Green surface unevenness

Figure 6-19 Green sheet surface unevenness caused by vapor from residual solvent erupting.

The molluscs from New Zealand are known as paua, while their cousins across the Pacific on the American coastline are known as abalone. Both occur in glorious iridescent greens, blues, pinks and purples. The nacreous layer has a surface pattern resembling waves, which is caused by concentiatioiis of organic matrix. In the centre is a more uneven area where the animal was attached to the shell. The... 

Today, the best method of overcoming the problem of uneven densities in a green body is isostatic pressing. In this compaction process, the pressure is applied by a fluid that is pressurized and acts uniformly from all sides on dry particulate solids that are enclosed in a flexible container ( mold ) immersed in the fluid [B.13a]. This results in the most uniform consolidation possible. Of course, there is still a density gradient across the part, the center is always less compacted than the surface, but the gradient is uniform and, typically, does not cause distortion during sintering. 

Camber and waviness are similar in form in that they are variations in flatness over the substrate surface. Referring to Fig. 4.6, camber can be considered an overall warpage of the substrate, while waviness is more periodic in nature. Both of these factors may occur as a result of uneven shrinkage during the organic removal/sintering process or as a result of nonuniform composition. Waviness may also occur as a result of a flat spot in the rollers used to form the green sheets. 

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