Density green body

Clasen R. Preparation and sintering ofhigh-density green bodies to high-purity silica glass. J. Non-Cryst. SoUds 1987 89 335-344... 

The development of the microstructure is strongly affected by the perfection of the Si green body. Inhomogeneities in density, pore size and distribution are... 

In this chapter, we have described the colloid chemistiy of ceramic powders in suspension. Colloid stability is manipulated by electrostatic and steric means. The ramifications on processing have been discussed with emphasis on single-phase ceramic suspensions with a distribution of particle sizes and composites and their problems of component segregation due to density and particle size and shape. The next chapter will discuss the rheology of Uie ceramic suspensions and the mechanical behavior of dry ceramic powders to prepare the ground for ceramic green body formation. The rheology of ceramic suspensions depends on their colloidal properties. 

These equations show the steady state density achieved for a particular pressure. The relations surest that inhomogeneities in the stress distribution within a die will lead to inhomogeneities in the packing density of the ceramic green body. 

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]. 

With a knowledge of the pressure distribution in problem 6, determine the density distribution in the cylindrical green body. The powder used is MgO with a packing density pressure relationship given in Table 13.1. 

A 10% volume SiC ethanol suspension Dg = 0.3 pm cr = 2) is slip cast with a conical plaster of Paris mold to make a radome for an airplane. The pores in the mold are 50 pm in diameter and the permeability of the mold is negligible compared to that of the powder. Determine the time necessary to slip cast a conical green body with a wall thickness of 1.5 cm. Assume that the ultimate packing density of the SiC powder is 80% theoretical. Data for ethanol density 0.7893 gm/cc viscosity 1.2 cP and yi = 24 dynes/cm. 

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