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

2016 ◽  
Vol 113 (48) ◽  
pp. 13618-13623 ◽  
Author(s):  
Sooheyong Lee ◽  
Haeng Sub Wi ◽  
Wonhyuk Jo ◽  
Yong Chan Cho ◽  
Hyun Hwi Lee ◽  
...  
Keyword(s):  
Deep Level ◽  
Potassium Dihydrogen Phosphate ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Dihydrogen Phosphate ◽  
High Concentration ◽  
Liquid Phases ◽  
Nucleation Sites ◽  
Solution Studies

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 KH2PO4(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 high-concentration 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.

scholarly journals Nonclassical Nucleation—Role of Metastable Intermediate Phase in Crystal Nucleation: An Editorial Prefix

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 174
Author(s):  
Fajun Zhang ◽  
José A. Gavira ◽  
Geun Woo Lee ◽  
Dirk Zahn
Keyword(s):  
Intermediate Phase ◽  
Solid Phase ◽  
Early Stage ◽  
Order Parameters ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Supersaturated Solution ◽  
Liquid Phases

Classical nucleation theory (CNT), which was established about 90 years ago, represents the most commonly used theory in describing nucleation processes. For a fluid-to-solid phase transition, CNT states that the solutes in a supersaturated solution reversibly form small clusters. Once a cluster reaches its critical size, it becomes thermodynamically stable and is favored for further growth. One of the most important assumptions of CNT is that the nucleation process is described by one reaction coordinate and all order parameters proceed simultaneously. Recent studies in experiments, computer simulations, and theory have revealed nonclassical features in the early stage of nucleation. In particular, the decoupling of order parameters involved during a fluid-to-solid transition leads to the so-called two-step nucleation mechanism, in which a metastable intermediate phase (MIP) exists in parallel to the initial supersaturated solution and the final crystals. These MIPs can be high-density liquid phases, mesoscopic clusters, or preordered states. In this Special Issue, we focus on the role of the various MIPs in the early stage of crystal nucleation of organic materials, metals and alloys, aqueous solutions, minerals, colloids, and proteins, and thus on various scenarios of nonclassical pathways of crystallization.

scholarly journals Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

2022 ◽  
Vol 3 ◽  
Author(s):  
Vitalii Starchenko
Keyword(s):  
Reactive Transport ◽  
Surface Reaction ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Reactive Flow ◽  
Natural Environments ◽  
Pore Scale ◽  
Arbitrary Lagrangian Eulerian ◽  
Mineral Precipitation

A fundamental understanding of mineral precipitation kinetics relies largely on microscopic observations of the dynamics of mineral surfaces exposed to supersaturated solutions. Deconvolution of tightly bound transport, surface reaction, and crystal nucleation phenomena still remains one of the main challenges. Particularly, the influence of these processes on texture and morphology of mineral precipitate remains unclear. This study presents a coupling of pore-scale reactive transport modeling with the Arbitrary Lagrangian-Eulerian approach for tracking evolution of explicit solid interface during mineral precipitation. It incorporates a heterogeneous nucleation mechanism according to Classical Nucleation Theory which can be turned “on” or “off.” This approach allows us to demonstrate the role of nucleation on precipitate texture with a focus at micrometer scale. In this work precipitate formation is modeled on a 10 micrometer radius particle in reactive flow. The evolution of explicit interface accounts for the surface curvature which is crucial at this scale in the regime of emerging instabilities. The results illustrate how the surface reaction and reactive fluid flow affect the shape of precipitate on a solid particle. It is shown that nucleation promotes the formation of irregularly shaped precipitate and diminishes the effect of the flow on the asymmetry of precipitation around the particle. The observed differences in precipitate structure are expected to be an important benchmark for reaction-driven precipitation in natural environments.

Nucleation and Glass Formation

1985 ◽  
Vol 57 ◽  
Author(s):  
D. R. Uhlmann ◽  
M. C. Weinberg
Keyword(s):  
Glass Formation ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Oxide Glass ◽  
Classical Nucleation Theory ◽  
Nucleation Kinetics ◽  
Formation Behavior ◽  
Homogeneous Crystal ◽  
Exponential Factors

AbstractThe role of nucleation kinetics in affecting glass formation behavior is discussed. Also considered are measurements of homogeneous crystal nucleation in a variety of liquids. For a number of oxide glass-forming liquids, available data indicate pre-exponential factors which are larger than those predicted from classical nucleation theory by factors of 1017 to 1049. Possible sources of this discrepancy are discussed.

scholarly journals Entropy and the Tolman Parameter in Nucleation Theory

Entropy ◽  
2019 ◽  
Vol 21 (7) ◽  
pp. 670 ◽  
Author(s):  
Jürn W. P. Schmelzer ◽  
Alexander S. Abyzov ◽  
Vladimir G. Baidakov
Keyword(s):  
Surface Tension ◽  
Size Dependence ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Alternative Methods ◽  
Classical Nucleation Theory ◽  
Component Systems ◽  
Bulk Parameters ◽  
Curvature Dependence ◽  
Gibbs Theory

Thermodynamic aspects of the theory of nucleation are commonly considered employing Gibbs’ theory of interfacial phenomena and its generalizations. Utilizing Gibbs’ theory, the bulk parameters of the critical clusters governing nucleation can be uniquely determined for any metastable state of the ambient phase. As a rule, they turn out in such treatment to be widely similar to the properties of the newly-evolving macroscopic phases. Consequently, the major tool to resolve problems concerning the accuracy of theoretical predictions of nucleation rates and related characteristics of the nucleation process consists of an approach with the introduction of the size or curvature dependence of the surface tension. In the description of crystallization, this quantity has been expressed frequently via changes of entropy (or enthalpy) in crystallization, i.e., via the latent heat of melting or crystallization. Such a correlation between the capillarity phenomena and entropy changes was originally advanced by Stefan considering condensation and evaporation. It is known in the application to crystal nucleation as the Skapski–Turnbull relation. This relation, by mentioned reasons more correctly denoted as the Stefan–Skapski–Turnbull rule, was expanded by some of us quite recently to the description of the surface tension not only for phase equilibrium at planar interfaces, but to the description of the surface tension of critical clusters and its size or curvature dependence. This dependence is frequently expressed by a relation derived by Tolman. As shown by us, the Tolman equation can be employed for the description of the surface tension not only for condensation and boiling in one-component systems caused by variations of pressure (analyzed by Gibbs and Tolman), but generally also for phase formation caused by variations of temperature. Beyond this particular application, it can be utilized for multi-component systems provided the composition of the ambient phase is kept constant and variations of either pressure or temperature do not result in variations of the composition of the critical clusters. The latter requirement is one of the basic assumptions of classical nucleation theory. For this reason, it is only natural to use it also for the specification of the size dependence of the surface tension. Our method, relying on the Stefan–Skapski–Turnbull rule, allows one to determine the dependence of the surface tension on pressure and temperature or, alternatively, the Tolman parameter in his equation. In the present paper, we expand this approach and compare it with alternative methods of the description of the size-dependence of the surface tension and, as far as it is possible to use the Tolman equation, of the specification of the Tolman parameter. Applying these ideas to condensation and boiling, we derive a relation for the curvature dependence of the surface tension covering the whole range of metastable initial states from the binodal curve to the spinodal curve.

Studies of Potassium Dihydrogen Phosphate (KDP) Crystals Doped with Potassium Dichromate (PD) using ICP and UV Spectrophotometer

2007 ◽  
Vol 1015 ◽  
Author(s):  
Selemani Seif ◽  
Ravindra Behari Lal
Keyword(s):  
Potassium Dichromate ◽  
Potassium Dihydrogen Phosphate ◽  
Dihydrogen Phosphate ◽  
High Concentration ◽  
Potassium Dihydrogen ◽  
Evaporation Technique ◽  
Uv Transmittance ◽  
Kdp Crystals ◽  
Specific Amount

AbstractThis paper reports on preparation and characterization of Potassium Dihydrogen Phosphate (KDP) crystals doped with Potassium Dichromate (PD). The crystals were grown at room temperature by solution evaporation technique. The grown crystals were polished, sliced, and analyzed using UV-Spectrophotometer, which showed high concentration of PD impurities in KDP crystals at 200-280 nanometer. These concentrations were then verified using ICP measurements to determine specific amount in ppm of chromium ions in KDP crystals. In additional to that, the UV-transmittance data of these crystals were then converted to absorbance per thickness, and used to calculate absorption coefficients, extinction coefficients, and refractive index as a function of wavelength. The results showed that the presence of PD impurities in the crystal matrix of KDP has played a key reformative role in the UV sensing of Potassium Diphosphate crystals.

scholarly journals Crystal Nucleation and Growth in Cross-Linked Poly(ε-Caprolactone) (PCL)

2021 ◽  
Author(s):  
Timur Mukhametzyanov ◽  
Jürn W.P. Schmelzer ◽  
Egor Yarko ◽  
Albert Abdullin ◽  
Marat Ziganshin ◽  
...  
Keyword(s):  
Average Distance ◽  
Maximum Growth ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Theoretical Interpretation ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
Transition Range ◽  
Cross Links

The crystal nucleation and overall crystallization kinetics of cross-linked poly(ε-caprolactone) was studied experimentally by fast scanning calorimetry in a wide temperature range. With an increasing degree of cross-linking, both the nucleation and crystallization half-times increase. Concurrently, the glass transition range shifts to higher temperatures. In contrast, the temperatures of the maximum nucleation and the overall crystallization rates remain the same independent of the degree of cross-linking. The cold crystallization peak temperature generally increases as a function of heating rate, reaching an asymptotic value near the temperature of the maximum growth rate. A theoretical interpretation of these results is given in terms of classical nucleation theory. In addition, it is shown that the average distance between the nearest cross-links is smaller than the estimated lamellae thickness, which indicates the inclusion of cross-links in the crystalline phase of the polymer.

scholarly journals Reversible disorder-order transitions in atomic crystal nucleation

Science ◽  
2021 ◽  
Vol 371 (6528) ◽  
pp. 498-503
Author(s):  
Sungho Jeon ◽  
Taeyeong Heo ◽  
Sang-Yeon Hwang ◽  
Jim Ciston ◽  
Karen C. Bustillo ◽  
...  
Keyword(s):  
Early Stage ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Gold Nanocrystals ◽  
Size Dependent ◽  
In Situ Electron Microscopy ◽  
Nucleation Mechanisms ◽  
Structural Fluctuations

Nucleation in atomic crystallization remains poorly understood, despite advances in classical nucleation theory. The nucleation process has been described to involve a nonclassical mechanism that includes a spontaneous transition from disordered to crystalline states, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporal resolution shows that the early stage of atomic crystallization proceeds through dynamic structural fluctuations between disordered and crystalline states, rather than through a single irreversible transition. Our experimental and theoretical analyses support the idea that structural fluctuations originate from size-dependent thermodynamic stability of the two states in atomic clusters. These findings, based on dynamics in a real atomic system, reshape and improve our understanding of nucleation mechanisms in atomic crystallization.

A Numerical Model for the Description of Massive and Lamellar Microstructure Formation in Gamma-TiAl

2007 ◽  
Vol 539-543 ◽  
pp. 1481-1486 ◽  
Author(s):  
Alain Jacot ◽  
Amin Rostamian
Keyword(s):  
Titanium Aluminides ◽  
Lamellar Microstructure ◽  
Mathematical Expression ◽  
Nucleation Theory ◽  
Matrix Composition ◽  
Classical Nucleation Theory ◽  
Modeling Approach ◽  
Alloy Chemistry ◽  
Nucleation Sites ◽  
Growth Laws

A phenomenological modeling approach has been developed to describe the massive transformation and the formation of lamellar microstructures during cooling in gamma titanium aluminides. The modeling approach is based on a combination of nucleation and growth laws which take into account the specific mechanisms of each phase transformation. Nucleation of both massive and lamellar γ is described with classical nucleation theory, accounting for the fact that nuclei are formed predominantly at α/α grain boundaries. Growth of the massive γ grains is calculated with a mathematical expression for interface-controlled reactions. A modified Zener model is used to calculate the thickening rate of the γ lamellar precipitates. The model incorporates the effect of particle impingement and rapid coverage of the nucleation sites due to growth. The driving pressures of the phase transformations are obtained form Thermo-Calc based on actual temperature and matrix composition. The model permitted investigating the influence of alloy chemistry, cooling rate and average α grain size upon the amount of massive γ and the average thickness and spacing of the lamellae. Calculated CCT diagrams were compared with experimental data collected from the literature and showed good agreement.

scholarly journals Influence of solvent on crystal nucleation of risperidone

2015 ◽  
Vol 179 ◽  
pp. 309-328 ◽  
Author(s):  
Donal Mealey ◽  
Jacek Zeglinski ◽  
Dikshitkumar Khamar ◽  
Åke C. Rasmuson
Keyword(s):  
Induction Time ◽  
Density Functional ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Functional Theory ◽  
Interfacial Energies ◽  
Solution Condition ◽  
Solvent Molecules ◽  
Influence Of Solvent

Over 2100 induction time experiments were carried out for the medium-sized, antipsychotic drug molecule, risperidone in seven different organic solvents. To reach the same induction time the required driving force increases in the order: cumene, toluene, acetone, ethyl acetate, methanol, propanol, and butanol, which reasonably well correlates to the interfacial energies as determined within classical nucleation theory. FTIR spectroscopy has been used to investigate any shifts in the spectra and to estimate the interaction of solute and solvent at the corresponding site. The solution condition has also been investigated by Density Functional Theory (DFT) calculations over (1 : 1) solvent–solute binding interactions at 8 different sites on the risperidone molecule. The DFT computational results agree with the spectroscopic data suggesting that these methods do capture the binding strength of solvent molecules to the risperidone molecule. The difficulty of nucleation correlates reasonably to the DFT computations and the spectroscopic measurements. The results of the different measurements suggest that the stronger the solvent binds to the risperidone molecule in solution, the slower the nucleation becomes.

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