The Dow Chemical Company

Stanley J Morrow

Walter W Henslee

John S Lindsey

Christopher P Christenson

William M Eckert

John N Periard

Hans H Schwantje

Charles R Whitworth

Dale M Bertelsman

There is disclosed a unique substantially non-reactive refractory material suitable for use as a material of construction for various component parts of an electrolytic light metal, particularly magnesium, production cell. The non-reactive refractory material is comprised of a magnesium aluminum spinel. When used in block form the blocks may be joined together by use of a phosphate-spinel mortar.

Magnesium aluminum spinel in light metal reduction cells

Several methods are set forth for preparing polymetallic spinels by coprecipitating two or more metal compounds in a proportion to provide a total of eight positive valences when combined in the oxide form in the spinel crystal lattice. The methods disclosed require coprecipitation of the metals in the hydroxide form or convertible to the hydroxide-oxide form, calcining the coprecipitate, and finally sintering the calcined material at about one-half its melting point or greater, thereby forming a spinel which has a density of greater than 50 percent of the theoretical density of spinel crystal. Also disclosed are techniques for preparing spinels having more than two metals incorporated into the spinel lattice, as well as a separate oxide phase associated with the spinel crystallites, and slipcasting compositions.

Magnesium aluminum spinels

A spinel containing slip-casting composition, a method for preparing the spinel slip-casting composition and a method for casting the slip into usable forms are described. The spinel employed to prepare the castable slips is a pre-calcined spinel prepared in the manner of copending application Ser. No. 184,189, filed Sept. 4, 1980, which is ball-milled with water, then mixed with a deflocculant at pH 9 or below and optionally with a molding aid. The slurry or 'slip' is cast into a mold porous to water until the desired thickness of solid has been obtained and the excess 'slip' decanted or otherwise withdrawn from the mold i.e., drain cast method or the 'slip' is solid cast and dried to produce a green solid casting. The green shape is retained in the mold until it gains green strength, 1 hour to 5 days, and thereafter placed in an oven wherein it is fired to above about 1400.degree. C. for from 1 to 20 hours until it has reached its maximum density of between about 55 and 99 percent of theoretical. Also disclosed are mixtures of pre-fired spinels with calcined spinels of various heat histories to yield more durable green forms. In addition there is disclosed slips prepared from mixtures of different spinel compositions.

Spinel slip casting composition and articles

A method for preparing spinel (MgAl.sub.2 O.sub.4) surfaces on alumina or alumino silicate articles or shapes by exposure of the article or shape to molten or vaporous magnesium or magnesium alloy for from two to ten hours under nonpyrophoric conditions.

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Clute, TX, United States of America

Stanley J Morrow