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Ultra High and Ultra Low Thermal Conductivity Materials
For the ultra high thermal conductivity materials, we will predicatively design, synthesize, characterize, and model unique oxygen-functionalized 2D transition-metal carbides (MXenes) with ultrahigh thermal conductivity. We will also study how to integrate them to existing semiconductor device fabrication process to significantly enhance the heat dissipation for improved cooling and thermal management for future potential applications, including reliable heat spreader in high-power directed energy systems, radar, RF communications, and lasers. The experimental research will be coupled with theoretical modeling to establish the systematic understanding of the thermal transport in these novel 2D materials.
For the ultra low thermal conductivity materials, we will focus on the investigation of the electron critical scattering within a temperature window near the phase transition temperature in certain ultrathin chalcogenide nanowires. We intend to achieve materials with a manipulatable transient temperature range and phase transition speed to maintain the very low thermal conductivity while with little sacrifice in the electrical conductivity.
We are particularly looking at the following materials:
2D MXenes with Ultra High Thermal Conductivity - MXenes are a new family of 2D transition-metal carbides and nitrides, which can be fabricated by selective etching of “A” from MAX phases (Mn+1AXn where M is an early transition metal, A is an A-group element, X is C or N, and n=1, 2, or 3). The as-synthesized MXenes are typically functionalized by -O, -OH and -F groups, which can be denoted as Mn+1XnTx, where T stands for the surface-terminating group. Our preliminary theoretical calculation suggests these oxygen-functionalized MXenes, such as Hf2CO2, could exhibit extremely high in-plane room-temperature thermal conductivity.
Phase Transition in Ultrathin Nanowires - Via size-reduction, we intend to achieve the phase transition temperature increased by more than 100 K. Through doping, the phase transition temperature can be decreased by 50 K or more. This vast transition temperature tunability makes these phase transition materials have broader applications for thermal management and storage. In-situ TEM based structure characterization and the simultaneous thermal and electrical transport characterization during phase transition will help clarify the impact of fluctuations in the sample density, concentration, and structure introduce extra critical electron and phonon scattering.
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