Boron Nitride exhibits a hexagonal structure and is sometimes known as white graphite, due to its lubricity, anisotropic properties, heat resistance, and high thermal conductivity. This latter property, combined with a low thermal expansion, leads to excellent resistance to thermal shock. All three forms, Hot Pressed, Pyrolytic and Hot Isostatic Pressed, can be used at very high temperatures. However, in an oxidising atmosphere the maximum use temperature is 850-900C. Hot Pressed and Hot Isostatic Pressed Boron Nitride are produced by densification of powder, whereas Pyrolitic Boron Nitride is produced by Chemical Vapour Deposition (CVD), depositing onto graphite at temperatures in excess of 1800C.
Boron Nitride differs from graphite in having a high dielectric strength and low dielectric constant and is often used as an electrical insulator at very high temperatures. Chemically inert, Boron Nitride is used as crucibles for molten metals. Boron Nitride is non-toxic and transparent to microwaves. It may be machined to close tolerances.