hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. It is a translucent silver-gray transition metal, chemically similar to zirconium and found together in ores containing zirconium. In 1869, Dimitri Mendeleev first predicted the existence of hafnium, and in 1923 it became the second most-discovered element among the stable elements. It was named after the Latin name of Hapnia in Copenhagen, where the element was found. Hafnium is used in filaments and electrodes, and has a property of absorbing neutrons. It is used in control rods of reactors together with zirconium alloys. Hafnium oxide is also used in semiconductor manufacturing processes. It is used to make special purpose superalloy by mixing with niobium, titanium, tungsten and so on.