Preparation method of compact silicon carbide ceramic

Abstract

The invention discloses a preparation method of compact silicon carbide ceramic, which is characterized in that the compact accumulation among silicon carbide crystalline particles is realized so as to obtain a polycrystalline block ceramic with high compactness by using decomposition and chemical combination reactions generated by pure silicon carbide or a material source of silicon carbide at the temperature of 2,250-2,500DEG C, wherein the material source of silicon carbide is generated by a chemical combination reaction, adopting a high-temperature physical gaseous phase transmission technology and controlling the gaseous phase recrystallizing and arraying accumulation process. For the compact silicon carbide ceramic prepared by the method, crystals are directly bonded by pure silicon carbide interfaces, silicon carbide crystalline particles are directionally arrayed and compactly accumulated according to the preferred orientation of crystals and the volume density of the ceramic can approach to the theoretical density.

Description

technical field [0001] The invention relates to a preparation technology of high-strength and dense silicon carbide ceramics used in the fields of structural ceramics, bulletproof materials, optical devices and invisible wave-absorbing surface materials. Background technique [0002] Silicon carbide material has high thermal conductivity, low thermal expansion coefficient, extremely high high temperature strength and hardness, excellent thermal shock resistance, creep resistance, and wear resistance. Silicon carbide has semiconductor characteristics, has the characteristics of negative temperature coefficient, high chemical stability, is insoluble in common acids and mixed acids, does not react with boiling hydrochloric acid, sulfuric acid, hydrofluoric acid, etc. It has broad application prospects in chemical industry, environmental protection and other related industrial fields. [0003] At present, the main process methods for obtaining dense silicon carbide ceramics are...

AI Technical Summary

Problems solved by technology

Although there are no open pores, silicon residues and carbon inclusions inevitably occur in silicon carbide products prepared by reaction sintering of carbon blanks, which affect the use of materials in high temperature environments

Chinese patent documents 200610136881.5, 95100358.5, 92109201.6, 87206878 and other silicon carbide products obtained by recrystallization methods do not have a large number of second phase inclusions, but the proportion of residual pores is relatively high and the strength is low

In terms of sintered density and flexural strength indicators, pressureless sintered and pressure sintered silicon carbide are relatively high, as shown in the literature [Journal of Harbin University of Science and Technology, 2002, 7 (2) 80-83; Journal of Silicates, 2008, 36( 11) 1629~1632; Acta Silicate, 1981, 9(2) 133~143], etc., in the preparation process, boron and boron compounds, carbon black, alumina, yttrium oxide, calcium fluoride, etc. need to be added as sintered Auxiliary, through pressure molding or pressure sintering, the product produced is doped with a large amount of non-silicon carbide second phase, the sintering shrinkage is large, the preparation process is complicated and it is difficult to obtain special-shaped products

[0004] As the application of vapor deposition process of silicon carbide such as Chinese patent literature 200480040597.7, 200610076993.6, 200710177781.1, 200810071049.0; literature [Journal of Northwestern Polytechnical University, 2001, 19 (2) 165~168] etc. adopt silicon-containing gas (such as silanes) and carbon Similar gases (such as methane) are used as raw materials to prepare thin films, the size of the product and the deposition thickness are limited, the production cost is high, the deposition speed is slow (80 microns / hour), the production efficiency is low, and it is only used for surface materials; Chinese patent document 200810081741.1 proposes A variety of manufacturing methods of chemical vapor deposition silicon carbide products have been proposed, but they are only applied to the joint connection and surface deposition modification of silicon carbide products; The nucleation of crystals affects the quality of single crystals, and the deposition temperature is generally high, so there is also the problem that the deposition rate is slow and it is difficult to obtain high-density and complex-shaped ceramic products

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