|Title:|| Method of preparing thin porous sheets of ceramic material|
|Abstract:||A method of forming thin porous sheets of ceramic material for use as electrodes or other components in a molten carbonate fuel cell is disclosed. The method involves spray drying a slurry of fine ceramic particles in liquid carrier to produce generally spherical agglomerates of high porosity and a rough surface texture. The ceramic particles may include the electrode catalyst and the agglomerates can be calcined to improve mechanical strength. After slurrying with suitable volatile material and binder tape casting is used to form sheets that are sufficiently strong for further processing and handling in the assembly of a high temperature fuel cell.|
|Inventor(s):|| Swarr; Thomas E. (South Windsor, CT), Nickols; Richard C. (East Hartford, CT), Krasij; Myron (Avon, CT) |
|Assignee:|| The United States of America as represented by the United States (Washington, DC) |
1. A method of forming a thin porous sheet of ceramic material comprising:
providing a slurry of fine ceramic particles and liquid carrier including binder material;
spray drying the slurry to form generally spherical porous agglomerates having a rough surface texture;
calcining the agglomerates at a sufficient temperature to drive off said binder material and fix the fine ceramic particles in agglomerates of spiky morphology while substantially maintaining the porosity of the particles;
slurrying the calcined agglomerates with binder and volatile material to form a slip for casting as a tape;
spreading a thin layer of the slip onto a smooth substrate and
drying the slip to set the binder and drive off the volatile material to form a porous sheet of ceramic material.
2. The method of claim 1 wherein the ceramic particles in the slurry include at least two different oxides capable of reacting together to form a ceramic oxygenate at the spray drying and the calcining conditions.
3. A method of preparing electrode catalyst material for a molten carbonate fuel cell comprising:
providing a slurry containing a liquid carrier including a binder material and particles of electrode catalyst a major portion of which are within size fraction 0.2 to 2 microns,
spray drying said slurry at about 100.degree.-500.degree. C. at about 0.1 to 1.0 MPa pressure to produce generally spherical, porous agglomerates of about 10-50 microns size with a rough surface texture containing the catalyst particles,
calcining said agglomerates at about 700.degree.-1100.degree. C. for about 1-6 hours to provide porous, spiky agglomerate particles while substantially maintaining the porosity of the particles,
slurrying said calcined agglomerates with binder and volatile liquid to form a slip,
spreading a thin layer of the slip onto a smooth substrate, and
drying said slip to evaporate volatiles and set said binder to form a porous strip of electrode catalysts with interlocking particles for mechanical strength suitable for fabricating into a fuel cell electrode.
4. The method of claim 2 wherein said electrode catalyst material comprises a cathode catalyst, said catalyst selected from the group consisting of oxides of nickel and oxygenates of lanthanium.
5. The method of claim 4 wherein said catalyst material is LaCoO.sub.3.