SiC-based composite ceramic and preparation method thereof

Abstract

The invention discloses SiC-based composite ceramic and a preparation method thereof. The SiC-based composite ceramic is prepared from Si and SiC, wherein SiC is a continuous matrix phase, Si is a free phase, and the free phase is distributed in the continuous matrix phase on the surface of the SiC-based composite ceramic. The preparation method comprises the following steps that 1, a mixed solid phase, organic monomers, a cross-linking agent and water are mixed and then subjected to ball milling, pre-mixed slurry is obtained, the mixed solid phase is composed of carbon black and alpha-SiC ceramic powder, the pre-mixed slurry is subjected to vacuum degassing and then mixed with an azoic compound, and mixed slurry is obtained; 2, gel casting is carried out; 3, gaseous phase siliconing sintering is carried out. The SiC-based composite ceramic has the advantages of being high in density, high in heat conductivity, low in heat expansion coefficient, excellent in polishing performance and the like; the preparation method is short in period, low in sintering temperature, free of sintering shrinking, controllable in finished product performance and capable of adapting to net-size forming of SiC-based ceramic elements in complex shapes.

Description

technical field [0001] The invention belongs to the technical field of composite phase ceramics and its preparation, and in particular relates to a SiC-based composite phase ceramic and a preparation method thereof. Background technique [0002] As a structural ceramic, silicon carbide has many excellent properties such as corrosion resistance, high temperature resistance, high strength, excellent thermal conductivity, and impact resistance. It is widely used in chemical, mechanical, aviation and other fields, and has always been the focus of research in the field of materials. and hotspots. However, ceramic materials are difficult to machine after sintering. People have been looking for a net-size molding method for complex-shaped ceramic components, which has become a key link to ensure the quality of ceramic components and obtain materials with practical application value. [0003] Gel injection molding is a new technology developed on the basis of traditional grouting m...

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Problems solved by technology

[0004] However, carbon black-containing slurries are not suitable for forming silicon carbide structural ceramic components by gel injection molding. The mold initiation system is mainly composed of monomer acrylamide (AM), crosslinking agent N,N'-methylenebisacrylamide (MBAM) and initiator ammonium persulfate (APS), as the raw material carbon black for the preparation of silicon carbide ceramics It will have a bad influence on the gelation process. Carbon black's graphite-like planar structure is responsible for the decomposition of APS • SO 4 - Free radicals have a strong capture effect, which leads to the need for a large amount of initiator to cause decomposition, and the capture effect induces APS to accelerate the decomposition at the same time, resulting in a sharp increase in the concentration of free radicals, and the gel reaction is rapid and uncontrollable. The higher the effect, the more obvious it is, which cannot meet the requirements of the injection molding process.

Due to the existence of this technical problem, the preparation of dense SiC-based ceramics using carbon black-containing slurries has always been a difficulty

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