Crystallization Mechanism Research Articles

Exploring the Potential of Halide Electrolytes for Next‐Generation All‐Solid‐State Lithium Batteries

AbstractAll‐solid‐state lithium batteries (ASSLBs) are expected to revolutionize large‐scale energy storage and electric vehicles due to their exceptional safety and high energy density. Central to this technology is the development of solid electrolytes, with halide electrolytes emerging as highly promising candidates, offering high ionic conductivity, robust electrochemical stability and excellent mechanical properties. Since the breakthrough discovery of Li3YCl6 in 2018, research on halide electrolytes has entered a new era. However, despite continuous research efforts, practical challenges persist in their application, including the need to further enhance ionic conductivity, improve moisture resistance, and achieve better compatibility with electrode materials. This review provides a comprehensive overview of recent progress and ongoing challenges in halide electrolytes, examining crystal structures, conduction mechanisms, and scalable synthesis techniques. Various modification strategies are also explored aimed at boosting ionic conductivity and electrochemical stability, with a particular focus on improving interface stability. Finally, future perspectives are outlined for designing high‐performance halide electrolyte materials, offering guidance for ongoing research efforts toward their commercial application in ASSLBs.

Spiral-Concave Prussian Blue Crystals with Rich Steps: Growth Mechanism and Coordination Regulation.

Investigating the formation and transformation mechanisms of spiral-concave crystals holds significant potential for advancing innovative material design and comprehension. We examined the kinetics-controlled nucleation and growth mechanisms of Prussian Blue crystals with spiral concave structures, and constructed a detailed crystal growth phase diagram. The spiral-concave hexacyanoferrate (SC-HCF) crystals, characterized by high-density surface steps and a low stress-strain architecture, exhibit enhanced activity due to their facile interaction with reactants. Notably, the coordination environment of SC-HCF can be precisely modulated by the introduction of diverse metals. Utilizing X-ray absorption fine structure spectroscopy and in situ ultraviolet-visible spectroscopy, we elucidated the formation mechanism of SC-HCF to Co-HCF facilitated by oriented adsorption-ion exchange (OA-IE) process. Both experimental data, and density functional theory confirm that Co-HCF possesses an optimized energy band structure, capable of adjusting the local electronic environment and enhancing the performance of the oxygen evolution reaction. This work not only elucidates the formation mechanism and coordination regulation for rich steps HCF, but also offers a novel perspective for constructing nanocrystals with intricate spiral-concave structures.

Spiral‐Concave Prussian Blue Crystals with Rich Steps: Growth Mechanism and Coordination Regulation

AbstractInvestigating the formation and transformation mechanisms of spiral‐concave crystals holds significant potential for advancing innovative material design and comprehension. We examined the kinetics‐controlled nucleation and growth mechanisms of Prussian Blue crystals with spiral concave structures, and constructed a detailed crystal growth phase diagram. The spiral‐concave hexacyanoferrate (SC‐HCF) crystals, characterized by high‐density surface steps and a low stress‐strain architecture, exhibit enhanced activity due to their facile interaction with reactants. Notably, the coordination environment of SC‐HCF can be precisely modulated by the introduction of diverse metals. Utilizing X‐ray absorption fine structure spectroscopy and in situ ultraviolet‐visible spectroscopy, we elucidated the formation mechanism of SC‐HCF to Co‐HCF facilitated by oriented adsorption‐ion exchange (OA‐IE) process. Both experimental data, and density functional theory confirm that Co‐HCF possesses an optimized energy band structure, capable of adjusting the local electronic environment and enhancing the performance of the oxygen evolution reaction. This work not only elucidates the formation mechanism and coordination regulation for rich steps HCF, but also offers a novel perspective for constructing nanocrystals with intricate spiral‐concave structures.

Investigation of orientation behavior of nematic liquid crystals on UV-irradiated polyimide films

Abstract The orientation mechanism of liquid crystals (LCs) on surfaces remains unclear, despite several methods for controlling pretilt angles. This study investigates the relationship between the surface condition of polyimide films, whose pretilt angles can be controlled by UV dose, and LC orientation behavior. Absorbance at wavelength of 200 nm and 260 nm significantly decrease, while thickness reduces approximately 4 nm. A rubbing treatment further decreases the thickness by approximately 2 nm. Atomic force microscopy confirmed the change in molecular conformation by UV-irradiation and rubbing treatment. The dispersive and polar components of the surface free energy of UV-irradiated polyimide films are evaluated, it’s found that only the polar component changes with UV dose. Additionally, we confirm that the alignment of LCs transitions from homeotropic to planar with increased UV irradiation, demonstrating that pretilt angle distribution can be spatially controlled. These results contribute to establishing a photoalignment method for pretilt angle control.

Advancing the development of supersonic natural gas liquefaction through understanding heavy hydrocarbon crystallization mechanism

During supersonic natural gas liquefaction, the solidification of heavy hydrocarbon molecules can be used to improve the efficiency of the liquefaction. This study investigates the supersonic crystallization of n-hexane using an experimental system designed by ourself for precise measurement of liquid heavy hydrocarbon vaporization. The results demonstrate that n-hexane gas condenses rapidly 1.5 cm downstream of the nozzle throat, releasing significant latent heat. The subsequent crystallization of these droplets transitions the substance fully from liquid to solid, and the latent heat released during crystallization is much lower than that during condensation. Under different conditions, we found that higher partial pressures intensify n-hexane crystallization, accelerating liquid phase growth despite slower solid phase mass increase. Furthermore, larger nozzle expansion ratios shorten the time and space distribution of the liquid phase mass fraction. Molecular dynamics simulations reveal n-hexane’s melting and surface crystallization temperatures to be approximately 160 ± 1 K and 158 ± 1 K, respectively, with a supercooling degree of 2 K, explaining the observed crystallization behavior in supercooled droplets.

Effect of surface morphology on the deformation mechanism of Cu nanocrystal under cyclic loading at different temperatures: Molecular dynamics simulations

Micro-electromechanical systems (MEMS) are often subject to mechanical vibration or temperature, the fatigue reliability of small metal parts is a potential problem for long-term operational stability. Since the MEMS packaging is performed at a high temperature of about 600 K. Therefore, in this paper, the deformation mechanisms of copper nano-single crystals with different surface morphologies under cyclic loading were investigated by molecular dynamics calculations at room temperature (300 K) and high temperature (600 K) to provide a theoretical basis for the design of copper nanomaterials. The results show that the plastic deformation modes of the models with different surface morphologies during cyclic loading are mainly Shockley partial dislocations slipping along {111}. In contrast, the fatigue damage modes are extrusion intrusion induced by high shear strain. Compared with the surface containing a pore, the damage caused by the circular and sharp recesses through the surface is more serious. The causes of stress concentration during deformation are mainly the entanglement of Shockley partial dislocations and the generation of Lomer-Corell lock fixed dislocations. The locations of these stress concentrations will produce pores in the subsequent deformation. In addition, since periodic interfaces do not cause particularly pronounced stress concentrations and shear strain concentrations on the surface compared to other models with defects, and the resulting shear strain concentration bands are split by shear strain bands in the other direction, extrusion intrusion is prevented. Therefore, at room temperature, the model with a one-dimensional sinusoidal surface has the strongest resistance to fatigue damage, while at high temperatures, the model with a two-dimensional sinusoidal surface has the optimal resistance to fatigue damage. This provides a basis for the design of NEMS/MEMS working at high temperatures.

Crystallization of 2D TiO2 Nanosheets via Oriented Attachment of 1D Coordination Polymer.

Demystifying the molecular mechanism of growth is vital for the rational design, synthesis, and optimization of functional nanomaterials. Despite the promising perspectives and extensive efforts, the growth mechanism of atomically thin TiO2(B) nanosheets remains unclear, hence it is difficult to tune their band and surface structures. Herein, we report an oriented attachment-based crystallization mechanism of TiO2(B) nanosheets from a 1D titanium glycolate coordination polymer through hydrolysis and condensation. With time-tracking experiments, this 1D coordination polymer is found to be an intermediate in the synthesis of TiO2(B) nanosheets by using Ti alkoxides and chlorides as precursors, suggesting the universality of the 1D-to-2D growth mechanism. Such a side-to-side attachment pathway bridges the classical and nonclassical interpretations of crystallization, and meanwhile hints at the possibility of other 1D complexes as potential precursors for 2D materials.

Unraveling the multi-step crystallization mechanism of polytetrafluoroethylene, modified polytetrafluoroethylene, and their nanocomposites with boron nitride nanobarbs: Experimental insights and theoretical analysis

Unraveling the multi-step crystallization mechanism of polytetrafluoroethylene, modified polytetrafluoroethylene, and their nanocomposites with boron nitride nanobarbs: Experimental insights and theoretical analysis

Transmission enhancement mechanism of PT symmetric photonic crystal coupled with grooved sub-wavelength grating

In order to enhance the sensing characteristics of the sensor, based on the periodic sub-wavelength grating(SWG), a groove structure is introduced to make the Fano resonance waveform sharper. At the same time, based on the Parity-Time(PT) symmetry principle, by making the periodic photonic crystal meet the PT symmetry condition, the structure can absorb the energy of the emitted light on the original basis, produce the transmission enhancement effect, and make the transmission peak of the structure exceed 1. The sensing is realized by using the property that the different refractive indices of the detected medium corresponds to different transmission. When the incident light is 1550 nm, the sensitivity and FOM (Figure of Merit) value of the proposed structure reach 5.702 × 105RIU−1and 1.9 × 107 respectively, which greatly improves the performance of the sensor.

Theoretical Investigation into Polymorphic Transformation between β-HMX and δ-HMX by Finite Temperature String

Polymorphic transformation is important in chemical industries, in particular, in those involving explosive molecular crystals. However, due to simulating challenges in the rare event method and collective variables, understanding the transformation mechanism of molecular crystals with a complex structure at the molecular level is poor. In this work, with the constructed order parameters (OPs) and K-means clustering algorithm, the potential of mean force (PMF) along the minimum free-energy path connecting β-HMX and δ-HMX was calculated by the finite temperature string method in the collective variables (SMCV), the free-energy profile and nucleation kinetics were obtained by Markovian milestoning with Voronoi tessellations, and the temperature effect on nucleation was also clarified. The barriers of transformation were affected by the finite-size effects. The configuration with the lower potential barrier in the PMF corresponded to the critical nucleus. The time and free-energy barrier of the polymorphic transformation were reduced as the temperature increased, which was explained by the pre-exponential factor and nucleation rate. Thus, the polymorphic transformation of HMX could be controlled by the temperatures, as is consistent with previous experimental results. Finally, the HMX polymorph dependency of the impact sensitivity was discussed. This work provides an effective way to reveal the polymorphic transformation of the molecular crystal with a cyclic molecular structure, and further to prepare the desired explosive by controlling the transformation temperature.

Atomistic simulations of polysaccharide materials for insights into their crystal structure, nanostructure, and dissolution mechanism

AbstractCrystalline polysaccharides are abundant in nature and can be transformed into highly functional materials. However, the molecular basis for the formation of higher-order structures remains unclear. Computer simulation is an advanced tool for modeling macromolecular structures, and the atomistic simulations provide valuable information on the crystalline polysaccharides. Fiber deformation, crystalline transition, and novel nanostructures of cellulose were characterized through molecular dynamics simulations and density functional theory calculations of models of molecular chain sheets extracted from the crystal structure of the cellulose polymorphs. Extended ensemble molecular dynamics simulations were applied to analyze the artificial crystal structure of non-natural amylose analog polysaccharides, revealing the hexagonal packing of double helices through the self-assembly of molecular chains dispersed in aqueous solution. Dissolution simulations of the cellulose and chitin crystalline fibers revealed that the anions of ionic liquids, with their solvation power, played a key role in the cleavage of intermolecular hydrogen bonds in the crystal structure, whereas the cations contributed to irreversible molecular chain dispersion. The good correlation between the actual solubility of polysaccharides and the predicted number of intermolecular hydrogen bonds prompted the development of a platform that combined simulations and machine learning for high-throughput screening of solvents for cellulose and chitin.

Effects of Ta on the high temperature creep behavior and deformation mechanism of a Ni-based single crystal superalloy

The effects of Ta on the high temperature creep behavior and deformation mechanism in a Ni-based single crystal (SX) superalloy were investigated at 1120 °C/137 MPa. Ta was regarded as an essential strengthening element of the γʹ phase in the alloy, and the results indicated that the increase of Ta prolonged the creep rupture life. In this work, the addition of Ta increased the volume fraction of the γʹ phase and narrowed the γ channels, making the dislocation bowing out at the primary stage of creep more difficult. As creep continued, with a lower effective diffusion coefficient of alloying elements and larger γʹ raft thickness, the alloy with 6.5 wt% Ta addition was considered to possess the lower dislocation climbing rate, which reduced the minimum creep rate of the alloys. Subsequently, it was noted that the density of superdislocations in γʹ phase was clearly reduced with the increase of Ta. This was supposed to be the elevated Ta content in the alloy, which increased the lattice misfit and led to the formation of a denser dislocation network, thereby enhancing the interfacial strengthening effect and effectively preventing the cutting of superdislocations. The Ta effect on high-temperature creep was systematically summarized in this study, which was an important guideline for further composition design and optimization of Ni-based SX superalloys.

Crystal Structure and Molecular Mechanism of Isocitrate Lyase from Chloroflexus aurantiacus.

Chloroflexus aurantiacus is a green, nonsulfur bacterium that employs the 3-hydroxypropionate cycle to grow, using carbon dioxide/bicarbonate as its primary carbon source. Like most bacteria, it possesses the glyoxylate cycle, facilitated by malate synthase and isocitrate lyase (ICL), allowing a "tricarboxylic acid cycle" bypass. C. aurantiacus also harbors ICL, an enzyme that catalyzes reversible isocitrate cleavage into glyoxylate and succinate. This study presents the crystal structures of C. aurantiacus-derived ICL (CaICL), in its Mg2+-bound and Mn2+ and isocitrate-bound forms, elucidating its substrate-binding mechanism and catalytic loop dynamics. CaICL forms a homotetramer and interacts with isocitrate via critical active-site residues, revealing its catalytic mechanism. The stabilization of the catalytic loop and adjacent terminal regions upon isocitrate binding underscores its functional significance. These findings advance our understanding regarding ICL enzymes, offering a basis for future investigations into their biological roles and potential applications.

Mechanisms of dissolution and crystallization of amorphous glibenclamide

Amorphous solid dispersions enhance the dissolution and oral bioavailability of poorly water-soluble drugs. However, the link between polymer properties and formulation performance has not been fully clarified yet. We studied the effect of hydroxypropyl cellulose (HPC) polymers molecular weight (Mw) on the storage stability, dissolution kinetics and supersaturation stability of spray-dried amorphous glibenclamide (GLB) formulations. The solid-state stability of amorphous GLB during storage was significantly enhanced by both the 40 kDa (HPC-SSL) and 84 kDa (HPC-L) polymers, regardless of Mw differences. In contrast, HPC-SSL maintained significantly higher aqueous drug concentrations during dissolution, compared to HPC-L (its higher Mw analogue). Dedicated dissolution experiments, in situ optical microscopy and solid-state characterization revealed that aqueous drug concentrations were determined by the interplay between crystallization inhibition, drug ionization, wetting and solubilization effects: (1) HPC prevents surface nucleation, hence inhibiting crystallization, (2) intestinal colloids (bile salts and phospholipids) increase supersaturated drug concentrations via wetting and solubilization effects and (3) pH and drug ionization severely impact the degree of supersaturation. The better performance of the lower Mw HPC-SSL was due to its superior inhibition of surface crystallization. These insights into the molecular mechanisms of dissolution and crystallization of amorphous solids provide foundation for rational formulation development.

The network structure and properties of a unique mining solid waste-based glass-ceramics

To alleviate the environmental pollution caused by the stockpile of mining-based, such as coal-based solid waste, mining solid waste-based CaO-MgO-Al2O3-SiO2 (CMAS) glass-ceramics with a diopside phase as the main crystalline phase was developed by one-step sintering method, and the effect of different solid waste content on the network structure and properties were investigated. The results show that, with the diversification of solid waste content, the crystallization temperature (Tp), the amount of Fe3+ concentration, and diopside crystalline, the main structure of glass Q2 changed also. Accordingly, significant changes have occurred in properties such as the bending strength, Vickers hardness, and density. Optimizing the raw material ratio, crystallization mechanism, a mining solid waste-based glass-ceramic with unique network structure is well developed and the bending strength, Vickers hardness, fracture toughness, and density reaches maximum values of 175.19 MPa, 10.47 GPa, 2.03 MPa⋅m1/2, and 3.00 g/cm3, respectively. The findings contribute significantly to the development of durable and reliable materials for the utilization of mining solid waste resources.

Use of magnetic fields to impact glass-transition and crystallization during manufacturing of ZBLAN optical fibers

ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) is the most stable glass among the Heavy Metal Fluoride (HMF) family and has a wide range of applications in medical industry, telecommunication, IR transmission, among others. But, due to crystal formation while manufacturing of ZBLAN fiber its theoretical minimum loss has not been achieved yet. Some techniques such as high cooling rate and microgravity conditions have been utilized to reduce the crystal formation but are challenging to implement during manufacturing of these fibers. Alternatively, magnetic field (MF), also a body force like gravity, is expected to influence the crystal formation mechanism and glass kinetics. In this work, ZBLAN glass is processed under magnetic fields of various intensities while simulating fiber drawing manufacturing process conditions. Then, the processed ZBLAN is analyzed using Differential Scanning Calorimetry (DSC) at varying scanning rates. Various glass kinetics parameters such as activation energy, fragility, and preferred crystallization mechanism in terms of Avrami parameter (n) have been analyzed. The glass transition temperature (Tg) increases for a given sample as scanning rate (β) increases. Samples processed under varying magnetic fields, at the same scanning rate, displayed higher glass transition temperatures. Also, when the magnetic field increases, the activation energy required for glass transition decreases, and the fragility index (m) decreases. There is also a preference for surface crystallization over volume crystallization. These results encourage application of magnetic fields for reducing crystal formation while processing ZBLAN glass.

Exploring the mechanisms of benzanilide crystal growth and morphology: Crystal surface structure, solvent diffusion and solvent-interface interactions

Flaky crystals are fragile, rendering them unsuitable for various applications including use, processing, storage and transportation. This work investigates the growth and morphology regulation mechanisms of flaky crystals using benzanilide as a model material. Initially, block-like crystals are prepared by solvent screening and cooling crystallization with its morphology greatly improved. Subsequently, growth kinetics of (111), (1–10) and (020) faces are established with crystal growth experiments. The crystal growth of (001) face is also determined to follow a two-dimensional nucleation model with the microscopic surface analysis using atomic force microscopy. The changes of the surface integration resistance and the growth step height are regarded as kinetic mechanisms of the growth behavior and crystal morphology modulation by solvent and supersaturation. Finally, the molecular mechanism of the modulation of the solvent in crystal morphology is revealed base on crystal surface structure analysis and molecular dynamics simulations. The weak solvent-interface polar interactions facilitate the incorporation of benzanilide molecules into the weak polarity (001) face, leading to the surface roughening and increased crystal thickness when employing strongly polar solvents such as acetonitrile. Unlike the former, the relatively weak hydrogen bonding interactions between solvents and strong polarity (020) face, and the higher diffusion ability of molecules promote the rapid growth and disappearance of (020) face in ethanol and acetonitrile with strong hydrogen bond formation ability. This study can contribute to a deeper understanding of the solvent effect on crystal morphology and provide guidance for optimizing crystallization conditions to obtain shape-tailored crystal products.

Exploring the mechanisms of enhanced piezoelectric properties in (K,Na)NbO3 single crystals

(K,Na)NbO3 (KNN)-based piezoelectric materials are candidates for replacing Pb-based materials. However, the piezoelectric properties of existing KNN-based single crystals are still inferior to those of Pb-based relaxor ferroelectric single crystals. Moreover, the piezoelectric response mechanism of KNN-based single crystals remains unclear. In this study, (Li,K,Na)(Nb,Sb,Ta)O3:Mn (KNNLST:Mn) single crystals with an excellent piezoelectric coefficient d33 of approximately 778 pC/N were prepared. Systematically studies of intrinsic and extrinsic piezoelectric responses have revealed that the high d33 of KNNLST:Mn single crystals is related to the shear piezoelectric response of a single-domain state and irreversible domain wall motion of the engineering domains. Furthermore, the effect of the orthorhombic (O)-tetragonal (T) phase boundary on intrinsic and extrinsic piezoelectric response is systematically studied, and the impact mechanism is elucidated. The results indicate that a lower dielectric response and elastic constant limit the intrinsic shear piezoelectric response of KNNLST:Mn single crystals, and approaching the O–T phase boundary can enhance both intrinsic and extrinsic piezoelectric responses. This study improves our understanding of the structure-performance relationship in KNN-based single crystals and offers insights for optimizing piezoelectric properties in KNN-based materials.

Damage and removal behaviors of indium phosphide crystals involved in ultrasonic vibration-assisted AFM machining

Indium phosphide (InP) crystals exhibit a propensity for brittle damage during machining, categorizing them as challenging materials due to their inherent brittleness and pronounced anisotropy. Atomic force microscopy (AFM) machining serves as a crucial approach for achieving low-damage removal of such brittle crystals. Molecular dynamics simulations were conducted to investigate the vibration-assisted AFM machining of InP crystals, systematically exploring the effects of scratching force, stress distribution, and subsurface damage. The findings revealed that plastic deformation of InP crystals during vibration-assisted AFM scratching was primarily governed by mechanisms including stress-induced amorphization transitions, phase transformations, dislocations, stacking faults, and lattice distortions. Compared to conventional AFM machining, vibration-assisted AFM machining had a smaller average contact area and maintained a periodic movement pattern of contact-separation. This induced the change of chip removal from piling up in front of the cutting tool to uniform flow to both sides. Employing appropriate vibration parameters in vibration-assisted AFM significantly diminished the scratching force, stress, dislocation length, and subsurface damage depth. These results not only elucidate the material removal and damage mechanisms of InP crystals at atomic and close-to-atomic scales, but also offer theoretical guidance for parameter optimization in the vibration-assisted AFM machining of other soft and brittle crystals.

Synergetic effect of non-invasive posttreatment agents enables highly efficient and stable all-inorganic Sn-Pb perovskite solar cells

All-inorganic tin–lead perovskites present a promising avenue for achieving an ideal bandgap, approaching the Shockley-Queisser limit, while circumventing the use of volatile organic cations. However, challenges such as relatively low power conversion efficiency (PCE) and rapid degradation dynamics—stemming from complex film crystallization mechanisms and Sn oxidation—hinder their advancement. In this study, we employed sequential interface engineering on the CsPb0.6Sn0.4I3 system, utilizing non-invasive carbazole propylamine bromide and ethylenediamine diiodide as post-treatment agents. This approach significantly enhances both the bulk structure and surface morphology, thereby promoting charge transport, suppressing non-radiative recombination, and improving structural stability. The champion device achieved a PCE of 16.62 % and demonstrated over 2200 h of T80 stability in dry N2. Remarkably, stability in high-humidity environments was validated through device aging tests and in situ GIWAXS analysis. These results underscore the substantial potential of sub-1.4 eV bandgap all-inorganic Sn-Pb perovskite solar cells.