University of California, San Diego
Decoding the Materials Genome via Comprehending "2-D Interfacial Phases"
Location: EB1 Room 3003
Friday, September 16th 2016 - 2:00 pm
Abstract A piece of ice melts at 0 °C, but a nanometer-thick surface layer of the ice can melt at tens of degrees below zero. This phenomenon, known as "premelting," was first recognized by the physicist Michael Faraday. Materials scientists have discovered that the surfaces and interfaces in engineered materials can exhibit more complex phase-like behaviors at high temperatures, which can affect the fabrication and properties of a broad range of metallic alloys and ceramic materials. Specifically, recent studies of 2-D grain-boundary (GB) phases (also called "complexions") shed light on several long-standing mysteries in materials science, including the origins and atomic-level mechanisms of activated sintering, liquid metal embrittlement, and abnormal grain growth. Since bulk phase diagrams are one of the most useful tools for materials design, it is conceived that interfacial "phase" diagrams can be developed as a generally-useful materials science tool, in support of the Materials Genome Initiative.
Our recent efforts include (a) combining a genetic algorithm with hybrid Monte Carlo and molecular dynamics simulation to reveal the atomistic detail of GB phase-like transformation, (b) stabilizing nanocrystalline alloys at high temperatures using high-entropy GB complexions, and (c) utilizing analogous 2-D surface phases to improve the performance of batteries, supercapacitors, photocatalysts, and nanowire-based oxygen-ion conductors.
If time permits, I will also briefly discuss our recent studies on understanding the mechanisms of flash sintering, where we have (1) theoretically developed a model to reveal the flash mechanism and predict onset flash temperature with a precision of ≤ ±6 °C and (2) practically achieved, e.g., the sintering of ZnO to >97% density at an extremely low furnace temperature of < 120 °C in ~30 seconds.
Bio: Jian Luo graduated from Tsinghua University with dual Bachelor's degrees. After receiving his M.S. and Ph.D. degrees from M.I.T., Luo worked in the industry for more than two years with Lucent Technologies and OFS/Fitel. In 2003, he joined the Clemson faculty, where he served as an Assistant/Associate/Full Professor of Materials Science and Engineering. In 2013, he moved to UCSD as a Professor of NanoEngineering and Professor of Materials Science and Engineering. He received a National Science Foundation CAREER award in 2005 (from the ceramics program) and an Air Force Office of Scientific Research Young Investigator award in 2007 (from the metallic materials program). Luo was named as a National Security Science and Engineering Faculty Fellow in 2014 and elected as a Fellow of the American Ceramic Society in 2016.