Refractory

Refractory, nonmetallic materials that can withstand high temperatures without losing their hardness. Refractory substances include magnesite, dolomite, silica, alumina, chromite, and zirconia. Firebrick or fire clay is a common refractory, using aluminum silicates and other substances to retain their original properties. Refractories are used industrially in kilns, furnaces, and crucibles, where they line or insulate the walls of these high-heat chambers or containers. Refractories are also required in nuclear power plants, where high levels of radioactivity are capable of generating intense heat.