清華大學材料科學與工程研究院《材料科學論壇》

學術報告

題目：Grain boundary mobility control: A case study in zirconia ceramics

報告人：Yanhao Dong （Department of Nuclear Science and Engineering,Massachusetts Institute of Technology）

時間：2018年5月17日（星期四） 上午9:30

地點：清華大學逸夫技術科學樓A205房間

聯系人：汪長安老師 62785488

報告摘要：
Competition between densification and coarsening is the key issue in ceramic sintering, which requires a rational design of grain boundary mobility within the applicable processing window. Using zirconia as a model system, we demonstrate a facile control of grain boundary mobility over orders of magnitude, via conventional state variables including temperature, atmosphere and electric field. Specifically, >1,000 times enhanced mobility can be obtained by (electro-)chemical reduction, indicating greatly accelerated cation diffusion by cation reduction and novel electron-phonon interactions on ion dynamics as proved by first-principles simulations. On the other hand, a rapid mobility quench has been observed in cubic zirconia, suppressing grain growth kinetics and enabling two-step sintering to fabricate nano-grain ceramics. A generalized mean-field growth theory echoes with our observations, addressing a critical role of multi-grain junctions which were previously unaware of. To conclude, we believe there is plenty of room in ceramic’s processing and microstructural control, where mechanistic understandings from continuum to atomistic scale are of vital importance.

報告人簡介：
Yanhao Dong is now a postdoctoral researcher at the Massachusetts Institute of Technology. He obtained his BS degree in materials science in 2012 from Tsinghua University, and his MS degree in materials science in 2014, his MS degree in applied mechanics in 2015, and his PhD degree in material science in 2017, all from the University of Pennsylvania. His PhD dissertation focused on cation diffusion in zirconia ceramics, covering from phenomenological sintering and grain growth experiments to continuum-level solution of transport and growth theory to atomistic simulation of defect energetics and kinetics. He received the inaugural Global Distinguished Doctoral Dissertation Award from the American Ceramic Society, Best Paper Award from Journal of the American Ceramic Society and Outstanding Reviewers Award from Scripta Materialia. His current research interest is on ceramics and functional oxides for energy application.

董岩皓，現任美國麻省理工學院博士後。2008-2012年，在清華大學材料科學與工程系學習，獲得學士學位。2012-2017年，在美國賓夕法尼亞大學學習，獲得材料學碩士、應用力學碩士和材料學博士學位。他在博士論文工作中，采用實驗（陶瓷燒結、晶粒生長和電場輔助擴散）、理論（連續體平均場理論下的物質傳輸和晶粒生長）與原子尺度模拟（缺陷的形成能和動力學）相結合的方法，系統研究了氧化锆陶瓷中金屬陽離子的擴散現象與機理。他獲得了美國陶瓷學會頒發的首屆優秀博士生論文獎（Global Distinguished Doctoral Dissertation Award），美國陶瓷學會會志頒發的最佳論文獎和Scripta Materialia雜志頒發的最佳審稿人獎。他現階段的主要研究方向是陶瓷和氧化物材料在能源方面的應用。