Monolithic SiC Research Articles

Mechanical Properties of SiC-Matrix Composite Reinforced with Dispersed Graphite Microcrystals

Silicon carbide containing 5-15wt% graphite was fabricated by hot-pressing at 2000°-2300°C using carbon black as a starting carbon material. B4C of 1wt% was doped in SiC as a sintering aid before mixing with carbon black. X-ray diffractometry and SEM revealed that the grain growth of SiC was suppressed by the carbon addition, and that carbon black changed to graphite microcrystals. Carbon addition increased the flexural strength of the composite appreciably. The composite with 10% graphite had the average strength of 820MPa and the maximum value of 1000MPa. The fracture toughness of 4.5MPa √m for the 10% graphite composite was obtained, as compared with 3.3MPa √m for monolithic SiC.

EVALUATION OF SIC MATRIX COMPOSITES FOR HIGH TEMPERATURE APPLICATIONS

Abstract SiC matrix composite components have been fabricated by infiltrating and overcoating fiber preforms of graphite, alumina, and SiC via chemical vapor deposition (CVD). The degree of CVD densification could be controlled to yield vacuum tight components as well as porous open mesh structures where only the fiber was coated. These components have been fabricated in a wide variety of shapes including baskets, tubes and corrugated panels. The CVD process has been successfully scaled up to produce panels 80 cm by 80 cm. The morphology, chemistry, and geometry of the fiber was found to have a significant effect on the deposition process. Thus, process conditions had to be modified based on the fiber being infiltrated. These components were subjected to 1400 C temperature treatments including operation in gas-fired furnaces. After 2000 hours of testing in a gas-fired furnace at 1300 C, the SiC composite tubes have remained intact and un cracked. This suggests that the monolithic SiC coating is the contro...

SiC matrix/SiC fiber composite: A high-heat flux, low activation, structural material

A process for producing a high-strength, high-density SiC matrix/SiC fiber composite material has been developed. Fibers are woven, braided, or unidirectionally wound into a preform which is then impregnated with SiC matrix by chemical vapor infiltration (CVI). The primary features of this new material are its composite fracture characteristics — high strain-to-failure and high fracture toughness - as contrasted with the brittle fracture characteristics of monolithic SiC. This material holds promise as a low activation structural material for applications requiring high temperature, high heat flux capability.