ESTIMATION OF HEAT CAPACITIES AND OTHER THERMODYNAMIC PROPERTIES OF REFRACTORY BORIDES

摘要

High-temperature heat capacities and other related thermodynamic functions of the refractory borides were calculated and the results tabulated.nTheoretical expressions describe the contributions of various factors to the heat capacities (Cp) of crystalline solids. To apply these expressions to borides, however, a number of parameters need to be determined, so correlation methods are developed here for estimating many of these parameters. The correlations are based upon known properties of bo¬rides, carbides, nitrides, metals, and other compounds. Heat capacity factors that are taken into account are the dilata¬tion term, harmonic and anharmonic lat¬tice vibrations, the separate contributions of conduction electrons and d or f elec¬trons, and contributions of lattice defects.nAn important parameter in the dilata¬tion factor is the thermal expansivity. It is found that thermal expansivity corre¬lates with atomization energy (AE ) and degree of ionic or covalent bonding in the compound.