The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Mihalis Lazaridis - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous Nucleation on rough surfaces: implications to atmospheric aerosols
Atmospheric Research, 2000Co-Authors: Mihalis Lazaridis, Øystein Hov, Kostas EleftheriadisAbstract:Abstract The effect of the surface roughness of solid atmospheric aerosol particles on their Heterogeneous Nucleation capability has been examined using the concept of “self-affine” rough surfaces. The surface roughness has a great influence on the contact angle between the particle surface and the nucleating liquid droplets. Roughness enhances wetting and the rate of Heterogeneous Nucleation from the vapor to the liquid phase. The paper furthermore discusses the considerable influence of the surface roughness on the physico-chemical characteristics of atmospheric insoluble aerosol particles.
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A Statistical Mechanical Model of Heterogeneous Nucleation Including the Effects of Line Tension and Surface Diffusion
Journal of Colloid and Interface Science, 1994Co-Authors: Mihalis LazaridisAbstract:A statistical mechanical model for the Heterogeneous Nucleation process has been constructed in order to give a more solid foundation to the classical model based on continuum thermodynamics. A size correction of the surface tension has been included in the present model, which leads to the evaluation of a microscopic contact angle. The Heterogeneous Nucleation of water on different substrates has been examined. With the introduction of the concepts of negative line tension and surface diffusion into the statistical mechanical model, a smaller value for the critical supersaturation for Heterogeneous Nucleation is expected, in agreement with the experimental results, as compared with the predictions of the classical theory. Moreover, our model gives higher Nucleation rates for small aerosol particles as compared with the predictions of the classical model of Heterogeneous Nucleation.
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A statistical mechanical approach to Heterogeneous Nucleation
The Journal of Chemical Physics, 1993Co-Authors: Mihalis Lazaridis, Ian J. FordAbstract:The aim of the present work is to construct a model of Heterogeneous Nucleation based on a statistical mechanical derivation as an alternative to the classical model based on continuum thermodynamics. The result is similar to the classical approach, but the relation to the underlying microscopic physics is clearer. In our approach, we make use of the capillarity approximation using a cluster potential energy that is independent of the position of the molecules in the cluster. The model has a qualitative agreement with the experimental results of Mahata and Alofs for the Heterogeneous Nucleation of water on different substrates.
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A theoretical description of the Heterogeneous Nucleation in binary systems
Journal of Aerosol Science, 1992Co-Authors: Mihalis Lazaridis, Markku KulmalaAbstract:Abstract The classical theory of heterogenous Nucleation based on Fletcher (1958) has been used until now to describe the Nucleation phenomena. However, the Heterogeneous Nucleation process is complex, and its full description covers many aspects missing from the simplest version of the theory. In the present paper we developed a realistic model for Heterogeneous Nucleation in binary systems which takes into consideration the effects of non-uniform surface, surface diffusion and line tension. Furthermore, we use our model to examine the mechanism of Heterogeneous Nucleation in atmospheric conditions.
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Binary Heterogeneous Nucleation at a non-uniform surface
Journal of Aerosol Science, 1992Co-Authors: Mihalis Lazaridis, Markku Kulmala, Boris GorbunovAbstract:Abstract The model for the Heterogeneous Nucleation on aerosol particles with a non-uniform surface introduced by Gorbunov and Kakutkina has been extended to binary systems, and the results of this model have been compared with the results of the uniform surface model. Binary Heterogeneous Nucleation of water-sulphuric acid and water-nitric acid vapours have been investigated. The uniform surface model is found to underestimate the Nucleation rate with a few orders of magnitude compared to the model for non-uniform surfaces.
Markku Kulmala - One of the best experts on this subject based on the ideXlab platform.
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Investigating the effectiveness of condensation sink based on Heterogeneous Nucleation theory
Journal of Aerosol Science, 2020Co-Authors: Saana Tuovinen, Jenni Kontkanen, Jingkun Jiang, Markku KulmalaAbstract:Abstract New Particle Formation (NPF) is regularly observed to occur in heavily polluted Chinese megacities. However, in these NPF events, the survival probability of small clusters into larger aerosol particles is higher than theoretically predicted. One explanation for this could be that the loss rate of clusters due to scavenging by pre-existing particles, which is described by condensation sink, is lower than expected. In this study, we describe the loss of clusters due to condensation sink by using Heterogeneous Nucleation theory, and investigate if ineffectiveness of Heterogeneous Nucleation can result in a significantly lowered effective condensation sink. We find that in principle it is possible that due to properties of the system there is no Heterogeneous Nucleation, and this can significantly influence the magnitude of effective condensation sink and thus increase the survival probability of clusters.
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The Effect of Seed Particle Charge on Heterogeneous Nucleation
Nucleation and Atmospheric Aerosols, 2007Co-Authors: Paul M. Winkler, Gerhard Steiner, G.p. Reischl, Aron Vrtala, Paul E. Wagner, Markku KulmalaAbstract:Heterogeneous Nucleation of n-propanol vapor was measured using charged and uncharged particles in the diameter range from 1.4 to 4 nm as condensation nuclei. Neutral particles were obtained by neutralization of electrostatically classified particles by means of a bipolar diffusion charger whereas for charged particles the charger was replaced by a corresponding dummy. Depending on the sign of the voltage supplied to the classifier electrode, positively or negatively charged particles were obtained, respectively. Heterogeneous Nucleation measurements were performed using a fast expansion chamber. In this paper we illustrate how the charging state of equally sized particles influences the Nucleation behavior.
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The molecular approach to Heterogeneous Nucleation.
The Journal of chemical physics, 2005Co-Authors: Evgeni Zapadinsky, Antti Lauri, Markku KulmalaAbstract:A molecular approach to Heterogeneous Nucleation has been developed. The expressions for the equilibrium cluster distribution, the reversible work of the cluster formation, and the Nucleation rate have been derived. Two separate statements for the work of formation were formulated. If the equilibrium cluster distribution is normalized on the monomer concentration near the substrate surface, the reversible work of formation is expressed by ΔGhetI=(Fnhet−Fnhom)−(F1het−F1hom)+ΔGhom where Fnhet and Fnhom are the Helmholtz free energies of a cluster interacting with a substrate and a cluster not interacting with the substrate, respectively. If the equilibrium cluster distribution is normalized on the monomer concentration far from the substrate surface, the work of cluster formation is given by ΔGhetII=(Fnhet−Fnhom)+ΔGhom. The former expression corresponds to the approach of the classical Heterogeneous Nucleation theory. The cluster partition function appears to be dependent on the location of a virtual plane,...
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The influence of particle solubility on Heterogeneous Nucleation in binary vapor mixtures
AIP Conference Proceedings, 2000Co-Authors: D. Petersen, Markku Kulmala, Aron Vrtala, Ari Laaksonen, R. Ortner, Paul E. WagnerAbstract:Heterogeneous Nucleation of binary n-propanol - water vapor mixtures on non-soluble or partially soluble 8nm Ag and NaCl particles has been investigated experimentally. At constant temperature the vapor activities have been stepwise increased and the number of particles activated to condensational growth shows a comparatively steep increase until all particles have been activated. Onset activities were obtained for various mixing ratios of the binary vapor mixtures. In contrast to homogeneous Nucleation, for binary Heterogeneous Nucleation only a coNucleation without significant mutual enhancement was observed. Heterogeneous Nucleation calculations based on Fletcher theory using experimentally obtained contact angles have been performed. Satisfactory agreement of the slopes of the Nucleation probability curves was observed. However, considerable deviations between experimental and theoretical onset activities indicate problems of the binary Nucleation theory based on the capillarity approximation. For NaC...
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A theoretical description of the Heterogeneous Nucleation in binary systems
Journal of Aerosol Science, 1992Co-Authors: Mihalis Lazaridis, Markku KulmalaAbstract:Abstract The classical theory of heterogenous Nucleation based on Fletcher (1958) has been used until now to describe the Nucleation phenomena. However, the Heterogeneous Nucleation process is complex, and its full description covers many aspects missing from the simplest version of the theory. In the present paper we developed a realistic model for Heterogeneous Nucleation in binary systems which takes into consideration the effects of non-uniform surface, surface diffusion and line tension. Furthermore, we use our model to examine the mechanism of Heterogeneous Nucleation in atmospheric conditions.
Chong-cheng Huang - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous Nucleation of n-Butanol Vapor on Submicrometer Particles of SiO2 and TiO2.
Journal of colloid and interface science, 1999Co-Authors: Chin-cheng Chen, Chong-cheng Huang, Chun-ju TaoAbstract:Abstract Condensation of a supersaturated vapor of n -butanol on monodisperse submicrometer particles is investigated in a flow cloud chamber (FCC). The size dependence of critical supersaturation in the range of 20 to 90 nm is experimentally determined. Two types of aerosol, SiO 2 and TiO 2 , are tested. The results show that both aerosols induce Heterogeneous Nucleation better than perfectly wetted particles. The experimental critical supersaturation is smaller than that predicted by the Fletcher version of Volmer theory of Heterogeneous Nucleation even with the line tension and surface diffusion taken into account and has a size dependence in qualitative agreement with that theoretically predicted but to a lesser degree. The discrepancy can not be fully accounted for by the effects of line tension and surface diffusion and the existing theory concerning the curvature-dependent physical properties. The law of corresponding states was extended to the Heterogeneous Nucleation, and a simple correlation was observed. We conclude that the macroscopic theory of Heterogeneous Nucleation leads to a prediction of critical supersaturation higher than that experimentally measured.
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Heterogeneous Nucleation of Water Vapor on Submicrometer Particles of SiC, SiO2, and Naphthalene
Journal of Colloid and Interface Science, 1998Co-Authors: Chin-cheng Chen, Ming-sheng Guo, Yi-jer Tsai, Chong-cheng HuangAbstract:Abstract Heterogeneous Nucleation of water vapor on monodisperse submicrometer particles is investigated in a flow cloud chamber. The size dependence of critical supersaturation in the range of 15 to 120 nm is experimentally determined. Three types of aerosol, SiC, SiO2, and naphthalene, are tested. The results show that all three aerosols induce Heterogeneous Nucleation much better than that predicted based on bulk physical properties and, for SiC and SiO2, even better than perfectly wetted particles. The experimental critical supersaturation is smaller than that predicted by the Fletcher version of the Volmer theory of Heterogeneous Nucleation even with the line tension and surface diffusion taken into account and has a size dependence in qualitative agreement with that theoretically predicted but to a lesser degree. The discrepancy cannot be fully accounted for by the effects of line tension and surface diffusion and the existing theory concerning the curvature dependent physical properties. We conclude that the macroscopic theory of Heterogeneous Nucleation leads to significant underestimation of the Nucleation rate and prediction of higher critical supersaturation than that experimentally measured.
Chin-cheng Chen - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous Nucleation of n-Butanol Vapor on Submicrometer Particles of SiO2 and TiO2.
Journal of colloid and interface science, 1999Co-Authors: Chin-cheng Chen, Chong-cheng Huang, Chun-ju TaoAbstract:Abstract Condensation of a supersaturated vapor of n -butanol on monodisperse submicrometer particles is investigated in a flow cloud chamber (FCC). The size dependence of critical supersaturation in the range of 20 to 90 nm is experimentally determined. Two types of aerosol, SiO 2 and TiO 2 , are tested. The results show that both aerosols induce Heterogeneous Nucleation better than perfectly wetted particles. The experimental critical supersaturation is smaller than that predicted by the Fletcher version of Volmer theory of Heterogeneous Nucleation even with the line tension and surface diffusion taken into account and has a size dependence in qualitative agreement with that theoretically predicted but to a lesser degree. The discrepancy can not be fully accounted for by the effects of line tension and surface diffusion and the existing theory concerning the curvature-dependent physical properties. The law of corresponding states was extended to the Heterogeneous Nucleation, and a simple correlation was observed. We conclude that the macroscopic theory of Heterogeneous Nucleation leads to a prediction of critical supersaturation higher than that experimentally measured.
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Heterogeneous Nucleation of Water Vapor on Submicrometer Particles of SiC, SiO2, and Naphthalene
Journal of Colloid and Interface Science, 1998Co-Authors: Chin-cheng Chen, Ming-sheng Guo, Yi-jer Tsai, Chong-cheng HuangAbstract:Abstract Heterogeneous Nucleation of water vapor on monodisperse submicrometer particles is investigated in a flow cloud chamber. The size dependence of critical supersaturation in the range of 15 to 120 nm is experimentally determined. Three types of aerosol, SiC, SiO2, and naphthalene, are tested. The results show that all three aerosols induce Heterogeneous Nucleation much better than that predicted based on bulk physical properties and, for SiC and SiO2, even better than perfectly wetted particles. The experimental critical supersaturation is smaller than that predicted by the Fletcher version of the Volmer theory of Heterogeneous Nucleation even with the line tension and surface diffusion taken into account and has a size dependence in qualitative agreement with that theoretically predicted but to a lesser degree. The discrepancy cannot be fully accounted for by the effects of line tension and surface diffusion and the existing theory concerning the curvature dependent physical properties. We conclude that the macroscopic theory of Heterogeneous Nucleation leads to significant underestimation of the Nucleation rate and prediction of higher critical supersaturation than that experimentally measured.
Sheng Liu - One of the best experts on this subject based on the ideXlab platform.
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Supercooling characteristics of mannitol phase transition system under Heterogeneous Nucleation
Journal of Materials Science, 2020Co-Authors: Jun Ji, Jotham Muthoka Munyalo, Xuelai Zhang, Yinghui Wang, Yue Chen, Sheng LiuAbstract:Supercooling of phase change materials (PCMs) during solidification is a major problem in cold thermal energy storage (CTES), which reduces energy efficiency and aggravates energy waste. This study focuses on the supercooling characteristics of PCMs under Heterogeneous Nucleation, which provides a new idea for researching the influence of different dispersants on the supercooling degree of aqueous solution. The optimal ratios of CNTs water dispersant (TNWDIS) and polymer polyacrylic acid sodium (PAAS) to multi-walled carbon nanotubes (MWCNTs) in mannitol aqueous solution are determined through microstructure and cooling characteristics. How these two surfactants and MWCNTs with different concentrations and particle sizes influence the supercooling degree of nanofluids are investigated. The results indicate that the effect of PAAS is greater than that of TNWDIS. Furthermore, under the action of two dispersants and particle sizes of MWCNTs, the fitting equations of supercooling changing with the concentration of MWCNTs are obtained. In the light of the Heterogeneous Nucleation theory, with the enlargement of the particle size and the diminution of the contact angle affected by the dispersants, the interfacial free energy of Heterogeneous Nucleation of PCMs on the surface of nanoparticles is reduced. The supercooling degree therefore decreases. Specifically, the Nucleation mechanism is deduced and analyzed through the contact angle and Nucleation free energy formula.