The invention provides fumed silica comprising aggregates that have an aggregate size and a surface area that satisfy particular formulas relating aggregate size to surface area, as well as aggregates that exhibit particular viscosity, power law exponent index, and/or elastic modulus characteristics when dispersed in liquid media. The invention also provides processes of preparing such fumed silica by combining a silica precursor with a stream of combustible gas, combusting the stream, and producing a stream of combusted gas and fumed silica particles, wherein dopants are introduced, the time/temperature profile, or history, of the stream of combusted gas and fumed silica particles is adjusted to allow for post-quench aggregate growth, and/or additional silica precursor is introduced into the stream of combusted gas.

Fumed silica of controlled aggregate size and processes for manufacturing the same

The invention relates to a method for the production of pyrogenic silica having a specific surface area of 30 to 500 m²/g and an average aggregate particle size of 100 to 500 nm and a relative thickening effect of greater than 2.0 relative to an amount of 2% by weight silica in a silicon oil with optimum dispersion, and a fraction of less than 0.03% by weight relative to the pyrogenic silica and less than 100,000 coarse particles per 1 millimeter relative to a 10% by weight aqueous dispersion of the silica. The pyrogenic silica is produced in a flame in a reactor, wherein the reaction gases in an amount of 100kg/h of at least one or more silicon compounds, fuel gas at 100Nm³/h, and air with more than 20% by volume oxygen at 300Nm³/h are brought to reaction in a flame, wherein the nozzle ejection velocity of the inset gases from the reactor nozzle is between 10 and 200 m/s, and the gas velocity and the temperature at the nozzle and in the reactor is radially homogeneously distributed.

Pyrogenic silica produced in a production facility with high capacity

The present disclosure describes a protective coating for a low index material, and a process for preparing a protected low index material. The protective coating partially penetrates the pores of a low index material, providing a seal protecting the pores, and can strengthen the construction by forming a gradient in properties of the protected low index material. The present disclosure further provides a diffusing low index optical element having a protected low index material and a diffusing layer disposed on the low index material.

Protective coating for low index material

The invention provides a method used for preparing flake-like silicon dioxide powder, and belongs to the technical field of powder particle size and morphology control. According to the method, bauxitic clay ore powder containing SiO2 is taken as a raw material; an activator, a dispersant, and a crystal grain morphology control agent are added into the raw material for uniform mixing; an obtained mixed powder is subjected to calcining in atmosphere containing halogen, and obtained silicon halide is subjected to hydrolysis so as to obtain silicon dioxide and halogen hydride; after calcining, the valve of a sealed reaction container is unsealed, so that high pressure gas in the sealed reaction container is delivered into a gas-solid separator with a larger volumn via expansion so as to realize gas-solid separation of silicon halide with gas phase and obtain the flake-like silicon dioxide powder, wherein the gas-solid separator is provided with a water cooling jacket. Thickness of the flake-like silicon dioxide powder is less than 0.2 m, and average diameter-to-thickness ratio is higher than 50. Reaction temperature of the method is relatively low; the method is simple; energy consumption is low; production cost is low; and the diameter-to-thickness ratio of the flake-like silicon dioxide powder can be adjusted.

Method used for preparing flake-like silicon dioxide powder

A method of producing a powder suitable for additive manufacturing and/or powder metallurgy applications from a precursor particulate material comprising: subjecting the precursor particulate material to at least one high shear milling process, thereby producing a powder product having a reduced average particle size and a selected particle morphology.

Method of producing a powder product

The invention provides a process for the production of fumed silica. The process comprises providing a silicon halide feedstock comprising about 80% to 100% methyltrichlorosilane, combining the silicon halide feedstock with hydrogen gas and oxygen gas to form a reactant mixture, discharging the reactant mixture out of a burner, and combusting the hydrogen gas and the oxygen gas of the reactant mixture so as to hydrolyze the silicon halide feedstock to produce fumed silica. Hydrogen (H2) is present in a mole fraction of about 0.11 or less based on the reactant mixture, and/or the velocity of the reactant mixture upon exiting the burner is about 25 m/s or more.

Process for the production of fumed silica

A method of preparing a dispersion of aggregate metal oxide particles having a pre-selected average aggregate particle diameter comprising pre-selecting a desired percent-reduction in the average aggregate particle diameter of the metal oxide particles, providing a dispersion standard pertaining to a dispersion of the aggregate metal oxide particles, wherein the dispersion standard correlates (i) the solids concentration of the dispersion with (ii) the percent-reduction in the aggregate particle diameter of the aggregate metal oxide particles that occurs when the dispersion is milled in a high-shear mixer, and preparing and milling a dispersion of the aggregate metal oxide particles in a high-shear milling device at a solids concentration that is within 10% of the solids concentration determined by the standard to provide a dispersion of aggregate metal oxide particles having the desired average aggregate particle diameter. Also provided is a method for reducing the average aggregate particle diameter of aggregate metal oxide particles, and a dispersion prepared by the method.

Method of preparing an aggregate metal oxide particle dispersion having a desired aggregate particle diameter

Wässrige Dispersion aus aggregierten Aluminiumoxidpartikeln

The invention relates to an aqueous dispersion of aggregate silica particles having a desired aggregate particle diameter.

Aqueous dispersion of aggregate silica particles

The invention relates to an aqueous dispersion of aggregate alumina particles having a desired aggregate particle diameter.

Joanne Liu

Papers

Process for the production of fumed silica

Method of preparing an aggregate metal oxide particle dispersion having a desired aggregate particle diameter

Wässrige Dispersion aus aggregierten Aluminiumoxidpartikeln

Aqueous dispersion of aggregate silica particles

Aqueous dispersion of aggregate alumina particles