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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.