# US 4,397,963 A · Method for fabricating cermets of alumina-chromium systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,397,963 A - Document ID: US4397963A - Status: Granted - Kind: A - Application number: 06/308,738 - Filed: 1981-10-05 - Granted: 1983-08-09 - Earliest claimed: 1981-10-05 - Inventors: Chester S. Morgan - Web page: https://patentgrep.com/patent/US4397963A ## CPC - C04B 35/71: Ceramic products containing macroscopic reinforcing agents (C04B35/66 takes precedence {; infiltration of a porous ceramic matrix with a material forming a non-ceramic phase C04B41/00, reaction infiltration with Si in order to form SiC C04B35/573, in order to form Si3N4 C04B35/591}) - C04B 35/111: Fine ceramics - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE ## Abstract Cermet insulators resistant to thermal and mechanical shock are prepared from alumina-chromium systems by providing an Al.sub.2 O.sub.3 material of about 0.5 to 7.0 micron size with a solid-hydrocarbon overcoating by slurring an effective amount of said solid hydrocarbon in a solvent mixture containing said Al.sub.2 O.sub.3 and thereafter evaporating said solvent, contacting said coated Al.sub.2 O.sub.3 with a solution of chromium precursor compound, heating the resulting mixture in a reducing environment to a temperature above the decomposition temperature of said chromium precursor compound but less than the melting temperature of the Al.sub.2 O.sub.3 or chromium for sufficient duration to yield a particulate compound having chromium essentially dispersed throughout the Al.sub.2 O.sub.3, and then densifying said particulate to provide said cermet characterized by a theoretical density in excess of 96% and having 0.1 to 10.0 vol.% elemental chromium metal present therein as a dispersed phase at the boundaries of the Al.sub.2 O.sub.3 material. Cermet components prepared thereby are useful in high temperature equipment, advanced heat engines, and nuclear-related equipment applications where electrical or thermal insulators are required. ## Claims ### Claim 1 A method for fabricating a cermet of Al.sub.2 O.sub.3 /Cr or Cr alloy, characterized by 0.1 to 5.0 vol.% of metal present as a dispersed phase and comprising the steps of: (a) coating a ceramic material with a solid hydrocarbon; (b) contacting said coated material with a solution of a chromium compound; (c) heating said contacted mixture in a reducing environment to a temperature above the decomposition temperature of said chromium compound and less than the melting temperature of the ceramic material for sufficient duration to yield a particulate compound having a discontinuous chromium phase dispersed within a ceramic phase; and (d) densifying said particulate to provide a cermet having 0.1 to 5.0 vol.% chromium or chromium alloy present therein as a dispersed phase largely at the boundaries of the ceramic material grains. ### Claim 2 (depends on 1) The method of claim 1 wherein the Cr metal precursor compound is Cr(NO.sub.3).sub.3 or CrCl.sub.3 and the ceramic material is Al.sub.2 O.sub.3. ### Claim 3 (depends on 1) The method of claim 1 wherein the ceramic material coating of step (a) is provided by slurrying Al.sub.2 O.sub.3 with an organic solvent selected, from the group consisting of hexane, benzene, and toluene, and a suitable amount of solid hydrocarbon compound selected from the group consisting of paraffin, octacosane, and pentatricontane, so as to provide a coating on the Al.sub.2 O.sub.3 of sufficient mass to provide the Al.sub.2 O.sub.3 with about a 7 wt.% net weight gain upon evaporation of the solvent. ### Claim 4 (depends on 1) The method of claim 1 wherein the heating step (c) is carried out within the range of 1000.degree. C. to 1500.degree. C. ### Claim 5 (depends on 1) The method of claim 1 wherein the Cr alloy precursor compound comprises sufficient proportions of chloride or nitrate salts, selected from the group consisting of Cr(NO.sub.3).sub.3, CrCl.sub.3, Ni(NO.sub.3).sub.2, NiCl.sub.2, and mixtures thereof, to produce a cermet particulate mixture having substantially equivalent proportions by weight of Ni and Cr. ### Claim 6 (depends on 1) The method of claim 1 wherein the Al.sub.2 O.sub.3 particle size ranges from about 0.5 to 7.0 microns. ### Claim 7 (depends on 4) The method of claim 4 wherein the reducing environment is about 1.0 to 0.75 atmospheres of hydrogen gas. ### Claim 8 (depends on 1) A thermal shock resistant and electrical insulating cermet producd by the method of claim 1. ### Claim 9 (depends on 8) The article of claim 8 wherein said metal phase is uniformly dispersed as a discontonuous phase through said article.