About Hexagonal Boron Nitride
Boron nitride is a synthetic material, which although discovered in the early 19th century was not developed as a commercial material until the latter half of the 20th century. Boron and nitrogen are neighbors of carbon in the periodic table - in combination boron and nitrogen have the same number of outer shell electrons - the atomic radii of boron and nitrogen are similar to that of carbon. It is not surprising therefore that boron nitride and carbon exhibit similarity in their crystal structure. The chemical combination of boron and nitrogen does not occur in nature. The properties, manufacture and applications is one of the key advanced ceramic in modern technology. Hexagonal boron nitride (h-BN) crystallizes like graphite in a layer lattice and is therefore often called “white graphite”. Its very good thermal (high melting- or sublimation point and good thermal shock stability) and physical characteristics (good electrical insulator, good heat conductivity and good high temperature lubrication qualities) make it an interesting ceramic material. One of the most well-known characteristics of hexagonal boron nitride is the very bad wettability by metal melts (like Al, Mg, Zn, Pb and Cu), slags as well as salt melts. Boron nitride is stable at air to approx. 1000°C, under reduced conditions or inert gases it can be used up to 1800°C. Crystal lattice of hexagonal boron nitride (bottom left) and graphite (bottom right). Because boron nitride and graphite show similar layer structures, boron nitride is often called "white graphite".
