Characterization and control of the fiber-matrix interface in ceramic ...

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isostatic pressing (HIP), can be applied to more complex geometries with
comparable results. Hot pressing is ideal for the fabrication of shortfiber
or whisker-reinforced ceramics (such as the Sic-reinforced alumina)
and unidirectional lay-ups, but it is expensive. Its application to
multidimensional continuous-fiber-reinforced composites is also limited;
therefore, other techniques for the fabrication of fiber-reinforced
ceramic composites have been explored.
3.3 Sintering
Alternative powder-processing techniques incorporate a forming step
and a subsequent sintering/firing densification stage. "Greenware"
preforms are fabricated by cold pressing, slip casting, or extruding a
fiber-powder-binder mixture or slurry. The binders are removed by lowtemperature
heat treatments, and the components are consolidated by
firing to high temperatures.
The major disadvantage of these processes
is the large degree of shrinkage that occurs during sintering. The
shrinkage produces cracks and porosity in the composite matrix, resulting
in poor properties.
The high sintering temperatures can also damage the
fiber reinforcement.
3.4 Unconventional Techniques
Most of the aforementioned fabricatLon techniques are more suited to
short fibers or whiskers than to continuous fibers OK filaments. Many
composites processed using the methods described herein have exhibited
iqroved mechanical behavior over monolithic ceramics, but the processes
are not easily adaptable to the manufacture of continuous-fiber
composites. The forming and pressing steps cannot be used for large