Showing papers on "Ceramic matrix composite published in 1984"

Process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition

Abstract: A chemical vapor deposition (CVD) process for preparing fiber-reinforced ceramic composites. A specially designed apparatus provides a steep thermal gradient across the thickness of a fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

Gas turbine engine and composite parts

Abstract: High strength, fracture tough, high temperature oxidatively stable, gas turbine engine core engine components are described made of silicon carbide fiber reinforced ceramic matrix or silicon carbide fiber reinforced glass matrix material. A gas turbine engine containing core engine components as above described is also disclosed.

Surface coated Sialon-base ceramic materials for tools

Abstract: A surface coated Sialon-base ceramic material for tools has its surface coated with a hard layer, and exhibits very excellent wear resistance when used in cutting tools and other wear resisting tools. The surface coated Sialon-base ceramic material comprises: a Sialon-base ceramic matrix and at least one hard coating layer formed over the surface of the above matrix, which consists essentially of at least one selected from the group consisting of carbide of Ti, Zr, or Hf, nitride thereof, carbo-nitride thereof, carbo-oxide thereof, and carbo-nitro-oxide thereof, preferably having a mean thickness within a range from 0.5 to 10 μm. The above surface coated Sialon-base ceramic material for tools may further include at least one second hard coating layer formed on a surface of the above first-mentioned hard coating layer, which consists essentially of at least one selected from the group consisting of oxide of Al and nitro-oxide thereof, wherein the first-mentioned hard coating layer exists as an intermediate layer whereas the second hard coating layer exists as a surface layer. Preferably, the second hard coating layer has a mean thickness within a range from 0.5 to 5 μm.

Inorganic Fibres and Composite Materials: A Survey of Recent Developments

Abstract: Inorganic fibres, their manufacture and properties: metal fibres - iire drawing techniques. Melt forming techniques. Carbon fibres - manufacture processes. Post-treatments of carbon fibres. Boron fibres - use of other core materials. Improvements in the CVD process and related apparatus. Polycrystalline refractory oxide fibres - manufacture processes. Composition, properties and applications. Polycrystalline refractory carbide, nitride and boride fibres - chemical vapor deposition. Other fibres - review. New types of fibres developed since 1970. Monocrystalline fibres: growth techniques - growth from the vapor phase. Growth from solutions. Growth from gels. Other techniques. Inorganic fibres composite materials: metal matrix composites - the metal fibre-metal matrix systems. The carbon-, boron-, carbide-, boride-fibre-metal matrix system. Ceramic or glass matrix composites - metal-ceramic systems. Ceramic-ceramic systems. General methods for the manufacture of composite materials - methods based on the combination of preformed fibres with matrix material. Methods involving the in situ generation of fibres. List of cited patents. List of patentees. Subject index.

Method and apparatus for contacting reactants in chemical and biological reactions

Abstract: The present invention is directed to novel methods and apparatus for conducting chemical and biological reactions. A reactor is provided that includes a reaction matrix member formed from microporous ceramic. A chemical or biological material is fixed within the pores of the porous matrix, and reaction solution is passed through the porous matrix member at a controlled rate. Preferably, the matrix member is tubular in shape and comprises a plurality of concentric layers of ceramic material, each layer having a substantially uniform pore size, but the plurality of layers having a progressively decreasing pore size with respect to the preceding layer. Each layer may also have a different thickness than other layers. Reaction solution is introduced into an axial bore through the ceramic matrix member, and the product solution is collected from the outside of the ceramic matrix member. Optionally, lumens within one or more adjacent ceramic layers, and/or spaces between layers can be provided.

Ceramic composite article

Abstract: A carbon film is formed on a ceramic element, or a metal film is formed on the carbon film, and subsequently the ceramic element is bonded to another ceramic or metal element, thereby forming a composite article. The composite article has a high bonding strength and is hardly fractured at joint. Ceramic articles having a surface coating of a hard carbon film or a hard carbon film containing metal grains can also be formed by this process.

Process for the hot-isostatic compression of ceramic shaped parts

Abstract: A ceramic preform is coated with a layer of amorphous carbon and is then hot-isostatically compressed to form the desired ceramic part. The layer of carbon can then be removed.

Manufacture of ceramics

Abstract: Ceramic components are made by forming, prior to sintering, a green ceramic matrix with at least one fibre layer consisting of similar ceramic material in or on the matrix with no, or only partial, infiltration of the matrix material into the fibre layer, and then sintering the matrix and fibre layer together The matrix and fibre layer may be formed together by putting the latter in a mould and slip casting the matrix, or by isostatic pressing the matrix and fibre layer(s) together in a mould Owing to the partially homogeneous union between similar composite materials the reinforcing fibre layer produces a crack-stopping and fragment-containing effect in the event of rupture of the ceramic component

High performance fibers for structurally reliable metal and ceramic composites

Abstract: Very few of the commercially available high performance fibers with low densities, high Young's moduli, and high tensile strengths possess all the necessary property requirements for providing either metal matrix composites (MMC) or ceramic matrix composites (CMC) with high structural reliability. These requirements are discussed in general and examples are presented of how these property guidelines are influencing fiber evaluation and improvement studies at NASA aimed at developing structurally reliable MMC and CMC for advanced gas turbine engines.

High-temperature oxidation of a silicon nitride constructional ceramic

Abstract: An account is given of an investigation into the high-temperature oxidation of a silicon nitride base constructional ceramic. It is shown that the mechanism of the oxidation process for this ceramic depends on temperature. The ceramic is superior in oxidation resistance to similar materials studied earlier.

Ceramic composite article and process for the production thereof

Abstract: A carbon film is formed on a ceramic element, or a metal film is formed on the carbon film, and subsequently the ceramic element is bonded to another ceramic or metal element, thereby forming a composite article. The composite article has a high bonding strength and is hardly fractured at joint.

Particulate and whisker toughened alumina composites

Abstract: Two approaches have recently been examined for achieving an increase in K/sub Ic/ in a ceramic matrix composite system with Al/sub 2/O/sub 3/ as the matrix in both cases. In one approach, studies were conducted to determine if submicron metal particles distributed in the alumina matrix could effectively increase K/sub Ic/. Fracture surface and microstructural analyses of these composites indicated that the observed increases in K/sub Ic/ were due to a relatively large grain duplex microstructure developed in the Al/sub 2/O/sub 3/ during densification. This same duplex microstructure resulted in reduced fracture strength. For the other approach, the concept of utilizing SiC whiskers in a ceramic matrix has been studied and the results in the Al/sub 2/O/sub 3/-SiC whisker system have been particularly encouraging. For the initial experimental work, the composites were hot pressed to essentially theoretical density. In later work, some success has been achieved in pressureless sintering these composites. The SiC whisker reinforced alumina composites were shown to have improved fracture toughness and strength compared to conventional monolithic alumina. For example, at a 20 vol % whisker cencentration, fracture toughness (K/sub Ic/) and flexural strength were 8.3 MPa.m/sup 1/2/ and 650 MPa at room temperature, respectively. Equally important,more » is that these properties remain relatively constant up to temperatures of 1000/sup 0/C.« less

Fabrication of SiC whiskers and composites

Abstract: The Los Alamos Structural Ceramics Program is a multi-faceted program with an overall objective of producing superior strength and fracture toughness in ceramic bodies for load bearing applications. One phase of the program is pursuing the development of silicon carbide whiskers which are used to prepare ceramic matrix composites. The purpose of this work is to investigate strengthening and toughening mechanisms in ceramic composites. In the following we describe some elements of the whisker development program in which we are endeavoring better to characterize the whisker growth process in order to scale up its production potential. We have used these whiskers in the preparation of four types of ceramic matrix representative of a range of materials. The nature and reasons for choosing these materials are described. Composites have been prepared by dry-blending followed by hot pressing which yields high density bodies. In addition we are beginning an investigation of wet processing (slip casting) to produce a silicon-silicon carbide body which will be reaction sintered in nitrogen. Composites of glass-, hot pressed silicon nitride -, and molybdenum disilicide - silicon carbide whiskers have been tested in flexure to determine strength and fracture toughness. Results have been promising, with substantial toughening exhibitedmore » in all systems, and strengthening in the glass and MoSi/sub 2/ composites. The reaction bonded silicon nitride is not yet to the testing stage.« less