Microscopic explosive boiling due to rapid heating has found many applications in modern technologies such as thermal ink jet printing, laser cleaning, and laser surgery. It is a nonequilibrium process involving an extremely high liquid superheating. This paper presents an experimental study of such an explosive vaporization process induced by firing a microsecond pulsed laser beam on a thin Pt film deposited on a quartz substrate. The temperature variation of the Pt film is measured by recording the electric resistance of the film during laser heating and subsequent cooling. A high-speed photographic technique is employed to visualize the bubble formation and the explosive evaporation process. Explosive boiling experiments have been carried out in either a pool of acetone liquid or a thin acetone film covering the Pt film. The heating rate achieved ranges from 8.0×106 K/s to 9.0×107 K/s. Violent explosive boiling was observed in the case of a liquid film and the vapor bubbles together with liquid droplets were expelled from the Pt film. While in the case of a liquid pool, only a large cluster of bubbles was formed on the Pt film during laser heating. A close examination of the temperature curves reveals a sudden reduction in the heating rate during laser heating, and an apparent bubble nucleation temperature can be defined. Experimental data show that this apparent bubble nucleation temperature is a strong function of the heating rate. It is close to the equilibrium boiling point at low heating rates while approaches the homogeneous nucleation temperature at high heating rates.

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