Formation of Co2P in the combustion regime

Abstract

Combustion of the system Co-P produces the compounds Co/sub 2/P, CoP and CoP/sub 3/, the first two being producible in the combustion regime, while for synthesis of stoichiometric Co/sub 2/P at normal argon pressure, an original mixture with a certain excess of phosphorus is required. The present experiments were performed with electrolytic cobalt powder and red phosphorus. As the Co-P mixture is diluted by the final product (Co/sub 2/P) there is a decrease in combustion temperature and rate, unaccompanied by any of the anomalies seen with dilution by cobalt. It can be suggested that although the combustion in the Co-P system and, possibly, i-- other phosphide systems, is not gasless in its kinetic aspects the combustion mechanism is similar to that in gasless systems. It is shown that formation of the phosphide Co=3''P and specimens wyth composition Co-Co/sub 2/P in the combustion regime occurs with participation of a lIqui) phase of eutectic composition. Combustion occurs in a self-oscillating regime. The temperature for Co/sub 2/P formation is close to its melting point, and the process activation energy comprises 205 kJ/mole.