北京大学湍流与复杂系统国家重点实验室-学术讲座

湍流与复杂系统国家重点实验室学术报告(报告人：Prof.Yang-Tse Cheng）

发布时间: 2009-07-07 03:31:00　　

SEMINAR SERIES

北京大学工学院力学与空天技术系

湍流与复杂系统国家重点实验室

题目：

报告人 Prof. Yang-Tse Cheng

Chemical and Materials Engineering,

University of Kentucky

报告内容摘要：

I will present several examples from our recent studies of nanostructured materials. Although these studies were mainly motivated by automotive applications, the examples helped unveil several general relationships between the growth, structure, and property of nanostructured materials that may be useful to other applications.

(1) Nanocomposite coatings and nanowires by physical vapor deposition. By co-deposition and controlled phase-separation, we have synthesized nanocomposite thin films with enhanced mechanical, tribological, and electrical properties. We have also demonstrated that the residual stress in the co-deposited films could be exploited to grow nanowires. These nanocomposite coatings and nanowires have applications in areas such as friction reduction, magnetic recording, and energy conversion.

(2) Microscopic shape memory and superelastic effects. Using micro- and nano-indentation techniques, we have demonstrated the existence of shape memory and superelastic effects under complex loading conditions at the micro- and nano-meter scales. These effects form the basis for applying shape memory alloys as “self-healing” surfaces and “metallic-based adhesion” materials. The microscopic shape memory effect can also be exploited to create surfaces with reversible roughness and texture for applications such as friction control and information storage.

(3) Understanding diffusion-induced-stresses in nanostructured materials for durable lithium ion batteries. We examined the effects of surface tension and surface modulus on diffusion-induced stresses within spherical nano-particles. We showed that both the magnitude and distribution of stresses could be significantly affected by surface mechanics if the particle diameter is in the nanometer range. In particular, a tensile state of stress may be significantly reduced in magnitude or even be reverted to a state of compressive stress with decreasing particle radius. This reduction in tensile stress may be responsible for the observed resilience to fracture and decrepitation of nanoparticles used in electrochemical energy storage.

These examples illustrate the myriad possibilities of using nanostructured materials and nanoscale characterization for industrial applications. They also demonstrate the multidisciplinary nature of materials research.

主持人：王建祥教授

时间：7月15日（周三）下午3:00

地点：英杰交流中心第四会议室

欢迎广大师生光临！

联系人：联系人：陈永强, 王建祥