Compatibility of some high-heat oxides with BN

High-temperature compatibility of the most promising insulating materials among nitrides-boron nitride with a number of high-temperature insulating oxides: Al2O3, MgO ZrO2, SiO2 is described. The investigations have been performed by studying processes of interaction of powdered mixtures in nitride-oxide systems depending upon a temperature under predetermined pressure conditions in purified argon. Isobar-isothermal potentials (ΔZ deg) of possible interaction reactions in each system for 1.400-2.000 deg C have been calculated. All the calculated values of isobar-isothermal potentials are positive thus indicating that reactions running left-to-right are not possible under standard equilibrium conditions. An analysis of the dependence of BN isobar-isothermal potential upon temperature indicates that BN dissociation is possible under standard equilibrium conditions at a temperature higher than 2.000 deg C. In BN-Al2O3 system there is no interaction at 1.500-1.700 deg C with pressure being 1.10-5 and 760 mm of a mercury column. The weight is decreased on account of BN evaporation. An increase of interaction temperature depending upon a higher pressure is typical of all the systems and results from some peculiarities of interaction with gaseous products formed whose rate of liberation reduces as pressure goes up