Dirk Coster and Georg von Hevesy discovered hafnium in 1923 using X-ray spectroscopy on zircon ore samples from Norway. They identified element number 72 on the periodic table at a laboratory in Copenhagen.
Pure hafnium is a shiny silvery gray metal with a melting point of 2233 degrees Celsius and a boiling point exceeding 4600 degrees Celsius. Finely divided particles of this metal can ignite spontaneously in air due to its pyrophoric nature.
Control rods containing hafnium absorb neutrons effectively because the element has a neutron capture cross section of approximately 2000 barns. This property allows naval submarines and research reactors like FRM II to slow down or shut down reactor rates safely.
Most hafnium comes from heavy mineral sands ore deposits found in Brazil and Malawi alongside minerals like ilmenite and rutile. About half of all manufactured hafnium appears as a byproduct of refining zirconium through liquid-liquid extraction processes.
Microprocessors built at the 45 nanometer scale use hafnium oxide as gate insulators to reduce leakage current in transistors. Rocket nozzles for liquid-fuel engines utilize alloys such as C103 which contains 89% niobium plus 10% hafnium to increase heat resistance.