hafnium carbonitride is a material with a high melting point that was thought to be impossible to achieve until recently. It’s composed of hafnium, nitrogen, and carbon. It’s a good choice for aircraft parts that need to withstand high heats, according to researchers at the National University of Science and Technology (NUST) in Moscow.

Hafnium carbide is considered a great material for hypersonic structures because of its excellent thermal shock resistance, high temperature strength, and oxidation resistance at elevated temperatures. However, it oxidizes above 700 degF, which makes it unsuitable for hypersonic flight.

This research effort developed a new high temperature thermal protection infiltrated coating made from hafnium carbonitride that was processed using a new processing technique called reactive solution infiltration. This process produces integrated bond layers that are reactively fused to the C/C substrate allowing for high reusability and continuous use at elevated temperatures.

The materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and nanoindentation techniques. They exhibit a constant stoichiometric ratio, Hf/(C+N), and improved mechanical properties with the increase of negative bias voltage from 17 to 32 GPa for hardness and from 200 to 280 GPa for elastic modulus.

The Hf(C,N)-MoSi2 samples were deposited by spark plasma sintering from HfC-N target mixtures in a reactive nitrogen atmosphere with different applied negative bias voltages (0, -50, -100, and -150 V). The bulk Hf(C,N)-MoSi2 is mainly characterized by the formation of monoclinic hafnium oxide, accompanied by the release of gaseous reaction products such as CO2 and NO.