physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mech ...

, explosive boiling or phase explosion is a process in which a superheated

metastable In chemistry and physics, metastability is an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball is onl ...

liquid undergoes an explosive liquid–vapor

phase transition In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic Sta ...

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 and then later advanced by Fucke and Seydel.

Mechanism

Explosive boiling or phase explosion - p-T diagram

Explosive boiling can be best described by a pressure–temperature (''p''–''T'') phase diagram. 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 The Clausius–Clapeyron relation, in chemical thermodynamics, specifies the temperature dependence of pressure, most importantly vapor pressure, at a discontinuous phase transition between two phases of matter of a single constituent. It is nam ...

is still valid. During this time heterogeneous evaporation occurs in the substance, with bubbles nucleating from impurities, surfaces, grain boundaries, etc. Fluctuation of thermodynamic properties near critical point

Fluctuation of thermodynamic properties near critical point

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 The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

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 Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...

, thermodynamic properties like

specific heat In thermodynamics, the specific heat capacity (symbol ) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat ...

and

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

vary rapidly as shown in the figure at right. Density and

entropy Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...

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 In thermodynamics, nucleation is the first step in the formation of either a new Phase (matter), thermodynamic phase or Crystal structure, structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically def ...

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. 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 Laser ablation or photoablation (also called laser blasting) is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser ...

References

{{Reflist Physical chemistry

Mechanism

See also

References