Abstract: The invention relates to preparations of monodisperse spherical oxide particles in the form of free-flowing powders of agglomerates in which the particles are bonded to one another by a binder. With these preparations, the oxide particles can be homogeneously dispersed in polymer systems with particular ease.

Abstract: The present invention concerns a moulded microcrystalline spherical Al2O3- sintered body, process for its production as well as its use.

Abstract: Aluminum hydroxide having specific characteristics, and a tire tread rubber composition and a pneumatic tire employing the aluminum hydroxide, which allow grip performance and abrasion resistance to increase and rolling resistance to decrease and are superior in processibility, are provided.

Abstract: The present invention concerns a moulded microcrystalline spherical Al2O3- sintered body, process for its production as well as use.

Abstract: The present invention provides homogeneously surface-fluorinated metal oxide particulates, characterized in that a metal oxide particulate such as Ti, Al, Si, Ag, Cu, Fe, Zr, Ce, Mn, Sn, Ge and Ta is surface reacted with fluorine gas while allowing the metal oxide particulate to flow, and also provides a process for manufacturing the metal oxide particulates. The homogeneously surface-fluorinated metal oxide particulates according to the present invention are useful as an additive for a weatherproof coating material, a weatherproof resin or a cosmetic material. Furthermore, according to the process of the present invention, the surface of a metal oxide particulate can be homogeneously fluorinated at any ratio in a very simple and efficient manner.

Abstract: The present invention relates to complex oxides used as raw materials for fine ceramic materials, and more particularly to complex oxide precursors in the form of a fine powder which are readily converted to complex oxides with low energy and also a process for preparing the same.

Abstract: The present invention related to methods of manufacturing oxide, nitride, carbide, and boride powders and other ceramic, organic, metallic, carbon and alloy powders and films and their mixtures having well-controlled size and crystallinity characteristics. This invention relates, more particularly, to a development in the synthesis of the ceramic, metallic, composite, carbon and alloy nanometer-sized particles with precisely controlled specific surface area, or primary particle size, crystallinity and composition. The product made using the process of the present invention and the use of that product are also claimed herein.

Abstract: An alumina solid, obtainable by a process comprising the step of contacting in a liquid medium at least one alumina precursor with at least one template comprising a dendrimeric molecular nanosystem a mixture of two or more thereof.

Abstract: A process for making a modified boehmite alumina comprising reacting at elevated temperatures a boehmite alumina with a compound having the formula: X(SO3M)n wherein X is an organic moiety, M in a monovalent cation, and n is an integer reflecting the number of SO3M groups bonded to said organic moiety to produce a reaction mixture containing modified boehmite alumina and recovering solid, modified boehmite alumina from the reaction mixture.

Abstract: A porous spinel type oxide shows a large surface area and a uniform micro-porous structure. The oxide is expressed by general formula MO—Al2O3 and shows a surface area per unit weight of not less than 80 m2/g. Such a porous spinel type compound oxide is obtained by impregnating a specific &ggr;-alumina carrier with a solution of a compound of metal element M capable of taking a valence of 2, drying the impregnated carrier and calcining it at a temperature of 600° C. or higher. The specific &ggr;-alumina carrier shows a surface area per unit weight of not less than 150 m2/g, a micro-pore volume per unit weight of not less than 0.55 cm3/g and an average micro-pore diameter between 90 and 200 angstroms. The micro-pores with a diameter between 90 and 200 angstroms occupy not less than 60% of the total micro-pore volume of the carrier.

Abstract: A catalyst for hydrodemetalization of heavy oil, especially residuum oil, and a process for preparing the same, wherein said catalyst comprises the metal elements of Groups VIII and/or VIB as active components supported on an alumina carrier having large pores. The total pore volume of said carrier is in the range of 0.80˜1.20 ml/g (by mercury porosimetry method), the specific surface area in the range of 110˜200 m2/g, the peak pore diameter in the range of 15˜20 nm, and the bulk density in the range of 0.50˜0.60 g/ml. In the process of the invention, a physical pore-enlarging agent and a chemical pore-enlarging agent are added simultaneously during the mixing of the pseudoboehmite to a plastic mass, then extruding, drying, calcining, the carrier is obtained, then impregnating with active components by spraying onto the carrier, after drying and calcining, the catalyst is obtained.

Abstract: A new, cost effective process for the production of ultrafine particles which is based on mechanically activated chemical reaction of a metal compound with a suitable reagent. The process involves subjecting a mixture of a metal compound and a suitable reagent to mechanical activation to increase the chemical reactivity of the reactants and/or reaction kinetics such that a chemical reaction can occur which produces a solid nano-phase substance. Concomitantly, a by-product phase is also formed. This by-product phase is removed so that the solid nano-phase substance is left behind in the form of ultrafine particles. During mechanical activation a composite structure is formed which consists of an intimate mixture of nano-sized grains of the nano-phase substance and the reaction by-product phase.

Abstract: A process for producing zinc oxide fine particles comprising heating a mixture comprising a zinc source, a carboxyl-containing compound, and an alcohol; a process for producing zinc oxide-polymer composite particles, which comprises heating a mixture comprising a zinc source, a carboxyl-containing compound, a polymer, and an alcohol at a temperature of 100° C. or higher; a process for producing inorganic compound particles having on their surface a cluster of thin plate like zinc oxide crystals with their tip projecting outward, which comprises heating a mixture comprising a zinc source, a carboxyl-containing compound, lactic acid or a compound thereof, and an alcohol at a temperature of 100° C.

Abstract: Hydrated aluminium compounds of the present invention are represented by the general formula nS, mM, Al2O3, xH2O where S is a surfactant or a group of surfactants, n is the number of moles of S, M is an alkaline cation, preferably selected from the group formed by Na+, K+, NH4+, m is the number of moles of M and x is the number of moles of water. The hydrated compounds are obtained from inorganic aluminium sources which are in the form of cation-monomers and/or cation-oligomers. The surfactants are anionic and/or non-ionic surfactants. When the group of surfactants comprises at least one anionic surfactant, at least one cationic surfactant can optionally be added.

Abstract: Alumina particles having high dispersibility and plasticity, at least on the surface of which a phosphoric acid or phosphate is present and suitable for use as a material for pigments for paints, precision abrasives or ceramics. The alumina particles are produced by adding a crystallization inhibitor containing at least phosphate ion to aluminum hydroxide or alumina hydrate and then conducting a hydrothermal synthesis treatment. The amount of the phosphate ion to be added is in the range of 3.0×10−3 to 2.5×10−2 mol per mol of aluminum hydroxide or alumina hydrate. The particle size of aluminum hydroxide or alumina hydrate is 0.1 to 5.0 &mgr;m. The hydrothermal synthesis is preferably conducted at 350° C. or above under a pressure of 50 to 200 atm and at a temperature elevation rate of 5° C./min to 0.3° C./min. The thus obtained alumina is &agr;-alumina in the form of hexagonal plate single crystal having a particle size of 0.

Abstract: The present invention provides a resin additive obtained by subjecting inorganic particles of silica or alumina to surface treatment with tannic acid and further subjecting them to surface treatment with a coupling agent, or subjecting inorganic particles to surface treatment with tannic acid and then subjecting them to surface treatment with a phenone compound or saccharides, followed by further subjecting them to surface treatment with a coupling agent. The above resin additive has an effect to provide a thermoplastic resin with heat stability in heating and melting the resin and prevent a reduction in the IZOT impact strength.

Abstract: An alumina solid is obtainable by a process comprising the step of contacting in a liquid medium at least one alumina precursor with at least one template comprising a membrane lipid or a mixture of two or more thereof.

Abstract: An alumina sol, containing a small amount of water of crystallization inside the crystal lattice of boehmite, having high mechanical strength, properties suitable for use as an alumina adsorbent or carrier, and the ability to be formed without additional concentration. The alumina sol comprises a fibrous boehmite having the molecular formula Al2O3.1.05-1.30 H2O with the weight average diameter and the weight average length being respectively in the range of 3 to 50 nm and in the range of 30 to 3000 nm, and has an alumina concentration of 15 to 60% by weight.

Abstract: .alpha.-Alumina comprising .alpha.-alumina single crystal particles which are homogeneous containing no crystal seed inside the particles; have an octa- or higher polyhedral shape; have a D/H ratio of from 0.5 to 3.0, wherein D represents a maximum particle diameter parallel to a hexagonal lattice plane of a hexagonal close-packed lattice of the particles, and H represents a diameter perpendicular to the hexagonal lattice plane; have a number average particle diameter of more than 5 .mu.m and not more than 30 .mu.m; have a sodium content of less than 5 ppm in terms of Na.sub.2 O; and have an alumina purity of not less than 99.90% by weight. .alpha.-Alumina in a powder form composed of .alpha.-alumina single crystal particles having a high punity, a fine and uniform composition, a narrow particle size distribution, and an octa- or higher polyhedral shape which are not aggromerates. The .alpha.

Abstract: A powdery .alpha.-alumina having an alumina purity of at least 99.8 wt. %, a sodium content of 40 ppm or less and an iron content of 20 ppm or less, which is obtained by grinding aluminum hydroxide which is produced by the Bayer process or a transition alumina which is obtained by precalcining aluminum hydroxide produced by the Bayer process, and calcining the aluminum hydroxide or transition alumina in an atmosphere containing 1 vol. % or more of a hydrogen chloride gas, or an atmosphere containing 1 vol. % or more of a chlorine gas and 0.1 vol. % or more of steam, at a temperature of 600 to 1400.degree. C.

Abstract: A process for producing .alpha.-alumina powder comprising the step of calcining at least one of transition alumina and a transition alumina precursor capable of becoming transition alumina on heating, in a gas atmosphere containing (1) a hydrogen halide, (2) a component prepared from a halogen and steam or (3) a halogen, in the presence of at least one of a seed crystal and a shape-controlling agent. The .alpha.-alumina powder is particularly useful as a raw material for abrasives, fillers, sinters or spacers which comprises .alpha.-alumina particles having a substantially octahedral or eicosahedral shape, a specific structure, and a narrow primary particle size distribution.

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: A fire-retardant plastic mixture contains 55%-75% by weight of boehmite which has an orthorhombic crystal structure and has the general formula AlO.sub.x (OH).sub.3-2x with x-values ranging between 0.8 and 0.99, and has a mean grain diameter d.sub.50 ranging between 0.4 and 0.7 .mu.m, a d.sub.10 value ranging between 0.7 and 1.2 .mu.m and a d.sub.90 value ranging between 0.2 and 0.4 .mu.m. The filler material is used in the form of a finely-crystallized hydrargillite which is obtained during a precipitation process according to Bayer with a grain diameter of 0.5 to 3 .mu.m, which is suspended and which, without any mechanical working, is transformed directly in a hydro-thermal process at temperatures ranging between 220.degree. C. and 240.degree. C. under turbulent conditions into a boehmite of the general formula AlO.sub.x (OH).sub.3-2x with x-values ranging between 0.8 and 0.99.

Abstract: Fine powders of ceramic materials can be obtained by firing a precursor powder in a rotary kiln while carried on coarse carrier particles.

Abstract: An aluminum oxide mass characterized by a specific surface area greater than or equal to 70 m.sup.2 /g and a narrow pore radius distribution, with at least 90% of the pore radii being approximately 0.5 to 2.5 nm, preferably approximately 1.7 to 2.2 nm.

Abstract: A process for producing an alumina material with high strength is disclosed. The process for producing an alumina material includes the steps of (a) providing a solution containing a dispersing agent, (b) mixing a .theta.-alumina powder and an .alpha.-alumina powder with the solution to form a slurry, (c) filtering the slurry to form a green part, (d) drying the green part, and (e) densifying the dried green part to form the alumina material.

Abstract: Compounds of the general formula Ca.sub.2 MeSbO.sub.6 where Me is a 3+ ion selected from the group consisting of aluminum (Al), scandium (Sc), indium (In), gallium (Ga), or a rare earth metal have been prepared and included as the substrate or barrier dielectric in high critical temperature thin film superconductors, ferroelectrics, pyroelectrics, piezoelectrics, and hybrid device structures.

Abstract: To hydrous titanium dioxide obtained by hydrolysis of titanium sulfate was added a predetermined amount of a water-soluble aluminum compound and/or a water-soluble zinc compound, the mixture is calcined, and a suitable amount of aluminum and/or zinc is introduced into the crystals to make up the crystal defects of anatase-type titanium dioxide, so that it has increased stability and excellent color stability.

Abstract: Alpha alumina powder is produced by granulating at least one alumina starting material selected from group consisting of transition alumina and alumina compound to obtain particles and calcining the particles in a halogen-containing atmosphere which comprises a hydrogen halide gas, a halogen gas or a mixture of a halogen gas and steam and contains at least 0.1 % by volume of at least one halogen-containing gas selected from the group consisting of hydrogen halide gas and halogen gas.By granulating the alumina starting material powder in the form of particles to increase a bulk density and calcining them in the presence of halogen, .alpha.-alumina powder having a regulated particle size and shape and a narrow particle size distribution and containing fewer agglomerated particles is produced at a high calcining efficiency.

Abstract: A method of depositing catalytically active components on high-surface carrier materials is disclosed by dispersing the carrier materials in water and mixing this dispersion with an aqueous solution of soluble precursors of the catalytically active components. The pH of the dispersion is adjusted to a value between 6 and 8 before the aqueous solution of the precursors is supplied by capillary injection under constant agitation of the dispersion and thereafter, if necessary, the precursors of the catalytically active components are precipitated on the carrier material by capillary injection of a dilute base.

Abstract: Sol-gel alumina that is dried but unfired can be explosively comminuted by feeding the dried gel into a furnace held at temperatures above those at which vaporizable materials are eliminated from the particles of gel. At suitably elevated temperatures the firing is sufficient to form fully densified alpha alumina particles of a size suitable for direct use as abrasive grits.

Abstract: The present invention provides a process for producing fine flaky alumina particles which are suitable as a raw material for ceramics, a pigment for paint, etc., wherein aluminum hydroxide or alumina hydrate having a particle size regulated to the order of submicron is subjected to a hydrothermal treatment in water or an aqueous alkali solution at a temperature of 350.degree. C. or above and under a pressure of 200 kg/cm.sup.2 or below. The present invention further provides an alumina-based plastic material which is produced by kneading the aforesaid fine flaky particles with an organic water holding material and water. Methylcellulose, polyvinyl alcohol, carboxymethylcellulose, polyethylene glycol, etc. are preferably used as the organic water holding agent. The alumina-based plastic material has a high plasticity, so that there is no need of using a large amount of a binder. Thus a dense molded article having stable properties can be prepared.

Abstract: This invention relates to a generic process for producing a refractory oxide which comprises reacting liquid water with: at least one metal fluoride reactant; or at least one metal fluoride reactant and at least one metal oxide reactant; or at least one metal oxide reactant and an aqueous hydrogen fluoride solution, to produce either a colloidal mixture or a solution; drying either the colloidal mixture or solution; heating the dried product to produce a solid state metal hydroxyfluoride; heating the hydroxyfluoride to a temperature at which it chemically decomposes into a cationically-homogeneous and nanostructured solid state metal oxyfluoride; and performing one of the following heating steps: (i) to a solid state decomposition-temperature where the oxyfluoride chemically decomposes into a refractory oxide; or, (ii) to a molten state decomposition-temperature where the oxyfluoride chemically decomposes into a refractory oxide; or, (iii) to a vapor state decomposition-temperature where the oxyfluoride chemi

Abstract: A process for producing alumina and other aluminia products where the formation of a Schiff base imine by reaction of a orgaonaluminum amide or imide oligomer with a carbonyl compound is promoted by the Lewis acid character of the oligomer. The water byproduct of the Schiff base serves as an in situ reagent for subsequent hydrolysis and sol-gel condensation of the aluminum species with concomitant production of alkane. The imine then is washed from the alumina with a suitable solvent. Any of a number of primary amines and aldehydes or ketones may be reagents. Calcining of the sol-gels yields high surface area alumina as characterized by scanning electron microscopy, and gas physisorption measurements. Microporous and/or mesoporous alumina is obtained depending on synthesis conditions. Alumina microspheres are obtained under certain conditions.

Abstract: A process for preparing .gamma.,.delta.-unsaturated ketones of the general formula I ##STR1## by reacting an allyl alcohol of the general formula II ##STR2## in which R.sup.1 is H or a hydrocarbon radical having 1 to 20 carbon atoms, with diketene or an alkyl acetoacetate of the general formula III ##STR3## in which R.sup.2 is alkyl having 1 to 4 carbon atoms in an unmodified or modified Carroll reaction in the presence of an aluminum catalyst, wherein aluminum compounds which are stable liquids at room temperature, or a mixture of such aluminum compounds, which comprise at least one radical formed from an alkyl acetoacetate and 1 or 2 alkoxy radicals, or else comprise exclusively radicals formed from alkyl acetoacetates, which are esterified with sec-butanol or isobutanol, or else are esterified with at least two different alcohols, are used as aluminum catalyst.

Abstract: The present invention relates to a catalyst comprising an extruded essentially alumina-based support, constituted by a plurality of juxtaposed agglomerates and partially in the form of packs of flakes and partially in the form of needles, and optionally comprising at least one catalytic metal or a compound of a catalytic metal from group VIB, and/or optionally at least one catalytic metal or compound of a catalytic metal from group VIII. The invention also relates to its use in a fixed bed reactor, for hydrorefining and hydroconverting hydrocarbon feeds.

Abstract: The present invention provides a process for producing aluminum oxide fibers and, particularly, a process for producing aluminum fibers that have a high aspect ratio and can be accurately aligned, said process for producing aluminum oxide fibers comprising the steps of: uniformly mixing an aluminum or aluminum alloy powder with a boron oxide powder or a powder which, upon heating, can be converted to a boron oxide powder; and heating the mixed powder, or comprising the steps of: mixing not more than 50% by weight, in terms of titanium, of a titanium or titanium alloy powder to the starting mixture; and heating the mixed powder.

Abstract: Semi-crystalline alumina compositions with framework mesopores are disclosed. The compositions are assembled from inorganic aluminum precursors and nonionic polyethylene oxide surfactants. The new assembly pathway introduces several new concepts to alumina mesostructure synthesis. The application of low-cost, non-toxic and biodegradable surfactants and low cost aluminum reagents as alumina precursors which are inorganic and low solution reaction temperatures, introduces efficient and environmentally clean synthetic techniques to the formation of mesostructures. Recovery of the surfactant can be achieved through solvent extraction where the solvent may be water or ethanol or by calcination.

Abstract: A process is disclosed for preparing anhydrous alumina from aluminum hydroxide which comprises feeding aluminum hydroxide into a first suspension preheater and partially dehydrating the aluminum hydroxide with a hot exhaust gas, transporting the partially dehydrated aluminum hydroxide with said exhaust gas to a first separating means and separately withdrawing the exhaust gas and the partially dehydrated aluminum hydroxide, and dividing the partially dehydrated aluminum hydroxide into a first and second partial stream of solids. The process uses a circulating fluidized bed comprising a fluidized bed reactor, a recycle separator connected to the upper portion of said fluidized bed reactor, and a return line for leading solids from said recycle separator to the lower portion of said fluidized bed reactor. The second partial stream of solids is fed into a second suspension preheater and contacted with hot exhaust gas from the recycle separator.

Abstract: Alumina particles having high dispersibility and plasticity, at least on the surface of which a phosphoric acid or phosphate is present and suitable for use as a material for pigments for paints, precision abrasives or ceramics. The alumina particles are produced by adding a crystallization inhibitor containing at least phosphate ion to aluminum hydroxide or alumina hydrate and then conducting a hydrothermal synthesis treatment. The amount of the phosphate ion to be added is in the range of 3.0.times.10.sup.-3 to 2.5.times.10.sup.-2 mol per mol of aluminum hydroxide or alumina hydrate. The particle size of aluminum hydroxide or alumina hydrate is 0.1 to 5.0 .mu.m. The hydrothermal synthesis is preferably conducted at 350.degree. C. or above under a pressure of 50 to 200 atm and at a temperature elevation rate of 50.degree. C./min to 0.3.degree. C./min. The thus obtained alumina is .alpha.-alumina in the form of hexagonal plate single crystal having a particle size of 0.2 to 15 .mu.

Abstract: The present invention provides a hollow oxide particle including a shell wall constituting a hollow room, and the shell wall has a thickness of 20 nm or less. The shell wall may be mainly composed from at least one selected from the group consisting of alumina, spinel, iron oxides, yttrium oxides, and titanium oxides. A process for producing the hollow oxide particle comprises the steps of: forming a Water in Oil (W/O) type emulsion including aqueous microspheres having a each diameter of 100 nm or more, by adding an organic solvent to an aqueous solution dissolving and/or suspending at least one of metal salts and metal compounds; and forming the hollow oxide particle by atomizing the Water in Oil (W/O) type emulsion to burn. When the hollow oxide particle is brought into contact with a water-containing solution, a surface of the shell wall may have a minutely irregular surface.

Abstract: A process for producing a stable acidic aqueous alumina sol containing 50 to 300 nm of elongate secondary particles which are elongated in only one plane and formed by edge-to-edge coagulation of rectangular plate-like primary particles having a length of one side of 10 to 30 nm when observed through an electron microscope, the process comprises the steps of:(A) adding an alkali to an aqueous alumina sol containing fibrous colloidal particles of an amorphous alumina hydrate to produce a reaction mixture having a pH of 9 to 12,(B) subjecting the reaction mixture obtained in the step (A) to a hydrothermal treatment at a temperature of 110 to 250.degree. C. to produce an aqueous suspension containing an alumina hydrate having a boehmite structure, and(C) desalting the aqueous suspension obtained in the step (B) by adding water and an acid by ultrafiltration to form an acidic aqueous alumina sol having a pH of 3 to 6.

Abstract: Methods of making substantially phase-pure and thermally stable crystalline alumina compositions stabilized with an oxide of silicon, germanium, phosphorus, arsenic or a mixture thereof. Also provided are crystalline alumina compositions and catalyst supports made using these methods.

Abstract: The invention concerns oxidised aluminium or aluminium alloy pigments having a content of metallic aluminium of not more than 90% by weight with respect to the total weight, wherein the pigments are colored, flake-like, shiny and non-agglomerated, a process for the production thereof and use thereof as special-effect pigments and as base pigments for further colouring with organic or inorganic color pigments.

Abstract: Ultrafine metal oxide and mixed metal oxide ceramic particles are prepared by flame spray pyrolysis of a ceramic precursor solution containing one or more gycolato polymetallooxanes dissolved in a volatile organic solvent. Recycle of the nanosized particles disposed in additional ceramic precursor solution leads to larger particles. The metal oxide and mixed metal oxide particles may be converted to the respective nitrides by high temperature ammonolysis. The process produces high quality ceramic particles from inexpensive and relatively non-toxic reagents in high space-time yield.

Abstract: An apparatus for producing solid fine particulates has a substantially closed reaction vessel and a hollow gas input conduit inside the vessel formed with a multiplicity of similar outlet apertures each having a flow cross section of at most 2 mm.sup.2. The conduit has an overall cross-sectional area equal to at least 100 times the flow cross section of a one of the apertures. A foraminous structure in the vessel surrounds the conduit and an electrode is provided in the vessel outside the foraminous structure. A direct-current power supply has a negative side connected to the foraminous structure and a positive side connected to the electrode while the input conduit is at ground potential so that a glow discharge is created in the vessel between the foraminous structure and the electrode.

Abstract: A method and apparatus are disclosed for continuously drying, preferably with agglomeration and/or coating and sizing, and separating a solid product from a liquid feed material, especially bauxite slurry which passes through a very sticky phase during drying, without significant encrustation of the equipment used.

Abstract: A process for producing .alpha.-alumina powder comprising the step of calcining at least one of transition alumina and a transition alumina precursor capable of becoming transition alumina on heating, in a gas atmosphere containing (1) a hydrogen halide, (2) a component prepared from a halogen and steam or (3) a halogen, in the presence of at least one of a seed crystal and a shape-controlling agent. The .alpha.-alumina powder is particularly useful as a raw material for abrasives, fillers, sinters or spacers which comprises .alpha.-alumina particles having a substantially octahedral or eicosahedral shape, a specific structure, and a narrow primary particle size distribution.

Abstract: The invention concerns a process for the production of alumina for ceramics by calcining alumina trihydrate in the presence of a mineralizer such as a halogenated compound and/or a boron compound, the calcined alumina being constituted by friable agglomerates of elementary particles, or crystallites, of alpha alumina, the average size of which can be fixed as required, with a unimodal narrow distribution of crystallite sizes, characterized in that calcining of the alumina trihydrate is carried out in an industrial kiln in a renewed oxidising atmosphere at a temperature in the range 800.degree. C. to 1300.degree. C. for a period of 0.5 hour to 4 hours in the simultaneous presence of a halogenated compound acting as a mineralizer and a silica based alumina recrystallisation modifier which is uniformly and intimately distributed in the alumina trihydrate charge.

Abstract: An alumina solid is obtainable by a process comprising the step of contacting in a liquid medium at least one alumina precursor with at least one template comprising a membrane lipid or a mixture of two or more thereof.