Heats of Formation of Aluminum Diboride and α-Aluminum Dodecaboride.

ABSTRACT

The energies of combustion of AlB2 and α-AlB12 were measured in a bomb calorimeter using fluorine as the oxidant. Major problems of this investigation were the assessment of the state and distribution of impurities in the samples and the establishment of the stoichiornetry of the aluminum boride phase. We obtain -16±3 kcal mol-1 and -48±10 kcal mol-1 for the heats of formation of AlB2 and α-AlB12, respectively. The uncertainties cited are the overall experimental errors. Their magnitudes are chiefly due to uncertainties in the impurity correction applied and the uncertainties in the heats of formation of the combustion products.