Crystal Growth & Design最新文献

Ho-doped Pb(Mg1/3Nb2/3)O₃–PbTiO₃ (Ho-doped PMN–PT) single crystal with a size of φ25 × 25 mm was successfully grown by the Bridgman technique. The [110]-oriented crystal taken from the starting part of the crystal ingot was studied in detail. The Rietveld refinement and room-temperature domain configuration reveal the coexistence of monoclinic (Mc) and tetragonal (T) phases in the studied crystal. Upon heating, the unpoled crystal undergoes a Mc→T→C phase transition process, while the poled crystal undergoes a Mc→O→T→C phase transition process. The dielectric coefficient (ε₃₃/ε₀), piezoelectric constant (d₃₃), and electromechanical coupling factor (k_t) are 5725, 1450 pC/N, and 0.5, respectively, all of which are higher than those of the [110]-oriented PMN–PT single crystal. The coercive field (E_c) is 5.1 kV/cm, approximately twice that of the PMN–PT single crystal. Excellent ε₃₃/ε₀, d₃₃, and k_t are attributed to the denser polar nanoregions induced by Ho doping, which is supported by the relaxor behavior and the dielectric-temperature curve at low temperatures. The increase in E_c is attributed to the coexistence of the Mc and T phases. In addition, Ho doping induces PMN–PT crystals to achieve green light emission under 454 nm excitation. The strongest emission peak is at 552 nm, and extremely high color purity is exhibited. These characteristics make the developed single crystals a promising candidate for optoelectronic intelligent devices.

The batch cooling crystallization of the α polymorphic form of l-glutamic acid from aqueous solution in a kilo-scale 20 L pharmaceutical batch crystallizer is simulated using a multiphase computational fluid dynamics (CFD) model coupled with a one-dimensional population balance equation (PBE). The predicted three-dimensional spatial and temporal distributions of turbulent kinetic energy, supersaturation, nucleation rate, and solid volume fraction provide a high fidelity and very detailed insights into the interplay between crystallizer hydrodynamics and crystallization process kinetics and their resultant impact upon the resulting crystal size distributions (CSDs). Comparison of the CFD-PBE modeling results with published experimental data (Liang, 2002) demonstrates the model’s predictive capability by reproducing the measured final CSDs with an acceptable degree of accuracy. An increase in impeller speed is found to increase both the measured and predicted CSD curves shift toward smaller particles sizes. In terms of the spatial variations of process parameters, the evolution of CSD during the crystallization process reveals significant variation of the evolving CSD at the early stages (between 45 and 40 °C) of the crystallization process, which is relatively invariant in the later stages (between 30 and 20 °C), consistent with the reduction of solution supersaturation within the batch process. The simulation results under different agitation rates reveal that at the higher rates, smaller crystals are produced due to a greater level of turbulence and higher supersaturation at an early stage of the process. Detailed sensitivity analysis on the effect of crystallization kinetics on the predicted CSD emphasizes the need for using reliable kinetic data relevant to the crystallization conditions being simulated.

Phytosterols, and their saturated analogs phytostanols, exist in different hydrated forms known as monohydrate (ca. 4 wt % water), hemihydrate (ca. 2 wt % water), and anhydrate (0 wt % water), all having different properties. In the current research, the solid-state characteristics of phytosterols and phytostanols were studied, with a focus on the hydrate formation and stability. The solid-state analysis was conducted using powder XRD, TGA, DSC, elemental analysis, and SEM. To the best of our knowledge, this is the first time that crystal lattice and unit cell parameters of β-sitostanol have been investigated. Surprisingly, we observed that different hydrate forms can be modified solely by adjusting the drying and storage conditions of the crystals. This implies that the crystallization conditions themselves, especially the solvent system, can be chosen based purely on crystal purity, preferred particle specifications and yield obtained. Anhydrous phytosterols are more stable against atmospheric moisture when stored at ambient conditions compared to anhydrous phytostanols, which absorb moisture remarkably quickly, within as little as an hour. The findings regarding the differences in stability and hygroscopicity tendencies are important aspects for storage and usage of the material in further applications.

We studied the effects of ambient nitrogen (N₂) gas on the growth kinetics of ice crystals. We directly observed individual elementary spiral steps (0.4 nm in height) on prism faces of ice crystals under N₂ gas at 0.20–1.00 atm using our advanced optical microscope (a Laser Confocal Microscope combined with a Differential Interference contrast Microscope: LCM-DIM). We measured the lateral velocity (v_step) of elementary spiral steps on prism faces as a function of supersaturation (σ) of water vapor under N₂ gas at different pressures (P_N2). From the dependence of v_step on σ, we determined the step kinetic coefficient β under different P_N2 and found that with increasing P_N2 from 0.20 to 1.00 atm, β decreases monotonically to approximately one-fourth. In addition, we also determined the step ledge free energy κ of elementary spiral steps from the relation between the spacing of adjacent spiral steps and supersaturation at crystal surfaces. Then, we found that κ shows a small maximum at P_N2 = 0.80 atm, although it is unclear whether this result holds any meaning. We discussed the reasons for the decrease in the surface growth kinetics (β) of ice crystals by considering two cases: when N₂ gas adsorbs or does not.

Limpets of the family Nacellidae construct their shells with an outer prismatic layer, underlain by an acicular-foliated layer, and occasionally an internal crossed-lamellar layer. The outer layer consists of prisms oriented approximately perpendicular to the shell growth surface. At the transition to the acicular-foliated layer, these prisms subdivide into segments that become incorporated into the underlying folia. The folia are extensive, radially oriented, and further subdivided into transverse acicles, hence the term “acicular-foliated”. Crystallographically, the outer prisms are remarkable in having their c-axes oriented at a high angle to their elongation and aligned toward the shell margin, with one a-axis typically perpendicular to the growth surface. The prisms exhibit a high degree of co-orientation, with textures ranging from diffuse to well-organized sheet textures. When considering rhombohedral face orientations, the texture may appear either single- or double-crystal-like. This crystallographic arrangement is inherited by the acicular-foliated layer, where the texture invariably becomes stronger. Such an unusual orientation likely results from oriented nucleation on an organic template, possibly the mantle surface, combined with crystal competition in the direction toward the shell margin. From both morphological and crystallographic perspectives, the prismatic-acicular-foliated microstructural complex of nacellids is unparalleled among molluscs.

Kidney stones contain organic components, including proteins, in addition to inorganic components that constitute crystals. In vitro calcium oxalate crystal growth experiments also confirmed that the proteins were incorporated into the crystals. However, the structural states of proteins in stones and crystals remain unclear. In this study, we focused on protein denaturation and compared the effects of native and denatured proteins on the growth of calcium oxalate crystals. Five model proteins with different secondary structures, molecular weights, and isoelectric properties─bovine serum albumin (BSA), soybean trypsin inhibitor (STI), bovine β-lactoglobulin (BLG), chicken egg lysozyme (HEL), and bovine pancreas α-chymotrypsinogen (BPC)─were selected. These proteins were irreversibly denatured under high-temperature and high-pressure conditions. Denatured BSA, STI, and BLG showed significant changes in crystal shape compared to native proteins, indicating that they inhibited crystal growth. In contrast, denatured HEL and BPC stabilized the metastable phases, although the effect of denaturation on the crystal shape was small. Microscopic observations using fluorescently labeled proteins revealed that the denatured proteins exhibited stronger fluorescence from the surface and within the crystals, indicating that protein denaturation enhanced their binding to calcium oxalate crystals. Thus, the structural state of the proteins contained within the stones must be considered.

The integration of materials can generate synergistic effects, forming the core concept of a new generation of multifunctional applications. In particular, the integration of the ZnO structure with the zeolite imidazolate framework-8 (ZIF-8) has been shown to enhance gas selectivity, which is mainly achieved through the molecular sieving effect of the specific-sized porous structure of ZIF-8. In this work, a room-temperature ammonia (NH₃) gas sensor based on ZnO/ZIF-8 composites was fabricated via a combination of hydrothermal synthesis, templating, and drop-casting methods. By tuning the concentration of 2-methylimidazole, the ZIF-8 content was optimized, and the ZnO/ZIF-8–2 sensor exhibited robust NH₃ sensing performance at room temperature. The sensor exhibited outstanding sensitivity toward NH₃ (150.16@100 ppm), approximately 16 times that of pure ZnO sensor, with a rapid response/recovery time (14.5 s/1.6 s). Furthermore, the sensor showed remarkable selectivity, repeatability, and humidity resistance. This improvement is attributed to the increased content of oxygen vacancies and adsorbed oxygen species, high carrier density, the unique lychee-like morphology and large specific surface area, and the synergistic effect of the ZnO/ZIF-8 heterojunction. This study provides a promising strategy for the efficient detection of NH₃ at room temperature using ZIF-8-based hybrid materials.

4H Silicon carbide (4H–SiC) is the most promising semiconductor for power devices. The performance of the devices is determined by the quality of the 4H–SiC epilayers. Triangle defects are the most prevalent defects in the epilayers. As the epilayer thickness increases, more defects are generated in association with them, further leading to a decrease in device yield. In this work, the formation and evolution mechanism of dislocation piles derived from triangle defects in thick epilayers is investigated. The composition of the 3C silicon carbide (3C–SiC) in the triangle defects was confirmed by Raman spectroscopy. The dislocation piles originate from basal plane dislocation (BPD) segments generated by the mismatch between 3C–SiC and 4H–SiC. Based on X-ray topography (XRT) measurements, it is determined that the dislocation piles consist of interfacial dislocations (IDs), BPDs, and threading dislocations (TDs). The evolution mechanism of dislocation piles was analyzed by three-dimensional (3D) XRT section images, and a model was established. The BPD segments generated by mismatch glide under thermal stress, leaving IDs at the interface between the substrate and the epilayer. The glided BPDs continue to propagate along the basal plane with epitaxial growth and are converted into TDs under the step-flow. TDs propagate perpendicular to the basal plane and reach the surface of the epilayer, leaving growth pits on the surface. This study conducts an in-depth investigation into the formation, evolution, and effects of dislocation piles induced by triangle defects in a thick 4H–SiC epilayer, providing guidance for further improving wafer yield.

Ni and S atoms in the same reaction system are prone to form a mixture composed of various nickel sulfide phases, and the one-step synthesis of α-NiS remains challenging. Herein, glucose was added to the precursor solution for the synthesis of nickel sulfide. With the increase of glucose, Ni and S atoms gradually transformed into α-NiS. Meanwhile, glucose gradually increases the specific surface area of the product, providing more active sites for electrochemical energy storage. The induced phase transition effect provided by glucose is only effective for α-NiS and requires a fixed concentration of reactants, which provides clear guidance for the synthesis of α-NiS. Ni_xS_y-0.5 synthesized with 0.5 g glucose has a large surface area and the highest electrochemical properties. Furthermore, the Ni_xS_y-0.5//activated carbon (AC)–asymmetric supercapacitor (ASC) has an energy density of 47.9 Wh kg^–1. This work has established a crystal phase structure regulation strategy for nickel sulfide, which is conducive to the synthesis of transition metal sulfides with high electrochemical performance.

Cocrystallization is a versatile supramolecular synthetic strategy for tuning the properties of organic semiconductors (OSCs) and related polycyclic aromatic hydrocarbons (PAHs) by controlling their packing and architectures with suitable coformers. In this study, we demonstrate a supramolecular synthon substitution approach to afford cocrystals of 9,10-diphenylanthracene (DPA) and its isostere 9,10-dipyridylanthracene (DPyA) with halogenated coformers 1,2-diiodotetrafluorobenzene (1,2-C₆I₂F₄), 1,4-diiodotetrafluorobenzene (1,4-C₆I₂F₄), and 1,3,5-triiodotrifluorobenzene (1,3,5-C₆I₃F₃). The strategy enables reliable replacement of [C–I···π] interactions in DPA cocrystals with [C–I···N] interactions in the corresponding DPyA cocrystals. Although coformers and substitutions alter the supramolecular architectures, the photophysical properties and molecular conformations of the OSC building blocks remain largely preserved. The results highlight synthon substitution as a reliable supramolecular design element that accelerates the derivatization of established OSCs and their isosteres, offering opportunities for property modulation.