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Surface tension

About: Surface tension is a research topic. Over the lifetime, 25410 publications have been published within this topic receiving 695471 citations.


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Journal ArticleDOI
29 Jun 2017-Nature
TL;DR: Observation and theoretical evidence are presented illustrating that, in ambient air, surface tension lowering can prevail over the reduction in the Raoult effect, leading to substantial increases in cloud droplet concentrations, changing the properties of clouds.
Abstract: The spontaneous growth of cloud condensation nuclei (CCN) into cloud droplets under supersaturated water vapour conditions is described by classic Kohler theory. This spontaneous activation of CCN depends on the interplay between the Raoult effect, whereby activation potential increases with decreasing water activity or increasing solute concentration, and the Kelvin effect, whereby activation potential decreases with decreasing droplet size or increases with decreasing surface tension, which is sensitive to surfactants. Surface tension lowering caused by organic surfactants, which diminishes the Kelvin effect, is expected to be negated by a concomitant reduction in the Raoult effect, driven by the displacement of surfactant molecules from the droplet bulk to the droplet–vapour interface. Here we present observational and theoretical evidence illustrating that, in ambient air, surface tension lowering can prevail over the reduction in the Raoult effect, leading to substantial increases in cloud droplet concentrations. We suggest that consideration of liquid–liquid phase separation, leading to complete or partial engulfing of a hygroscopic particle core by a hydrophobic organic-rich phase, can explain the lack of concomitant reduction of the Raoult effect, while maintaining substantial lowering of surface tension, even for partial surface coverage. Apart from the importance of particle size and composition in droplet activation, we show by observation and modelling that incorporation of phase-separation effects into activation thermodynamics can lead to a CCN number concentration that is up to ten times what is predicted by climate models, changing the properties of clouds. An adequate representation of the CCN activation process is essential to the prediction of clouds in climate models, and given the effect of clouds on the Earth’s energy balance, improved prediction of aerosol–cloud–climate interactions is likely to result in improved assessments of future climate change.

217 citations

Journal ArticleDOI
TL;DR: In this article, a diblock copolymer of deuterated styrene and isoprene was chemically modified to incorporate pendant fluorinated side chains (fingers) by forward recoil spectrometry, and surface segregation and interfacial segregation of the modified block copolymers from a polystyrene matrix were observed in as-spun films.
Abstract: A diblock copolymer of deuterated styrene and isoprene (dPS−PI) with a small volume fraction of isoprene was chemically modified to incorporate pendant fluorinated side chains (“fingers”). The composition distribution of the diblock copolymers within a high molecular weight polystyrene (PS) homopolymer was determined by forward recoil spectrometry. Surface segregation and interfacial segregation of the modified block copolymers from a polystyrene matrix are observed in as-spun films. Equilibrium segregation was achieved on annealing at 160 °C for several days. The segregation isotherms at the air−polymer interface are shown to be quantitatively described by a self-consistent mean field theory (SCMF), and these permit us to estimate an effective Flory parameter which describes the attraction of the fluorinated segments to the surface and their repulsion from the bulk. The change in the surface tension as a result of the adsorption of the block copolymers at the air−homopolymer interface was evaluated from ...

217 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured interfacial tension of carbon dioxide-water-alcohol mixtures at temperatures in the range 5-71 C and pressures 0.1-18.6 MPa, using the capillary rise method.
Abstract: High-pressure interfacial- and surface-tension phenomena govern the migration and recovery of oil and gas from hydrocarbon reservoirs. The phenomena are of particular relevance to phase separation and mass transfer in light hydrocarbon fractionation plants and in propane deasphalting in lubricating oil refining. Interfacial tensions of carbon dioxide-water-alcohol mixtures were measured at temperatures in the range 5--71 C and pressures 0.1--18.6 MPa, using the capillary rise method. The alcohols were methanol (0.136 mf), ethanol (to 0.523 mf), and isopropyl alcohol (to 0.226 mf). Interfacial tension (IFT) decreased linearly with both temperature and pressure din the low-pressure range (gaseous CO{sub 2}) but was largely independent of pressure at high pressure (liquid or supercritical CO{sub 2}). There was a zone in the vicinity of the critical pressure of CO{sub 2}-as much as 20 C below and 10 C above the carbon dioxide critical temperature--where IFT became small. This is attributed to the formation of a second CO{sub 2}-rich phase. The isotherms exhibited a crossover pressure near 3 MPa for all systems examined.

217 citations

Journal ArticleDOI
TL;DR: In this paper, the rates of nucleation of liquid aerosols from the gaseous maxtures H2SO4+H2O and HNO3+H 2O at 25°C for various relative humidities (10% to 100%) and various activities of acid vapor were calculated using the Flood-Neumann-Doring-Reiss-Doyle theory of binary homogeneous necleation.
Abstract: The rates of nucleation of liquid aerosols from the gaseous maxtures H2SO4+H2O and HNO3+H2O at 25°C for various relative humidities (10% to 100%) and various activities of acid vapor are calculated using the Flood‐Neumann‐Doring‐Reiss‐Doyle theory of binary homogeneous necleation The activities of acid vapor needed for nucleation are 25 to 300 times smaller for H2SO4+H2O than for HNO3+H2O This is due to the much larger free energy of mixing in the liquid phase for H2SO4+H2O Conversion from activities to actual pressures leads to condentrations of nitric acid which are much too high to be found under normal atmospheric conditions On the other hand, the concentrations of sulfuric acid vapor needed to nucleate droplets in the H2SO4+H2O system are in the range 4(10−5) to 13(10−2) ppm, a concentration which can result from photo‐oxidation of SO2 in the atmosphere Calculations are made of the growth curves for H2SO4+H2O droplets (radius versus composition) at various relative humidities from the critical size radius up to a 1000 A radius, corresponding to nuclei large enough to serve as condensation centers for heterogeneous nucleation A generalized version of the Kelvin equation which includes the composition dependence of the surface tension for a binary mixture is derived and applied in calculating these growth curves Sign errors in the second derivatives of the free energy in Doyle's paper are corrected The limitations of the binary homogeneous nucleation theory at extremely low concentrations of one of the components are discussed and it is shown that this theory becomes inapplicable if the actual vapor pressure of one component is below 10−6 torr

217 citations

Journal ArticleDOI
TL;DR: In this article, the relative influence of dispersed-phase viscosity and interfacial tension on equilibrium drop size and drop size distribution is studied for dilute suspensions by dispersing various silicone oils in water, methanol, and their solutions.
Abstract: The relative influence of dispersed-phase viscosity and interfacial tension on equilibrium drop size and drop size distribution is studied for dilute suspensions by dispersing various silicone oils in water, methanol, and their solutions. Correlations for Sauter mean diameter, D32, are developed in terms of system variables using the mechanistic models of Part I. Drop sizes for low to moderate viscosity dispersed phases are normally distributed in volume and can be correlated by normalization with D32. Trends in the distributions are explained in terms of a parameter representing the relative resistance to breakage.

216 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,074
20222,426
2021804
2020816
2019843
2018828