Stages Of Crystal Growth Research Articles

High-Quality SiC Crystal Growth by Temperature Gradient Control at Initial Growth Stage

A modified process condition has been proposed for the growth of high-quality 6-inch 4H-SiC single crystal. Temperature gradient (dT[°C] = Tbottom-Tupper) was controlled by changing coil position in order to investigate the effect of the temperature gradient on the SiC crystal quality. SiC ingot surface and etch pit density (EPD) of etched SiC wafer were investigated according to different dT conditions at the initial stage of SiC crystal growth. The surface of SiC crystal ingots grown with different dT for 10h were observed by OM and etched SiC wafers were prepared from SiC crystal ingots after main growth step for 100h. Different dT conditions in the initial growth stage resulted in dramatically different surface images and the crystal quality evaluated by EPD.

Study on the optimal conductivity titration parameters for SO42- in cement-based materials

Accurately obtaining the SO42- content in concrete is a prerequisite for revealing mechanism of sulfate attack, establishing model of sulfate attack, proposing durability design methods. The feasibility of testing SO42- in cement-based materials by conductivity titration was investigated by the author in previous research. Therefore, this study further investigated the optimal conductivity titration parameters and standard for determining the endpoint of titration curve by establishing a conductivity titration kinetic model (CTKM). Based on the proposed CTKM, optimal range of titration parameters such as the volume of measured solution, solution concentration standard titrant and titration rate were obtained, and the effects of other ions on optimal range of titration parameters were also discussed. The results show that among the six stages on the titration curve of SO42- (undersaturation stage, crystal nucleation stage, crystal growth stage, quasi reaction end stage, reaction end stage and infinite titration stage), crystal growth stage and reaction end stage are essential. The titration curves calculated by the CTKM are in good agreement with the measured curves. The included angle between the left and right tangents of a point on the normalized conductivity titration curve can be a good criterion for determining the titration end point. When the included angle exceeds 10°, the titration end point is easily determined. The optimal range of titration parameters are confined by the minimum measured solution volume to submerge the conductivity electrode (about 5 mL), the maximum measured solution volume to be stirred evenly (about 10 mL), and the appropriate added volume of standard titrant to ensure titration accuracy (between 1 and 1.5 mL), and the included angle to be easily determined (greater than 10°). The influence of H+, OH–, Cl-, and Na+ on SO42- titration gradually weakens. In composite solution containing 0.01 mol/L SO42-, when the concentration of H+ exceeds 0.1 mol/L, or the concentration of OH– exceeds 0.2 mol/L, directly titrating SO42- is difficult and a deionization process is required.

Automatic Control of Nucleation and Crystal Growth Using Online Raman Analyzer

The accurate determination of crystal formation during crystallization is crucial for obtaining crystal products with consistent quality and quantity. In this study, we aimed to identify the feasibility of using Raman spectroscopy to monitor the crystal growth stage in the crystallization process using cephalosporin intermediate 7-ACT as an example molecule. By observing the changes in the characteristic peak of the 7-ACT crystal (504 cm−1) and the characteristic peak of the solvent acetonitrile (914 cm−1), a correlation between the crystal growth stage and the change in the Raman intensity of the crystal solution was discovered. The determination of the optimal starting time for the crystal growth stage through a Raman analyzer significantly improves the consistency of crystal product quality. This led to a fivefold reduction in the variation in the weight and water content of the final 7-ACT crystal products compared to those obtained via manual control. In addition, our experiments also indicated that Raman monitoring could be more efficient at enabling the chemical synthesis reaction to be completed compared to manual control. Thus, our work demonstrates the potential of Raman spectroscopy in the real-time control of chemical synthesis reactions and crystallization processes.

Mechanism underlying effects of CaO-MgO combined expansive agent on hydration kinetics of cement-based systems

With the order of better understanding the early hydration process and reaction mechanism of CaO-MgO combined expansion agent-involved cement-based systems (CMEA-CBS), CMEA dosage, CaO to MgO ratio (Ca/Mg), MgO activity, hydration temperature, and water-binder ratios (w/b) were chosen as the influencing factor. Accordingly, isothermal calorimetry was implemented to analyze the hydration heat release law, and the Krstulovic–Dabic model was applied to investigate the hydration kinetic. Moreover, the activation energy of CMEA-CBS was calculated. The findings of this study are as follows. The incorporation of CMEA can accelerate the hydration of cementitious systems. Hydration temperature increase markedly promote the hydration reaction of CMEA-CBS. The hydration reaction of CMEA-CBS is a complex associated reaction process dominated by multiple reaction mechanisms in sequence. At both 20 °C and 45 °C, the hydration process of CMEA-involved cement-based systems experienced three stages of crystallization nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D), and the hydration mechanism was NG → I → D. However, the hydration of CMEA-CBS at 65 °C switched from the NG stage to the D stage directly. The hydration promotion effect of increasing temperature on I and D process of CMEA-CBS is less than I and D process of pure cement. Compared to the other groups, the temperature increase had the least effect on the early hydration process of 10%-C1M1-M-0.4 with the lowest apparent activation energy.

Synthesis of layered double hydroxides: Investigating the impact of stirring conditions and reactor design parameters

The synthesis by coprecipitation of Layered Double Hydroxides (LDHs) is governed by the stages of nucleation and crystal growth associated with the efficiency of the mixing and dispersion process of the reagents. Mixing efficiency is related to process variables, such as agitation speed, type of impeller and baffles presence, among others. In this context, this work proposes an analysis of these variables in a batch reactor, using a 23 factorial design employing the factors: acceleration speed (200 and 1000 rpm), mixing time (2 and 18 h) and presence or absence of baffles. The results were evaluated quantitatively (amount of LDH produced, time and amount of base for the formation of LDHs to begin) and qualitatively (mixing aspects, sedimentation ad grinding). The significant factors affecting the amount of LDH produced (51.94–80.81 g) were agitation speed and aging time. These factors were also correlated with the structural characteristics of the materials produced, such as crystallinity, crystallite size (70.99–174.79 nm), surface area (69.81–97.62 m2/g), pore volume (0.28–0.59 cm3/g), and pore diameter (11.40–34.66 nm). LDHs produced at higher agitation rates (1000 rpm) and longer aging times (18 h) yielded higher quantities of materials (80.81 g) with improved structural characteristics. The study highlights the importance of systematically exploring the synergistic effect between process variables, emphasizing the research potential in this area.

Determination of the process effect on cocoa butter crystallization by rheometer: Kinetic modeling by Gompertz equation.

In this study, the effects of temperature (22, 24, 26, 28, and 30°C) and strain (0.1%, 1%, and 5%) on cocoa butter (CB) crystallization were investigated by oscillatory test, and the four-parameter Gompertz model was used to interpret the effect of parameters on pre-crystallization, nucleation, and crystal growth stages of CB. Lag time and growth rate were calculated using the Gompertz model using time-dependent storage modulus (G') data. According to the results, CB crystallization at 26°C with a 1% strain value had the highest growth rate value, the shortest lag time, and the formation of βv polymorph type. Followingly, polymorphic types of the CB crystals were determined based on the melting points of polymorphs via the temperature ramp step, and the results obtained were correlated with a polarized light microscope. In conclusion, using a rheometer in both the observation of the pre-crystallization process and the determination of polymorph types is very important for research and development studies in the chocolate industry for process and formulation optimization. PRACTICAL APPLICATION: This study demonstrates the feasibility of a novel approach for investigating crystallization and oscillatory shear of CB using a rheometer, both for observing crystallization kinetics and determining polymorph type, accompanied by the Gompertz equation to model the crystallization kinetics. According to the results, the effect of process parameters (temperature and shear) on the crystallization behavior of CB can be observed by rheometer, which can provide a detailed perspective for chocolate manufacturers and researchers in research and development studies.

Controlling Nucleation and Crystallization of CsPbI3 Perovskites for Efficient Inverted Solar Cells.

The unfavorable morphology and high crystallization temperature (Tc) of inorganic perovskites pose a significant challenge to their widespread application in photovoltaics. In this study, an effective approach is proposed to enhance the morphology of cesium lead triiodide (CsPbI3) while lowering its Tc. By introducing dimethylammonium acetate into the perovskite precursor solution, a rapid nucleation stage is facilitated, and significantly enhances the crystal growth of the intermediate phase at low annealing temperatures, followed by a slow crystal growth stage at higher annealing temperatures. This results in a uniform and dense morphology in CsPbI3 perovskite films with enhanced crystallinity, simultaneously reducing the Tc from 200 to 150°C. Applying this approach in positive-intrinsic-negative (p-i-n) inverted cells yields a high power conversion efficiency of 19.23%. Importantly, these cells exhibit significantly enhanced stability, even under stress at 85°C.

Hydration characteristics and pollutant solidification mechanism of full solid waste electrolytic manganese residue super sulfate cement

In this study, electrolytic manganese residue (EMR) rich in soluble manganese, ammonia nitrogen, and sulfate was combined with carbide slag (CS) and granulated blast furnace slag (GBFS) to produce Full Solid Waste Electrolytic Manganese Residue Super Sulfate Cement (FWS-EMR-SSC). The compressive strength, hydration mechanism, microstructure, hydration kinetics, and pollutant solidification mechanism of FWS-EMR-SSC were investigated. The study revealed that the optimal ratio was 4% carbide slag, 40% EMR, and 56% GBFS, achieving a compressive strength of 38.34 MPa at 28 days. This was due to the release of OH- from carbide slag, causing EMR to dissolve large amounts of SO42- and Ca2+, while GBFS accelerated the release of Ca2+, Si2+, Al3+, leading to the formation of abundant AFt and C-(A)-S-H gel, providing strength to FWS-EMR-SSC. The heat release rate and cumulative heat of the FWS-EMR-SSC system were lower than Ordinary Portland Cement (OPC). Additionally, compared to OPC, the second exothermic peak rate was significantly reduced and delayed in the FWS-EMR-SSC system due to the exothermic release of gypsum, retarding effects, and pronounced generation of AFt. The simulation of FWS-EMR-SSC hydration kinetics using the Krstulović-Dabić model revealed that FWS-EMR-SSC underwent the NG-I-D process. Gypsum retarded the nucleation and crystal growth stages of NG, while AFt had a significant impact on the D diffusion stage. The C-(A)-S-H, AFt gel, and iron-manganese compounds (Fe2Mn(PO4)2(OH)2·(H2O)8, MnFe2O4) generated in the FWS-EMR-SSC system could undergo ion exchange and chemical precipitation with Mn2+. Meanwhile, NH3-N transformed into NH3 release, ensuring that the leaching toxicity of FWS-EMR-SSC met the Chinese standard limits of GB8978-1996 for wastewater discharge.

Chemodynamic PtMn Nanocubes for Effective Photothermal ROS Storm a Key Anti-Tumor Therapy in-vivo.

Chemodynamic therapy (CDT) is a new treatment approach that is triggered by endogenous stimuli in specific intracellular conditions for generating hydroxyl radicals. However, the efficiency of CDT is severely limited by Fenton reaction agents and harsh reaction conditions. Bimetallic PtMn nanocubes were rationally designed and simply synthesized through a one-step high-temperature pyrolysis process by controlling both the nucleation process and the subsequent crystal growth stage. The polyethylene glycol was modified to enhance biocompatibility. Benefiting from the alloying of Pt nanocubes with Mn doping, the structure of the electron cloud has changed, resulting in different degrees of the shift in electron binding energy, resulting in the increasing of Fenton reaction activity. The PtMn nanocubes could catalyze endogenous hydrogen peroxide to toxic hydroxyl radicals in mild acid. Meanwhile, the intrinsic glutathione (GSH) depletion activity of PtMn nanocubes consumed GSH with the assistance of Mn3+/Mn2+. Upon 808 nm laser irradiation, mild temperature due to the surface plasmon resonance effect of Pt metal can also enhance the Fenton reaction. PtMn nanocubes can not only destroy the antioxidant system via efficient reactive oxygen species generation and continuous GSH consumption but also propose the photothermal effect of noble metal for enhanced Fenton reaction activity.

Reversible evolution phenomenon of particle during crystal growth: A phase-field study

The two-dimensional thermodynamically consistent phase field model, which consists of the anisotropic Allen-Cahn type equation and the heat equation, is used to study the morphological pattern of the particle in the initial stage of crystal growth. The results reveal the locally reversible growth of the particle in the initial stage of crystal growth. Specifically, some parts of the particle interface first grow inward, while others grow outward from the interface of critical nucleation, until the growth speed of the interface becomes zero. After this, the inward growth parts start to grow outward with other parts. The locally reversible growth of the particle leads to the development of a petal-like shape. The particle radius size dependence of the temperatures along the parts of the particle interface in different crystallographic directions at different time points is studied. By a series of results, the correlations between the morphological pattern selection of the particle and the model parameters, including undercooling and anisotropic strength, are analyzed. These results contribute to understanding the fundamental mechanism of the particle evolution during crystal growth.

Early-age properties of cement paste with mechanically ground Yellow River sediment

Yellow River sediment(YRS) is a rich, low-activity silica-aluminum dredged sediment resource, which can provide a new source of supplementary cementitious materials(SCMS). This study investigated the influence of mechanically ground Yellow River sediments (MGYRS) on the hydration kinetics and early-age shrinkage of cement paste. Hydration kinetics revealed that MGYRS could significantly accelerate the hydration process, proceeding directly from the nucleation and crystal growth stage (NG) to the diffusion stage (D). In the plastic stage of cement paste, the early-age shrinkage of MGYRS at 40 min and 70 min increased by 250 µm/m and 99 µm/m, respectively. Microscopic analysis showed that MGYRS could promote the generation of Ca(OH)2, and the nucleation, micro-aggregate filling effect of MGYRS could refine the pore structure. This study can provide theoretical support for realizing the gelatinization of YRS.

Synchrotron X-Ray Topography Studies for Defect Formation at the Early Stage of PVT-Grown 4H-SiC Crystals

Silicon Carbide (SiC), typically 4H-SiC, is replacing conventional silicon materials for high power and high frequency applications due to its excellent electrical and thermal properties [1]. However, high quality SiC wafers with low defect density are still in urgent need for automotive and energy saving applications. SiC wafers are obtained from bulk growth by physical vapor transport (PVT) method and considerable efforts have been expended to optimize growth process to lower defect densities. One major approach is the study of initial stages of crystal growth as most defects are nucleated at this stage and propagate into the boule. Ailihumaer et al [2] demonstrated the behaviors of threading edge dislocations (TEDs), threading screw dislocations (TSDs)/threading mixed dislocations (TMDs), and basal plane dislocations (BPDs) across the seed/newly grown layer interface in PVT-grown 4H-SiC. Sanchez et al [3] revealed the nucleation of TEDs and TSDs at the initial growth stage in PVT-grown SiC.However, more detailed investigations are still in demand for PVT grown 4H-SiC crystals during initial stage of growth. This study investigates 4° off-axis 4H-SiC wafers with several hundred microns of initial-stage growth PVT method. Synchrotron X-ray topography (SXRT) technique is employed and shows dramatically modified defect distribution across the seed/newly grown layer interface (Figure 1). The formation of Shockley stacking fault starting at initial stage of crystal growth is suggested as partial dislocations running along <11-20> directions on basal plane are observed to form rhombus shapes (Figure 2). Prismatic slip is observed to take place near the wafer edges and prismatic dislocations undergo cross slip to form unique dislocation configurations. A statistical analysis on defect changes across the seed/newly grown layer is being carried out and the results will be reported. These results will be complemented by observations from Nomarski optical microscopy (NOM) and Raman Spectroscopy studies to propose the formation mechanism of defects across the seed/newly grown layers.

Wollastonite-containing glass-ceramics from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 ternary systems

Glass-ceramics (GCs) are polycrystalline materials produced from parent glasses by the controlled crystallization that results in crystalline phase(s) embedded in a residual amorphous matrix. Typically, GCs are produced by a conventional glass route with subsequent crystallization for which two heat treatments are usually applied, the former to generate nuclei and the latter being a crystal growth stage. Alternatively, another technically viable route for manufacturing GCs involves sintering of glass-powder compacts followed by crystallization (sinter-crystallization).Wollastonite-containing GCs from the CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems find a wide variety of uses in different technological fields, including construction, architecture, medical and high-tech fields. For example, a special type of wollastonite-containing GC marketed under the name of Neoparies®, which is stronger and lighter than natural stone, features high resistance to weathering/chemical attack and is manufactured on a large scale for construction and architectural applications. In the biomedical field, the well-known Cerabone® products have been used in bone-contact applications for many years.The main goal of this brief review is to provide a critical analysis of the experimental trials focusing on the synthesis of wollastonite-containing GC materials and to discuss the various fields of their application. Constitution of phase diagram of CaO–Al2O3–SiO2 and CaO–MgO–SiO2 systems are comprehensively discussed with connection to melt crystallization path and crystalline phase formation. Furthermore, special emphasis will be given to the production of wollastonite-containing GCs for construction and architectural purposes from natural raw materials and wastes, as well as to the recent advancement in developing wollastonite-containing GC biomaterials for bone repair.

Design of follow-up superconducting Cusp magnetic field and system performance analysis of Czochralski single crystal furnace

This paper proposes a magnetic system structure for a single crystal furnace that addresses the issue of unreasonable distribution of magnetic field lines on the free surface caused by DHL (Distance between the lower edge of the heat shield and the liquid surface) fluctuation during early stages of crystal growth. The proposed structure adjusts with the fluctuation of the free surface during the crystal pulling process, enabling the magnetic system to positively impact the thermal system. The thermo-magnetic coupling in a 160-type single crystal furnace before and after magnetic system optimization was simulated using the finite element method. Numerical simulation was employed to compare the temperature gradient, S-L (solid–liquid) boundary temperature distribution, and radial oxygen content in the single crystal furnace before and after magnetic system optimization under the conditions of Cr (crystal rotation) and Gr (graphite crucible rotation). The results reveal that the optimized magnetic system helps adjust the shape of the S-L boundary, decrease the temperature gradient, and lower the oxygen levels at the S-L boundary. However, when the Gr is rotated at high speed, although the S-L interface becomes flatter, the temperature gradient and oxygen concentration at the boundary increase. On the other hand, When Cr is at high speed, the S-L boundary tends to become flatter and the temperature gradient at this boundary decreases, but the oxygen concentration at the S-L boundary increases. Compared to the original single crystal furnace with a fixed magnetic system, the single crystal furnace with a lifting magnetic system experiences a 6.34% reduction in radial temperature gradient and a 3.02% reduction in axial temperature gradient during the actual crystal pulling process parameters. The temperature gradient at the S-L boundary decreases by 36.50%, and the radial average oxygen concentration decreases by 26.58%. Furthermore, the temperature distribution of the crystal and melt becomes more uniform, the oxygen content at the S-L boundary is effectively controlled, and the overall crystal quality improves. These findings can serve as a reference for designing a new magnetic system for a single crystal furnace.

Reappraising Crystallization Kinetics with Overgrowth Chronometry: an in Situ Study of Olivine Growth Velocities

Abstract We investigated the early stages of olivine crystal growth via in situ seeded experiments in a single plagioclase-hosted melt inclusion, using a heating stage microscope. Each experiment was subjected to a cooling ramp of 7800°C/h followed by an isothermal dwell at 19°C, 38°C, 57°C, 77°C, 96°C or 129°C of undercooling. The seeds (6–16 μm in diameter Ø) grew into large crystals (Ø 80–169 μm) in 3 to 30 min through the symmetrical development of tabular, skeletal, and dendritic overgrowths as the undercooling of the system increased. Time-resolved image processing and incremental measurements of the overgrowth thicknesses indicate up to three stages of crystal growth: an acceleration stage, a linear (constant growth rate) stage, and a deceleration stage. At the isotherm, the growth velocities reach a stable maximum that in all experiments corresponds to the period of linear growth. The highest linear values are measured at the $\left\{101\right\}$ interfaces, from 2.1 × 10−8 m/s at 19°C of undercooling to 4.8 × 10−7 m/s at 129°C of undercooling. Crystal growth is slower at other interfaces, in the ranges 1.9–7.6 × 10−8 m/s and 4.5 × 10−9 – 7.6 × 10−8 m/s for the $\left\{100\right\}$ and $\left\{001\right\}$ forms, respectively. Growth in the $&amp;lt;010&amp;gt;$ dimension appears limited to less than 2.4 × 10−8 m/s at 129°C of undercooling. We constrain the uncertainty on these growth velocities, which includes the environmental conditions (± 8.6°C on the nominal undercooling) and the measurements of crystal lengths (underestimated by &amp;lt;16% at most fast interfaces). A systematic and comprehensive review of 19 pre-existing datasets indicates that our linear growth velocities are faster than most growth rates determined at comparable undercoolings. Growth rates determined as half crystal lengths divided by total time are intrinsically low estimates of the true maximum, linear growth velocities, because the total time includes periods of slower or non-growth, and measured crystal dimensions are subject to projection foreshortening or truncation. These errors can lead to values that are several times to several orders of magnitude lower than the true maximum growth rates. This study completes and refines previously published data on the crystallization kinetics of olivine, highlighting the sensitivity of growth rates to specific environmental conditions and measurement methods. We emphasize the importance of symmetrical growth and true maximum growth velocities for interpreting olivine growth histories.

Amodal segmentation of cane sugar crystal via deep neural networks

The growth of cane sugar crystals can provide fundamental information for the setting of production process parameters. However, the overlap phenomenon of sugar particles has adverse effects on identifying the shape of sugarcane crystals in images, and it is critical to effectively recognize the status of the growth of cane sugar crystals. To realize the recognition and segmentation of three cane sugar crystal states, we propose ASSugarNet, a cane sugar crystal amodal segmentation method based on deep neural networks. To better extract multi-scale semantic features, the local feature enhance module is proposed. The foreground boundary enhancement loss function is adopted, which can effectively improve the segmentation quality of sugar crystal boundary regions. For overlapping crystals, the amodal segmentation module is used to predict the contours and masks of the occluded sugar crystals, which provides accurate input for the subsequent sugar crystal growth stage judgment. To verify the network performance, we create a dataset of cane sugar crystals. Compared with FCN, PSPNet and U-Net 3 + network, the experimental results show that the proposed network structure has better segmentation for three types of crystal performance, with MIoU of 81.47% and OA of 91.00%. The AP of ASSugarNet for adhesive particle segmentation is 32.25%, and the AP50 is 52.14%.

The Interaction Between Interface Morphology of Particles with Anisotropic Effect of Interface Kinetics in an Alloy Melt

AbstractThe conventional theory of crystal growth presents an irreversible outward increase of the crystal size through solute deposition on the nuclei; however, the asymptotic solution of the dynamics model of the particle reveals that the crystal growth undergoes a locally reversible inward growth process in the early stage of crystal growth. Immediately after nucleation, some parts of the interface first grow inward through solute rejection along certain crystal orientations from the interface of nucleation, while the other parts of the interface grow outward through solute deposition along other crystal orientations. Until the inward growth attains a certain distance, the interface grows outward along each crystal orientation. This growth behavior is attributed to the interaction between interface morphology of particles with the anisotropic effect of interface kinetics. Through a systematic variation of the anisotropy parameters, the particle exhibits a continuous transition from one growth morphology to other growth morphologies. During the morphological transition process, as initial concentration increases, the growth of the particle is inhibited in the preferred growth directions, whereas it is facilitated in other growth directions. As a result, the interface morphologies of the particle with different petal‐shaped morphologies in the early stage of crystal growth are formed.

Study on the Effect of Polycarboxylate Ether Molecular Structure on Slurry Dispersion, Adsorption, and Microstructure.

This study synthesized polycarboxylate superplasticizer (PCE) with varying carboxyl densities and main chain degrees of polymerization. The structural parameters of PCE were characterized using gel permeation chromatography and infrared spectroscopy. The study investigated the impact of PCE's diverse microstructures on cement slurry's adsorption, rheology, hydration heat, and kinetics. Microscopy was used to analyze the products' morphology. The findings indicated that an increase in carboxyl density led to an increase in molecular weight and hydrodynamic radius. A carboxyl density of 3.5 resulted in the highest flowability of cement slurry and the most considerable adsorption amount. However, the adsorption effect weakened when the carboxyl density was the highest. Decreasing the main chain degree of polymerization led to a significant reduction in the molecular weight and hydrodynamic radius. A main chain degree of 16.46 resulted in the highest flowability of slurry, and both large and small main chain degrees of polymerization exhibited single-layer adsorption. PCE samples with higher carboxyl density caused the greatest delay in the induction period, whereas PCE-3 promoted the hydration period's acceleration. Hydration kinetics model analysis indicated that PCE-4 yielded needle-shaped hydration products with a small nucleation number in the crystal nucleation and growth stage, while PCE-7's nucleation was most influenced by ion concentration. The addition of PCE improved the hydration degree after three days and facilitated the strength's later development compared to the blank sample.

Controlling crystallization: what liquid structure and dynamics reveal about crystal nucleation mechanisms.

Over recent years, molecular simulations have provided invaluable insights into the microscopic processes governing the initial stages of crystal nucleation and growth. A key aspect that has been observed in many different systems is the formation of precursors in the supercooled liquid that precedes the emergence of crystalline nuclei. The structural and dynamical properties of these precursors determine to a large extent the nucleation probability as well as the formation of specific polymorphs. This novel microscopic view on nucleation mechanisms has further implications for our understanding of the nucleating ability and polymorph selectivity of nucleating agents, as these appear to be strongly linked to their ability in modifying structural and dynamical characteristics of the supercooled liquid, namely liquid heterogeneity. In this perspective, we highlight recent progress in exploring the connection between liquid heterogeneity and crystallization, including the effects of templates, and the potential impact for controlling crystallization processes. This article is part of a discussion meeting issue 'Supercomputing simulations of advanced materials'.

Effect of Hydrophobic Moieties on the Assembly of Silica Particles into Colloidal Crystals

To boost the implementation of colloidal crystals (CCs) in separation science, the effects of the most common chromatographic reversed phases, that is, butyl and octadecyl, on the assembly of silica particles into CCs and on the optical properties of CCs are investigated. Interestingly, particle surface modification can cause phase separation during sedimentation because the assembly is highly sensitive to minute changes in surface characteristics. Solvent-induced surface charge generation through acid-base interactions of acidic residual silanol groups with the solvent is enough to promote colloidal crystallization of modified silica particles. In addition, solvation forces at small interparticle distances are also involved in colloidal assembly. The characterization of CCs formed during sedimentation or via evaporative assembly revealed that C4 particles can form CCs more easily than C18 particles because of their low hydrophobicity; the latter can only form CCs in tetrahydrofuran when C18 chains with a high bonding density have extra hydroxyl side groups. These groups can only be hydrolyzed from trifunctional octadecyl silane but not from a monofunctional one. Moreover, after evaporative assembly, CCs formed from particles with different surface moieties exhibit different lattice spacings because their surface hydrophobicity and chemical heterogeneity can modulate interparticle interactions during the two main stages of assembly: the wet stage of crystal growth and the late stage of nano dewetting (evaporation of interparticle solvent bridges). Finally, short, alkyl-modified CCs were effectively assembled inside silica capillaries with a 100 μm inner diameter, laying the foundation for future chromatographic separation using capillary columns.