Hafnium carbide () is a chemical compound of hafnium and carbon. Previously the material was estimated to have a melting point of about 3,900 °C.[ More recent tests have been able to conclusively prove that the substance has an even higher melting point of 3,958 °C exceeding those of tantalum carbide and tantalum hafnium carbide which were both previously estimated to be higher.]
Atomistic simulations conducted in 2015 predicted that a similar compound, hafnium carbonitride (HfCN), could have a melting point exceeding even that of hafnium carbide.
Hafnium carbide is usually carbon deficient and therefore its composition is often expressed as ( x = 0.5 to 1.0). It has a cubic (rock-salt) crystal structure at any value of x.
Hafnium carbide powder is obtained by the smelting of hafnium(IV) oxide with carbon at 1,800 to 2,000 °C. A long processing time is required to remove all oxygen. Alternatively, high-purity HfC coatings can be obtained by chemical vapor deposition from a gas mixture of methane, hydrogen, and vaporized hafnium(IV) chloride.
Because of the technical complexity and high cost of the synthesis, HfC has a very limited use, despite its favorable properties such as high hardness (greater than 9 Mohs
The magnetic properties of change from paramagnetic for x ≤ 0.8 to diamagnetic at larger x. An inverse behavior (dia-paramagnetic transition with increasing x) is observed for Tantalum carbide, despite its having the same crystal structure as .
See also
