Some aspects of ice crystal growth from the vapour phase; apparatus and growth kinetics in the presence of organic gases and with various nucleants

Neustaedter, Jacob; Gallily, Isaiah

doi:10.1016/0022-0248(87)90472-6

Cited by 4 publications

(2 citation statements)

References 17 publications

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“…They observed habit and crystal size changes. Neustaedter and Gallily (1987) grew snow crystals from the gas phase in the presence of 5% (molar) of several alkohols and observed a change in habit and a reduction in growth rates. Anderson et al (1969) grew snow crystals from the gas phase in the presence of unspecified, but apparently large, amounts of methyl 2-cyanoacrylate and also observed a change in crystal size and habit.…”

Section: Discussionmentioning

confidence: 98%

Snow metamorphism as revealed by scanning electron microscopy

Dominé

Lauzier

Cabanes

et al. 2003

Microscopy Res & Technique

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Current theories of snow metamorphism indicate that sublimating snow crystals have rounded shapes, while growing crystals have shapes that depend on growth rates. At slow growth rates, crystals are rounded. At moderate rates, they have flat faces with rounded edges. At fast growth rates, crystals have flat faces with sharp edges, and they have hollow faces at very fast growth rates. The main growth/sublimation mechanism is thought to be by the homogeneous nucleation of new layers at or near crystal edges. It was also suggested that the equilibrium shape of snow crystals would be temperature dependent: rounded above -10.5 degrees C, and faceted below. To test these paradigms, we have performed SEM investigations of snow samples having undergone metamorphism under natural conditions, and of snow samples subjected to isothermal metamorphism at -4 degrees and -15 degrees C in the laboratory. In general, current theories predicting crystal shapes as a function of growth rates, and of whether crystals are growing or sublimating, are verified. However, the transition in equilibrium shapes from rounded to faceted at -10.5 degrees C is not observed in our isothermal experiments that reveal a predominance of rounded shapes after more than a month of metamorphism at -4 and -15 degrees C. Some small crystals with flat faces that also have sharp angles at -15 degrees C, are observed in our isothermal experiments. These faces are newly formed, and contradict current theory. Several hypotheses are proposed to explain their occurrence. One is that they are due to sublimation at emerging dislocations.

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Section: Discussionmentioning

confidence: 98%

Snow metamorphism as revealed by scanning electron microscopy

Dominé

Lauzier

Cabanes

et al. 2003

Microscopy Res & Technique

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“…Crystals in this part of the atmosphere play important roles in radiative and chemical processes, and these roles are determined largely by the shape and sizes of the crystals as well as the surface structure. There is laboratory evidence that small concentrations of gaseous impurities alter the crystal growth shape [Anderson et a/.,1969; Hallett and Mason, 1958;Nakaya et a/.,1958;Neustaedter and Gallily, 1987;Odencrantz, 1968;Schaefer, 1949]. The uniform flux model (as opposed to the capacitance model) readily lends itself to exploration of these impurity-induced modifications of surface impedance [Nelson, 1994].…”

Section: Applicationsmentioning

confidence: 99%

New theoretical framework for studies of vapor growth and sublimation of small ice crystals in the atmosphere

Nelson¹,

Baker²

1996

J. Geophys. Res.

123

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We present a new microscopic model of growth and sublimation (g/s) of ice crystals in the atmosphere. This model is based on the assumption that the flux of vapor to the crystal surface is uniform over each flat crystal face. It thus differs fundamentally from the standard “capacitance” model for crystal growth, in which the mixing ratio is assumed uniform at the surface. In the new model the surface influence on growth is calculated self‐consistently in terms of local environmental conditions, again differing sharply from the standard models in which this influence is either ignored or assigned a uniform, externally prescribed value. The new model leads to predictions of the evolution of ice crystal shape as well as mass. We find that predicted g/s rates are generally smaller than those predicted by the earlier models. The general trends both in g/s rates and in crystal hollowing predicted by the model are consistent with field and laboratory observations. The values of certain surface parameters needed for application of our model must be found from experiment. We review and compare the relevant laboratory experiments on ice crystal g/s rates and show their lack of mutual consistency. Therefore the surface parameters inferred from these experiments are necessarily uncertain. We show that the surface parameter values can be inferred from observations of crystal hollowing, since our model allows the prediction of environmental conditions at which hollowing should occur.

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Chemical aspects of the effect of impurities in crystal growth

Veintemillas-Verdaguer

1996

Progress in Crystal Growth and Characterization of Materials

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Some aspects of ice crystal growth from the vapour phase; apparatus and growth kinetics in the presence of organic gases and with various nucleants

Cited by 4 publications

References 17 publications

Snow metamorphism as revealed by scanning electron microscopy

Snow metamorphism as revealed by scanning electron microscopy

New theoretical framework for studies of vapor growth and sublimation of small ice crystals in the atmosphere

Chemical aspects of the effect of impurities in crystal growth

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