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Method for producing ceramic cellular structure having high cell density
| Details |
Inventors: Cleveland, Joseph J.;
Assignee: GTE Sylvania Incorporated (Stamford, CT)
Primary Examiner: Lesmes; George F.
Assistant Examiner: Thibodeau; P. J.
Attorney, Agent or Firm: O'Malley; Norman J., Fox; John C., Castle; Donald R.
A ceramic cellular structure having a cell density of up to 1600 cells per square inch and wall thicknesses down to 2 mils is produced by a process which comprises: (1) forming a slurry consisting essentially of finely divided sinterable solid particles of ceramic raw materials and a controlled amount of a plastic supporting matrix containing thermoplastic resin, a thermosetting resin, a plasticizer, an organic solvent and a small amount of a deflocculant; (2) ball milling the slurry; (3) casting the slurry in the form of a film; (4) removing the solvent to produce a self-supporting green ceramic tape; (6) molding a portion of the tape to form a corrugated first member; (7) providing another portion of the tape to form a substantially flat second member; (8) forming a first bilayer by bonding the second member to the nodes of the first member; (9) mutually bonding a predetermined number of bilayers substantially identical to the first bilayer to form a cellular green structure of a desired shape; and (10) firing the green structure at a temperature sufficient to form a sinter-welded polycrystalline ceramic structure. The fired structures, after being subjected to various finishing operations, are useful as rotary heat regenerators, stationary heat recuperators and catalyst supports. |
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DETAILED DESCRIPTION OF THE INVENTION For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above description of some of the aspects of the invention.
Essentially any ceramic or glass raw material particles are useful in the practice of this invention which will sinter or sinter and devitrify to form a ceramic body when heated to conventional firing temperatures.
Solid oxides such as aluminum oxide, rare earth oxides, refractory metal oxides, zirconium oxides and silicon oxides can be used.
Ceramic materials other than oxides such as silicon nitride, silicon carbide, Sialons (a series of compounds resulting from partial substitution of Al for Si and O for N in B--Si.
sub.
3 N.
sub.
4), rare earth metal silicates, and zirconium spinel can be used.
However, in view of the applications envisioned for the final ceramic cellular structures, ceramic materials exhibiting low positive, zero or negative coefficients of thermal expansion in their fired state are preferred for use in the practice of the invention.
Such preferred materials include but are not limited to lithium aluminum silicates, magnesium aluminum silicates, lithium-magnesium aluminum silicates, aluminum silicates, mullite, cordierite, magnesium titanate, aluminum titanate and fused silica.
If desired, various minor amounts (generally one-half percent by weight or less) of various additives such as grain growth inhibitors may be incorporated into the ceramic raw material as is known in the art.
For example, magnesium oxide has long been known as an effective grain growth inhibitor for aluminum oxide.
Some rare earth oxides are also known to be effective grain growth inhibitors for various ceramic materials.
Depending upon beginning particle size and the desired tape cast thickness the raw materials may have to be milled to reduce particle size.
For example, for a tape thickness of 2 mils the particle size should not exceed about 50 microns
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Metal Working 
