Abstract
It has been considered that NiO/SiO2 particles prepared by chemical vapor deposition are agglomerates of several hundred Angstrom of NiO and SiO2 particles. The reaction environments of particle growth were in a free molecular region, and the extent of super saturation S for NiO and SiO2 vapor varied with temperature and location in the reactor, but the orders are almost 1020. It is also considered that the nucleation rate is ultimately rapid. Then, the particle growth was analyzed with the mechanism of Brownian agglogemate, corrected for the axial temperature distribution of the reactor, and the following relation was obtained between particle diameter d and residence time τ :
d=ατ2/5
Further, the value of sticking coefficent c as calculated from a pure NiO production process was markedly larger than that calculated from a NiO/SiO2 production process, and the ratio of sticking coefficents was in agreement with the Ni content in the particles.
From these facts, it is revealed that the growth of NiO particles in the NiO/SiO2 production system suppressed the NiO particle growth by blocking of SiO2 particles, but this is effective for homogeneously dispersing into the SiO2 matrix.
