Abstract: Printed circuit board laminates which have improved thermal stability. The improved properties are attributed to the use of a novel aluminium hydroxide which is described by the molecular representation: Al2O3.nH2O where n>2.6 and <2.9.

Abstract: The present invention relates to an aqueous suspension comprising: A) silica and/or alumina particles, and B) a compound of overall formula (I): Al(OH)a(SO4)b(SiOx)c(Y)d  (I)  with: a between 0.1 and 2, b between 0.3 and 1.5, c between 0 and 0.1, d greater than 0.05, Y chosen from alkali metals and alkaline earth metals, x between 2 and 4, and its derivatives, the said compound (B) being present in the suspension at a concentration of at least 1.65 mol/l, expressed as moles of aluminium issued from the said compound. Another subject-matter of the invention is a process useful for the preparation of the said suspension and its use in the field of cement pastes, mortars and concretes and in particular as setting and hardening accelerating agent for cements.

Abstract: A structured boehmite pigment which comprises a plurality of alumina monohydrate particles. The pigment is particularly useful as a flatting pigment in paint and as an anti-block agent in plastic film. The boehmite pigment has an aggregate median particle size of about 8 to about 30 microns; a total pore volume of at least about 0.8 ml/g; a differential pore volume of less than about 0.3 ml/g; an oil absorption of about 70 to about 135 m/g; a BET surface area of about 3 to about 20 m2/g, and a TAPPI brightness of at least about 90.

Abstract: Method for manufacturing a plate boehmite and a plate alumina having high catalytic activity. The plate boehmite is prepared by subjecting at least one kind of an alkaline earth metal compound, which is selected from calcium, strontium and barium, and aluminum hydroxide to pressurization and heating at 150 to 300° C. in the presence of water. The resulting reaction product is treated with an acid to remove the residual alkaline earth metal compound contained in the product, followed by rinsing with water. The resulting plate boehmite is subjected to calcination at 450 to 1500° C. Thus, a plate alumina comprising a mixture of &thgr;-alumina and &dgr;-alumina as a major component is prepared.

Abstract: An improvement in the Bayer process for producing alumina trihydrate in which bauxite ore is digested in a mixture with a digestion sodium aluminate liquor to produce a slurry, the slurry is settled to remove undigested residues therefrom and produce a pregnant liquor of sodium aluminate and alumina trihydrate is precipitated from the pregnant liquor in the presence of alumina trihydrate recycled as seed. When beginning the precipitation, an aliquot of the pregnant liquor with recycled alumina trihydrate is removed, subjected to mechanical action of an intensity and for a time sufficient to cause formation of seeds, and returned with the formed seeds to the beginning of the precipitation.

Abstract: A modified alumina is useful as metals passivator in fluidizable catalytic cracking catalysts. The modified alumina is prepared from a hydrated alumina, e.g., gibbsite, which is reacted with a low-molecular weight organic acid, e.g., acetic acid, forming aluminum salts. Calcination of the modified alumina results in decomposition of the aluminum salt.

Abstract: A process for the manufacture of coarse aluminum hydroxide via the Bayer Process. The process involves the decomposition of a supersaturated alkaline aluminate liquor in a two stage precipitation process having an agglomeration stage and a growth stage. The agglomeration stage takes place in agglomeration tanks, where the liquor is seeded with fine aluminum hydroxide to induce precipitation and formation of a suspension, followed by a growth stage, where the suspension is seeded with a coarse aluminium hydroxide. Typically, the feed of the supersaturated alkaline aluminate liquor is split over a first agglomeration tank at a higher liquor temperature of 70° to 100° C. and a second agglomeration tank or one or more of a series of second agglomeration tanks at a lower liquor temperature of 50° to 80° C.

Abstract: A process which allows the conversion of clay minerals of the kalonite group, to a relatively pure form of alumina and silica respectively comprising the steps of (a) heating the kaolinite group minerals to greater than 500.degree. C., which causes dehydroxylation of the crystallographic lattice and formation of an intermediate meta-kaolin; (b) reacting the intermediate with only one of a selection of reagents including acids, alkalines or metalliferous compounds followed by heating of the mixture to form an aluminium salt in solution and residue of silica; (c) separation of the aluminium salt solution from the residue of silica by filtration and further treatment of the silica residue to produce a relatively pure form of fine particled silica; (d) formation of an alum by addition of ammonium sulphate in solution to the aluminium salt solution and further treatment of the alum to produce a relatively pure form of aluminium hydroxide.

Abstract: Aluminum hydroxide is disclosed, wherein a mean particle size of a secondary particle is from 0.1 to 8 .mu.m, a BET specific surface area is not less than about 30 m.sup.2 /g and a pore size distribution has a maximum value within the range from 5 to 100 nm, a method for producing the same, and a method of using the same, comprising containing the same in a rubber, a method for using the same as a filler of a rubber composition for tire tread, and a rubber composition for tire tread using the same.

Abstract: Pelletized adsorbent compositions and methods of adsorbing toxic target compounds are provided for the destructive adsorption or chemisorption of toxic or undesired compounds. The pelletized adsorbents are formed by pressing together powder nanocrystalline particles comprising a metal hydroxide or a metal oxide at pressures of from about 50 psi to about 6000 psi to form discrete self-sustaining bodies. The pelletized bodies should retain at least about 25% of the surface area/unit mass and total pore volume of the starting metal particles.

Abstract: A process for producing alumina hydrates having a boehmite structure is provided. These alumina hydrates are dispersible in water. The boehmite or pseudoboehmite in colloids having a pH value of between 3 and 7 is present in a nanocrystalline form (<4 nm) whereby an exceptionally high translucence is imparted to the colloid.

Abstract: The present invention allows the reproduction of a crystalline aluminum hydroxide having a high particle strength and a high purity which can find wide application such as abrasive from a supersaturated sodium aluminate solution which is being recycled in the production of aluminum hydroxide or lithographic printing plate. In a process for the purification of aluminum hydroxide which comprises the hydrolysis reaction of a supersaturated solution of sodium aluminate to crystallize aluminum hydroxide, the improvement which comprises the steps of keeping the temperature of a suspension formed by mixing a mother liquor having a total caustic soda concentration of from 50 to 700 g/l and an aluminum concentration or from 0 to 300 g/l with crystalline aluminum hydroxide at a range of from 10.degree. C. to 200.degree. C. for at least 1 to 48 hours, mixing the suspension with the supersaturated solution of sodium aluminate, and then causing the crystallization reaction at the crystallization reaction temperature.

Abstract: Process for the production of aluminium hydroxide by digesting bauxite with alkali solution and precipitating aluminium hydroxide from the digestion solution, comprising:a combining bauxite and alkali solution having a caustic concentration of at least 180 grams per liter expressed as sodium carbonate and digesting partly the bauxite in the combined product in a first digestion step at relatively low temperature,b separating reaction product obtained in step a into a liquid phase and a solids/liquid slurry,c combining liquid phase and solids/liquid slurry obtained in step b and digesting the combined product in a second digestion step at relatively high temperature,d releasing heat from the reaction product obtained in step c to preheat liquid phase obtained in step b,e separating the reaction product obtained in step d into a supersaturated sodium aluminate solution and undissolved material,f precipitating aluminium hydroxide from the supersaturated sodium aluminate solution obtained in step e and separating

Abstract: Disclosed are a powder of indium-tin oxide aciculae suitable as an electroconductive filler for an electroconductive ink to be used for forming a transparent electroconductive film, a method for producing a raw material to be used for producing the powder of indium-tin oxide aciculae, which has a major diameter of 5 .mu.m or more and a ratio of the major diameter to the minor diameter of 5 or more, an electroconductive paste capable of forming a light-transmitting electroconductive film having sufficient electroconductivity and light transmittance by printing, such as screen-printing, followed by high-temperature baking, and a light-transmitting electroconductive film to be formed from the paste. The raw material is produced by heating and concentrating an aqueous solution containing indium ions and nitrato ions to form a high-viscosity slurry followed by separating a powder of aciculae from the slurry. By calcining the raw material, a powder of indium-tin oxide aciculae is produced.

Abstract: A process for the precipitation of aluminum trihydroxide from a supersaturated sodium aluminate solution, comprising the steps of(a) supplying a stream of supersaturated sodium aluminate solution and a first stream of aluminum trihydroxide particles as seed particles to a first reaction circuit,(b) maintaining the sodium aluminate stream containing the stream of seed particles in the first reaction circuit under conditions mainly resulting in precipitation and agglomeration of aluminum trihydroxide,(c) passing the stream thus obtained to a second reaction circuit in which the stream is maintained under conditions mainly resulting in precipitation and growth of aluminum trihydroxide particles,(d) passing the stream obtained in the second reaction circuit to a separation/classification unit to separate the stream into a first aluminum trihydroxide product stream comprising the coarser particle size portion, a second aluminum trihydroxide product stream comprising the finer particle size portion and a spent liqu

Abstract: By mixing an alumina gel suspension prepared by dispersing alumina gel in pure water in an alumina concentration of 0.1 to 12% by weight, with an aqueous metal salt solution wherein a compound of a Group VIA metal and a compound of a Group VIII metal are dissolved, and then evaporating water to dry while stirring the mixture, the metal component can be loaded effectively on the alumina gel to a sufficiently high loading quantity, and active catalyst compositions useful as catalysts being superior in functions, such as activities, to the conventional hydrogenation catalysts are easily obtainable. Sufficiently desulfurized hydrocarbons are obtainable by allowing the catalyst compositions to contact sulfur-containing hydrocarbons in the presence of hydrogen.

Abstract: A process for producing strong, essentially dust-free agglomerates from dust created by an industrial operation carried out, for example, on an ore or mineral, e.g. during the thermal conversion of a material containing predominantly gibbsite to sub-alpha alumina by a multistage thermal process having at least one intermediate stage. The process comprises grinding particles of binder material containing undercalcined alumina to a median particle size of less than 30 microns and to a specific surface area in the range of 90-300 m.sup.2 /g; combining about 1-4 parts by weight of the dust with one part by weight of the ground binder material to form combined solids; mixing the combined solids with water to produce agglomerates, the total amount of added water being about 0.8-1.2 parts by weight for every part by weight of the ground binder material, plus about 0.08 to 0.

Abstract: A process for the production of aluminum hydroxide from an alumina-containing ore comprising, in a process for the production of aluminum hydroxide involving extraction of alumina from an alumina-containing ore by an aqueous alkaline solution, supplying a slurry containing the alumina-containing ore at a high solid content which is prepared from a small amount of an alkaline solution together with an aqueous alkaline solution which is so preheated to a temperature that a preheated temperature is enough high to have a temperature after the mixing with the slurry which is higher than an extraction temperature of alumina, simultaneously or after the mixing them, to an extraction apparatus comprising of a tube reactor, extracting alumina from the alumina-containing ore under extraction conditions of a temperature of 120.degree.-160.degree. C.

Abstract: A process is disclosed for the production of alumina by the Bayer process, including a precipitation process having an agglomeration stage and a growth stage in which the precipitation slurry is passed through a multiplicity of growth tanks. In the agglomeration stage, the precipitation slurry is maintained at a temperature of about 75.degree. C. to 85.degree. C. In the growth stage, the agglomeration slurry is cooled by about 1.degree. C. to 3.degree. C. in each growth tank of the multiplicity of growth tanks as compared to an adjacent previous growth tank. The temperature of the precipitation slurry leaving the final precipitator is preferably about 55.degree. C.

Abstract: A process for the production of an aluminum hydroxide with rounded grain surfaces. An alkaline solution of a specific composition derived from the Bayer process is inoculated and adsorptively precipitated with an aluminum hydroxide with a specific grain distribution. The aluminum hydroxide obtained according to the new process is especially suitable for the flameproof finishing of polyesters.

Abstract: A process for the production of an aluminum hydroxide with rounded grain surfaces. An alkaline solution of a specific composition derived from the Bayer process is inoculated and adsorptively precipitated with an aluminum hydroxide with a specific grain distribution. The aluminum hydroxide obtained according to the new process is especially suitable for the flameproof finishing of polyesters.

Abstract: New crystalline phases of the fluoroaluminum compound AlF.sub.k (OH).sub.3-k and processes for their preparation and conversion to conventional phases, as well as isolation of solid HAlF.sub.4 are disclosed.

Abstract: Aluminum hydroxide containing no coarse particle is prepared by continuously supplying at least one compound selected from the group consisting of aluminum alkoxides and aluminum alkoxide derivatives which are prepared by chemically modifying aluminum alkoxides, and water under high shear rate stirring.

Abstract: A process for preparing an ultra-white alumina trihydrate having a G.E. brightness of at least about 98%. The product is alumina trihydrate that has been rehydrated with coprecipitation, and the crystal phase of the product is primarily gibbsite in thin platelet form having a ratio of thickness to diameter of about 0.2 to about 0.3. The product is prepared by flash activation of a white initial alumina trihydrate, addition of the activated material to a purified sodium aluminate liquor having an alumina to caustic ratio of about 0.5, and rehydrating and precipitating the alumina at ambient temperature under agitation for about 48 hours, followed by washing and drying of the resulting precipitate. The material is especially useful as a filler or coating in papermaking, and it can be substituted for a portion of titanium dioxide pigment in the ratio of 1:1, and can be combined with titanium dioxide as a pigment mixture, either in slurry form or in dry form.

Abstract: The present invention relates to fluorinated surfaces which exhibit sufficient hydrophilicity and sufficient electropositivity to bind DNA from a suspension containing DNA and permit elution of the DNA from the surface. Generally, the hydrophilic and electropositive characteristics are expressed at the fluorinated surface. Preferred fluorinated surfaces of the present invention include fluorinated Al(OH).sub.3, fluorinated SiO.sub.2 and fluorinated Celite. The fluorinated surfaces of the present invention are particularly useful in processes for purification of DNA from other cellular components. In these processes, a suspension of cellular components is placed in contact with the fluorinated surface, the fluorinated surface is washed to remove all cellular components other than DNA which are bound to the surface, and the bound DNA is eluted from the surface. Lower concentrations of chaotrope in the binding buffer are needed to bind DNA to the fluorinated surfaces.

Abstract: A method of making water soluble pre-ceramic polymers includes heating hydrated metal salts above their melting points. A flow of air drives off water and most of the ligands. Polymerization occurs in the melt and the remaining side groups make the polymer soluble in water. Solubilization in water is accomplished by mixing the polymer with distilled water and heating the mixture at a temperature higher than about 60.degree. C. Thus prepared polymer solutions may be used to form fibers, films, and composite matrices.

Abstract: An improved process for making high purity aluminum hydroxide [Al(OH).sub.3.3H.sub.2 O] of the hydrargillite form containing the steps of: (a) adding a non-powdered aluminum solid, preferably aluminum ingots, into a hot water bath at about 70.degree. C. to form a reaction mixture; (b) stirring the reaction mixture for about 20 minutes: (c) adding an alkaline-generating solid, preferably sodium hydroxide solids, into the reaction mixture and heating the reaction mixture to reach boiling point temperature; (d) lowering the temperature of the reaction mixture to 75.degree..about.80.degree. C. and stirring the reaction mixture for about 60 minutes; (e) lowering the temperature of the reaction mixture to room temperature; and (f) filtering the reaction mixture to obtain the high purity aluminum hydroxide form. The high purity of the final product was confirmed by data from X-ray diffraction and thermogravimetric analysis.

Abstract: Fine flaky boehmite particles which have an orthorhombic crystal form and a specified crystal face grown in the form of a flat plate, and a process for the preparation of fine flaky boehmite particles which comprises subjecting aluminum hydroxide or hydrated alumina having a particle size adjusted to the order of submicrons to hydrothermal treatment in water or an aqueous alkali solution at a temperature of 150.degree. C. or above under a pressure of 100 atm or below. The fine flaky boehmite particles are useful as a starting material for the preparation of fine flaky alumina particles or as a filler suitable for a pigment for coating materials, a filler for rubbers and plastics and a coating material for paper making.

Abstract: New crystalline phases of the fluoroaluminum compound AlF.sub.k (OH).sub.3-k and processes for their preparation and conversion to conventional phases, as well as isolation of solid HAlF.sub.4 are disclosed.

Abstract: Alumina hydrate particles have a high surface area and low dispersity and may have a low soluble soda content. They may be made by milling a liquid suspension of alumina hydrate, subjecting the milled suspension to classification into coarse and fine fractions, recycling the coarse fraction to the mill and recycling the fine fraction to the classification stage. A narrow particle size distribution is obtained.

Abstract: Alumina powder having a .theta.-alumina content of at least 70% by weight and an average primary particle size at least 0.1 .mu.m and containing a tungsten compound in an amount of 0.1 to 5% by weight in terms of tungsten oxide based on alumina can be used as an abrasive for a magnetic recording medium having good properties.

Abstract: The invention concerns the production of aluminum trihydrate crystal by the Bayer process, by digesting ground bauxite, filtering off the red mud, cooling the filtrate, and crystallizing out the dissolved aluminum hydroxide as gibbsite. Before and/or during the crystallization, polyglycerines of the general formula H--(OCH.sub.2 CHOH--CH.sub.2).sub.n --OH, where n is an integer equal to or greater than 3, are added.

Abstract: Alumina hydrate particles have a high surface area and low dispersity and may have a low soluble soda content. They may be made by milling a liquid suspension of alumina hydrate, subjecting the milled suspension to classification into coarse and fine fractions, recycling the coarse fraction to the mill and recycling the fine fraction to the classification stage. A narrow particle size distribution is obtained.

Abstract: Fine flaky boehmite particles which have an orthorhombic crystal form and a specified crystal face grown in the form of a flat plate, and a process for the preparation of fine flaky boehmite particles which comprises subjecting aluminum hydroxide or hydrated alumina having a particle size adjusted to the order of submicron to hydrothermal treatment in water or an aqueous alkali solution at a temperature of 150.degree. C. or above and under a pressure of 100 atm or below. The fine flaky boehmite particles are useful as a starting material for the preparation of fine flaky alumina particles or as a filler suitable for a pigment for coating materials, a filler for rubbers and plastics and a coating material for paper making.

Abstract: An aqueous slurry of about 100-1000 centipoises viscosity suspending about 200-2000 g/l of aluminum hydroxide particles smaller than 5 .mu.m is spray-dried, and the dried powders are calcined to obtain alumina powders. The alumina powders have a sharp particle size distribution, being suitable for electronic, abrasive and refractory applications.

Abstract: A process for producing agglomerates from dust (especially electrostatic precipitator dust) collected from a process involving the thermal conversion of a material containing gibbsite to sub-alpha alumina and alpha alumina, and the agglomerates so formed. The process involves binding the dust particles together using water and undercalcined alumina taken from an intermediate stage of the same thermal conversion that originally produces the dust. The added undercalcined alumina is ground, in order to create fresh surfaces, to a median particle size of less than 30 microns and a specific surface area of about 130 to 300 m.sup.2 /g. About 1-4 parts by weight of the dust are mixed with every part by weight of the ground undercalcined alumina. A special procedure is employed for mixing the solids and water which makes use of intensive mixing.

Abstract: Macrocrystalline .alpha.-alumina hexagonal platelets, well adapted as reinforcing materials and polishing agents, are prepared by calcining admixture of transition or hydrated alumina and a fluorocompound flux, such fluorocompound flux having a melting point of up to 800.degree. C. and, in the molten state, serving to dissolve the transition/hydrated alumina.

Abstract: Alumina trihydrate is dehydrated and rehydrated with a solution of dye, then dried to make colored alumina trihydrate which is distributed in a resin matrix to make solid decorative materials, such as artificial granite having excellent fire retardance.

Abstract: A method for the production of aluminum hydroxide, including reacting water in the liquid phase and aluminum at a pH above about 12.4. In this pH range, aluminum hydroxide is produced at acceptable rates both for aluminum surface areas above 75,000 mm.sup.2 /g and for aluminum surface area of less than about 50,000 mm.sup.2 per gram, and even down to 20 mm.sup.2 per gram. According to an alternative view of the invention, it is characterized by the production of aluminum hydroxide by reacting aluminum with liquid water containing choline. Aluminum hydroxide particles having unique morphologies are obtained.

Abstract: The invention includes novel separations material of stable polybutadiene coated and crosslinked on a surface of generally spherical metal oxide/hydroxide support particles comprising crystals of metal oxide/hydroxide with the crystals extending radially outward from a central core region and having a shape selected from principally acicular to principally lamellar. A chromatographic packing material for performing high performance liquid chromatography in the reverse phase of polybutadiene coated on alumina in accordance with the present invention provides highly symmetrical chromatogaphic peaks.

Abstract: A boehmite or boehmite precursor can be improved in its dispersibility by subjecting it to a hydrothermal treatment at a pH of less than 3.5 and at elevated temperature and pressure.

Abstract: In a process for precipitating alumina hydrate from a stream of Bayer process liquor, wherein the stream is first divided into a major portion and a minor portion, the minor portion fed to an agglomeration stage and seeded with fine seed to induce precipitation and formation of a slurry, and the major portion cooled and charged with coarse seed and directed to a growth stage to induce formation of alumina hydrate product, the steps of: separating solids from the minor portion after formation of the slurry; cooling, to a temperature of between about 45.degree. C. and about 60.degree. C., the liquid remaining after separating solids from the slurry formed in the agglomeration stage; adding an amount of coarse seed to the remaining liquid to generate a slurry of fresh hydrate nuclei; and recombining the slurry of fresh hydrate nuclei with the major portion of the stream.

Abstract: The present invention provides anticorrosive pigments on the basis of tertiary alkaline-earth aluminum phosphates, particularly those where the numerical atomic ratio x:y:z of formula AE.sub.x Al.sub.y (PO.sub.4).sub.z of alkaline earth to aluminum to phosphorus or phosphate is 50-70% to 5-30% to 20-50%. It also provides a process for their production in which an alkaline-earth compound and aluminum compound sufficiently soluble with phosphoric acid are reacted with phosphoric acid, the precipitated pigment is filtered off as usual and dried, optionally calcined and optionally ground.

Abstract: An improved process for precipitating alumina from Bayer process liquors is disclosed. The process involves dividing an incoming pregnant liquor stream into a minor portion of about 10 to about 25% by volume of the total incoming pregnant liquor stream, and directing that stream into a series of small tanks where the minor stream is permitted to agglomerate. Fine aluminum hydroxide seed having a median particle size of between about 30 and about 60 microns is added to this stream. The slurry resulting from the agglomeration stage is then directed to a set of larger vessels in which the growth stage will take place. At this point, the remaining portion of the pregnant liquor is combined with the slurry resulting from the agglomeration stage. A coarse seed charge of about 150 to about 600 grams/liter of seed having a median particle size of between about 80 and about 100 microns is charged into the second set of vessels.

Abstract: Aluminum hydroxide having a particle size of 2 to 30 .mu.m and having small specific surface area and low resin filling viscosity can be prepared by using precipitated aluminum hydroxide composed of secondary agglomerated particles having a primary particle size almost equal to the desired average particle size of intended pulverized aluminum hydroxide as the starting material to be pulverized and pulverizing this starting aluminum hydroxide. This aluminum hydroxide has an average particle size of 2 to 30 .mu.m, a surface roughness coefficient Sr/Sc (in which Sr represents the specific surface area of particles measured by the nitrogen adsorption method and Sc represents the specific surface area calculated from the size of particles approximated to spheres while taking the particle size distribution of particles into consideration) smaller than 2.5 and a linseed oil absorption smaller than 30 cc/100 g as determined according to JIS K-5101.

Abstract: Process for the production of a short-prismatic aluminum hydroxide by decomposing a supersaturated sodium aluminate liquor. The product can be used as a pigment and filler in the paper industry, as a flame-retardant filler in plastics and as a white pigment in paints and enamels.

Abstract: A method is described for mixing a difficult to wet, finely divided powder, e.g. alumina dust, with an aqueous liquid, e.g. Bayer process spent liquor. In the method, the liquor is introduced into a cylindrical mixing zone having a conical bottom zone, the liquor being continuously introduced into the mixing zone as a high velocity stream tangentially immediately above the conical zone to thereby form a rapidly moving vortex within the mixing zone. The dust is caused to fall into the center of the vortex whereby the dust is rapidly engulfed by the liquor with little or no dusting. The thus formed slurry is continuously removed from the bottom of the conical zone and may be processed through a classification circuit, to be separated as fine seed and returned to the precipitation circuit where the fine particles are agglomerated and grown to larger particles of alumina by contact with Bayer process pregnant liquor.

Abstract: A method of modifying crystal structure of alumina trihydrate crystallizing from saturated Bayer liquors, which method includes the treatment of the saturated Bayer liquors with a crystal modifying amount of a polysaccharide, preferably a dextran.

Abstract: Aluminum oxide ceramic composite articles having high flexural and tensile strength are produced by introducing a liquid aluminum oxide precursor material into a ceramic reinforcement fabric, curing the precursor material at an elevated temperature, and converting the cured precursor material to an aluminum oxide ceramic by pyrolysis at temperatures which do not result in the degradation of the reinforcement material. Such ceramic composite articles are particularly useful for applications requiring a low dielectric constant and a high mechanical strength.

Abstract: An improved process for precipitating alumina from Bayer process liquors is disclosed. The process involves dividing an incoming pregnant liquor stream into a minor portion of about 10 to about 25% of the total incoming pregnant liquor stream, and directing that stream into a series of small tanks where the minor stream is permitted to agglomerate. Fine aluminum hydroxide seed having a median particle size of between about 30 and about 60 microns is added to this stream. The slurry resulting from the agglomeration stage is then directed to a set of larger vessels in which the growth stage will take place. At this point, the remaining portion of the pregnant liquor is combined with the slurry resulting from the agglomeration stage. A coarse seed charge of about 150 to about 600 grams/liter of seed having a median particle size of between about 80 and about 100 microns is charged into the second set of vessels. This improved process helps to increase the yield of a strong coarse aluminum trihydroxide product.