Hafnium carbonitride (HfCN) is an ultra-high temperature ceramic (UHTC) mixed anion compound composed of hafnium (Hf), carbon (C) and nitrogen (N).
molecular dynamics calculations have predicted the HfCN (specifically the HfC0.75N0.22 phase) to have a melting point of 4,110 ± 62 °C (), the highest known for any material. Another approach based on the artificial neural network machine learning pointed towards a similar composition — HfC0.76N0.24. Experimental testing conducted in 2020 has confirmed a melting point above , substantiating earlier predictions made with atomistic simulations in 2015.
Properties The HfCxN1−x has been assessed to possess the following properties: Thermal conductivity: 19–24 W·m−1·K−1 at room temperature, 32–39 W·m−1·K−1 at high temperature and with increased nitrogen content. Electrical conductivity: (149×104)–(213×104) Ω−1 m−1 Plasticity limit: Fusion enthalpy: Flexural strength: 638 ± 28 MPa at room temperature, 324 MPa at , 139 MPa at , 100 MPa at . Fracture toughness: 6.73 ± 0.07 MPa·m1/2, 4.7 ± 0.3 MPa·m1/2 Vickers hardness: , 21.3 ± 0.55 GPa ()
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