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In recent years, metal composite refractory materials have become a research hotspot, such as introducing Si, Al and Fe into refractory materials, research and development of Si-Si3N4-corundum ceramic cups, Al-carbon-corundum skateboards and Fe-AlN -MgO-Si3N4 composite materials, etc., some have been promoted and applied in production, and achieved satisfactory results. It is worth mentioning that although Si is not a metal, it has the characteristics of metal ductility and plasticity. It is often classified as a metallic material.

The research shows that once the metal is compounded as a component in the refractory material, it not only has the corresponding compound to strengthen and toughen the matrix material under an appropriate atmosphere, but also has the functions of plastic phase molding, sintering promotion and oxidation resistance.

The role of metals in refractory materials:

Plastic phase forming: The metal lattice will slip under the action of stress, which has plastic characteristics. Compared with the hard inorganic material particles, it will play the plastic forming characteristics during the forming process, so that the same The density of the green body prepared under the molding pressure is higher than that of the sample without metal addition.

Promote sintering: The sintering promoting effect of metals on refractory materials can be attributed to two factors: First, the introduction of metal-forming plastic phase molding can increase the density of the green body, shorten the distance between particles, and reduce the diffusion and mass transfer during firing. The energy required; Second, the melting point of the metal is generally lower than that of the refractory material, which can generate a liquid phase at a lower temperature. The capillary force formed by the liquid phase and its own viscous flow accelerate the atom migration rate and the green body. Shrinkage promotes the densification process of sintering.

Improve toughness: Metals can improve the toughness of composite materials through mechanisms such as crack bridging, crack deflection, and crack barrier. Among them, crack bridging is the most effective toughening mechanism, that is, when the crack propagates to the interface between the metal material and the matrix material, Due to the ductility of the metal particles, the cracks make the stress elongated, which will exert a bridging stress on the upper and lower surfaces of the crack. On the one hand, it can prevent the crack from opening and reduce the strength factor of the crack tip. The plastic deformation occurs at the opening, which consumes the energy of the crack tip and plays a role in toughening.

Oxidation resistance: Carbon composite refractories have excellent thermal shock resistance and slag resistance due to the presence of carbon, but there are defects of easy oxidation. Once carbon is oxidized, its advantages will be lost. In order to give full play to the advantages of carbon composite refractories, it is often by adding appropriate additives to improve its oxidation resistance. Due to its lively performance, metal easily reacts with O2 and CO. It has been used as an antioxidant in refractory materials. Al, Si, Mg and corresponding alloys are commonly used as antioxidants.

In-situ reaction to generate non-oxides: Introduce metals into refractory materials, during the firing process, use their reaction with raw material components or surrounding gases to generate non-metallic reinforced and toughened phases, which can improve the performance of the substrate at normal and high temperatures Thermal shock and other effects. At present, this technology has received extensive attention. It can be seen from the above that the addition of metals to refractory materials has a positive effect on the mechanical properties and oxidation resistance of refractory materials, which indicates that they have broad application prospects in refractory materials. With the continuous development of science and technology and continuous breakthroughs in the field of science, the performance of metal composite refractories will continue to be optimized, and its scope of application will be further expanded. (Zhengda High Temperature Research Institute: Li Wenfeng)