The so-called ultra-high temperature materials refer to the most heat-resistant advanced materials that can still be used as usual in harsh environments such as stress and oxidation, and at ultra-high temperatures of about 2000 ° C. They are widely used in aerospace and other high-tech fields, such as the leading edge of the wing in hypersonic environment, the nose cone of the aircraft, and the front of the combustion chamber of the spacecraft.

        In ultra-high temperature materials, refractory metals and their alloys and carbon-carbon composites are quite limited because of their poor oxidation resistance, because the current development focus of ultra-high temperature materials at home and abroad has shifted to ultra-high temperature ceramics, which can be mainly divided into carbide ceramics, boride ceramics and nitride ceramics three categories. Among them, the melting point of the carbide can reach more than 3000℃, and the melting point of the carbide does not exist high temperature transition phenomenon, which makes it occupy a place in the field of ultra-high temperature ceramics, mainly hafnium carbide (HfC), tantalum carbide (TaC) and zirconium carbide (ZrC), etc. - Among them, the HfC and TaC cost is high, the preparation technology and production equipment requirements are high. Therefore, their large-scale use is limited. ZrC is favored because of its high cost performance and has become the "carry child" level of existence in the class of high-temperature materials.

Comparison of melting points of different types of refractory materials - performance advantages of zirconium carbide

        The figure below shows the crystal structure of ZrC (face-centered cubic crystal structure), with Zr atoms forming the cubic lattice and C atoms in the octahedral gap position of the lattice. A wide range of non-stoichiometric phenomena exists in carbon-zirconium chemical reaction systems, namely ZrCx (0.5≤x≤1). Therefore, zirconium carbide (ZrC) is a non-stoichiometric interstitial compound, and carbon vacancy is common in ZrC ceramic materials.

Crystal structure of ZrC
        A series of excellent characteristics of ZrC are attributed to its special structure, so it has high hardness (microhardness of 26Gpa), high melting point (3400℃), excellent high temperature mechanical properties, good wear resistance and corrosion, resistance to fission product attack and low neutron cross section and other excellent physical and chemical properties. Therefore, ZrC ceramic materials can be used in many fields, such as: tools, wear-resistant materials and so on.
In addition, ZrC also has a high hardness, can be used as an abrasive material for a variety of hard metals, glass or corundum processing; ZrC is regarded as the most promising new material for covering nuclear fuel particles because of its high strength and hardness, small thermal neutron absorption cross section and good radiation resistance.

        ZrC ceramics can be used as the matrix to improve its oxidation resistance and mechanical properties by introducing other phases. For example, metal Mo is added to ZrC, and Zr-Mo composites with different Mo contents can be prepared by different sintering methods (non-pressure sintering, hot isostatic pressing sintering, etc.). On the other hand, ZrC ceramics are introduced into other materials as a reinforcement phase, which can improve the performance of the overall material.