Accession Number : ADA322561

Title :   Development and Control of Porosity in Al2O3/AlPO4 Coatings.

Descriptive Note : Technical rept.,

Corporate Author : MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE

Personal Author(s) : Francis, Larraine F.

PDF Url : ADA322561

Report Date : 24 FEB 1997

Pagination or Media Count : 10

Abstract : This report describes a new method for low temperature preparation of porous ceramic coatings. A reaction between aluminum oxide and phosphoric acid is used to bind particles together and control porosity. Porous ceramic coatings with pore contents ranging from 25 to 50% were prepared at processing temperatures as low at 300 deg C. The porosity in coatings prepared from dispersions containing alumina and phosphoric acid was controlled by the relative amount of acid and hence relative amount of aluminum phosphate reaction product. The addition of aluminum chloride to the dispersion led the formation of fine aluminum hydroxide precipitates which react with phosphoric acid at lower temperatures to form aluminum phosphate; these fine reaction products help to bind the alumina particles together without affecting the pore content. The success of this low temperature phosphate route leads to the possibility of other coating systems which use chemical reactions to promote bonding and control porosity.

Descriptors :   *CERAMIC COATINGS, *POROSITY, LOW TEMPERATURE, CHEMICAL BONDS, ALUMINUM OXIDES, PHOSPHATES, PHOSPHORIC ACIDS, FINE GRAINED MATERIALS, PRECIPITATES.

Subject Categories : Ceramics, Refractories and Glass
      Coatings, Colorants and Finishes

Distribution Statement : APPROVED FOR PUBLIC RELEASE