Boron carbide silicon carbide composite ceramic and preparation method thereof

Abstract

The invention relates to a method for preparing boron carbide silicon carbide composite ceramic and belongs to the technical field of ceramic materials. The boron carbide silicon carbide composite ceramic is prepared by mechanically alloying three-element mixed powder of boron carbide, carbon powder and silicon powder and sintering by a reaction hot-pressing technology, wherein the three-element mixed powder comprises 50 to 90 weight percent of boron carbide powder, 15 to 3 weight percent of carbon powder and 35 to 7 weight percent of silicon powder; and the molar ratio of the carbon powder to the silicon powder is 0.8 to 1.2. The high-compactness boron carbide silicon carbide composite ceramic can be obtained at low temperature without adding a liquid phase sintering aid. Silicon carbide which is obtained through in-situ synthesis in the sintering process of carbon and silicon has high purity and the crystal grains are small and dispersed uniformly, so the mechanical property of the ceramic is improved. The boron carbide silicon carbide composite ceramic prepared by the method has high compactness, high hardness and high high-temperautre mechanical property and can serve as an anti-impact and wear-resistant part of precise structure engineering.

Description

technical field [0001] The invention relates to a composite ceramic material and a preparation method thereof, in particular to a boron carbide silicon carbide composite ceramic and a preparation method thereof, belonging to the technical field of ceramic materials. Background technique [0002] Boron carbide (B 4 C) It is a superhard material whose hardness is second only to diamond and cubic boron nitride. It has high melting point, low density, excellent wear resistance, excellent chemical stability and high neutron absorption capacity. It is widely used in military protection, nuclear power plant, chemical industry and aerospace fields. but B 4 C is a ceramic material with strong covalent bonds. Covalent bonds account for 93.9%, and its plasticity is poor, the grain boundary movement resistance is large, and the surface tension is very small in solid state, so boron carbide sintering is very difficult. In addition, the fracture toughness and strength of boron carbide ...

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Problems solved by technology

[0007] In the preparation methods involved in the above patents, if Si is used as an infiltration agent for vacuum infiltration, a large amount of Si elemental remains in the product, which reduces the hardness and high-temperature mechanical properties of the product. In addition, the product prepared by this method , the distribution of the two phases is uneven, resulting in unstable performance of the product; while the product obtained by liquid phase sintering has larger grains, lower hardness and poor high-temperature mechanical properties

The products obtained by these two methods have low hardness, are not resistant to high temperature, and have unstable performance. They can only meet daily applications and are not easy to be used in precision structural engineering.

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