Victor F. Janas

Fabrication of fine-scale 1-3 Pb(Zrx,Ti1-x)O3/ ceramic/polymer composites using a modified lost mold method

The processing of piezoelectric Pb(Zr,Ti)O3 ceramic fiber/polymer composites via a modified lost mold process is discussed. In the lost mold process, plastic molds, which are negatives of the desired ceramic structure, are created. Each mold is filled with a slurry containing fine Pb(Zr,Ti)O3 powders. After drying, the mold is burned out under controlled atmosphere, and the ceramic is sintered. The sintered ceramic structure is backfilled with polymer, polished, electroded and poled. In the modified lost mold process, several different sacrificial mold were investigated. One type of mold was plastic or wax sheets with precisely punched holes. A second was hollow polyester fibers. The modified mold forming procedure allows rapid prototyping of composites with a variety of connectivities, as well as novel spatial scale and periodicity. Composites with a ceramic fiber as fine as 50 micrometers in 1-3 connectivity have been demonstrated. A variety of rod shapes, including triangles, hexagons, and diamonds have also been demonstrated. Electromechanical characteristics of a number of composites were determined, and will be reported. The modified lost mold process can be used to form fine-scale, large area piezoelectric ceramic/polymer composites for use in hydrophones, transducers for medical ultrasonic imaging and non-destructive evaluation, and as sensors and actuators in vibration and noise control.

Processing of fine-scale piezoelectric ceramic/polymer composites for transducer applications

Abstract In the past decade, piezoelectric ceramic/polymer composites have been used in transducers for a variety of applications. These applications include hydrophones, biomedical imaging, non-destructive testing, and air imaging. Recently, much attention has been give to fine-scale composites. Composites allow higher operating frequencies, and thus increased transducer resolution. In this review, several methods for processing fine-scale piezoelectric ceramic/polymer composites are discussed.

Fabrication and properties of fine scale 1-3 piezocomposites by modified lost mold method

The fabrication of 1-3 piezoelectric PZT/polymer composites using a modified lost mold method is discussed. The modification is in the method of forming the mold. Two new types of sacrificial polymer molds were investigated. In one of the methods, dental wax sheets /spl sim/1.25 mm thick were punched to get the negative of the desired ceramic structure. The wax molds were infiltrated with a slurry containing a high solids loading of PZT particles. Particle size distribution of the PZT powder was controlled to optimize the slurry viscosity and solids loading. After drying, the molds were burned out, and the PZT structures sintered to high density in a controlled lead atmosphere. Various structures with 1-3 rods ranging in size from 50 to 500-/spl mu/m in diameter, and with shapes inducing diamonds, hexagons, triangles, squares, and cylinders were fabricated. In another method, the mold was developed by bundling of hollow polyester fibers (ID=240-/spl mu/m) and filling them with PZT slurry. The sintered rod structures obtained from either type of molds were backfilled with polymer, polished, electroded and poled. The processing of the piezocomposites and their electromechanical properties will be presented.

Development of fine scale piezoelectric ceramic/polymer composites via incorporation of fine PZT fibers

Lead zirconate titanate (PZT) fibers 50 to 70 /spl mu/m in diameter, formed by the Viscous Suspension Spinning Process (VSSP) were sized and incorporated into piezoelectric ceramic/polymer composites. Water soluble polymer solutions containing polyvinyl alcohol, polyethylene glycol, and ethylene glycol were used as sizing agents. The sized fibers formed a multifilament collimated bundle called a tow. The number of individual fibers in a tow varied between 10 and 500. The sized tows were dried at room temperature and cut to desired lengths, heat treated to remove the organic and fired to form straight rods. The rods were bundled and embedded in spurrs epoxy to fabricate 1-3 composites. Green tows were also woven into plain fabric and carpet structures. After firing, the diameter of the individual PZT fibers was 10 to 30 /spl mu/m. The effect of sizing solution chemistry and concentration on tow tightness and flexibility is reported. The microstructure and electromechanical properties of composites with a variety of architectures are also discussed.

Engineering of fine structured 2-2 and 2-0-2 piezoelectric ceramic/polymer composites by tape casting

A novel process of forming piezoelectric composites using tape cast sheets is reported. Composites with 2-2 and 2-0-2 connectivity were formed using sintered tape cast sheets of PZT-5H. The third phase in the form of powder included zirconia, alumina, or hollow and solid glass spheres. Electromechanical properties including d/sub 33/, d/sub h/, K, ringdown time, and k/sub t/ were evaluated. The 2-0-2 composites showed a ringdown time up to 50% faster than 2-2 composites. The d/sub h/ of the 2-0-2 composites were about 20% higher than those of the 2-2 composites at equivalent PZT volume fractions.

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.