XAFS studies on the supported Ni catalysts prepared from Ni colloids
Introduction It is well known that Ni catalysts are very useful for many catalytic reactions. But the size of Ni particles on catalyst is typically 20-100 nm and the preparing the smaller Ni particles on the support is desired. Colloidal metal particles have been expected as a superior catalyst precursor for supported solid catalyst because of their small particle size and the narrow size distribution. In this study, we prepared Ni metal colloid by using tBuONa as a stabilizer and used for the Ni catalyst precursor. Non-porous SiO2 as well as meso-porous SiO2 (HMS) were used as the support. The supported Ni catalysts were reduced by hydrogen and were characterized by XAFS analysis.
A mathematical model is developed for simulating the formation and growth of phases in the diffusion of aluminum through the nickel matrix of high-temperature alloys. The kinetic laws of diffusion processes in multiphase coatings deposited from a gaseous phase by the method of circulation are determined. The suggested mathematical model is tested experimentally.