Incipient flocculation molding: a new ceramic forming technique

Incipient Flocculation Molding (IFM) is a new and low-cost net-shape formin g technique for ceramic components. Unlike other ceramic forming processes, the slurry has a very low viscosity, which facilitates molding very intric ate features. IFM utilizes a concentrated, nonaqueous, sterically stabilize d ceramic colloidal suspension that is injected into a nonporous mold at a very low pressure. As the temperature of the suspension is lowered below th e theta-point of the stabilizer-solvent system, it is destabilized, resulti ng in flocculation of the slurry to a solid mass. The flocculation process is both rapid and reversible. IFM operates essentially as a temperature-dep endent deflocculant. IFM is ideal for molding ferroelectric ceramics, parti cularly PZT powders, for manufacturing actuators having complex and intrica te features. This is accomplished by dispersing the powders in a solvent, s tabilized by grafted polyethylene glycol (PEG), and injecting into a mold. The solvent is removed by vacuum evaporation and the dried green body is fi nally sintered at an elevated temperature.