US 5,296,420 AGranted

Composite refractory materials

AssigneeCommonwealth Scientific and Industrial Research Organization

InventorRonald C. Garvie

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Abstract

A relatively dense composite refractory material which has reasonable strength and good thermal shock resistance comprises an alumina matrix material within which are dispersed particles of polycrystalline zirconia comprises from 1.0 to 40 percent by volume of the composite material. Each particle of zirconia is an agglomerate of microcrystals which are strongly bonded together. Due to the agglomerates of the bonding together of the microcrystals at their grain boundaries. The microcrystals contain no matrix material within their agglomerates, and exhibit strong thermal expansion anisotropy. They have a size such that cracks do not form spontaneously within the agglomerates during cooling from about 1600.degree. C. to room temperature. Typically the agglomerates have a mean diameter of from 10 to 15 micrometers, while the average diameter of the microcrystals in an agglomerate is from 1 to 2 micrometers.

Claims10

Dependent claims

A composite alumina/zirconia refractory material comprising an alumina matrix with particles of zirconia dispersed therein, said composite material having been formed by die pressing a mixture of alumina powder and the zirconia particles, followed by sintering in the absence of applied pressure at a temperature of about 1600.degree. C., said composite material having a porosity which does not exceed 12 percent, wherein the particles of zirconia

(a) occupy from 1.0 percent by volume to 40 percent by volume of the composite refractory material;
(b) each comprise a polycrystalline agglomerate of microcrystals with no matrix material within the agglomerate, the microcrystals (i) being strongly bonded together, (ii) exhibiting a strong thermal expansion anisotropy, and (iii) having a size such that cracks do not form spontaneously within the agglomerate during cooling from a temperature of about 1600.degree. C. to room temperature;
and
(c) each have a mean diameter of from 10 to 15 micrometers, with the microcrystals therein having a mean diameter of from 1 to 2 micrometers.

1 more element

Dependencies are inferred from the claim text.