Preparation of palladium-based alloy powders by the thermal decomposition of binary complex ammonium oxalate salts

Abstract

The possibility of obtaining powder alloys (solid solutions) by thermal decomposition of salts of the types [Pd(NH3)4[M(C2O4)2] and (M(NH3)n[Pd(C2O4)2] was investigated. Salts of the desired compositions were synthesized by double decomposition of the ammonium and oxalate complexes of the metals in aqueous solution. The production of new compounds was confirmed by x-ray diffraction analysis. It was shown that pyrolysis of the salts (Pd(NH3)4][M(C2O4)2] occurs in stages: initially one of the oxalate groups migrates to the cationic part, and later the products obtained, (Pd(NH3)2](C2O4)] and MC2O4, decompose. The decomposition temperatures of the salts obtained correlated with those of MC2O4. Pyrolysis of [Pd(NH3)4] [M(C2O4)2] produced highly dispersed solid solution powders of palladium with copper, nickel, and copper, respectively, with the atom ratio Pd:M = 1:1, and the intermetallic compound PdZn. The powder particle sizes did not exceed 1 μm. Initial salts, intermediate products, and oxides were not detected in the powders.