Hafnium

Hafnium, chemical element, symbol Hf; for physical constants see Periodic Table. Hafnium was discovered in 1923, by Dirk Coster and Georg von Hevesey, identified by means of X-ray spectroscopic analysis of zircon. It is found in most zirconium minerals. Zirconium and hafnium are 2 of the most difficult elements to separate. The element is prepared by reducing the tetrachloride with magnesium. Hafnium is a brilliant silver, ductile, corrosion- resistant metal. It is used in nuclear reactor control rods. The metal is pyrophoric in finely divided form and absorbs hydrogen at elevated temperatures. Hafnium carbide is the most refractory binary composition known, and hafnium nitride is the most refractory metal nitride. Hafnium is used in alloys and as a getter in gas-filled and incandescent lamps.