One-step Crystallization Process Research Articles

An Efficient Ionic Liquid-Mediated Extraction and Enrichment of Isoimperatorin from Ostericum koreanum (Max.) Kitagawa.

Ionic liquids (ILs) have attracted significant interest because of their desirable properties. These characteristics have improved their application to overcome the shortcomings of conventional separation techniques for phytochemicals. In this study, several ILs were investigated for their capacity to extract isoimperatorin, a bioactive furanocoumarin, from the roots of Ostericum koreanum. Herein, 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) was selected as a promising IL for separating isoimperatorin. A central composite design was applied to optimize the extraction conditions. Under the optimal conditions, the yield of isoimperatorin reached 97.17 ± 1.84%. Additionally, the recovery of isoimperatorin from the [Bmim][BF4] solution was successfully achieved (87.73 ± 2.37%) by crystallization using water as an antisolvent. The purity of the isoimperatorin was greatly enhanced, from 0.26 ± 0.28% in the raw material to 26.94 ± 1.26% in the product, in a one-step crystallization process. Namely, an enhancement of approximately 103-folds was reached. The developed approach overcomes the shortcomings of conventional separation methods applied for gaining isoimperatorin by significantly reducing the laboriousness of the process and the consumption of volatile organic solvents. Moreover, the simplicity and effectiveness of the method are assumed to be valuable for producing isoimperatorin-enriched products and for promoting its purification. This work also confirms the efficiency of ILs as a promising material for the separation of phytochemicals.

Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide (CTAB) through a facile one-step crystallization process. Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles. The influences of crystallization conditions were investigated, and the possible synthesis mechanism was proposed. ZSM-5 zeolites with different amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol. The results showed that a trace amount of CTAB significantly promoted the crystallization of ZSM-5 zeolite, with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates. CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates. The ZSM-5 zeolite with the smallest primary particles of 50–80 nm exhibited large specific surface area, abundant mesopores, and the greatest microporosity. The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

Enantiomer-selective magnetization of conglomerates for quantitative chiral separation

Selective crystallization represents one of the most economical and convenient methods to provide large-scale optically pure chiral compounds. Although significant development has been achieved since Pasteur’s separation of sodium ammonium tartrate in 1848, this method is still fundamentally low efficient (low transformation ratio or high labor). Herein, we describe an enantiomer-selective-magnetization strategy for quantitatively separating the crystals of conglomerates by using a kind of magnetic nano-splitters. These nano-splitters would be selectively wrapped into the S-crystals, leading to the formation of the crystals with different physical properties from that of R-crystals. As a result of efficient separation under magnetic field, high purity chiral compounds (99.2 ee% for R-crystals, 95.0 ee% for S-crystals) can be obtained in a simple one-step crystallization process with a high separation yield (95.1%). Moreover, the nano-splitters show expandability and excellent recyclability. We foresee their great potential in developing chiral separation methods used on different scales.

Self-Limited Growth of Nanocrystals in Structural Heterogeneous Phase-Change Materials during the Heating Process

Typical nanocomposite heterogeneous ZnSb-Al2O3 and ZnSb-ZnO phase-change materials were prepared. A direct comparison of the distinct structures in the amorphous, metastable, and stable states between two different materials was investigated systematically. Upon heating, ZnSb-Al2O3 films show a two-step crystallization process with the formation of the metastable orthorhombic ZnSb phase ahead of the stable trigonal ZnSb phase, while ZnSb-ZnO films could exhibit a one-step crystallization process with the formation of the stable trigonal ZnSb phase when the ZnO-doping concentration is more than 12.3 atom %. In the case of ZnSb-Al2O3, the structural transition to the metastable phase is accompanied by a pronounced increase in the grain size up to 100 nm. Such an increase in the crystal grain size is not found in ZnSb-ZnO films; i.e., the nanocrystals do not grow significantly when the crystallized film is precipitated with the metastable ZnSb phase. By the method of advanced scanning transmission electron m...

One-step phase transition and thermal stability improvement of Ge2Sb2Te5 films by erbium-doping

The crystallization behavior of Er-doped Ge2Sb2Te5 phase-change materials is investigated systemically for phase change memory application. It is observed that Er dopants can serve as a center for suppression of face-centered-cubic to hexagonal phase transition of Ge2Sb2Te5 films, leading to a one-step crystallization process. The crystallization temperature, 10-year data retention ability and crystalline resistance of Ge2Sb2Te5 films can be significantly increased. Raman spectra suggest that GeTe component is mainly responsible for the phase transition in Er-doped Ge2Sb2Te5 films.

Synthesis of Micro-Mesoporous Composites MCM-41/13X and Their Application on CO2 Adsorption: Experiment and Modeling

Two micromesoporous composites of MCM-41/13X are synthesized through a two-step crystallization process and a one-step crystallization process, respectively. The results of X-ray diffraction, nitrogen adsorption–desorption isotherms, Fourier transform infrared spectroscopy, and transmission electron microscopy results show that the as-prepared samples possessed both micropores and mesopores. The materials take advantage of not only the large adsorption capacity and thermal stability of the microporous material, but also the rapid diffusion and mass transfer of mesoporous materials, which lead to improve CO2 adsorption capacities compared to the pure microporous or mesoporous materials.

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

AbstractOne-step crystallization is one of the most energy conserving methods for glass-ceramics preparation. However, only a few kinetics studies focused on the glass-ceramics prepared by the one-step crystallization. The one-step crystallization kinetic parameters were studied using differential scanning calorimetry. The activation energy (Ea) and the Avrami parameter (n) were calculated as 152. 79 kJ · mol−1 and 4. 39, respectively. These parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent glass. The properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering method. This crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

Rare earth-modified kaolin/NaY-supported Pd-Pt bimetallic catalyst for the catalytic combustion of benzene.

A new type of porous kaolin/NaY composite (KL-NY) with a large specific surface area and large pore sizes was synthesized through a one-step crystallization process, and rare earth-modified KL-NY-supported Pd-Pt catalysts were studied for benzene combustion. The results indicated that the pore volume and specific surface area of KL-NY after calcination and crystallization were 0.298 cm(3)/g and 365 m(2)/g, respectively, exhibiting appropriate pore structure and good thermal stability. Catalysts with rare earth metals greatly enhanced the activity of Pd/KL-NY, and the addition of Pt and Ce into the Pd catalyst improved the catalytic activity as well as the stability. The catalyst with an optimal Ce content and Pt/Pd molar ratio (0.2%Pd-Pt (6:1)/6%Ce/KL-NY) demonstrated the best activity for the complete oxidation of benzene at 230 °C, and the catalyst above maintained the 100% benzene conversion for 960 h.

Pathway mediated microstructures and phase morphologies of asymmetric double crystalline co-oligomers

Various microstructures and phase morphologies of an amphiphilic poly(ethylene oxide)-block-polyethylene (PEO-b-PE) co-oligomer, controlled by topological restriction of PE segments on the tethered PEO chains, were characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), scanning electron microscopy (SEM), and synchrotron radiation wide-angle/small-angle X-ray scattering (WAXS/SAXS) in drop-cast films. The crystallization processes were mediated by two pathways, a one-step crystallization process (I) and a sequential crystallization process (II). Results show that the thermal procedures have great influence on the microstructures and phase morphologies of PEO-b-PE co-oligomer, e.g., negative spherulites with radial stripes were detected in the one-step crystallization process (I), while crystalline texture, which contains a large number of crystals with reduced sizes, formed in the sequential crystallization process (II). Based on our experimental data, the topological restriction effect encountered by PEO chains depends on the hard confinement of PE crystals and the soft confinement of amorphous PE in the two crystallization procedures. The formation mechanisms of the long-range order structures within the co-oligomer were elucidated through morphology models. These nano-patterned structures make the double crystalline block copolymers outstanding candidates for surface modification, micromolding, and optoelectronic devices in nanotechnological and biomedical applications.

Regioselective acylation of methyl-α-d-glucopyranoside with different acylating agents catalysed by micro/mesoporous materials

The composite microporous/mesoporous material ZSM-5/MCM-48 was successfully prepared by hydrothermal synthesis using a simple one-step crystallization process. The material was a mesoporous composite containing zeolite and crystals of ZSM-5. The textural and structural features of this material were characterized by use of powder XRD, nitrogen sorption, FTIR spectroscopy, SEM, and TEM. The mesoporous material obtained, Al-MCM-48, and the composite material, ZSM-5/MCM-48, were used as catalysts for acylation of methyl-α-d-glucopyranoside. Fatty acids (n = 10, 14, and 16) and fatty acid chlorides were used, individually, as acylating agents for this reaction. The effects of solvent, type of catalyst, and nature of the fatty acids on the acylation reaction were investigated. Reaction yields in the range 50–70 % were achieved by use of this synthetic pathway. The products resulting from the acylation reaction are new nonionic bio-surfactants.

Structure and dynamics in the crystallization of Ni500 nanocluster

Molecular dynamics simulations are performed on nano clusters with 500 nickle atoms (Ni500) to determine the structure and dynamics in the isothermal crystallization using embed atom model potentials. Through the study of nano Ni cluster dynamic behavior, we find that multi-step crystallization process of Ni500 is at temperatures far below the melting temperature (Tm), whereas one-step crystallization process is at the temperatures just below Tm. Multi metastable states are observed before Ni500 becomes fully crystallized in multi-step crystallization process. We find that atom rearrangements take not only string-like cooperative motion manner but also other collective motion manner.

Crystallization characteristics of Mg-doped Ge2Sb2Te5 films for phase change memory applications

Mg-doped Ge2Sb2Te5 (GST) films with different Mg doping concentrations have been prepared, and their crystallization behavior, structure and electrical properties have been systematically investigated for phase-change memory applications. The results show that the addition of Mg into GST films could result in an enhancement in crystallization temperature, activation energy and electrical resistance compared with the conventional GST films, indicating that a good amorphous thermal stability. On the other hand, the proper Mg concentration ranging from 13.6 to 31.1at.% can lead to a one-step crystallization process from amorphous to faced-centered cubic (fcc) phase and suppress the formation of the hexagonal close-packed (hcp) crystalline phase. X-ray photoelectron spectra (XPS) further confirm that the formation of covalent MgSb and MgTe bonds contribute to the enhanced thermal stability in Mg-doped GST films.

Crystallization mechanism in Sb:Te thin films

The aim of this work is to study the mechanism of crystallization in Sb:Te thin films using differential scanning calorimetry (DSC), four-probe resistivity and X-ray diffraction (XRD) measurements. The DSC showed that the Sb 70+ x Te 30− x films with x in the range of −3⩽ x⩽3 show one exothermic reaction at 110 °C, whereas the films with x in the range of 3⩽ x⩽13 present an additional one at about 70 °C. XRD measurements and Rietveld analysis have shown that the first exothermal peak can be associated to the formation of crystalline Sb and the second to the process of transformation of the Sb and the remaining material into a more stable Sb 2 n Te 3 crystalline phase. Appearance of additional Sb phase decreases the crystallization temperature of Sb 70+ x Te 30− x films. These structural transformations are also observed in the four-probe resistivity measurements: a one-step crystallization process in the Sb 70+ x Te 30− x films with x in the range of −3⩽ x⩽3and a two-steps crystallization process in films with x in the range of 3⩽ x⩽13. The results of this investigation have shown that the amorphous-to-crystalline phase transformation in eutectic Sb:Te depended on the films composition.

Effect of cobalt on the crystallization of Ni 50Zr 50 amorphous alloys

The effect of cobalt on the crystallization process and products of Ni 50− x Co x Zr 50 amorphous alloys was investigated by DSC calorimetry and transmission electron microscopy. All the samples investigated show a one-step crystallization process. The crystallized samples with 0 at.% Co, 5 at.% Co and 10 at.% Co content are characterized by an orthorhombic crystal structure. With increasing cobalt content a cubic phase was detected between the orthorhombic (Ni, Co)Zr phases.