Metal oxide coated silica shells
AssigneeE. I. Du Pont de Nemours and Company
InventorHoward R. Linton
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Abstract
The present invention discloses a novel high surface area powder composition in which the individual powder particles comprise hollow silica shells, e.g., amorphous hydroxylated silica, coated with finely distributed surface accessible metal oxides. The invention also discloses metallic coatings, which are obtained by converting at least a portion of the oxide coatings into the corresponding metals.
Claims20
A powder composition in which the powder particles comprise a hollow silica shell that has an average diameter in the range of about 0.05 to 15 microns, a shell thickness in the range of from about 5 to 50 nanometers, and surface area of about 25 to 350 m.sup.2 /g, said silica shell having a surface accessible coating comprising at least one metal oxide selected from the group consisting of Fe, Zr, V, Nb, Ta, Cr, Mo, W, Co, Ni, Cu, and Zn, wherein said at least one metal oxide comprises about 10 to 75% by weight of the powder composition.
A process for preparing a powder composition, the process comprising the steps of:
- (a) applying to a slurry comprising finely divided core particles, a coating comprising silica,
- (b) optionally dissolving the core material to form an aqueous slurry comprising hollow shell shells,
- (c) recovering the shells, washing said shells substantially free from soluble residues, and optionally drying,
- (d) preparing an aqueous slurry comprising the silica shells, and depositing at least one finely distributed metal hydroxide upon said shells, by adding to the aqueous slurry at least one water soluble salt of said metal hydroxide, and an alkali metal hydroxide,
- (e) recovering the solids from the slurry thereby obtaining silica shells which are at least partially coated with a metal hydroxide, and;
- (f) heating the recovered shells to convert at least a portion of said metal hydroxide coating to a surface accessible metal oxide, wherein said metal oxide comprises at least one oxide of the metals selected from the group of Fe, Zr, V, Nb, Ta, Cr, Mo, W, Co, Ni, Cu and Zn.
A process for preparing a ultra-violet light absorbing powder, the process comprising the steps of:
- (a) preparing an aqueous slurry comprising hollow silica shells,
- (b) applying a coating of at least one ultra-violet light absorbing material upon at least a portion of said shells, by adding at least one water soluble salt which corresponds to said material, and an alkali hydroxide,
- (c) recovering the solids from the slurry thereby obtaining silica shells which are at least partially coated a hydroxide of said absorbing material, and;
- (d) heating the recovered shell to convert at least a portion of said hydroxide to a surface accessible metal oxide.
Dependencies are inferred from the claim text.