The present invention relates to a method for preparing a spherical silica powder filler, comprising the following steps: performing hydrolytic condensation on an organic silicon compound to obtain polysiloxane precipitate, wherein the organic silicon compound comprises silane having the chemical formula of (R.sub.1).sub.a(R.sub.2).sub.b(R.sub.3).sub.c(Si(X).sub.d, wherein R.sub.1, R.sub.2, and R.sub.3 are independently selected C1-18 hydrocarbyl groups or hydrogen atoms; X is a hydrolysable functional group; a, b, and c are 0, 1, 2, or 3; d is 1, 2, 3, or 4; and a+b+c+d=4; smashing and drying the polysiloxane precipitate to obtain siloxane angular powder; and melting and spherifying the siloxane angular powder into the spherical silica powder filler. The present invention also provides a spherical silica powder filler obtained by the method and an application thereof. The present invention takes the organic silicon compound as the starting material, and the resulting spherical silica powder filler does not contain radioactive elements such as uranium and thorium, and therefore, the requirement of low radioactivity is satisfied.

Disclosed is a black powder comprising silica particles that contain carbon. Each of the silica particles is single-layered. The content of carbon contained in the surfaces of the silica particles measured by an X-ray photoelectron spectroscopy is 1% by mass or less.

The present disclosure relates to a furnace for manufacturing a glass particle deposit by depositing glass particles generated from a glass raw material. The furnace includes two or more portions that are not fixed to each other in an upper-lower direction which is an axial direction of the glass particle deposit. The two or more portions include a first portion and a second portion which are independently formed, and the two or more portions have a structure in which the first portion and the second portion do not interfere with each other when the first portion is deformed by thermal expansion.

To reduce scratches during polishing while ensuring an appropriately high polishing rate, provided are a silica for CMP satisfying the following (A) to (C), an aqueous dispersion using a silica for CMP, and a method of producing a silica for CMP: (A) a BET specific surface area of 40 m.sup.2/g or more and 180 m.sup.2/g or less; (B) a particle density measured by a He-gas pycnometer method of 2.24 g/cm.sup.3 or more; and (C) a coefficient of variation in primary particle diameter calculated by TEM/image analysis of 0.40 or less.

Fumed silica having a BET surface area of 20015 m2/g, a grindometer value of less than 30 m and a median value by PCS of 65 to 85 nm is prepared by grinding a fumed silica having a surface area of 20025 m2/g, and silicone rubber containing this silica.

The present disclosure provides a system for generating fumed silica particles for manufacturing of an optical fiber preform. The system includes a generator and a plurality of inlets connected with the generator. The generator includes a plurality of burners. The plurality of inlets include a first inlet, a second inlet, a third inlet and a fourth inlet. The first inlet provides passage for flow of a precursor material to the generator. The second inlet provides passage for flow of a first gas to the generator. The third inlet provides passage for flow of a second gas to the generator. The fourth inlet provides passage for flow of a carrier gas to the generator. The plurality of burners enables a chemical reaction between the precursor material, the first gas and the second gas that facilitates the generation of the fumed silica particles.

Silica particles have an average pore volume of nanoscale pores of 5.3 nm.sup.3 or less as measured by positron annihilation spectroscopy. The silica particles may have an average pore volume of atomic-scale pores of 0.33 nm.sup.3 or more as measured by positron annihilation spectroscopy. The silica particles may have a volume of pores having a diameter of 2 nm or less of 0.0070 cm.sup.3/g or less as measured by a nitrogen gas adsorption method.

The present invention relates to a process for preparing a metal oxide, comprising a) spraying a liquid raw material comprising at least one metal compound by mixing it with a gas to form an aerosol; b) forming a gaseous reaction mixture from the aerosol obtained in step a) by complete evaporation thereof; c) converting the gaseous reaction mixture obtained in step b) to metal oxide in the presence of oxygen.

A heat control member comprises a mixture of a) silica aerogel particles having particle sizes in a range from 0.1 mm to 5 mm and b) hydrophobic silica-containing particles having a methanol number of at least 30 and a particle size D50 of 100 microns or less, the mixture having a particle size distribution of silica-containing particles having at least two peaks. The silica aerogel particles and hydrophobic silica containing particles are present in a ratio from 1:99 to 99:1; and the heat control member has a thermal conductivity at 25 C. of from 5 to 30 mW/m.K and a thickness of 0.1-10 mm.