Titanium and its alloys are widely used as implant materials for biomedical devices owing to their high mechanical strength, biocompatibility, and corrosion resistance. However, there is a significant rise in implant-associated infections (IAIs) leading to revision surgeries, which are more complicated than the original replacement surgery. To reduce the risk of infections, numerous antibacterial agents, e.g., bioactive compounds, metal ions, nanoparticles, antimicrobial peptides, polymers, etc., have been incorporated on the surface of the titanium implant. Various coating methods and surface modification techniques, e.g., micro-arc oxidation (MAO), layer-by-layer (LbL) assembly, plasma electrolytic oxidation (PEO), anodization, magnetron sputtering, and spin coating, are exploited in the race to create a biocompatible, antibacterial titanium implant surface that can simultaneously promote tissue integration around the implant. The nature and surface morphology of implant coatings play an important role in bacterial inhibition and drug delivery. Surface modification of titanium implants with nanostructured materials, such as titanium nanotubes, enhances bone regeneration. Antimicrobial peptides loaded with antibiotics help to achieve sustained drug release and reduce the risk of antibiotic resistance. Additive manufacturing of patient-specific porous titanium implants will have a clear future direction in the development of antimicrobial titanium implants. In this review, a brief overview of the different types of coatings that are used to prevent implant-associated infections and the applications of 3D printing in the development of antibacterial titanium implants is presented.

For NDIs which fractured after being inserted in patients, it can be observed that the fracture mechanism was fatigue in all cases. The fractography can be observed in Figure 3, with different SEM micrographs showing a detailed description of both crack nucleation points and crack propagation paths. Figure 3 shows the presence of many longitudinal cracks along practically all vertices between the walls of the inner hexagonal connection [25,26,27].


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SEM fractography of explanted cp-Ti grade 4 NDIs: (a) SEM micrograph of an explanted implant, top view; (b) SEM micrograph of hexagonal inner connection (side view) showing longitudinal fracture cracks; the white arrows mark the places of crack nucleation; (c,d) SEM micrographs showing crack propagation at different magnifications.

SEM micrographs of the cpTi grade 4 NDI showing crack nucleation and propagation: (a) SEM micrograph showing crack nucleation starting point, (b) SEM micrograph showing crack cyclic propagation due to fatigue.

Initially, static uniaxial compression tension tests were conducted in order to determine the yield strength of the material, the ultimate strength, and the strain to fracture. The hardness of the specimens was measured on polished cross-sections using a Vickers microhardness tester (Akashi, Matsusawa, Japan) with a Vickers diamond indenter under a load of 0.98 N (100 gf) and 15 s of indentation. Fifteen data points were collected and averaged for each hardness value. Ten implants were analyzed for static tension, and the same number was used for hardness testing (n = 10).

This work investigates the micro-milling machinability of Ti-6Al-4V alloy produced by a Laser Engineered Net Shaping (LENS) additive manufacturing (AM) process with a specific focus on surface quality, cutting forces and burr formation. The effects of additive deposition parameters are also investigated since the material thermal history during processing can affect porosity and mechanical behavior of the samples, giving different milling performances. The material characterization of samples is done through micrographies, hardness tests and porosity evaluation. The roughness of the machined surfaces shows a statistical distinction between the AM and wrought titanium samples. Similar behavior is seen with the cutting forces, which increase with an increase of hardness of the AM samples. The results also show an increased trend towards burr formation in case of down milling of AM samples compared to wrought titanium samples. The future prospective is to take into account the machinability properties as functional material characteristics to optimize through the deposition process.

N2 - This work investigates the micro-milling machinability of Ti-6Al-4V alloy produced by a Laser Engineered Net Shaping (LENS) additive manufacturing (AM) process with a specific focus on surface quality, cutting forces and burr formation. The effects of additive deposition parameters are also investigated since the material thermal history during processing can affect porosity and mechanical behavior of the samples, giving different milling performances. The material characterization of samples is done through micrographies, hardness tests and porosity evaluation. The roughness of the machined surfaces shows a statistical distinction between the AM and wrought titanium samples. Similar behavior is seen with the cutting forces, which increase with an increase of hardness of the AM samples. The results also show an increased trend towards burr formation in case of down milling of AM samples compared to wrought titanium samples. The future prospective is to take into account the machinability properties as functional material characteristics to optimize through the deposition process.

AB - This work investigates the micro-milling machinability of Ti-6Al-4V alloy produced by a Laser Engineered Net Shaping (LENS) additive manufacturing (AM) process with a specific focus on surface quality, cutting forces and burr formation. The effects of additive deposition parameters are also investigated since the material thermal history during processing can affect porosity and mechanical behavior of the samples, giving different milling performances. The material characterization of samples is done through micrographies, hardness tests and porosity evaluation. The roughness of the machined surfaces shows a statistical distinction between the AM and wrought titanium samples. Similar behavior is seen with the cutting forces, which increase with an increase of hardness of the AM samples. The results also show an increased trend towards burr formation in case of down milling of AM samples compared to wrought titanium samples. The future prospective is to take into account the machinability properties as functional material characteristics to optimize through the deposition process.

Abstract: In this paper, two mathematical models based on heat transfer principle have been developed for the simulation of single resistance-capacitance pulse discharge in micro electric discharge machining of Ti-6Al-4V. Models are solved using finite volume as well as finite element methods in order to predict the size and shape of the single spark crater. It calculates the temperature distribution in the work piece and thereby predicts the size and shape of the single spark crater. The developed models were compared each other with the same operating parameters and assumptions. The trend predicted by the models were found to be same and in good agreement with a variation less than 6%. In order to validate the developed models, the crater shape from the predicted temperature of the models were calculated and compared with the experimental results. It was observed that both the models are in good agreement in predicting the crater shape.

Abstract: The interest on micro cutting processes is proved by the attention of industries on this topic. This trend moves the researches on micro cutting toward different aspects. A modelling procedure for forecasting cutting forces in microcutting, considering all phenomena involved in micro scale, can be of interest for industries allowing the evaluation of process quality. This paper deals with modelling of cutting forces in micromilling operations of channels. The proposed procedure is a combination of a force model based on specific cutting pressure and instantaneous chip section, estimated considering the tool run-out contribution, an optimisation strategy (particles swarm optimisation), and data coming from experimental tests realised on a sample of titanium alloy (Ti6Al4V). The comparisons between experimental and analytical data, and the evaluation of the uncertainty of the calibrated model show the good ability of the proposed procedure for defining analytical model for force prediction in channels micromilling.

To research the relationship of micro-structures and antibacterial properties of the titanium-doped ZnO powders and probe their antibacterial mechanism, titanium-doped ZnO powders with different shapes and sizes were prepared from different zinc salts by alcohothermal method. The ZnO powders were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), and the antibacterial activities of titanium-doped ZnO powders on Escherichia coli and Staphylococcus aureus were evaluated. Furthermore, the tested strains were characterized by SEM, and the electrical conductance variation trend of the bacterial suspension was characterized. The results indicate that the morphologies of the powders are different due to preparation from different zinc salts. The XRD results manifest that the samples synthesized from zinc acetate, zinc nitrate, and zinc chloride are zincite ZnO, and the sample synthesized from zinc sulfate is the mixture of ZnO, ZnTiO3, and ZnSO4  3Zn (OH)2 crystal. UV-vis spectra show that the absorption edges of the titanium-doped ZnO powders are red shifted to more than 400 nm which are prepared from zinc acetate, zinc nitrate, and zinc chloride. The antibacterial activity of titanium-doped ZnO powders synthesized from zinc chloride is optimal, and its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are lower than 0.25 g L-1. Likewise, when the bacteria are treated by ZnO powders synthesized from zinc chloride, the bacterial cells are damaged most seriously, and the electrical conductance increment of bacterial suspension is slightly high. It can be inferred that the antibacterial properties of the titanium-doped ZnO powders are relevant to the microstructure, particle size, and the crystal. The powders can damage the cell walls; thus, the electrolyte is leaked from cells. be457b7860

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