Naozumi Iwasawa

Piezoelectric paints as one approach to smart structural materials with health-monitoring capabilities

Piezoelectric paints have a potential to change a conventional structural material into an intelligent material system with health-monitoring capabilities such as vibration sensing and damage detection. Such paints were prepared using lead zirconate titanate (PZT) ceramic powder as a pigment and epoxy resin as a binder. The obtained paints were coated on aluminum test specimens, and were cured at room temperature or at 150 , thus forming the paint films having different thicknesses of 25-300 . These films were then poled at room temperature, and were evaluated with regard to the sensitivities as vibration and acoustic emission sensors in the frequency ranges of 0-250 Hz and 0-1.0 MHz, respectively. This paper mainly describes the effects of the film thickness and the cure temperature on the poling behavior of the PZT/epoxy paint film. This paper describes also the application of the paint film as a vibration modal sensor integrated into a structural material.

Application of piezoelectric paints to damage detection in structural materials

Piezoelectric paints were prepared using lead zirconate titanate (PZT) ceramic powder as a pigment and epoxy resin as a binder. The obtained paints were coated on aluminum plates and were cured at room temperature, thus forming the paint films having thicknesses of 25 to 300 /tm and a PZT volume fraction of 53%. These films were then poled at room temperature, and were evaluated with regard to the sensitivity as an acoustic emission sensor in the frequency range of 0-1.2 MHz. The paint film sensitivity obtained at a given poling field depends on the film thickness, even after being normalized by dividing by the film thickness. The current-voltage characteristic of the paint film reveals that the film-thickness dependence of the normalized sensitivity is interpreted in terms of the space-charge buildup at the PZT/epoxy interface during the poling process of the paint film.

Thickness dependence of the poling and current–voltage characteristics of paint films made up of lead zirconate titanate ceramic powder and epoxy resin

A specially prepared paint made up of lead zirconate titanate (PZT) ceramic powder and epoxy resin was coated on an aluminum plate and was cured at room temperature, thus forming the paint film of 25–300 μm thickness with a PZT volume fraction of 53%. The paint film was then poled at room temperature, and the poling behavior was determined by measuring the piezoelectric activity as a function of poling field. The poling behavior shows that the piezoelectric activity obtained at a given poling field increases with an increase in the film thickness from 25 to 300 μm. The current–voltage characteristic of the paint film, on the other hand, shows that the increase in the film thickness leads not only to an increase in the magnitude of the current density at a given electric field but also to an increase in the critical electric field at which the transition from the ohmic to space‐charge‐limited conduction takes place. This fact indicates that the amount of the space charge of electrons injected into the pain...

Preparation of Piezoelectric Paints and Application as Vibration Modal Sensors

Piezoelectric paints were prepared using lead zir conate titanate (PZT) ceramic powder as a pigment, and epoxy resin as a binder. The obtained paints were coated on aluminum beams and were dried at room temperature, thus forming films with thicknesses of 35 to 81 μm and PZT volume fractions of 30 to 53% . The films were then poled under electric fields of up to 350 kV/cm at room temperature, and the resulting piezoelectric activity was evaluated from vibration measurements on the aluminum beams. The piezoelectric activity obtained under a given poling field increases with increasing film thickness and with increasing volume fraction of PZT. The piezoelectric activity of the PZT/epoxy paint film has proved to be high enough to determine the natural frequencies and mode shapes of a structural material, thus demonstrating the potential of the paint film as a built-in vibration modal sensor.

Poling characteristics of PZT/epoxy piezoelectric paints

Abstract Piezoelectric paints were prepared using lead zirconate titanate (PZT) ceramic powder as a pigment and epoxy resin as a binder. The PZT/epoxy composition was adjusted to 92/8 or 96/4 by weight in the pigment paste (an intermediary product of the final paint), while in the final paint the composition was adjusted to 88/12 by weight (53/47 by volume) for both pigment pastes. The obtained paint was coated on an aluminum beam, and was cured at room temperature for at least 3 days or at 150°C for 45 min, thus forming the film of 25-175 μm thickness. The film was then poled at room temperature, and the poling behavior was determined from the piezoelectric activity as a function of poling field. The poling behavior of the film depends on the film thickness, the cure temperature, and the PZT/epoxy composition in the pigment paste. A good correlation is found between the piezoelectric activity and the electrical conductivity for all the films studied, thus indicating that the poling behavior of the PZT/ep...

Study on thermal crosslinking reaction of o-naphthoquinone diazides and application to electrodeposition positive photoresist

The thermal reactions of o-naphthoquinone diazide (NQD) compounds as a material for photoresists were studied in comparison with their photochemical reactions. An NQD compound decomposed at around 140°C and further reacted in the presence of an alcohol in the solution to yield an indenecarboxylic ester. The photochemical reaction of the NQD compound with alcohol also provided the same ester in a solution, as expected. In a polymer matrix, the thermal reaction of a multifunctional NQD compound with a copolymer having hydroxyl groups yielded sufficiently crosslinked structures at 140°C in 10 min. On the other hand, when the copolymer matrix containing the NQD compound was exposed to UV, and subsequently to heating (140°C for 10 min), no crosslinked structure was obtained. Consequently, it was confirmed that the heating provides a large difference in solubility between unexposed and exposed areas, quite a useful feature from the viewpoint of efficient development of photoimage. We have applied this finding to an electrodeposition positive photoresist incorporating a post exposure bake (PEB) in resist processing. The PEB afforded a very wide process window in an alkaline developer.