Takeyoshi Uchida

Cavitation sensor with hydrothermally synthesized lead zirconate titanate polycrystalline film deposited on cylindrical titanium pipe: Estimation of acoustic cavitation field and basic characteristics of cavitation sensor

We have developed a small cavitation sensor by deposition of hydrothermally synthesized lead zirconate titanate polycrystalline film onto the outer surface of a hollow cylindrical titanium pipe. The spatial distribution of acoustic cavitation generated in the vessel of a 150 kHz sonoreactor was measured by using the broadband integrated voltage (BIV) calculated from the output signal of the cavitation sensor. A spatial distribution similar to the sonochemical luminescence pattern could be observed in the measured BIV results. We found that our fabricated cavitation sensor could measure the spatial distribution of acoustic cavitation in a high-intensity ultrasound field for a period exceeding 150 h without damage. We also measured the spatial distribution and directivity of the receiving sensitivity for characterization of the sensor. The measured results suggest that the BIV and cavitation signal included in the output signal of the cavitation sensor are a consequence of the acoustic cavitation generated ...

Surface modification of diamond powders by sonochemical reaction

Diamond powders are used for polishing electronics devices such as hard disk substrates. The surface profile of the polished texture affects the final properties of hard disk and so polishing materials and polishing process are very important. Polishing materials have to be dispersed homogeneously without aggregation. Many dispersants are then developed to improve the dispersion property of polishing materials, whereas improvement of the surface properties of polishing materials using dispersant is not essential. In this study, an attempt was made to modify the surface of diamond powders using acoustic cavitation generated by irradiation of strong ultrasonic wave on aqueous diamond slurry. As a result, the diamond particle surface was verified to be modified by the oxidizing action of active oxygen species formed by acoustic cavitation.

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

Study on dispersion and surface modification of diamond powders by ultrasound exposure

When diamond particles are used as abrasive agents, diamond particles have to disperse homogeneously. Consequently, many dispersants are developed to improve the dispersion property of abrasive agents, whereas improvement of surface properties of abrasive agents using dispersant is not essential. We attempted intrinsic surface modification of diamond particles used as abrasive agents by ultrasound exposure. The change of zeta potential by ultrasound exposure was confirmed. Sub-micro diamond particles with average size smaller than 0.3 /spl mu/m were obtained.

Development of tough anti cavitation hydrophone by deposition of hydrothermally synthesized lead zirconate titanate poly-crystalline film on reverse surface of titanium front layer

It is difficult to measure the high intensity ultrasound field with generation of acoustic cavitaion, since the electrode of hydrophone will be damaged by erosion and acoustic cavitation. Therefore, we developed the original miniature hydrophone by using hydrothermally synthesized lead zirconate titanate poly-crystalline film deposited on a reverse surface of a titanium film front layer as protection layer from damage by acoustic cavitation and erosion. Our hydrophone could be used to measure the high intensity ultrasound field with generation of acoustic cavitation such as focal area of 1.6 MHz HIFU treatment equipment and in a vessel of a 47 kHz ultrasound cleaner without any damage. However, we observed the output waveform of the hydrophone without nonlinear distortion in spite of measurement in high intensity ultrasound field like focal area of 1.6 MHz HIFU treatment equipment. We considered on the cause of above problem and its improving methods by computer simulation with MASONs equivalent circuit ...

P2L-3 Effects of Sound Field and Acoustic Streaming on Nanometer Sized Diamond Particles Dispersion System using Ultrasound

We reported the improvement of dispersion of nanometer sized diamond particles using shock wave and active oxygen species by acoustic cavitation at 155 kHz in 2004 IEEE International UFFC Joint 50th Anniversary Conference in Montreal. Average sound pressure calculated from sound pressure distribution in horizontal plane at distance of 10 mm from a stainless steel vibrating disk in water tank was used as acoustic index for improvement of dispersion of the diamond particles. The measured horizontal plane was on the loop of the standing wave acoustic field. However, improvement of dispersion characteristics of the particles was performed in whole water in the water tank. Therefore, each sound pressure distribution in horizontal plane at the distances of 10 mm to 95 mm from the stainless steel vibrating disk was measured by hydrophone. Sound pressure distribution all over water in the water tank was observed three dimensionally. The generation of active oxygen species in the water tank was estimated by observation of sonochemical luminescence. As the results, higher sound pressure than 100 kPa was measured in central region lower than height of 55 mm from the stainless steel vibrating disk in the water tank. Sonochemical luminescence could not be observed in above region in the water tank. They were contradictory results. We guess that the acoustic streaming prevents from trapping cavitation bubble at the loop of standing wave sound field. We think that the acoustic streaming is one cause of the contradictory results. Homogenous sound pressure distribution is required improvement of dispersion characteristics of nanometer sized diamond particles by ultrasound exposure

Development of wide frequency range ultrasound exposure system for dispersion of nano diamond particles

A novel acoustic dispersion method for fine diamond particles was proposed. We developed the ultrasound exposure system using PZT piezoelectric ceramic vibrator and acoustic matching layer which is expected to operate in wide frequency range and with high efficiency in this time. Since the conventional ultrasound exposure system was the narrow frequency band system (fractional bandwidth of 9%) using the Langevin-type transducer, we are apprehensive that the performance of the system became unstable by changing resonant frequency of the transducer due to temperature elevation for long time operation. The bottom plate of the water tank for irradiation of ultrasound into diamond particle suspension is used as the acoustic matching layer. PZT piezoelectric ceramic vibrator with resonant frequency of 300 kHz was equipped on the bottom plate. It was found by measurement of sonochemical luminescence and KI oxidation method that active oxygen species like hydroxyl radical and hydrogen peroxide generated by the new ultrasound exposure system was increased twice the amount of those generated by the conventional system. Furthermore, it was proved by measurement of the frequency characteristics of sonochemical luminescence that the new system could generate the active oxygen stably in wider frequency range (fractional bandwidth of 39%) than the conventional system. Zeta potential of sonicated nano diamond particles was increased.