Thermodynamics of Nitrogen in B ₂ O ₃ , B ₂ O ₃ ─SiO ₂ , and B ₂ O ₃ ─CaO Systems

Abstract

The BN solubilities for B 2 O 3 , B 2 O 3 ─SiO 2 , and B 2 O 3 ─CaO systems have been measured mainly at 1823 K using a graphite crucible. The capability of the systems for nitrogen dissolution is compared with that of silicate systems in terms of nitride capacity. The dependence of nitrogen solubility in molten CaO containing 15 mol% of B 2 O 3 on oxygen and nitrogen partial pressures is also investigated. It has been found that there are two mechanisms for nitrogen dissolution, namely as chemically bonded nitrogen and as physically dissolved nitrogen gas.