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1.
David A. Pacheco Tanaka Margot A. Llosa Tanco Junya Okazaki Yoshito Wakui Fujio Mizukami Toshishige M. Suzuki 《Journal of membrane science》2008,320(1-2):436-441
Mesoporous YSZ–γ-Al2O3 membranes were coated on α-Al2O3 (Ø2 mm) tube by dipping the α-Al2O3 support tube into mixed sol consists of nano-size YSZ and bohemite particles followed by drying and calcination at 600 °C. Addition of bohemite in YSZ sol helped a good adhesion and uniform coating of the membrane film onto α-Al2O3 support. The quality of the mesoporous YSZ–γ-Al2O3 membranes was evaluated by the gas permeability experiments. The number of defects was minimized when the γ-Al2O3 content became more than 40%. Addition of γ-Al2O3 inhibited the crystal growth of YSZ, sintering shrinkage and distortion stress. Increase of calcination temperature and time results in the increase of pore size and N2 permeance. A hydrogen perm-selective membrane was prepared by filling palladium into the nano-pores of YSZ–γ-Al2O3 layer by vacuum-assisted electroless plating. Crystal growth of palladium was observed by thermal annealing of the membrane at 600 °C for 40 h. The Pd–YSZ–γ-Al2O3 composite membrane revealed improved thermal stability allowing long-term operation at elevated temperature (>500 °C). This has been attributed to the improved fracture toughness of YSZ–γ-Al2O3 layer and matching of thermal expansion coefficient between palladium and YSZ. Although fracture of the membrane did not occur, decline of H2 flux was observed when the membrane was exposed in 600 °C. This has been attributed to the agglomeration of palladium particles by crystal growth and dense packing into the pore networks of YSZ–γ-Al2O3 by elevation of temperature. 相似文献
2.
Among the perovskites, the rare earth manganites find application in several electrochemical devices because of their enhanced thermodynamic stability. In this paper, we present the results obtained on the preparation and characterization of La0.95MnO3+δ and Sm0.95MnO3+δ which were prepared by the solid state and sol–gel methods. XRD characterization of the manganites indicated that the crystal structure depends on the method of preparation and heat treatments. The ratio of Mn3+ to Mn4+ in these samples also depended on the method of preparation and heat treatments, as indicated by thermogravimetric (TG) and temperature programmed reduction (TPR) studies in Ar + 5% H2 atmosphere. The standard molar enthalpy of formation, which is a measure of the thermodynamic stability of these compounds were determined using an isoperibol calorimeter. 相似文献
3.
Emanuel Postolache D. K. Powell G. Popov Ram C. Rai M. Greenblatt J. W. Brill 《Solid State Sciences》2000,2(8)
We have measured Young's modulus (using a vibrating reed technique) and the specific heat (using ac calorimetry) on the same crystals of α′-NaV2O5 at its Tc=34 K magnetic phase transition. Both properties exhibit large, unsymmetrical, and sample-dependent anomalies. While the specific heat results suggest tricritical behavior of the transition, large fluctuation effects are observed in the modulus above Tc. Fits of the modulus in terms of the specific heat, entropy, and free energy suggest that fluctuations are strongly stress- and sample-dependent. 相似文献
4.
The bulk superconducting YCa2Cu3O7−δ compounds are prepared at an ordinary pressure of oxygen by conventional solid-state reaction method. The formation of sample is tested by means of XRD and is studied for their ac susceptibility below room temperature up to 77.5 K. The samples are found single-phase orthorhombic structure and found superconducting at 83.5 K. It is shown that the analysis is consistent with published data on YBa2Cu3O7−δ oxide superconductor. 相似文献
5.
Rina Ghosh Swarupananda Maiti Arijit Chakraborty Dilip K. Maiti 《Journal of molecular catalysis. A, Chemical》2004,210(1-2):53-57
A new efficient one-pot synthesis of α-amino phosphonates derived from nitro substituted anilines, aldehydes and diethyl phosphite has been carried out by employing 5 mol% of In(OTf)3. The method is equally effective for the generation of α-amino phosphonates from various carbonyl compounds and other amines. 相似文献
6.
Kenji Ishikawa Kenji Metoki Hiroshi Miyamoto 《Journal of solid state chemistry》2009,182(8):2096-2103
Variation of the phases of Nd2NiO4+δ with the excess oxygen concentration δ has been examined at room temperature in the range 0.067≤δ≤0.224 using the X-ray powder diffraction technique. The phases observed at room temperature are orthorhombic-I (0.21<δ≤0.224), orthorhombic-IV (0.175<δ≤0.21), orthorhombic-II (0.15<δ≤0.175), orthorhombic-II+quasi-tetragonal-I (0.10<δ≤0.15), and quasi-tetragonal-I (0.067<δ≤0.10). 相似文献
7.
Evert J. Elzinga Yuanzhi Tang Jason McDonald Stephanie DeSisto Richard J. Reeder 《Journal of colloid and interface science》2009,340(2):153-159
The interaction of selenate, selenite, and chromate with the hydrated surface of γ-Al2O3 was studied using a combination of macroscopic pH edge data, electrophoretic mobility measurements, and X-ray absorption spectroscopic analyses. The pH edge data show generally increased oxyanion adsorption with decreasing pH, and indicate ionic strength-(in)dependent adsorption of chromate and selenate across the pH range 4–9, and ionic strength-(in)dependent adsorption of selenite in this pH range. The adsorption of chromate peaks at pH 5.0, whereas for selenate and selenite no pH adsorption maxima are observed. Electrophoretic mobility measurements show that all three oxyanions decrease the zeta potential of γ-Al2O3 upon adsorption; however, only selenite decreased the pHPZC of the γ-Al2O3 sorbent. EXAFS data indicate that selenite ions are coordinated in a bridging bidentate fashion to surface AlO6 octahedra, whereas no second-neighbor Al scattering was observed for adsorbed selenate ions. Combined, the results presented here show that pH is a major factor in determining the extent of adsorption of selenate, selenite, and chromate on hydrated γ-Al2O3. The results point to substantial differences between these anions as to the mode of adsorption at the hydrated γ-Al2O3 surface, with selenate adsorbing as nonprotonated outer-sphere complexes, chromate forming a mixture of monoprotonated and nonprotonated outer-sphere adsorption complexes, and selenite coordinating as inner-sphere surface complexes in bridging configuration. 相似文献
8.
Limin Song Shujuan Zhang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):217-220
A series of α-Fe2O3/FeOOH nanostructures with different morphologies have successfully been synthesized based on K4[Fe(CN)6] at 140 °C by a novel hydrothermal method. The morphology and phase of α-Fe2O3/FeOOH can be controlled by adjusting the reaction time. UV–vis absorption spectrum, X-ray powder diffraction, and transmission electron microscopy analyses were used to characterize the resulting products. A detailed, rational mechanism is proposed for the formation of α-Fe2O3/FeOOH nanostructures. The potential applications of the as-synthesized α-Fe2O3/FeOOH nanoparticles with different morphologies on photocatalytic decomposition of salicylic acid were also investigated. 相似文献
9.
The (E)-α-selenylvinylstannanes react with acyl halides in presence of a catalytic amount of Pd(PPh3)4 to give the corresponding (Z)-α-selenyl-α,β-unsaturated ketones in good yield. 相似文献
10.
Environment-friendly synthesis of N-phenylpiperidine from aniline and 1,5-pentanediol over γ-Al2O3 catalyst
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An efficient environment-friendly synthesis of N-phenylpiperidine was developed from aniline and 1,5-pentanediol over γ-Al2O3 catalyst under atmospheric pressure. The conversion of 1,5-pentanediol reached 97% and the selectivity for N-phenylpiperidine attained 94%. The structure of the catalyst was characterized by NH3-TPD and BET. The influences of calcination temperature of the catalyst and reaction temperature on activity and selectivity of the catalyst were investigated. 相似文献
11.
In this paper, we have reported the preparation of low cost γ-Al2O3 membrane on a macroporous clay support by dip-coating method. For the synthesis of γ-Al2O3 top layer on the support, a stable boehmite sol is prepared using aluminium chloride salt as a starting material by sol–gel route. The structural properties of the composite membrane as well as γ-Al2O3 powder is carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm data, Fourier transform infrared analysis (FTIR) and dynamic light scattering (DLS) analysis. The mean particle size of the boehmite sol used for coating is found to be 30.9 nm. The pore size distribution of the γ-Al2O3–clay composite membrane is found to be in the range of 5.4–13.6 nm. Separation performance of the membrane in terms of flux and rejection of single salts solution such as MgCl2 and AlCl3 as a function of pH, salt concentration and applied pressure is also studied. The rejection and flux behavior are found to be strongly dependent on electrostatic interaction between the charged molecules and γ-Al2O3–clay composite membrane. The intrinsic rejection has been determined by calculating the concentration at membrane surface (Cm) using Speigler–Kedem model. It is found that the observed rejection shows anomalous trend with increase in applied pressure and the intrinsic rejection increases with increase in applied pressure, a trend typical of the separation of electrolyte through charged membranes. At acidic pH, both the salt solution shows higher rejection. With increase in the salt concentration, observed rejection of salt decreases due to the enhanced concentration polarization. The maximum rejection of MgCl2 and AlCl3 is found to be 72% and 88%, respectively for salt concentration of 3000 ppm. 相似文献
12.
Ferroelastic β′-Gd2(MoO4)3, (GMO), crystals are formed through the crystallization of 21.25Gd2O3–63.75MoO3–15B2O3 glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50–500 μm spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called “self-powdering phenomenon during crystallization” in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO4)2− tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals. 相似文献
13.
γ-Al2O3 samples, both pure and Cr doped, were prepared by heating at 470°C sol–gel precursors obtained by using aluminum tri-sec-butoxide [Al(OC4H9)3] as the starting compound. The samples were characterised for phase composition (X-ray diffraction) and surface area (BET). Electrochemical determinations of the double layer reactivity of the pure and doped oxides were performed both by surface charge and by electrokinetic sonic amplitude (ESA) determinations. The interfacial electrostatic response is discussed and analysed also with reference to the sample surface state obtained by X-ray photoelectron spectroscopy (XPS). 相似文献
14.
Hanping Ding Bin Lin Xingqin Liu Guangyao Meng 《Electrochemistry communications》2008,10(9):1388-1391
Protonic ceramic membrane fuel cells (PCMFCs) based on proton-conducting electrolytes have attracted much attention because of many advantages, such as low activation energy and high energy efficiency. BaZr0.1Ce0.7Y0.2O3−δ (BZCY7) electrolyte based PCMFCs with stable Ba0.5Sr0.5Zn0.2Fe0.8O3−δ (BSZF) perovskite cathode were investigated. Using thin membrane BZCY7 electrolyte (about 15 μm in thickness) synthesized by a modified Pechini method on NiO-BZCY7 anode support, PCMFCs were assembled and tested by selecting stable BSZF perovskite cathode. An open-circuit potential of 1.015 V, a maximum power density of 486 mW cm−2, and a low polarization resistance of the electrodes of 0.08 Ω cm2 was achieved at 700 °C. The results have indicated that BZCY7 proton-conducting electrolyte with BSZF cathode is a promising material system for the next generation solid oxide fuel cells. 相似文献
15.
Shijing Zhan Xuefeng Zhu Baofeng Ji Weiping Wang Xiaoliang Zhang Jibo Wang Weishen Yang Liwu Lin 《Journal of membrane science》2009,340(1-2):241-248
Asymmetrical thin membranes of SrCe0.95Y0.05O3−δ (SCY) were prepared by a conventional and cost-effective dry pressing method. The substrate consisted of SCY, NiO and soluble starch (SS), and the top layer was the SCY. NiO was used as a pore former and soluble starch was used to control the shrinkage of the substrate to match that of the top layer. Crack-free asymmetrical thin membranes with thicknesses of about 50 μm and grain sizes of 5–10 μm were successfully pressed on to the substrates. Hydrogen permeation fluxes (JH2) of these thin membranes were measured under different operating conditions. At 950 °C, JH2 of the 50 μm SCY asymmetrical membrane towards a mixture of 80% H2/He was as high as 7.6 × 10−8 mol/cm2 s, which was about 7 times higher than that of the symmetrical membranes with a thickness of about 620 μm. The hydrogen permeation properties of SCY asymmetrical membranes were investigated and activation energies for hydrogen permeation fluxes were calculated. The slope of the relationship between the hydrogen permeation fluxes and the thickness of the membranes was −0.72, indicating that permeation in SCY asymmetric membranes was controlled by both bulk diffusion and surface reaction in the range investigated. 相似文献
16.
Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds
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Abdolali Alizadeh Seyed Yasub Hosseini Hadi Sedighian Fahimeh Bayat 《Helvetica chimica acta》2015,98(10):1426-1434
Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1). 相似文献
17.
3, 5-Dimethyl-4-carbethoxy-2-cyclohexen-1-one has been synthesized through the Knoevenagel condensation1, which is then subjected to alkylation and acylation at α-position. The resulting products are hydrolyzed and decarboxylated to α-substituted cyclohexenones. 3, 5-Dimethyl-2-cyclohexen-1-one is converted by N-bromosuccinimide to phenol via enolization2. 相似文献
18.
Srikant Bhagat Ratnesh Sharma Asit K. Chakraborti 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):235-240
Commercially available lithium hydroxide monohydrate (LiOH·H2O) was found to be a novel ‘dual activation’ catalyst for tandem cross-aldol condensation between cyclic/acyclic ketones and aromatic/heteroaromatic/styryl/alkyl aldehydes leading to an efficient and easy synthesis of α,α′-bis(aryl/alkylmethylidene)ketones at r.t. in short times. The reaction of aryl, heteroaryl, styryl and alkyl aldehydes with acyclic and five/six-membered cyclic ketones afforded excellent yields after 2 min to 1.25 h. The reaction conditions were compatible with various electron withdrawing and electron donating substituents, e.g. Cl, F, NO2, OMe and NMe2. The rate of the cross-aldol condensation was influenced by the nature of the ketone and electronic and steric factors associated with the aldehyde. The reaction took place at a faster rate for acyclic ketone (e.g., acetone) than that for cyclic ketone (e.g., cyclohexanone). In case of cycloalkanones, the rate of the reaction was dependent on the size of the ring of the cycloalkanone. The cross-aldol condensation of cyclopentanone was faster than that of cyclohexanone for a common aldehyde. In case of reactions involving aliphatic aldehyde having α-hydrogen atom no self-aldol condensation of the aldehyde took place. 相似文献
19.
Francine Novack Victoria Ctia S. Radatz Maraisa Sachini Raquel G. Jacob Gelson Perin Wladimir P. da Silva Eder J. Lenardo 《Tetrahedron letters》2009,50(49):6761-6763
2-Phenylseleno aldehydes and ketones were selectively obtained using solid-supported catalyst (KF/Al2O3) and PEG-400 as clean, recyclable medium in good to excellent yields. The method was applied in the preparation of highly functionalized 2-phenylseleno citronellal and citronellol, potential bactericide agents. The catalytic system KF/Al2O3 and PEG-400 can be re-used for four times without previous treatment. 相似文献
20.
D. Kubala E.A. Drage A.M.E. Al-Faydhi J. Ko
íek P. Papp V. Matej
ík P. Mach J. Urban P. Limo-Vieira S.V. Hoffmann . Matej
ík N.J. Mason 《International journal of mass spectrometry》2009,280(1-3):169
We have performed a coordinated set of experiments to measure the electron impact ionisation and UV photoabsorption cross sections of α- and β-pinene. The adiabatic ionisation energies of α- and β-pinene were derived from experiment and found to be 8.3 and 8.6 eV which compared well with high-level quantum chemical calculations (G3MP2) yielding values of 8.29 and 8.41 eV. Additionally, vertical ionisation energies of 8.62 and 8.96 eV were calculated using an OVGF method. UV photoabsorption cross sections were measured using a high-resolution synchrotron radiation source and electronic states interpreted on the basis of the TD quantum chemical methods. 相似文献