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Hafnium carbonitride

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 HfC<sub>0.75</sub>N<sub>0.22</sub> phase) to have a melting point of 4,110&nbsp;±&nbsp;62&nbsp;°C (), the highest known for any material. Another approach based on the artificial neural network machine learning pointed towards a similar composition — HfC<sub>0.76</sub>N<sub>0.24</sub>. Experimental testing conducted in 2020 has confirmed a melting point above , substantiating earlier predictions made with atomistic simulations in 2015.

Properties

The HfC<sub>x</sub>N<sub>1−x</sub> has been assessed to possess the following properties:

  • Thermal conductivity:
  • 19–24 W·m<sup>−1</sup>·K<sup>−1</sup> at room temperature,
  • 32–39 W·m<sup>−1</sup>·K<sup>−1</sup> at high temperature and with increased nitrogen content.
  • Electrical conductivity: (149×10<sup>4</sup>)–(213×10<sup>4</sup>) Ω<sup>−1</sup> m<sup>−1</sup>
  • 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·m<sup>1/2</sup>, 4.7 ± 0.3 MPa·m<sup>1/2</sup>
  • Vickers hardness: , 21.3 ± 0.55 GPa ()

References