T.F. McNulty

Development of a binder formulation for fused deposition of ceramics

A new family of thermoplastic binders has been developed for usage in fused deposition of ceramics (FDC). Mixtures were formulated consisting of a base binder, tackifier, wax, and plasticizer. The resultant formulation was chosen based on mechanical, rheological, and thermal property requirements. A formulation consisting of 100 parts base binder (by weight), along with 20 parts tackifier, 15 parts wax, and five parts plasticizer exhibited an optimized compromise of mechanical, rheological, and thermal properties. This formulation was compounded with 55 vol. per cent lead zirconate titanate (PZT) powder, and extruded into filaments with a diameter of 1.75mm and a length of approximately 50 (+/‐10) cm. The resulting filaments were used to fabricate functional piezoelectric ceramic devices via FDC. The binder development process is described, along with the associated mechanical, rheological, and thermal property data.

Piezoelectric ceramics and composites via rapid prototyping techniques

Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping techniques. Reports on processing in which piezoelectric ceramics and composites with novel and conventional designs were fabricated using rapid prototyping techniques. Fused deposition of ceramics, fused deposition modeling, and Sanders prototyping techniques were used to fabricate lead‐zirconate‐titanate ceramics and ceramic/polymer composites via, first, direct fabrication and, second, indirect fabrication using either lost mold or soft tooling techniques.

Fabrication of curved ceramic/polymer composite transducer for ultrasonic imaging applications by fused deposition of ceramics

Fused Deposition of Ceramics (FDC), developed at Rutgers University, is a Solid Freeform Fabrication (SFF) technique where a three-dimensional green ceramic object is built, layer by layer, starting from a Computer Aided Design (CAD) file of the object. This technique was used to build novel piezoelectric ultrasonic transducers for medical imaging applications. Curved ceramic skeletons for 2-2 composite transducers were built by FDC. The designs curvature can be tailored in the CAD file. Therefore, the final composite requires very little machining. The FDC-built green parts were designed in order to have 30 percent volume fraction of ceramic in the composites. The FDC green samples were subjected to a slow binder burnout cycle at 550/spl deg/C for 4 hours, using a heating rate of 10/spl deg/C per hour, then sintered at 1285/spl deg/C for 1 hour. Two radii of curvature were chosen: 10 cm and 20 cm. The minimum composite thickness was 1.5 mm in both cases. The maximum thickness was 2.26 mm for the first radius of curvature and 1.88 mm for the second. Physical characterization of the samples revealed that 95% of the theoretical density was achieved. The electromechanical properties of the final composites and of FDC bulk samples are reported in this paper.

Development of tube actuators by fused deposition of ceramics

Fused Deposition of Ceramic (FDC) technique has been employed to fabricate piezoelectric tube arrays, based on the lead zirconate titanate system directly from a Computer-Aided Design (CAD) file. Extruded filaments with a diameter of 1.75 mm and 52.5 to 60 vol.% PZT loaded were used as feed material. Single tubes and tube arrays of up to 25 elements with the dimensions of 3 to 8 mm outer diameter, 6 to 20 mm height, and 0.4 to 2.0 mm wall thickness have been made. The green structures were subjected to a binder burnout to remove the organic material and were sintered at 1285/spl deg/C for 1 hour to 94-96% theoretical density. The electromechanical properties were evaluated in terms of axial displacements, resonance behavior and hysteresis. The effective piezoelectric coefficient in the axial direction was measured to be /spl sim/1,800 pm/V. The results demonstrate that the FDC technique can be used for rapid prototyping tube actuators with good electromechanical properties, thereby widening the scope of their application.

Multilayered multifunctional ceramic materials by tape casting

Compatibility studies were performed on several electro-ceramic materials for possible usage in multilayered multifunctional ceramic (MMC) devices. Ceramic tape cast sheets were made using BaTiO/sub 3/, (Ni,Zn)Fe/sub 2/O/sub 4/, and 70% Al/sub 2/O/sub 3/ electrical porcelain powders. These materials were then laminated and co-fired to yield monolithic ceramic blocks. EDS dot maps of the material interfaces show that cross-reactivity between sheets was minimal allowing for their usage in complex 3-D circuitry.

Fabrication of Piezoelectric Ceramic / Polymer Composite Transducers using Fused Deposition of Ceramics

The Fused Deposition of Ceramics (FDC) technique was used to fabricate ceramic skeletons for development of piezoelectric composite transducers for medical imaging. The green parts were designed in order to have 30 vol% of PZT-5H ceramic in the final composites. Physical characterization of the sintered samples revealed that 96% of the theoretical density was achieved. Optical microscopy showed that defects, such as small roads and bubbles were eliminated due to powder processing improvements. The electromechanical properties of the final composites were found to be similar to properties obtained for conventionally made composites.