Crystal Nucleation Process Research Articles

Water Vapor Sorption Isotherms of Salt-affected Soils

Salt-affected soils, including saline and alkali soils, cover about 7% of the land area on earth. Their interaction with water differs from non-saline soils, thereby exhibiting distinct fundamental properties and mechanical and hydrological behaviors. The soil-water interaction is generally assessed by water vapor sorption isotherm, i.e., the relationship between soil water content and ambient relative humidity under isotherm conditions. Yet to date, there still lacks a comprehensive dataset of water vapor sorption isotherms of salt-affected soils. This study presents a water vapor isotherm dataset encompassing six distinct soil types, ranging from sandy soil to expansive clayey soils. These soils were mixed with four salt types, including NaCl, KCl, MgCl2, and LiCl, at varying salt content, yielding 33 combinations of salt-affected soil samples. The results reveal three intriguing features of vapor sorption behaviors of salt-affected soils: (1) the presence of soil lowers the deliquescence relative humidity (DRH) of the salt in it, suggesting a potential interaction between soil solid and salt crystals; (2) the wetting-drying isotherm hysteresis of salt-affected soils significantly increase with salt content, even for non-expansive soils, implying a crystal nucleation process of salts in soils upon drying; (3) Sodium salt abnormally lowers adsorption capacity of Ca-montmorillonite in low RH range, demonstrating the existence of cation exchange between salt and interlayer cations.

Phase behavior and crystal nucleation of hard triangular prisms.

The interplay between densification and positional ordering during the process of crystal nucleation is a greatly investigated topic. Even for the simplest colloidal model-hard spheres-there has been much debate regarding the potential foreshadowing of nucleation by significant fluctuations in either local density or local structure. Considering anisotropic particles instead of spheres adds a third degree of freedom to the self-organization process of crystal nucleation: orientational ordering. Here, we investigate the crystal nucleation of hard triangular prisms. Using Monte Carlo simulations, we first carefully determine the crystal-fluid coexistence values and calculate the nucleation barriers for two degrees of supersaturation. Next, we use brute force simulations to obtain a large set of spontaneous nucleation events. By studying the time evolution of the local density, positional ordering, and orientational ordering in the region in which the nucleus first arises, we demonstrate that all local order parameters increase simultaneously from the very start of the nucleation process. We thus conclude that we observe no precursor for the crystal nucleation of hard triangular prisms.

Effects of structure similar additive on the crystallization of L-phenylalanine from aqueous solution

Effects of structure similar additive on the crystallization of L-phenylalanine from aqueous solution

Morphological regulation of Pt/CeO2 and its catalytic dehydrogenation of methylcyclohexane in fixed bed reactor

Morphological regulation of Pt/CeO2 and its catalytic dehydrogenation of methylcyclohexane in fixed bed reactor

Preparation of UiO-66 membrane through heterogeneous nucleation assisted growth strategy for efficient CO2 capture under humid conditions

Preparation of UiO-66 membrane through heterogeneous nucleation assisted growth strategy for efficient CO2 capture under humid conditions

Efficient and Highly Stable Lateral Perovskite Single‐Crystal Solar Cells through Crystal Engineering and Weak Ion Migration

AbstractThe lateral device structure for perovskite solar cells (PSCs) has garnered significant attention, primarily due to its elimination of the need for expensive transparent electrodes. However, the performance of lateral devices, which are more sensitive to crystal quality and charge carrier transport bottlenecks, has lagged far behind the predominant vertical PSCs. Herein, by modulating the crystal nucleation and growth processes of thin FA0.75MA0.25PbI3 (FA = formamidinium; and MA = methylammonium) single crystals, crystal quality and carrier transport are improved, resulting in a power conversion efficiency (PCE) of 12.64%, a record for lateral PSCs. Investigation of the device's stability reveals that iodide ion migration is suppressed due to a reduction in the iodide vacancy concentration combined with weak interface iodide ion migration. It is shown that the latter effect is a result of the perpendicular direction of the ion migration and the electric field in the lateral PSCs. Consequently, these lateral single‐crystal PSCs display remarkable operational stability, retaining 100% of their initial PCE after 1200 h of steady‐state output at the maximum power point voltage (Vmpp) under 1 sun illumination. This work highlights the advantages of lateral single‐crystal devices and their potential to address key ion migration issues of PSCs.

Improving Hybrid Tin Halide Films by Tin Trifluoromethanesulfonate for Lead-Free Perovskite Solar Cells.

Tin-based perovskite solar cells (Sn-PSCs) without toxic lead ions outperform other types of lead-free PSCs in terms of photovoltaic performance. To avoid the oxidation of Sn2+ cations and the formation of vacancy defects, most reports involve the addition of SnF2 to the perovskite precursor solution, but hybrid tin halide (Sn-PVK) films still suffer from poor crystallinity and stability. In this work, we used an alternative additive of tin trifluoromethanesulfonate (Sn(OTF)2). Compared to SnF2, the solubility of Sn(OTF)2 in the precursor solution is greatly improved, and the crystal nucleation process is delayed, resulting in the enhancement of crystal growth. The coordination ability of the OTF- anions suppresses the oxidation of Sn2+ cations, which promotes the stability of Sn-PVK films. By replacing the conventional additive of SnF2 with Sn(OTF)2, the device achieves an increase in power conversion efficiency from 7.96% to 10.3%, while the stability of the devices is improved simultaneously.

The impact of crystal phase transition on the hardness and structure of kidney stones

Calcium oxalate kidney stones, the most prevalent type of kidney stones, undergo a multi-step process of crystal nucleation, growth, aggregation, and secondary transition. The secondary transition has been rather overlooked, and thus, the effects on the disease and the underlying mechanism remain unclear. Here, we show, by periodic micro-CT images of human kidney stones in an ex vivo incubation experiment, that the growth of porous aggregates of calcium oxalate dihydrate (COD) crystals triggers the hardening of the kidney stones that causes difficulty in lithotripsy of kidney stone disease in the secondary transition. This hardening was caused by the internal nucleation and growth of precise calcium oxalate monohydrate (COM) crystals from isolated urine in which the calcium oxalate concentrations decreased by the growth of COD in closed grain boundaries of COD aggregate kidney stones. Reducing the calcium oxalate concentrations in urine is regarded as a typical approach for avoiding the recurrence. However, our results revealed that the decrease of the concentrations in closed microenvironments conversely promotes the transition of the COD aggregates into hard COM aggregates. We anticipate that the suppression of the secondary transition has the potential to manage the deterioration of kidney stone disease.

Hydration mechanism and photocatalytic antibacterial performance of cement-based composites modified by hydrophilic nano-TiO2 particles

Hydration mechanism and photocatalytic antibacterial performance of cement-based composites modified by hydrophilic nano-TiO2 particles

Using brewing waste diatomite activated by ball milling to simple and sustainable synthesis of nano-H-ZSM-5 aggregates

Using brewing waste diatomite activated by ball milling to simple and sustainable synthesis of nano-H-ZSM-5 aggregates

Online In Situ Real-Time Experimental Investigation of the Crystallization Characteristics and Kinetic Models during the Nucleation and Growth Process of Para-Xylene Suspension Crystallization

Online In Situ Real-Time Experimental Investigation of the Crystallization Characteristics and Kinetic Models during the Nucleation and Growth Process of Para-Xylene Suspension Crystallization

Recovery of sulphur dioxide by converter dust synergistic coke decomposition of phosphogypsum

Recovery of sulphur dioxide by converter dust synergistic coke decomposition of phosphogypsum

Recent Theoretical Advancement of Boron-Rich Compounds for Applications in High-Density Energy Conversion Devices

Boron-rich compounds (IBCs) such as boron suboxide (B6O) and boron subphosphide (B12P2) are derived from the α-rhombohedral boron lattice with extreme hardness and unusual electrical properties. These compounds display an extraordinary self-healing ability to repair the lattice defects generated from exposure to high-energy irradiation. This unique ability will enable these boron-rich compounds to be deployed in nuclear battery devices for space or deep-sea exploration applications when coupled with their high hole mobility.Synthesis and control of the stoichiometry of IBCs are the key technical challenge. For instance, the electrical properties of B6O are susceptible to specific B:O ratios. Thus far, the highest quality B6O crystals were obtained from high-pressure, high-temperature (HP-HT) experiments using mixed boron and boron oxide powders. Nevertheless, a mature synthesis protocol yielding consistent, high-quality B6O crystals has not been established.In this talk, density functional theory (DFT) was used to understand how the structural, electronic, and thermodynamic stabilities of B6O (and other IBCs) are influenced by the interstitial elements and point defects at the icosahedral sites. Using the hybrid HSE functional, we confirmed that the perfect B6O bulk is a p-type semiconductor with a direct band gap of 2.8 eV. Furthermore, by screening the α-boron compounds systematically, we found that a simple octet rule may offer a consistent explanation for the variations in the computed electronic structures. Then, the thermodynamic calculations based on the DFT method predict that formations of interstitial defects become favorable only at higher temperatures.To understand the self-healing property, the nudged elastic band (NEB) method was employed to identify the minimum energy pathways for the diffusions of dislocated B and O atoms. The diffusion of icosahedral B atoms has an energy barrier of 0.16 eV, confirming that the boron vacancies can be repaired with little kinetic limitation. Nevertheless, a substantially perturbed lattice requires more complex structural reorganization and thus incurs higher barriers (> 1 eV).Lastly, reactive molecular dynamics simulations with a frozen core were performed to gain insights into the initial crystal nucleation process using a newly developed ReaxFF force field. For the first time, we can gain a molecular perspective on the formations of the boron icosahedra (B12) motif and the energetic profile. Such knowledge will aid the experimental design of IBC synthesis.

Effects of Structural Relaxation of Glass-Forming Melts on the Overall Crystallization Kinetics in Cooling and Heating.

In the theoretical treatment of crystallization, it is commonly assumed that the relaxation processes of a liquid proceed quickly as compared to crystal nucleation and growth processes. Actually, it is supposed that a liquid is always located in the metastable state corresponding to the current values of pressure and temperature. However, near and below the glass transition temperature, Tg, this condition is commonly not fulfilled. In such cases, in the treatment of crystallization, deviations in the state of the liquid from the respective metastable equilibrium state have to be accounted for when determining the kinetic coefficients governing the crystallization kinetics, the thermodynamic driving force of crystallization, and the surface tension of the aggregates of the newly evolving crystal phase including the surface tension of critical clusters considerably affecting the crystal nucleation rate. These factors may greatly influence the course of the overall crystallization process. A theoretical analysis of the resulting effects is given in the present paper by numerical solutions of the J(ohnson)-M(ehl)-A(vrami)-K(olmogorov) equation employed as the tool to model the overall crystallization kinetics and by analytical estimates of the crystallization peak temperatures in terms of the dependence on cooling and heating rates. The results are shown to be in good agreement with the experimental data. Possible extensions of the theory are anticipated and will be explored in future analysis.

Prediction of the phase diagram of liquid–liquid phase separation during crystallization via a molecular mechanism study

Prediction of the phase diagram of liquid–liquid phase separation during crystallization via a molecular mechanism study

The role of solute conformation, solvent–solute and solute–solute interactions in crystal nucleation

AbstractThe induction time for nucleation can differ based on the solutions used to conduct a crystallization, which can in turn impact the efficiency and economics of a crystallization process, the crystal size distribution, the morphology and ultimately functionality of the final product. Establishing a link between the nucleation pathway/solution structure and nucleation induction time is essential to achieve improved comprehension of the process of crystal nucleation from solution. In this study, the role of solute conformation, solvent–solute interaction, and solute–solute interaction in nucleation was examined using tolbutamide as a model compound in toluene and toluene–alcohol solutions. Through a combination of induction time experiments, attenuated total reflection Fourier transformed infrared spectroscopy, nuclear magnetic resonance spectroscopy, molecular dynamics simulations, and quantum chemical calculations, it was found that not only solvent–solute interactions but also solute–solute interactions and structural similarities between molecular self‐assemblies in the solution and synthons in the crystal structure, can significantly influence the nucleation induction time.

The Crystallization of Disordered Materials under Shock Is Governed by Their Network Topology.

When the shock load is applied, materials experience incredibly high temperature and pressure conditions on picosecond timescales, usually accompanied by remarkable physical or chemical phenomena. Understanding the underlying physics that governs the kinetics of shocked materials is of great importance for both physics and materials science. Here, combining experiment and large-scale molecular dynamics simulation, the ultrafast nanoscale crystal nucleation process in shocked soda-lime silicate glass is investigated. By adopting topological constraints theory, this study finds that the propensity of nucleation is governed by the connectivity of the atomic network. The densification of local networks, which appears once the crystal starts to grow, results in the underconstrained shell around the crystal and prevents further crystallization. These results shed light on the nanoscale crystallization mechanism of shocked materials from the viewpoint of topological constraint theory.

Crystallization discrepancies in Mg65Zn30Ca5 metallic glass ribbon and thin film revealed by nanocalorimetry

Crystallization discrepancies in Mg65Zn30Ca5 metallic glass ribbon and thin film revealed by nanocalorimetry

Hydration and microstructure of ternary high-ferrite Portland cement blends incorporating a large amount of limestone powder and fly ash

Hydration and microstructure of ternary high-ferrite Portland cement blends incorporating a large amount of limestone powder and fly ash

Impact of Crystal Nuclei on Dissolution of Amorphous Drugs.

Amorphous drugs are used to improve bioavailability of poorly water-soluble drugs. Crystallization must be managed to take full advantage of this formulation strategy. Crystallization of amorphous drugs proceeds in a sequence of crystal nucleation and growth, with different kinetics. At low temperatures, crystal nucleation is fast, but crystal growth is slow. Therefore, amorphous drugs may generate dense but nanoscale crystal nuclei. Such tiny nuclei cannot be detected using routine powder X-ray diffraction (PXRD) and polarized light microscopy (PLM). However, they may negate the dissolution advantage of amorphous drugs. In this work, for the first time, the impact of crystal nuclei on dissolution of amorphous drugs was studied by monitoring the real-time dissolution from amorphous drug films, with and without crystal nuclei, and the evolving crystallinity in the films. Three model drugs (ritonavir/RTV, posaconazole/POS, and nifedipine/NIF) were chosen to represent different crystallization tendencies in the supercooled liquid state, namely, slow-nucleation-and-slow-growth (SN-SG), fast-nucleation-and-slow-growth (FN-SG), and fast-nucleation-and-fast-growth (FN-FG), respectively. We find that although the amorphous films containing nuclei do not show obvious differences from the nuclei-free films under PLM and PXRD before dissolution, they have inferior dissolution performance relative to the nuclei-free amorphous films. For SN-SG drug RTV, crystal nuclei have negligible impact on the crystallization of amorphous films, dissolution rate, and supersaturation achieved. However, they cause earlier de-supersaturation by inducing crystallization in solution as heterogeneous seeds. For FN-SG drug POS and FN-FG drug NIF, crystal nuclei accelerate crystallization in the amorphous films leading to lower supersaturation achieved with POS, and elimination of any supersaturation with NIF. Dissolution profiles of amorphous films can be further analyzed using a derivative function of the apparent dissolution rate, which yields amorphous solubility, initial intrinsic dissolution rate, and onset of crystallization in the amorphous films. This study highlights that although crystal nuclei are undetectable with routine analytical methods, they can significantly negate, or even eliminate, the dissolution advantage of amorphous drugs. Hence, understanding crystal nucleation process and developing approaches to prevent it are necessary to fully realize the benefits of amorphous solids.