Several diborides, carbides and nitrides of the group IVB and VB transition metals are a family of materials known as ultrahigh temperature ceramics based on melting temperatures in excess of 3000°C. In recent years, hafnium and zirconium borides in ultrahigh temperature ceramics have attracted increasing attention from material scientists and engineers due to their unique combination of high melting point, high strength, high electrical and thermal conductivities, excellent corrosion resistance, and good oxidation resistance. These properties make the ultrahigh temperature ceramics promising candidates for high-temperature applications, including thermal protective structures for leading-edge parts on hypersonic re-entry space vehicles, propulsion systems, furnace elements, refractory crucibles, and plasma-arc electrodes.