An Experimental Investigation of the Melting Behavior of Small Metal Particles

摘要

A dark-field transmission electron microscope technique was applied to a collection of submicron sized metal crystallites prepared by in-situ physical vapor deposition onto an amorphous carbon substrate in a vacuum of 2 x 10 to the -7th power torr in order to determine the melting behavior of individual crystallines. It was found that each particle melted suddenly at a single temperature which decreased with decreasing size. No liquid sheath was observed at any time. The melting temperature seemed to decrease nearly linearly with increasing surface curvature. Flat platelets with a near zero surface curvature but a significant surface to volume ratio showed no noticible size dependence of melting temperature. Oxidation of the particles raised their melting temperature as did embedding the particles in an amorphous carbon matrix. A simple thermodynamic model can account for all of the above observed effects. (Author)