On the Probability of Nucleation at the Surface of Freezing Drops

Turner, Giles W.; Bartell, Lawrence S.

doi:10.1021/jp058098x

Cited by 17 publications

(12 citation statements)

References 22 publications

(37 reference statements)

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“…6 The presence of the surfactant could have induced heterogeneous nucleation at the interface with the surfactant. 7 Koop 8 analyzed data on ice nucleation in water droplets in gaseous environments and concluded that the experimental errors associated with the published data are too large to distinguish between surface-and volume-dependent processes on the basis of measured nucleation rates. Laboratory measurements indicate that homogeneous nucleation of ice from pure water droplets is indeed a volumeproportional process for droplet radii above 19 µm.…”

Section: Introductionmentioning

confidence: 99%

Efflorescence of Ammonium Sulfate and Coated Ammonium Sulfate Particles: Evidence for Surface Nucleation

et al. 2010

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Using optical microscopy, we investigated the efflorescence of ammonium sulfate (AS) in aqueous AS and in aqueous 1:1 and 8:1 (by dry weight) poly(ethylene glycol)-400 (PEG-400)/AS particles deposited on a hydrophobically coated slide. Aqueous PEG-400/AS particles exposed to decreasing relative humidity (RH) exhibit a liquid-liquid phase separation below approximately 90% RH with the PEG-400-rich phase surrounding the aqueous AS inner phase. Pure aqueous AS particles effloresced in the RH range from 36.3% to 43.7%, in agreement with literature data (31-48% RH). In contrast, aqueous 1:1 (by dry weight) PEG-400/AS particles with diameters of the AS phase from 7.2 to 19.2 mum effloresced between 26.8% and 33.9% RH and aqueous 8:1 (by dry weight) PEG-400/AS particles with diameters of the AS phase from 1.8 to 7.3 mum between 24.3% and 29.3% RH. Such low efflorescence relative humidity (ERH) values have never been reached before for AS particles of this size range. We show that these unprecedented low ERHs of AS in PEG-400/AS particles could not possibly be explained by the presence of low amounts of PEG-400 in the aqueous AS phase, by a potential inhibition of water evaporation via anomalously slow diffusion through the PEG coating, or by different time scales between various experimental techniques. High-speed photography of the efflorescence process allowed the development of the AS crystallization fronts within the particles to be monitored with millisecond time resolution. The nucleation sites were inferred from the initial crystal growth sites. Analysis of the probability distribution of initial sites of 31 and 19 efflorescence events for pure AS and 1:1 (by dry weight) PEG-400/AS particles, respectively, showed that the particle volume can be excluded as the preferred nucleation site in the case of pure AS particles. For aqueous 1:1 (by dry weight) PEG-400/AS particles preferential AS nucleation in the PEG phase and at the PEG/AS/substrate contact line can be excluded. On the basis of this probability analysis of efflorescence events together with the AS ERH values of pure aqueous AS and aqueous PEG-400/AS particles aforementioned, we suggest that in pure aqueous AS particles nucleation starts at the surface of the particles and attribute the lower ERH values observed for aqueous PEG-400/AS particles to the suppression of the surface-induced nucleation process. Our results suggest that surface-induced nucleation is likely to also occur during the efflorescence of atmospheric AS aerosol particles, possibly constituting the dominating nucleation pathway.

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Section: Introductionmentioning

confidence: 99%

Efflorescence of Ammonium Sulfate and Coated Ammonium Sulfate Particles: Evidence for Surface Nucleation

et al. 2010

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“…surface vs. volume freezing. 1,6,8,[13][14][15][16][17][18] The discussion has found a broad echo in the atmospheric sciences since the phase behavior of aerosols determines weather processes by affecting the energy balance of the atmosphere. On Earth, water and its ices are the obvious focus of interest, but recent high-profile space missions have found other simple molecules, such as ammonia, methane, or ethane, to play a similar role in the atmospheres of certain planets and moons of our solar system (see ref.…”

Section: Introductionmentioning

confidence: 99%

Vibrational exciton coupling as a probe for phase transitions and shape changes of fluoroform aerosol particles

Sigurbjörnsson

Firanescu

Signorell

2009

Phys. Chem. Chem. Phys.

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Phase transitions and shape changes of aerosol particles play a fundamental role in atmospheric as well as technical processes involving aerosols. For the example of fluoroform particles, we demonstrate how information about both processes can be extracted from time-dependent infrared spectra by comparison with vibrational exciton calculations. We find volume crystallization rate constants for fluoroform particles in the range of J(v) = 10(8)-10(10) cm(-3) s(-1) at a temperature of T = 78 K. Furthermore, our investigation reveals that supercooled fluoroform droplets crystallize to the most stable monoclinic bulk crystal structure. Immediately after crystallization, the particles have a cube-like shape which evolves with increasing time to an elongated shape. The present results provide new data for a better understanding of the Rapid Expansion of Supercritical Solutions when fluoroform is used as a supercritical solvent under expansion conditions which lead to fluoroform aerosol formation.

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“…Recent studies suggest that for systems as widely varying as atomic liquids [8], salts [16], tetrahedral liquids [17], hexaflourides [18], metal alloys [7,10], Nickel-Silicon [19], polymers [20], and water [4,21], homogeneous nucleation prefers the liquid-vapor interface, and therefore its rate scales not as volume but rather as area. The mechanism for surface nucleation remains unclear, and even more troubling, its predominance has been qualified and questioned [5,[22][23][24]. Meanwhile, experiments on the nucleation of ice on small particles in supercooled water have revealed a strong enhancement in nucleation rate for particles at the liquid-water -air interface [6,25], suggesting that whatever physics underlies surface nucleation likely extends to heterogeneous nucleation as well.…”

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confidence: 99%

Nucleation at the Contact Line Observed on Nanotextured Surfaces

et al. 2014

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It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale texture does not.

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On the Probability of Nucleation at the Surface of Freezing Drops

Cited by 17 publications

References 22 publications

Efflorescence of Ammonium Sulfate and Coated Ammonium Sulfate Particles: Evidence for Surface Nucleation

Efflorescence of Ammonium Sulfate and Coated Ammonium Sulfate Particles: Evidence for Surface Nucleation

Vibrational exciton coupling as a probe for phase transitions and shape changes of fluoroform aerosol particles

Nucleation at the Contact Line Observed on Nanotextured Surfaces

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