Green Body Characterization

With the green body properties for the various sections of the green body, a map of these properties can be made to visualize the zones of the green body where laige variances in the properties in the green hody exist in close proximity to one another. Such maps for the density in uniaxial and isostatically pressed green bodies are shown in Enures 13.35, 13.36, and 13.42 [90]. 

To assess the uniformity of the microstructure in a green body, the variance, is used [91]. 

When the experimental variance, o-fxp( i), is larger than the variance in the property, r fc(xi), it is impossible to determine whether stochastic homogeneity exists in the green body. For this case, only an effective homogeneity can be determined. The experimental variance is established by repeated measurements of the property for a single sample. 

With these methods of characterization, the reasons for problems of warping and cracking at later stages of processing can be established. 

For 10 gms of spherical TI2O powder with a geometric mean size by mass of 1.5 /u.m and a geometric standard deviation of 1.8 in 1 liter of aqueous suspension at pH 6, determine the particle size segregation that occurs if the suspension is allowed to settle under 

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Surface area of a powder increases geometrically with decreasing particle size, so that the volume fraction of the outermost layer of ions on the surface increase significantly, which has a significant effect on properties of the powder. With the development of nanotechnology, it is readily to synthesize powders with nanosized particles (1-100 nm). Therefore, characterization of surface properties becomes more and more important. Specifically for ceramics or transparent ceramics, the consolidation of fine ceramic powders with liquid suspensions to produce more uniform green bodies has been shown to play an important role in the fabrication ceramics, especially when special or complex structures are required. Because the quality of microstructure of the consolidated body is determined by the dispersion behavior of the powder and the interaction between the particles in the suspension, which is closely related to the surface properties of the particles, controlling the physical and chemical properties of particles is a critical to ceramics fabrication. 

The density of the compact as a function of the applied pressure is usually used to characterize the compaction behavior of a ceramic powder, which can be used for process optimization and quality control of the green bodies. If the density is plotted... 

Uematsu K (1996) Immersion microscopy for detailed characterization of defects in ceramic powders and green bodies. Powder Technol 88 291-298... 

In literature, visualization techniques like computed tomography (CT) [18-21] or immersion liquid technique (ILT) [22-25] for the characterization of ceramic granules or green bodies are described. The techniques were used especially for macroscopic pore analysis because of limited resolution of the technical equipment. During the last years, improvements up to a resolutions of 1 pm could be achieved by modem 3D techniques. 

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