Showing papers on "Ceramic matrix composite published in 1976"

Ceramic-matrix composites

Abstract: Ceramic materials often exhibit a combination of useful physical and mechanical properties, including high refractoriness, but their applications are restricted due to their brittle behaviour; in an attempt to improve the strength, and particularly the toughness, of brittle ceramics particle-strengthening and fibre-reinforcement have been utilized, with limited success. The factors which affect the mechanical properties of these composite systems are discussed, and the various experimental systems that have been investigated are reviewed. It is concluded that, although the potential applications of such materials are extremely diverse, several important aspects, particularly the effect that matrix microcracking may have on the mechanical and thermal stability of reinforced-ceramic systems, must be fully evaluated before ceramic-matrix composites can seriously be considered as useful replacements for more conventional materials.

Method for dip-coating ceramic with molten silicon

Abstract: It is desirable to coat large area, thin sheets of large-grain polycrystalline silicon on an inexpensive ceramic substrate for use in solar cell applications and the like. Such ceramic substrates as are used are chosen from those having thermal expansion coefficients similar to those of silicon. The ceramics meeting these requirements, for example mullite, alumina and zirconia, when brought into contact with molten silicon, however, are not wet by the silicon and no coating takes place. In this invention the method of coating includes the step of carbonizing the surface of such a substrate and then contacting the carbonized surface of the ceramic with the molten silicon, whereupon a large-grain silicon coating is produced wherever the ceramic is carbonized. In this way the ceramic of the type which is not wet by molten silicon can be successfully coated with silicon.

Ceramic nuclear waste forms. II. A ceramic-waste composite prepared by hot pressing

Abstract: A feasibility study has been conducted to determine whether nuclear waste calcine and a crystalline ceramic matrix can be fabricated by hot pressing into a composite waste form with suitable leaching resistance and thermal stability. It was found that a hard, dense composite could be formed using simulated commercial fuel reprocessing waste and a matrix of ..cap alpha..-quartz with a small amount of a lead borosilicate glass added as a consolidation aid. Its density, waste loading and leaching resistance are comparable to the glasses being considered for fixation of nuclear wastes. The hot-pressed composite offers a closer approach to thermodynamic stability and improved thermal stability (in monolithic form) compared with glass waste forms. Recommendations for further optimization of the hot-pressed waste form are given.