Abstract: Plasma-sprayed layers of aluminium oxide on a substrate are produced by using a pyrogenically produced aluminium oxide, for example selected from the group consisting of borosilicate and steel, as starting powder.

Abstract: Plasma-sprayed layers of aluminium oxide on a substrate are produced by using a pyrogenically produced aluminium oxide, for example selected from the group consisting of borosilicate and steel, as starting powder.

Abstract: Granules based on silicon dioxide and having the properties: Average grain size: 10 to 120 ?m BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5% of the total pore volume exists of pores with a diameter < 5 nm, rest meso- and macropores pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/l They are prepared by dispersing silicon dioxide in water, spray drying, optionally heating and/or silanizing. Whereas a pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m2/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nm2 and a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm or a high-purity pyrogenically prepared silicon dioxide having metal contents of less than 0.

Abstract: Plasma-sprayed layers of aluminium oxide on a substrate are produced by using a pyrogenically produced aluminium oxide, for example selected from the group consisting of borosilicate and steel, as starting powder.

Abstract: Slip containing at least one aluminium oxide powder and at least one unstabilized zirconium dioxide powder, wherein a) the zirconium dioxide powder i) has a mean particle diameter of less than 300 nm, ii) shows only the monoclinic phase and the tetragonal phase in the X-ray diffraction pattern, with the proportion of tetragonal phase at room temperature being from 20 to 70%, and iii) is present in a proportion of from 2 to 20% by weight, based on the total amount of the slip, b) the aluminium oxide powder i) has a mean particle diameter of more than 300 nm and ii) is present in a proportion of from 80 to 98% by weight, based on the total amount of the slip, and c) the solids content, as the sum of aluminium oxide and zirconium dioxide, is from 50 to 85% by weight, based on the total amount of the slip.

Abstract: Process for preparing granules of oxidic or nonoxidic metal compounds, characterized in that a dispersion which comprises water, oxidic or nonoxidic metal compounds and at least one dispersant is spray-dried,—where the proportion of oxidic or nonoxidic metal compounds is 40 to 70% by weight and the sum of the proportions of water and the particles is at least 70% by weight and—the particles have a BET surface area of 20 to 150 m2/g and a median of the particle size of less than 100 nm,—where the dispersant is present in the dispersion with a proportion of 0.25 to 10% by weight based on the oxidic or nonoxidic metal compounds and—where the spray-drying is performed by atomization with air in the cocurrent principle or fountain principle, and an air inlet temperature of 170 to 300° C. and an air outlet temperature of 90 to 130° C. are selected.

Abstract: Glass is produced by depositing presintering composition on a preform set into move in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of the presintering composition while optionally a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas, whereby the presintering composition consists of granules of metal oxides or metalloid oxides of a pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m2/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nm2 and a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm or a high-purity pyrogenically prepared silicon dioxide having metal contents of less than 0.

Abstract: Nanoscalar, pyrogenically produced yttrium-zirconium mixed oxide which has a BET surface area of between 1 and 600 m2/g, a total chloride content of less than 0.05 wt. % and does not exhibit a conversion into the monoclinic phase during storage is produced by atomizing yttrium compounds and zirconium compounds and reacting them in a flame. The mixed oxide can be used as ceramic raw material.

Abstract: Method for fabricating a glass-monolith by the sol-gel process, in which a pyrogenically produced silica (fumed silica) is used in the form of a powder and/or a dispersion, characterized in that as pyrogenically produced silica (fumed silica) a silica (fumed silica) deriving from the group highly pure, pyrogenically produced silica (fumed silica) with a metal content of lower than 9 ppm and/or a pyrogenically prepared silicon dioxide powder having—a BET surface area of 30 to 90 m2/g, —a DBP number of 80 or less, an average aggregate area of less than 25,000 nm2, an average aggregate circumference of less than 1,000 nm, at least 70% of the aggregates having a circumference of less than 1,300 nm is used.

Abstract: Slip containing at least one aluminium oxide powder and at least one unstabilized zirconium dioxide powder, wherein a) the zirconium dioxide powder i) has a mean particle diameter of less than 300 nm, ii) shows only the monoclinic phase and the tetragonal phase in the X-ray diffraction pattern, with the proportion of tetragonal phase at room temperature being from 20 to 70%, and iii) is present in a proportion of from 2 to 20% by weight, based on the total amount of the slip, b) the aluminium oxide powder i) has a mean particle diameter of more than 300 nm and ii) is present in a proportion of from 80 to 98% by weight, based on the total amount of the slip, and c) the solids content, as the sum of aluminium oxide and zirconium dioxide, is from 50 to 85% by weight, based on the total amount of the slip.

Abstract: Granules based on pyrogenically prepared silicon dioxide, method for their preparation and use thereof Granules based on silicon dioxide and having the properties: Average grain size: 10 to 120 ?m BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5% of the total pore volume exists of pores with a diameter <5 nm, rest meso- and macropores pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/l They are prepared by dispersing silicon dioxide in water, spray drying, optionally heating and/or silanising. Whereas a pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m2/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nm2 and a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm or a high-purity pyrogenically prepared silicon dioxide having metal contents of less than 0.

Abstract: A method for producing ultra-high purity, optical quality, glass articles is disclosed which involves: 1. compacting metaloxide or metal loidoxide to granules having a mean particle size of less than about 1 millimeter; 2. optionally fully sintering the granules to produce high purity, artificial sand; 3. casting the granulesar artificial sand by conventional techniques, such as, slip casting, to form a high density, porous, green body; 4. optionally drying and partially sintering the green body; 5. optionally fully sintering the green body under vacuum, and 6.

Abstract: A binder-free metal oxide dispersion with a content of metal oxide of greater than 15 wt. %, wherein the metal oxide powder in the dispersion has a number-average aggregate diameter of less than 200 nm and the dispersion comprises as the liquid phase a mixture of water and a water-miscible, organic solvent. Coated substrates and mouldings produced with the metal oxide dispersion.

Abstract: Process for the preparation of a binder-free metal oxide sol, comprising the steps: a) initial introduction into a vessel of a metal oxide dispersion, wherein the metal oxide powder in the dispersion has an average, number-related aggregate diameter of less than 200 nm, and b1) addition of a metal alcoholate M(OR)x, and optionally of a hydrolysis catalyst, or b2) addition of a starting sol which is obtained by hydrolysis of a metal alcoholate M(OR)x with a hydrolysis catalyst, and the weight-related ratio of metal oxide from the hydrolysis to metal oxide in the dispersion is 0.01 to 1. Metal oxide sol obtainable by this process. Coated substrate which can be produced by means of the metal oxide sol, and shaped article.

Abstract: A multi-component glass which, in addition to the components TiO2 and SiO2, comprises a further component from the group consisting of glass-forming agents and/or intermediate oxides is prepared by preparing mixtures of the starting components and reacting these to give the desired compositions, or treating a green body with a suspension of the additional components and reacting it to give the desired composition. The multi-component glass can be used for the production of shaped bodies with dimensions close to the final dimensions.

Abstract: A layer which is obtained by thermal treatment from an aqueous dispersion applied to a substrate, the dispersion containing silicon/titanium mixed oxide powder prepared by flame hydrolysis. It is prepared by applying a dispersion which contains the silicon/titanium mixed oxide powder to a substrate and then sintering by using a thermal treatment. It can be used, for example, on materials with very low coefficients of expansion.

Abstract: Plasma-sprayed layers of aluminium oxide on a substrate are produced by using a pyrogenically produced aluminium oxide, for example selected from the group consisting of borosilicate and steel, as starting powder.

Abstract: The invention relates to a method for separating ashes from the exhaust gases of combustion installations by means of separating devices. According to the invention, a hydrophobic, pyrogenically produced silicic acid is introduced into the flow of exhaust gas.

Abstract: Pyrogenically prepared silicon dioxide with the following physicochemical properties: 1. Average particle size (D50 value) D50?150 nm (dynamic light scattering, 30 wt %) 2. Viscosity (5 rpm, 30 wt %) ??100 m·Pas 3. Thixotropy of Ti (?(5 rpm))/(?(50 rpm))?2 4. BET surface area 30-60 m2/g 5. Compacted bulk=100-160 g/L 6. Original pH?4.5 that can be used for the preparation of dispersions and glass bodies.

Abstract: Aqueous dispersion comprising silicon/titanium mixed oxide powder with a BET surface area of 5 to 500 m2/g which has been prepared by flame hydrolysis and has a titanium dioxide content of 0.5 to 20 wt. %, based on the powder, water and at least one pH-regulating substance which can be removed completely from the reaction mixture on heating, the aqueous dispersion having a solids content of between 40 and 80 wt. %. A green body produced therefrom with a green density of between 40 and 85%. A shaped glass article of optical quality with a coefficient of thermal expansion of not more than 0.5×10?6/K produced from the green body.