Abstract
Ultrasonic irradiation generates small bubbles in a liquid; these bubbles are called "cavitation bubbles". Under ambient temperature and pressure conditions, high temperatures and pressures are produced in and around the cavitation bubble, just before cavitation collapse adiabatically. Understanding of cavitation bubble temperature is very important for practical use of sonochemistry, because of chemical and physical effects on decomposition of hazardous substans, formation of nano-particle, etc. But the sonochemical phenomena such as cavitation bubble temperature, pressure and so on are not well understood. In this study, we investigated cavitation temperature through recombination of methyl radicals (・CH3) formed by the sonolysis of aqueous solutions with various alcohols. Ultrasonic irradiation was carried out at several temperatures (10℃〜40℃) in water bath with an ultrasonic generator (Kaijyo 4021, 200kHz, 1.3W/cm^2) under an argon or helium atmosphere. It was found that the concentrations of t-butyl alcohol and 2-propanol affected cavitation bubble temperature. The cavitation temperature increased and reached the maximum temperature and then decreased with increasing the concentration of alcohol. Irradiation time and vapor pressure also affected the cavitation bubble temperature. In addition, in the case of n-alcohol, the cavitation bubble temperature was also related by vapor pressure.
