Papers by Author: Ryuzo Watanabe

Abstract: This paper introduces the development of two kinds of graded piezoceramic bending actuators. For designing the graded compositional profiles, classical lamination theory (CLT) is used to explore the optimal gradient that generates large electromechanical response. As the first model material, a laminated piezoceramic bimorph actuator was designed and fabricated with a graded compositional distribution of PZT and Pt, and its electric-induced bending characteristics were evaluated and compared with the analytical results by CLT. Furthermore, porosity-graded PZT ceramics were developed, which may be used as the preforms for the infiltration process to fabricate bending actuators with graded ceramic/metal and/or ceramic/polymer interfaces. The fabrication process and property evaluation of homogenously porous and porosity-graded PZT ceramics were introduced.

Abstract: Gas release behavior from aluminum and Al 7075 alloy powders during heating in argon was investigated by in-situ gas chromatography. Water vapor, hydrogen, carbon mono-oxide were detected as individual evolution spectra against heating temperature and time. The mechanisms of water and hydrogen evolutions were studied in detail for the determination of effective degassing condition. The adsorbed water and aluminum hydrate on the particle surfaces were considered to be the sources for the released water. Hydrogen peaks were formed from released gases through the reaction of aluminum and magnesium with adsorbed and hydrated water, and from liberated hydrogen that would have been excessively occluded during atomization. For the alloy powder magnesium was found to lower the hydrogen evolution temperature to enhance overall hydrogen release.

Abstract: Uniformly porous and porosity-graded piezoelectric ceramics were prepared by sintering powder compacts consisting of lead zirconate titanate (PZT) and organic material powders as pore-forming agents (PFA) in air atmosphere. The dielectric, elastic and piezoelectric properties of uniformly porous PZT ceramics were investigated as a function of the porosity volume fraction. The electric-field-induced deflection characteristics of the beam-shaped actuator samples were measured with electric strain gages, and compared with the values calculated from the modified classical laminate theory using the elastic and piezoelectric constants of the non-FGM porous PZT ceramics.