Solute concentrations and strains in nanograined materials
讲座名称：
Solute concentrations and strains in nanograined materials
讲座时间：
2013-03-27
讲座人：
张统一
形式：
校区：
兴庆校区
实践学分：
讲座内容：
中国科学院院士、香港科技大学张统一教授受聘为西安交通大学名誉教授，2013年3月27日来我校参加受聘仪式，并为我校师生作学术报告。
时间：2013年3月27日（星期三）下午14:30 - 16:30
地点：教一楼南204第五会议室
活动安排：
14:30－14:40 校领导会见
14:40－14:50 仪式开始，王铁军院长介绍张统一教授学术成果及荣誉
14:50－15:10 校领导向张统一教授颁发聘书并讲话
15:10－15:15 张统一教授致谢词
15:15－16:20 张统一教授作学术报告
报告题目：Solute concentrations and strains in nanograined materials
Abstract : Taking advantages from both Gibbs and McLean adsorption isotherms, we developed a Gibbs-approach based adsorption isotherm for grain boundary (GB) segregation in nanograined (ng) polycrystals. An excess GB thickness was introduced to describe the excess of GB atomic volume in comparison with the atomic volume in lattice. The GB bulk modulus was then determined with the excess GB thickness and a universal function. The newly developed adsorption isotherm is able to analyze simultaneously stresses, concentrations and their coupling behaviors in grains and GBs, showing that the apparent solute concentration could be greatly enhanced in ng materials, due to a large grain boundary volume fraction and a considerable increase in the lattice concentration that is, in turn, boosted by the concentration-induced stresses.Using the experimental data of lattice strain and sample strain of the nanograinedPd, with an averaged grain size of 10 nm and in thermodynamic equilibrium with a H2 partial pressure, we determined H concentrations and stresses, as a function of the H2 partial pressure, in both grains and grain boundaries. More importantly, we determined 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. With the determined intrinsic properties, the Gibbs-approach based adsorption isotherm predicted the H segregation in grain boundaries of nanograinedPd with an averaged grain size of 5 nm. The predication was verified by other reported experiment data.
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