Emulsion-char method for making fine powder
AssigneeSprague Electric Company
InventorNed E. Cipollini
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Abstract
Water soluble precursors of ceramic compounds are emulsified in an organic fluid that is subsequently heated to remove the free water from the emulsion droplets and further heated in a partial oxygen atmosphere to form a char. The carbon in the char maintains the separation between the dried droplet-derived particles. This char may then be heated in air to oxidize and remove the carbon, to calcine the ceramic, and to controllably produce a fine powder of spherical particles having a narrow size distribution.
Claims20
A powder-making method of the kind including preparing an aqueous solution of precursor compounds of the desired powder product, and forming an emulsion comprised of a suspension of droplets of said aqueous solution in a water-immiscible organic fluid, wherein the improvement comprises:
- heating said emulsion to evaporate and remove free water from said droplets and to evaporate and remove a substantial portion of said organic fluid to produce a dispersion of emulsion-droplet-derived particles in the remainder of said organic fluid;
- heating said dispersion in a reduced-oxygen atmosphere to char said remainder of said organic fluid and to form a carbon-char matrix containing said particles;
- and
- oxidizing and removing the carbon in said carbon char matrix to leave only said particles in the form of a powder.
A method for making a fine powder comprising:
- (a) preparing an aqueous solution of precursor compounds of the desired powder product;
- (b) forming an emulsion comprising a suspension of droplets of said aqueous solution in a water-immiscible organic fluid;
- (c) first heating said emulsion to remove free water from said emulsion droplets to convert said emulsion to a dispersion of dry particles composed of said precursor compounds;
- (d) heating said dispersion in an essentially inert atmosphere to decompose at least a portion of said organic fluid to form a carbon char matrix in which separation of said particles is preserved;
- and,
- (e) oxidizing and removing the carbon in said carbon-char matrix by heating in an oxidizing atmosphere to leave only said particles in the form of a powder.
Dependencies are inferred from the claim text.