Tian Li
Assistant Professor, Mechanical Engineering, Purdue University
Email: tianli@purdue.edu; mytian1211@gmail.com
Address: 1034 Ray W. Herrick Laboratories, 177 S Russell St, West Lafayette, IN 47907
Our group website:
www.tianliresearch.com
Selected Publications:
Tian Li, et al, "A radiative cooling structural material" Science 364, 6442, (2019)
Tian Li, et al, "Cellulose Ionic Conductors with High Differential Thermal Voltage for Low-Grade Heat Harvesting" Nature Materials, 18, 6 (2019)
Tian Li, et al, "A Nanofluidic Ion Regulation Membrane with Aligned Cellulose Nanofibers" Science Advances, 5, 2, 4238 (2019)
Tian Li, et al, "Thermoelectric Properties and Performance of Flexible Reduced Graphene Oxide Films up to 3000 K" Nature Energy 3, 148–156 (2018).
Tian Li, et al, "Anisotropic, Lightweight, Strong, and Super Thermally Insulating Nanowood with Naturally Aligned Nanocellulose" Science Advances, 4, 3, 3724 (2018)
Selected Awards and Activities
Research Concentration 1: Emerging Cellulose Science and Engineering towards Energy Efficient Infrastructure and Energy-Water Nexus
Cellulose-Water-Energy Nexus
Nanoscale or even sub-nm scale cellulose channels allows for interesting interaction among cellulose, water and ions. As a demonstration, the transport of sodium ions within the molecular chains were demonstrated which was utilized to achieve a high ionic thermoelectric performance (T. Li, et al, Nature Materials 18, 6, 2019).
The dimension of the ion transport channels shows excellent tunability via structural engineering. This opens up an exciting new direction using abundant bio-materials—cellulose for fluidic applications. Taking nanofluidics for example, nanoscale ion channels exhibit among fibrillated cellulose and elementary cellulose fibers with a dimension of 2 nm to 50 nm. Wood with numerously aligned nanoscale channels can thus be used as an ion regulation membrane from which an electrically gated ionic transistor was demonstrated with an exchange of electrical signal and ion signal (T Li, et al, Science Advances 5, 2, 2019).
With the aid of advanced characterization methods including small angle neutron scattering and small angle X-ray scattering as well as fundamental understanding of the process-structure-property-application relationship via molecular engineering, enormous opportunities in a myriad of new directions can be foreseen.
Energy efficient building materials with light and thermal management
Buildings represent the largest energy sector. Building energy efficiency must be considered as a part of our sustainable energy strategy. With innovative functionalization, wood can be made as an extremely attractive energy efficient building material. Several wood technologies were developed including transparent wood, thermal insulation nanowood, and radiative cooling wood.
Taking cooling wood for example, it features an effective back-scattering of sunlight and minimum absorption coefficient for the realization of the sub-ambient radiative cooling, providing a perpetual path to dissipate heat into the universe via the atmospheric transparency window without energy consumption. The cooling wood is directly derived from mesoporous natural wood. The material exhibits continuous cooling effect with a mechanical strength > 400 MPa and a specific tensile strength of 334.2 MPa cm3/g. The high strength is attributed to the physical entanglement of microscale wood cells and the maximized interaction among aligned nanofibers via hydrogen bonding (T. Li, et al, Science, 364, 6442, 2019) .
Research Concentration 2: High temperature synthesis-structure-properties
The high temperature synthesis (up to 3300 K) enabled by joule heating of carbon-based substrate opens a new paradigm of nanomaterials. Many new and exciting scientific discoveries on the correlations between high temperature synthesis-structure-properties await. The development of the ultrahigh-temperature operation of thermoelectrics can open up possible applications in many high-power energy systems. To efficiently convert heat to electricity, a high operating temperature is desirable to ensure a high Carnot efficiency. The thermally-reduced solution-processed graphene oxide at 3300 K is shown to be a highly efficient and reliable thermoelectric material up to 3000 K, which makes it a promising candidate for a broad range of applications including concentrated solar power, radiation energy conversion, thermoelectric topping cycles for power plants, and direct energy generation from hydrocarbon combustion, since our maximum operation temperature exceeds the adiabatic flame temperatures of all common fuels in air (T. Li, et al, Nature Energy 3, 148–156, 2018)
PhD work on Self-Assembled InAs/GaAs/ Quantum Dot Solar Cells and Non-linear Optics
My PhD work focuses on experimental and theoretical studies aimed at establishing the fundamental understanding of the linear and non-linear electrical and optical processes governing the operation of quantum dot solar cells and their feasibility for the realization of intermediate band solar cell.
Uniform performance QD solar cells with high conversion efficiency have been fabricated using carefully calibrated process recipes as the basis of all reliable experimental characterization. We are able to distinguish the nonlinearity effect by 1PA and 2PA process. The observed 2PA current under off-resonant and on-resonant excitation comes from a two-step transition via the tailing states instead of the QD states.
My PhD ~ 5 years experiences in cleanroom fabrication and setting up optoelectronic characterization systems including external quantum efficiency, z-scan, two-photon absorption, automated optical fiber-waveguide coupling stage, et al.
