Method of forming sodium beta-Al.sub.2 O.sub.3 films and coatings
AssigneeWestinghouse Electric Corp.
InventorsDeborah M. Paruso, Bulent E. Yoldas
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Abstract
A sodium Beta-alumina thin film is coated onto a supporting substrate by forming an agglomerate-free, hydrolyzed sol, principally comprising an electrically surface active polymer formed by the hydrolysis and peptization of sodium and aluminum alkoxides, which is applied to the substrate. The substrate and applied sol are then heated to crystallize the polymer and form a solid film having pores with radii of up to about 250 Angstrom units.
Claims13
A method of making a highly ion-conductive, supported sodium-Beta alumina thin electrolyte film, which comprises the steps of:
- (A) forming a fluid, sodium Beta-alumina precursor sol having an Al concentration equivalent to between about 0.5 and about 2.5 weight percent Al.sub.2 O.sub.3, by the steps comprising, first reacting Na(OR) and Al(OR).sub.3 alkoxide compounds, where R is an alkyl group containing from 1 to 6 carbon atoms, and then peptizing and completely hydrolyzing the reactants;
- in a manner such that a Na compound is reacted with an Al compound to form a chemical bond between Na and Al through oxygen to form a slurry of non-crystalline, electrically surface active polymers containing Na, Al, OR, and OH groups before complete hydrolysis, and where a peptizing acid is added to the reactants and adsorbed on the polymer surface at some point in sol formation after alkoxide reaction to provide a non-crystalline, homogeneous, agglomerate-free, fluid sol;
- (B) applying the fluid, non-crystalline precursor sol as a film to a substrate;
- and finally
- (C) heating the precursor film at between 1200.degree. C. and about 1450.degree. C., to cause a phase change and formation of a uniform, low porosity, solid material comprising crystalline sodium Beta-alumina in film form firmly bonded to the substrate, where the solid film has pores with radii of up to about 250 Angstrom units, and where, in step (A) the Na compound and the Al compound are added in an amount effective to provide a mole ratio of Na:Al of from 1:5 to 11 in the final crystalline film formed after heating in step (C).
A method of making a highly ion-conductive, supported sodium-Beta alumina thin electrolyte film, which comprises the steps of:
- (A) forming a fluid, sodium Beta-alumina precursor sol having an Al concentration equivalent to between about 0.5 and about 2.5 weight percent Al.sub.2 O.sub.3, by controlled hydrolyzing and acid peptizing Na(OR) and Al(OR).sub.3 alkoxide compounds, where R is an alkyl group containing from 1 to 6 carbon atoms, by:
- (1) first partially hydrolyzing one of the alkoxide compounds with water, and then
- (2) reacting the first partially hydrolyzed alkoxide with an effective amount of the other alkoxide compound so that a Na compound is reacted with an Al compound to form a chemical bond between Na and Al through oxygen to form a slurry of non-crystalline, electrically surface active polymers containing Na, Al, OR, and OH groups, and then
- (3) completely hydrolyzing the polymer with a water-alcohol solution and peptizing it with an acid electrolyte where the peptizing acid is adsorbed on the polymer surface to provide a non-crystalline, homogeneous, agglomerate-free, fluid sol,
- (B) applying the fluid, non-crystalline precursor sol as a film to a refractory ceramic substrate, and finally
- (C) heating the precursor film at between 1200.degree. C. and about 1450.degree. C., to cause a phase change and formation of a uniform, low porosity, solid material comprising crystalline sodium Beta-alumina in film form firmly bonded to the substrate, where the solid film has pores with radii up to about 250 Angstrom units, and where, in step (A) the Na compound and the Al compound are added in an amount effective to provide a mole ratio of Na:Al of from 1:5 to 11 in the final crystalline film formed after heating in step (C).
Dependencies are inferred from the claim text.