Boron nitride is a white solid material in the as produced hot pressed form. It is a low porosity solid. It is easily machined into complex shapes using standard carbide tooling. The material is anisotropic in its electrical and mechanical properties due to the platy hexagonal crystals and their orientation during the hot press consolidation.
Boron nitride is often referred to as “white graphite” because it is a lubricious material with the same platy hexagonal structure as carbon graphite. Unlike graphite, BN is a very good electrical insulator. It offers very high thermal conductivity and good thermal shock resistance. BN is stable in inert and reducing atmospheres up to 2800°C, and in oxidizing atmospheres to 850°C.
Three grades are commonly used, including a boric oxide binder system, a calcium borate binder system, and a pure diffusion bonded grade. The boric oxide containing material (Grade BO) absorbs moisture which causes swelling and property degradation. The calcium borate containing material (Grade CA) is moisture resistant. The pure BN material (Grade XP) contains no binders and is used for extremes of temperature and where purity is important. The boric oxide material is the most commonly used grade.