One-step Crystallization Research Articles

Optical properties of advanced lithium disilicate.

A variety of firing protocols are available for the IPS e.max lithium disilicate (LD) and can be used for new, 'advanced' LD (ALD). However, the impact of firing protocols on the optical properties of ALD is still unknown. The aim of the present study was to evaluate the color difference (ΔE00), the translucency parameter (TP00) and the whiteness index for dentistry (WID) for both LD glass ceramics after the processes of firing/glazing. Fifty disk-shaped specimens, with a diameter of 10 mm and a thickness of 1.2 mm, were fabricated from IPS e.max CAD (LD; Ivoclar) and another 50 from CEREC Tessera™ (ALD; Dentsply Sirona). The specimens from each group were further divided into 5 subgroups (n = 10) according to the firing/glazing protocol applied: crystallization (c); one-step crystallization and glazing (cg); crystallization and refiring (c-r); two-step crystallization and glazing (c-g); or long-firing crystallization (lfc). The ΔE00, TP00 and WID were assessed. The statistical analysis of ΔE00 was performed using the one-way analysis of variance (ANOVA) and Tukey's post hoc test, while TP00 and WID were analyzed with the two-way ANOVA and Tukey's post hoc test at a statistical significance level of 0.05. The cg groups were designated as the reference. The ANOVA showed that the firing procedures had no effect on ΔE00, TP00 and WID in the case of LD. In addition, LD exhibited greater translucency and brightness as compared to ALD. For ALD, all color changes observed in relation to the reference firing protocol were clinically unacceptable. The ALD specimens which underwent 1 standard firing cycle showed higher TP00 and WID values than other ALD groups. The choice of the firing protocol has no impact on the color, TP00 or WID of LD. Additionally, LD presents higher WID values than ALD, irrespective of the firing protocol used. Alternative firing protocols result in clinically unacceptable color variations when compared to the manufacturer-recommended protocol for ALD. Advanced LD is more sensitive to different firing protocols with regard to its optical properties, which makes the workflow less predictable in comparison with LD.

Preparation of enstatite-spinel based glass-ceramics from ferronickel slag and iron ore tailings by microwave-assisted one-step crystallization

A novel method to prepare high-quality enstatite-spinel based glass-ceramics by co-utilization of ferronickel slag (FNS) and iron ore tailings (IOT) via microwave-assisted one-step crystallization was proposed with an emphasis on the effect of IOT content on the preparation process. The thermodynamic analysis demonstrated that incorporating appropriate amounts of IOT into FNS can effectively transform olivine in FNS into enstatite. The experimental exploration revealed that the crystallization activation energy of the parent glass decreased from 564.6 kJ/mol to 351.93 kJ/mol when the IOT content increased from 30 wt% to 45 wt%. Meanwhile, the Avrami index of the parent glass increased from 3.88 to 4.81, indicating less depolymerization. In the subsequent crystallization process, with increasing content of IOT, the main phase was enstatite, accompanied by small amounts of spinel which acted as nucleation sites promoting the enstatite formation. Due to the decreased depolymerization degree that resulted in fewer nucleation sites, the average grain size of enstatite increased from 123 nm to 196 nm. By controlling crystallization of the melted mixture of 65 wt% FNS and 35 wt% IOT at 863 °C for 20 min, the resulting enstatite-spinel based glass-ceramics had excellent comprehensive properties, namely density of 3.13 g/cm3, bending strength of 153.53 MPa, Vickers microhardness of 9.22 GPa, acid resistance of 99.89%, and alkali resistance of 99.72%. With a much shorter crystallization time (1/6 of conventional one), the product obtained by microwave-assisted one-step crystallization had properties comparable to those derived from similar wastes.

Preparation of Li2O–Al2O3–SiO2–B2O3（LASB）glass-ceramic with low thermal expansion coefficient from spent hydrogenation catalysts and crystallization kinetics

The recovery of spent hydrogenation catalysts occupies advantages in both alleviating environmental burden and resource shortage. Whereas, the development of conventional hydrometallurgical recovery of molybdenum (Mo) and nickel (Ni) from spent MoNi/Al2O3 catalysts has been limited by the numerous processes and the accompanying generation of waste liquids and residues. Herein, A new recycling route for the preparation of spent hydrogenation catalysts with low thermal expansion coefficients (CTE) was proposed, which has the advantages of short process, green environment and high value utilization. The Li2O–Al2O3–SiO2–B2O3 (LASB) parent glass containing Mo and Ni were obtained by melting with different contents of the spent catalysts. The thermal expansion coefficient of the glass was minimized to 6.08 × 10−6/°C at an addition of 25 wt% of the spent catalysts. Moreover, according to the crystallization peak in DTA curve, glass-ceramics were prepared by one-step crystallization heat treatment at different crystallization temperatures. The main crystalline phase of the glass-ceramic precipitated by heating at 685 °C is β-quartz (Li2Al2Si3O10), which gives the glass-ceramics the lowest coefficient of thermal expansion (0.96 × 10−6/°C) of glass-ceramic as well as the maximum density (2.45 g/cm3) and Vickers hardness (705.8 Hv). Furthermore, the activation energy (354.65 ± 17.42) kJ/mol) and Avrami index (5.39) associated with crystallization were extracted from the fitting of different theoretical model, indicating the three-dimensional crystallization of the LASB glass-ceramics. This technology provides a waste-to-material strategy for hazardous waste and a clean production route for the preparation of the functional glass-ceramics.

ZIF-8 membranes on ZIF-8-PVDF/PVDF dual-layer polymeric hollow fiber supports for gas separation

ZIF-8 membranes have attracted extensive research attention due to their ease of synthesis, stable properties, and wide applicability. Compared to expensive inorganic supports, organic polymer supports are more flexible and inexpensive. However, addressing the issue of weak adhesion between the surface of the organic support and the ZIF-8 membrane layer poses a significant challenge. In this study, we present a strategy for preparation of ZIF-8 membrane by the fabrication of an asymmetric dual-layer polymeric hollow fiber support using polyvinylidene fluoride (PVDF) as the material. The outer layer of the support is composed of PVDF embedded with ZIF-8 seeds, while the inner layer consists of pure PVDF. This approach addresses the weak adhesion between the support and the ZIF-8 membrane layer formed through a one-step solvothermal crystallization process. The effects of ZIF-8 seed size, content, and crystallization conditions on the membrane structure and performance are investigated. Under the synergistic molecular sieving effects of ZIF-8 continuous membrane layer and ZIF-8 crystals within the outer layer of the support, larger gas molecules are difficult to penetrate the membrane layer, making the resulting membrane highly selective for the gas separation. Under the optimal fabrication conditions, the H2 permeability of the ZIF-8 membrane is determined to be 1.52 ± 0.1 × 10−7 mol·Pa−1·s−1·m−2, with a H2/N2 ideal separation selectivity of 69.5 ± 4. This method demonstrates simplicity and high reproducibility for preparation of ZIF-8 membranes on dual-layer hollow fibers, and it is expected to be extended to the growth and fabrication of other MOF membranes.

Enhancement of particle properties of cefuroxime sodium by simultaneous control of polymorph and uniform spherulites

Cefuroxime Sodium (CS) is a low-toxicity and highly effective antibiotic drug with a wide application market. Its polymorph form β has the advantage of thermal stability and resistance to degradation. However, poor powder properties cause filtration difficulties, severe electrostatic phenomena and difficulties in automated dispensing, which limit its application. In order to improve the powder properties and stability of CS from the source, we used a one-step crystallization method to prepare CS (form β) with high sphericity and uniform particle size. The spherulites of form β of CS (β spherulites) have excellent powder properties, with high flowability (32.8°), good sphericity (90.2%), low C.V. (45.6%), and adjustable particle size distribution. Thanks to improved powder properties, the β spherulites exhibits 40% higher thermal stability and maximum 41% faster dissolution rate in the compatible solutions, compared to commercially available products, which implies the β spherulites is more competitive in powder formulations.

Purification of monoethylene glycol by melt crystallization

Separation of glycols with close boiling points and relatively high viscosity at their melting point is a challenge in the production of high purity products downstream of biorefinery processes. In this work, the efficiency of the layer melt crystallization process with acetone as the assisting solvent was evaluated for a mixture of monoethylene glycol and 1,2-pentanediol. Solid-liquid equilibrium was measured and modelled with the NRTL and modified UNIFAC group-contribution models to evaluate the thermodynamic driving force of crystallization. Layer melt crystallization was conducted to determine the effect of solvent composition on purity, distribution coefficient of impurity, crystal growth rate, and yield at different operating conditions. Addition of the solvent altered the thermodynamics and kinetics of crystallization, thereby altering the purity level of the final product. An effective distribution coefficient of impurity between 0.1 and 0.6 in one-step crystallization was obtained, depending on the solvent composition and the applied operating conditions.

Preparation of Ultrafine Nitroguanidine by One-Step Crystallization in an Impinging Stream-Rotating Packed Bed

To solve the problems of the traditional production process of ultrafine nitroguanidine (NQ), such as a long process and easy pollution caused by recrystallization, the ultrafine NQ (2–6 μm) was prepared by the one-step crystallization in an impinging stream-rotating packed bed (IS-RPB). The influence of operation parameters on the size of the NQ crystal was discussed through various particle size characterization methods. Results show that the size of ultrafine NQ prepared in the IS-RPB was 2.0–3.0 μm, which was smaller than that of market products and conformed to the military standard. Simultaneously, the crystal morphology tended to reduce the length, meeting the target requirement of “shorter and thicker” high-end products. The role of high dispersion and strong mixing in the IS-RPB was the key to continuous and one-step nucleation and crystallization of NQ. One-step crystallization in the IS-RPB is a push flow operation process, where abundant accumulation of the raw material will be avoided effectively, and the safety of energetic material processing will be enhanced greatly. Ultrafine NQ can be prepared without recrystallization, which greatly reduces the energy consumption and the pollution of organic impurities to the product and the environment, providing a new way for the continuous production of ultrafine NQ.

One-step crystallization in (Ge2Sb2Te5)90Ga10 thin film

Owing to data storage ability of chalcogenide based Ge2Sb2Te5 phase change alloy, this composition has been tremendously explored for its application in memory devices. Upon annealing, this composition exhibit two step crystallization, i.e, amorphous -to- fcc, and then from fcc -to- hcp phase. To address the issue of power consumption in such phase transitions, the present study is reporting one-step crystallization in (Ge2Sb2Te5)90Ga10 thin film, i.e., from amorphous -to- fcc phase which is confirmed by optical transmission contrast studies. Thus, the results poses the promising data storage applicability of (Ge2Sb2Te5)90Ga10 thin film in phase change memory devices.

One-Step Microcrystalline Glass Preparation Using Smelting Slag from Waste Automobile Three-Way Catalysts through Iron Collection

The smelting slag obtained through iron collection from waste automobile three-way catalysts was used as a raw material to prepare microcrystalline glass through a one-step crystallization heat treatment. The phase composition and microstructure of the prepared glass were analyzed through X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectroscopy, respectively. Single-factor experiments were conducted to investigate the effects of crystallization temperature from 900 to 950 °C and crystallization time from 0.5 to 4 h on the physical and chemical properties of the microcrystalline glass. The results indicated that the optimum crystallization temperature and time for preparing microcrystalline glass with glass smelting slag through the proposed one-step crystallization heat treatment process were 950 °C and 3 h, respectively. Under these experimental conditions, the number of crystalline phases of the microcrystalline glass was high, the grains were mainly spherical and columnar particles, the sample structure was dense, and the best results were obtained: the density was 2.72 g/cm3, the water absorption was 1.55%, the porosity was 4.2%, the Vickers hardness was 618 HV, the acid resistance was 2.6%, and the alkali resistance was 0.04%. In addition, the results of the toxicity characteristic leaching procedure indicated that the leaching concentrations of heavy metals such as Zn, Cr, and Pb in the microcrystalline glass were lower than those in the base glass and were considerably lower than the acceptable limits. The microcrystalline glass obtained from final smelting slag through heat treatment can enhance the stabilization of harmful elements. The findings of this study can be applied to the treatment of bulk solid waste.

A new approach to determine/design the eutectic composition of binary, ternary, and high-entropy alloys using electromagnetic directional crystallization

Eutectic materials have been widely employed in many high-tech fields, and recently, eutectic high-entropy alloys (EHEAs) have become a research focus of eutectic materials; however, it is challenging to determine/design the eutectic composition of alloys accurately, especially multi-component alloys and EHEAs. In this study, a new electromagnetic directional crystallization approach was proposed to determine/design eutectic alloy compositions. First, standard eutectic Al-Si, Al-Si-Fe, Al-Si-Ti, and Al-Si-Fe-Mn alloys were obtained by directly separating their respective melts using electromagnetic directional crystallization. Then their eutectic compositions were accurately determined by inductively coupled plasma-optical emission spectroscopy. Conflicting reports about the eutectic reactions and phase transformations occurring in the Al-Si-Ti system were also resolved. Thereafter, the application of electromagnetic directional crystallization was extended to EHEAs. The widely investigated AlCoCrFeNi 2.1 EHEA was confirmed to have a eutectic composition, and a new EHEA Al 16.8 Co 12.6 Cr 13.8 Fe 11.8 Ni 45.1 with a combination of high strength and high ductility was obtained in this study by separating the AlCoCrFeNi 3 melt via electromagnetic directional crystallization. Therefore, in the absence of thermodynamic data, electromagnetic directional crystallization provides a promising approach for determining and designing the eutectic composition of alloys, especially EHEAs. This new approach is more direct, efficient, and simpler than the conventional thermodynamic-calculation approach because the application of the latter is significantly limited when thermodynamic data are not available. • A new approach is proposed to design eutectic high-entropy alloys without thermodynamic calculation. • A new eutectic high-entropy alloys, Al 16.8 Co 12.6 Cr 13.8 Fe 11.8 Ni 45.1 , was designed and reported. • Standard eutectic alloys were prepared through one-step electromagnetic directional crystallization. • Controversial research results about AlCoCrFeNi 2.1 alloy and the Al-Si-Ti system were finally solved.

Effects of coordination field environment on the fluorescence properties of transparent ZnGa2O4 glass-ceramics doped with Mn2+ and Cr3+ ions

The transparent ZnGa2O4 glass-ceramics doped with Mn2+/Cr3+ ions were prepared by a one-step crystallization method. The visible light fluorescence properties of Mn2+ ions in 6-coordination and 4-coordination environments and the visible light fluorescence properties of Mn2+/Cr3+ ions co-doped in transparent ZnGa2O4 glass-ceramics were studied. The results manifest that in the parent glass, Mn2+ ions mainly occupy the network former in the form of Hexa-coordination, and the luminescence center can emit orange-yellow light at ~600 nm. In transparent ZnGa2O4 glass-ceramics, Mn2+ ions and Cr3+ ions appear at the four-coordination site (Zn site) and six-coordination site (Ga site) in ZnGa2O4 spinel, respectively, and they can radiate green (510 nm) and red light (688 nm), respectively. An energy transfer mechanism of Mn2+→Cr3+ exists in ZnGa2O4: Mn2+/Cr3+ and different colors of luminescence can be produced by changing the molar ratios of components and test conditions. CIE results show that Mn2+-single-doped parent glass and glass-ceramics can be used in orange-yellow and green light displays, while Mn2+/Cr3+ co-doped transparent ZnGa2O4 glass-ceramics can be used as ideal materials for the green and red light displays.

Thermal Properties, Microstructure and Crystallization of Blends of Leaf Lard and Cottonseed Oil Stearin.

Blend oils composed by leaf lard (LL) and cottonseed oil stearin (COS) were prepared and the thermal property, microstructure and crystallization of these blends were investigated in the present study. Solid fat content (SFC), thermal behaviors, triacylglycerols composition, crystal structure and morphology of the LL and COS blends were determined by pulsed nuclear magnetic resonance (pNMR), differential scanning calorimetry (DSC), high-performance liquid chromatography (HPLC), X-ray diffractometer (XRD) and polarized light microscope (PLM), respectively. SFC profiles and iso-solid diagrams indicated that SFCs of all blends were almost close to the weighted averages of the fat components at temperatures beyond 20°C; however, below 20°C, SFCs of blends exhibited higher than those of the weighted averages of the fat components. With the content of COS increasing, palmitic acid and linoleic acid in the blends increased, while stearic acid and oleic acid decreased; monounsaturated-disaturated (USS) and triunsaturated (UUU) glycerides in the blends enhanced, while monosaturated-diunsaturated (UUS) glycerides declined. The melting temperature of the blends decreased with the increase of COS content. The crystal forms in LL were β' and β, and the packing pattern was double and triple chain length (2L and 3L). With COS in blends increasing, β' form crystals and 3L pattern reduced. Polarized light micrographs showed that the number of crystal particles in the blends raised with the increase of COS content, meanwhile, the grainsize of the sample gradually decreased. Visual appearances of the blends indicated that blending LL with COS could efficiently reduce the graininess of LL. The addition of COS had a significant effect on the crystallization behavior of LL. LL presented one-step crystallization at 10°C and 20°C, while COS showed two-step crystallization at 10°C and one-step crystallization at 20°C. However, the blends exhibited obvious two-step crystallization at 10°C, one-step or slight two-step crystallization at 20°C.

Rapid preparation of low thermal expansion transparent LAS nanocrystalline glass by one-step thermoelectric treatment

The Li2O–Al2O3–SiO2 (LAS) glass ceramics are prepared by one-step thermoelectric treatment. The influence of thermoelectric treatments on LAS glass-ceramics were studied. The crystal phase composition and microstructure of the LAS glass-ceramics were investigated by DSC, SEM, XRD and FTIR. Moreover, the thermal expansion performance and light transmittance of LAS nanocrystalline glass were characterized. The results show that low-expansion transparent LAS nanocrystalline glass can be produced in a short time by thermoelectric treatment. The free energy of nucleation and the degree of polymerization of the glass network are reduced by the electric field. The key is that the electric field polarizes Ti and Zr ions at the crystallization temperature, so that the crystal nuclei repel the same poles. This allows uniform crystal distribution, promotes crystallization and reduces one-step crystallization of crystal agglomeration. This proves that the rapid preparation of nanocrystalline glass by the one-step method is feasible, and provides a reference for the future one-step processing of glass-ceramics.

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.

Mechanism underlying two-step separated fcc-Al crystallization in Al-based metallic glasses

The precipitation of fcc-Al nanocrystals in Al-based metallic glasses was discussed and bifurcated into two classifications: one-step direct crystallization and two-step separated crystallization. In this work, we suggest that the inhomogeneous distribution of Al-rich regions in Al-based metallic glasses only determined the morphology of fcc-Al nanocrystals but not the two-step separated fcc-Al crystallization processes. Elemental doping (e.g., Si) is also excluded as a dominant factor of the two-step separated fcc-Al crystallization. In contrast, different processes of fcc-Al crystallization is most likely attributed to the maximum Al concentration and the adjacent gradient in the original Al-rich regions, the diffusion capability of each elements, and the completely crystallized products.

An Efficient Method for Extraction and Enrichment of γ-Linolenic Acid (GLA) from Spirulina

γ-linolenic acid (GLA) is useful for improving and treating various diseases, including immune system-related diseases. In the world of commerce, GLA production has problems that compel scientists to search for a simpler, safer, and less costly way. Some microalgae have been introduced as a rich source of fatty acids; Spirulina platensis has attracted scientists due to the presence of 31% GLA in its fatty acid profile. In the present study, the Iranian strain of spirulina was investigated. Cell culture was performed under optimized conditions and after dry biomass production; the powder was used to continue the study. Finally, the extraction and enrichment steps were performed, and the IR spectra and gas chromatography methods were used for identification and final measurements, respectively. After enrichment by one-step urea crystallization, the percentage of GLA enriched in the total lipid was increased to 61.17%. These results suggest that employing simple, relatively inexpensive, and modified methods for the GLA isolation from the Iranian strain of spirulina may have a potential for industrialization.

Synthesis of Cu-containing Diopside through a One-Step Crystallization

The incorporation of copper into pyroxene structure was investigated through the melt quenching technique and one-step crystallization procedure. Two series of glasses have been studied, one set with Ca=Mg and another set with Ca>Mg in diopside formula Cux(Ca Mg)2-xSi2O6. The glasses were nucleated by TiO2, Cr2O3, or CaF2 additions as nucleating agents to variably control the phases produced. X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the obtained samples. The heat treatment studied at 700, 800, 900 and 1000 °C for 2 h produced green and dark green glasses based on Cu-containing diopside. Various crystalline wollastonite, cuprite, tenorite, cristobalite, quartz, and fluorite phases were developed with different ratios combined with diopside formation depending on the heat treatment and nucleating agents used. As the heat treatment increased in temperature, the crystallized fraction increased with the development of nano-aggregates and the observed reticulated textures confirmed a radical change in the euhedral crystals. This emphasizes that the Cu-containing diopside can be created by a facile one step process. These compositions may find some applications in biological and optical fields.

P-n heterojunctions composed of two-dimensional molecular crystals for high-performance ambipolar organic field-effect transistors

Bilayer p-n heterojunctions are promising structures to construct ambipolar organic field-effect transistors (aOFETs) for organic integrated circuits. However, due to the lack of effective strategies for high-quality p-n heterojunctions with clear interfaces, the performance of aOFETs is commonly and substantially lower than that of their unipolar counterparts, which hinders the development of aOFETs toward practical applications. Herein, a one-step solution crystallization strategy was proposed for the preparation of high-quality bilayer p-n heterojunctions. A mixed solution of a p- and an n-type organic semiconductor was dropped on a liquid substrate, and vertical phase separation occurred spontaneously during crystallization to produce bilayer p-n heterojunctions composed of molecularly thin two-dimensional molecular crystals. Due to the clear interface of the bilayer p-n heterojunctions, the maximum mobility (average mobility) reached 1.96 cm2 V−1 s−1 (1.12 cm2 V−1 s−1) for holes and 1.27 cm2 V−1 s−1 (0.61 cm2 V−1 s−1) for electrons in ambient air. So far as we know, these values were the highest among double-channel aOFETs measured in ambient air. This work provides a simple yet efficient strategy to construct high-quality bilayer p-n heterojunctions, which lays a foundation for their application in high-performance optoelectronic devices.

One-step synthesis of hierarchical lamellar H-ZSM-5 zeolite and catalytic performance of methanol to olefin

In this paper, a hierarchical lamellar H-ZSM-5 zeolite (HLHZ) was successfully synthesized for methanol to olefin (MTO) by one-step crystallization, using urea instead of sodium hydroxide, and PEG2000 as soft-template. Urea was conducive to the formation of H-ZSM-5 zeolite directly after calcination to decomposed NH4+ into NH3 and remain H+ on the framework of ZSM-5 zeolite, thereby reducing the energy consumption caused by further ion exchange. The results showed that urea could guide the formation of b-axis-oriented lamellar H-ZSM-5 zeolite (LHZ) directly, and PEG2000 effectively guide the formation of HLHZ while reducing crystal particles size. Moreover, HLHZ exhibited longer catalytic lifetime and higher olefin selectivity. In conclusion, this work provided an energy-efficient and eco-friendly synthesis strategy, which conformed to the principles of green chemistry.

Solar Photocatalysis

Solar Photocatalysis