Nucleation in supersaturated potassium dihydrogen orthophosphate solutions

Joshi, M. S.; Antony, A. V.

doi:10.1016/0022-0248(79)90100-3

Cited by 53 publications

(34 citation statements)

References 10 publications

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“…We demonstrate an unprecedented degree of supersaturation with KH 2 PO 4 (KDP) aqueous solution, which is more than three times over previously reported values (31)(32)(33)(34)(35)(36)(37)(38)(39) (Table S1) by using the solution ESL apparatus. A crystal-solution interfacial free energy value estimated by CNT was also found to be much greater than previously reported (31)(32)(33)(34)(35)(36)38).…”

Section: Significancesupporting

confidence: 62%

“…A crystal-solution interfacial free energy value estimated by CNT was also found to be much greater than previously reported (31)(32)(33)(34)(35)(36)38). In addition, we measure two distinctive probability distributions for the nucleation events as a function of supersaturation, which implies a possible existence of two different solution states.…”

Section: Significancementioning

confidence: 59%

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Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH 2 PO 4 (KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a highconcentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.multipath nucleation | liquid-droplet levitation | supersaturation | in situ X-ray diffraction | in situ micro-Raman spectroscopy N ucleation is the first step toward crystallization, in which atoms or particles aggregate to form clusters in a metastable liquid, called crystal nuclei. The crystal nuclei in metastable liquid grow continuously if their size exceeds a critical limit, and are subsequently stabilized. Based on the classical nucleation theory (CNT) (1, 2), nucleation is mainly governed by two factors, that is, interfacial free energy and volume Gibbs free energy (or chemical potential) between liquid and crystal phases. Although the volume Gibbs free energy acts to stabilize the crystal nuclei, the interfacial free energy works as an energy barrier preventing the formation of the nuclei. If the crystal-liquid interfacial free energy creates a sufficiently high energy barrier, the liquid can be supercooled, supersaturated, or even supercompressed. In case of liquid metals (3-6), the crystal-liquid interfacial free energy arises from configurational entropy differences between crystal and liquid. That is, the greater difference in local structural orderings between crystal and liquid phases results in higher interfacial free energy, which consequently leads to a higher nucleation barrier and thus deeper supercooling. This concept has been verified in various metallic systems for elements (7) and many alloys (8-12). However, many experimental and theoretical investigations have raised questions that CNT may not be adequate to describe the initial nucleation processes in biomaterials (13-17) and minerals (18)(19)(20)(21)(22)(23)(24)(25)(26).Recently, an alternate nucleation mechanism, called multipathway nucleation (or crystallization) (13-23, 25, 26), has been proposed fo...

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Section: Significancesupporting

confidence: 62%

Section: Significancementioning

confidence: 59%

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…This value is significantly greater than any other results previously reported [52][53][54][55][56][57][58][59] (i.e. σ = 2~16.87 mJ/m 2 for s = 1.2~1.95).…”

Section: Metastable Monoclinic Kh 2 Po 4 (Kdp) Crystal Formation Fromcontrasting

confidence: 54%

Formation of Metastable Crystals from Supercooled, Supersaturated, and Supercompressed Liquids: Role of Crystal-Liquid Interfacial Free Energy

Lee

2017

Crystals

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Abstract:The formation mechanism of metastable crystals from metastable liquids still remains elusive, although controlling the metastability of crystals and liquids already plays a crucial role in designing new materials in physics, chemistry, biology, and materials science. This review article describes how metastable phases can be obtained by controlling temperature, concentration, and pressure. In particular, I show the role of crystal-liquid interfacial free energy in the formation of metastable crystals from metastable liquids at a given driving force. In a microscopic viewpoint, local structure similarity between the metastable crystals and liquid determines the crystal-liquid interfacial free energy, and thus the nucleation barrier for the metastable crystals. The effect of the interfacial free energy on the formation of metastable crystals from supercooled, supersaturated, and supercompressed liquids will be demonstrated with metallic liquids, aqueous solutions, and water.

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“…Therefore, sparingly soluble salts in aqueous solution always have much higher interfacial free energies than soluble salts. Thus the reported values for NH 4 Cl, KDP, and NaCl are 1.5±10 mJ m À2 [43,44] and the corresponding values for minerals such as calcite, CaCO 3 , [45] BaSO 4 , [46] and calcium phosphates [47] are 30±300 mJ m…”

Section: Nm) Than Those At Lower Undersaturation (mentioning

confidence: 95%

Dissolution of Crystallites: Surface Energetic Control and Size Effects

2004

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Traditional understanding of dissolution assumes that the reaction is spontaneous and continues until equilibrium is reached. This paper presents theoretical and experimental data to support a dissolution mechanism that involves the existence of critical conditions for dissolution, in which the reaction is accompanied by the formation of pits and the subsequent displacement of pit steps. The accompanying increase in surface roughness leads to changes in surface energy with losses of crystal mass that are positive rather than negative and the existence of critical dissolution conditions. Critical pits and dissolution steps are verified experimentally and a relationship between the size and rate of displacement of steps is also demonstrated, in which the rate decreases with size and approaches zero at a critical size, r*. These microscopic step dynamics are consistent with the observed size-effects in bulk dissolution, which cannot be explained using traditional dissolution theories. The observed size effects include self-inhibition, in which the dissolution rate decreases with extent of reaction, dissolution suppression, and periodic resumption. These interesting dissolution phenomena are only readily displayed when the sizes of dissolving crystallites fall in the same range as the critical size (i.e., within 50r*). It is interesting to note that natural biominerals and many nanoparticles fall into this category, so that their suspensions can be dynamically stabilized without dissolution in undersaturated supporting media. The current research implies that dissolution kinetics cannot be understood well without appealing to fundamental physical concepts about the energetic control of dissolution steps on a molecular level. A new dissolution model for crystallites is introduced systemically.

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Nucleation in supersaturated potassium dihydrogen orthophosphate solutions

Cited by 53 publications

References 10 publications

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Formation of Metastable Crystals from Supercooled, Supersaturated, and Supercompressed Liquids: Role of Crystal-Liquid Interfacial Free Energy

Dissolution of Crystallites: Surface Energetic Control and Size Effects

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