清华大学材料科学与工程研究院《材料科学论坛》

学术报告

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

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

时间：2018年5月17日（星期四） 上午9:30

地点：清华大学逸夫技术科学楼A205房间

联系人：汪长安老师 62785488

报告摘要：
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.

报告人简介：
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，现任美国麻省理工学院博士后。2008-2012年，在清华大学材料科学与工程系学习，获得学士学位。2012-2017年，在美国宾夕法尼亚大学学习，获得材料学硕士、应用力学硕士和材料学博士学位。他在博士论文工作中，采用实验（陶瓷烧结、晶粒生长和电场辅助扩散）、理论（连续体平均场理论下的物质传输和晶粒生长）与原子尺度模拟（缺陷的形成能和动力学）相结合的方法，系统研究了氧化锆陶瓷中金属阳离子的扩散现象与机理。他获得了美国陶瓷学会颁发的首届优秀博士生论文奖（Global Distinguished Doctoral Dissertation Award），美国陶瓷学会会志颁发的最佳论文奖和Scripta Materialia杂志颁发的最佳审稿人奖。他现阶段的主要研究方向是陶瓷和氧化物材料在能源方面的应用。