Ivan A. Cornejo

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.

Dielectric and electromechanical properties of PbNi/sub 1/3/Nb/sub 2/3/O/sub 3/-PbTiO/sub 3/-PbZrO/sub 3/ system: a processing-property study

The processing-property relationship in the system xPbNi/sub 1/3/Nb/sub 2/3/O/sub 3/-(1-x)[yPbTiO/sub 3/-(1-y)PbZrO/sub 3/] (PNN-PT-PZ), with 0.4/spl les/x/spl les/0.6 and 0.6/spl les/y/spl les/0.8, were investigated. Samples were processed by three different routes: direct reaction of the oxide constituents, Columbite precursor process, and the PNN-perovskite mixing route. Calcination and sintering studies were carried out at different temperatures for 1-8 hours under controlled PbO atmospheres. Phase evolution was monitored by powder x-ray diffraction (XRD). Scanning electron microscopy (SEM) was used for microstructural characterization. Maxima in the dielectric and electromechanical properties were obtained for samples with x=0.5 and y=0.7 that were sintered at 1200/spl deg/C. At room temperature, the highest dielectric constant was 6400 with a dissipation factor of 2%. These samples exhibit strong electromechanical coupling, k/sub t/=58 and k/sub p/=77%. The piezoelectric charge coefficient (d/sub 33/) of an optimum composition was found to be 820 pC/N.

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.