Jian Luo

Jian Luo, University of California, San Diego

From Ultrafast Sintering to Controlling Microstructures with Electric Fields

Abstract
This talk will first review a series of mechanistic studies of flash sintering [Scripta Mater. 146:260 (2018)]. In 2015, we reported that flash sintering generally starts as a thermal runaway [Acta Mater. 94:87 (2015)], along with other independent studies. In 2017, we further reported a mechanistic study to suggest ultrahigh heating rates as the key factor in enabling ultrafast sintering by demonstrating that similar densification rates can be achieved for ZnO via (1) flash sintering and (2) rapid thermal annealing (intense infrared heating without an electric field) with similar heating rates of ~200 K/s [Acta Mater. 125:465 (2017)]. A similar conclusion was also obtained by Professor Richard Todd and co-workers via an independent “ultra-fast firing” study of YSZ [JECS 37:2547 (2017)]. Subsequently, general ultrafast sintering methods, enabled by the same underlying mechanism, were demonstrated in collaborative studies [e.g., Science 368:521 (2020) and Nature 623:964 (2023)]. Although we have demonstrated that ultrafast sintering can be achieved without an electric field, we recognize that electric fields can influence microstructural evolution. For example, we discovered an electrochemically induced grain boundary disorder-to-order transition to trigger abnormal grain growth in Bi2O3-doped ZnO [Nature Communications 12:2374 (2021)]. Moreover, combined aberration-corrected electron microscopy and ab initio molecular dynamics simulations showed that applied electric fields can induce grain boundary oxidation transitions near the anode to create continuously graded microstructures in undoped ZnO [Materials Today 73:66 (2024)]. Several ongoing projects and unpublished results will also be discussed.

Biography
Jian Luo is a Professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the University of California, San Diego (UCSD). He graduated from Tsinghua University with dual Bachelor’s degrees: one in Materials Science and Engineering and another in Electronics and Computer Technology. After receiving his M.S. and Ph.D. degrees from M.I.T., Luo worked in the industry for over two years with Lucent Technologies Bell Laboratories, and OFS. In 2003, he joined the Clemson University 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 Nano Engineering and Professor of Materials Science and Engineering. Luo group’s current research focuses on interfaces in ceramics and metals, high-entropy and compositionally complex ceramics, ultrafast sintering and other novel ceramic processing technologies, high-temperature nanocrystalline alloys, and advanced materials for batteries and other energy-related applications. Luo authored and co-authored >220 articles in reputable journals, including Journal of the European Ceramics Society (15), Acta Materialia (21), Scripta Materialia (21), Science (6), Nature (3), and Physical Review Letters (2). His citations in Google Scholar exceed 3000 per year in 2024. Luo received a National Science Foundation CAREER award in 2005 (from the Ceramics program) and an AFOSR Young Investigator award in 2007 (from the Metallic Materials program). He was a Vannevar Bush Faculty Fellow (2014) and a Minerals, Metals & Materials Society (TMS) Brimacombe Medalist (2019). Luo is a Fellow of the American Ceramic Society (2016), a Fellow of the ASM International (2022), and an Academician of the World Academy of Ceramics (2021). Luo has served as the Chair for the Basic Science Division of the American Ceramic Society (2012-2013), the TMS Thin Films and Interfaces Committee (2012-2014), and the Solid Studies of Ceramics Gordon Research Conference (2018), and he co-organized nearly 60 symposia at various international conferences.