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.

Dispersion comprising particles of a surface-modified, hydrophilic silica, where

A) the particles of the surface-modified, hydrophilic silica comprise an aluminium atom and a hydrocarbon radical, a) the aluminium atom is bonded via an oxygen atom to a silicon atom of the particle surface, b) the hydrocarbon radical comprises a silicon atom which is bonded to a carbon atom of the hydrocarbon radical, c) possess an average particle diameter d.sub.50 in the dispersion of 40-200 nm, preferably 60-150 nm, and

B) the pH of the dispersion is 8 or more.

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

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 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.

Provided is a supercritical drying method of a silica wet gel blanket and a method for producing a silica aerogel blanket including the same, the supercritical drying method preventing a salt from being accumulated inside equipment during supercritical drying. By preventing a salt from being accumulated inside equipment during supercritical drying, it is possible to improve the operational stability of the supercritical drying process. In addition, since only a line filter needs to be separated and is easily washed, the time required for washing and the total amount of ammonia wastewater generated therefrom can be reduced, thereby improving efficiency and reducing costs.

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 stable dispersion of exfoliated layer substances is prepared through interlayer exfoliation of a layered compound. A dispersion including quaternary ammonium ions (A) each having a total carbon atom number of 15 to 45 and one or two C.sub.10-20 alkyl groups, and an anionic surfactant (B) having an ammonium ion, wherein plate-like particles (C) having an average thickness of 0.7 to 40 nm, an average major-axis length of 100 to 600 nm, an average minor-axis length of 50 to 300 nm, and a ratio of average major-axis length to average minor-axis length of 1.0 to 10.0 are dispersed in a liquid medium, and the plate-like particles (C) in the dispersion have an average particle diameter of 10 to 600 nm as measured by dynamic light scattering, and a transparent substrate using the dispersion.

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.

A supercritical drying device for preparing a silica wet gel blanket, in which the accumulation of salts inside equipment during supercritical drying is prevented. The accumulation of salts inside equipment is prevented by cooling the line filter to have an outer surface temperature in a range of 0 C.-50 C. resulting in improved operational stability of the supercritical drying process. In addition, because a line filter can be separated and easily cleaned, the time required for cleaning and the total amount of ammonia wastewater from the cleaning can be reduced, thereby resulting in the effects of improved efficiency and reduced costs.