The invention relates to a process for the preparation of a novel precipitated silica, wherein: a silicate is reacted with an acidifying agent, so as to obtain a silica suspension; said silica suspension is filtered, so as to obtain a filter cake; said filter cake is subjected to a liquefaction operation, in the absence of an aluminium compound; wherein a mixture of polycarboxylic acids is added to the filter cake, during or after the liquefaction operation. It also relates to novel precipitated silicas and to their uses.

The invention relates to a process for the preparation of a novel precipitated silica, wherein: a silicate is reacted with an acidifying agent, so as to obtain a silica suspension; said silica suspension is filtered, so as to obtain a filter cake; said filter cake is subjected to a liquefaction operation, in the absence of an aluminium compound; wherein a mixture of polycarboxylic acids is added to the filter cake, during or after the liquefaction operation. It also relates to novel precipitated silicas and to their uses.

Modified precipitated silica is produced in a one pot synthesis by forming precipitated silica and modifying with an organosiliconate. The modified precipitated silica is washed following preparation, affording a modified precipitated silica with low levels of ionic substances.

A method for producing new nanomaterials, 80 to 100 mol % of which are composed of TiO.sub.2 and 0 to 20 mol % are composed of another metal or semi-metal oxide that has a specific surface of 100 to 300 m.sup.2.Math.g.sup.1 and 1 to 3 hydroxyl groups per nm.sup.2.

A method for producing new nanomaterials, 80 to 100 mol % of which are composed of TiO.sub.2 and 0 to 20 mol % are composed of another metal or semi-metal oxide that has a specific surface of 100 to 300 m.sup.2.Math.g.sup.1 and 1 to 3 hydroxyl groups per nm.sup.2.

The present invention aims to provide a technique for preparing a complex fiber covered by silica and/or alumina at a high coverage ratio. According to the present invention, complex fibers comprising silica and/or alumina deposited on the surface of a fiber at a high coverage ratio can be prepared by synthesizing silica and/or alumina on the fiber while maintaining the pH of the reaction solution containing the fiber at 4.6 or less.

The present invention aims to provide a technique for preparing a complex fiber covered by silica and/or alumina at a high coverage ratio. According to the present invention, complex fibers comprising silica and/or alumina deposited on the surface of a fiber at a high coverage ratio can be prepared by synthesizing silica and/or alumina on the fiber while maintaining the pH of the reaction solution containing the fiber at 4.6 or less.

Modified precipitated silica is produced in a one pot synthesis by forming precipitated silica and modifying with an organosiliconate. The modified precipitated silica is washed following preparation, affording a modified precipitated silica with low levels of ionic substances.

To provide hollow silica particles having a dense silica shell layer.

A method for producing hollow silica particles, which comprises:

adjusting the pH of an oil-in-water emulsion containing an aqueous phase, an oil phase and a surfactant to at most 3.0 and adding a first silica material to the oil-in-water emulsion,

adding a second silica material to the emulsion having the first silica material added, at its pH of at least 8, in the presence of alkali metal ions, to obtain a hollow silica precursor dispersion, and

obtaining a hollow silica precursor from the hollow silica precursor dispersion and obtaining hollow silica particles from the hollow silica precursor.

The object of the present invention is to provide silica particles which can provide a silica particle dispersion exhibiting excellent uniformity. The present invention is silica particles having an average primary particle diameter d.sub.BET calculated from a specific surface area by a BET method of 1 nm or more and 100 nm or less and a ratio (d.sub.DLS/d.sub.BET) of an average secondary particle diameter d.sub.DLS measured by a dynamic light scattering method to the d.sub.BET of 1.2 or less. The silica particles of the present invention preferably have a coefficient of variation in a particle diameter measured using a transmission electron microscope at a magnification of 200,000 of 20% or less.