Tantalum wire is used as a filament for evaporating other metals. Tantalum is incorporated into a variety of alloys, conferring high melting point, ductility, strength, and corrosion resistance. Tantalum carbide is one of the hardest materials ever made. At high temperatures, tantalum has good 'gettering' ability. Tantalum oxide films are stable, with desirable dielectric and rectifying properties. The metal is used in chemical process equipment, vacuum furnaces, capacitors, nuclear reactors, and aircraft parts. Tantalum oxide may be used to make a glass with a high index of refraction, with applications including use for camera lenses. Tantalum is immune to body liquids and is a non-irritating metal. Therefore, it has widespread surgical applications.