Hopper Growth of Salt Crystals

Désarnaud, Julie; Derluyn, Hannelore; Carmeliet, Jan; Bonn, Daniel; Shahidzadeh, Noushine

doi:10.1021/acs.jpclett.8b01082

Cited by 56 publications

(51 citation statements)

References 27 publications

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“…[165][166][167] NaCl crystallization was studied in individual solution plugs in microcapillaries, where maintenance in a controlled humidity environment leads to solution evaporation and the build-up of supersaturation ( Figure 13). [168][169][170] A very high supersolubility of S ≈ 1.6 ± 0.2 was recorded, where this compares with the limit of metastability of NaCl of S ≈ 1.0 determined from cooling experiments. These highly supersaturated solutions could remain stable for days until a perturbation to the system such as a change in temperature triggers nucleation.…”

Section: Droplets In Microcapillariessupporting

confidence: 68%

Crystallization in Confinement

2020

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Many crystallization processes of great importance, including frost heave, biomineralization, the synthesis of nanomaterials, and scale formation, occur in small volumes rather than bulk solution. Here, the influence of confinement on crystallization processes is described, drawing together information from fields as diverse as bioinspired mineralization, templating, pharmaceuticals, colloidal crystallization, and geochemistry. Experiments are principally conducted within confining systems that offer well‐defined environments, varying from droplets in microfluidic devices, to cylindrical pores in filtration membranes, to nanoporous glasses and carbon nanotubes. Dramatic effects are observed, including a stabilization of metastable polymorphs, a depression of freezing points, and the formation of crystals with preferred orientations, modified morphologies, and even structures not seen in bulk. Confinement is also shown to influence crystallization processes over length scales ranging from the atomic to hundreds of micrometers, and to originate from a wide range of mechanisms. The development of an enhanced understanding of the influence of confinement on crystal nucleation and growth will not only provide superior insight into crystallization processes in many real‐world environments, but will also enable this phenomenon to be used to control crystallization in applications including nanomaterial synthesis, heavy metal remediation, and the prevention of weathering.

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Section: Droplets In Microcapillariessupporting

confidence: 68%

Crystallization in Confinement

2020

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“…Previously reported activation energies for NaCl growth are similar, around 20 kJ/mol. 22 The difference of a factor of about 2 is probably due to the fact that the process here is somewhat different. In ref ( 22 ) the growth of single crystals was studied; here we have secondary nucleation, and because of the very specific shape of the “legs”, the incorporation of molecules can occur only at specific crystalline faces which can lead to a higher activation energy.…”

mentioning

confidence: 94%

“…To see whether this can account for our observations, we start with the crystal growth rate, which can be described by 20 , 21 where K is the overall growth coefficient, S = m / m s , the supersaturation ( m being the NaCl concentration and m s the saturation concentration), and g is the growth rate order. Previous experimental work has shown 22 that the growth rate order g , which is a function of the supersaturation, is unity for supersaturations S m < 1.45. In our case, we can take g = 1, as the mechanism of leg formation consists of secondary nucleation and consequently the supersaturation is low.…”

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confidence: 96%

Self-Lifting NaCl Crystals

Salim

Kolpakov

Bonn

et al. 2020

J. Phys. Chem. Lett.

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We show that macroscopic crystals of NaCl that form from evaporating drops of aqueous salt solutions can spontaneously lift themselves up and away from a hydrophobic surface. At the end of the evaporation process, tiny crystals of NaCl grow onto larger ones and form “legs” that push the large crystals away from the surface. The temperature dependence of the lifting speed is found to exhibit Arrhenius behavior with an activation energy similar to that of crystals growing in solution: the crystal growth itself determines the lifting speed that can be up to half a centimeter per minute. We show that surface hydrophobicity is a necessary but not a sufficient condition to obtain this “self-lifting” behavior.

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“…From this growth rate (G), we estimated the supersaturation [ S = actual concentration/equilibrium saturation concentration] from equation 1 in ref. 9 G = K( S −1) a , to be S < 1.002 using a growth constant value K = 9.0 µm/s corrected for 19 °C from Fig. 4 in ref.…”

Section: Resultsmentioning

confidence: 99%

“…There are several methods for the growth of NaCl hopper cubes under normal gravity. The crystallization of NaCl has been investigated in microcapillaries with diameters of 20–2000 µm 9,15 by evaporation of brine at 21 °C under a wide range of supersaturation. With these spatially restricted conditions, gravity driven convection could be reduced thus hopper cubes grew in a diffusion dominated regime with Pe ~ 10 −2 − 10 −3 at the point of nucleation.…”

Section: Methodsmentioning

confidence: 99%

Comparison of sodium chloride hopper cubes grown under microgravity and terrestrial conditions

Pettit

Fontana²

2019

npj Microgravity

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Sodium chloride (NaCl) grown in terrestrial conditions form hopper cubes under diffusion controlled mass transport (Péclet number: ≪ 1), high supersaturations (S > 1.45), and fast growth rates (10–110 µm/s) over periods only maintainable for seconds to minutes yielding hopper cubes typically <250 µm. Here we report on NaCl hopper cubes grown in microgravity on the International Space Station (ISS) by evaporation of brine. They grew under diffusion limited mass transport (Péclet number: ~4 × 10−4 − 4) at low supersaturation (S < 1.002) and slow growth rates (0.34–1 µm/min) over periods of days to weeks. Due to the lack of sedimentation, symmetrical hopper cubes, 2–8 mm were produced. The most striking differences between microgravity and terrestrial gravity hopper growth conditions are low supersaturation and slow growth rates over long periods of time. Large, 1–20 cm naturally occurring symmetrical NaCl hopper cubes are found suspended in brine soaked mud, hypothesized to be produced in a slow growth, diffusion dominated environment. We speculate these geologic conditions allow for hopper growth similar to that of microgravity.

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Hopper Growth of Salt Crystals

Cited by 56 publications

References 27 publications

Crystallization in Confinement

Crystallization in Confinement

Self-Lifting NaCl Crystals

Comparison of sodium chloride hopper cubes grown under microgravity and terrestrial conditions

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