ABSTRACT
The sintering behavior of silver crystallites supported on nonporous alumina substrates has been investigated by means of transmission electron microscopy. When the specimens were heated in O2 at temperatures in the range 250–400°C, the following phenomena were observed: crystallite migration and coalescence, disappearance of small and large particles, decrease in size of small crystallites, and appearance of a large number of small crystallites of circular or wormlike shape. A few possible explanations are suggested for the appearance of a large number of small particles. The behavior of silver particles healed in H2 at temperatures in the range 300–400°C was qualitatively similar to that observed in O2. Sintering was, however, less severe, and the number of small particles that appeared was smaller. When heated in C2H4, the particles changed their shape from circular to ellipsoidal and, with few exceptions, remained almost unchanged in their locations, most probably as a result of carbon deposition on the surface and around the particles. When heated in a mixture of C2H4 and O2, the particles exhibited milder sintering than in O2, but acquired more irregular shapes, as during their heating in C2H4. © 1988 Academic Press, Inc.
