Thermodynamic analysis of the Ca-C-N system

Abstract

In the calcium-carbon-nitrogen (Ca-C-N) system there are two known ternary compounds: calcium cyanamide (CaCN2) and calcium cyanide (Ca(CN) 2). Calcium cyanamide is commercially produced by the nitrogenation of calcium carbide, while calcium cyanide is manufactured by the reaction of calcium cyanamide with carbon in a fused salt melt. In addition to the industrial production of these compounds, it has also been proposed that they can act as intermediate species in natural diamond formation. There is very little information in the literature regarding the thermodynamic properties of the Ca-C-N system and in particular calcium cyanide. Since this compound apparently only forms as a complex in a molten salt under very specific conditions, then it has proven difficult to determine its thermodynamic properties. Previously, the authors have determined these properties and in the present research, this thermodynamic information was utilized to develop predominance area diagrams for the Ca-C-N system at various temperatures. The application of this thermodynamic information leads to an improved understanding of the mechanism of formation of calcium cyanide and also the factors which govern the optimization of the industrial production method.