Thermodynamic and Kinetic Studies for a Refractory Materials Program

Work during 1963 is reported and the work from mid-1960 reviewed on a comprehensive program of thermodynamic and kinetic studies necessary to the theoretical consideration to temperatures of 3000K of the reactions of the zirconium and hafnium carbides and borides with oxygenor halogen-containing atmospheres. ; • Work presented includes: preparation of borides and carbides; low ', temperature heat capacity measurements on H1B2, HfC and hafnium metal; estimation of entropies at 298K for refractory diborides, nitrides, carbides, and oxides from high temperature heat content data; current status of heats of formation of the borides and carbides from oxygen and fluorine bomb calorimetry; and studies proving the feasibility of the "matrix isolation technique'" for spectroscopy of high temperature molecules through studies on the Lithium halides. Status of electron diffraction, equilibria, and heat of solution studies of the hafnium and zirconium halides is presented. Kinetic studies completed on the oxidation and fluorination of the hafnium and zirconium carbides and diborides are presented in detail. From ac and dc electrical conductivity studies on tetragonal ZrC^, a model of the defect structure is devised and oxygen diffusion in ZrC>2 is calculated. This technical documentary report has been reviewed and is approved. W.G. RAMKE Chief, Ceramics and Graphite Branch Metals and Ceramics Division Air Force Materials Laboratory