High-strength Reaction-sintered Silicon Carbide Research Articles

Strengthening Mechanism of High-Strength Reaction-Sintered Silicon Carbide

A newly developed high-strength reaction-sintered silicon carbide (SiC), which has two or three times higher strength than conventional sintered SiC, is one of the most promising candidates for lightweight substrates of optical mirrors, because of its fully dense structure, small sintering shrinkage ( < 0.5 %), good shape capability, and low sintering temperature. In this paper, in order to improve the performance of the newly developed reaction-sintered SiC, the effect of the microstructure on the bending strength was investigated by focusing on a physical fracture model using observations from transmission electron microscopy and X-ray stress measurement. As a result, it was confirmed that the bending strength of the newly developed reaction-sintered SiC could be improved by reducing the size of residual silicon. The strengthening mechanism of the newly developed reaction-sintered SiC was assumed to be due to piled-up dislocations at the grain-boundary of residual silicon sites, based on Stroh’s fracture model of polycrystalline solids.

Evaluation of Microstructure of High-Strength Reaction-Sintered Silicon Carbide

A newly developed high-strength reaction-sintered silicon carbide (SiC), which has two or three times higher strength than the normal sintered SiC, is one of the most promising candidates such as the lightweight substrate of optical mirror, because of fully dense, small sintering shrinkage (±1%), good shape capability and low sintering temperature. In this paper, in order to improve the performance of newly developed reaction-sintered SiC, the microstructure was investigated by paying attention to the crystal structures using the observation of transmission electron microscope and X-ray diffraction analysis. As a result, it made clear that the finer-scale microstructure could be observed as consisting of large particles (~1m in diameter) of starting powder -SiC and small particles (~1m in diameter) of -SiC formed during the reaction (Si+CSiC) with the residual silicon filling the remaining porosity. Also, it was identified that the -SiC formed during the reaction referred to the cubic (3C) polytype and the -SiC of starting powder referred to the hexagonal (6H) polytype.

Evaluation of Microstructure for High-Strength Reaction-Sintered Silicon Carbide

A newly developed high-strength reaction-sintered silicon carbide (SiC), which has two or three times higher strength than the normal sintered SiC, is one of the most promising candidates such as the lightweight substrate of optical mirror, because of fully dense, small sintering shrinkage (±1%), good shape capability and low sintering temperature. In this paper, in order to improve the performance of newly developed reaction-sintered SiC, the microstructure was investigated by paying attention to the crystal structures and the interface of each crystals using the observation of transmission electron microscope and X-ray diffraction analysis. As a result, it made clear that the finer-scale microstructure could be observed as consisting of large particles (∼1μm in diameter) of starting powder α–SiC and small particles (

ELID Grinding Properties of High-Strength Reaction-Sintered SiC

The high-strength reaction-sintered silicon carbide (RS-SiC) developed by TOSHIBA is one of the most excellent materials for large-scale space-borne optics. The bending strength of the high-strength RS-SiC is two times higher than other SiC ceramics. The purpose of this study is to investigate the ELID grinding properties of the high strength RS-SiC. Two types of metal bond diamond wheels (cup type and straight type) were used to grinding tests. The ground surface properties, such as roughness, subsurface damage and micro-step were made clear by measurement or observation. It was confirmed that, both the surface roughness and the depth of micro-step produced by cup-wheel were lower than those produced by straight-wheel. When a #20000 grit sized cup-wheel was used, a considerably high quality mirror surface (Ra<0.8nm) can be achived.

Effect of heat treatments on bending strength of high-strength reaction-sintered silicon carbide

Effect of heat treatments on bending strength of high-strength reaction-sintered silicon carbide

Development of mirror of 250mm in diameter for high-strength reaction-sintered silicon carbide

Development of mirror of 250mm in diameter for high-strength reaction-sintered silicon carbide

Development of high-strength reaction-sintered silicon carbide

Reaction sintering is one of the most attractive manufacturing processes of silicon carbide (SiC), because of dense structure, low processing temperature, good shape capability, low cost and high purity. However, mechanical properties of reaction-sintered SiC (RS-SiC) were typically much lower than normal sintered one. Particularly, the bending strength was approximately 300 MPa. In this study, in order to develop the high-strength RS-SiC, effect of the microstructure on the bending strength was examined. The bending strength of RS-SiC was recognized to be increased with decreasing the residual silicon (Si) size, and high-strength RS-SiC has been newly developed. The strength over 1000 MPa was obtained to control the residual Si size under 100 nm. Some other properties of developed high-strength RS-SiC were also evaluated.

Fabrication of Joing of High-Strength Reaction Sintered Silicon Carbide

Fabrication of Joing of High-Strength Reaction Sintered Silicon Carbide

Development of High-Strength Reaction-Sintered Silicon Carbide

Reaction sintering is one of the most attractive manufacturing processes of silicon carbide (SiC), because of dense structure, low processing temperature, good shape capability, low cost and high purity. However, mechanical properties of reaction-sintered SiC (RS-SiC) were typically much lower than normal sintered one. Particularly, the bending strength was approximately 300 MPa. In this study, in order to develop the high-strength RS-SiC, effect of the microstructure on the bending strength was examined. The bending strength of RS-SiC was recognized to be increased with decreasing the residual silicon (Si) size, and high-strength RS-SiC has been newly developed. The strength over 1000 MPa was obtained to control the residual Si size under 100 nm. Some other properties of developed high-strength RS-SiC were also evaluated.

Development of High Strength Reaction-Sintered Silicon Carbide.

In reaction-sintered silicon carbides, usually 10-40vol% of the residual silicon phase remains after the reaction-sintered process. For this reason, the bending strength of reaction-sintered silicon carbides decreases to or below 300MPa. The raw material composition (C/SiC) and the starting particle size were optimized in order to decrease the volume fraction of residual silicon and the SiC grain size. There was a tendency for the strength to increase with decreasing the residual silicon size. The strengthening effect may be attributed to the reduced residual silicon size. A reaction-sintered silicon carbide with a high bending strength of 1000MPa could be developed by the present optimization method.