Near Net-shape Fabrication of Ultrafine Scale Piezoelectric Ceramic/PolymerComposites

摘要

In this program, new net-shape forming technologies were developed for producingfine scale 1-3 and 2-2 piezoelectric ceramic/polymer composites. Piezocomposite materials having extremely fine piezoceramic elements were fabricated using a modified ceramic injection molding process similar to that developed by MSI 1 for coarse scale piezocomposite manufacturing. The principal technical challenges were to make extremely fine PZT ceramic 1-3 and 2-2 preforms without defects or distortion, and use these to and produce piezocomposite samples having sufficient thickness to achieve lateral mode-free response. PZT rods and strips having width dimensions in the order of 25 to 60 micrometers and length-to-width aspect ratios in excess of ten were demonstrated on a research scale. These were used for experimental demonstration of high frequency acoustic imaging arrays for medical ultrasound and Navy mine hunting applications. The new piezocomposite fabrication technology is finding applications ranging from diver-held sonar to low frequency mine detection and classification to advanced net-shape piezoelectric actuators. The program has influenced development of net-shape formed accelerometers for active surface control, as well as coarse receive arrays for submarine use. Under separate SBIR funding (ONR Contract number N00014-95-C-0117), the fine scale molding technology has been scaled up to the point where large (150 x 50 mm) pieces having pitch dimensions below 200 micrometers can be produced every few minutes. Prior to this work, the only net-shape forming approach available for producing piezocomposite was one developed by Siemens 2 which utilized ceramic slip casting into fugitive molds produced by x-ray photolithography.