THE PRODUCTION OF METALS AND ALLOYS BY THE DECOMPOSITION OF OXYSALTS

The production of metals from the thermal decomposition of oxysalts is an interesting process because the metals are produced below their melting point in a highly active particulate form. In many instances the production of the metal as the primary reaction mechanism is obscured because the environmental conditions allow the production of oxide products as a further reaction process. Thermodynamic considerations can be applied which show when the production of the metal is to be expected as the prime product in an inert atmosphere. This had previously been applied to oxalates, but the same reasoning is shown here to be applicable to formate decompositions and probably applies to other oxysalt systems. The types of kinetic expressions which govern such decompositions are outlined, and correlations are made between the kinetic mechanism of decomposition and the change in surface area. The correlation between density and surface area takes the form V1/V2 = (S1/S2)3/2.(N)1/2 where V1 and V2 are the molar volumes of the oxysalt and the metal product, S1 and S2 are the molar surface areas, and N is the number of particles of metal produced from one particle of oxysalt. In the present study it is shown that thermal analysis techniques can be used to produce powdered alloys at temperatures far below the melting point of the metals by the decomposition of suitable complex oxysalts or mixtures of oxysalts.