THE STRUCTURE OF AGGREGATED NIO PARTICLES IN NIO/SIO2 PARTICLES PREPARED BY CVD METHOD

The structure of NiO particles in the NiO/SiO2 agglomerates prepared by CVD was investigated by XRD, TEM, XPS and TPR. TEM observation and XRD analysis indicated that the NiO particles obtained were in the aggregated state, and that the size of them became large, while that of primary particles became small, with increasing preparation temperature. TPR and XPS analyses indicated that a trace amount of nickel silicate coexisted with the NiO/SiO2 particles, most likely at the outer region of the NiO aggregates near the interface with the SiO2 deposited on them. From these results and the hydrogen reduction experiments, we proposed the following structure model of the NiO/SiO2 agglomeration; at high preparation temperature small primary NiO particles grow into large secondary particles, followed by coating with thin SiO2 layers, while at low temperature large primary NiO particles grow and are surrounded by SiO2 matrix.