We investigated the growth temperature dependence of the structural and electrical properties of Sn-doped Ga2O3 homoepitaxial films grown on single-crystal β-Ga2O3 (010) substrates by molecular beam ...epitaxy. Ga2O3 films with an atomically smooth surface were obtained at growth temperatures of 550–650°C. On the other hand, a delay in the incorporation of Sn atoms in Ga2O3, which was probably due to segregation, occurred in the initial stage of growth at higher than 600°C. To ensure that Sn-doped Ga2O3 films with both high crystal quality and accurately controlled carrier density are obtained, the optimum growth temperature should be set at 540–570°C.
•We investigated the growth temperature dependence of Ga2O3 homoepitaxial films.•Atomically smooth Ga2O3 films were obtained at growth temperatures of 550–650°C.•The doping delay of Sn in Ga2O3 occurred at higher than 600°C.•High-quality Ga2O3 films can be obtained in a narrow Tg range of 550–570°C.
Poly (butylene terephthalate) (PBT) nanofibrils (NFs) were developed in-situ by implementing a rheologically tuned melt spinning process on poly (lactic acid) (PLA)/PBT blends. In the absence of any ...flow fields, melt crystallization of fabricated PLA/PBT in-situ nanofibrillar composites (NFCs) resulted in orthogonal patterning of PLA nanodomain crystallites around single or double PBT NFs. Geometric confinement (soft epitaxy) was the nucleation mechanism of PLA chains at the interface of isotropic distributed PBT NFs followed by the formation of reprocessible 2D nanohybrid shish-kebab (NHSK) superstructures. By increasing the PBT NFs content and their bundling, a fan-shaped transcrystalline structure was formed due to seeding or epitaxial nucleation on the bundle of PBT NFs owning a less curved interface. The nucleation and growth mechanism of crystallites structures which were influenced by temperature and PBT NF content have been discussed thermodynamically and kinetically by parallel investigations on microscopic observations and X-ray diffraction analysis. The evolution of different crystalline structures in quiescent melt in the forms of spherulites, NHSK, or fan-shaped transcrystallinity induces a local orientation in the isotropic NFCs. Mechanical propertie improvements of NFCs were compared in amorphous and crystalline states with tailored NHSK superstructures.
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•Geometric confinement (soft epitaxy) was the nucleation mechanism in the formation of reprocessible 2D nanohybrid shish-kebab (NHSK) superstructures.•The PLA fan-shaped transcrystalline structures were formed by increasing the PBT NFs content and their bundling due to seeding or epitaxial nucleation on the bundle of PBT NFs.•The curvature of the interface in fibrillar composites plays a dominant role in crystallite nucleation and final crystalline phase structure.•The evolution of crystalline structure in the form of spherulites, NHSK, or fan-shaped transcrystalliny induces a local orientation in isotropic NFCs.•The crystalline phase morphology of PLA was tailored to improve its mechanical properties while stopping aging.
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•Activated carbon induced α-FeOOH morphology and crystal transformation to amorphous FeOOH.•Sulfur capacity of 482.3 mg/g, greatly exceeding that most studies.•Synergistic effect ...between amorphous FeOOH and activated carbon promotes catalytic activity.•Catalytic oxidation mechanism reveled for H2S removal.
The performance of FeOOH for the removal of hydrogen sulfide (H2S) has been widely investigated. However, the harsh conditions of use and the difficulty of regeneration limit its practical application. In this study, FeOOH was loaded on activated carbon (AC) by a hydrothermal method to obtain a series of XF-AC catalysts for the removal of H2S from blast furnace gas (BFG). Among these catalysts, 3F-AC exhibited a high penetrating sulfur capacity of 482.3 mg/g and good regeneration performance. It is noteworthy that the use of AC as the support induced the transformation of α-FeOOH crystals into amorphous FeOOH and affected their morphology, and uniformly dispersed nanoparticles rather than agglomerated acicular crystals appeared on the surface of AC. The presence of amorphous FeOOH modulated the basic sites and surface hydroxyl groups of the catalysts while generating hydroxyl radicals during the reaction, thus improving the adsorption and oxidation of H2S. More importantly, the structural properties (surface area and pore volume) of 3F-AC enhanced the storage capacity of elemental sulfur and reduced the formation of by-products. The cyclic catalytic role of Fe3+/Fe2+ played an important role in the oxidation process. This work provides a simple and effective strategy for the design of BFG desulfurization catalysts.
Reasonable slag fluidity is essential for stable HIsmelt process operation. During the slag-tapping process, crystallization will cause the slag viscosity to rise sharply, which is not conducive to ...stable slag-tapping operation, especially for smelting high-titanium slag. In this paper, the viscosity of the CaO-MgO-Al2O3-SiO2-TiO2-FeO slag with varying 10–50% TiO2 content was studied in the laboratory. The crystalline phases of water quenched slag samples at different temperatures were determined by XRD, and it was verified with the results of Factsage thermodynamic calculations. In addition, the effects of crystalline phase, crystalline morphology and crystal size on the critical viscosity of slag were discussed through SEM-EDS analysis. The results show that the proper TiO2 content in the slag is below 40%, the temperature of critical viscosity (Tcv) of the slag is between 1336 °C and 1360 °C, and the Tcv of the slag with a TiO2 content of 50% increases to 1500 °C. The sudden increase in viscosity is related to the crystallization behavior of the slag. With the increase of TiO2 content, the main precipitated titanium-rich phase in the slag changed from dendritic perovskite to plate-shaped pseudobrookite. Among them, when the TiO2 content is 10%, the sharp increase in viscosity of the slag is mainly determined by the precipitation amount of melilite. The amount of crystals in the slag between 20% and 43% causes the viscosity of the slag to rise rapidly, which is mainly due to the fact that the granular crystals have a greater influence on the viscosity than the plate crystals. Compared with the experimental results, it is found that Factsage software cannot accurately calculate the phase equilibrium of slag with a TiO2 content of 40–50%.
Polylactic acid (PLA) is one of the most popular thermoplastics for fused deposition modeling (FDM). Attributed to its semi-crystalline nature, the relation between printing parameters and properties ...are more complicated than amorphous thermoplastics like acrylonitrile-butadiene-styrene (ABS). This study was designed to investigate two printing parameters, layer height (0.2 and 0.4 mm) and plate temperature (30 and 160 °C) on the Izod impact strength of printed PLA. X-ray diffraction (XRD) analysis confirmed the existence of α crystals in parts printed from 160 °C-plate temperature and α′ crystals in those printed at 30 °C-plate temperature. Parts printed with a 160 °C (plate temperature) had higher crystallinity. Polarized optical microscope (POM) observations illustrated that the plate temperature of 160 °C and layer height of 0.2 mm induced higher crystallinity, smaller crystals and interfacial crystal bands. The Izod impact strength of printed PLA at higher plate temperature was up to 114% higher than injection molded PLA made using conventional molding parameters.
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•Printed PLA from FLM process can be 114% higher in Izod impact strength than injection molded PLA.•High crystallinity and small crystal size induced by a high plate temperature improves the toughness of printed PLA.•Crystal morphology at the interfaces among printed layers was visualized for the first time by a light microscope and SEM.
•Organic phase change materials promote hydrate nucleation.•Hydrate nucleates quickly in presence of phase change materials and Tween80 or Span80.•Phase change materials reduce the scatter of the ...induction time of hydrate formation.•The hydrophobic CA–DE droplets provide hydrate nucleation sites.
The effects of organic phase change material (PCM) and surfactant on HCFC141b hydrate nucleation are investigated under quiescent conditions. The surfactants Tween80 and Span80 are chosen as emulsifiers, and the mixture of PCM n-decanoic acid (CA) and dodecyl alcohol (DE) is used as promoter. The emulsion of HCFC141b + CA–DE (the mass ratio of CA to DE is 1:1) + Tween80 or Span80 + H2O is prepared, where CA–DE is dispersed in water and HCFC141b is dissolved into CA–DE. The hydrophobic CA–DE droplets create an increased local HCFC141b concentration, and organize the surrounding water into a clathrate-like structure. Additives of 1 wt% CA–DE and 1 wt% Tween80 have the best promotion effect on the nucleation of HCFC141b hydrate. The nucleation of HCFC141b hydrate has a stochastic nature and the additives (CA–DE, Tween80 and Span80) reduce the scatter of the induction time of HCFC141b hydrate formation.
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•The supersaturation controls the struvite morphology.•The supersaturation controls the share of fine crystals and size distribution.•The size and morphology of struvite crystals ...affect the particle settleability.•The multifaceted morphology emerges due to different growth rate of crystal faces.•The supersaturation and pH mediate the aggregation of struvite crystals.
Struvite crystallization is widely applied for nutrient recovery from wastewater streams. The better understanding of the effects of reaction conditions on final crystal properties will contribute to improve both the recovery efficiency and product quality of struvite as a fertilizer. In this study, batch crystallization experiments were performed in laboratory scale to reveal the effect of supersaturation on the phosphorus recovery and crystal properties. For this purpose, supersaturation is regulated through varying the pH, magnesium and ammonium concentrations in solution. The effects of these parameters on controlling crystal properties such as size and morphology are highlighted through their role as supersaturation regulators.
The potential implications of different crystal morphologies on settling velocity and aggregation of crystals are also discussed. This improved understanding could aid in improved struvite crystallization processes for wastewater treatment.
•Existing of ethanol or rapid increases of supersaturation alters crystal morphology.•The thickness of Form B crystals decreases in the high concentration of ethanol in solution.•Form B is ...transferred to Form A by solution-mediated phase transformation.•Form B is a more stable form than Form A in terms of thermodynamic stability.
L-Histidine(L-His) has two polymorphs of FormA and FormB. It is known that the crystallization of polymorphs is influenced by antisolvents. In this study, crystal morphology of polymorph was considered from prediction of crystal structures. Next, the effects of ethanol on polymorphs and morphology of L-His were studied by evaluating crystals obtained from saturated aqueous solutions by cooling or adding of ethanol. From the prediction of crystal structures, It is suggested that FormA crystal tend to grow in the long side direction. Experiments show that FormA tends to be obtained from aqueous solvent, on the other hands, FormB tends to be obtained from ethanol existing solution. However, FormB were found to dissolve gradually and transited to FormA. Furthermore, results show high concentration of ethanol change the morphology along its thickness direction, so it suggests that the effect of antisolvents has a big influence on crystallization. Moreover, the results of Thermogravimeter-Differential Thermal Analyzer (TG-DTA) and Differential Scanning Calorimetry (DSC) analysis demonstrate that FormB, which is thought as a metastable form, is possibly favorable in term of thermal stability and suggests the behavior of melting and decomposition of L-His.
Li‐rich oxides can be regarded as the next‐generation cathode materials for high‐energy‐density Li‐ion batteries since additional oxygen redox activities greatly increase output energy density. ...However, the oxygen loss and structural distortion induce low initial coulombic efficiency and severe decay of cycle performance, further hindering their industrial applications. Herein, the representative layered Li‐rich cathode material, Li1.2Ni0.2Mn0.6O2, is endowed with novel single‐crystal morphology. In comparison to its polycrystal counterpart, not only can serious oxygen release be effectively restrained during the first oxygen activation process, but also the layered/spinel phase transition can be well suppressed upon cycling. Moreover, the single‐crystal cathode exhibits the limited volume change and persistent presence of superlattice peaks upon Li+ (de)intercalation processes, resulting in enhanced structural stability with absence of crack generation and successive utilization of oxygen redox reaction during long‐term cycling. Benefiting from these unique features, the single‐crystal Li‐rich electrode not only yields a high reversible capacity of 257 mAh g−1, but also achieves excellent cycling performance with 92% capacity retention after 200 cycles. These findings demonstrate that the morphology design of single crystals can be regarded as an effective strategy to realize high‐energy density and long‐life Li‐ion batteries.
The electrochemical behaviors, structural evolution, and oxygen activities of polycrystal and single‐crystal Li‐rich electrodes are comprehensively compared, which effectively demonstrate that the morphology design of single crystals can be regarded as an effective strategy to realize next‐generation high‐energy‐density Li‐ion batteries.
In the present study the effect of three commercially available anionic surfactants on the hydrate growth from a gas mixture of 90.5
mol% methane/9.5
mol% propane mixture was investigated. The ...surfactants used were sodium dodecyl sulfate (SDS), sodium tetradecyl sulfate (STS), and sodium hexadecyl sulfate (SHS). The morphology of the growing crystals and the gas consumption were observed during the experiments. The results showed that in the presence of surfactants, branches of porous fibre-like crystals were formed instead of dendritic crystals formed in the absence of any additive. In addition, extensive hydrate crystal growth on the crystallizer walls and a “mushy” hydrate layer instead of a thin crystal film appeared at the gas/water interface. Finally, the addition of SDS with concentration range between 242 and 2200
ppm (Δ
T=13.1
K) was found to increase the mole consumption for hydrate formation by approximately 14 times compared to pure water. This increase is related to the change in hydrate morphology, whereby a more porous hydrate forms with enhanced water/gas contacts.
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