentrating photovoltaic (CPV) systems are a key step in expanding the use of solar energy. Solar cells can operate at increased efficiencies under higher solar concentration and replacing solar cells with optical devices to capture light is an effective method of decreasing the cost of a system without compromising the amount of solar energy absorbed. However, CPV systems are still in a stage of development where new designs, methods and materials are still being created in order to reach a low levelled cost of energy comparable to standard silicon based PV systems. This article outlines the different types of concentration photovoltaic systems, their various design advantages and limitations, and noticeable trends. This will include comparisons on materials used, optical efficiency and optical tolerance (acceptance angle). As well as reviewing the recent development in the most commonly used and most established designs such as the Fresnel lens and parabolic trough/dish, novel optics and materials are also suggested. The aim of this review is to provide the reader with an understanding of the many types of solar concentrators and their reported advantages and disadvantages. This review should aid the development of solar concentrator optics by highlighting the successful trends and emphasising the importance of novel designs and materials in need of further research. There is a vast opportunity for solar concentrator designs to expand into other scientific fields and take advantage of these developed resources. Solar concentrator technologies have many layers and factors to be considered when designing. This review attempts to simplify and categorise these layers and stresses the significance of comparing as many of the applicable factors as possible when choosing the right design for an application. 

From this review, it has been ascertained that higher concentration levels are being achieved and will likely continue to increase as high performance high concentration designs are developed. Fresnel lenses have been identified as having a greater optical tolerance than reflective parabolic concentrators but more complex homogenisers are being developed for both system types which improve multiple performance factors. Trends towards higher performance solar concentrator designs include the use of micro-patterned structures and attention to detailed design such as tailoring secondary optics to primary optics and vice-versa. There is still a vast potential for what materials and surface structures could be utilised for solar concentrator designs especially if inspiration is taken from biological structures already proven to manipulate light in nature. 

67. Femtosecond Laser Textured Surfaces for Radiative Cooling: Black Metals 

Nan Zheng 1,†, Riˇcardas Buividas 1,2,* ,†, Hsin-Hui Huang 1,*, Dominyka Stonyte˙ 3 , Suresh Palanisamy 4 , De Ming Zhu 1, Tomas Katkus 1, Maciej Kretkowski 5 , Yoshiaki Nishijima 6,7,8, Lina Grineviciute 9 , Paul R. Stoddart 10 and Saulius Juodkazis 1,3,11 

1 Optical Sciences Centre, ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn, VIC 3122, Australia; nzheng@swin.edu.au (N.Z.); dzhu@swin.edu.au (D.M.Z.); sjuodkazis@swin.edu.au (S.J.) 

2 Quoba Systems Pty. Ltd., 26-28 Roberna St., Moorabbin, VIC 3189, Australia 

3 Laser Research Center, Physics Faculty, Vilnius University, Sauletekio Ave. 10, 10223 Vilnius, Lithuania; ˙ dominyka.stonyte@ff.vu.lt 

4 Department of Mechanical Engineering and Product Design Engineering, Swinburne University of Technology, Hawthorn, VIC 3122, Australia; spalanisamy@swin.edu.au 

5 Research Institute of Green Science and Technology, Shizuoka University, Hamamatsu Campus, Hamamatsu 432-8011, Japan; kretkowski.maciej@shizuoka.ac.jp 

6 Department of Electrical and Computer Engineering, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; nishijima@ynu.ac.jp 

7 Institute of Advanced Sciences, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan 

8 Institute for Multidisciplinary Sciences, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan 

9 Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300 Vilnius, Lithuania 

10 Department of Engineering Technologies, Swinburne University of Technology, Hawthorn, VIC 3122, Australia; pstoddart@swin.edu.au 

11 WRH Program International Research Frontiers Initiative (IRFI), Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan 

* Correspondence: rbuividas@swin.edu.au (R.B.); hsinhuihuang@swin.edu.au (H.-H.H.) 

† These authors contributed equally to this work 

There is a growing need for novel methods to modify the surfaces of a wide range of materials over large areas. Here, we demonstrate the creation of low-reflectance (R < 2%) surfaces in the near-to-mid infrared (IR) spectral window of 2–20 µm by ablating W, Al, and Cu with high average intensity 20–120 TW/cm2 , 200 fs laser pulses at 1030 nm wavelength. The chemical modifications of the surfaces by laser ablation under ambient room conditions were analyzed using X-ray photoelectron spectroscopy (XPS). The results show a consistent decrease in the metallic component, accompanied by an increase in metal oxides. Energy dispersive spectroscopy (EDS) showed a similar increase in oxygen content over a micrometer depth scale. The reduced refractive index of the metal oxides compared to the corresponding metals contributes to the reduction in IR reflectance, combined with the formation of 3D hierarchically textured surface structures. These IR-black metals exhibit great potential for radiative cooling at elevated temperatures relevant to industrial and space applications. 

66. Weld formation, microstructure and mechanical properties of laser oscillation welding of hot-dip galvanized steel sheets in a zero-gap lap joint configuration 

Fei Yan 1 , Yang Chen 1 , Panpan Lin 2 , Zeqi Hu 1 , Songyang Ma 1 , Zhongmei Gao 3, *, Junqiang Wang 4 , Hongsheng Chen 5 

1 School of Automobile Engineering, Wuhan University of Technology, Wuhan 430070, China 

2 State Key Laboratory of Precision Welding & Joining of Materials and Structures, Harbin Institute of Technology, Harbin 150001, China 

3 Hubei Digital Manufacturing Key Laboratory, School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China 

4 School of Physics and Electronic Information, Luoyang Normal University, Luoyang 471934, China 

5 School of Computer Science and Technology, Hubei University of Science and Technology, Xianning 437100, China 

In this paper, we describe a method using an oscillating laser beam adapted to supply a stable pathway inside the molten pool to allow the highly-pressurized zinc vapor to escape. The weld beads, microstructure and mechanical properties of the lap joints were carefully investigated, and the distribution characteristics of zinc element in the laser-welded joints were deeply explored using energy dispersive X-ray analysis. A high-speed video camera was applied to clearly observe the dynamic behavior of the laser-produced plasma plume and the keyhole, thereby revealing the escape mechanism of zinc vapor under different welding process conditions. Experimental results show that a lap joint with a desired forming quality was successfully achieved under the optimized welding process parameters. Laser oscillation welding method can not only accelerate the venting of the highly-pressurized zinc vapor from the molten pool and the keyhole, but also stabilize the laser-produced plasma during the welding process. The stirring effect of the oscillating laser beam on the welding pool also promotes the refinement of grains, the uniformity of the precipitated phases, and the inhibition of component segregation, which greatly improves the mechanical properties of the joints. The suppression of welding defects such as cavities and porosities in joints is mainly attributive to the stable escape pathway for zinc vapor and improved keyhole stability during oscillating laser beam welding. This study can provide an important theoretical guidance and technical support for high-quality and highefficiency manufacturing of automotive parts. 

65. Inverse Design of Photonic Surfaces via High throughput Femtosecond Laser Processing and Tandem Neural Networks

Minok Park, Luka Grbˇci´c, Parham Motameni, Spencer Song, Alok Singh, Dante Malagrino, Mahmoud Elzouka, Puya H. Vahabi, Alberto Todeschini, Wibe Albert de Jong, Ravi Prasher,* Vassilia Zorba,* and Sean D. Lubner* 

M. Park, A. Singh, M. Elzouka, R. Prasher, V. Zorba, S. D. Lubner Energy Technologies Area Lawrence Berkeley National Laboratory Berkeley, CA 94720, USA E-mail: rsprasher@lbl.gov; vzorba@lbl.gov; slubner@bu.edu L. 

Grbˇci´c, W. A. de Jong Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory Berkeley, CA 94720, USA P. Motameni, S. Song, D. Malagrino, P. H. Vahabi School of Information University of California at Berkeley Berkeley, CA 94709, USA 

This work demonstrates a method to design photonic surfaces by combining femtosecond laser processing with the inverse design capabilities of tandem neural networks that directly link laser fabrication parameters to their resulting textured substrate optical properties. High throughput fabrication and characterization platforms are developed that generate a dataset comprising 35280 unique microtextured surfaces on stainless steel with corresponding measured spectral emissivities. The trained model utilizes the nonlinear one-to-many mapping between spectral emissivity and laser parameters. Consequently, it generates predominantly novel designs, which reproduce the full range of spectral emissivities (average root-mean-squared-error < 2.5%) using only a compact region of laser parameter space 25 times smaller than what is represented in the training data. Finally, the inverse design model is experimentally validated on a thermophotovoltaic emitter design application. By synergizing laser-matter interactions with neural network capabilities, the approach offers insights into accelerating the discovery of photonic surfaces, advancing energy harvesting technologies. 

64. Inverse design of photonic surfaces via multi fidelity ensemble framework and femtosecond laser processing

Luka Grbčić1,6, Minok Park 2,6, Mahmoud Elzouka2 , Ravi Prasher2,3, Juliane Müller4 , Costas P. Grigoropoulos2,3, Sean D. Lubner2,5 , Vassilia Zorba2,3 & Wibe Albert de Jong 1,* 

1 Applied Mathematics and Computational Research Division, Computing Science Area, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. 

2 Energy Storage and Distributed Resources Division, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. 

3 Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA, 94709, USA. 

4 Computational Science Center, National Renewable Energy Laboratory, Golden, Colorado, 80401, USA. 

5 Department of Mechanical Engineering, Division of Materials Science and Engineering, Boston University, Boston, MA, 02215, USA. 

6 These authors contributed equally: Luka Grbčić, Minok Park.

*e-mail: slubner@bu.edu; vzorba@lbl.gov; wadejong@lbl.gov 

We demonstrate a multi-fidelity (MF) machine learning ensemble framework for the inverse design of photonic surfaces, trained on a dataset of 11,759 samples that we fabricate using high throughput femtosecond laser processing. The MF ensemble combines an initial low fidelity model for generating design solutions, with a high fidelity model that refines these solutions through local optimization. The combined MF ensemble can generate multiple disparate sets of laser-processing parameters that can each produce the same target input spectral emissivity with high accuracy (root mean squared errors < 2%). SHapley Additive exPlanations analysis shows transparent model interpretability of the complex relationship between laser parameters and spectral emissivity. Finally, the MF ensemble is experimentally validated by fabricating and evaluating photonic surface designs that it generates for improved efficiency energy harvesting devices. Our approach provides a powerful tool for advancing the inverse design of photonic surfaces in energy harvesting applications. 

63. High-efficiency air-bridge thermophotovoltaic cells

Bosun Roy-Layinde,1  Jihun Lim,2  Claire Arneson,3  Stephen R. Forrest,2,3,4 and Andrej Lenert,1,5,* 

1 Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA 

2 Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA 

3 Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA 

4 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA 

5Lead contact 

*Correspondence: alenert@umich.edu 

Thermophotovoltaic (TPV) cells generate electricity by converting infrared radiation emitted by a hot thermal source. Air-bridge TPVs have demonstrated enhanced power conversion efficiencies by recuperating a large amount of power carried by below-bandgap (out-of-band) photons. Here, we demonstrate single-junction InGaAs(P) air-bridge TPVs that exhibit up to 44% efficiency under 1,435C blackbody illumination. The air-bridge design leads to near-unity reflectance (97%–99%) of out-of-band photons for ternary and quaternary TPVs whose band gaps range from 0.74 to 1.1 eV. These results suggest the applicability of the air-bridge cells to a range of semiconductor systems suitable for electricity generation from thermal sources found in both consumer and industrial applications, including thermal batteries. 

 62. Thermophotovoltaic efficiency of 40%

Alina LaPotin 1 , Kevin L. Schulte 2 , Myles A. Steiner 2 , Kyle Buznitsky 1 , Colin C. Kelsall 1 , Daniel J. Friedman 2 , Eric J. Tervo 2 , Ryan M. France 2 , Michelle R. Young 2 , Andrew Rohskopf 1 , Shomik Verma 1 , Evelyn N. Wang 1 & Asegun Henry 1 ✉ 

1 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA. 

2 National Renewable Energy Laboratory, Golden, CO, USA 

Thermophotovoltaics (TPVs) convert predominantly infrared wavelength light to electricity via the photovoltaic efect, and can enable approaches to energy storage1,2 and conversion3–9 that use higher temperature heat sources than the turbines that are ubiquitous in electricity production today. Since the frst demonstration of 29% efcient TPVs (Fig. 1a) using an integrated back surface refector and a tungsten emitter at 2,000 °C (ref. 10), TPV fabrication and performance have improved11,12. However, despite predictions that TPV efciencies can exceed 50% (refs. 11,13,14), the demonstrated efciencies are still only as high as 32%, albeit at much lower temperatures below 1,300 °C (refs. 13–15). Here we report the fabrication and measurement of TPV cells with efciencies of more than 40% and experimentally demonstrate the efciency of high-bandgap tandem TPV cells. The TPV cells are two-junction devices comprising III–V materials with bandgaps between 1.0 and 1.4 eV that are optimized for emitter temperatures of 1,900–2,400 °C. The cells exploit the concept of band-edge spectral fltering to obtain high efciency, using highly refective back surface refectors to reject unusable sub-bandgap radiation back to the emitter. A 1.4/1.2 eV device reached a maximum efciency of (41.1 ± 1)% operating at a power density of 2.39 W cm–2 and an emitter temperature of 2,400 °C. A 1.2/1.0 eV device reached a maximum efciency of (39.3 ± 1)% operating at a power density of 1.8 W cm–2 and an emitter temperature of 2,127 °C. These cells can be integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy. This creates a pathway for thermal energy grid storage to reach sufciently high efciency and sufciently low cost to enable decarbonization of the electricity grid. 

61. High emissivity, thermally robust emitters for high power density thermophotovoltaics 

Minok Park1,2,3,†, Shomik Verma 4,†, Alina LaPotin4 , Dustin P. Nizamian5 , Ravi Prasher1,2, Asegun Henry4,*, Sean D. Lubner1,6,*, Costas P. Grigoropoulos1,2,*, and Vassilia Zorba1,2,*  

1 Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA 2 

2 Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California, 94720, USA 

3 Department of Mechanical and Automotive Engineering, Kongju National University, Cheonan, 31080, Republic of Korea 

4 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA 

5 Antora Energy, Inc., Sunnyvale, California, 94089, USA 

6 Department of Mechanical Engineering, Division of Materials Science and Engineering, Boston University, Boston, Massachusetts, 02215, USA 

Thermal radiative energy transport is essential for high-temperature energy harvesting technologies, including thermophotovoltaics (TPVs) and grid-scale thermal energy storage. However, the inherently low emissivity of conventional high-temperature materials constrains radiative energy transfer, thereby limiting both system performance and technoeconomic viability. Here, we demonstrate ultrafast femtosecond lasermaterial interactions to transform diverse materials into near-blackbody surfaces with broadband spectral emissivity above 0.96. This enhancement arises from hierarchically engineered light-trapping microstructures enriched with nanoscale features, effectively decoupling surface optical properties from bulk thermomechanical properties. These laser-blackened surfaces (LaBS) exhibit exceptional thermal stability, retaining high emissivity for over 100 hours at temperatures exceeding 1000°C, even in oxidizing environments. When applied as TPV thermal emitters, Ta LaBS double electrical power output from 2.19 to 4.10 W cm-2 at 2200°C while sustaining TPV conversion efficiencies above 30%. This versatile, largely material-independent technique offers a scalable and economically viable pathway to enhance emissivity for advanced thermal energy applications. 

60. Study on material removal mechanisms and parameter influence for remote laser cutting of concrete without assisted gas

Yi Jiana, Xingwang Bai a,*, Penglei Jiea, Lingfeng Luoa, Min Maoa, Changjun Qiua, Zebin Zhub, Yuguo Kangb

a School of Mechanical Engineering, University of South China, Hengyang, Hunan, 421001, PR China   

b Dadi Special Exploration Team of National Mine Emergency Rescue, Bei'jing 100040, China 

Remote laser cutting as a non-contact material removal method, makes it possible to be applied in long-distance rescue and demolition operations. The material removal rate in long-distance laser cutting of concrete is relatively low due to the absence of assisted gas. To address this problem, the material removal mechanism and the influence of parameters in remote laser cutting of concrete without assisted gas were investigated in this study. Through designed experiments, the effects of laser power and focal position on the material removal rates and kerf morphology were analyzed. A reciprocating cutting was proposed to increase material removal rates. The results show that main methods of material removal are splattering and slag dripping. Material removal rates can be enhanced by increasing laser power, positive defocusing and reciprocating cutting. This study provides a reference for future research on remote laser cutting concrete materials.

59. Al and Cu effect on the microstructure and mechanical properties of HEA alloys based on the AlCoCuFeNi system 

Three variants of high-entropy alloys (HEA) from the AlCoCuFeNi group containing different amounts of Al and Cu were developed and produced via induction melting and casting into ceramic molds. The ingots were homogenized at 1000 °C for 10 h. Analyses indicated that variations in aluminum (Al) and copper (Cu) concentrations resulted in significant changes to the microstructure, hardness, strength, and impact strength of the material. In the equiatomic variant, differential scanning calorimetry revelaed a peak linked with phase transformation at around 820 °C, indicating that this alloy's microstructure consists of two phases. In contrast, when the concentrations of Al and Cu are reduced, a single-phase microstructure is observed. The equiatomic variant (used as a reference) is characterized by its hardness and brittleness, exhibiting slight ductility, with a tensile strength of 80 MPa, a hardness of 400 HV5, and an impact strength of 1.9 J/cm². However, with adjusted Al contents of 1/2 and Cu contents of 1/4, the alloy displays exceptional strength combined with good plasticity, achieving a tensile strength of up to 450 MPa with 60% elongation, and an impact strength of 215 J/cm². Fracture analysis conducted using scanning electron microscopy revealed excellent ductility in the samples. 

58. Enhancing laser weld quality of multilayer copper micro-foils and anode disk for batteries manufacturing: Role of preload-controlled thermal resistance in ultrathin interlayer gap 

Junzhuo Guo a,b, Haoyue Lia a,b,*, Liqun Lia,a,b,*, Hongbo Xiaa,b, Xiangbing Zengc,d, Dingkai Yuanee, Lina Zhaoee 

a State Key Laboratory of Precision Welding & Joining of Materials and Structures, Harbin Institute of Technology, Harbin, Heilongjiang, 150001, China 

b Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou, Henan, 450000, China 

c Anhui Deeiot Energy Technology Co., Ltd, Wuhu, Anhui 241002, China 

d Chery Automobile Co., Ltd, Wuhu Anhui 241006, China 

e Yunsa Power (Ningbo) CO., Ltd, Ningbo, 315177, China 

In cylindrical lithium-ion batteries, laser welding of stacked copper foil and anode assemblies is essential for forming high-current full-tab connections, where weld quality is critical to ensuring cell safety. However, ultrathin interlayer gaps between stacked copper foils and anode disks significantly affect heat conduction during welding, yet it has received limited attention. In this study, the effect of precisely modulating the preload on the laser weld quality of multilayer copper foil stacks and anode disks and underlying heat transfer in ultrathin interlayer gap was investigated. The weld quality was comprehensively evaluated by examining surface and cross sectional morphology. It was found that within the preload range of 20 N to 60 N, the weld surface defects increased with higher preload while too little preload led to false welding. Although the weld depth and width are enhanced with increasing preload, the weld cross-section exhibits lower volatility and fewer porosities at a preload of approximately 40 N. Theoretical analysis indicates that the ultrathin inter-foil gas gap operates in a slip-flow regime with substantial thermal resistance. The preload governed the thermal resistance of gaps, thereby directly altering thermal transfer efficiency during laser welding. Higher quality welds with greater depth and fewer defects were obtained with an optimum preload of about 40 N, whereas too small preload induced incomplete depth and excessive preloads destabilized the welding process. This research established preload optimization as an effective strategy for enhancing multi layer copper foil welding reliability, providing novel insights for optimizing fixturing conditions in battery manufacturing processes. 

57. Performance analysis and experimental study of titanium GDL in proton exchange membrane fuel cell 

Tiancai Ma a,b , Huijin Guo a,b,c , Ziheng Gu a,* , Weikang Lin d , Jinxuan Qi a , Chaofan Yu c , Jianghua Li a 

a Tongji Univ, Sch Automot Studies, 4800 Caoan Highway, Shanghai, 201804, China 

b Tongji Univ, Inst Carbon Neutral, Shanghai, 200092, China 

c AT&M Environmental Engineering Technology Co., Ltd, No. 76 Xueyuan South Road, Haidian District, Beijing, 100081, China 

d Shanghai Champspower Technology Co., Ltd., Shanghai, 201800, China 

The gas diffusion layer (GDL) plays an important role in proton exchange membrane fuel cells (PEMFC) to support the catalytic layer, collect the current, conduct the gas and discharge the reaction product water. Titanium (Ti) can be one of the choices of GDL materials due to its high strength, low density and excellent corrosion resistance. Therefore, this paper investigated Ti substrate material for GDL and comparatively analyzed the changes in the contact angle of the GDL before and after hydrophobic treatment, analyzed the changes in the performance of the cell after different treatment processes, and measured the effect of compression force on the contact resistance of the cell. The results show that, after the selection of Ti felt as the substrate and the carbon plating process, the contact angle of the substrate layer and the microporous layer increased significantly, and the hydrophobicity of the GDL surface improved after carbon plating. The contact resistance of the Ti felt substrate was significantly reduced after carbon plating and was even lower than that of the C–H-060 substrate. Considering the importance of the hydrophobicity of GDL, acetylene black microporous layer coating is also needed to increase the contact angle of the GDL interface and improve the hydrophobicity of GDL. The hydrophobic treatment of MPL using Ti felt as the substrate can significantly improve the output performance of the cell at high current density, avoid flooding inside the cell, and increase the current density operating range of the cell. 

56. Virtual surface morphology generation of Ti-6Al-4V directed energy deposition via conditional generative adversarial network

Taekyeong Kim a *, Jung Gi Kimb*, Sangeun Park b, Hyoung Seop Kim c, Namhun Kim a, Hyunjong Ha d, Seung-Kyum Choi e, Conrad Tucker f, Hyokyung Sung b,g * and Im Doo Jung a *

a Department of Mechanical Engineering, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea; 

b Department ofMaterials Engineering and Convergence Technology (Center for K-Metals), Gyeongsang National University, Jinju, Republic of Korea;

c Department of Materials Science and Engineering, Center for High-Entropy Alloys, Pohang University of Science and Technology, Pohang,Republic of Korea; 

d Korea Institute of Materials Science, Changwon, Republic of Korea; 

e The George W. Woodruf School of MechanicalEngineering, Georgia Institute of Technology, Atlanta, GA, USA; 

f Department of Mechanical Engineering, Carnegie Mellon University,Pittsburgh, PA, USA; 

g Department of Materials Science and Engineering, Kookmin University, Seoul, Republic of Korea

The core challenge in directed energy deposition is to obtain high surface quality through processoptimisation, which directly affects the mechanical properties of fabricated parts. However, for expensive materials like Ti-6Al-4V, the cost and time required to optimise process parameters can be excessive in inducing good surface quality. To mitigate these challenges, we propose a novel method with artificial intelligence to generate virtual surface morphology of Ti-6Al-4V parts by given process parameters. A high-resolution surface morphology image generation system has been developed by optimising conditional generative adversarial networks. The developed virtual surface matches experimental cases well, with a Fréchet inception distance score of 174, in the range of accurate matching. Microstructural analysis with parts fabricated with artificial intelligence guidance exhibited less textured microstructural behaviour on the surface which reduces the anisotropy in the columnar structure. This artificial intelligence guidance of virtual surface morphology can help to obtain high-quality parts cost-effectively.

55. A Deep-Learning-Based Surrogate Model for Thermal Signature Prediction in Laser Metal Deposition

Shenghan Guo a , Weihong Guo b, Linkan Bian c, and Y. B. Guo d,*

a School of Manufacturing Systems and Networks, Arizona State University. 

b Industrial and Systems Engineering Department, Mississippi State University.

c Industrial and Systems Engineering, Rutgers University. 

d Advanced Manufacturing at Rutgers University, New Brunswick. 

Laser metal deposition (LMD) is an additive manufacturing method for metal parts by using focused thermal energy to fuse materials as they are deposited. During LMD, transient thermal signatures such as the in-situ thermal images of melt pool, contain rich information about process performance. Early prediction of such transient thermal signatures provides opportunities for process monitoring and defect prevention. While physics-based models of LMD have been conventionally used for thermal signature prediction, they have limitations and are computationally expensive for real-time prediction. A scalable, efficient data-science-based model is therefore needed. This paper develops a deep-learning-based surrogate model, called LMDcGAN, to predict and emulate the transient thermal signatures in LMD. The model generates images for the thermal dynamics of melt pool conditionally on the deposition layer. It enables early prediction of future-layer thermal signatures for an in-process part based on its early-layer thermal signatures. To respect the physics in LMD, a physics-guided image selection (PGIS) mechanism is integrated with LMD-cGAN to calibrate the predictions against physical benchmarks of transient melt pool for the process. The effectiveness and efficiency of the proposed method are demonstrated in a case study on the LMD of Ti-4Al-6V thin-walled structures. benchmarking them against physical insights about the process. LMD-cGAN can be applied to predict thermal signatures in future layers based on early-layer thermal signatures of an in-process part (an implicit assumption here is that the in-process part to be predicted for is the same type). LMD-cGAN can also be applied to emulate thermal signatures in specific layers. To generate thermal signatures for generic, non-defect parts, the training data should be selected with caution – the part where the data were collected should have no obvious defects, so the thermal signatures generated by LMD-cGAN show the regular thermal dynamics. Compared with pure physical models, the proposed method incorporates process uncertainties captured from the early-layer data, hence “on-the-fly” emulation of the melt pool, while characterizing the inherent relationship between the LMD process and thermal signatures. 

54. PEARSON'S OR SPEARMAN'S CORRELATION COEFFICIENT - WHICH ONE TO USE? 

Rebekić, Andrijana; Lončarić, Zdenko; Petrović, Sonja; Marić, Sonja 

Poljoprivredni fakultet u Osijeku, Poljoprivredni institut Osijek Faculty of Agriculture in Osijek, Agricultural Institute Osijek  

Most commonly used correlation coefficients are Pearson's product moment correlation coefficient and Spearman's rank correlation coefficient. The aim of this paper is to compare a Pearson's and Spearman's coefficient of correlation on the same data set. The winter wheat grain cadmium (Cd) concentration was correlated to grain zinc (Zn) concentration, plant height, plant weight, number of spikelets per spike and 1000 kernel weight. Data were collected from the experiment carried out in semi controlled conditions, where genotypic specificity of winter wheat varieties was tested on the grain Cd and Zn accumulation on uncontaminated and Cd contaminated soil. Results showed that selection of most convenient correlation coefficient mostly depends on the type of variables, presence of outliers normality and linearity of relationship. 

53. Effect of laser power on microstructure and properties of laser assisted cold sprayed copper coatings on steel 

Zhengwei Qi a,b,1 , Yanmei Li c,1 , Xin Chu b,* , Yingchun Xie b,* , Yu Long a,* 

a Institute of Laser Intelligent Manufacturing and Precision Processing, State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, School of Mechanical Engineering, Guangxi University, Nanning, Guangxi 530004, China 

b Institute of New Materials, Guangdong Academy of Sciences, National Engineering Laboratory of Modern Materials Surface Engineering Technology, Guangdong Provincial Key Laboratory of Modern Surface Engineering Technology, Guangzhou 510651, China 

c Huiyang Aviation Propeller Co., Ltd., Baoding 412002, China 

Laser assisted cold spraying (LACS) is a promising technology for preparing high performance copper-steel composite materials for grounding electrode applications. Laser power is a critical LACS parameter, however, in literature there is a lack of studies on the influence of laser power on coatings. In this study, the effect of laser power on microstructure and properties of LACS copper coatings on steel is investigated. The results show that with the increase of laser power, the copper coating generally shows reduced porosity and microhardness, as well as increased bonding strength. However, the grains are first refined and then coarsened, while the electrical conductivity and corrosion resistance both increased and then decreased. This is because when the laser power exceeds 4 kW, the grain is coarsened and the amount of large angular grain boundaries (HAGBs) increases because excessive temperature increases the recrystallization driving force, ultimately leading to decrease in coating electrical conductivity and corrosion resistance. 4.0 kW, 5 MPa, 800 ◦C is considered as optimal LACS parameters for preparation of pure copper coatings on Q235 steel. The coating has a porosity of <0.04 %, grain size of 0.634 μm, microhardness of 99.4HV0.1, bonding strength exceeds 62 MPa, electrical conductivity of 99 % IACS, and corrosion current density of 6.092 × 10− 8 A/cm2 . In addition, mechanisms of LACS particle deposition and corrosion of copper coatings in simulated soil solution were discussed. With the increase of laser power, more heat absorbed by the powder and the substrate promotes thermal softening and plastic deformation, resulting in stronger mechanical bonding. The corrosion mechanism gradually changes from pitting corrosion to uniform corrosion due to the reduced porosity and tighter grain boundaries, and finally to intergranular corrosion due to grain coarsening and high HAGBs content. Overall, this study provides guidance and reference for the practical application of LACS. 

52. Effects of Laser Cutting on Microstructure, Hardness and Magnetic Properties of Fe-

based Amorphous Ribbons

Junlei Shi 1, Lansong Yang 1, Hao Zhou, Peixin Fu, Pingjun Tao, Yuanzheng Yang *

School of Materials and Energy, Guangdong University of Technology, Guangzhou

510006, China

Fe-based amorphous materials are indispensable in magnetic devices. With the rapid application of the wireless charger, amorphous motors, and amorphous transformers, developing open-type magnetic devices has become an urgent task. In this research, a sophisticated continuous-wave infrared (IR) laser cutting technique is employed to cut FeSiBCuNb amorphous ribbons into ring shapes at different laser powers, then the laminated magnetic cores are prepared. Here, a systematic study is conducted on the cross-section morphology, microhardness, microstructure and magnetic properties of FeSiBCuNb amorphous ribbons by laser cutting. Our results demonstrate that three zones occur from the cutting edge to the substrate, which we call them as the melted zone (MZ), the heat affected zone (HAZ) and the unaffected zone. Meanwhile, Only the α-Fe(Si) phase and the residual amorphous phase are generated in the crystallization zone as the reaction time between the laser and the FeSiBCuNb amorphous ribbon is short, and its average grain sizes decrease gradually from the cutting edge to the unaffected zone. Also, the formation of amorphous-nanocrystalline dual-phase after laser cutting is beneficial to obtaining high hardness, and it is about 1035 HV at 20 μm from straight cut-edge. In addition, the sample of applied laser power of 75W exhibits excellent combined properties, including narrow width of the MZ and HAZ, low power loss of 53.96 W/kg (200 mT, 100 kHz). This discovery provides the potential of Fe-based amorphous ribbon used IR laser cutting as a promising method, which stills suitable for high-frequency power devices.

51. Porous Material (Titanium Gas Diffusion Layer) in Proton Exchange Membrane Fuel Cell/Electrolyzer: Fabrication Methods &GeoDict: A Critical Review 

Javid Hussain 1,2,†, Dae-Kyeom Kim 2,†, Sangmin Park 1,2, Muhammad-Waqas Khalid 1,2, Sayed-Sajid Hussain 3, Bin Lee 4, Myungsuk Song 2,* and Taek-Soo Kim 1,2,* 

1 Industrial Technology, University of Science and Technology, Daejeon 34113, Republic of Korea; javidmohsin77@kitech.re.kr (J.H.); jhsm8920@kitech.re.kr (S.P.); waqas@kitech.re.kr (M.-W.K.) 

2 Korea Institute for Rare Metals, Korea Institute of Industrial Technology, Incheon 21999, Republic of Korea; kyeom@kitech.re.kr 

3 Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea; sayedsajidh506@gmail.com 

4 Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University, Yongin 17104, Republic of Korea; leebin@khu.ac.kr Correspondence: mssong@kitech.re.kr (M.S.); tskim@kitech.re.kr (T.-S.K.) 

† Theseauthors contributed equally to this work. 

Proton exchange membrane fuel cell (PEMFC) is a renewable energy source rapidly ap proaching commercial viability. The performance is significantly affected by the transfer of fluid, charges, and heat; gas diffusion layer (GDL) is primarily concerned with the consistent transfer of these components, which are heavily influenced by the material and design. High-efficiency GDL must have excellent thermal conductivity, electrical conductivity, permeability, corrosion resistance, and high mechanical characteristics. The first step in creating a high-performance GDL is selecting Citation: Hussain, J.; Kim, D.-K.; Park, S.; Khalid, M.-W.; Hussain, S.-S.; Lee, B.; Song, M.; Kim, T.-S. Porous Material (Titanium Gas Diffusion Layer) in Proton Exchange Membrane Fuel Cell/Electrolyzer: Fabrication Methods & GeoDict: A Critical Review. Materials 2023, 16, 4515. https://doi.org/10.3390/ ma16134515 Academic Editor: Fani Stergioudi Received: 10 May 2023 Revised: 15 June 2023 Accepted: 16 June 2023 Published: 21 June 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). the appropriate material. Therefore, titanium is a suitable substitute for steel or carbon due to its high strength-to-weight and superior corrosion resistance. The second crucial parameter is the fabrication method that governs all the properties. This review seeks to comprehend numerous fabrication methods such as tape casting, 3D printing, freeze casting, phase separation technique, and lithography, along with the porosity controller in each process such as partial sintering, input design, ice structure, pore agent, etching time, and mask width. Moreover, other GDL properties are being studied, including microstructure and morphology. In the future, GeoDict simulation is highly recommended for optimizing various GDL properties, as it is frequently used for other porous materials. The approach can save time and energy compared to intensive experimental work. 

50. Effect of laser remelting and ultrasonic irradiation on crack suppression and properties of Ni-WC laser cladding layer

Haifeng Zhang, HuaiChen Guo, Xiaoping Hu, JiYuan Tao, WenHan She, Changlong Zhao *

School of Mechanical and Vehicle Engineering, Changchun University, Changchun 130022, Jilin

Natural Science Foundation of Jilin Province (No. YDZJ202501ZYTS395) , Scientific Research  Education Department of Jilin Province (No. JJKH20251089CY) .

The objective of this study was to examine the impact of two assisted laser cladding processes, namely laser remelting and ultrasonic irradiation, on the properties and crack susceptibility of Ni60-WC laser cladding layers on C45E4 steel substrates. The experimental configuration entailed the implementation of facilitated metal matrix ceramic composite fused cladding layer preparation processes by laser remelting and laser cladding, employing a custom-designed ultrasonic irradiation device that was developed in-house. A range of analytical instruments, including an optical digital microscope, a scanning electron microscope, a Vickers microhardness tester, an X-ray diffractometer (XRD), a friction and wear tester, and a three-dimensional optical profilometer, were used to investigate the surface cracking, microstructure, hardness, abrasion resistance, and wear surface morphology of the fused cladding. The experimental findings demonstrated that ultrasonic waves significantly enhanced the crystal strengthening effect of the fused cladding, resulting in a 23.08% decrease in wear resistance. Furthermore, the combined laser remelting and ultrasonic-assisted process effectively prevented the formation of cracks in the laser-melted cladding layer and enhanced the hardness of the fused cladding substrate. Notably, despite the occurrence of partial melting of WC particles during the laser remelting process, the hardness of the cladding layer prepared by these assisted processes exhibited an enhancement of 17.54%, and the wear resistance was found to be comparable to that of the conventional cladding layer.

49. Effect of different carbon fillers on the properties of graphite composite bipolar plate 

R.B. Mathur ∗, S.R. Dhakate, D.K. Gupta, T.L. Dhami, R.K. Aggarwal 

Carbon Technology Unit, Engineering Materials Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012, India 

A bipolar plate is one of the key components of a proton exchange membrane fuel cell. Development of a suitable material for use as bipolar plate is scientifically and technically important due to the need to maintain high-electrical conductivity, better mechanical properties and low-manufacturing cost. A replacement of the conventional graphite bipolar plate is reported which is twice as strong as the conventional monolithic graphite plate. These plates have been produced by compression molding technique using natural graphite, synthetic graphite, carbon fiber and carbon black as reinforcing constituents and phenolic resin as a binder matrix. A judicious combination and their respective proportions, could produce a composite plate with bulk density 1.8–1.90 g/cm3, electrical resistivity between 0.002 and 0.007 cm, shore hardness ∼65, flexural strength ∼45 MPa and flexural modulus ∼12 GPa. The characteristics and the performance of the composite plate developed by us are compared with the commercially available bipolar plates. A power density of ∼500mW/cm2 was achieved at 1400mA/cm2 current density when the above composite plate was used as a bipolar plate in a unit fuel cell 

48. A review on the mechanical and electrical properties of graphite and modified graphite reinforced polymer composites 

Rajatendu Sengupta a, Mithun Bhattacharya a, S. Bandyopadhyay b, Anil K. Bhowmick a,∗ 

a Rubber Technology Centre, Indian Institute of Technology Kharagpur, 721302, India 

b School of Materials Science and Engineering, UNSW, Sydney, NSW 2052, Australia 

Carbon materials particularly in the form of sparkling diamonds have held mankind spellbound for centuries, and in its other forms, like coal and coke continue to serve mankind as a fuel material, like carbon black, carbon fibers, carbon nanofibers and carbon nanotubes meet requirements of reinforcing filler in several applications. All these various forms of carbon are possible because of the element’s unique hybridization ability. Graphene (a single two-dimensional layer of carbon atoms bonded together in the hexagonal graphite lattice), 

47. Graphite and carbon powders for electrochemical applications 

Mathis Wissler ∗ 

Superior Graphite Europe, 13000, 850 13 Sundsvall, Sweden 

Graphite and carbon powders occur in many different forms and emanate from many different sources. A systematic classification is given based on the degree of crystallinity, from low-structured coke and coal products to macro-crystalline graphite and nanocarbons. In the family of ‘carbon black’ the highly conductive products acetylene black and PUREBLACK® Carbon are discussed. Graphite can be either natural or synthetic. Depending on the formation of the natural graphite, the morphology can vary from micro-crystalline to macro-crystalline. Expanded graphite is described as a chemically treated, extremely thin, flake graphite. Synthetic graphite products are classified as either primary material or secondary. The latter is defined as a byproduct of graphite component- and electrode-manufacturing.

The characterization of graphite and carbons is also discussed. A very useful characterization tool – the ‘PSTP’ model (purity, structure, texture, particle size) – has been formalized. These four basic parameters determine most of the application parameters such as conductivity, lubricity and elasticity. The influence of these four basic parameters on the application properties is examined.

46. A review on warpage measurement metrologies for advanced electronic packaging

Guoli Sun a, b, Shuye Zhang a, b, * 

a State Key Laboratory of Precision Welding & Joining of Materials and Structures, Harbin Institute of Technology, Harbin 150001, China

b Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou 450000, China

In the post-Moore era, advanced electronic packaging technology emerges as a prominent direction for the future evolution of semiconductor industry. Nevertheless, warpage remains a prevalent issue in this domain, capable of significantly disrupting the precision and automation operation of subsequent processes, thereby precipitating various operational challenges. Consequently, the comprehensive examination of warpage assumes paramount important in enhancing packaging assembly yield and ensuring device reliability. The rigorous measurement of warpage through experimental methodologies assumes a pivotal role in investigating warpage-related concerns. Thus, this review has succinctly encapsulated established warpage measurement metrologies that are extensively employed in advanced semiconductor packages, shedding light on the measurement capabilities, advantages and limitations inherent of each technique. Typically, warpage measurement techniques can be broadly categorized into two main classes: contact and noncontact methods. Noteworthy examples of the former category encompass moiré interferometry, digital image correlation (DIC), laser scanning measurement and optical interferometry, while the later involves stylus-based technique and the use of ruler for warpage data acquisition. Furthermore, this study encompasses a comprehensive examination of all the aforementioned measurement methods and offers insights into their comparative analysis, as well as future prospects. Notably, empirical investigations suggest that moiré-based methodologies reign supreme. This discourse delineates the technical challenges and future development trends facing each warpage measurement method. In essence, the goal of this study is to furnish concise and coherent guidelines and support for engineers and researchers seeking to navigate the realm of warpage measurement within the sphere of advanced electronic packaging. 

45. Implementation of the Homogenization Method in the Numerical Estimation of Wafer Warpage

Soufyane Belhenini 1,*,Imad El Fatmi 1,Caroline Richard 2,Abdellah Tougui 3 and Fabrice Roqueta 4

1 Smart Structures Laboratory, University of Ain Temouchent, BP 284 Route S.B.A, Ain Temouchent 46000, Algeria

2 GREMAN UMR CNRS 7347, Université de Tours, Insa Centre Val de Loire, 37200 Tours, France

3 Laboratory of Mechanics Gabriel Lamé, University of Tours, 37200 Tours, France

4 STMicroelectronics, 10 Rue Thalès de Milet CS 97155, 37071 Tours, France

* Author to whom correspondence should be addressed.

Given the growing global demand for high-performance microcomponents, while keeping the size of the microcomponents as small as possible, several manufacturers have chosen to increase the number of thin layers to increase the integration density. These thinner layers cause warping-type deformations during processing. In this study, warping during the development of a stacking composed of a silicon substrate coated with two thin layers, one dielectric in undoped silicate glass (USG) and the other metallic in platinum, was numerically analyzed and validated by comparison with experimental measurements. The numerical study presented in this paper has several components that make it simple and reliable. Indeed, simplifications of the loading conditions were introduced and validated by comparison with experimental results. Another part of the simplification is to integrate a homogenization approach to reduce the number of calculations. The efficiency and precision of the homogenization approach were validated for the mechanical and thermomechanical models by comparing the heterogeneous and homogenized models. 

44. Implementation of the Homogenization Method in the Numerical Estimation of Wafer Warpage 

 Soufyane Belhenini 1,*,Imad El Fatmi 1,Caroline Richard 2,Abdellah Tougui 3 and Fabrice Roqueta 4 

1 Smart Structures Laboratory, University of Ain Temouchent, BP 284 Route S.B.A, Ain Temouchent 46000, Algeria

2 GREMAN UMR CNRS 7347, Université de Tours, Insa Centre Val de Loire, 37200 Tours, France

3 Laboratory of Mechanics Gabriel Lamé, University of Tours, 37200 Tours, France

4 STMicroelectronics, 10 Rue Thalès de Milet CS 97155, 37071 Tours, France

*Author to whom correspondence should be addressed.

Given the growing global demand for high-performance microcomponents, while keeping the size of the microcomponents as small as possible, several manufacturers have chosen to increase the number of thin layers to increase the integration density. These thinner layers cause warping-type deformations during processing. In this study, warping during the development of a stacking composed of a silicon substrate coated with two thin layers, one dielectric in undoped silicate glass (USG) and the other metallic in platinum, was numerically analyzed and validated by comparison with experimental measurements. The numerical study presented in this paper has several components that make it simple and reliable. Indeed, simplifications of the loading conditions were introduced and validated by comparison with experimental results. Another part of the simplification is to integrate a homogenization approach to reduce the number of calculations. The efficiency and precision of the homogenization approach were validated for the mechanical and thermomechanical models by comparing the heterogeneous and homogenized models. 

43. Polymer Composites Bipolar Plates for PEMFCs 

E. Planes *, L. Flandin, N. Alberola 

* LEPMI, UMR 5279, CNRS Grenoble INP -Université de Savoie -Université J. Fourier LMOPS Bât. IUT, Université de Savoie, Campus Savoie Technolac, F-73376 Le Bourget-du Lac Cedex, France 

In order to improve their commercial liability, many scientific and technological efforts are being performed on fuel cell systems. The bipolar plates represent a major part of the stack with about 80% of the total weight and 30 to 40% of cost. On the technical point of view, bipolar plates should fulfill functional challenges besides ensuring the mechanical strength of the stack. As a result an optimal material for bipolar plate application should present an unusual balance of properties, essentially high electrical conductivity and good mechanical strength. To date, many different materials for bipolar plates have been investigated and an alternative solution consists in polymer composite that com-bine the processability and mechanical properties of the polymeric phase and the conductivity of the carbon fillers. This communication provides a state-of-the-art review of the current development, manufacturing and structure-property re-lationship of polymer composites designed for bipolar plates applications. Both thermoset resins and thermoplastics were considered and combined to many different carbon fillers: graphite, carbon fibers, carbon black, carbon nanotubes. The interests and limitations of these formulations are presented in terms of processability and most relevant properties. A debate on the optimization of electrical and mechanical properties is presented. 

42. Effect of different carbon fillers on the properties of graphite composite bipolar plate 

 R.B. Mathur *, S.R. Dhakate, D.K. Gupta, T.L. Dhami, R.K. Aggarwal 

* Carbon Technology Unit, Engineering Materials Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012, India 

A bipolar plate is one of the key components of a proton exchange membrane fuel cell. Development of a suitable material for use as bipolar plate is scientifically and technically important due to the need to maintain high-electrical conductivity, better mechanical properties and low-manufacturing cost. A replacement of the conventional graphite bipolar plate is reported which is twice as strong as the conventional monolithic graphite plate. These plates have been produced by compression molding technique using natural graphite, synthetic graphite, carbon fiber and carbon black as reinforcing constituents and phenolic resin as a binder matrix. A judicious combination and their respective proportions, could produce a composite plate with bulk density 1.8–1.90 g/cm3, electrical resistivity between 0.002 and 0.007 cm, shore hardness ∼65, flexural strength ∼45 MPa and flexural modulus ∼12 GPa. The characteristics and the performance of the composite plate developed by us are compared with the commercially available bipolar plates. A power density of ∼500mW/cm2 was achieved at 1400mA/cm2 current density when the above composite plate was used as a bipolar plate in a unit fuel cell. 

41. Fabrication of aluminum bipolar plates with Archimedes’ screw‑shaped channels: a rubber pad forming process assessment 

S. J. Hashemi 1  · Amir H. Roohi 2

1 Department of Mechanical Engineering, Faculty of Enghelab-e Eslami, Tehran Branch, Technical and Vocational University (TVU), Tehran, Iran. 

2 Department of Mechanical Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran. 

Bipolar plates are one of the most important components of polymer membrane fuel cells. In this manuscript, the rubber pad forming of aluminum bipolar plates with Archimedes’ screw-shaped channels and draft angle of 90◦ has been investigated. Hence, all possible combinations of the process parameters were determined and corresponding experimentations performed in order to investigate the efects of the rubber hardness, punch speed and the hydraulic press force. In this regard, three rubber pads including polyurethane, silicone and natural rubber were used. Channel depth and thinning percentage in the corner of the channel are measured and the efect of each parameter is analyzed. Based on the results, the maximum channel depth was achieved using a silicone pad with a hardness of 60 Shore A. Using a rubber pad with a very high and low hardness number, both, reduces the depth of channel. Furthermore, as the punch speed increases, the channel depth increases and the thinning percentage, as well. 

40. Simulation of an innovative flow-field design based on a bio inspired pattern for PEM fuel cells 

R. Roshandel*, F. Arbabi, G. Karimi Moghaddam 

Department of Energy Engineering, Sharif Energy Research Institutes, Sharif University of Technology, P.O. Box 11365-9567, Tehran, Iran 

Proton exchange membrane (PEM) fuel cell performance is directly related to the bipolar plate design and their channels pattern. Power enhancements can be achieved by optimal design of the type, size, or patterns of the channels. It has been realized that the bipolar plate design has significant role on reactant transport as well as water management in a PEM Fuel cell. Present work concentrates on improvements in the fuel cell performance by optimization of flow-field design and channels configurations. A threedimensional, multi-component numerical model of flow distribution based on NaviereStokes equations using individual computer code is presented. The simulation results showed excellent agreement with the experimental data in the previous publications. In this paper, a new bipolar plate design inspired from the existed biological fluid flow patterns in the leaf is presented and analyzed. The main design criteria in this research are based on more uniform velocity distribution and more homogeneous molar spreading of species along the flow channels and also higher voltage and power density output in different current densities. By developing a numerical code it was found that the velocity and pressure profiles on catalyst surface are much more uniform, reactant concentration on catalyst surface is very more homogeneous and the power density is higher than parallel and serpentine flow channels up to 56% and 26% respectively. 

39. Investigation of optimization and evaluation criteria for flow field in proton exchange membrane fuel cell: A critical review 

Yu Zhou a,b , Ben Chen a,b,* 

a Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan, 430070, China 

b Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan, 430070, China 

The optimal design of the flow field is of great significance for the performance enhancement and commercial application of proton exchange membrane fuel cells (PEMFCs). The optimization of water-gas transport characteristics in the flow field is the key research content and the key to enhancing the performance and durability of PEMFC. Flow field design evaluation criteria are the mainstream methods for judging the water-gas transport characteristics of flow fields. This paper reviews the current status of PEMFC flow field optimization design research, emphasizes multiple flow field design evaluation criteria, and is dedicated to achieving a standardized, integrated and commercialized design of commercial flow field plates (FFP). Further, a flow field design criterion with a cost-effectiveness index as an important criterion is proposed to optimize the high cost of commercial FFP and poor water-gas transport performance at high current densities. In order to obtain a commercial FFP with better comprehensive performance and better cost-effectiveness, and ultimately promote the commercialization of PEMFC. 

38. Carbon materials in composite bipolar plates for polymer electrolyte membrane fuel cells: A review of the main challenges to improve electrical performance

Renato A. Antunes a,∗, Mara C.L. de Oliveira b, Gerhard Ett b, Volkmar Ett b 

a Engineering, Modeling and Applied Social Sciences Center (CECS), Federal University of ABC (UFABC), 09210-170 Santo André, SP, Brazil 

b Electrocell Ind. Com. Equip. Elet. LTDA, Technology, Entrepreneurship and Innovation Center (CIETEC), 05508-000 São Paulo, SP, Brazil 

The technology of polymer electrolyte membrane (PEM) fuel cells is dependent on the performance of bipolar plates. There is a strong relationship between thematerial used in themanufacturing of the bipolar plate and its final properties. Graphite–polymer composite bipolar plates are well-established commercial products. Several other carbon based fillers are tested. Carbon nanotubes, carbon fibers, carbon black, graphite nanoplatelets and expanded graphite are examples of such materials. Structural characteristics of these particles such as morphology and size have decisive influence on the final properties of bipolar plates. Furthermore, the volumetric fraction of the filler is of prime importance. There is plenty of information on individual aspects of specific composite bipolar plates in the literature. Notwithstanding, the analysis of structure–property relationship of these materials in a comprehensive source is not found. In this paper, relevant topics on the structural aspects of carbon based fillers and how they influence the final electrical performance of composite bipolar plates are discussed. It is intended that this document contribute to the development of new and maximized products to the PEM fuel cell industry. 

37. Polymer composites bipolar plates for PEMFCs 

E. Planes a,∗ , L. Flandin a , N. Alberola a 

a LEPMI, UMR 5279, CNRS Grenoble INP - Université de Savoie - Université J. Fourier LMOPS Bât. IUT, Université de Savoie, Campus Savoie Technolac, F-73376 Le Bourget-du Lac Cedex, France 

In order to improve their commercial liability, many scientific and technological efforts are being performed on fuel cell systems. The bipolar plates represent a major part of the stack with about 80% of the total weight and 30 to 40% of cost. On the technical point of view, bipolar plates should fulfill functional challenges besides ensuring the mechanical strength of the stack. As a result an optimal material for bipolar plate application should present an unusual balance of properties, essentially high electrical conductivity and good mechanical strength. To date, many different materials for bipolar plates have been investigated and an alternative solution consists in polymer composite that combine the processability and mechanical properties of the polymeric phase and the conductivity of the carbon fillers. This communication provides a state-of-the-art review of the current development, manufacturing and structure-property relationship of polymer composites designed for bipolar plates applications. Both thermoset resins and thermoplastics were considered and combined to many different carbon fillers: graphite, carbon fibers, carbon black, carbon nanotubes. The interests and limitations of these formulations are presented in terms of processability and most relevant properties. A debate on the optimization of electrical and mechanical properties is presented. 

36. Prediction of surface morphology and reflection spectrum of laser-induced periodic surface structures using deep learning 

Hojun Na 1 , Jeonghyun Yoo 1 , Hyungson Ki * 

1 Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, South Korea 

Laser-induced periodic surface structures have been extensively explored as an enabling tool for fabricating various optical surfaces because the resulting surface ripples can effectively modify surface reflectance. Here, we propose a deep-learning-based model for predicting high-quality surface scanning electron microscopy (SEM) images with detailed surface morphology corresponding to unexplored process conditions. In addition, the reflectance value at 550 nm and reflection spectra from the generated (or original) SEM images were predicted. To obtain training data, stainless steel 304 specimens were processed with femtosecond laser pulses on a large process window consisting of 32 process conditions to obtain SEM images with various surface morphologies and corresponding reflection spectra. The image prediction model is based on a conditional generative adversarial network, which generates a surface SEM image from the laser fluence and scanning speed values. The reflectance prediction model was developed based on ResNet152 and Long-Short Term Memory network. The average ac curacies for the pattern period and ripple width were 98.2 and 94.6 %, respectively, and the L norm error for the reflection spectra was less than 4 %. It was demonstrated that the reflection spectra can be accurately predicted using only surface images, which can also be accurately generated from process parameters. 

35. Machine learning‑based microstructure prediction during laser sintering of alumina 

Jianan Tang1,3, Xiao Geng2, Dongsheng Li4, Yunfeng Shi5,*, Jianhua Tong2, Hai Xiao1,3* & Fei Peng2,3,*

1Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634, USA. 

2Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA. 

3Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Anderson, SC 29625, USA. 

4Advanced Manufacturing LLC, East Hartford, CT 06108, USA. 5Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Materials Research Center, Troy, NY 12180-3590, USA. 

*email: shiy2@rpi.edu; haix@ clemson.edu; fpeng@clemson.edu 

It has been a significant focus in advanced manufacturing and material science to predict the product’s micro structure under a specific processing condition. This is because the material’s microstructure has huge influences on the material’s properties. Conventionally, such knowledge is obtained from trial-and-error experiments. This approach requires extensive and long-term efforts. Substantial progress has been made in the physics-based models that predict microstructures under known governing laws1–10. However, these physics-based models usu ally require high computational costs. It is unrealistic to use physics-based models for real-time microstructure prediction in the advanced manufacturing systems. The data-driven machine learning (ML) approaches11 offer potent alternative tools to simulate the material’s microstructure. After training, the data-driven ML algorithms can generate the simulation results almost instantly, without knowing the governing laws. Deep learning algorithms12, especially generative adversarial networks (GANs)13, have demonstrated out standing performances in synthesizing highly realistic images14–16. The material’s microstructure is often repre sented as micrographs from scanning electron microscopy (SEM). Thus, simulating material’s microstructure using GANs has attracted great interests. For example, GANs have been developed to stochastically generate porous media’s solid-void structure17,18. A framework was developed to optimize the GAN-generated microstruc tures with desired material properties19. A modified GAN has been used to synthesize porous electrode micro structures for electrochemical energy store devices20. In another study, a modified conditional GAN (CGAN) was used to reconstruct metal microstructures based on various cooling methods21. T he research mentioned above on GAN-based micrograph synthesis, though successful, is focused on the regeneration of the microstructures from the trained processing conditions. It would be desirable to use machine learning to predict the microstructure under the previously unexplored processing conditions. 

34. Machine learning based prediction of melt pool morphology in a laser-based powder bed fusion additive manufacturing process 

Zhibo Zhang a,Chandan Kumar Sahu b,Shubhendu Kumar Singh b,Rahul Rai b,ZhuoYang c and Yan Lu d 

a Manufacturing and Design Lab (MADLab), University at Buffalo, Buffalo, NY, USA; 

b Geometric Reasoning and Artificial Intelligence Lab (GRAIL), Clemson University International Center for Automotive Research (CU-ICAR), Clemson, SC, USA; 

c Mechanical and Industrial Engineering Department, University of Massachusetts Amherst, Amherst, MA, USA; 

d National Institute of Standards and Technology, Gaithersburg, MD, USA 

Laser-based powder bed fusion (L-PBF) has become the de facto choice for metal additive manufacturing (AM) processes. Even after considerable research investments, components manufactured using L-PBF lack consistency in their quality. Realizing the crucial role of the melt pool in controlling the final build quality, we predict theorphology of theeltpool directly from the build commands in an L-PBF process. We leverage machine learning techniques to predict quantitative attributes like the size as well as qualitative attributes like the shape of the melt pool. The area of the melt pool is predicted using an LSTM network. The outlined LSTM-based approach estimates the area with 90.7% accuracy. The shape is inferred by synthesising the images of the melt pool by using a Melt Pool Generative Adversarial Network (MP-GAN). The synthetic images attain a structural simi larity score of 0.91. The precision and accuracy of the results showcase the efficacy of the outlined approach and pavethewayforreal-time monitoring and control of the melt pool to build products with consistently better quality. 

33. Experimental and Numerical Investigation of the Diffusion of a Confined Wall Jet through a Perforated Plate 

Moussa Diop1*, Denis Flick2, Graciela Alvarez1, Jean Moureh1 

1 Refrigerating Process Engineering Unit, INRAE Antony, Antony, France 

2 Université Paris Saclay, INRAE, AgroParisTech, UMR SayFood, Massy, France 

When performing numerical modeling of fluid flows where a clear medium is adjacent to a porous medium, a degree of difficulty related to the condition at the interface between the two media, where slip velocity exists, is encountered. A similar situation can be found when a jet flow interacts with a perforated plate. The numerical modeling of a perforated plate by meshing in detail each hole is most often impossible in a practical case (many holes with different shapes). Therefore, perforated plates are often modeled as porous zones with a simplified hypothesis based on pressure losses related to the normal flow through the plate. Nevertheless, previous investigations of flow over permeable walls highlight the impossibility of deducing a universal analytical law governing the slip velocity coefficient since the latter depends on many parameters such as the Reynolds number, porosity, interface structure, design of perforations, and flow direction. This makes the modeling of such a configuration difficult. The present study proposes an original numerical interface law for a perforated plate. It is used to model the turbulent jet flow interacting with a perforated plate considered as a fictitious porous medium without a detailed description of the perforations. It considers the normal and tangential effects of the flow over the plate. Validation of the model is realized through comparison with experimental data. 

32. Visualizing laser ablation using plasma imaging and deep learning 

JAMES A. GRANT-JACOB, * BEN MILLS, AND MICHALIS N. ZERVAS 

Optoelectronics Research Centre, University of Southampton, SO17 1BJ, UK 

* J.A.Grant-Jacob@soton.ac.uk 

High power laser ablation can lead to the creation of plasma and the emission of bright light, which can prevent the direct observation of the workpiece. Alternative techniques for enabling the visualization of the sample during laser machining are therefore of interest. Here, we show that the plasma created during laser ablation, when viewed perpendicular to the sample surface, contains information regarding the appearance of the sample. Specifically, we show that deep learning can predict the 2D appearance of the sample, directly from 2D projected images of the plasma produced during single pulse femtosecond laser ablation. In addition, this approach also enables the identification of the pulse energy of the most recent laser pulse used to machine the sample. This work could have applications across laser materials processing in research and industry, in cases where there is a requirement for real-time visualization of the sample surface during laser ablation. 

31. A review of composite bipolar plates in proton exchange membrane fuel cells: Electrical properties and gas permeability

Kwang Il Jeong a, Jaehyung Oh a, Seung A Song b, Dongyoung Lee c, Dai Gil Lee a, Seong Su Kim a,* 

aDepartment of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea

bDepartment of Mechanical and Manufacturing Engineering, The University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada

cStandard Energy, Techno 6-ro Yuseong-gu Daejeon, Republic of Korea

Proton exchange membrane fuel cells (PEMFCs) consist of bipolar plates, end plates, membrane electrode assemblies, and gas diffusion layers. Among these components, the bipolar plates (BPs) are the main components because they contribute significantly to the volume, cost, and weight of the PEMFC. Owing to their good electrical and thermal conductivities, graphite and metallic materials are conventional materials for BPs. However, graphite BPs lack mechanical strength, and it is difficult to machine channels on these BPs due to the intrinsic brittleness of the material. Metallic BPs have relatively high density and require surface modification and coating to suppress surface corrosion. Recently, thermoplastic or thermosetting composites reinforced with carbon-based conductive fillers have attracted significant attention because of their superior corrosion resistance and low density. In this paper, we comprehensively review the electrical conductivities of composite BPs in terms of their carbon-based fillers, matrix materials, and the manufacturing process. Next, various surface treatments aimed at improving the interfacial contact resistance of composites are discussed. Finally, methods used for reducing gas permeabilities of composite BPs are summarized. 

30. An overview of bipolar plates in proton exchange membrane fuel cells

Aubrey Tang 1,2, Louis Crisci 1,2, Leonard Bonville 1,2, Jasna Jankovic 1,2,* 

1 Center for Clean Energy Engineering, University of Connecticut, 44 Weaver Road, Unit 5233, Storrs, CT 06269 

2 Institute of Materials Science, University of Connecticut, 97 North Eagleville Road, Storrs CT 06269 

Bipolar plates are a crucial component of proton exchange membrane fuel cells. They are responsible for transporting reactant gases, carrying the current from the membrane electrode assembly to the end plates, providing heat and water management, and separating the individual cells. However, these plates also contribute to 80% of the fuel cell's weight, 50% of its volume, and 40% of its cost, posing a barrier to the commercialization of fuel cells. This paper provides a comprehensive review of the materials and manufacturing processes used in the fabrication of bipolar plates as well as recent research conducted on the improvement of bipolar plate weight, volume, and cost through material selection and manufacturing methods. Additive manufacturing is highlighted in this work as an innovative manufacturing method to produce bipolar plates. Novel contributions in this paper include a detailed explanation of traditional manufacturing processes for metallic and graphitic-polymer bipolar plates as well as a cost comparison between additive and traditional manufacturing processes. 

29. Engineering the catalyst layers towards enhanced local oxygen transport of Low-Pt proton exchange membrane fuel cells: Materials, designs, and methods 

Shiqing Liu a , Shu Yuan a , Yuwei Liang a , Huiyuan Li a , Zhiling Xu a , Qian Xu c , Jiewei Yin a , Shuiyun Shen a , Xiaohui Yan a,* , Junliang Zhang a,b 

a Institute of Fuel Cells, School of Mechanical Engineering, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai, China 

b MOE Key Laboratory of Power Machinery and Engineering, Shanghai Jiao Tong University, Dongchuan Rd. 800, Shanghai, China 

c Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China 

Proton exchange membrane fuel cells (PEMFCs) help to achieve decarbonized energy demand due to their advantages of no pollution emission and high power efficiency. But the commercialization of fuel cells has encountered difficulties due to the high-cost issue. The key to addressing the cost issue of PEMFCs lies in reducing Pt amount. However, concentration polarization in the high current density region increases as the decrease of Pt loading, of which the local transport loss of oxygen in the cathode catalyst layer (CCL) occupies the most significant part. Therefore, reducing local oxygen transport resistance is necessary to achieve ultra-low Pt loading in practical PEMFC. This paper focuses on summarizing various electrode design methods for the CCL that optimize the local transport resistance of oxygen, including modifications to the ionomer layer, catalyst structure, and overall electrode structure. Each improvement method is explained with the mechanism of the local oxygen transport process, investigating the effect of different ionomer and Ptbased nanoparticle structures, distribution, and surface chemistries on the local transport pathways. The insights proposed in this paper provide recommendations for the fabrication and design of high-efficiency low-platinum fuel cells. 

28. Preparation, performance and challenges of catalyst layer for proton exchange membrane fuel cell 

Meng Xie 1,2,Tiankuo Chu 1,2,Tiantian Wang1,2,Kechuang Wan 1,2,Daijun Yang 1,2,Bing Li 1,2,*,Pingwen Ming 1,2 and Cunman Zhang 1,2 

1 School of Automotive Studies, Tongji University (Jiading Campus), 4800 Cao’an Road, Shanghai 201804, China

2 Clean Energy Automotive Engineering Center, Tongji University (Jiading Campus), 4800 Cao’an Road, Shanghai 201804, China

* Author to whom correspondence should be addressed.

In this paper, the composition, function and structure of the catalyst layer (CL) of a proton exchange membrane fuel cell (PEMFC) are summarized. The hydrogen reduction reaction (HOR) and oxygen reduction reaction (ORR) processes and their mechanisms and the main interfaces of CL (PEM|CL and CL|MPL) are described briefly. The process of mass transfer (hydrogen, oxygen and water), proton and electron transfer in MEA are described in detail, including their influencing factors. The failure mechanism of CL (Pt particles, CL crack, CL flooding, etc.) and the degradation mechanism of the main components in CL are studied. On the basis of the existing problems, a structure optimization strategy for a high-performance CL is proposed. The commonly used preparation processes of CL are introduced. Based on the classical drying theory, the drying process of a wet CL is explained. Finally, the research direction and future challenges of CL are pointed out, hoping to provide a new perspective for the design and selection of CL materials and preparation equipment. 

27. Structure, Property, and Performance of Catalyst Layers in Proton Exchange Membrane Fuel Cells 

Jian Zhao1  · Huiyuan Liu1  · Xianguo Li1,*

1 Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada  

Catalyst layer (CL) is the core component of proton exchange membrane (PEM) fuel cells, which determines the performance, durability, and cost. However, difculties remain for a thorough understanding of the CLs’ inhomogeneous structure, and its impact on the physicochemical and electrochemical properties, operating performance, and durability. The inhomogeneous structure of the CLs is formed during the manufacturing process, which is sensitive to the associated materials, composition, fabrication methods, procedures, and conditions. The state-of-the-art visualization and characterization techniques are crucial to examine the CL structure. The structure-dependent physicochemical and electrochemical properties are then thoroughly scrutinized in terms of fundamental concepts, theories, and recent progress in advanced experimental techniques. The relation between the CL structure and the associated efective properties is also examined based on experimental and theoretical fndings. Recent studies indicated that the CL inhomogeneous structure also strongly afects the performance and degradation of the whole fuel cell, and thus, the interconnection between the fuel cell performance, failure modes, and CL structure is comprehensively reviewed. An analytical model is established to understand the efect of the CL structure on the efective properties, performance, and durability of the PEM fuel cells. Finally, the challenges and prospects of the CL structure-associated studies are highlighted for the development of high-performing PEM fuel cells. 

26. Permeability and Turbulence Over Perforated Plates

Haris Shahzad 1  · Stefan Hickel 1   · Davide Modesti 1  

1 Aerodynamics Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 2, 2629 HS Delft, South Holland, The Netherlands 

We perform direct numerical simulations of turbulent fow at friction Reynolds number, Re ≈ 500−2000 grazing over perforates plates with moderate viscous-scaled orifce diameter d+ ≈ 40 − 160 and analyse the relation between permeability and added drag. Unlike previous studies of turbulent fows over permeable surfaces, we fnd that the fow inside the orifces is dominated by inertial efects, and that the relevant permeability is the Forchheimer and not the Darcy one. We fnd evidence of a fully rough regime where the relevant length scale is the inverse of the Forchheimer coefcient, which can be regarded as the resistance experienced by the wall-normal fow. Moreover, we show that, for low porosities, the Forchheimer coefcient can be estimated with good accuracy using a simple analytical relation. 

25. A pressure-loss model for flow-through round-hole perforated plates of moderate porosity and thickness in laminar and turbulent flow regimes 

Shuai Li a,∗, Lars Davidson a, Shia-Hui Peng a,b  

a Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden 

b FOI - Swedish Defense Research Agency, SE-164 90 Stockholm, Sweden 

In this paper, we proposed a novel fluid flow model for pressure loss through plates with circular perforations in both laminar and turbulent flows. The design of this model is based on the recent measurements conducted at ONERA in the framework of the ongoing European Union H2020 INVENTOR project, as well as an existing model for laminar flows. The new model is then validated against existing numerical simulations in the laminar regime and experiments in the turbulent regime. Overall, the predictions given by the new model agree well with the numerical simulations and experiments, and are superior to other models in the literature. This is significant, considering that the present model is much simpler than these previous models. To demonstrate the applicability of the new model in numerical simulations, two-dimensional channel flows are simulated using Reynolds-averaged Navier–Stokes (RANS) equations with the new model as a pressure-drop source term added to the momentum equations. Results show that the RANS predictions agree very well with the present model predictions. 

24. Gas diffusion layers for PEM fuel cells: Materials, properties and manufacturing – A review

Grigoria Athanasaki a, Arunkumar Jayakumar b, A.M. Kannan a, *

a Fuel Cell Laboratory, The Polytechnic School, Ira A. Fulton Schools of Engineering, Arizona State University, Mesa, AZ, 85212, USA

b Green Vehicle Technology Research Centre, Department of Automobile Engineering, SRM-Institute of Science and Technology, Kattankulathur, 603203, India

The complexity in proton exchange membrane fuel cell (PEMFC) stack stems from the fact that numerous physio-chemical processes as well as multi-functional components are involved in its operation. Among the various components a Gas Diffusion Layer (GDL) being an integral component that plays a significant role in determining the performance, durability, and the dynamic characteristics, when air is used as oxidant. In addition, it serves as an armour to safeguard the membrane (Nafion), which is a delicate as well as one of the most expensive components of the PEMFC stack. A comprehensive insight on the GDL can help us to assess the fuel cell stack performance and durability. Apparently, the gas (hydrogen and air/oxygen) being converted to the energy in a PEM fuel cell needs to be diffused uniformly for which surface attributes and porosity must also be well interpreted. This review is a comprehensive assessment made on the fundamental mechanism of the diffusion process along with the various materials involved and evaluating their pros and cons. Eventually, the various manufacturing techniques involved in the GDL fabrication process are also reviewed holistically. It is envisaged that the additive manufacturing process can be a potential option to fabricate a GDL in a cost-effective and simple manufacturing approach. 

23. Fabrication and investigation of polymer-based carbon composite as gas diffusion layer of proton exchange membrane of fuel cells 

Reza Taherian 1 , Mohammad Matboo Ghorbani 1 , Mohammad Nasr 2 , Seyed Rahim Kiahosseini 3

1 Chemical & Material Engineering Department, Shahrood University of Technology, Shahrood, Iran 

2 Institute of Materials and Energy, Iranian Space Research Center, 7th Kilometer of Imam Ave., Isfahan, Iran 

3 Department of Engineering, Damghan Branch, Islamic Azad University, Damghan, Iran 

Carbon paper is one of the most important component in polymer electrolyte PEMfuel cells. In this research, we report two methods of manufacturing carbon papers that do not need the steps of carbonization and graphitizationare common steps in carbon paper. At first method (mixing method), the short carbon fibers have a randomdistributionin the composite and in the second method (fabric method), the long carbon fibers are oriented inplanarconfiguration .In order to investigate on the properties, the effect of paper thickness and expanded graphitevaluehave been considered and compared with Toray carbon paper. The characterization is performed by scanningelectronmicroscope, maximum pore size, mean pore size, permeability, electrical conductivity, flexibility, and performance(I-V)curve. The results show that mixing method resulting in a higher electrical conductivity, pore size, and permeability, aswell as I-V curve similar to Toray paper. In addition, the cost estimates and flexibility test show that both fabricandmixing methods results in a much lower cost, due to removing the graphitization and carbonization steps, andmoreflexible samples in comparison to Toray paper 

22. Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered 

Arunkumar Jayakumar 1,*,Sarat Singamneni 1,Maximiano Ramos 1,Ahmed M Al-Jumaily 1 and Sethu Sundar Pethaiah 2 

1Mechanical Engineering Department, Auckland University of Technology, Auckland 1010, New Zealand

2Gashubin Engineering Pte. Ltd., 8 New Industrial Road, Singapore 536200, Singapore

*Author to whom correspondence should be addressed.

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time. 

21. Porous Material (Titanium Gas Diffusion Layer) in Proton Exchange Membrane Fuel Cell/Electrolyzer: Fabrication Methods & GeoDict: A Critical Review

Javid Hussain 1,2,†,Dae-Kyeom Kim 2,†,Sangmin Park 1,2,Muhammad-Waqas Khalid 1,2,Sayed-Sajid Hussain 3,Bin Lee 4,Myungsuk Song 2,* and Taek-Soo Kim 1,2,* 

1Industrial Technology, University of Science and Technology, Daejeon 34113, Republic of Korea

2Korea Institute for Rare Metals, Korea Institute of Industrial Technology, Incheon 21999, Republic of Korea

3Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea

4Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University, Yongin 17104, Republic of Korea

*Authors to whom correspondence should be addressed.

†These authors contributed equally to this work.

Proton exchange membrane fuel cell (PEMFC) is a renewable energy source rapidly approaching commercial viability. The performance is significantly affected by the transfer of fluid, charges, and heat; gas diffusion layer (GDL) is primarily concerned with the consistent transfer of these components, which are heavily influenced by the material and design. High-efficiency GDL must have excellent thermal conductivity, electrical conductivity, permeability, corrosion resistance, and high mechanical characteristics. The first step in creating a high-performance GDL is selecting the appropriate material. Therefore, titanium is a suitable substitute for steel or carbon due to its high strength-to-weight and superior corrosion resistance. The second crucial parameter is the fabrication method that governs all the properties. This review seeks to comprehend numerous fabrication methods such as tape casting, 3D printing, freeze casting, phase separation technique, and lithography, along with the porosity controller in each process such as partial sintering, input design, ice structure, pore agent, etching time, and mask width. Moreover, other GDL properties are being studied, including microstructure and morphology. In the future, GeoDict simulation is highly recommended for optimizing various GDL properties, as it is frequently used for other porous materials. The approach can save time and energy compared to intensive experimental work. 

20. A Review of Water Management in Polymer Electrolyte Membrane Fuel Cells 

Mengbo Ji and Zidong Wei * 

State Key Laboratory of Power Transmission Equipment & System Security and New Technology, School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400044, China 

At present, despite the great advances in polymer electrolyte membrane fuel cell (PEMFC) technology over the past two decades through intensive research and development activities, their large-scale commercialization is still hampered by their higher materials cost and lower reliability and durability. In this review, water management is given special consideration. Water management is of vital importance to achieve maximum performance and durability from PEMFCs. On the one hand, to maintain good proton conductivity, the relative humidity of inlet gases is typically held at a large value to ensure that the membrane remains fully hydrated. On the other hand, the pores of the catalyst layer (CL) and the gas diffusion layer (GDL) are frequently flooded by excessive liquid water, resulting in a higher mass transport resistance. Thus, a subtle equilibrium has to be maintained between membrane drying and liquid water flooding to prevent fuel cell degradation and guarantee a high performance level, which is the essential problem of water management. This paper presents a comprehensive review of the state-of-the-art studies of water management, including the experimental methods and modeling and simulation for the characterization of water management and the water management strategies. As one important aspect of water management, water flooding has been extensively studied during the last two decades. Herein, the causes, detection, effects on cell performance and mitigation strategies of water flooding are overviewed in detail. In the end of the paper the emphasis is given to: (i) the delicate equilibrium of membrane drying vs. water flooding in water management; (ii) determining which phenomenon is principally responsible for the deterioration of the PEMFC performance, the flooding of the porous electrode or the gas channels in the bipolar plate, and (iii) what measures should be taken to prevent water flooding from happening in PEMFCs. 

19. Factors influencing the performance of PEM fuel cells: A review on performance parameters, water management, and cooling techniques 

Rupinder Singh 1, Amandeep Singh Oberoi 2,*, Talwinder Singh 1

1 Mechanical Engineering Department, Punjabi University, Patiala, India 

2 Mechanical Engineering Department, Thapar Institute of Engineering and Technology, Patiala, India 

This paper addresses the effects of critical parameters that affect the performance and lifespan of proton exchange membrane (PEM) fuel cells. Amongst all, control of excess water content and dehydration in PEM fuel cells is the major issue under various operating conditions. Therefore, their effects on cathode, anode, gas diffusion layer (GDL), catalyst layer (CL), and flow channels are summarized in the initial part of this paper. Various active cooling strategies such as air cooling, liquid cooling, and phase change method to extract the waste heat from the stack are represented. The lateral part of this paper throws light on the role of heat pipes, working fluid, and the effect of the addition of nanofluid with pertinent filling ratio (FR) in cooling of PEM fuel cells. This work is intended to aid the selection of cooling methods for PEM fuel cells through the consideration of the variety of affecting parameters preceding major expenditure for wide-scale production. In future, cost comparison associated with the cooling techniques of the fuel cell would be evaluated. 

18. Enhanced performance of proton exchange membrane fuel cell by introducing nitrogen-doped CNTs in both catalyst layer and gas diffusion layer 

Sanying Hou a,b , Bin Chi a , Guangzhi Liu a , Jianwei Ren c , Huiyu Song a,*, Shijun Liao a,* 

a The Key Laboratory of Fuel Cell Technology of Guangdong Province & the Key Laboratory of New Energy Technology of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, Guangdong, China 

b School of Chemistry and Chemical Engineering, University of South China, Hengyang 421001, China 

c HySA Infrastructure Centre of Competence, Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), PO Box 395, Pretoria 0001, South Africa 

The performance of the proton exchange membrane fuel cell (PEMFC) is significantly improved through introducing nitrogen-doped carbon nanotubes (NCNTs) into the catalyst layer (CL) and microporous layer (MPL) of the membrane electrode assembly (MEA), it reveals by SEM images that the NCNTs are uniformly dispersed in CL and MPL, resulting in the more plenty of porosity, higher surface area, better conductivity, and better prevention of the layer cracks. The BET surface area and pore volume of MPL are increased by 88% and 77% respectively with the addition of 20 wt% of NCNTs in MPL. The membrane electrode assembly (MEA) with adding 20 wt% NCNTs both in cathode CL and in cathode GDL can yield the best cell performance. At a celltemperature of 70 C and 30 psi back pressures, the current density is up to 1000 mAcm2 at 0.7 V and 1600 mAcm2 at 0.6V, and the max power density reaches 997 mWcm2 . 

17. Recent Progress on the Key Materials and Components for Proton Exchange Membrane Fuel Cells in Vehicle Applications

Cheng Wang 1,5,*,Shubo Wang 1,Linfa Peng 2,Junliang Zhang 3,Zhigang Shao 4,Jun Huang 5,Chunwen Sun 6,Minggao Ouyang 5 and Xiangming He 1,5,* 

1 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China

2 State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China

3 School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

4 Fuel Cell System and Engineering Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China

5 State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China

6 Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, China

Fuel cells are the most clean and efficient power source for vehicles. In particular, proton exchange membrane fuel cells (PEMFCs) are the most promising candidate for automobile applications due to their rapid start-up and low-temperature operation. Through extensive global research efforts in the latest decade, the performance of PEMFCs, including energy efficiency, volumetric and mass power density, and low temperature startup ability, have achieved significant breakthroughs. In 2014, fuel cell powered vehicles were introduced into the market by several prominent vehicle companies. However, the low durability and high cost of PEMFC systems are still the main obstacles for large-scale industrialization of this technology. The key materials and components used in PEMFCs greatly affect their durability and cost. In this review, the technical progress of key materials and components for PEMFCs has been summarized and critically discussed, including topics such as the membrane, catalyst layer, gas diffusion layer, and bipolar plate. The development of high-durability processing technologies is also introduced. Finally, this review is concluded with personal perspectives on the future research directions of this area. 

16. A comprehensive review on hybrid power system for PEMFC-HEV: Issues and strategies

Xueqin Lü* , Yan Qu, Yudong Wang, Chao Qin, Gang Liu 

Nowadays, there is a great shortage of non-renewable energy, and the environmental problems such as air pollution caused by automobile exhaust are very serious. The traditional fuel vehicle has been unable to meet the current human needs, so more and more people are concerned about the development of the hybrid electric vehicles (HEVs). Based on proton exchange membrane fuel cell (PEMFC) is a new clean energy without pollution, PEMFC-HEV has a great potential for development. In this review, we have made a comprehensive research on energy management strategy (EMS) of the hybrid power system (HPS) for PEMFC-HEV in recent years. This paper focuses on the EMS of PEMFC as the main power source, the battery and the supercapacitor (SC) as the auxiliary energy in HEV. In this research, the classification of PEMFC-HEV is introduced in detail, and the advantages and disadvantages of various combinations of HPS are summarized. In addition, according to the different requirements and optimization targets of PEMFC-HEV, this paper makes a deep study of the current PEMFC-HEV hybrid system model, and the EMS developed by the researchers. Besides, the simulation and experimental results are compared with each other. From the perspective of strict evaluation, the existing technology can perform more or less. However, high efficiency and optimization performance still fail to achieve high goals. Therefore, the current problems and main control strategies of PEMFC-HEV are discussed and summarized, which is helpful for the development of PEMFC-HEV research in the future. The review will be expected to bring more efforts to the future development of PEMFC-HEV, including faster dynamic response, longer service lifetime, economic optimization, and high efficiency for the PEMFC system. 

15. Developments in fuel cell technologies in the transport sector

A. Alaswad a,* , A. Baroutaji  b , H. Achour  c , J. Carton  c, Ahmed Al Makky  a , A.G. Olabi  a 

a Institute of Energy and Engineering Technologies, University of the West of Scotland, Paisley, Scotland 

b Cork Institute of Technology, Cork, Ireland c School of Mechanical and Manufacturing Engineering, Dublin City University, Dublin, 9, Ireland 

The demand for clean power source which can be used to run the various types of vehicles on the road is increasing on a daily basis due to the fact that high emissions released from internal combustion engine play a significant role in air pollution and climate change. Fuel cell devices, particularly Proton Exchange Membrane (PEM) type, are strong candidates to replace the internal combustion engines in the transport industry. 

The PEMFC technology still has many challenges including high cost, low durability and hydrogen storage problems which limit the wide-world commercialization of this technology. In this paper, the fuel cell cost, durability and performances challenges which are associated with using of fuel cell technology for transport applications are detailed and reviewed. Recent developments that deal with the proposed challenges are reported. Furthermore, problems of hydrogen infrastructure and hydrogen storage in the fuel cell vehicle are discussed. 

14. Critical assessment of power trains with fuel-cell systems and different fuels

B. Hohlein * , S. von Andrian, Th. Grube, R. Menzer 

Institut fur Werkstoffe und Verfahren der Energietechnik IWV-3 , Forschungszentrum Julich FZJ , D-52425 Julich, Germany 

Legal regulations USA, EU are a major driving force for intensifying technological developments with respect to the global Ž . automobile market. In the future, highly efficient vehicles with very low emission levels will include low-temperature fuel-cell systems Ž . PEFC as units of electric power trains. With alcohols, ether or hydrocarbons used as fuels for these new electric power trains, hydrogen as PEFC fuel has to be produced on board. These concepts including the direct use of methanol in fuel-cell systems, differ considerably in terms of both their development prospects and the results achieved so far. Based on process engineering analyses for net electricity generation in PEFC-powered power trains, as well as on assumptions for electric power trains and vehicle configurations, different fuel-cell performances and fuel processing units for octane, diesel, methanol, ethanol, propane and dimethylether have been evaluated as fuels. The possible benefits and key challenges for different solutions of power trains with fuel-cell systemsron-board hydrogen production and with direct methanol fuel-cell DMFC systems have been assessed. Locally, fuel-cell power trains are almost Ž . emission-free and, unlike battery-powered vehicles, their range is comparable to conventional vehicles. Therefore, they have application advantages cases of particularly stringent emission standards requiring zero emission. In comparison to internal combustion engines, using fuel-cell power trains can lead to clear reductions in primary energy demand and global, climate-relevant emissions providing the advantage of the efficiency of the hydrogenrair reaction in the fuel cell is not too drastically reduced by additional conversion steps of on-board hydrogen production, or by losses due to fuel supply provision. 

13. New Perspectives on Fuel Cell Technology: A Brief Review

Norazlianie Sazali 1,*,Wan Norharyati Wan Salleh 2,Ahmad Shahir Jamaludin 3 and Mohd Nizar Mhd Razali 3

1 Faculty of Mechanical & Automotive Engineering Technology, Universiti Malaysia Pahang, Pekan 26600, Pahang, Malaysia

2Advanced Membrane Technology Research Centre (AMTEC), School of Chemical and Energy, Faculty of Engineering, Universiti Teknologi Malaysia, Skudai 81310, Johor Darul Takzim, Malaysia

3Faculty of Manufacturing & Mechatronic Engineering Technology, Universiti Malaysia Pahang, Pekan 26600, Pahang, Malaysia

Energy storage and conversion is a very important link between the steps of energy production and energy consumption. Traditional fossil fuels are a natural and unsustainable energy storage medium with limited reserves and notorious pollution problems, therefore demanding a better choice to store and utilize the green and renewable energies in the future. Energy and environmental problems require a clean and efficient way of using the fuels. Fuel cell functions to efficiently convert oxidant and chemical energy accumulated in the fuel directly into DC electric, with the by-products of heat and water. Fuel cells, which are known as effective electrochemical converters, and electricity generation technology has gained attention due to the need for clean energy, the limitation of fossil fuel resources and the capability of a fuel cell to generate electricity without involving any moving mechanical part. The fuel cell technologies that received high interest for commercialization are polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs), and direct methanol fuel cells (DMFCs). The optimum efficiency for the fuel cell is not bound by the principle of Carnot cycle compared to other traditional power machines that are generally based on thermal cycles such as gas turbines, steam turbines and internal combustion engines. However, the fuel cell applications have been restrained by the high cost needed to commercialize them. Researchers currently focus on the discovery of different materials and manufacturing methods to enhance fuel cell performance and simplify components of fuel cells. Fuel cell systems’ designs are utilized to reduce the costs of the membrane and improve cell efficiency, durability and reliability, allowing them to compete with the traditional combustion engine. In this review, we primarily analyze recent developments in fuel cells technologies and up-to-date modeling for PEMFCs, SOFCs and DMFCs.

12. Effect of pre-annealing strains on annealing texture developments in commercially pure (CP) titanium

S.K. Sahoo a, *, S. Panda a , R.K. Sabat b , G. Kumar c , S.C. Mishra a , U.K. Mohanty a and S. Suwas b 

a Department of Metallurgical & Materials Engineering, NIT Rourkela, Rourkela 769008, India; 

b Department of Materials Engineering, IISc Bangalore, Bangalore 560012, India; 

c Department of Metallurgical Engineering & Materials Science, IIT Bombay, Mumbai 400076, India 

Hexagonal commercially pure titanium (cp-titanium) plates were subjected to unidirectional-rolling (rolling), accumulative roll-bonding (ARB) and crossrolling in a laboratory rolling mill. Rolling and cross-rolling were carried out to impart 90% reduction in thickness and ARB processing was performed for six passes. The deformed plates were then subjected to annealing at 600 °C for a large range of soaking time starting from 0.17 min (10 s) to 30 min. It was observed that the samples were fully recrystallized after 5 min of annealing, irrespective of the rolling processes employed in this study. Also, the samples were seen to develop almost similar texture when annealing was carried out beyond 5 min of annealing time. However, before annealing, the texture development was seen to be different in the respective samples subjected to different rolling processes. The initial ð1 1 2 5Þh1 100i texture present in the deformed structure got strengthened during annealing of the samples under investigation. It was also observed that the texture development was insignificant in ARB-processed samples after annealing 

11. Review and analysis of PEM fuel cell design and manufacturing

Viral Mehta, Joyce Smith Cooper *

Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA

Design and manufacturing alternatives for Proton Exchange Membrane (PEM) fuel cells are described and analyzed within the context of vehicle applications. Specifically, following a review of many alternatives, 16 polymer electrolyte membranes, 2 types of gas diffusion layers (GDL), 8 types of anode catalysts, 4 types of anode catalysts, and 100 bipolar plate designs are recommended for further study. This work not only reviews membrane electrode assembly manufacturing options and synthesis processes for many of the membranes and for the gas diffusion layers but also adds to the bipolar plate fabrication options described in the literature. This work is intended to facilitate material and process selection through the consideration of the variety of design and manufacturing alternatives propr to capital investment for wide-scale production. 

10. Numerical optimization of channel to land width ratio for PEM fuel cell

Mohammad Ziauddin Chowdhury a b, Omer Genc a b, Serkan Toros a b

a Nigde Omer Halisdemir University Prof. Dr. T. Nejat Veziroglu Clean Energy Research Center, Nigde, Turkey

b  Mechanical Engineering Department, Faculty of Engineering, Nigde Omer Halisdemir University, Nigde, Turkey

Flow field plays a vital role in proton exchange membrane (PEM) fuel cell where channel geometry being the primary factor. Most of the channel geometry analyses were limited to few number of case studies, whereas in this study total 73 case studies were analyzed for the optimization of channel and land width. A three dimensional isothermal single phase flow mathematical model is developed and further validated with experimental study to optimize the channel and land width through parametric sweep function for a staggering 73 number of case studies. The optimization analyses are carried out for a straight channel geometry considering a fixed operating voltage of 0.4 V and channel depth of 1.0 mm. Due to the large number of case studies, the analyzed performance parameters i.e. current density and pressure drop are easily understandable for the change in different channel and land width. The numerical results predicted that the pressure drop is more dependent on channel width compare to the land width and anode pressure drop is less significant than cathode pressure drop. However, both channel and land width have an equal importance on the cell current density. Considering channel pressure drop and current density, the optimization analyses showed that the channel to land width of 1.0 mm/1.0 mm would be best suitable for PEMFC channel geometry. 

9. Crossover effects of the land/channel width ratio of bipolar plates in polymer electrolyte membrane fuel cells

Aeri Jung a, Im Mo Kong a, Kyung Don Baik b, Min Soo Kim a

a Division of WCU Multiscale Mechanical Design, Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Republic of Korea

bAgency for Defense Development, Daejeon 305-152, Republic of Korea

The crossover effect of the land/channel width ratio of bipolar plates in polymer electrolyte membrane fuel cells is experimentally investigated in this study. To isolate the effect of the land/channel width ratio, three different types of bipolar plates of a fixed sum and channel width are specially prepared. With three different bipolar plates, measurements are taken of electrochemical performance, inlet pressure, and hydrogen crossover rate. When the stoichiometric ratio of hydrogen is 1.5, the standard type of bipolar plate, BP2 (land width = 0.75 mm, channel width = 1.05 mm) show the best performance. However, according to increasing stoichiometric ratio of hydrogen, BP3 (land width = 1.12 mm, channel width = 0.68 mm) has the best performance, especially at the medium and high current range. For the crossover rate, the biggest amount of hydrogen gas crossover to the cathode in BP3. This is because of the anode inlet pressure caused by the largest land/channel ratio of BP3. 

8. Design optimization of proton exchange membrane fuel cell bipolar plate

Tabbi Wilberforce a, A.G. Olabi b d, Domenico Monopoli a, M. Dassisti c, Enas Taha Sayed e, Mohammad Ali Abdelkareem b d e

a College of Engineering and Physical Sciences, Department of Mechanical, Biomedical and Design Engineering, Aston University, Birmingham B4 7ET, UK

b Sustainable Energy & Power Systems Research Centre, RISE, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates

c Politecnico di Bari, DMM, Bari, Italy

d Center for Advanced Materials Research, University of Sharjah, 27272 Sharjah, United Arab Emirates

e Chemical Engineering Department, Faculty of Engineering, Minia University, Egypt

The bipolar plate geometry design is one of the fuel cell's key features that determines the cell's power. It equally has a direct correlation to the thermal and water management of the cell as it tends to regulate the amount of by-product water that can be expunged from the fuel cell. This study, therefore, explored the development of novel bipolar plate geometry designs, namely the square baffled channel, the rectangular baffled channel, the parallel channel design, and the double serpentine geometry design. This was further compared with the traditional serpentine design to ascertain the design with the optimum fuel cell performance. With the squared baffled channel presenting the best results, varying operating conditions that will influence the performance of the novel fuel cell channel design were also evaluated. It was observed that the hydrogen mass fraction increased by 22.6% for the square baffled channel design compared with the other geometry designs considered in the present study. The square baffle channel showed 12.11% increase in power density and 14.54% increase in current density compared to the rectangular baffle channel. In terms of the parallel channel design, the square baffle showed 18.941% increase in power density and 22.278% increase in current density. The least performing channel geometry design was the double serpentine design. Comparing the double serpentine channel geometry design to the square baffle channel geometry design, there was an increase in current density by 67.72% and 77.88% in terms of power density in favour of the square baffle channel geometry design. The square baffle channel also showed 50% increase in current density and 58.23% increase in power density compared to conventional serpentine channel flow plate geometry design. An adaptive neuro fuzzy inference system (ANFIS) was also adopted to predict the output power of the cell. This was then compared with Feed Forward Back Propagation Neural Network to determine the model with the most accurate results. The adaptive neuro-fuzzy inference model accurately predicted the non-linearities associated with fuel cell performance, hence recommended as ideal for Proton Exchange membrane fuel cell prediction. The main contribution for the study is the development of optimal flow plate geometry design that will ensure maximum fuel cell performance. The current study is aimed at providing technical information to policy makers and the fuel cell industry on how optimization of the flow plate design via the introduction of baffles could increase the cell performance hence accelerates its commercialization and widen their applications in various sectors beyond the automotive industry. 

7. Mass transfer enhancement of PEM fuel cells with optimized flow channel dimensions

Weitong Pan a, Xueli Chen a, Fuchen Wang a, Gance Dai b

a Institute of Clean Coal Technology, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China

b State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China

A comprehensive understanding of gas channel (GC)-gas diffusion layer (GDL) interrelations incorporating the mass transfer coefficients, resistances, and areas provides guidelines for the flow channel design. This paper is based on the “flow field analysis scheme” that combines theoretical analysis and numerical simulation. In the analysis, transport-reaction interactions are clarified using multiple resistances in series approach. Results indicate that the external mass transfer resistance is primarily confined to the GDL; and instead, the GC-GDL interface should be highlighted for a uniform transport flux. It is further revealed that the reconciliation of the mass transfer area and coefficient is the key to enhanced transport capability. On this basis, the analytical solution of optimal channel width is obtained; and its coordination with the flow rate is established. Next, a typical single-channel fuel cell model is investigated with various geometric and operating parameters, further validating and quantifying the theoretical analysis. 

6. Picosecond laser cutting and drilling of thin flex glass

Krystian L. Wlodarczyk a, Adam Brunton b, Phil Rumsby b, Duncan P. Hand a

a Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom

b M-Solv Ltd., Oxonian Park, Landford Locks, Kidlington, Oxford OX5 1FP, United Kingdom

We investigate the feasibility of cutting and drilling thin flex glass (TFG) substrates using a picosecond laser operating at wavelengths of 1030 nm, 515 nm and 343 nm. 50 μm and 100 μm thick AF32®Eco Thin Glass (Schott AG) sheets are used. The laser processing parameters such as the wavelength, pulse energy, pulse repetition frequency, scan speed and the number of laser passes which are necessary to perform through a cut or to drill a borehole in the TFG substrate are studied in detail. Our results show that the highest effective cutting speeds (220 mm/s for a 50 μm thick TFG substrate and 74 mm/s for a 100 μm thick TFG substrate) are obtained with the 1030 nm wavelength, whereas the 343 nm wavelength provides the best quality cuts. The 515 nm wavelength, meanwhile, can be used to provide relatively good laser cut quality with heat affected zones (HAZ) of <25 μm for 50 μm TFG and <40 μm for 100 μm TFG with cutting speeds of 100 mm/s and 28.5 mm/s, respectively. The 343 nm and 515 nm wavelengths can also be used for drilling micro-holes (with inlet diameters of ⩽75 µm) in the 100 μm TFG substrate with speeds of up to 2 holes per second (using 343 nm) and 8 holes per second (using 515 nm). Optical microscope and SEM images of the cuts and micro-holes are presented. 

5. Laser-perforated anode gas diffusion layers for direct methanol fuel cells  

Abdullah Alrashidi, Hongtan Liu

Clean Energy Research Institute, Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL 33146, USA

Novel anode gas diffusion layers (AGDLs) with both hydrophobic and hydrophilic pathways are created to enhance transfer of both methanol and CO2. Such AGDLs are created by perforating PTFE-treated AGDLs with laser, so that the original pores/pathways in the AGDL are hydrophobic and the laser perforations are hydrophilic, thus providing easy transport paths for both the liquid methanol solution and CO2. One of the novel AGDLs has increased the cell performance by 32% over the non-perforated AGDL. Results of electrochemical impedance spectroscopy (EIS) show that the main reason for the performance enhancement is due to the reduction in mass transfer resistance. Additionally, there is a reduction in charge transfer resistances due to the enhanced methanol transfer to the catalyst layer. The results of linear sweep voltammetry (LSV) show that the perforations increase methanol crossover, thus if perforation density of the AGDL is too high, the cell performances are lower than that of the virgin AGDL.

4. Ablation characteristics and material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers 

HUALU WANG, 1,2 QIULING WEN, 1,2,* XIPENG XU, 1,2 JING LU, 1,2 FENG JIANG, 1,2 AND CHANGCAI CUI1,2 

1 Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China 

2 Fujian Engineering Research Center of Intelligent Manufacturing for Brittle Materials, Huaqiao University, Xiamen 361021, China 

The microstructures on a diamond surface have attracted extensive attention in microelectronics, ultra-precision machining tools, and optical elements, etc. In this work, microgrooves were fabricated on a single-crystal diamond surface using ultraviolet nanosecond or infrared picosecond laser pulses. The surface and internal morphologies of the microgrooves were characterized. The chemical composition and phase transition of the diamond after laser irradiation were analyzed. Furthermore, the ablation threshold, ablation rate, and material removal rate of the diamond processed by nanosecond or picosecond lasers were also calculated. In addition, the temperature distributions of the diamond ablated by nanosecond or picosecond lasers were simulated. Finally, the material removal mechanisms of a single-crystal diamond processed by nanosecond or picosecond lasers were revealed. This work is expected helpful to provide a guidance for the laser fabrication of microstructures on diamond. 

3. Development of bipolar plates with different flow channel configurations for fuel cells

Rajesh Boddu, Uday Kumar Marupakula, Benjamin Summers, Pradip Majumdar

Department of Mechanical Engineering, Northern Illinois University, DeKalb, IL 60115, USA

Bipolar plates include separate gas flow channels for anode and cathode electrodes of a fuel cell. These gases flow channels supply reactant gasses as well as remove products from the cathode side of the fuel cell. Fluid flow, heat and mass transport processes in these channels have significant effect on fuel cell performance, particularly to the mass transport losses. The design of the bipolar plates should minimize plate thickness for low volume and mass. Additionally, contact faces should provide a high degree of surface uniformity for low thermal and electrical contact resistances. Finally, the flow fields should provide for efficient heat and mass transport processes with reduced pressure drops. In this study, bipolar plates with different serpentine flow channel configurations are analyzed using computational fluid dynamics modeling. Flow characteristics including variation of pressure in the flow channel across the bipolar plate are presented. Pressure drop characteristics for different flow channel designs are compared. Results show that with increased number of parallel channels and smaller sizes, a more effective contact surface area along with decreased pressured drop can be achieved. Correlations of such entrance region coefficients will be useful for the PEM fuel cell simulation model to evaluate the affects of the bipolar plate design on mass transfer loss and hence on the total current and power density of the fuel cell.

2. Laser micro-milling of microchannel on copper sheet as catalyst support used in microreactor for hydrogen production

Wei Zhou a, Wenjun Deng b, Longsheng Lu b, Junpeng Zhang a, Lifeng Qin a, Shenglin Ma a, Yong Tang b

a Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China

b School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

Microchannel structure as catalyst support has been widely used to construct numerous microreactors for hydrogen production. In this work, the laser micro-milling technique was introduced into the fabrication process of microchannels with different geometry and dimensions. The effects of varying scanning speed, laser output power and number of scans on the surface morphology and geometrical dimension of microchannels have been investigated based on SEM observations. It is found that the change of scanning speed and laser output power significantly affected the surface morphology of microchannel. Moreover, the depth of microchannel was increased when the laser output power and number of scans were increased. Subsequently, the microchannels on copper sheet fabricated by the laser micro-milling technique were used as catalyst support to conduct the methanol steam reforming reaction. The better reaction performance of methanol steam reforming in microchannels indicates that laser micro-milling process is probably suitable to fabricate the microchannel reactor for the commercial application.

1. Optimizing operating parameters of a honeycomb zeolite rotor concentrator for processing TFT-LCD volatile organic compounds with competitive adsorption characteristics

Yu-Chih Lin a, Feng-Tang Chang b c

a Department of Environmental Engineering and Health, Yuanpei University, 306 Yuan-Pei Street, Hsin-Chu City 300, Taiwan

b JG Environmental Technology Co., Ltd., 3F, No. 70, Guangming 1st Road, Shihsing Village, Jhubei City, Hsinchu county 302, Taiwan

c College of Engineering, National Chiao Tung University, Taiwan

In this study, the authors attempted to enhance the removal efficiency of a honeycomb zeolite rotor concentrator (HZRC), operated at optimal parameters, for processing TFT-LCD volatile organic compounds (VOCs) with competitive adsorption characteristics. The results indicated that when the HZRC processed a VOCs stream of mixed compounds, compounds with a high boiling point take precedence in the adsorption process. In addition, existing compounds with a lowboiling point adsorbed onto the HZRCwere also displaced by the high-boiling-point compounds. In order to achieve optimal operating parameters for high VOCs removal efficiency, results suggested controlling the inlet velocity to <1.5 m/s, reducing the concentration ratio to 8 times, increasing the desorption temperature to 200–225 ◦C, and setting the rotation speed to 6.5 rpm.

50. Effect of laser remelting and ultrasonic irradiation on crack suppression and properties of Ni-WC laser cladding layer 

Haifeng Zhang, HuaiChen Guo, Xiaoping Hu, JiYuan Tao, WenHan She, Changlong Zhao * 

School of Mechanical and Vehicle Engineering, Changchun University, Changchun 130022, Jilin

Natural Science Foundation of Jilin Province (No. YDZJ202501ZYTS395) , Scientific Research  Education Department of Jilin Province (No. JJKH20251089CY) .

The objective of this study was to examine the impact of two assisted laser cladding processes, namely laser remelting and ultrasonic irradiation, on the properties and crack susceptibility of Ni60-WC laser cladding layers on C45E4 steel substrates. The experimental configuration entailed the implementation of facilitated metal matrix ceramic composite fused cladding layer preparation processes by laser remelting and laser cladding, employing a custom-designed ultrasonic irradiation device that was developed in-house. A range of analytical instruments, including an optical digital microscope, a scanning electron microscope, a Vickers microhardness tester, an X-ray diffractometer (XRD), a friction and wear tester, and a three-dimensional optical profilometer, were used to investigate the surface cracking, microstructure, hardness, abrasion resistance, and wear surface morphology of the fused cladding. The experimental findings demonstrated that ultrasonic waves significantly enhanced the crystal strengthening effect of the fused cladding, resulting in a 23.08% decrease in wear resistance. Furthermore, the combined laser remelting and ultrasonic-assisted process effectively prevented the formation of cracks in the laser-melted cladding layer and enhanced the hardness of the fused cladding substrate. Notably, despite the occurrence of partial melting of WC particles during the laser remelting process, the hardness of the cladding layer prepared by these assisted processes exhibited an enhancement of 17.54%, and the wear resistance was found to be comparable to that of the conventional cladding layer.