Hafnium carbonitride (HfCN) is a mixed anion chemical compound of

hafnium Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

and

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

. With a melting point of above 4,000 °C, it is the most refractory compound known. No other substance has a higher melting point at atmospheric pressure. In 2015, atomistic simulations predicted that a Hf-C-N material could have a melting point exceeding Ta₄Hf₁C₅ and

hafnium carbide Hafnium carbide ( Hf C) 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 hig ...

by 200 °C. This would later be proven in experimental testing conducted in 2020 by the National University of Science and Technology (NUST) in Moscow. Samples of both hafnium carbide and hafnium carbonitride were tested in the same environment in which hafnium carbonitride was shown to have a melting point exceeding 4,000 °C and higher than that of hafnium carbide (3,958 °C). More precise testing has yet to be conducted to determine the substance's exact melting point.

References

{{Nitrides Hafnium compounds Carbides Nitrides