•The crystal morphology of sucralose was precisely simulated via the MAE model.•Roughness and solvent-crystal contacting angle are vital for solvent adsorption.•The solvent-crystal interactions are ...dominated by strong hydrogen bonds.•Different inhibitory degree of solvents on two faces arouses varied aspect ratios.
The effect of solvents on sucralose crystal morphology was studied both experimentally and theoretically in water, methanol and ethanol. Hirshfeld surfaces and 2-D fingerprint plots were used to investigate the solute-solute interactions which were involved in the calculation of crystal morphology in vacuum. Moreover, solvent-crystal interactions were considered by using the modified attachment energy model and molecular dynamics simulation, leading to a precise simulation of sucralose crystal morphology in all the three solvents. In order to have a better understanding of the solvent effect, surface structure as well as the strength and the type of the solvent-crystal interactions on the morphologically important faces including the (0 1 1) and (1 0 1) faces were discussed. Both surface roughness and solvent-crystal contacting angle were found to be important to the effective solvent adsorption. Based on the diffusion coefficient of solvent molecules on the crystal faces, the crystal morphology of sucralose was also affected by the solvent diffusion. Radial distribution function analysis showed strong hydrogen bonds between the hydrogen atoms in the solutes and the oxygen atoms in the solvents on the (0 1 1) and (1 0 1) faces. Furthermore, different inhibitory degrees of the solvents on the two faces can cause varied aspect ratios of crystals in the tested three solvents.
The components of bone assemble hierarchically to provide stiffness and toughness. However, the organization and relationship between bone's principal components-mineral and collagen-has not been ...clearly elucidated. Using three-dimensional electron tomography imaging and high-resolution two-dimensional electron microscopy, we demonstrate that bone mineral is hierarchically assembled beginning at the nanoscale: Needle-shaped mineral units merge laterally to form platelets, and these are further organized into stacks of roughly parallel platelets. These stacks coalesce into aggregates that exceed the lateral dimensions of the collagen fibrils and span adjacent fibrils as continuous, cross-fibrillar mineralization. On the basis of these observations, we present a structural model of hierarchy and continuity for the mineral phase, which contributes to the structural integrity of bone.
Carbon capture and storage (CCS) is a critical approach to reducing atmospheric carbon emissions. The United Nations UN Climate Change Conference COP26 Glasgow 2021 emphasized setting execution plans ...to reach the goal of a zero-carbon economy by 2050 as per the Paris Agreement 2015. CO2 sequestration in deep-sea sediments in the form of clathrate hydrates is a promising technique as it provides a significant capacity for CO2 storage. Deep-sea sediments contain high salinity water, which will impair the CO2 storage capacity and hydrate stability. Therefore, it's essential to examine the effect of salinity on CO2 hydrate stability in simulated deep-sea sediments to foster real-time field application.
In this first-gen experimental work, the stability of CO2 hydrates across and inside the deep oceanic saline sediments has been evaluated for an extended period 14 days. An artificial seabed, saturated with saline solution 3.5 wt% NaCl, was created using silica sand inside a high-pressure reactor system and stability tests were conducted at oceanic conditions (10 MPa, 4 °C). In phase 1, CO2 hydrates were formed across the seabed by pressurizing the system multiple times to 3.5 MPa using pure CO2 gas. In phase 2, the hydrates were immersed in a brine solution 3.5 wt% NaCl and their stability was observed over 2 weeks >14 days. The experimental results indicate that CO2 hydrates are adequately stable when submerged inside the brine solution and layers of hydrates were visible at the end of 2 weeks of the stability experiment. In phase 3, a hybrid depressurization heating approach was used at the end of the stability test to confirm the presence of a good quantity of CO2 hydrates inside the sand bed.
Display omitted
•CO2 hydrate formation kinetics in deep-oceanic sediments saturated in brine.•CO2 hydrate formation morphology in oceanic sediments saturated in brine.•CO2 hydrates stability evaluated in deep-ocean sediments submerged in brine.
The annealing of sputtered AlN films with different thicknesses grown on sapphire in nitrogen ambient was investigated. In the annealing, two AlN films on sapphire were overlapped “face-to-face” to ...suppress the thermal decomposition of the AlN films. The sputtered AlN films with small grains consisted of columnar structure were initially aligned with (0002) orientation but became slightly inclined with increasing film thickness resulting in the formation of a two-layer structure. After annealing, films became a single crystalline layer regardless of the film thickness, and their crystallinity markedly improved after annealing at 1600–1700°C. The full widths at half maximum of the (0002)- and (101¯2)-plane X-ray rocking curves were improved to 49 and 287 arcsec, respectively, owing to the annihilation of domain boundaries in the sputtered AlN films, which concurrently increased the compressive stress in the films.
•The “face-to-face” annealing of sputtered AlN films on sapphire in nitrogen ambient was investigated.•Crystallinity of annealed AlN films markedly improved after annealing at 1600–1700°C.•The FWHM of the (0002)- and (102)-plane X-ray rocking curves were improved to 49 and 287″, respectively.
•MD simulation was used to study the effect of solution conditions on β-HMX habit.•The effect of model dimension was studied, and a reasonable model size was obtained.•All the simulation results have ...a good agreement with the experimental results.
To research the influence of solution conditions on β-HMX crystal morphology in acetone-ethyl acetate-water ternary system, attachment energy (AE) model was adopted to simulate the morphology of β-HMX with the water mass fraction of 5%, 10%, 15% and 20% respectively. In acetone-ethyl acetate-water ternary system, the ratio of acetone and ethyl acetate was fixed on 4:3. Moreover, the effects of different temperatures and supersaturations on β-HMX morphology in acetone-ethyl acetate-water ternary system (5% water) were also examined. In addition, the influence of model dimension on the attachment energy was studied, and a reasonable model size was obtained. The simulated results reveal that the difference of water ratio, temperature and supersaturation can affect β-HMX morphology. The simulation results will provide some guidance for the crystallization process of β-HMX.
•A chemo-mechanical strategy for forming crystals.•Crystal structure is chemo-mechanically controlled in a gel environment.•Mg2+ and confinement yield magnesium calcite crystals with “fried egg” ...shapes and spherulitic structures.•The fried eggs result from spherulitic growth molded at the gel-glass interface.•No fried eggs without nucleation on the glass and interfacial adhesion between the glass and gel.
The production of synthetic crystals with controlled shapes and properties is an enticing prospect, yet, the production of such materials is an ongoing challenge. Here, we present a strategy for chemo-mechanically directing the growth of crystals with non-equilibrium structures using a custom-designed double-diffusion cell. We combine chemical additives (e.g., Mg2+ ions) and mechanical confinement (e.g., hydrogel networks) to modulate the growth of calcium carbonate crystals. Specifically, the combination of Mg2+ ions with a strong agarose gel results in calcitic structures, at the gel-glass slide interface, with distinct fried egg-like morphologies and radial or Maltese-cross extinction patterns. In contrast, precipitation with only Mg2+ or agarose results in aragonite spherulites or squished calcite rhombohedra, respectively. Raman spectroscopy and energy dispersive spectroscopy of the “fried eggs” reveals that they are composed of Mg-calcite, which becomes less disordered over time, and the “egg whites” make this transition before the “yolks”. We propose that the “fried eggs” form due to a spherulitic growth process molded by the crystallization-induced delamination of the gel away from the glass slide at the gel-glass interface. In support of the importance of the gel-glass interface, the “fried eggs” do not form when the glass slide is treated with a hydrophobic silane, suppressing heterogeneous nucleation and weakening the interfacial adhesion between the gel and glass, making it easier for the gel to delaminate, thus reducing the confinement effect. As such, this work highlights the important chemo-mechanical role that gel environments can play in crystal formation.
•Behavior of primary dendrite arm spacing is investigated by the phase-field method.•Effect of grain boundaries, pulling speed and inclination angle are investigated.•Unique value of spacing is ...formed by the branching occurred at grain boundary.
The steady-state value of primary dendrite arm spacing (PDAS) in the columnar dendrites growing between the converging and diverging grain boundaries is investigated by means of quantitative phase-field simulations. The simulations show that there is a unique value of PDAS under a given solidification condition in the system with grain boundaries. This is in contrast to existence of allowable range of PDAS under a given solidification in a system without the grain boundaries, i.e., an infinitely large columnar grain investigated in many early works. Such a unique value of PDAS depends on the pulling speed and inclination angle of the crystal, but not on the initial condition; that is, it is independent of the history of solidification condition. The dependences of the unique value on the pulling speed and inclination angle qualitatively agree with the theoretical models.
Mitigation of crystallization fouling on heat transfer surface is crucial for developing highly efficient desalination techniques, because the tenacious and porous crystal layer can drastically ...deteriorate system efficiency. Surface modification is a potential approach to decrease scale formation and promote crystal removal, but some of the mechanisms between crystallization and substrate properties are still not fully understood. In this study, we use dual-angle microscopic visualization and image processing to quantify three-dimensional crystallization behavior and analyze the impact of surface structure and material. The transition of crystal size and distance with roughness and wettability are identified from statistical analysis. The determination of crystal porosity and effective thermal conductivity is enabled by visualized geometry and measured deposition mass. This study shed lights on potential strategies of surface modification to mitigate scaling in desalination by enhancing scale removal and localizing crystal growth.
•Crystallization behavior regulated by surface micro-structure•Quantitative analysis of crystal morphology•Variation of scale deposition mass with surface properties and temperature
PDF
