A silica particle dispersion liquid includes a silica particle that satisfies (i) to (iii) below: (i) an average particle diameter d is 5 to 300 nm; (ii) an occlusion amount of a basic substance per 1 g of the particle is 2 mg or more; and (iii) a Sears number Y exceeds 12.0.

A silica particle dispersion liquid includes a silica particle that satisfies (i) to (iii) below: (i) an average particle diameter d is 5 to 300 nm; (ii) an occlusion amount of a basic substance per 1 g of the particle is 2 mg or more; and (iii) a Sears number Y exceeds 12.0.

Provided is a production method of a silica particle dispersion liquid which includes, preparing a linked silica particle by adding a liquid A containing alkoxysilane and a liquid B containing an alkali catalyst to a liquid containing water, an organic solvent, and an alkali catalyst in a container. The preparing a linked silica particle includes initially adding an alkali catalyst, the initially adding an alkali catalyst includes decreasing a molar ratio of an alkali catalyst to silica in the liquid in the container to 0.15 to 0.60 by adding the liquid A containing alkoxysilane to the liquid in the container, and increasing the molar ratio by 0.2 or more by adding the liquid B to the liquid having the decreased molar ratio in the container.

Provided is a production method of a silica particle dispersion liquid which includes, preparing a linked silica particle by adding a liquid A containing alkoxysilane and a liquid B containing an alkali catalyst to a liquid containing water, an organic solvent, and an alkali catalyst in a container. The preparing a linked silica particle includes initially adding an alkali catalyst, the initially adding an alkali catalyst includes decreasing a molar ratio of an alkali catalyst to silica in the liquid in the container to 0.15 to 0.60 by adding the liquid A containing alkoxysilane to the liquid in the container, and increasing the molar ratio by 0.2 or more by adding the liquid B to the liquid having the decreased molar ratio in the container.

Aqueous dispersion containing a hydrophilic metal oxide powder comprising a metal oxide and a surface modification of the metal oxide, wherein a) the metal oxide is selected from the group consisting of TiO.sub.2, ZrO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Sb.sub.2O.sub.3, WO.sub.3, CeO.sub.2 and mixed oxides thereof and b) the surface modification b1) comprises silicon atoms and aluminum atoms and b2) the silicon atoms are at least partly bonded to a hydrocarbon radical via a C atom and b3) the Al/Si molar ratio of the surface modification is 1:2-1:20.

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.

A lost circulation material (LCM) is provided having an alkaline nanosilica dispersion and a polyester activator. The alkaline nanosilica dispersion and the polyester activator may form a gelled solid after interaction over a contact period. Methods of lost circulation control using the LCM are also provided.

The present invention provides a boron-containing silica dispersion having better dispersion stability at a high concentration, and higher binding properties between boron and silica than conventional dispersions. The present invention is a boron-containing silica dispersion containing amorphous silica particles containing boron atoms and a dispersion medium; the boron-containing amorphous silica particles having an average particle size of 10 to 100 nm, as determined from 40 particles selected at random in a transmission electron micrograph; the boron-containing silica dispersion having a solids content of 5 to 30 mass %; and the boron-containing silica dispersion having a sedimentation rate of the particles of 4% or less, when the boron-containing silica dispersion is left standing for 1000 hours, and proportions of SiO.sub.2 and B.sub.2O.sub.3 of 90.0 to 99.8 mass % and 0.2 to 10.0 mass %, respectively, in 100 mass % of a total of SiO.sub.2 and B.sub.2O.sub.3, all terms of oxide, when the boron-containing silica dispersion is subjected to ultrafiltration by the following method and dried; <Ultrafiltration method> washing is performed by sequentially adding pure water in an amount of 6 times the volume of the boron-containing silica dispersion at a flow rate of a liquid fed of 3660 ml/minute using an ultrafiltration membrane with a fraction molecular weight of 13,000.

A polishing composition that can not only achieve high polishing speed, but also can improve the surface smoothness (surface quality) of a polished substrate and reduce defects is provided. That is, provided is a polishing composition comprising silica particles and a water soluble polymer, wherein the contained silica particles satisfy the following requirements (a) to (c): (a) the primary particle diameter based on the specific surface area is 5 to 300 nm; (b) the coefficient of variation in the particle diameter is 10% or less; and (c) the Sears number Y is 10.0 to 12.0.

A polishing composition that can not only achieve high polishing speed, but also can improve the surface smoothness (surface quality) of a polished substrate and reduce defects is provided. That is, provided is a polishing composition comprising silica particles and a water soluble polymer, wherein the contained silica particles satisfy the following requirements (a) to (c): (a) the primary particle diameter based on the specific surface area is 5 to 300 nm; (b) the coefficient of variation in the particle diameter is 10% or less; and (c) the Sears number Y is 10.0 to 12.0.