Champion Spark Plug Company

Cooper Indusries, Inc.

Champion Spark Plug

William R Manning

Terrence K Brog

A method for producing a ceramic is disclosed. The method involves comminuting a batch composed of from 6 to 95 percent of particulate ZrO.sub.2 and from 5 to 94 percent of particulate Al.sub.2 O.sub.3. A part of the particulate ZrO.sub.2 is in a metastable tetragonal crystal structure, for example, as a consequence of 3.sup.m/o of Y.sub.2 O.sub.3 dissolved therein and a part has a monoclinic crystal structure. The comminuted batch is compacted into a shape, and the shape is fired. The degree of comminution of the batch, the firing conditions and the proportions of stabilized and monoclinic ZrO.sub.2 in the batch are controlled to produce a dense, gas impervious ceramic which contains both metastable tatragonal and monoclinic ZrO.sub.2, and in such proportions that the ceramic has improved strength by comparison with an otherwise identical ceramic wherein all of the ZrO.sub.2 is in either a metastable tetragonal or a monoclinic crystal structure. Also disclosed is a method where the particulate alumina can be an alumina-chromia solid solution containing up to 50.sup.m/o of chromia. In another embodiment, a ceramic article is disclosed. The article is composed of from 6 to 95 percent of particulate ZrO.sub.2, from 5 to 94 percent of particulate Al.sub.2 O.sub.3, from 1/4 to 33/4 percent of MnO.sub.2 and from 1/4 to 33/4 percent of TiO.sub.2 .

Alumina-zirconia ceramic

A ceramic article is disclosed. The article is composed of from 6 to 50 percent of particulate ZrO.sub.2 having an ultimate particle size less than 2 .mu.m, from 50 to 94 percent of particulate Al.sub.2 O.sub.3, from 1/4 to 3 percent of MnO.sub.2 and from 1/4 to 3 percent of TiO.sub.2.

A ceramic consisting essentially of from 1 to 15 percent of glass and 99 to 85 percent of a mixture of particulate Al.sub.2 O.sub.3 and particulate ZrO.sub.2 is disclosed. ZrO.sub.2 is present in a sufficient amount usually from 1/4 to 6 percent base on the of the ZrO.sub.2 and Al.sub.2 O.sub.3, to strengthen the ceramic significantly, by comparison with an otherwise identical ceramic where the particulate ZrO.sub.2 is replaced either by the glass or by particulate Al.sub.2 O.sub.3. The glass constitutes a vitreous phase bonding the particulates into a dense, gas impervious structure, and can be a calcium magnesium silicate glass containing from 45 to 80 percent of SiO.sub.2, from 8 to 55 percent of CaO and MgO, and not more than 15 percent of Al.sub.2 O.sub.3.

A ceramic composed of 1 to 15 percent of glass and 99 to 85 percent of a mixture of particulates is disclosed. The glass, present as a vitreous phase bonding the particulates into a dense, gas impervious structure, contains 45 to 80 percent of SiO.sub.2, 8 to 65 percent of CaO and MgO and not more than 15 percent of Al.sub.2 O.sub.3. The particulates, which are finer than 15 microns in ultimate particle size, include Al.sub.2 O.sub.3 and at least one of ZrO.sub.2, HfO.sub.2 and solid solutions of the two. The ceramics are subject to microcracking, which can be cured by refiring, or prevented by including particulate Y.sub.2 O.sub.3 as a stabilizer.

Alumina ceramic comprising a siliceous binder and at least one of

A method for producing a dense and impervious stabilized hafnium oxide ceramic having zero percent water absorption is disclosed. The hafnium oxide is stabilized in the sense that a solid solution with Y.sub.2 O.sub.3 is formed. The solid solution has a cubic crystal structure which, because of its similarity to the structure of the mineral fluorite, is sometimes called a 'fluorite phase'; unlike hafnium oxide alone, which undergoes a destructive phase transformation from tetragonal to monoclinic during cooling, the cubic structure of the solid solution remains stable during cooling of a ceramic article. The ceramic is made by producing an intimate dry mixture consisting essentially, on an oxide basis, of hafnia, yttria and at least one oxide selected from the group consisting of silica, alumina, calcia, magnesia, baria and strontia, yttria constituting substantially 8 to 12 mole percent of said article based upon the total number of moles of hafnia and yttria, and silica, alumina, calcia, magnesia, baria and strontia constituting from 1/4 percent to 4 percent, based upon the weight of hafnia and yttria, with the proviso that calcia, magnesia, baria and strontia constitute not more than 70 percent by weight of the total of silica, alumina, calcia, magnesia, baria and strontia, pressing the dry mixture into a predetermined shape, and sintering the shape to a gas impervious condition at a temperature from 2700.degree. F. to 3000.degree. F. A stabilized, dense, hafnium oxide ceramic has the capability of conducting oxygen anions, a requisite of the solid electrolyte in an oxygen concentration cell. Such a cell can be used as an oxygen sensor in apparatus for controlling the operation of an internal combustion engine to maintain substantially the stoichiometric air-fuel ratio. When the air-fuel ratio is closely controlled, a three-way catalytic converter can be used to control emissions of hydrocarbons, CO and NO.sub.x within the limits presently specified for 1978.

Growing community of inventors

Richmond, MI, United States of America

William R Manning