Abstract: Novel monodispersed crystalline mixed metal layered hydroxide compounds of the general formula are prepared:Li.sub.m D.sub.d T(OH).sub.(m+2d+3+na) A.sub.a.sup.n, where m is an amount from zero to 1; D is a divalent metal; d is the amount of D ions of from zero to 4; T is a trivalent metal; A represents anions or negative-valence radicals of valence n; na is from zero to -3; (m+d) is greater than zero; and (m+2d+3+na) is equal to or greater than 3. The D metal is preferably Mg and the T metal is preferably Al. These compounds are useful as gelling agents which impart beneficial thixotropic properties to various fluids, such as drilling fluids, especially when employed along with fluid loss agents.

Abstract: A composition comprised ofI. 60 to 90% wt. of(a) from 70 to 95 weight percent of at least one of(i) one or more MgAl.sub.2 O.sub.4 spinels heated at a temperature of about 600.degree. C. to about 1700.degree. C. and having less than 20% by weight of segregated phases of Al.sub.2 O.sub.3 or MgO;(ii) MgAl(OH).sub.5-ny X.sub.y.sup.n where y.ltoreq.1; x=OH.sup.-, halogen, SO.sub.4.sup.=, NO.sub.3.sup.- carboxylate, halogenated carboxylate, H.sub.2 PO.sub.4.sup.-, HPO.sub.4.sup.=, HCO.sub.3.sup.-, and the like which is prepared by coprecipitating a Mg and Al salt under controlled pH and Mg/Al ratios and which may also include segregated phases of AlO(OH), Mg(OH).sub.2 and/or Al(OH).sub.3 following pH adjustment;(iii) intermediates of (1) and (2) prepared by partial calcination of (2) at temperatures .gtoreq.300.degree. C. but .ltoreq.600.degree. C.

Abstract: A spinel containing slip-casting composition, method for preparing the spinel slip-casting composition and method for casting the slip into usable forms are described. The spinel employed to prepare the castable slips is a pre-calcined spinel and a calcined spinel each 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. 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mold porous to water until the desired thickness of solid has been obtained and the excess "slip" decanted or otherwise withdrawn from the mold. 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 50 and 99 percent of theoretical.