Abstract: Process for producing a silicon-carbon composite powder in which a) a gas stream A containing at least one starting compound of silicon selected from the group consisting of SiH4, Si2H6 and Si3H8, and b) a gas stream B containing at least one starting compound of carbon selected from the group consisting of methane, ethane, propane, ethylene and acetylene are reacted in a hot wall reactor at a temperature of less than 900° C., the reaction mixture is cooled or allowed to cool and the pulverulent reaction product is separated from gaseous materials.

Abstract: The invention relates to a method for producing a shaped body that contains at least 85 vol. % crystalline silicon carbide and at most 15 vol. % silicon, comprising the following steps: a) providing a powdered mixture that contains at least 60 vol. % amorphous silicon carbide and at most 40 vol. % silicon having a crystallite size of 3-50 nm; b) shaping the mixture by b1) hot pressing, or b2) compacting at room temperature and subsequent sintering or hot pressing, wherein the sintering or hot pressing is carried out in an inert gas or vacuum at a temperature of at least 1400° C. The volume ratio SiC:Si in the powdered mixture is 95:5-99:1.

Abstract: Organofunctional silicon particles are covalently functionalized on their surface with at least one organic compound, for example a plurality of —O—(C1-C48)-alkyl compounds. The functionalization of the surface of the silicon particles makes it possible to adjust the properties of fluids in terms of their profile of properties by addition of the modified silicon particles. For instance, the alkoxy-functionalized silicon particles may preferably be added to a motor oil as additives for reducing viscosity.

Abstract: Silicon-containing particles are used for protection of industrial materials, such as electrooptical layers or electrooptical components, from electromagnetic radiation in the UV range and optionally in the visible as far as the IR range, wherein the particles take the form of primary particles having a particle size in the range from 1 to 100 nm and may optionally take the form of clusters of the primary particles. A particular advantage is the possibility of matching the absorption of the electromagnetic radiation to the wavelength region to be absorbed that is of interest in a defined manner via the particle size and the particle size distribution. The silicon-containing particles can be used as biocompatible and biodegradable UV protection in industrial applications and compositions for industrial applications as formulations, such as preferably in coating compositions, such as paint.

Abstract: Silicon-containing particles are used for protection of human cells from electromagnetic radiation in the UV range and optionally in the visible as far as the IR range, where the particles preferably take the form of clusters of primary particles having a particle size in the range from 5 to 100 nm. A particular advantage is the possibility of matching the absorption of the electromagnetic radiation to the wavelength region to be absorbed in a defined manner via the particle size. The silicon-containing particles can be used for biocompatible and biodegradable UV protection in cosmetic or medical formulations, such as preferably a sunscreen, or else in a cosmetic formulation for the UV protection of hair.

Abstract: A method of fractionating a dispersion of oxidic nanoparticles wherein at least one step of the method is a membrane crossflow filtration step, the flow of the dispersion over the membrane being brought about by means of driven rotating parts; and dispersions of oxidic nanoparticles that are obtainable by the method.

Abstract: Aqueous dispersion comprising cerium oxide and silicon dioxide, obtainable by first mixing a cerium oxide starting dispersion and a silicon dioxide starting dispersion while stirring, and then dispersing at a shear rate of 10000 to 30000 s?1, wherein a) the cerium oxide starting dispersion—contains 0.5 to 30% by weight of cerium oxide particles as the solid phase, —a d5o of the particle size distribution of 10 to 100 nm—and has a pH of 1 to 7, and b) the silicon dioxide starting dispersion—contains 0.1 to 30% by weight of colloidal silicon dioxide particles as the solid phase, has a d5o of the particle size distribution of 3 to 50 nm and has a pH of 6 to 11.5, d) with the proviso that the d5o of the particle size distribution of the cerium oxide particles is greater than that of the silicon dioxide particles, the cerium oxide/silicon dioxide weight ratio is >1 and the amount of cerium oxide starting dispersion is such that the zeta potential of the dispersion is negative.

Abstract: Aqueous cerium oxide dispersion Aqueous cerium oxide dispersion, containing 5 to 60% by weight cerium oxide. It can be used to polish SiO2 in the semiconductor industry.

Abstract: Process for the production of a metal oxide powder having a BET surface area of at least 20 m2/g by reacting an aerosol with oxygen in a reaction space at a reaction temperature of more than 700° C. and then separating the resulting powder from gaseous substances in the reaction space, wherein the aerosol is obtained by atomisation using a multi-component nozzle of at least one starting material, as such in liquid form or in solution, and at least one atomising gas, the volume-related mean drop diameter D30 of the aerosol is from 30 to 100 ?m and the number of aerosol drops larger than 100 ?m is up to 10%, based on the total number of drops, and metal oxide powder obtainable by this process.

Abstract: Surface-modified superparamagnetic oxidic particles, characterized by the following physicochemical characteristics: BET surface area 20 to 75 m2/g; Carbon content 0.5 to 6.0% by weight; Tamped density 150 to 500 g/l; Chlorine content 50 to 1000 ppm; Drying loss 0.1 to 4.0% by weight are prepared by contacting the oxides with the surface modifier either by spraying or vapour deposition and then heat-treating them. The surface-modified oxidic particles can be used as a filler in adhesives. Further fields of application are use for data carriers, as a contrast agent in imaging processes, for biochemical separation and analysis processes, for medical applications, as an abrasive, as a catalyst or as a catalyst support, as a thickener, for thermal insulation, as a dispersing assistant, as a flow assistant and in ferrofluids.

Abstract: Process for polishing silicon surfaces, in which a dispersion which comprises cerium oxide particles, at least one polymeric, anionic dispersing additive and at least one oxidizing agent and which has a pH of 7 to 10.5 is used, said cerium oxide particles having a positive charge and polymeric, anionic dispersing additive and oxidizing agent being soluble in the liquid phase of the dispersion.

Abstract: A dispersion comprising particles of cerium oxide and sheet silicate, where—the zeta potential of the sheet silicate particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, —the mean diameter of the cerium oxide particles is not more than 200 nm sheet silicate particles is less than 100 nm, —the proportion, based in each case on the total amount of the dispersion, of cerium oxide particles is from 0.1 to 5% by weight sheet silicate particles is from 0.01 to 10% by weight and—the pH of the dispersion is from 3.5 to <7.5.

Abstract: A dispersion comprising particles of cerium oxide and particles of cerium oxide and colloidal silicon dioxide, where —the zeta potential of the silicon dioxide particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, —the mean diameter of the cerium oxide particles is not more than 200 nm silicon dioxide particles is less than 100 nm, —the proportion, based in each case on the total amount of the dispersion, of cerium oxide particles is from 0.1 to 5% by weight silicon dioxide particles is from 0.01 to 10% by weight and —the pH of the dispersion is from 3.5 to <7.5.

Abstract: A method of fractionating a dispersion of oxidic nanoparticles wherein at least one step of the method is a membrane crossflow filtration step, the flow of the dispersion over the membrane being brought about by means of driven rotating parts; and dispersions of oxidic nanoparticles that are obtainable by the method.

Abstract: A dispersion comprising particles of cerium oxide and sheet silicate and one or more aminocarboxylic acids and/or salts thereof, where the zeta potential of sheet silicate particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, the mean diameter of the•cerium oxide particles is not more than 200 nm•sheet silicate particles is less than 100 nm, the content, based in each case on the total amount of the dispersion, of•cerium oxide particles is from 0.1 to 5% by weight•sheet silicate particles is from 0.01 to 10% by weight and•aminocarboxylic acid or salt thereof is from 0.01 to 5% by weight and the pH of the dispersion is from 7.5 to 10.5.

Abstract: A dispersion comprising particles of cerium oxide and colloidal silicon dioxide and in each case one or more aminocarboxylic acids and/or salts thereof, where the zeta potential of the silicon dioxide particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, the mean diameter of the • cerium oxide particles is not more than 200 nm silicon dioxide particles is less than 100 nm, the content, based in each case on the total amount of the dispersion, of • cerium oxide particles is from 0.1 to 5% by weight silicon dioxide particles is from 0.01 to 10% by weight and • aminocarboxylic acid or salt thereof is from 0.01 to 5% by weight and —the pH of the dispersion is from 7.5 to 10.5.

Abstract: A dispersion comprising cerium oxide particles and colloidal silicon dioxide particles, where—the zeta potential of the silicon dioxide particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, and—the mean particle diameter of the cerium oxide particles is not more than 200 nm and that of the silicon dioxide particles is not more than 100 nm, the mean particle diameter of the cerium oxide particles being greater than that of the silicon dioxide particles—the cerium oxide/silicon dioxide weight ratio is from 1.1:1 to 100:1 and—the pH of the dispersion is from 7.5 to 10.5.

Abstract: A dispersion comprising cerium oxide particles and particles of one or more sheet silicates, where the zeta potential of the sheet silicate particles is negative and that of the cerium oxide particles is positive or equal to zero, and the zeta potential of the dispersion is negative overall, the mean particle diameter of the cerium oxide particles and the mean particle diameter of the sheet silicate particles is not more than 100 nm and the pH of the dispersion is from 7.5 to 10.5, preferably from 9 to 10.

Abstract: Aqueous cerium oxide dispersion Aqueous cerium oxide dispersion, containing 5 to 60% by weight cerium oxide. It can be used to polish SiO2 in the semiconductor industry.

Abstract: Zinc silicon oxide particles with a core-shell structure which have a Zn/Si ratio of from 2 to 75, in atom %/atom %, whose fraction of Zn, Si and O is at least 99% by weight, based on the zinc silicon oxide particles, which have a BET surface area of from 10 to 60 m2/g, a weight-averaged primary particle diameter of from 10 to 75 nm an average aggregate area of less than 40 000 nm2 and an average aggregate diameter (ECD) of less than 200 nm, whose core is crystalline and consists of aggregated primary particles of zinc oxide and whose shell surrounds the aggregated zinc oxide primary particles and consists of one or more compounds containing the elements Si and O. Dispersion, coating composition and sunscreen formulation comprise the zinc silicon oxide particles.