Viscosity and acoustic behavior of ceramic suspensions optimized for phase-change ink-jet printing

The application of ink-jet printing technologies to direct-write and freeform fabrication of ceramics requires the development of appropriate printing fluids. The critical parameter controlling fluid printing ability is viscosity, although surface tension and density are also important. Additionally, in piezoelectric-driven ink-jets, drop ejection is governed by a series of electric pulses exciting a transducer at acoustic frequencies and hence the fluid acoustic wave speed is also important. Here, suspensions of sterically stabilized fine ceramic powders in solidifying hydro-carbon systems exhibiting suitable rheology for ink-jet printing have been formulated and their acoustic behavior has been characterized. For the particle sizes and frequencies used in this study, acoustic wave speed as a function of solids content is accurately predicted by effective medium theory. Suspensions containing up to 45% particulate by volume can be successfully passed through conventional printing heads.