Hafnium alloy contains metal element hafnium, which has the highest melting point in the world. The substance with the highest known melting point is a compound of hafnium: tetrahfnium pentacarbide (Ta4HfC5), with a melting point of 4215 degrees Celsius.
Hafnium, metal Hf, atomic number 72, atomic weight 178.49, is a lustrous silver-gray transition metal. Hafnium has 6 kinds of natural stable isotopes: hafnium 174, 176, 177, 178, 179, 180. Hafnium does not react with dilute hydrochloric acid, dilute sulfuric acid and strong alkali solution, but it is soluble in hydrofluoric acid and aqua regale. The element name comes from the Latin name for the city of Copenhagen. The pure hafnium salt was obtained by fractional crystallization of fluoro salt in 1925 by Swedish chemist helveche and Dutch physicist koster, and was reduced by metal sodium to obtain pure hafnium metal. Hafnium content in the earth's crust is 0.00045% and is often associated with zirconium in nature.
If single theory of binary compounds, tantalum carbide alloy has the highest melting point (3983 ° C), but hafnium carbide alloy is one of the highest melting point alloy (3928 ° C). The one that's mentioned in the title should be the tantalum hafnium carbon alloy, which wikipedia says has the highest melting point of any known compound. The encyclopaedia britannica once included this conclusion, but later changed it to include one of the substances with the highest melting point.
The high melting point of ta-hf-c solid solution is due to the strong chemical bonding between HfC and TaC (strong hybridization of class 5d and 2p). This interpretation was also mentioned in the literature of Osama et al., and according to the research conclusions in the literature, it was proposed that HfC and TaC could form uniform single-phase cubic crystal structure, which improved the stability of the structure.
The difference in the melting point value may be caused by the unavoidable changes in the composition and structure of the compound and the lack of measuring means in the process of high temperature melting point measurement.
