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11.
Samples of Sn4+-substituted bismuth vanadate, formulated as Bi4Sn x V2? x O11?( x /2)? δ in the composition range 0.07 ≤ x ≤ 0.30, were prepared by standard solid-state reactions. Sample characterization and the principal phase transitions (α ? β, β ? γ and γ′ ? γ) were investigated by FT-IR spectroscopy, X-ray powder diffraction, differential thermal analysis (DTA) and AC impedance spectroscopy. For composition x = 0.07, the α ? β and β ? γ phase transitions were observed at temperatures of 451 and 536°C, respectively. DTA thermograms and Arrhenius plots of conductivities revealed the γ′ ? γ phase transition at 411 and 423°C for x = 0.20 and 0.30, respectively. AC impedance plots showed that conductivity is mainly due to the grain contribution, which is evident in the enhanced short-range diffusion of oxide ion vacancy in the grains with increasing temperature. The highest ionic conductivity (5.03 × 10?5 S cm?1 at 300°C) was observed for the x = 0.17 solid solution with less pronounced thermal hysteresis. 相似文献
12.
《Solid State Ionics》2006,177(3-4):269-274
Alkaline earth substituted UO2 (U1 − xMxO2 ± δ; M = Mg, Ca, Sr; 0.1 ≤ x ≤ 0.525) with fluorite structure was synthesized in reducing atmosphere. Structure and conductivity properties of U1 − xMxO2 ± δ fluorites were investigated for possible application in solid oxide fuel cells (SOFC). At room temperature and ambient atmosphere the materials are stable; however they decompose at an oxygen partial pressure pO2 > 10− 4 atm and temperatures higher than 600 °C. The total conductivity measured for the best conducting U1 − xMxO2 ± δ material with M = Ca and x = 0.177 is as high as 3 S/cm at pO2 < 10− 4 atm at 600 °C. The relatively low ionic transference number (ti∼0.02) is disadvantageous for potential use as electrolyte material for SOFC applications. The high conductivity and possible depolarization effects suggest potential use as anode materials in SOFC. 相似文献
13.
Hang Xu Shi-Jun Liao Xiang-Cheng You 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):1152-1156
In this paper, the time fractional partial differential equations are investigated by means of the homotopy analysis method. This technique is extended to study the partial differential equations of fractal order for the first time. The accurate series solutions are obtained. This indicates the validity and great potential of the homotopy analysis method for solving nonlinear fractional partial differential equations. 相似文献
14.
Remon M. Zaki Adel M. Kamal El-Dean Shaban M. Radwan Mokhtar A. Abd ul-Malik 《中国化学会会志》2020,67(4):658-673
In the present investigation, a simple and straightforward methodology for the preparation of novel bifunctional thienopyrazolopyrazines 4a–d has been reported. Synthesis of thieno or furopyrazolopyrazines 5a , b , e , f was achieved by the reaction of o-amino-esters 4a , b , e , f with 2,5-dimethoxytetrahydrofuran. The latter pyrrolyl derivatives 5a , b , e , f were used as starting intermediates for the synthesis of new pyrimido, pyrido, and pyrazino heterocycles fused to the thieno or furopyrazolopyrazine moiety. Furthermore, alkaline hydrolysis of the o-amino-ester 4a followed by acidification afforded the corresponding o-amino carboxylic acid 15 , which was used as a versatile precursor for the synthesis of other heterocyclic compounds fused to the thienopyrazolopyrazine ring system, namely: pyrimidine, oxazine, oxazepine, and pyridine derivatives 16–23 . The chemical structures of the synthesized compounds were confirmed on the basis of elemental and spectral analyses (Fourier-transform infrared spectroscopy [FT-IR], 1H nuclear magnetic resonance [NMR], and mass spectroscopy [MS] in addition to 13C NMR for some of them). Moreover, from the biological screening, we found that most of the tested compounds exhibited promising antifungal, antibacterial, and anti-inflammatory activities compared with the corresponding reference drugs. 相似文献
15.
Gamil A.A. Al-Hazmi Khlood S. Abou-Melha Nashwa M. El-Metwaly Ismail Althagafi Fathy Shaaban Marwa G. Elghalban Mohammed M. El-Gamil 《应用有机金属化学》2020,34(3):e5408
Trivalent Cr (III) and divalent of both Mn (II) and Cu (II) complexes containing hydrazone ligands derived from the condensation of picolinohydrazide with O-vanillin were synthesised and characterized by elemental analysis, spectral and magnetic measurements. The suggested octahedral structures were confirmed by applying DFT optimization and conformational studies. The thermal decomposition behaviour of Mn (II) complex is discussed. The evaluation of kinetic parameters (Ea, A, ∆H, ∆S and ∆G) of all thermal degradation stages have been evaluated using Coats-Redfern and Horowitz-Metzger approaches. The band gap results suggested that these complexes are semi-conductors and lie in same range of highly efficient photovoltaic materials. Antibacterial studies showed that higher activity of complexes than of ligands. Assay on the antioxidant activity (DPPH and SOD) of the above complexes revealed the high SOD-activity of Mn (II) complex and high DPPH-activity for ligand. 相似文献
16.
Ahmed S. N. Al-Kamali 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1812-1824
The alkylation of 4-cyano-5,6-dimethylpyridazin-3(2H)-thione 3 with some halo compounds gave the S-alkylated products 4a–c , which upon treatment with ethanolic sodium ethoxide afforded the cyclized thienopyridazines 5a–c as products. Pyridazothienotriazines 6a–c were prepared by the treatment of compounds 5a–c with nitrous acid, while their reaction with triethyl orthoformate and with carbon disulfide gave the corresponding pyrimidothienopyridazines 7a–c , and 8a–c , respectively. S-alkylated products 9a–o were obtained by the reaction of 8a–c with some halo compounds. 相似文献
17.
《Tetrahedron letters》1988,29(46):5949-5952
A novel oxidative ring-opening reaction of isoxazolidines upon treatment with an electrophile and subsequently with a basegives β-amino ketones and β-amino acid esters highly efficiently. 相似文献
18.
Shijun Liao 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):983-997
We describe, very briefly, the basic ideas and current developments of the homotopy analysis method, an analytic approach to get convergent series solutions of strongly nonlinear problems, which recently attracts interests of more and more researchers. Definitions of some new concepts such as the homotopy-derivative, the convergence-control parameter and so on, are given to redescribe the method more rigorously. Some lemmas and theorems about the homotopy-derivative and the deformation equation are proved. Besides, a few open questions are discussed, and a hypothesis is put forward for future studies. 相似文献
19.
Fabrication and characterization of polymer thermo-optic switch based on mmi coupler 总被引:2,自引:0,他引:2
Abdulaziz M. Al-hetar Abu Bakar Mohammad Zaid A. Shamsan 《Optics Communications》2011,284(5):1181-1185
The 2 × 2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of −36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch. 相似文献
20.
《Tetrahedron letters》1987,28(46):5635-5636
The preparation of methylene-1, 3-diselenole and its ready conversion to TSeF are discussed. 相似文献