Cooper Industries, Inc.

Champion Spark Plug Company

Jow-Lay Huang

A method for producing a sintered reaction bonded silicon nitride insulator is disclosed. The method comprises mixing powdered silicon having an average particle size not greater than 5 .mu.m with from 3 to 7 percent each of MgO and CeO.sub.2, pressing a shape from the resulting mixture, calcining the shape, grinding the calcined shape to a desired contour, and heating the ground shape in a nitrogen atmosphere at a pressure of about 1 atmosphere absolute. The MgO and CeO.sub.2 serve as sintering aids. Other suitable sintering aids include 2 to 8 percent of Y.sub.2 O.sub.3, 6 percent of Y.sub.2 O.sub.3 and 2 percent of Al.sub.2 O.sub.3, and 2 to 8 percent of MgO, BeO, HfO.sub.2 or Zr.sub.2 O.sub.2. The heating of the ground shape is controlled, until a reaction bonded Si.sub.3 N.sub.4 body is produced in which at least 99 percent of the Si in the initial charge is reacted to Si.sub.3 N.sub.4, so that reaction between nitrogen and the ground shape is substantially complete at any given temperature before the shape is heated above that temperature, and, thereafter, to produce a sufficient amount of a cerium-magnesium silicate glass to produce a Si.sub.3 N.sub.4 body having from 85 to 90 percent of theoretical density.

Production of a sintered reaction bonded silicon nitride insulator

A method for producing a sintered reaction bonded silicon nitride ceramic reinforced with silicon carbide whiskers is disclosed. The method comprises mixing powdered silicon having an average particle size not greater than 5 .mu.m with from 3 to 7 percent each of MgO and CeO.sub.2 and from 10 to 35 percent of silicon carbide whiskers, from 15 to 50 percent of silicon nitride or from 10 to 35 percent of silicon carbide whiskers and from 15 to 50 percent of silicon nitride, pressing a shape from the resulting mixture, and heating the shape in a nitrogen atmosphere at a pressure of about 1 atmosphere absolute. The MgO and CeO.sub.2 serve as sintering aids. Other suitable sintering aids include 2 to 8 percent of Y.sub.2 O.sub.3, 6 percent of Y.sub.2 O.sub.3 and 2 percent of Al.sub.2 O.sub.3, 2 to 8 percent of MgO, BeO, HfO.sub.2 or ZrO.sub.2 and 1 to 5 percent of CaO. The heating of the ground shape is controlled, until a temperature is reached at which it has previously been determined that the consumption of nitrogen by reaction between silicon of the shape and nitrogen is complete so that reaction between nitrogen and the shape is substantially complete at any given temperature before the shape is heated above that temperature, and therafter the shape is heated rapidly to produce, by reaction involving the sintering aid, a sufficient amount of a glass to produce a Si.sub.3 N.sub.4 body having from 65 to 85 percent of theoretical density.

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Troy, MI, United States of America

Jow-Lay Huang