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The melt infiltration technology of General Electric Corporation, Schenectady, New York, produces CFCCs composed of continuous silicon carbide fibers in a matrix of silicon carbide and silicon. The composite is made by a silicon melt infiltration process in which densification takes place in a matter of minutes. A boron-nitride-based coating is applied to the fiber. It provides fiber pull-out and protects the fiber from the molten silicon during the infiltration step. The coated fibers are pulled through a liquid mixture containing polymers and fillers and wound onto a drum to produce unidirectional plates.

The composite preform plates are loaded into a vacuum furnace while in contact with silicon. Initial heating of the preform to 500-600°C (932°-1112°F) is done slowly to allow burnout of any binders, leaving a body of 35-40% porosity. Heated above 1410°C (2570°F), the silicon melts and infiltrates the porous preform by capillary action. No external pressure is required. During infiltration the silicon reacts with the any free carbon in the preform (incorporated as a particulate in the matrix slurry or from pyrolysis of a binder constituent) to form silicon carbide. Any residual porosity is filled with silicon. The overall infiltration process is near net shape, with less than 0.5% change in preform dimensions.

The plates are cut into tapes, stacked, and pressed by die pressing, compression molding, vacuum bagging, or autoclaving to form a laminated composite. This process is also used to form silicon carbide/alumina CFCCs and alumina/alumina CFCCs when aluminum is used in place of silicon. An aluminum oxide matrix is grown through a silicon carbide fiber preform. The fiber preform is first coated with a boron nitride/silicon carbide dual layer. The boron nitride is derived from boron chloride, ammonia, and hydrogen. The silicon carbide is derived from methyltrichlorosilane. Both coatings are deposited employing CVI. These coatings protect fibers from the molten aluminum, and the silicon carbide coating wets the fiber to facilitate infiltration of the aluminum. When molten aluminum metal is placed in contact with the silicon carbide fiber preform, it oxidizes in the presence of air at elevated temperatures and forms a matrix that is rich in aluminum oxide. Residual aluminum, present in the matrix as microscopic interconnected channels, is removed from the CFCC.

Amercom, Chatsworth, California, pioneered a CFCC process employing liquid infiltration of preforms with preceramic polymers, and phenolic resin, as a way of rigidizing the preform in the first-stage of CVI. This eliminates the need for graphite tooling to hold and configure the fiber-reinforced preform during the initial rigidization and densification steps. Instead, aluminum or other metal tooling can be used repeatedly and requires heat up to only 204°C (400°F). The batch-processing capacity of a reactor for the early CVI processing stages are increased by 300% or more. This technology is owned by COI Ceramics, Incorporated.

A process of Allied Signal Ceramic Components, Torrance, California, illustrates the versatility of ceramic composite chemistry. The process results in a carbon fiber-reinforced silicon nitride ceramic composite. Cold isostatic pressing is used to form the composite. Glass encapsulation and hot isostatic pressing are employed to densify it. Silicon nitride provides excellent mechanical properties and resists corrosion. The carbon fiber provides self-lubrication and toughness.

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