学科建设
微电论坛(第596期)
发布于:2016-10-24 11:22:36   |   作者:[学院] 微固学院   |   浏览次数:2320
时间:2016年10月26日(周三)上午10:30
地址:沙河校区微固楼420会议室
主办:微电子与固体电子学院
承办:研究生院
范围:院内

题 目: Brittle Failure of Boron Carbide and Related Materials from Atomistic Simulations; Strategy to Improve Ductility

主讲人: Qi An Assistant Professor

主持人: 唐斌 教授

  介:

Qi An is an assistant professor in Chemical & Materials Engineering Department at University of Nevada, Reno (UNR). He joined UNR in July 2016. Before then, he was a postdoctoral scholar in the Division of Chemistry and Chemical Engineering at California Institute of Technology (Caltech). Qi An received his B.S. from University of Science and Technology of China, and his Ph.D. in Materials Science from Caltech in 2012. His research area is computational materials science. His research specifically focuses on material properties under extreme conditions; deformation and failure mechanism of superhard ceramics, metallic glasses, metals, and thermoelectric materials; detonation and sensitivity of energetic materials; and surface chemistry.He has authored or co-authoredover 60 publications in the peer-review scientific journals including Science, Physical Review Letters, Nature Communications, Proceedings of the National Academy of Science, Nano Letters, etc.

Ceramics such as boron carbide (B4C) are strong but too brittle for extended applications. The development of B4C based materials with improved properties is prevented by their complex bonding conditions and their relationships to the macroscale mechanical properties. In this talk we will discuss the deformation and brittle failure mechanism of B4C from atomistic simulations. We first identified a unique deformation path shearing along the most plausible slip system in which a boron-carbon bond between neighboring icosahedral clusters breaks to form a carbon lone pair (Lewis base) on the C within the icosahedron. Further shear then leads this Lewis base C to form a new bond with the Lewis acidic B in the middle of a CBC chain. This initiates destruction of this icosahedron, resulting in amorphous structure.Then we performed large-scale reactive-molecular-dynamics simulations on shear deformations of B4C and found that brittlefailure in B4C arises from formation of higher density amorphous bands due to fracture of the icosahedra. This leads to negative pressure and cavitation resulting incrack opening. Furthermore we will discuss the nano-twins in B4C, boron suboxide (B6O) and β-B, and their effects on the structural and mechanical properties. Finally we will discuss the microalloying strategies to improve theductility of B4C by avoiding the icosahedral fracture.


Welcome to attend!

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