The present invention relates to a method for producing a silica aerogel and a silica aerogel produced thereby. More specifically, a first water glass solution is used to form a first silica wet gel, and then a second water glass solution is additionally added to form a second silica wet gel organically bonded to the first silica wet gel which serves as a basic skeleton, so that a silica aerogel with enhanced physical properties is formed to increase the resistance to shrinkage in ambient drying, and the concentration of silicon dioxide in each of the first and second water glass solutions is controlled, thereby providing a method for producing a silica aerogel by which a silica aerogel having a specific tap density and controllable density can be produced, and also providing a silicon aerogel produced by the method.

The present invention relates to a hydrophilic silica aerogel blanket for ultra-high temperature insulation, a production method thereof, and a construction method thereof. More specifically, the present invention provides a production method a hydrophilic silica aerogel blanket, the method capable of strengthening the structure of a silica gel by adding a basic catalyst in an aging step, reducing processing time and cost by omitting a surface modification step, thereby reducing manufacturing cost, and suppressing the generation of a bad odor during construction by fundamentally blocking a volatile organic compound (VOC), a hydrophilic silica aerogel blanket produced thereby, and a construction method of a hydrophilic silica aerogel blanket, the method capable of suppressing the generation of a bad odor when constructing the hydrophilic aerogel blanket on an ultra-high temperature piping equipment, and at the same time, preventing the loss of heat insulation performance due to moisture in the air.

A positive electrode active material contains conductive silica and sulfur filled in pores of the conductive silica. The conductive silica is preferably a composite containing silica gel and fine particulate carbon dispersed in the silica gel. The positive electrode includes the aforementioned positive electrode active material. A rechargeable battery includes the aforementioned positive electrode.

An abrasive type silica with low refractive index and high transparency, a preparation method and an application thereof are disclosed. The preparation method of the present invention includes the following steps: S1, a sodium sulfate solution is added into a reaction tank, the solution is heated to 80-95 C., a sodium silicate solution and a sulfuric acid solution are added at the same time while stirring, the dropping rate of the sodium silicate solution is controlled at 13-15 m.sup.3/h, the dropping rate of the sulfuric acid solution is controlled to ensure that the pH value of the reaction process is 3.0-4.5, and stirring is continued for 10-15 min after the adding is finished; and S2, the formed silica is filter pressed, washed, spray-dried and airflow crushed to prepare the abrasive type silica with low refractive index and high transparency.

An abrasive type silica with low refractive index and high transparency, a preparation method and an application thereof are disclosed. The preparation method of the present invention includes the following steps: S1, a sodium sulfate solution is added into a reaction tank, the solution is heated to 80-95 C., a sodium silicate solution and a sulfuric acid solution are added at the same time while stirring, the dropping rate of the sodium silicate solution is controlled at 13-15 m.sup.3/h, the dropping rate of the sulfuric acid solution is controlled to ensure that the pH value of the reaction process is 3.0-4.5, and stirring is continued for 10-15 min after the adding is finished; and S2, the formed silica is filter pressed, washed, spray-dried and airflow crushed to prepare the abrasive type silica with low refractive index and high transparency.

The present invention relates to a method of preparing ultra-pure silicon carbide in which a super-porous spherical silica aerogel is used as a silica raw material. By preparing the silica aerogel particles using low-cost water glass, a reaction area with respect to a carbon raw material is increased to enable low-temperature synthesis of silicon carbide, the size and shape of silicon carbide powder may be uniformly controlled to prepare ultra-pure silicon carbide, and economic efficiency and productivity of the silicon carbide synthesis may be improved. Thus, it is expected that the silicon carbide powder prepared by the preparation method of the present invention may be provided as an optimized raw material for the preparation of silicon carbide sintered body and single crystal (ingot).

The present invention relates to a method of preparing ultra-pure silicon carbide in which a super-porous spherical silica aerogel is used as a silica raw material. By preparing the silica aerogel particles using low-cost water glass, a reaction area with respect to a carbon raw material is increased to enable low-temperature synthesis of silicon carbide, the size and shape of silicon carbide powder may be uniformly controlled to prepare ultra-pure silicon carbide, and economic efficiency and productivity of the silicon carbide synthesis may be improved. Thus, it is expected that the silicon carbide powder prepared by the preparation method of the present invention may be provided as an optimized raw material for the preparation of silicon carbide sintered body and single crystal (ingot).

Provided is a method for producing silica aerogel using a pre-hydrolyzed polysilicate, the method comprising: applying a polysilicate as a reactant when synthesizing of the pre-hydrolyzed polysilicate; and hydrating the polysilicate in the presence of an alcohol-based compound, which is generated through the hydration of a compound of Formula 1 without the addition of a separate alcohol-based solvent:

R.sub.1Si(OR.sub.2).sub.3[Formula 1]

wherein R.sub.1 is an alkyl having 1 to 20 carbon atoms, a cycloalkyl having 3 to 20 carbon atoms, or a vinyl having 1 to 20 carbon atoms, and each R.sub.2 is independently an alkyl having 1 to 20 carbon atoms.

Provided is a method for producing silica aerogel using a pre-hydrolyzed polysilicate, the method comprising: applying a polysilicate as a reactant when synthesizing of the pre-hydrolyzed polysilicate; and hydrating the polysilicate in the presence of an alcohol-based compound, which is generated through the hydration of a compound of Formula 1 without the addition of a separate alcohol-based solvent:

R.sub.1Si(OR.sub.2).sub.3[Formula 1]

wherein R.sub.1 is an alkyl having 1 to 20 carbon atoms, a cycloalkyl having 3 to 20 carbon atoms, or a vinyl having 1 to 20 carbon atoms, and each R.sub.2 is independently an alkyl having 1 to 20 carbon atoms.

The present invention relates to a method of preparing a high hydrophobic silica aerogel having a high specific surface area and a low tap density, and a hydrophobic silica aerogel prepared thereby. The method of preparing a hydrophobic silica aerogel according to the present invention may have good productivity and economic efficiency, because preparation time is reduced by simultaneously performing surface modification, gelation, and solvent substitution in a single step, and may control a degree of hydrophobicity of the prepared silica aerogel by controlling a surface modification reaction by including a step of adding ammonium hydroxide. Thus, the preparation method according to the present invention and the hydrophobic silica aerogel are suitable for industries that need the method and the hydrophobic silica aerogel, particularly, industries that need a silica aerogel having high hydrophobicity or industries that need a silica aerogel having various degrees of hydrophobicity.