报告题目：Phase transformations and plasticity in metal nanoparticles obtained by solid state dewetting of thin films

报告时间：2015年8月17日（星期一）10:00

报告地点：ACC-3会议室

报告人：Prof. Eugen Rabkin, Dean, Department of Materials Science and Engineering, TECHNION - Israel Institute of Technology

报告内容：

We report the results of our studies of solid state dewetting (agglomeration) of thin Au, Fe, and Ni films, and of Au-Fe bi-layers deposited on sapphire substrate.At the final stages of agglomeration an array of single crystalline faceted nanoparticles is produced. We demonstrate an extraordinary thermal stability of these nanoparticles and correlate it with the absence of crystalline defects (dislocations and grain boundaries) in the particles. Our nanoindentation studies of plasticity of Au and Fe nanoparticles produced by solid state dewetting demonstrate that the particles can be loaded elastically up to very high stresses approaching the theoretical shear strength of respective material. We observed a size effect in deformation of the Au nanoparticles, yet the sign of the effect depended on the shape of indentation probe and concomitant stress gradients in the particles. We related the observed deformation size effect with the microscopic details of dislocations nucleation and glide in the particles. The in-situ X ray diffraction studies of Fe nanoparticles demonstrated that they can be overheated by 200 C above the alpha-gamma transformation temperature. The transformation did occur in the particles of Fe-Au alloys, and in some of the thin Fe films during in-situ dewetting. Based on our data and nucleation models, we underline a deep analogy between nanoparticles plasticity (dislocations nucleation) and phase transformations (a-g transformation in Fe nanoparticles, nucleation of a stable phase).

附件.报告人简介

                                             汕头大学理学院

                                             2015/8/14