Colloid stability in ceramic systems

To determine the polymers which will likely destabilize a sj tem, it is necessary to look at the Flory—Hu ins x parameter. If the x parame- 

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. 

Calculate the Hamaker constant for the collision of two 0.5 /u,m spherical AI2O3 particles dispersed in benzene (An(/i = 0) = 5 x 10 J) with an adsorbed layer of poly(methyl methacrylate) = 100,000. Use this Hamaker constant to calculate the van der Waals interaction energy as a function of particle separation. 

Calculate the steric interaction energy between the two spheres given in problem 1. Use Table 10.7 for the value of the relevant Flory-Huggins x parameter. 

For the data given in problem 4, determine if the S3rstem will imdergo a sol-to-gel transition if the fractal aggregates have a fractal dimension of 2.15. Determine the time for gelation of this system. 

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