Hafnium carbonitride explained

Hafnium carbonitride (HfCN) is an ultra-high temperature ceramic (UHTC) mixed anion compound composed of hafnium (Hf), carbon (C) and nitrogen (N).

Ab initio molecular dynamics calculations have predicted the HfCN (specifically the HfC_0.75N_0.22 phase) to have a melting point of 4,110 ± 62 °C (NaNabbr=onNaNabbr=on), highest known for any material.^{[1] [2]} Another approach based on the artificial neural network machine learning pointed towards a similar composition — HfC_0.76N_0.24. Experimental testing conducted in 2020 has confirmed a melting point above 4000C, substantiating earlier predictions made with atomistic simulations in 2015.^[3]

Properties

The HfC_xN_1−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: 2000C
• Fusion enthalpy: 150kJ/mol
• Flexural strength:
  • 638 ± 28 MPa at room temperature,
  • 324 MPa at 1000C,
  • 139 MPa at 1600C,
  • 100 MPa at 2000C.
• Fracture toughness: 6.73 ± 0.07 MPa·m^1/2, 4.7 ± 0.3 MPa·m^1/2
• Vickers hardness: 19.08GPa, 21.3 ± 0.55 GPa (21.3GPa)

Notes and References

1. Buinevich . V.S. . Nepapushev . A.A. . Moskovskikh . D.O. . Trusov . G.V. . Kuskov . K.V. . Vadchenko . S.G. . Rogachev . A.S. . Mukasyan . A.S. . 2020-03-17 . Fabrication of ultra-high-temperature nonstoichiometric hafnium carbonitride via combustion synthesis and spark plasma sintering . Ceramics International . en . Elsevier . 46 . 10 . 16068–16073 . 10.1016/j.ceramint.2020.03.158 . 0272-8842 . 8596178549 . 216437833.
2. Web site: Science . The National University of . MISIS . Technology . 2020-05-27 . Scientists develop the most heat-resistant material ever created . 2023-04-02 . phys.org . en.
3. Hong. Qi-Jun. van de Walle. Axel. 2015. Prediction of the material with highest known melting point from ab initio molecular dynamics calculations. Physical Review B. 92. 2. 020104. 10.1103/PhysRevB.92.020104. 2015PhRvB..92b0104H. 1098-0121. free.