Explosive boiling
In physical chemistry, explosive boiling or phase explosion is a process in which a superheated metastable liquid undergoes an explosive liquid–vapor phase transition into a stable two-phase state because of a massive homogeneous nucleation of vapor bubbles. This concept was pioneered by M. M. Martynyuk in 1976[1] and then later advanced by Fucke and Seydel.[2]
Mechanism
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Explosive boiling can be best described by a pressure–temperature (p–T) phase diagram.[3] The figure on right shows a typical p–T phase diagram of a substance. The binodal line or the coexistence curve is a thermodynamic state where at that specific temperature and pressure, liquid and vapor can coexist. The spinodal line on right is the boundary of absolute instability of a solution to decomposition into multiple phases. A typical heating process is shown in red.
If the heating process is relatively slow, the liquid has enough time to relax to an equilibrium state, the liquid follows the binodal curve and the Clausius–Clapeyron relation is still valid. During this time heterogeneous evaporation occurs in the substance, with bubbles nucleating from impurities, surfaces, grain boundaries, etc.[4]
On the other hand, if the heating process is fast enough that the substance cannot reach the binodal curve through heterogeneous boiling, the liquid becomes superheated, with its temperature above boiling point at a given pressure. The system then shifts away from the binodal and continues to follow the red curve, thus approaching the spinodal. Near the critical temperature, thermodynamic properties like specific heat and density vary rapidly as shown in the figure at right. Density and entropy undergo the largest fluctuation. During this time, it is possible to have a large density fluctuation in a very small volume. This fluctuation of density results in the nucleation of a bubble. The bubble nucleation process occurs homogeneously everywhere in the substance. The rate of bubble nucleation and vapor sphere growth rate increases exponentially closer to the critical temperature. The increasing nucleation prevents the system from reaching the spinodal. When the bubble radius reaches a critical size, the bubbles continue to expand and eventually explode, resulting in a mixture of gas and droplets. This is the explosive boiling, also termed phase explosion.[4]
Explosive boiling was used by M. M. Martynyuk to calculate the critical temperature of metals. He used electric resistance to heat up metal wire. Explosive boiling was found to occur while using ultrafast femtosecond laser ablation.[citation needed]
See also
[edit]References
[edit]- ^ Martynyuk, M. M. (March 1977). "Phase Explosion of a Metastable Fluid". Combustion, Explosion, and Shock Waves. 13 (2): 178–191. doi:10.1007/BF00754998. eISSN 1573-8345. ISSN 0010-5082. S2CID 98386500.
- ^ Seydel, U.; Fucke, W. (July 1978). "Experimental Determination of Critical Data of Liquid Molybdenum". Journal of Physics F: Metal Physics. 8 (7): L157 – L161. Bibcode:1978JPhF....8L.157S. doi:10.1088/0305-4608/8/7/003. ISSN 0305-4608.
- ^ Bulgakova, N. M.; Bulgakov, A.V. (August 2001). "Pulsed Laser Ablation of Solids: Transition from Normal Vaporization to Phase Explosion". Applied Physics A: Materials Science and Processing. 73 (2): 199–208. Bibcode:2001ApPhA..73..199B. doi:10.1007/s003390000686. eISSN 1432-0630. ISSN 0947-8396. S2CID 98776908.
- ^ a b Christensen, B.; Tillack, M.S. (January 2003). Survey of Mechanisms for Liquid Droplet Ejection from Surfaces Exposed to Rapid Pulsed Heating (PDF) (Report). La Jolla, Cal.: University of California, San Diego. Archived from the original (PDF) on 24 January 2021. Retrieved 5 March 2013.