A subject of this invention is to provide a dispersion liquid of a silica-based composite particle, which can rapidly polish silica film, Si wafer or even hard-to-process material, can concurrently achieve high surface accuracy (less scratches, etc.), and can suitably be used for surface polishing of semiconductor devices including semiconductor substrate and wiring board, by virtue of its impurity-free nature. The subject is solved by a dispersion liquid of a silica-based composite particle that contains a silica-based composite particle that has a core particle mainly composed of amorphous silica, and bound thereto a ceria particle mainly composed of crystalline ceria, further has a silica film that covers them.

An aqueous hydrophobic silica dispersion includes a hydrophilic particulate silica, a hydrophobic particulate silica having a methanol number of at least 60, and a dispersant having at least one cationic or cationizable group and an HLB ratio of 2 to 20.

The present invention aims to provide a dispersant and a dispersion composition that exhibit high dispersing ability for nano-carbons such as, in particular, CNTs. The dispersant according to the present invention includes a polyalkylene oxide having a structural unit of the following chemical formula (1).

##STR00001##

In the chemical formula (1), L.sup.1 and L.sup.2 are each a straight-chain alkylene group that may have a substituent, Z is a linking group that links L.sup.1 and Ar, or alternatively, Z may not be present and L.sup.1 and Ar may be linked directly to each other, and Ar is represented by the following chemical formula (1a), (1b), or (1c).

##STR00002##

The invention provides silica particles, formed from an alkoxysilane serving as a raw material, characterized in that the silica particles satisfy the following requirements (a) to (c): (a) the silica particles have an alkali metal element content of 5 ppm or less, with respect to the silica solid content; (b) the silica particles exhibit a moisture absorption of 0.25 mg/m.sup.2 or less at 50% relative humidity, and a refractive index, as determined through the liquid immersion method, of 1.450 to 1.460; and (c) the silica particles have a mean primary particle size, derived from a specific surface area as determined through the nitrogen adsorption method, of 10 to 100 nm.

The invention relates to a process for producing a paste-like SiO.sub.2 composition using an SiO.sub.2 slip which allows simple intermediate storage and transport conditions without the processability of the slip to give the paste-like SiO.sub.2 composition being impaired thereby. According to the invention, it is for this purpose proposed that a homogeneous SiO.sub.2 base slip be subjected to a drying step to form a dry SiO.sub.2 composition and subsequently be processed further by means of a remoistening step to give the paste-like SiO.sub.2 composition, where the remoistening step comprises the addition of liquid to the dry SiO.sub.2 composition to form a paste-like kneadable SiO.sub.2 composition having a solids content of more than 85% by weight. The invention further relates to the use of a paste-like SiO.sub.2 composition as repair composition.

The present invention relates to a method for producing a silica aerogel blanket having excellent surface modification efficiency and high hydrophobicity while not containing residual chlorine, and to a silica aerogel blanket produced thereby and not containing residual chlorine.

Surface-treated fumed silica, with a tribo-electro static charge of 500 C/g to +500 C/g, a ratio of the tribo-electro static charge to BET surface area of 3.5 C/m.sup.2 to +3.5 C/m.sup.2, a methanol wettability of at least 20% by volume methanol in methanol/water mixture, a ratio of carbon content to BET surface area of at most 0.020 wt. %*g/m.sup.2, a process for its preparation and the use thereof.

The present invention relates to a method for producing a silica aerogel blanket having excellent surface modification efficiency and high hydrophobicity while not containing residual chlorine, and to a silica aerogel blanket produced thereby and not containing residual chlorine.