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31.
Spinel systems with the composition of Cu1−xZnxCr2O4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation
method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface
area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as
oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to
cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h. 相似文献
32.
R.P. Pant Manju Arora Balwinder Kaur Vinod Kumar Ashok Kumar 《Journal of magnetism and magnetic materials》2010,322(22):3688-3691
Nanoparticles of CoGdxFe2−xO4 (where x=0.0, 0.1, 0.3, 0.5) series have been prepared by chemical co-precipitation. The effect of Gd3+ ion concentration on crystalline phase, crystallinity, crystallite size, molecular vibrations and magnetic resonance has been investigated in detail. The crystallinity decreases with an increase in Gd3+ ion concentration and changes the structural parameters. The spin lattice relaxation has been correlated with the doping ion concentration. Similarly, the superparamagnetic behavior of these particles has been observed with EPR spectroscopy. 相似文献
33.
A new active layer for CO2 sensing based on semiconducting CuO-CuxFe3−xO4 (with 0 ≤ x ≤ 1) nanocomposite was prepared by radiofrequency sputtering from a delafossite CuFeO2 target using a specific in situ reduction method followed by post annealing treatment in air. The tenorite-spinel ferrite nanocomposite layer was deposited on a simplified test device and the response in a carbon dioxide atmosphere was measured by varying the concentration up to 5000 ppm, at different working temperatures (130-475 °C) and frequencies (0.5-250 kHz). The results showed a high response of 50% (Rair/RCO2=1.9) at 250 °C and 700 Hz for a CO2 concentration of 5000 ppm. 相似文献
34.
J.L. Gunjakar 《Applied Surface Science》2008,254(18):5844-5848
The present investigation is related to the deposition of single-phase nano-sheets spinel nickel ferrite (NiFe2O4) thin films onto glass substrates using a chemical method. Nano-sheets nickel ferrite films were deposited from an alkaline bath containing Ni2+ and Fe2+ ions. The films were characterized for their structural, surface morphological and electrical properties by means of X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and two-point probe electrical resistivity techniques. The X-ray diffraction pattern showed that NiFe2O4 nano-sheets are oriented along (3 1 1) plane. The FT-IR spectra of NiFe2O4 films showed strong absorption peaks around 600 and 400 cm−1 which are typical for cubic spinel crystal structure. Microstructural study of NiFe2O4 film revealed nano-sheet like morphology with average sheet thickness of 30 nm. The room temperature electrical resistivity of the NiFe2O4 nano-sheets was 107 Ω cm. 相似文献
35.
Sheikdawood Parveen Thathan Premkumar Subbiyan Poornima Subbiah Govindarajan 《Journal of Saudi Chemical Society》2019,23(6):691-701
Metal complexes ([ML2], where M = Fe, Co, or Zn; HL = 2-[(6-ethyl-5-oxo-4,5-dihydro-2H-[1,2,4]triazin-3-ylidene)-hydrazono]-butyric acid, C9H13N5O3) of a Schiff base derived from α-ketobutyric acid (α-KBA) and diaminoguanidine (Damgu) were synthesized and characterized using elemental, spectral, and thermal studies. The metal complexes exhibited similar decomposition behavior, with a highly exothermic final decomposition step resulting in the formation of metal oxides. Isomorphism among the complexes was revealed using a powder X-ray diffraction (PXRD) technique. Solid solution precursors ([Zn1/3M2/3(L)2], where M = Fe, Co) were synthesized and characterized using various physico-chemical techniques. A thermal decomposition technique was used to prepare spinel-type zinc cobaltite (ZnCo2O4) and zinc ferrite (ZnFe2O4) nanocrystalline particles with the synthesized single source precursors. Structural studies using PXRD ascertained the predominant crystal phase to be spinel. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) showed a mean nanoparticle size of 18 ± 2 nm. Magnetic measurements revealed a weak magnetic behavior in the synthesized spinels. In the aqueous phase, the spinels exhibited catalytic activity, reducing 4-nitrophenol (4-NP) in the presence of NaBH4 at room temperature. Additionally, the study demonstrated that the catalyst can be recovered and reused for five cycles with a more than 85% conversion efficiency. 相似文献
36.
Abdülhadi Baykal Nermin Kasapoğlu Yüksel Köseoğlu Ali Cemil Başaran Hüseyin Kavas Muhammet S. Toprak 《Central European Journal of Chemistry》2008,6(1):125-130
A series of Ni-doped cobalt ferrites NixCo1−xFe2O4 (x = 0.0, 0.4, 0.6, 0.8, and 1.0) were prepared using microwave-induced combustion. Nickel, cobalt, and ferric nitrates were
used as starting materials and glycine as fuel. The influence of Ni content on the lattice parameter, stretching vibrations,
and magnetization was studied. XRD, FTIR, and SEM were used for structure, composition, and morphology investigation. A porous
network structure was observed with average particle size 60–67 nm. All samples had a cubic spinel structure. The unit cell
parameter “a” decreases linearly with nickel concentration due to the smaller ionic radius of nickel. Magnetization measurements
showed that coercivity decreased as Ni content increased; it increased with decreasing temperature.
相似文献
37.
利用化学沉淀法和溶胶凝胶法,通过两步法成功制备出含有尖晶石钴铁氧体和氧化铜的复合催化剂CoFe2O4/CuO,通过扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和X射线衍射(XRD)对制备出的CoFe2O4/CuO进行表征,探究不同高级氧化体系对磺胺甲恶唑(SMX)去除能力,考察过氧乙酸(PAA)浓度、催化剂投加量、水体中常见干扰物质(Cl-,HCO-3,SO42-,HA)和不同自由基捕获剂对SMX去除的影响。分析结果表明CoFe2O4/CuO同时具有CoFe2O4与CuO的特征,对比单独CoFe2O4与CuO,CoFe2O4/CuO对PAA展现出极高的活化性能,在最佳反应条件下(催化剂投加量=20mg·L-1,c(PAA)=200μ... 相似文献
38.
J.A. Ball S.T. Murphy R.W. Grimes D. Bacorisen R. Smith B.P. Uberuaga K.E. Sickafus 《Solid State Sciences》2008,10(6):717
In perfect normal MgAl2O4 spinel the Mg2+ ions occupy tetrahedral 8a sites and Al3+ ions occupy octahedral 16d sites. In reality some cations are exchanged between the cation sublattices forming pairs of antisite defects and thus a degree of “inversion”. Here atomic simulation is used to investigate the influence that antisite defects have on the populations of other intrinsic defects, those associated with Schottky and Frenkel reactions. One consequence is that the total magnesium interstitial concentration is increased substantially over the aluminium interstitial concentration and the magnesium vacancy concentration is increased over the aluminium vacancy concentration but to a much smaller extent. The split structures of isolated interstitial defects and the stability of various defect clusters are also discussed. 相似文献
39.
《Comptes Rendus Chimie》2016,19(8):955-962
A ZnxCu1−xAl2O4 catalyst was prepared via the microwave-assisted solution combustion method (MSC). This method presents a fast procedure for industrial scale catalyst preparation. The physicochemical properties of the fabricated catalyst were characterized using XRD, FTIR, BET, SEM and TEM analyses. The catalytic performance through the esterification reaction was examined under the following conditions: reaction temperature = 180 °C, catalyst concentration = 3% (w/w), molar ratio of oleic acid to methanol = 9 and reaction time = 6 h. XRD results showed that loading both zinc and copper oxides on alumina at a ratio of amounts that were nearly the same resulted in decreased crystalline size and well-dispersed copper-alumina and zinc-alumina crystals. Moreover, the mean pore diameter of the sample was increased by simultaneous loading of zinc and copper oxides on alumina that enhanced permeation of the reactants within pores and increased the interaction of the reactant with the catalyst active sites. The catalyst showed minimum tendency towards adsorbing moisture from air, which was attributed to it having less atoms on the surface through which binding with H2O molecules takes place. The highest level of activity in the esterification reaction (96.9%) was obtained at the optimum ratio of the Zn:Cu molar ratio, identified to be 2:3. The sample particles ranged from 10 to 30 nm in size, without agglomeration. 相似文献
40.
Combining two methods, coating and doping, to modify spinel LiMn2O4, is a novel approach we used to synthesize active material. First we coated the LiMn2O4 particles with the nickel oxide particles by means of homogenous precipitation, and then the nickel oxide-coated LiMn2O4 was calcined at 750 °C to form a LiNixMn2−xO4 shell on the surface of spinel LiMn2O4 particles. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cyclic voltammetry (CV) and charge-discharge test were performed to characterize the spinel LiMn2O4 before and after modification. The experimental results indicated that a spinel LiMn2O4 core is surrounded by a LiNixMn2−xO4 shell. The resulting composite showed excellent electrochemical cycling performance with an average fading rate of 0.014% per cycle. This improved cycle stability is greatly attributed to the suppression of Jahn-Teller distortion on the surface of spinel LiMn2O4 particles during cycling. 相似文献