Developing New Ultrahigh Thermal Conductivity Materials

Yongjie Hu, Assistant Professor
Mechanical and Aerospace Engineering Department, UCLA

Heat dissipation has become an increasingly important technological challenge in modern electronics and energy technologies. Discovering new high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. In this talk, I will describe our recent progress in developing emerging high thermal conductivity semiconductors including boron arsenide (BAs) and boron phosphide (BP). For the first time, we synthesized BAs and BP single crystals without detectable defects, and measured a room temperature thermal conductivity of 1300 W/mK (Science 361, 575, 2018) and 500 W/mK (Nano Letters 17, 7507, 2017) respectively. Our ultrafast spectroscopy study in conjunction with atomistic theory reveals that the unique band structure of BAs allows for very long phonon mean free paths and strong high-order anharmonicity through the four-phonon process. The single-crystal BAs has the highest thermal properties among all common metals and semiconductors. Our study establishes BAs and BP as new benchmark materials for thermal management applications, and exemplifies the power of combining experiments and ab initio theory in new materials discovery. In addition, I will briefly describe new in-situ techniques recently developed in my group that enable better fundamental understanding of phonon spectra and control of nanoscale energy transport for applications in batteries, sensors, and thermoelectrics.

About the Speaker

Yongjie Hu is an Assistant Professor of Mechanical and Aerospace Engineering at UCLA. His group exploits a variety of interdisciplinary experimental and theoretical approaches to investigate nanoscale transport processes, with a current emphasis on developing advanced thermal materials and experimental metrologies to characterize transport mechanisms. Before joining the faculty of UCLA, he received his Ph.D. from Harvard University and Battelle Fellowship from MIT. His research has been recognized by diverse research societies, including NSF CAREER Award and Air Force Young Investigator Award.