Norimichi Kawashima

Stability of Superoxide Ion in Imidazolium Cation-Based Room-Temperature Ionic Liquids

The stability of superoxide ion (O(2)(*-)) generated chemically by dissolving KO(2) in dried dimethyl sulfoxide solutions containing imidazolium cation [e.g., 1-ethyl-3-methylimidazolium (EMI(+)) and 1-n-butyl-2,3-dimethylimidazolium (BMMI(+))] based ionic liquids (ILs) was investigated with UV-visible spectroscopic, NMR, and voltammetric techniques and an ab initio molecular orbital calculation. UV-visible spectroscopic and cyclic voltammetric measurements reveal that the O(2)(*-) species reacts with BMMI(+) and EMI(+) cations of ILs to form hydrogen peroxide. The pseudo first order rate constant for the reaction of BMMI(+) and O(2)(*-) species was found to be about 2.5 x 10(-3) s(-1). With a molecular orbital calculation, the O(2)(*-) species is understood to attack the 2-position (C-2) of the imidazolium ring (i.e., BMMI(+)) to form an ion pair complex in which one oxygen atom is bounded to C-2 and the other to the hydrogen atom of -CH(3) group attached to C-2. Eventually, the ion pair complex of BMMI(+) cation and O(2)(*-) species undergoes a ring opening reaction as evidenced with (1)H NMR measurement.

Development of Miniature Needle-Type Hydrophone with Lead Zirconate Titanate Polycrystalline Film Deposited by Hydrothermal Method

A needle-type miniature hydrophone was developed using hydrothermally deposited lead zirconate titanate (PZT) polycrystalline films on a titanium (Ti) wire with a diameter of 0.3 mm in this study. Two types of hydrophones were fabricated as a trial for this paper. One is a hydrophone with hydrothermally deposited PZT polycrystalline films on the end surface and side surface near the end of the Ti wire. The other one is a hydrophone with hydrothermally deposited PZT polycrystalline films only on the end surface of the Ti wire. We measured the frequency characteristics of the relative receiving sensitivity and directivity of the fabricated hydrophones. The frequency characteristics of the relative receiving sensitivities of the fabricated hydrophone type A or B were measured in the frequency range from 1 to 20 MHz. Our hydrophone with deposited PZT films on the end and side faces of the Ti wire had problems in the directivity of relative receiving sensitivity. The relative sensitivity of the side direction was higher than that of the front direction. The directivity of our hydrophone with hydrothermally deposited PZT films only on the end surface of the Ti wire was improved remarkably.

Fundamental Study on One-Dimensional-Array Medical Ultrasound Probe with Piezoelectric Polycrystalline Film by Hydrothermal Method: Experimental Fabrication of One-Dimensional-Array Ultrasound Probe

We deposited a lead zirconate titanete (PZT) polycrystalline film on a titanium substrate by the hydrothermal method and fabricated a transducer using the PZT film for use as an ultrasound probe. A 10 MHz miniature one-dimensional-array medical ultrasound probe containing the PZT film was developed. After sputtering titanium on the surface of a hydroxyapatite substrate, the titanium film on the substrate was etched by the photolithography to form a one-dimensional titanium film electrode array. We could thus fabricate a miniature one-dimensional-array ultrasound probe by the hydrothermal method. Transmitted ultrasound pulses from a 10 MHz commercial ultrasound probe were received by the newly fabricated one-dimensional-array ultrasound probe. The fabrication process of the probe and the results of experiments on receiving waveforms were reported in this paper.

Development of Small Ultrasonic Probe using Lead Zirconate Titanate Film Deposited by Hydrothermal Method

Miniature ultrasonic probes were developed by hydrothermally depositing lead zirconate titanate (PZT) polycrystalline films on a titanium (Ti) wire. The small ultrasound probes were fabricated using hydrothermally deposited PZT polycrystalline film on the end of a titanium wire with a diameter of 0.6 mm and a length of 50 mm. The performances of the prototype small ultrasound probes were measured. As a result, it was confirmed that the probe has a center frequency of 16 MHz, a fractional bandwidth of 70%, and a distance resolution of better than about 130 µm without using an acoustic matching layer. It was also found that the beam width was 0.55 mm for a distance of 4 mm between the string target and the miniature ultrasound probe.

Needle type miniature hydrophone with PZT poly-crystalline film deposited by hydrothermal method having wide directivity

Recently, we have been studied on the deposition technique of piezoelectric poly-crystalline film by hydrothermal synthesizing method in order to develop the piezoelectric actuators and the ultrasound sensors. Hydrophones with diameter of 0.3 mm were fabricated trially by hydrothermal synthesizing method and estimated their performance. However, it was found that there were some problems on their directivities of receiving sensitivities. Hydrophones with modified structure were fabricated trially for improvement of their directivities of receiving sensitivity and estimated their performances.

Development of water immerse type ultrasound probe with PZT film deposited by hydrothermal method

It is well known that the ultrasound is used in various fields like medical applications, non-destructive inspection and many other manufacturing processes. Piezoelectric transducers are used most frequently to generate ultrasound. In particular, piezoelectric ceramic transducers like PZT are used most frequently. However, for the generation of high frequency ultrasound from 10 to 20 MHz, PZT transducer is difficult to handle because thickness is less than 0.2 mm. Therefore, our purpose of study is to form PZT piezoelectric films with hydrothermal method and to develop ultrasound sensors with resonant frequency of a few MHz to a few hundreds MHz. Ultrasound sensors with resonant frequency of a few MHz which were difficult to be fabricated by conventional hydrothermal method were manufactured and their performance in water was studied and reported. These results show the feasibility of the fabrication of ultrasound sensors of frequency from a few MHz to a few hundreds MHz by hydrothermal method.

P3Q-5 Hydrothermal Polycrystalline PZT Thick Film Transducer for High Intensity Ultrasound Radiation at Over 20 MHz

A high intensity and high frequency ultrasound radiation ultrasonic transducer was fabricated by the hydrothermal deposition technique of lead zirconate titanate polycrystalline thick film. This ultrasonic transducer had a 45 micron meters thick hydrothermal PZT layer on a 50 micron meters thick titanium substrate, and an active area was 5 mm times 5 mm. The piezoelectric constant d33 of this PZT thick film was 44 pm/V and the acoustic impedance was about 8 Mrayl. This prototype ultrasonic transducer radiated a sound pressures of over 100 kPa at over 20 MHz in degassed water using a thickness vibration mode of the PZT film. The radiated sound pressures was measured using a commercial hydrophone that was proofed of the receiving sensitivity at 1 MHz to 60 MHz. The hydrophone was held 40 mm in front of a surface of the prototype transducer. This measuring point was a central ultrasonic beam axis from the prototype transducer. An applied voltage to the prototype ultrasonic transducer was 40 V at ten cycles burst waveform of sine wave when measuring the radiated sound pressure. Additionally, when a driving signal was 20 MHz continuous sine waves, cavitations and an acoustic streaming was generated along a line of the central ultrasonic beam axis. The observation of generated cavitations when the continuous high intensity ultrasonic radiation from the transducer was conducted with the KI oxidation method. The cavitations was measured by measuring the oxidation reaction from the generating of cavitations in a KI solution. A volume of the KI solution for the measurement of cavitations was 50 ml

Development of miniature ultrasonic probe with piezoelectric poly‐crystalline film deposited by hydrothermal method

Recently, a PZT poly‐crystalline film deposited on titanium substrate using the hydrothermal method was studied actively in our laboratory for development of an ultrasonic sensor. These PZT poly‐crystalline films can form PZT poly‐crystalline films easily on substrates of complex shape using hydrothermal method. We reported a needle‐type miniature hydrophone and the ultrasonic transducer with hydrothermally synthesized PZT poly‐crystalline films. Results confirmed that the hydrothermally synthesized PZT poly‐crystalline films showed wideband frequency characteristics in the megahertz band of sensitivities. A miniature ultrasonic probe with wide frequency band characteristics of sensitivities is thought to be producible using hydrothermally synthesized PZT poly‐crystalline films. Miniature ultrasonic probes were fabricated using hydrothermally deposited PZT poly‐crystalline film on the end of 0.6‐mm‐diam titanium wires. Ultrasonic imaging experiments of a target in water were performed using a fabricated u...