a nitride ceramic

A nitride ceramic joins a metal or silicon to nitrogen. The stars are silicon nitride Si3N4 (tough, thermal-shock-resistant engine and bearing parts), aluminium nitride AlN (an electrical insulator that conducts heat almost like a metal, prized for cooling electronics), and titanium nitride TiN (the gold-coloured hard coating on drill bits). Nitrogen sits between carbon and oxygen, and nitrides sit, in personality, between the covalent carbides and the ionic oxides.

Metal-nitrogen bonds are strongly covalent, giving hardness, high stiffness, and refractoriness. Silicon nitride is the standout structural ceramic: its interlocking elongated grains give it unusually high fracture toughness and superb thermal-shock resistance (you can heat it red-hot and quench it), which is why it is used for turbocharger rotors and the rolling elements of hybrid bearings. Aluminium nitride is the exception that proves the insulator rule: it blocks electricity, yet its rigid light-atom lattice carries heat by lattice vibrations (phonons) extremely well.

Nitrides serve as bearings, cutting tools, engine components, LED and power-electronics substrates (AlN), and decorative-and-functional hard coatings (TiN). Like carbides, nitrides are not oxides, so they can oxidise in hot air, though silicon nitride again protects itself with a silica skin. Sialons, silicon-aluminium-oxynitrides, deliberately dissolve alumina into silicon nitride, blending the nitride and oxide families into tailorable tool materials, a good reminder that these branches interbreed.