Champion Spark Plug Company

Cooper Industries, Inc.

Francis H Dulin

A semi-conducting ceramic is disclosed. The ceramic consists essentially of from 50 percent to 72 percent of silicon carbide particles, from 25 percent to 47 percent of silicon nitride particles and a modified silicon oxynitride glass bonded to the silicon carbide particles and bonding the silicon nitride particles together. An improvement in a method for producing an article which comprises silicon carbide particles dispersed in a matrix is also disclosed. The method includes the step of firing or sintering the article to convert the matrix to a densified ceramic with the formation of a liquid phase. The improvement involves embedding the article, prior to firing, in a cover material which contains powdered silicon and maintaining a nitrogen or an inert atmosphere in contact with the cover material during firing. The amount of silicon in the cover material and the composition of the atmosphere are such that the silicon carbide particles are protected against oxidation.

Semi-conducting ceramic

A fired, electrically semi-conducting ceramic body is disclosed. The body consists essentially of silicon carbide particles having a median particle size from about 3 to about 25 microns dispersed in a bonding matrix. The silicon carbide particles constitute from about 50 to about 70 percent of the body. The body has an 'apparent porosity' as subsequently defined herein from 20 to 40. The production of such a body from a batch composed of silicon carbide, alumina, silica and at least one oxide, carbonate or hydroxide of calcium, magnesium, barium or strontium is also disclosed. The batch is milled and pressed into a shape, and the resulting shape is then fired in an inert gas atmosphere to a temperature from about 2,300.degree. to 2,800.degree. F. for a time sufficiently long to produce a semi-conductor body having the requisite apparent porosity of from 20 to 40 percent.

Electrically semi-conducting ceramic body

A method for producing a semi-conductor body is disclosed. The batch for the body is silicon carbide and reactive alumina. The batch is first dry ball milled with from 1/2 to 2% fatty acid and pressed into a shape. The shape is then fired either in air below 2300.degree.F. or in an inert gas atmosphere to a temperature from about 2000.degree. to 3000.degree.F., and for a time sufficiently long to produce a semi-conductor body having a specified apparent porosity. An impregnation step is also disclosed to achieve the specified apparent porosity.

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Rochester Hills, MI, United States of America

Francis H Dulin