Porous carbon preform for reactive sintering, as well as preparation method and application thereof

Abstract

The invention discloses a porous carbon preform for reactive sintering, as well as a preparation method and application thereof. The porous carbon preform is obtained by taking charcoal powder as a carbon source, taking lignocellulose as a pore-forming agent, taking a modified polyester type high molecular compound as a dispersant, taking camphene as a dispersion medium, adding a certain amount of ethyl ether, performing constant-temperature ball milling at the temperature of 55 DEG C to obtain material slurry, performing vacuum degassing, then pouring and forming the material slurry at room temperature, subliming till constant weight, and carrying out biscuit firing at the temperature of 900-1550 DEG C for 0.5-2h. The porous carbon preform prepared by the method disclosed by the invention has the advantages of controllable density and porosity, uniform pore structure, no defects and the like, and has great reactive sintering performance; reaction sintered silicon carbide generated by high-temperature silicon impregnation reaction has no black cores, cracking, delamination and other defects, and has good mechanical properties.

Description

technical field [0001] The invention relates to a porous carbon preform and its preparation method, in particular to a porous carbon preform for reaction sintering, its preparation method and its application in preparing silicon carbide. Background technique [0002] The preparation of reaction-sintered silicon carbide by impregnating porous carbon preforms with molten silicon is a very competitive technology, which has the advantages of less residual silicon, high flexural strength, and low cost. However, during the siliconizing process, the reaction between the carbon in the porous carbon preform and the molten silicon is very violent, and the porous carbon preform has a dramatic volume expansion effect during the siliconizing reaction, which easily leads to reaction sintering of silicon carbide. Defects such as black centers, cracks, and delaminations appear. Therefore, the preparation of porous carbon preforms is very important, and the density of porous carbon preforms ...

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Problems solved by technology

[0003] At present, the methods for preparing porous carbon preforms mainly include the chemical synthesis phase separation pyrolysis method invented by Hucke (Hucke, Hucke E E. Methods of producing carbonaceous bodies and the products there of. U.S. Pat. No. 3859421, Jan. 7, 1975.), this method can precisely control the density and pore structure of the porous carbon preform, so that the porous carbon preform with uniform structure can be obtained. The flexural strength can reach 800MPa, but this method involves complex physical and chemical processes, the preparation parameters are not easy to control, the preparation cost is high, and industrial production has not been realized

[0004] The wood pyrolysis framework method is a traditional method for preparing porous carbon preforms. This method can accurately replicate the natural structure of wood and prepare porous carbon preforms with biological forms. At the same time, it does not involve complex physical and chemical reactions, and the preparation cost It is also lower than the chemical synthesis phase separation pyrolysis method invented by Hucke, but during the pyrolysis process of wood, the deformation and cracks caused by uneven material density and burning loss greatly affect the quality of porous carbon prefabricated body

[0005] Chinese patent application 00114425.1 "Method for manufacturing reaction-sintered silicon carbide ceramic materials by one-step process of pure carbon powder water-based dispersion" adopts industrial carbon and graphite powder as carbon source, water as dispersion medium, adding dispersant, binder, plasticizer agent, defoamer, etc. After ball milling, carbon slurry is prepared. The slurry is prepared by wet molding processes such as grouting and extrusion to produce a green body. Up to 400MPa, density 3.0g / cm 3 reaction sintered silicon carbide products, the preparation process of this method is simple and feasible, the preparation cost is low, and it is easy to realize industrial production. Pyrolysis, it is easy to introduce defects such as cracks and delamination in the green body, and the pore structure in the green body is not easy to control

This technology uses charcoal powder as a carbon source, camphene as a dispersion medium, and adds a certain amount of dispersant. The room temperature condensation casting molding method introduced in this invention can be practiced to prepare a porous carbon prefabricated body. After the silicon reaction, the obtained reaction sintered silicon carbide has fatal defects such as black cores, cracks and delaminations, which are difficult to meet the actual use requirements

It can be seen that the porous carbon prefabricated body suitable for reaction sintering cannot be prepared by simply adopting this molding method, and it is necessary to change the preparation method

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