A new binder formulation has been developed for Fused Deposition of Ceramics (FDC) which consists of commercially-available polymer constituents.. This formulation was used. in conjunction with lead zirconate titanate (PZT) and hydroxyapatite (HAp) powders. Adsorption studies were performed to test the effectiveness of several carboxylic acids and alcohols on the dispersion of these powders in the binder system. In both cases, it was found that stearic acid was most effective as a dispersant for the ceramic powder / thermoplastic system. After a suitable dispersant was chosen, ceramic powders were compounded with the binder formulation to yield 55 vol.% ceramic-loaded materials. The resultant compound was• used to make filament suitable for use in a modified StratasysTM 3D-Modeler. The filament was well suited for FDC usage, and the parts made using FDC contained no detectable filament-related defects.

The fused deposition of ceramics (FDC) technique was used to fabricate piezoelectric ceramic skeletons for the development of piezoelectric composite transducers with 2-2 connectivity for medical imaging. The green parts were designed to have 30 vol% lead zirconate titanate ceramic (PZT-5H) in the final composites. Physical characterization of the sintered samples revealed that 96% of the theoretical density was achieved. Optical microscopy showed that defects due to the FDC mode of deposition, such as small roads and bubbles, were eliminated, because of improvements in powder processing. The electromechanical properties of the final composites were similar to the properties that were obtained for conventionally made composites. A matching layer and a backing layer, as well as wires and an inductor, were added to each FDC composite to fabricate a functional medical imaging transducer. The devices were tested in water using a steel target 3.5 cm thick. Echoes from the target could be detected with all the transducers that were fabricated using FDC. The sensitivities of the transducers were similar to that of a commercial transducer. However, the ringing was much longer than that for a commercial transducer, because the backing layer was not optimized in the transducers that were fabricated using FDC.

A study of the adsorption of several surfactants onto lead zirconate titanate (PZT) powder was performed. The adsorption of oleyl alcohol, stearyl alcohol, oleic acid, and stearic acid onto PZT-5H powder (surface area = 2.58 m 2 /g) was measured by thermogravimetric analysis. Toluene was used as a solvent, and the solution concentrations were set at 50.0 g/L. It was found that the stearic acid adsorption onto the PZT-5H powder was highest, to the extent of 8.1 mg/m 2 . Trace amounts of stearyl alcohol adsorbed onto PZT, showing an adsorption of 0.8 mg/m 2 . Both oleyl alcohol and oleic acid showed no measurable adsorption. Once stearic acid was found to be a suitable surfactant for fused deposition of ceramics (FDC), the coating process was studied to further optimize the amount adsorbed. A total of six solution concentrations, varying from 5.0 to 70.0 g/L stearic acid in toluene, were tested. It was found that a solution concentration of 30.0 g/L stearic acid was sufficient to provide maximum coverage of the PZT surface. Increases in concentration beyond 30.0 g/L had no effect on the adsorption of the surfactant. PZT powder coated with stearic acid using this method was compounded with a proprietary thermoplastic binder formulation at 55 vol% PZT. Rheology measurements show that this material exhibits a viscosity adequate for FDC.

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