Slurry chemistry control to produce easily redispersible ceramic powder compacts

The slurry-based Three Dimensional Printing (3DP(TM)) process requires the production of an easily redispersible powder bed from a well-dispersed slur ry. Understanding and control of the interparticle potential in the dispers ed state, as well as in the dry consolidated state, are important. The stre ngth of the particle-particle interactions in the dry state determines the redispersion efficiency. One factor that controls the interparticle strengt h is the chemical stability of the ceramic powders in the dispersed state. For unstable powders, a partial dissolution and/or hydration of the powders can occur and eventually impede the redispersion by forming insoluble salt bridges at the necks of the particles. Redispersion of the powder bed can be improved substantially by weakening the strength of the particle-particl e bonds. The formation of strong chemical bonds between particles should be avoided by adjusting the slurry pH to an appropriate range where the powde rs are chemically stable in the slurry. Replacement of the chemical bonds b y soluble physical bonds, using a low-molecular-weight hydrophilic polymer, also reduces the interparticle strength and enhances redispersion.