Homogeneous Bubble Nucleation Research Articles

Morphological control of electrodeposited iron for fluctuating photovoltaic electrical energy

With the Paris Agreement, the installed capacity of green power, such as photovoltaic (PV) and wind power, is growing rapidly at a rate of more than 10 % per year. The practical application of these green electrical energies is limited by the relative lag in the scale of energy storage systems. In response to the pressure on energy storage systems, we explored the feasibility of supplying DC power directly from a PV plant to an industrial electrolyzer by comparing the electrodeposition behavior of Fe2+ in a sulfuric acid system from stabilized DC and fluctuating PV power sources. We found that the factor that damages the stable operation of an iron electrodeposition system the most is the presence of hydrogen evolution reactions, where the generation of hydrogen bubbles reduces the current efficiency of the electrodeposition system and, in severe cases, destroys the surface morphology of the deposited products, causing devastating damage to the system. On this basis, we designed a simple scheme that uses heterogeneous bubble nucleation instead of homogeneous bubble nucleation for rapid bubble expulsion from the cathode surface. Benefiting from the rapid transfer of bubbles, the current efficiency of the electrodeposited iron system increases by 1.25%–10 % at different current densities, and the maximum roughness decreases by 129–2,396 nm, which considerably improves the stability of the electrodeposited iron system for PV power. This work provides useful experimental support for the transformation of the traditional steel smelting industry, which is characterized by high carbon emission and energy consumption, into an environmentally friendly industry.

Characterization of homogeneous nucleation of superheated liquid droplets by nonlinear analysis

The homogeneous bubble nucleation in superheated liquid droplets can be initiated by energetic particles or radiation. The nonlinearity in the heat transfer introduces chaos in the temperature time series of a boiling system. In the present study, the acoustical pulses from the homogeneous nucleation of superheated liquid droplets by neutrons and gamma-rays have been collected. Nonlinear time series analysis methods like 3D attractor reconstruction and Fast Fourier transformation (FFT) have been performed on the collected pulses. The analysis predicts the possibility of the existence of chaos, and the positive value of the largest Lyapunov exponent confirms it. The nonlinearity in the energy deposition by both the recoil nuclei and electrons from the neutrons and gamma-rays respectively, introduce chaos. A qualitative difference has been observed in the 3D attractor and Rescaled Range (R/S) plots between the neutron and gamma-ray-induced pulses, and the present differences are useful for the identification of these pulses.

The Effects of Viscosity and Capillarity on Nonequilibrium Distribution of Gas Bubbles in Swelling Liquid–Gas Solution

A detailed statistical description of the evolution of supersaturated-by-gas solution at degassing has been presented on the basis of finding the time-dependent distribution in radii of overcritical gas bubbles. The influence of solution viscosity and capillarity via internal pressure in the bubbles on this distribution has been considered until the moment when the gas supersaturation drops due to depletion and stops nucleation of new overcritical gas bubbles. This study is based on our previous results for the nonstationary growth rates of overcritical bubbles depending on gas supersaturation, diffusivity and solubility in solution, solution viscosity, and surface tension on bubble surface. Other important factors are linked with the initial rate of homogeneous gas bubble nucleation and coupling between diffusivity and viscosity in the solution. Here, we numerically studied how all these factors affect the time-dependent distribution function of overcritical bubbles in their radii, maximal and mean bubble radii, and the time-dependent swelling ratio of a supersaturated-by-gas solution in a wide range of solution viscosities.

Study of low-level pool boiling in vapor chamber of wickless micro-heat pipe based on Lattice Boltzmann pseudopotential method—Effects of superheat and wall wettability

The lattice Boltzmann method, a mesoscopic numerical method with a solid kinetic basis, is used to establish a low-level pool boiling model to exhibit the transport phenomena inside an evaporation chamber of a wickless micro heat pipe using DI water as the working fluid. The effects of wall superheat and wall wettability on bubbles’ nucleation, growth, and detachment in the evaporation chamber were compared and analysed. Moreover, the influence of the wall superheat on the thermal performance of the micro heat pipe was specifically examined. It is found that the low-level pool boiling occurs with a wall superheat that is higher than 0.357T c, indicating a high heat flux for heat removal. Interestingly, when the relatively hydrophobic chamber wall is superheated by 0.46T c, there are more nucleation sites, and the complete bubbles cycle containing nucleation, growth, and detachment is longer. In contrast, on a hydrophilic surface under the same and sufficient superheat condition, the number of bubble nucleation sites is less than that on the hydrophobic surface, and the complete cycle of bubbles is shorter. It is worth mentioning that the model has values for predictions of homogeneous nucleation of bubbles and thermal transport on hydrophobic or hydrophilic surfaces.

Analytical solution of surface tension of quark-hadron phase transition

By using the finite temperature field theory, the one-loop effective potential and the dynamics of the quantum chromodynamics deconfinement phase transition in the framework of Friedberg-Lee model are studied at finite temperature and density. Our results show that there is a first-order deconfinement phase transition for the full phase diagram, and the critical temperature is about 119.8 MeV for a zero chemical potential whereas the critical chemical is around 256.4 MeV when the temperature is fixed at <i>T</i> = 50 MeV. Moreover, in the thin-wall approximation, we investigate the dynamics of a strong first-order quark-hadron transition via homogeneous bubble nucleation in the Friedberg-Lee model. Under an appropriate boundary condition, the equation of motion for the <inline-formula><tex-math id="M3">\begin{document}$ \sigma $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20220659_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20220659_M3.png"/></alternatives></inline-formula> field is solved, then the evolutions of the bubble critical configuration with radius <inline-formula><tex-math id="M4">\begin{document}$ r $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20220659_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20220659_M4.png"/></alternatives></inline-formula> at different temperatures and densities are calculated. The surface tension, the typical radius of the critical bubble and the shift in the coarse-grained free energy each as a function of temperature and chemical potential are obtained. In order to gain the reliability and advantages of the thin-wall approximation, our analytical results based on the thin-wall approximation are compared with those obtained by the exact numerical method accordingly. Finally, some consequences and possible applications of our results in the quark meson model and Polyakov quark meson model are also presented in the end of this paper.

Investigation of quantum effect of liquid hydrogen on homogeneous bubble nucleation using a density functional theory and molecular dynamics simulations

In this paper, a quantum effect of hydrogen molecules (uncertainties of each atomic nuclear position and momentum) on the bubble nucleation rate was investigated. The homogeneous bubble nucleation analyses were performed using a density functional theory (DFT) reflecting equations of state (EOSs) constructed to reproduce the thermophysical properties of hydrogen obtained from a classical molecular dynamics (MD) method and a quantum MD method. The results showed that the quantum nature of liquid hydrogen decreases the bubble nucleation rate when compared in the same reduced temperature and reduced superheat ratio condition. Further, it was indicated that the results might be caused by the increase of the energy barrier arising from the difference of the density profile and its position at the critical bubble (in other words, the differences of the critical bubble size and the liquid–vapor interface thickness). Furthermore, the DFT analysis was validated through the evaluation of the bubble nucleation rate using the classical MD method and the quantum MD method made as numerical experiments, and qualitatively the same result was obtained between the DFT and the MD simulations.

Experimental demonstration of continuous bubble nucleation in rhyolite

Bubble nucleation is the first step in magma degassing. The kinetics of bubble nucleation during eruptive magma ascent determines the rate of magma degassing, which in turn, has a significant control on the explosivity of eruptions. Here, we examine if bubble nucleation in rhyolite can be continuous over the inferred timescale of magma travel time from reservoir to the surface in explosive silicic eruptions. We performed homogeneous bubble nucleation experiments using cylinders cored from natural rhyolite. Samples were hydrated at an initial pressure and temperature, then decompressed to a final pressure, and held at that pressure for various amounts of time before being quenched. Within a given suite samples had the same temperature as well as initial and final pressures, but were held for different annealing times. The resulting bubble number density of samples within each suite increases by up to 2 orders of magnitude as annealing time increases, indicating that nucleation continued during annealing. We estimate the nucleation rate and duration from measured bubble number densities and show that nucleation in the majority of samples was still ongoing at the time of quenching. Our findings confirm theoretical predictions that bubble nucleation can be a continuous process during eruptive magma ascent in explosive eruptions.

Lower Closure Point for Nitrogen or Argon Adsorption in Mesoporous Solids: Window-Induced Evaporation or Surface-Induced Cavitation?

Isotherms for nitrogen adsorption at 77 K and argon at 87 K in mesoporous adsorbents exhibit a hysteresis loop with a lower closure point (LCP) at a reduced pressure P/P0 of approximately 0.4. This observation has been attributed to the homogeneous nucleation of vapor bubbles in the condensate within a cavity when it has been stretched beyond its tensile strength limit; on this basis, it is argued that the LCP is a property of the adsorbate fluid. However, our extensive computer simulations of homogeneous cavitation invariably give an LCP of 0.25, rather than 0.4. In our quest for the microscopic origin of the observed LCP, we have explored the possible role of two properties of a solid adsorbent: surface heterogeneity and the nature of the conduits connecting a cavity to the surrounding gas. In the first case, cavitation originates from the birth of nanobubbles formed at weakly adsorbing patches on the pore walls, which we refer to as surface-induced cavitation; in the second case, referred to as window-induced evaporation, the condensate in the cavity evaporates because of the snapping of the adsorbate in the short conduits (or windows) connecting the cavity to the surrounding gas. Our simulations show that the evaporation of the condensate from a cavity occurs at a reduced pressure of around 0.4 only when the holding potential of the patches in the surface-induced model is so weak that an open adsorbent with a similar holding potential would be nonwetting. The hypothesis that weakly adsorbing patches are the reason for loop closure at a relative pressure of 0.4 must therefore be rejected because this condition is unlikely to be found in real adsorbent solids. On the other hand, window-induced evaporation of the condensate from a cavity at 0.4 occurs when the windows are of nanodimensions. We argue that windows of nanodimensions are very probable in adsorbents consisting of agglomerations of microparticles.

Evaporation time and vapor generation limit of a droplet on a hot surface

The characteristic of heat flux was analyzed during the heat conduction regime after a water droplet deposited onto a hot surface at the temperature bringing the minimum evaporation time. A two-dimensional solution for estimating surface heat flux was newly derived, in place of the existing one-dimensional one, when a finite size of the liquid droplet suddenly contacted a high-temperature surface of a semi-infinite thick solid. The estimated surface heat fluxes at the minimum evaporation time point for several materials with different thermal properties were consistent within an uncertainty of 20%, although the corresponding surface temperatures for different materials were much different. In addition, a simple equation was developed to estimate the surface heat flux at the minimum evaporation time point, which was validated for the liquid subcooling of 70-80 K and the water droplet radius of 1.0-1.5 mm. Visual observation revealed that the characteristic of the droplet behavior on the hot surface was much different whether the homogeneous bubble nucleation condition was satisfied or not.

Bubble dynamics in a strong first-order quark-hadron transition * *Supported in part by National Natural Science Foundation of China (NSFC) (11675048)

We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model. The one-loop effective thermodynamic potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials. By taking the temperature and the chemical potential as variables, the evolutions of the surface tension, the typical radius of the critical bubble, and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained, and the limit on the reliability of the thin-wall approximation is also addressed accordingly. Our results are compared to those obtained for a weak first-order quark-hadron phase transition; in particular, the spinodal decomposition is relevant.

In situ transmission electron microscopy with dual ion beam irradiation and implantation

To study the helium effects and their interactions with displacement damage in irradiated materials, an in situ dual-ion beam irradiation capability with transmission electron microscopy was recently established at the IVEM-Tandem Facility at Argonne National Laboratory. Pure nickel was irradiated in situ individually with 1 MeV Kr ions for displacement damage study, 16 keV He ions for helium implantation, and simultaneously with 1 MeV Kr ions and 16 keV He ions at the rate of 1 at.% He/dpa to study the interaction of helium and displacement damage at 500 °C. Helium bubbles were formed and segregated within dislocation loops during the He implantation experiment and no bubbles were observed outside the loops. The loop size increased with increasing helium concentration. In contrast, helium bubbles were formed uniformly in the matrix when nickel was irradiated simultaneously with 1 MeV Kr ions and 16 keV He ions. It is suggested that the uniformly-distributed defect clusters formed under 1 MeV Kr ion irradiation serve as trapping sites of helium atoms resulting in homogeneous nucleation of helium bubbles under the dual-ion beam irradiation in nickel.

Single-bubble dynamics in nanopores: Transition between homogeneous and heterogeneous nucleation

When applying a voltage bias across a thin nanopore, localized Joule heating can lead to single bubble nucleation, offering a unique platform for studying nanoscale bubble behavior, which is still poorly understood. Accordingly, we investigate bubble nucleation and collapse inside solid-state nanopores filled with electrolyte solutions and find that there exists a clear correlation between homo/heterogeneous bubble nucleation and the pore diameter. As the pore diameter is increased from 280 nm to 525 nm, the nucleation regime transitions from predominantly periodic homogeneous nucleation to a non-periodic mixture of homogeneous and heterogeneous nucleation. A transition barrier between the homogeneous and heterogeneous nucleation regimes is defined by considering the relative free-energy costs of cluster formation. A thermodynamic model considering the transition barrier and contact-line pinning on curved surfaces is constructed, which determines the possibility of heterogeneous nucleation. It is shown that the experimental bubble generation behavior is closely captured by our thermodynamic analysis, providing important information for controlling the periodic homogeneous nucleation of bubbles in nanopores.

Explosive Volcanic Eruptions and Spinodal Decomposition: A Different Approach to Deciphering the Tiny Bubble Paradox

AbstractBubbles in magmas drive explosive volcanic eruptions. The spatial distribution of bubble nucleation sites in an ascending, decompressing, and supersaturating magma is one of the primary controls on ash morphologies and volcanic hazards. The mechanism of bubble formation is important because it ultimately determines the spatial distribution of bubbles in the fragmenting magma. The initial nucleation of bubbles in a homogeneous magma is problematical because excessive surface tension pressure in very small, nascent bubbles should drive exsolved volatiles back into the melt. This thermodynamic barrier to bubble viability confounds understanding of homogeneous bubble nucleation, yet very small bubbles form, grow, and ultimately drive explosive volcanic eruptions. We refer to this as “the tiny bubble paradox.” Classical nucleation theory typically explains bubble formation and growth, but we propose that a spectrum of bubble‐forming mechanisms may include both homogeneous nucleation and spinodal decomposition (the spontaneous unmixing of phases by uphill diffusion) as end‐member processes. As spinodal decomposition progresses, regularly sized and regularly spaced quasi‐spherical zones form with increasingly high concentration of dissolved water at the centers. Bubble formation occurs as the concentration of water in the interior of the water‐rich zones approaches 100% and the concentration of melt approaches zero. The presence of a broad, diffuse, concentration gradient of water rather than a narrow water‐melt interface means that there is no surface, per se, for surface tension to arise. This is the crux of the solution of the tiny bubble paradox.

The Kinetic Theory for the Stage of Homogeneous Nucleation of Multicomponent Droplets and Bubbles: New Results

A review of the theoretical data accumulated for the last decade on the diffusion kinetics of the stage of homogeneous nucleation of liquid droplets and gas bubbles in multicomponent systems has been presented. In addition to the previously known results, the review contains new relations and discussions that represent the further development of own studies. Thermodynamic expressions that relate the composition of critical droplets and bubbles occurring at unstable equilibrium with metastable multicomponent systems to the sizes of new-phase particles and degrees of supersaturation in the systems have been discussed. The dynamics of the growth of individual multicomponent supercritical droplets and bubbles at the stage of nucleation has been described at arbitrary values of vapor supersaturation for droplets and gas solubility in solutions for bubbles. The kinetics of the nucleation stage has been considered for ensembles of droplets and bubbles within the framework of the mean-field description of supersaturations and the excluded-volume approach. A relation has been shown between the excluded-volume approach to the description of the nucleation stage and the Kolmogorov crystallization theory.

Shock wave induced cavitation of silicone oils

The cavitation threshold of polydimethylsiloxane (silicone) oils was studied using the planar impact of flyer plates to generate large transient negative pressures within the liquids. The plate-impact experiments used a 64-mm-bore gas-gun to launch thin sabot-supported flyer plates onto liquid capsule targets in which a thin Mylar diaphragm formed a free surface at the back of the sample. The shock wave driven into the target capsule by the flyer impact placed the silicone oil in tension upon reflection from the rear free surface, eventually causing the sample to cavitate. The spall strength, or critical tension which cavitates the liquid, was determined by monitoring the free-surface velocity using a photonic Doppler velocimetry system. This study explored the effect of viscosity and loading strain rate on a system of three silicone oils having vastly different viscosities (4.8×10−2Pas to 2.9×101Pas), but otherwise similar properties. The spall strength was found to remain constant over the ranges of strain rate and viscosities probed in this work. A comparison of the experimental results to models for the cavitation threshold of liquids suggested that homogeneous nucleation of bubbles was the dominant mechanism for tension relief at the onset of cavitation.

Thermal and Electromagnetic Transients in Liquid Metal Surfaces of the FNSF

The Fusion Nuclear Science Facility (FNSF) is an intermediate step in the path to commercial fusion energy that will accommodate the extreme fusion nuclear environment and the complex integration of components and their environment as well as the relevant nuclear science and plasma physics. The transient thermal and electromagnetic loads on plasma-facing components in FNSF have been shown to offer significant design challenges that are difficult to meet with solid walls. Hence, the project team is investigating the feasibility of using liquid walls to ameliorate some of the risk associated with solid wall designs.In this paper, we examine the effects these transient loads will have on a liquid wall. Mass loss is considered using standard evaporation models accounting for transient surface temperatures. The heat transfer is modeled with a one-dimensional transient conduction model that accounts for evaporative losses. No liquid motion is considered. Loss rates of tens of microns per edge-localized mode (ELM) are predicted. Peak heat fluxes are treated parametrically to help address the substantial uncertainty inherent in models for the timing and spatial distribution of the heat deposited during the ELM. Boiling is considered but is found to not be of consequence, as the temperatures required for homogeneous nucleation of bubbles are substantially higher than a conventional boiling point. It should be noted that all evaporation calculations are for evaporation into a vacuum. In the future, we intend to incorporate these evaporation rates into an edge physics code to self-consistently model the net mass flows at the liquid surface in a tokamak.Electromagnetic effects due to ELMs and disruptions are accounted for by assuming a stationary plasma quench. ELMs are addressed assuming a small fluctuation in the plasma current during an event, while disruptions are addressed assuming a full quench of the current. The variation in the plasma current induces currents in the conducting fluid, leading to forces on the liquid (and subsequent motion). A commercial finite element code is used to calculate the induced currents and forces associated with a static liquid divertor. Liquid motion is not considered in this calculation, so no magnetohydrodynamic (MHD) currents are addressed, but a simplified model is presented to estimate the impact of these currents on the liquid motion. Based on these calculations, the acceleration of the liquid is expected to be quite high, and containment of the liquid is likely not possible. The MHD effects appear to be relatively minor.

Predicting Homogeneous Bubble Nucleation in Rhyolite

AbstractBubble nucleation is the critical first step during magma degassing. The resultant number density of bubbles provides a record of nucleation kinetics and underlying eruptive conditions. The rate of bubble nucleation is strongly dependent on the surface free energy associated with nucleus formation, making the use of bubble number density for the interpretation of eruptive conditions contingent upon a sound understanding of surface tension. Based on a suite of nucleation experiments with up to >1016 bubbles per unit volume of melt, and using numerical simulations of bubble nucleation and growth during each experiment, we provide a new formulation for surface tension during homogeneous nucleation of H2O bubbles in rhyolitic melt. It is based on the Tolman correction with a Tolman length of δ = 0.32 nm, which implies an increase in surface tension of bubbles with decreasing nucleus size. Our model results indicate that experiments encompass two distinct nucleation regimes, distinguishable by the ratio of the characteristic diffusion time of water, τdiff, to the decompression time, td. Experiments with >1013 m−3 bubbles are characterized by τdiff/td≪ 1, wherein the nucleation rate predominantly depends on the interplay between decompression and diffusion rates. Nucleation occurs over a short time interval with nucleation rate peaks at high values. For experiments with comparatively low bubble number density the average distance between adjacent bubbles and the diffusion timescale is large. Consequently, τdiff/td≫ 1 and nucleation is nearly unaffected by diffusion and independent of decompression rate, with bubbles nucleating at an approximately constant rate until the sample is quenched.

Unexpected Homogeneous Bubble Nucleation near a Solid–Liquid Interface

We report a quasi-three-dimensional observation of electron-beam-induced nanobubbles inside a 1000 nm thick layer of water using the liquid cell electron microscopy. In the early stage of observation, heterogeneous bubble nucleation occurred, and small bubbles coalesced with the adjacent bubbles when they come in contact with each other. However, for the first time, we found that after prolonged electron beam irradiation heterogeneous nucleation did not occur more, and then homogeneous nucleation started even though a solid surface was available for heterogeneous nucleation. We conclude that the Ostwald ripening effect prevents heterogeneous nucleation from occurring and that the lower surface tension due to the generation of ions and radicals boosts the homogeneous nucleation. It was also discovered that the generation sites of homogeneous nucleation are beneath the three-phase contact lines of existing interfacial bubbles.

Homogeneous nucleation of nano size H2O bubbles and their growth to micro size in rhyolite melts

Volcanism accompanies transfer of volatiles such as H2O and CO2 from the Earth interior to the atmosphere. The underlying process for transfer of the volatiles is magma degassing. As magma rises toward the Earth surface, the volatiles in silicate melts become supersaturated due to decompression of magma so that nucleation of volatile-bearing bubbles and subsequent growth of the bubble occur. In this study, bubble nucleation rate of water in rhyolite melts above 1000 K, which determines the style of the eruption of the magma, is calculated by using molecular cluster model. Calculation results indicate that the homogeneous nucleation of water in the rhyolite melts is possible when the supersaturation pressure exceeds 110 MPa and the number density of bubbles formed increases as increase in the degree of the supesaturation. Growth of bubble formed from the critical cluster was also calculated and the results were compared with observed bubble sizes. When the bubble number density is greater than 1015/m3, depletion of the concentration of volatiles hinders further growth of bubbles.

Study of homogeneous bubble nucleation in liquid carbon dioxide by a hybrid approach combining molecular dynamics simulation and density gradient theory.

A new method for predicting homogeneous bubble nucleation rates of pure compounds from vapor-liquid equilibrium (VLE) data is presented. It combines molecular dynamics simulation on the one side with density gradient theory using an equation of state (EOS) on the other. The new method is applied here to predict bubble nucleation rates in metastable liquid carbon dioxide (CO2). The molecular model of CO2 is taken from previous work of our group. PC-SAFT is used as an EOS. The consistency between the molecular model and the EOS is achieved by adjusting the PC-SAFT parameters to VLE data obtained from the molecular model. The influence parameter of density gradient theory is fitted to the surface tension of the molecular model. Massively parallel molecular dynamics simulations are performed close to the spinodal to compute bubble nucleation rates. From these simulations, the kinetic prefactor of the hybrid nucleation theory is estimated, whereas the nucleation barrier is calculated from density gradient theory. This enables the extrapolation of molecular simulation data to the whole metastable range including technically relevant densities. The results are tested against available experimental data and found to be in good agreement. The new method does not suffer from typical deficiencies of classical nucleation theory concerning the thermodynamic barrier at the spinodal and the bubble size dependence of surface tension, which is typically neglected in classical nucleation theory. In addition, the density in the center of critical bubbles and their surface tension is determined as a function of their radius. The usual linear Tolman correction to the capillarity approximation is found to be invalid.