The quasi-liquid layer of ice revisited: the role of temperature gradients and tip chemistry in AFM studies

Constantin, Julián Gelman; Gianetti, Melisa Mariel; Longinotti, M. Paula; Corti, Horacio R.

doi:10.5194/acp-18-14965-2018

Cited by 33 publications

(36 citation statements)

References 39 publications

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“…The interfacial tension between ice and vapour is not well known. Following previous studies, we assume a quasi-liquid layer to form on the ice surface (Gelman Constantin et al, 2018;Wettlaufer, 1999). Then an upper limit of the interfacial tension of ice and water vapour is given by the sum of the interfacial tensions of water and vapour and ice and water: γvi(T) = γvw(T) + γiw(T), following David et al (2019).…”

mentioning

confidence: 99%

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Marcolli¹,

Mahrt²,

Kärcher³

2020

Preprint

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Abstract. How ice crystals form in the troposphere strongly affects cirrus cloud properties. Atmospheric ice formation is often initiated by aerosol particles that act as ice nucleating particles. The aerosol-cloud interactions of soot and associated feedbacks remain uncertain, in part because a coherent understanding of the ice nucleation mechanism and activity of soot has not yet emerged. Here, we provide a new framework that predicts ice formation on soot particles via pore condensation and freezing (PCF) that, unlike previous approaches, considers soot particle properties capturing their vastly different pore properties compared to other aerosol species such as mineral dust. During PCF, water is taken up below water saturation into pores on soot aggregates by capillary condensation. At cirrus temperatures, pore water can freeze homogeneously and subsequently grow into a macroscopic ice crystal. In the soot-PCF framework presented here, the relative humidity conditions required for these steps are derived for different pore types as a function of temperature. The pore types considered here evolve from idealized stacking of equally sized primary particles, either in tetrahedral or cubic packing arrangements. Specifically, we encompass n-membered ring pores that form between n individual spheres within the same layer of primary particles as well as pores in the form of inner cavities that form between two layers of primary particles. We treat soot primary particles as perfect spheres and use the contact angle between soot and water (θsw), the primary particle diameter (Dpp) and the degree of primary particle overlap (overlap coefficient, Cov) to characterize soot pore properties. We find that n-membered ring pores are the dominant pore structures for soot-PCF, as they are common features of soot aggregates and have a suitable geometry for both, filling with water and growing ice below water saturation. We focus our analysis on three-membered and four-membered ring pores as they are of the right size for PCF assuming primary particle sizes typical for atmospheric soot particles. For these pore types, we derive equations that describe the conditions for all three steps of soot-PCF, namely capillary condensation, ice nucleation, and ice growth. Since at typical cirrus conditions homogeneous ice nucleation can be considered immediate as soon as the water volume within the pore is large enough to host a critical ice embryo, soot-PCF becomes either limited by capillary condensation or ice crystal growth. For instance, our results show that at typical cirrus temperatures of T = 220 K, three-membered ring pores formed between primary particles with θsw = 60°, Dpp = 20 nm, and Cov = 0.05 are ice growth limited, as the ice requires a relative humidity with respect to ice of RHi = 137 % to grow out of the pore, while a sufficient volume of pore water for ice nucleation has condensed already at RHi = 86 %. Conversely, four-membered ring pores with the same primary particle size and an overlap coefficient of Cov = 0.1 are capillary condensation limited as they require RHi = 129 % to gather enough water for ice nucleation, compared with only 124 % RHi, required for ice growth. We use the soot-PCF framework to derive a new equation to parameterize of ice formation on soot particles via PCF. This equation is based on soot properties that are routinely measured, including the primary particle size and overlap, and the fractal dimension. These properties, along with the number of primary particles making up an aggregate and the contact angle between water and soot, constrain the parameterization. Applying the new parameterization to previously reported laboratory data of ice formation on soot particles provides direct evidence that ice nucleation on soot aggregates takes place via PCF. We conclude that this new framework clarifies the ice formation mechanism on soot particles at cirrus conditions and provides a new perspective to represent ice formation on soot in climate models.

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mentioning

confidence: 99%

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Marcolli¹,

Mahrt²,

Kärcher³

2020

Preprint

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“…The humidity uncertainty is quite large, as expected, considering that we are measuring very low vapor pressures at the analyzed temperature range. However, some results obtained in a previous study 17 showed that during ice deposition at constant temperature, RH attained a constant value of (102.5 ± 4.4)%, indicating that probably the uncertainty in the RH is overestimated. Table II summarizes the sample temperature, supercooling, and temperature and RH of the humid nitrogen above the sample for the experiments performed.…”

Section: Resultsmentioning

confidence: 85%

“…AFM force curves over ice are usually used to study the thickness of the quasi-liquid layer (QLL) that exists over a supercooled ice surface and whose properties differ from those of the bulk supercooled liquid at the same temperature. [13][14][15][16][17] When the tip is away from the ice surface, the force between the tip and the sample is zero. At a certain point, close to the surface, the tip experiences an attractive force, jumping into the ice.…”

Section: Articlementioning

confidence: 99%

“…Measurements were performed with an AFM tip (a Pt/Ir-coated tip) provided by Nanosensors, whose characteristics are summarized in Table I. The characteristics of the tip (shape and chemistry) may affect the QLL thickness determinations, 17,19 but none of these factors would significantly affect the ice thickness measurements used to determine the ice The raw voltage vs piezoelectric displacement (z piezo ) data are transformed into force plots (force vs indentation depth, z tip ). Quantitative analysis of force curves requires several calibrations, which are detailed in a previous study 17 and summarized in Sec.…”

Section: B Force Curve Measurementsmentioning

confidence: 99%

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Environmental chamber with controlled temperature and relative humidity for ice crystallization kinetic measurements by atomic force microscopy

Gianetti

Constantin

Corti

et al. 2020

Review of Scientific Instruments

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The present work describes the development of an environmental chamber (EC), with temperature and humidity control, for measuring ice growth kinetics over a substrate with an atomic force microscope (AFM). The main component of the EC is an AFM fluid glass cell. The relative humidity (RH) inside the EC is set by the flow of a controlled ratio of dry and humid nitrogen gases. The sample temperature is fixed with an AFM commercial accessory, while the temperature of the nitrogen gas inside the EC is controlled by circulating cold nitrogen vapor through a copper cooler, specially designed for this purpose. With this setup, we could study the growth rate of ice crystallization over a mica substrate by measuring the force exerted between the tip and the sample when they approach each other as a function of time. This experimental development represents a significant improvement with respect to previous experimental determinations of ice growth rates, where RH and temperature of the air above the sample were determined far away from the ice crystallization regions, in opposition to the present work.

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“…One of the plausible causes for the considerable variations of the uptake amounts is the presence/absence of thin liquid water layers, so called quasi-liquid layers (QLLs), on ice crystal surfaces at temperatures below the melting point [8][9][10][11]. In the case of nitric acid (HNO 3 ) gas, heterogeneous…”

Section: Introductionmentioning

confidence: 99%

Appearance and Disappearance of Quasi-Liquid Layers on Ice Crystals in the Presence of Nitric Acid Gas

et al. 2020

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The surfaces of ice crystals near the melting point are covered with thin liquid water layers, called quasi-liquid layers (QLLs), which play crucial roles in various chemical reactions in nature. So far, there have been many spectroscopic studies of such chemical reactions on ice surfaces, however, revealing the effects of atmospheric gases on ice surfaces remains an experimental challenge. In this study, we chose HNO3 as a model atmospheric gas, and directly observed the ice basal faces by advanced optical microscopy under partial pressure of HNO3 (~10−4 Pa), relevant to those found in the atmosphere. We found that droplets (HNO3-QLLs) appeared on ice surfaces at temperatures ranging from −0.9 to −0.2 °C with an increase in temperature, and that they disappeared at temperatures ranging from −0.6 to −1.3 °C with decreasing temperature. We also found that the size of the HNO3-QLLs decreased immediately after we started reducing the temperature. From the changes in size and the liquid–solid phase diagram of the HNO3-H2O binary system, we concluded that the HNO3-QLLs did not consist of pure water, but rather aqueous HNO3 solutions, and that the temperature and HNO3 concentration of the HNO3-QLLs also coincided with those along a liquidus line.

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The quasi-liquid layer of ice revisited: the role of temperature gradients and tip chemistry in AFM studies

Cited by 33 publications

References 39 publications

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Soot-PCF: Pore condensation and freezing framework for soot aggregates

Environmental chamber with controlled temperature and relative humidity for ice crystallization kinetic measurements by atomic force microscopy

Appearance and Disappearance of Quasi-Liquid Layers on Ice Crystals in the Presence of Nitric Acid Gas

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