Abstract: Fumed silicon dioxide powder with a BET surface area of 20 to 35 m2/g, characterized in that a) the number-based median particle diameter is 60 to 150 nm, and b) the proportion of particles with a diameter of 200 nm or more is at most 10%, and c) the proportion of particles with a diameter of up to 60 nm is at most 20%, based in each case on the total number of particles.

Abstract: Aluminum oxide powder in the form of aggregates of primary-particles, which has a BET surface area of from 10 to 90 m2/g and comprises as crystalline phases, in addition to gamma-aluminum oxide and/or theta-aluminum oxide, at least 30% of delta-aluminum oxide. It is prepared by vaporizing aluminum chloride and burning the vapor together with hydrogen and air, the ratio of primary air/secondary air being 0.01 to 2, the exit speed vB of the reaction mixture from the burner being at least 10 m/s, the lambda value being 1 to 4, the gamma value being 1 to 3 and the value of gamma*vB/lambda being greater than or equal to 55. Dispersion comprising the aluminum oxide powder. Coating composition comprising the dispersion.

Abstract: Fumed silicon dioxide powder with a BET surface area of 20 to 35 m2/g, characterized in that a) the number-based median particle diameter is 60 to 150 nm, and b) the proportion of particles with a diameter of 200 nm or more is at most 10%, and c) the proportion of particles with a diameter of up to 60 nm is at most 20%, based in each case on the total number of particles.

Abstract: Pyrogenic silicon-titanium mixed oxide powder having • a BET surface area of 200 to 400 m2/g, • a DBP number/BET surface area ratio of 0.5 to 1.2, • a silicon dioxide content of 93.5 to 95.4% by weight and a titanium dioxide content of 4.6 to 6.5% by weight, where the sum of the contents is greater than 99.7% by weight. Dispersion comprising the pyrogenic silicon-titanium mixed oxide powder. Process for preparing a titanium-containing zeolite proceeding from powder or dispersion.

Abstract: Zirconium dioxide powder in the form of aggregated primary particles, having a BET surface area of 30 to 150 m2/g and a Berger whiteness of at least 88%. It is prepared by atomizing a solution which comprises an organic zirconium compound and mixing it with a combustion gas and air and allowing the mixture to burn in a flame into a reaction chamber surrounded by a casing, where the temperature in the reaction chamber and along the side of the wall of the casing facing the reaction chamber is at least 500° C. Dispersion comprising the zirconium dioxide powder. Use of the zirconium dioxide powder and of the dispersion for producing ceramics.

Abstract: Aluminium oxide powder produced by flame hydrolysis and consisting of aggregates of primary particles, having a BET surface area of from 100 to 250 m2/g, a dibutyl phthalate absorption of from 50 to 450 g/100 g of aluminium oxide powder, which powder shows only crystalline primary particles in high-resolution TEM pictures.

Abstract: 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. It is prepared by mixing at least one silicon compound in vapor form, a free-oxygen-containing gas and a combustible gas in a burner of known construction, igniting this gas mixture at the mouth of the burner and burning it in the flame tube of the burner, separating the solid obtained from the gas mixture and optionally purifying, wherein the oxygen content of the free-oxygen-containing gas is adjusted so that the lambda value is greater than or equal to 1, the gamma value is between 1.2 and 1.8, the throughput is between 0.1 and 0.3 kg SiO2/m3 of core gas mixture and the mean normalized rate of flow of gas in the flame tube at the level of the mouth of the burner is at least 5 m/s. The powder can be used as a filler.

Abstract: Flame-hydrolytically produced titanium dioxide powder that is present in the form of aggregates of primary particles, and has a BET surface of 20 to 200 m²/g, a half width (HW) [nm] of the primary particle distribution of HW = a×BETf where a = 670×10?9 m³/g and ?1.3 ≤ f ≤ ?1.0 and the proportion of particles with a diameter of more than 45 &mgr;m lies in a range from 0.0001 to 0.05 wt. %. The powder is produced by a process in which a titanium halide is vapourised at temperatures of less than 200°C.

Abstract: Aluminium oxide powder in the form of aggregates of primary- particles, which has a BET surface area of from 10 to 90 m2/g and comprises as crystalline phases, in addition to gamma- aluminium oxide and/or theta-aluminium oxide, at least 30% of delta-aluminium oxide. It is prepared by vaporizing aluminium chloride and burning the vapour together with hydrogen and air, the ratio of primary air/secondary air being 0.01 to 2, the exit speed vB of the reaction mixture from the burner being at least 10 m/s, the lambda value being 1 to 4, the gamma value being 1 to 3 and the value of gamma * vB/lambda being greater than or equal to 55. Dispersion comprising the aluminium oxide powder. Coating composition comprising the dispersion.

Abstract: Pyrogenically produced silica powder with a BET surface of 30 to 90 m2/g, a dibutyl phthalate number of at least 80 and a tamped density of no more than 110 g/l. It is produced in that at least one vaporous silicon compound, a gas containing free oxygen and a combustible gas are mixed together in a closed burner and then burnt in a flame in the flame tube of the burner, the solid obtained is separated from the gas mixture and optionally purified, wherein the oxygen content of the gas containing free oxygen is adjusted such that the lambda value is greater than or equal to 1, and the gamma value is between 1.2 and 1.8. It can be used in toner applications.

Abstract: Silicon-titanium mixed oxide powder, dispersion thereof and titanium-containing zeolite prepared therefrom Pyrogenic silicon-titanium mixed oxide powder, having a BET surface area of 200 to 400 m2/g, a silicon dioxide content of 97.0±1.5% by weight, a titanium dioxide content of 3.5±1.0% by weight, the sum of silicon dioxide content and titanium dioxide content being greater than 99.7% by weight. Dispersion comprising this powder. Process for the preparation of a titanium-containing zeolite starting from powder or dispersion.

Abstract: A powder mixture consisting of zinc/titanium mixed oxide particles, titanium dioxide particles and zinc oxide particles, wherein the zinc/titanium mixed oxide particles have a composition according to the formula (ZnO)1-x(TiO2)x, where 0.01<x<0.99, and are obtained from a thermal process and the powder mixture exhibits remission which, in the UV range from 320 to 400 nm, is lower than that of titanium dioxide and, in the UV range below 320 nm, is lower than that of zinc oxide. The powder mixture may be produced by introducing into a flame, as is used for the production of pyrogenic metal oxides by means of flame hydrolysis, an aerosol of a zinc compound, homogeneously mixing said aerosol with the flame hydrolysis gas mixture, allowing the aerosol/gas mixture to react in a flame, separating the solid reaction products from the stream of gas and then performing thermal treatment.

Abstract: Silicon-titanium mixed oxide powder produced by flame hydrolysis, which consists of aggregates of primary particles, with a BET surface area of 90±15 m2/g, a titanium dioxide proportion of 50±8 wt. % and an anatase/rutile ratio of 60:40 to 70:30. It is produced in that a mixture of silicon halide, titanium halide, hydrogen and primary air is ignited in a burner and the flame is burned into a reaction chamber closed off from the surrounding air, and secondary air and a gas, which increases the temperature in the reaction chamber by combustion and/or which slows down the cooling in the reaction chamber because of low heat transfer, are additionally introduced into the reaction chamber. It can be used in toner compositions.

Abstract: A silicon-titanium mixed oxide powder contains aggregates of primary particles selected from amorphous silicon dioxide particles, crystalline titanium dioxide particles, and silicon-titanium mixed oxide particles each having an amorphous silicon dioxide fraction and a crystalline titanium dioxide fraction. The silicon-titanium mixed oxide particles predominate in the powder. The powder exhibits a BET surface area of from 20 to 200 m2/g, and a titanium dioxide content in a range of from greater than 10 wt. % to less than 70 wt. %. An X-ray diffractogram of the powder exhibits the diffraction patterns of rutile and anatase, with a rutile/anatase ratio of from 2:98 to 98:2. The powder can be produced by vaporizing a silicon halide and a titanium halide at temperatures of less than 180° C.

Abstract: Silicon-titanium mixed oxide powder produced by flame hydrolysis, which consists of aggregates of primary particles, with a BET surface area of 90 15 m²/g, a titanium dioxide proportion of 50 8 wt. % and an anatase/rutile ratio of 60:40 to 70:30. It is produced in that a mixture of silicon halide, titanium halide, hydrogen and primary air is ignited in a burner and the flame is burned into a reaction chamber closed off from the surrounding air, and secondary air and a gas, which increases the temperature in the reaction chamber by combustion and/or which slows down the cooling in the reaction chamber because of low heat transfer, are additionally introduced into the reaction chamber It can be used in toner compositions.

Abstract: Flame-hydrolytically produced titanium dioxide powder that is present in the form of aggregates of primary particles, and has a BET surface of 20 to 200 m²/g, a half width (HW) [nm] of the primary particle distribution of HW = a×BETf where a = 670x10?9 m³/g and ?1.3 ≤ f ≤ ?1.0 and the proportion of particles with a diameter of more than 45 &mgr;m lies in a range from 0.0001 to 0.05 wt. %. The powder is produced by a process in which a titanium halide is vapourised at temperatures of less than 200°C.

Abstract: Silicon-titanium mixed oxide powder prepared by flame hydrolysis, having a ratio by weight of silicon dioxide/titanium dioxide, which is greater on the surface of the primary particles than that within the total primary particle. It is prepared by a flame hydrolysis process, in that a stream consisting of a vaporous titanium dioxide precursor and oxygen or an oxygen-containing gas and hydrogen, and a second stream consisting of a vaporous silicon dioxide precursor and a carrier gas consisting of oxygen, an oxygen-containing gas and/or an inert gas, are guided separately into the reaction chamber of a burner such as is known for the preparation of pyrogenic oxides, and are burnt here, the solid mixed oxide powder and hot gases are subsequently cooled, and the gases are separated from the solid. The powder may be used, for example, for the preparation of sunscreen preparations.

Abstract: A silicon-titanium mixed oxide powder contains aggregates of primary particles selected from amorphous silicon dioxide particles, crystalline titanium dioxide particles, and silicon-titanium mixed oxide particles each having an amorphous silicon dioxide fraction and a crystalline titanium dioxide fraction. The silicon-titanium mixed oxide particles predominate in the powder. The powder exhibits a BET surface area of from 20 to 200 m2/g, and a titanium dioxide content in a range of from greater than 10 wt. % to less than 70 wt. %. An X-ray diffractogram of the powder exhibits the diffraction patterns of rutile and anatase, with a rutile/anatase ratio of from 2:98 to 98:2. The powder can be produced by vaporizing a silicon halide and a titanium halide at temperatures of less than 180° C.

Abstract: Silicon-titanium mixed oxide powder prepared by flame hydrolysis, having a ratio by weight of silicon dioxide/titanium dioxide, which is greater on the surface of the primary particles than that within the total primary particle. It is prepared by a flame hydrolysis process, in that a stream consisting of a vaporous titanium dioxide precursor and oxygen or an oxygen-containing gas and hydrogen, and a second stream consisting of a vaporous silicon dioxide precursor and a carrier gas consisting of oxygen, an oxygen-containing gas and/or an inert gas, are guided separately into the reaction chamber of a burner such as is known for the preparation of pyrogenic oxides, and are burnt here, the solid mixed oxide powder and hot gases are subsequently cooled, and the gases are separated from the solid. The powder may be used, for example, for the preparation of sunscreen preparations.