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Zirconium Carbide

The use of zirconium carbide (ZrC) in engineering applications has been limited by the lack of a fully developed, commercially viable sintering process. Hot pressing powders at between 1900 °C and 2300 °C can achieve densities of greater than 93%. Additives such as ZrB2 enhance the sintering and produce ZrC with low porosity levels (2% to 4%) at around 2100 °C for 2 hours.

Coatings of zirconium carbide can be deposited as a coating by physical vapour deposition (PVD) and chemical vapour deposition (CVD).

Key Properties

Zirconium carbide (ZrC) is a transition metal carbide which is characterised by:

  • High hardness
  • High melting point
  • Electrical conductivity
  • High strength

These properties give it the potential to be a useful engineering ceramic.

Like other carbides, oxidation to carbon dioxide and zirconium oxide limits its use in oxidising environments.

Table 1. Typical Physical and Mechanical Properties of Zirconium Carbide

Property Value
Density (g.cm-3) 6.73
Fracture Toughness K1c (MPa.m0.5) 2.8
Bend Strength (MPa) 990
Hardness (GPa) 24.4
Electrical Conductivity (Ohm.cm) 78 x 10-6
Melting Point (°C) 3250

Applications

The material has yet to find wide commercial application and is found generally in development prototypes.

Applications quoted in literature include:

Field Emitters

Field emission arrays are used in flat video displays. They also have potential uses in microwave devices and spacecraft charge dissipation devices.  As opposed to display applications, many potential applications need high current per tip and the ability to operate in vacuum.  Transition metal carbides meet the property requirements and have been produced by vapour deposition.

Coating for UO2 Particle Fuel

ZrC coated UO2 particle fuel is a promising fuel for high temperature gas cooled reactors. The layer acts as a diffusion barrier to the metal fission products such as Cs. ZrC could replace SiC, which is more generally used. The ZrC layer is deposited by CVD.  It is compatible with UO2 and fission products and able to sustain a large strain at high temperatures.

Ultrahigh Temperature Applications

ZrC is a candidate for ultrahigh temperature applications because of its high melting point, good thermal shock resistance and absence of phase changes in the solid state. Components with operating temperatures of 2200 to 3000°C would result in a cleaner burning rocket engine. Barriers to its use are the absence of a coating to protect against oxidation and of a cost-effective manufacturing process for near-net shaped components.

Primary author: Ceram Research

For more information on this source please visit Ceram Research Ltd.

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