Appeal No. 95-1042
Application 07/964,002
and stripping the tape from the units prior to firing the units
(col. 7, lines 11-41).
Cleveland discloses a method for making ceramic cellular
structures having high cell density per unit area which are
useful as heat exchangers and supports for catalysts (col. 1,
lines 16-21). The portion of the reference relied upon by the
examiner (answer, page 5) is the discussion of the prior art,
wherein Cleveland states (col. 1, lines 44-68):
A major disadvantage of ceramics is the difficulty
inherent in forming them, due in large part to their
low strength in the green, unfired state and to their
brittleness in the fired state. The problem becomes
more acute as surface area and size requirements for
these structures increase, requiring decreased cell
wall thicknesses and increased bulk weight.
One approach to solving such forming problems has
been to cast a ceramic film from a slurry onto a
fugitive support material to form a bilayered tape,
mold the bilayered tape into a corrugated member, form
the tape into the desired structure (for example, by
rolling or stacking with interposing flat members) and
fire to volatilize the support medium and sinter-weld
the structure.
The technique of utilizing a fugitive support
material to provide needed strength during forming
imposes an upper limit on cell density due to the space
occupied by the support layer in the structure prior to
firing. In addition, where the wall thickness is small
compared to the support thickness, substantial contact
of the nodes of the corrugated layer may be prevented
(particularly in a rolled structure) resulting in
formation of few sinter welds during firing and
consequent low mechanical strength of the finished
structure.
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