Abstract
The formation process and the internal structure of Ag-NiO composite powders prepared by spray pyrolysis were investigated. Further, the changes in structure of the composite powders were studied after heating in air and H2 gas stream. The distribution of Ni grains in the composite powders prepared by spray pyrolysis was compared with that of the usual products obtained by a mechanical mixing method.
The internal structure of Ag-NiO composite powders was observed by SEM photographs and EPMA analysis with the result; there exist Ag layer in the external region and Ag-NiO composite layer in the internal region in a single particle. The formation process of the composite powders was discussed from the observation of cross sections of the composite powders and the thermogravimetric analysis of some nitrates. The two layer structure was composed by the deposition of Ag layer in the external region with decomposition of AgNO3 after the formation of Ag-NiO composite in the internal region.
The two layer structure of Ag-NiO composite powders did not change by heating in air. On the other hand, it was found that those structures could change and fine Ni grains were distributed uniformly after the reduction of the composite powders by heating in H2 gas stream.
