SEMINAR
The State Key Lab of
High Performance Ceramics and Superfine Microstructure
Shanghai Institute of Ceramics, Chinese Academy of Sciences
中 国 科 学 院 上 海 硅 酸 盐 研 究 所 高 性 能 陶 瓷 和 超 微 结 构 国 家 重 点 实 验 室
Solute concentrations and strains in nanograined materials and nanoparticles

　　张统一 院士

　　香港科技大学

　　时间：2015年1月15日（星期四）上午 9:30

　　地点：4号楼14楼第一会议室

　　联系人：陈立东 4804

　　报告摘要：

　　In this presentation, we report a newly developed Gibbs-approach based adsorption isotherm for interface (including grain boundary and surface) segregation in nanograined polycrystals and nanoparticles. An excess interface thickness was introduced to describe the excess of interface atomic volume in comparison with the atomic volume in lattice. The interface bulk modulus was then determined with the excess interface thickness and a universal function. The newly developed adsorption isotherm is able to analyze simultaneously stresses, concentrations and their coupling behaviors in lattice and interface. The thermodynamic analysis shows that the apparent solute concentration is greatly enhanced in nanomaterials due to two factors. The first one is the large interface volume fraction in nanomaterials and interface segregation. The second is due to a considerable increase in the lattice concentration that is boosted by the concentration-induced stresses. The difference of concentration in lattice and interface changes the stress on lattice from compressive to tensile and thus enhances the concentration in lattice. The theoretical predictions have been verified by experimental data reported in the literature for H-Pd system. With the measured lattice strain and sample strain of the nanograined Pd, with an averaged grain size of 10 nm, versus the hydrogen gas partial pressure, we determined H concentrations and stresses in grains and grain boundaries and the intrinsic properties of grain boundaries, such as the grain boundary bulk modulus, the grain boundary excess thickness, the difference in chemical potential between grains and grain boundaries, etc. Applying the Gibbs-approach based adsorption isotherm to the experimental data of nominal H concentration in Pd nanoparticles, with a mean diameter of 3.6 nm, versus H2 partial pressure, we determined the H-trap depth of Pd surface, the H concentrations and stresses in both core and surface shell of the nanoparticles. The developed Gibbs-approach based adsorption isotherm is able to be applied to other material systems.

　　报告人简介：

　　张统一院士，1985年在北京钢铁学院获博士学位、师从肖纪美院士。现任香港科技大学讲座教授及方氏工程学教授，上海大学材料基因组工程研究院院长，材料科学和固体力学专家。兼任远东及大洋洲断裂协会副主席、国际断裂协会副主席。2011年当选为中国科学院院士。研究领域包括材料的力学性能、微观力学/纳米力学、微结构与材料性能的关系、铁电和压电材料、薄膜、纳米线及纳米管、微桥/纳米桥实验、扩散与相变、多场耦合下的材料行为。

　　以第一作者及联合作者身份共发表200多篇SCI学术论文。在断裂力学，微观、纳观力学和材料的氢致开裂等领域取得了多项创新性成果，拥有两项美国专利和两项国家专利，获两次国家自然科学二等奖（1987年度十位获奖人中排第三和2007年度第一获奖人），2013年当选为国际断裂协会Fellow，2012年当选为香港工程院Fellow，2003年获香港裘槎高级研究学者奖，2001年当选为美国ASM International Fellow，1988年获中国科学技术协会青年科技奖。他是中国科学技术学报副主编及（国际）理论和应用断裂力学学报断裂与连续介质力学编辑。