Like Niobium, Tantalum is a heat-tolerant refractory metal with excellent corrosion resistance. Often alloyed with other metals, tantalum is used to make super alloys used in chemical processing, jet engines and nuclear reactors. Its oxidation properties also make it an excellent choice for many electronic applications, including electrolytic capacitors and high-power resistors. Tantalum is also highly bio-compatible and used extensively for medical applications, such as skull plates, hip joints, suture clips and stents.
Niobium (also known as columbium) is a shiny, ductile metal primarily used in alloys. It improves the properties of steel and is often used in gas pipelines, jet engines and structural applications. Because of its corrosion resistance and ability to perform at high temperatures, niobium metal plates, rods and sheets are used in sputtering targets and chemical processing equipment. At extremely low temperatures, it becomes superconductive. Superconductive niobium wire is used to make extremely powerful electromagnets used in magnetic resonance imagery and particle accelerators.
Tungsten has the highest melting point of all metals and, at temperatures greater than 1650°C, the highest tensile strength. Its thermal expansion rate is similar to that of borosilicate glass and silicon. Tungsten’s good thermal and electrical conductivity make it an excellent choice for microprocessor applications. It is also used in electron emitters, heater coils, cathode ray tubes, electrical contacts and a variety of high-heat applications.
Used with Alumel® in type K thermocouples and with Constantan in type E thermocouples, Chromel® is made of nickel and chromium.
With an extremely low coefficient of thermal expansion, approximately one-tenth that of carbon steel at temperatures up to 400° F, Invar® is often thought of as the material of choice for low expansion nickel alloy applications. The ability to maintain strength at very low temperatures also makes it the optimum choice for containing some liquid gasses.