Influence Of Crystallization Temperature Research Articles

Synthesis and Characterization of Multistage Porous Sodalite Nanocrystal Aggregate

Using the mixed solution of [Formula: see text]-butanol and ethanol as solvent, the sodalite nanocrystal aggregate was prepared by the solvothermal method. The influences of crystallization temperature, molar ratio Na/Al, crystallization time and silane concentration on the morphology, crystallite size, degree of crystallization and pore structure of the as-prepared samples were investigated by X-ray diffraction (XRD), BET, FTIR, Transmission Electron Microscopy (TEM) and scanning electron microscope (SEM). The results reveal that the sodalite nanocrystals are aggregated by self-assembly into the micropore–mesopore–macropore structure. Higher crystallization temperature and longer crystallization time are conducive to the growth of sodalite nanocrystals. It is a necessary condition for the formation of sodalite nanocrystals to keep high molar ratio Na/Al. The higher the molar ratio Na/Al, the more favorable the crystallization of sodalite nanocrystals. The appropriate concentration of silane agent is conducive to the preparation of smaller crystal-sized sodalite nanocrystals. After removing the silane agent by pickling, the sodalite nanocrystal aggregate is a multistage porous structure with the pore volume of 1.0133[Formula: see text]mL/g and the specific surface area of 449.73[Formula: see text]m2/g.

Efficient and controllable synthesis of zeolite Beta nanospheres and hollow-boxes using a temperature-sensitive bifunctional additive

Zeolite Beta nanospheres and hollow-boxes are successfully obtained through a simple one-pot hydrothermal crystallization route, using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) assisted with a temperature-sensitive bifunctional additive N-methyl-2-pyrrolidone (NMP). The influences of crystallization temperature, Si/Al ratio, and TEAOH content on the synthesis and physicochemical properties of zeolite Beta as well as the formation of hollow structure are investigated in detail. It reveals that the role of NMP changes from “crystallization promoter” (CP) to “hollow-directing agent” (HDA). And the acceleration effect of NMP decreases upon the crystallization temperature (120–160 °C) due to the decomposition of TEAOH. Meanwhile, high synthesis temperature (≥180 °C), high Si/Al ratio (≥30), and low TEAOH content (TEAOH/SiO2 ≤ 0.2) may lead to the formation of undesired zeolites ZSM-5 and/or ZSM-12. The obtained Beta nanosphere and hollow-box catalysts exhibit excellent catalytic activity in the degradation of low-density polyethylene (LDPE) due to their high external surface area and acid density.

Influences of crystallization temperature on the structure, dielectric, and energy storage characteristics of KBaSrNb5O15‐based glass–ceramics

AbstractGlass–ceramics capacitors have great application potential in pulsed power systems, due to ultrafast discharge speed and high dielectric breakdown strength (BDS). Here, lead‐free niobate glass–ceramic dielectric materials were synthesized, and the effects of heat treatment temperature on the dielectric, ferroelectric, and energy storage properties of glass–ceramics were investigated comprehensively. The results exhibit that the dielectric permittivity first increases and then decreases as the crystallinity increases; however, the dielectric BDS diminishes. At the optimum crystallization temperature of 740°C, the maximum value of discharge energy density is 2.2 J/cm3 at 600 kV/cm, which is about 7.6 times that of mother glass. Furthermore, an ultrahigh power density of about 380.9 MW/cm3 and ultrafast discharge speed of about 11.2 ns were achieved simultaneously. Meanwhile, great thermal stability of charge–discharge property was verified in this glass–ceramics. According to P–E loops and dielectric test result, a high dielectric constant (∼207) and low dielectric loss (<0.005) as well as high energy storage efficiency of about 94.9% were achieved for G740 sample. The previous results make the obtained glass–ceramic as potential candidates in dielectric capacitors.

Comparison of Paliperidone Palmitate from Different Crystallization Processes and Effect on Formulations In Vitro and In Vivo.

The quality of active pharmaceutical ingredients (APIs) is an important factor which can affect the safety and efficacy of pharmaceuticals. This study was designed to investigate the nature of paliperidone palmitate (PP) obtained by different crystallization processes, then compare the characteristics between test formulations which prepared PP of different crystallization and reference formulations (Invega Sustenna®) in vitro and in vivo. Two different PPs, namely PP-1 and PP-2, were prepared by different crystallization methods. Contact angle, morphology, and crystallinity of the PPs were characterized. Taking the particle sizes and distribution of Invega Sustenna® as reference, test formulations were prepared by the wet milling method using either a PP-1 or PP-2 sample. Their release behavior, stability in vitro, and pharmacokinetics in vivo were subsequently investigated. The results indicated that PP-2 had a higher surface free energy (SFE). More small particles were attached to the PP-1 surface under the influence of crystallization temperature. Different crystallization processes did not change the crystal of PP, but changed the crystallinity of PP. There was no obvious difference in in vitro releases between test formulations. However, the stability and state of formulation containing PP-2 were better compared to formulations containing PP-1, indicated by differences in crystallinity and SFE. Meanwhile, pharmacokinetic in vivo results demonstrated that the pharmacokinetic profiles and parameters of formulation containing PP-2 and Invega Sustenna® tended to be consistent, but those of formulations containing PP-1 were significantly different from those of formulations containing PP-2 or Invega Sustenna®, and there was burst release phenomenon of formulations containing PP-1 in rats. PP made by different crystallization processes could induce changes in appearance, SFE, and crystallinity, and further affect the stability, state, and pharmacokinetic in vivo formulation.

Recovery of Lanthanum from Aqueous Solutions by Crystallization as Lanthanum Sodium Sulfate Double Salt

The recovery of rare earth elements from spent nickel-metal hydride batteries by hydrometallurgical processing has become increasingly important in recent years. The present work investigated the effect of temperature, systems of adding the reactant, the molar ratio of sodium and lanthanum, and the initial concentration of six sulfate impurities (Ni, Co, Al, Mn, Fe, and Zn) on the crystallization of the monohydrate of sodium lanthanum sulfate double salt (NaLa(SO4)2·H2O) crystals from synthetic leachate solutions. The sodium sulfate reactant was added as an acidic solution by pumping or batchwise as a solid anhydrate salt to a pregnant lanthanum sulfate solution. Compared to precipitation with acidic sodium sulfate solution, precipitation with solid sodium sulfate yielded smaller single crystals, a greater tendency to form aggregates, and lower crystal purity. The lowest overall impurity and highest lanthanum quantity in crystals were obtained by semi-batch reactant adding performance of Na2SO4 solution at 70°C with Na/La molar ratio of 3. Real-time monitoring of the count rates of different chord length fractions clearly showed the influence of crystallization temperature on the precipitation kinetics.

ROPs of l-lactide catalyzed by neat Tin(II)2-ethylhexanoate - Influence of the reaction conditions on Tm and ΔHm

l-Lactide was polymerized by means of neat SnOct2 with variation of LA/Cat ratio, temperature and time. The resulting cyclic polylactides crystallized spontaneously at 160 °C or below, but needed nucleation via mechanical stress at 165 or 170 °C. All the crystalline polylactides obtained directly from ROP above 120 °C had melting temperatures (Tm) above 189 °C (up to 194.5 °C). SnOct2 also enabled transformation of low Tm poly(l-lactide)s (Tm < 180 °C) into the high Tm m1odification by annealing, due to the impact of transesterification reactions in the interphase between the crystallites. The influence of crystallization temperature and annealing time on the crystal thickness was studied via SAXS measurements. A comparison with the crystallization and annealing experiments reported by Pennings and coworkers and Tsuji and Ikada is discussed, and a satisfactory agreement has been found, because those authors also studied polyLA samples containing SnOct2 in its active form. It is also demonstrated in this work that the high Tm modification cannot be obtained when the catalyst is removed or poisoned as it is true for commercial polylactides.

Influence of crystallization temperature and atmosphere on the phase composition, microstructure and electrical properties of Ni–Mn–O thin films

Nickel manganite thin films were prepared by chemical solution deposition from nitrate and acetate precursors on polished alumina substrates. By variation of crystallization temperature between 650 ​°C and 900 ​°C and atmosphere during cooling of the films, the morphology, phase formation and electrical properties of the films were investigated. The electrically conductive spinel phase was formed as a main phase independent of processing conditions exhibiting NTCR characteristics. Cooling down in nitrogen atmosphere favored the decomposition of the spinel phase into nickel oxide and a spinel phase with higher manganese content, but it also reduced the resistance drift of the samples. From this finding it can be deduced that a reduced oxygen partial pressure influences defect equilibria and by that decreases cation vacancy concentration. This supports the assumption that cation redistribution by a cation vacancy diffusion mechanism is a relevant mechanism of resistance drift in such thin films.

Improvement of bi-layered YBCO superconducting films by using Ag and Au interlayers

Chemical solution deposition is a promising technology to fabricate YBCO superconducting thin films due to its low-cost advantage. However, the decreasing of critical current density (Jc) usually occurred in the fabrication of multi-layered YBCO films. In this study, Ag and Au heterogeneous interlayers were fabricated by using sputtering deposition in order to improve the bi-layered YBCO films, and the influence of crystallization temperature from 740 ∘C to 800 ∘C was investigated. It was found that Jc could be enhanced by both interlayers relative to the counterparts without interlayers, and the effect of Ag interlayer was superior to that of Au interlayer. When the crystallization temperature was 800 ∘C, the optimal sample with Ag interlayer had a Jc 3.65 MA/cm2, which was about twice of the Jc of its counterpart. The surface morphologies and cross-sections were observed by using scanning electron microscope, and the content variations of c-axis oriented grains were measured by using Raman spectroscopy, which could help to investigate the influences of interlayers on the microstructure of YBCO films. The possible reasons for the improvement effects of Ag and Au interlayers were discussed based on the experimental results.

Effect of CaCN2 on the preparation of CaAlSiN3 :Eu2+ phosphors.

Highly efficient red-emitting phosphors, CaAlSiN3 :Eu2+ , were successfully prepared by the solid-state method using calcium cyanide (CaCN2 ) as the single calcium source. The influences of crystallization temperature, crystallization time, calcination mode and compounds ratio on the photoluminescent properties were investigated. The CaAlSiN3 :Eu2+ phosphors were obtained with 1mol% CaCN2 by a two-step calcination procedure at 900°C for 2h and subsequently at 1600°C for 8h. The CaAlSiN3 :Eu2+ phosphors showed the strongest luminescent intensity at 660nm when excited by 468nm. With an increase in crystallization time, the maximum wavelength of the emission was shifted from 644nm to 660nm.

Size-controlled synthesis of hierarchical ferrierite zeolite and its catalytic application in 1-butene skeletal isomerization

Nano-ferrierite zeolite aggregates with hierarchical porosity were successfully prepared by using pyrrolidine as sole organic structure-directing agent. SEM and TEM images revealed that nano-sized crystals (40–60 nm) stacked together loosely to form irregular clusters. Influence of crystallization temperature and initial gel compositions (pyrrolidine content, alkalinity, water content) on the synthesis of ferrierite zeolite were investigated in detail. Low crystallization temperature and high alkalinity were beneficial to form nano-ferrierite zeolite aggregates with high hierarchical porosity (total pore volume: 0.461 cm3/g). Compared with commercialized ferrierite zeolite, hierarchical nano-ferrierite aggregates showed better catalytic stability and product selectivity in the 1-butene skeletal isomerization reaction.

How temperatures affect the number of dislocations in polymer single crystals

The influence of crystallization temperature (Tc) on the number of spiral growths on poly(butylene succinate) (PBS) single crystals, obtained by self-seeding method, was systematically studied. The studies show that the statistical average number of spiral growths formed on the PBS single crystals decays exponentially with respect to the Tc. Inspired by BCF (Bruton, Cabrera and Frank) theory and L-H (Lauritzen and Hoffman) theory, a thermodynamic model has been proposed, in which the origin of spiral growth was treated as a nucleation process. The model suggests that the nucleation rate of spiral growth depends on the inverse square of super-cooling degree, which predicted the density of spiral growth formed on lamellae, and was consistent with the experiments very well.

Temperature Dependence of Morphology of Transcrystalline at the Interface of Carbon Fiber and Poly (L‐Lactic Acid) Composite Under a Temperature Gradient Stage

SummaryThin film of carbon fiber (CF) and poly (L‐lactic acid) (PLLA) composite was prepared by a solution casting technique. Influence of crystallization temperature (Tc) on morphology of transcrystalline (TC) on the interface between CF and PLLA was investigated under a temperature‐controlled gradient (T‐gradient) stage with temperature ranging from 90 °C to 140 °C. Morphology of TC was observed by polarized optical microscope (POM). Typical TC structure isothermally crystallized on the T‐gradient stage was obtained at the surface of CF when Tc = 111 ∼ 132 °C. As Tc decreased from 132 to 111 °C, nuclei density on the surface of single fiber increased while the thickness of TC layer decreased. Crystallization kinetics of TC was investigated through isothermal crystalization under POM equipped with a temperature‐controlled stage. As Tc decreased, the nucleation rate of TC increased and the growth rate of TC decreased. Furthermore, it revealed that the thickness of TC layer was conducted by the competition between heterogeneous nucleation on the surface of fiber and homogeneous nucleation in the bulk matrix around the fiber. The nucleation rate of TC structure was much higher than homogeneous nucleation rate of spherulites in the bulk matrix when Tc was above 118 °C. In this case, TC had enough space to develop perpendicular to fiber axis. Consequently, thickness of TC layer was larger at higher crystallization temperature. On the contrary, transcrystallization was suppressed by homogeneous crystallization when Tc was below 118 °C due to enhanced nucleation ability of spherulites.

BaHfO3 artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films

Chemical solution deposition (CSD) is a promising way to realize REBa2Cu3O7−x (REBCO; RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO—e.g. by inductive critical current densities, Jc, at self-field and 77 K. YBCO is outperformed by more than 1 MA cm−2 with Jc values of up to 5.0 MA cm−2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field Jc measurements demonstrate high pinning force maxima of around 4 GN m−3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent Jc measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.

Influence of crystallization temperature on ionic conductivity of lithium aluminum germanium phosphate glass-ceramic

NASICON-structured Li1.5Al0.5Ge1.5(PO4)3 glass-ceramic is successfully fabricated through melt-quench with post-crystallization. The influence of crystallization temperature on structure and ionic conductivity is studied using X-ray diffraction, nuclear magnetic resonance and impedance analysis, revealing that the Li ion mobility is closely related with crystallization temperature that in turn affects the bulk conductivity. Scanning electron microscopy reveals a progress of transformation from an amorphous phase to a crystalline, and grain growth during the annealing. It is shown that crystallization temperature plays an important role in controlling the ionic conductivity. The highest conductivity of 2.25 × 10−3 S cm−1 with an activation energy of 0.29 eV at room temperature has been obtained for the glass-ceramic specimen crystallized at 825 °C for 8 h.

Highly crystalline binder-free ZSM-5 granules preparation

A new environmental friendly technology was developed for the preparation of highly crystalline binder-free zeolite ZSM-5 granules. It comprises a preparation of amorphous aluminosilicate granules by using inexpensive industrial reactants like sodium water glass and sodium aluminate without the use of organic structure directing agents. Dried aluminosilicate gel was compacted in granules by using sodium water glass as a “pseudo-binder”. Zeolite ZSM-5 granules were prepared by hydrothermal crystallization at 180 °C after 24 h by using lifted set-up reactor in 0.01 M NaOH comprising 10 wt% of amorphous aluminosilicate granules. The influence of crystallization temperature and time, SiO2/Al2O3 molar ratio of reactants and relationship between the amount of amorphous aluminosilicate granules and NaOH medium during hydrothermal treatment on the crystallization process of granulated ZSM-5 product were monitored and characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscope, and N2 physisorption technique. The presented procedure enabled more than doubled increase of the synthesis product yield, which positively impacts the economy and ecology of the production process.

Influence of Crystallization Temperature on Crystal Size and Morphology in the Synthesis of Zeolite NaX

Influence of Crystallization Temperature on Crystal Size and Morphology in the Synthesis of Zeolite NaX

The Role of the Crystallization Temperature on the Nanophase Structure Evolution of Poly[(R)-3-hydroxybutyrate

The nanophase structure of semicrystalline polymers, which determines the mechanical, thermal, and gas permeability behavior, can be quantified by thermal methods. A detailed investigation of the nanophase structure of poly[(R)-3-hydroxybutyrate] (PHB) was performed under conditions of isothermal, quasi-isothermal, and nonisothermal crystallizations. The experimental analyses revealed that the establishment of the nanophase rigid amorphous fraction (RAF) in PHB depends on the temperature at which crystallization occurs. The RAF grows in parallel with the crystal phase during quasi-isothermal crystallization at 30 °C, whereas during nonisothermal crystallization at higher temperatures, RAF starts to develop at 70 °C, in correspondence with the final stages of the crystallization process. The influence of crystallization temperature on the nanophase structure was rationalized taking into account the effect of the mobility of the entangled chain segments during the phase transition. The melting behavior was found to change after isothermal crystallization at 70 °C, revealing that complete RAF mobilization is achieved approximately at this temperature. The temperature of 70 °C could be the limit for the formation and the disappearance of rigid amorphous fraction in the PHB analyzed in the present study.

Synthesis and Characterization of Monodisperse Nanocrystalline HZSM-5 Zeolite

A monodisperse nanocrystalline HZSM-5 zeolite was prepared by varying-temperature synthesis method with aluminum nitrate (Al (NO3)3), tetraethyl orthosilicate (TEOS), and tetrapropyl ammonium hydroxide (TPAOH) as raw materials. X-ray diffraction (XRD) characterization results showed that the crystallinity of HZSM-5 prepared by varying-temperature synthesis method was higher than constant-temperature synthesis . The influence of crystallization temperature and time on morphology and particle size of HZSM-5 is represented by scanning electronic microscopy (SEM) characterization: nanocrystalline HZSM-5 with more regular morphology and smaller particle size can be prepared by varying-temperature synthesis method. The minimum average particle size is 0.3μm. The particle size will grow up to 3.0μm with the crystallization time prolonged.

Influences of Crystallization Temperature and Slurry Concentration on Stress of PZT Thick Film Prepared by a Modified Sol-Gel Method

As a key MEMS transducer materials, PbZr0.52Ti0.48O3(PZT) piezoelectric thick film should have good piezoelectric properties as well as lower stress. But now few studies on PZT film stress were carried out. The PZT thick films are deposited by a modified sol-gel method, and the influences of crystallization temperature and slurry concentration on stress are investigated in this paper. The result shows that the PZT thick film stress is tensile stress about 100-1000Mpa. With crystallization temperature increasing, thermal stress increases gradually. The stress increases about 3.5 times as the crystallization temperature rises from 600°C to 700°C. With powder concentration of slurry increasing, the stress of PZT thick film becomes smaller. The stress decreases about 7 times as powder concentration of slurry increasing from 1:4.5 to 1:3.5. The relationship between stress of PZT thick films and crystallization temperature is simulated by using the finite element method, and the results of simulation agree well with the experimental results.

Preparation of hollow ZSM-5 crystals in the presence of polyacrylamide

Hollow ZSM-5 crystals were successfully synthesized through a simple one-step hydrothermal crystallization method in the presence of polyacrylamide (PAM) as template. The influences of crystallization temperature, PAM concentration, and the type of PAM on the morphology and pore structure of hollow ZSM-5 zeolite as well as the stability and formation mechanism of hollow structure were investigated. Hollow ZSM-5 crystals could be synthesized by adding three types of PAM with different surface groups. Crystallization temperature and PAM concentration played crucial roles in the formation of hollow ZSM-5 crystals. Low crystallization temperature or high PAM concentration was beneficial for the formation of hollow ZSM-5 crystals with embedded large voids in the framework structure. Egg-shell like hollow ZSM-5 crystals formed with less amount of PAM at high temperature due to the decomposition of the PAM network. Moreover, the surface walls of those hollow ZSM-5 crystals possessed microporous crystalline framework. Hollow ZSM-5 crystals exhibited good thermal and hydrothermal stability, and anti-pressure ability. ZSM-5 crystallization in the presence of PAM was in good agreement with the surface-to-core crystallization process. The fast growth of ZSM-5 nuclei on the surfaces of PAM hydrogel resulted in the formation of single crystals with hollow structure after they consumed the synthesis gel and ZSM-5 nuclei in the PAM hydrogel network.