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1.
Mesoporous Ce1 ? x Fe x O2 mixed oxide catalysts of different molar ratios (x = 0.1–0.5) were prepared by the citric acid sol-gel method and the microwave technique. The activities of Ce1 ? x Fe x O2 mixed oxides on methane combustion were investigated, and the structure and reductive properties were characterized by XRD, BET, DRS, and TPR. The data showed that Ce1 ? x Fe x O2 mixed oxides prepared were mesoporous material. When x ≤ 0.2, the transition metal Fe incorporated into the lattice of CeO2 to form cubic Ce1 ? x Fe x O2 solid solutions, and mixed phases of cubic Ce1 ? x Fe x O2 solid solutions and α-Fe2O3 existed when x > 0.2. Ce1 ? x Fe x O2 solid solutions show higher activity for methane combustion than pure CeO2, especially for Ce0.9Fe0.1O2. 相似文献
2.
Ce1?xErxO2 and Ce1?2xErxGdxO2 co-doped ceria electrolyte nanopowder materials were successfully prepared by sol–gel method. Depending on the temperature, the crystal structure changes were analyzed by X-ray diffraction. It was observed that the crystal size of the electrolytes decreased depending on the temperature and the time. X-ray diffraction results confirmed cubic fluorite structure in the samples. The microstructural properties of the samples were analyzed by scanning electron microscopy, and thermal stability measurement was performed by thermogravimetric and differential thermal analyses. The total electrical conductivity of the nanopowder electrolytes was determined by the dc four-point probe technique in air at temperatures ranging from room temperature to 1373 K. The four-probe conductivity results revealed that Ce0.8Er0.1Gd0.1O2 has a higher ionic conductivity compared to Ce0.83Er0.17O2 at 1123 K. The four-probe conductivity results show that both Ce1?xErxO2 and Ce1?2xErxGdxO2 solid electrolytes have potential application to oxide ionic conductor for solid oxide fuel cells. 相似文献
3.
利用溶胶-凝胶方法在800 ℃焙烧10 h后, 合成了固溶体Ce1-xNdxO2-δ (x=0.05~0.55), X射线衍射(XRD)测试表明固溶体已经形成立方萤石结构; 电子顺磁共振谱(EPR)研究表明在固溶体Ce1-xNdxO2-δ中随着掺杂量x的增大, Ce3+离子含量减少, 说明掺杂Nd3+离子可以抑制Ce4+的还原; 交流阻抗谱的测量表明固溶体Ce0.9Nd0.1O2-d 具有离子导电特性, 600和700 ℃时的电导率分别为4.25×10-3和1.12×10-2 S•cm-1, 活化能为0.68 eV. 相似文献
4.
Heqing Jiang Dr. Fangyi Liang Oliver Czuprat Konstantin Efimov Armin Feldhoff Dr. Steffen Schirrmeister Dr. Thomas Schiestel Dr. Haihui Wang Prof. Jürgen Caro Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7898-7903
A porous perovskite BaCoxFeyZr0.9?x?yPd0.1O3?δ (BCFZ‐Pd) coating was deposited onto the outer surface of a BaCoxFeyZr1?x?yO3?δ (BCFZ) perovskite hollow‐fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ‐Pd porous layer on the outer surface of a dense BCFZ hollow‐fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ‐Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH4 onto the permeation side of the membrane. The blank BCFZ membrane and surface‐modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H2 min?1 cm?2 at 950 °C after depositing a BCFZ‐Pd porous layer onto the BCFZ membrane. 相似文献
5.
A novel technique of fabricating magnetic thermoplastic nanofibers by the control of the phase separation of immiscible polymer blends during melt extrusion was presented. The magnetic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE)/Fe3O4 composite nanofibers were prepared via the melt extrusion of cellulose acetate butyrate matrix and PVA‐co‐PE preloaded with different amounts of Fe3O4 nanoparticles. The morphologies of magnetic composite nanofibers were characterized by scanning electron microscopy. The uniform dispersion of Fe3O4 nanoparticles in nanofiber matrixes and crystal structures were confirmed using transmission electron microscopy and wide angle X‐ray diffraction. Thermogravimetric analysis was employed to quantify the exact loading amount of Fe3O4 nanoparticles in the composite nanofibers. The magnetic measurements showed that composite nanofibers displayed superparamagnetic behavior at room temperature. With increasing content of Fe3O4 nanoparticles, the saturation magnetization of the magnetic composite nanofiber significantly improved. The prepared magnetic composite nanofibers might have found potential applications in the sensors and bio‐molecular separation fields. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
A series of mixed oxides Sr4Fe6?xCoxO13?δ (x=0, 1, 2, 3, or 4) were prepared by sol‐gel method and used for catalytic combustion of methane. The structural properties of oxides were characterized by XRD, TGA, and XPS. The layered intergrowth perovskite‐like oxide Sr4Fe5CoO13?δ exhibits the highest catalytic activity for methane combustion under the experimental conditions. The enhanced catalytic activity of Sr4Fe5CoO13?δ for methane combustion could be attributed to the increased amount of oxygen vacancy caused by the partial substitution of cobalt for iron in the Sr4Fe6O13, which was confirmed by TGA and XPS. 相似文献
7.
以超高比表面炭材料为模板,硝酸盐为氧化物前体,通过改进的模板路线制备了具有较高比表面积的纳米CexFe1-xO2固溶体.采用X射线衍射、拉曼光谱、物理吸附和透射电镜对制备的样品进行了表征.结果表明,α-Fe2O3,CexFe1-xO2固溶体和CeO2的粒子尺寸为5~15nm,CeO2中部分Ce4 离子被Fe3 离子取代,从而形成了CexFe1-xO2固溶体.乙醇水蒸气重整反应结果显示,CexFe1-xO2固溶体比相应的α-Fe2O3和CeO2具有更高的催化活性和对氢气的选择性. 相似文献
8.
Magnetic poly(styrene?methyl methacrylate-glycidyl methacrylate)/Fe3O4 nanospheres with epoxy groups were prepared by modified one-step mini-emulsion polymerization in the presence of Fe3O4 ferrofluids. The products were characterized by fourier-transform infrared spectrum, transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometer. After surface modification with diaminopropane, histidine was covalently linked to the amine group of magentic nanospheres using glutaraldehyde as crosslinker. Finally, the preliminary labeling study based on non-radioactive rhenium was carried out and the labeling efficiency reached 80.4%. Such magnetic nanospheres had promising potential in magnetically targeted radiotherapy of cancer. 相似文献
9.
Xiaobing Zhao Yingqin Meng Xiaowang Lu Xiazhang Li 《Journal of Sol-Gel Science and Technology》2013,66(1):22-30
Ce1?x Ti x O2 nanocomposites supported on attapulgite clay (Ce1?x Ti x O2/ATP) were prepared by a facile sol–gel route. The textural and structural properties of the prepared products were characterized by thermogravimetric-differential scanning calormetry analysis, X-ray diffraction, transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared spectroscopy and Nitrogen adsorption-desorption measurements. The catalytic activity of the prepared Ce1?x Ti x O2/ATP catalysts for rhodamine B degradation was investigated. Results indicate that the particle size of Ce1?x Ti x O2 nanoparticles evenly attached onto the surface of ATP is approximately 10 nm. The Ti4+ doping ratios exhibit considerable impact on the redox ability and catalytic activity of Ce1?x Ti x O2/ATP composites. The introduction of an optimal amount of Ti4+ contributes to forming structure defects and electronic defects in the oxide lattice, increasing concentration of oxygen vacancies, consequently improving low-temperature redox ability of Ce4+ and enhancing catalytic activity of the composites. Ce1?x Ti x O2/ATP (x = 0.5) catalyst has the best catalytic degradation efficiency, which can reach as high as 97 % after reaction for 240 min. It is also found that attapulgite clay exhibit a positive synergistic effect to the Ce1?x Ti x O2 nanoparticles. 相似文献
10.
Preetam Singh 《Journal of solid state chemistry》2008,181(12):3248-3256
CeO2 and Ce1−xMxO2−δ (M=Zr, Ti, Pr, Y and Fe) nanocrystallites of 5-10 nm sizes have been synthesized by hydrothermal method using diethylenetriamine (DETA) and melamine as complexing agents. Compounds have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX) and their structures have been refined by the Rietveld method. All the compounds crystallize in cubic fluorite structure. Even up to 50% Zr and Y, 40% Ti, 25% Pr and 15% Fe is substituted for Ce4+ in CeO2 by this method. Sizes of crystallites can be tuned by changing the complexing agent and reaction temperature. Nanocrystalline CeO2 and Ce1−xZrxO2 prepared here have higher or at least competitive oxygen storage capacity (OSC) than those reported in literature. Ce1−xFexO2−δ shows higher OSC and higher percentage of CO oxidation at lower temperature than Ce1−xZrxO2. 相似文献
11.
Yinjuan Huang Mingzhu Liu Jiucun Chen Chunmei Gao Qiuyu Gong 《European Polymer Journal》2012,48(10):1734-1744
In this work, Fe3O4/poly(3-acrylamidephenylboronic acid-co-(2-dimethylamino) ethyl methacrylate) (Fe3O4/P(AAPBA-co-DMAEMA)) hydrogels possessing magnetic and triple-responsive properties and semi-interpenetrated by β-cyclodextrin-epichlorohydrin (β-CD-EPI) were prepared via radical polymerization. The characteristics of the materials have been investigated by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM). The swelling measurements and the application of Fe3O4/P(AAPBA-co-DMAEMA)/(β-CD-EPI) hydrogels in controlled release of drug were also investigated. It was found that the magnetic hydrogels exhibit swelling behaviors affected by pH, temperature, glucose concentration and magnetic field, and have porous morphologies, superparamagnetism. Moreover, the hydrogels possess targeting and could control the release of quercetin by adjusting pH value, temperature, glucose concentration and magnetic field. 相似文献
12.
以乙酰丙酮金属盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了镍锌不同配比的Ni_xZn_(1-x)Fe_2O_4(x=0,0.3,0.5,0.7和1.0)铁氧体,并通过X射线衍射仪(XRD),透射电子显微镜(TEM)和振动样品磁强计(VSM)等对样品的结构、形貌、磁性能和磁热性能进行了表征。结果表明:Ni_xZn_(1-x)Fe_2O_4铁氧体分散性较好,尺寸均一,形状近似球形,平均粒径为4~5 nm。Ni_xZn_(1-x)Fe_2O_4纳米颗粒在室温下表现出亚铁磁性,饱和磁化强度随着镍含量的增加先增大后减小,当x=0.5时达到最大值29.38 emu·g~(-1)。在382k Hz交变磁场作用下,Ni_(0.5)Zn_(0.5)Fe_2O_4铁氧体温度可升温至313 K,表现出较好的磁热性能。 相似文献
13.
14.
Ce
x
Sn1−x
O2 metal oxides were prepared by a citrate method and used as supports for CuO/Ce
x
Sn1−x
O2 catalysts. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, high-resolution
TEM, and temperature-programmed reduction techniques. XRD analysis indicated that the Ce
x
Sn1−x
O2 samples maintain the fluorite structure and form a solid solution when x = 0.9 or 0.8. TPR analysis revealed that two kinds of copper species are present on the surface of the Ce
x
Sn1−x
O2 support. The catalytic properties of the CuO/Ce
x
Sn1−x
O2 catalysts were evaluated for low-temperature CO oxidation using a microreactor-GC system. The effects of Ce/Sn ratio and
CuO loading on the catalytic performance were investigated. The results showed that these CuO/Ce
x
Sn1−x
O2 catalysts are very active for low-temperature CO oxidation. The 650 °C calcined 7 wt%-CuO/Ce
x
Sn1−x
O2 catalyst exhibited the highest catalytic activity. 相似文献
15.
L. A. Dunyushkina A. V. Kuz’min V. B. Balakireva V. P. Gorelov 《Russian Journal of Electrochemistry》2006,42(4):375-380
Transport numbers for oxygen ions and protons are measured by an emf method in the system CaTi1?x FexO3?δ (x = 0.1–0.5) in the oxidizing and reducing atmospheres in the temperature interval 973–1173 K. It is shown that the compounds under study are mixed ion-electron conductors at small iron concentrations and electron conductors, at large iron contents. The proton conductivity in the compounds is very poor and does not exceed 0.5% in air. On the basis of the temperature dependences of transport numbers for ions and linear expansion, it is established that the CaTi0.9Fe0.1O3?δ system has a phase transition of a second order in a reducing environment at 1020–1050 K. The total and partial electron conductivities of CaTi0.9Fe0.1O3?δ are studied as a function of the partial pressure of oxygen at 1173 K. The nature of electroconduction in CaTi1?x FexO3?δ is discussed. 相似文献
16.
The SrCexFe12?xO19 (x????0.08) ferrite microfibers were prepared via sol?Cgel method from starting reagents of metal nitrate salts and citric acid. The obtained microfibers were characterized by TG-DSC, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD patterns show that the main phase is M-type strontium hexaferrite without other impurity phases when calcined at 750?°C for 1?h, and the Ce3+ ions doping has not resulted in crystal structural changes of the Sr ferrite magnetoplumbite type structure. The SEM and TEM images indicate that samples with different calcination temperature and various values of x possess the diameters of below 10???m and homogeneous hexagonal plate-like morphology. The VSM results show that saturation magnetization (Ms) gradually increases with increase of calcination temperature while decreases with increase of addition of Ce3+ ions, and coercive force (Hc) reveals an increase at first and then decreases with increase of calcination temperature and Ce3+ ions content. 相似文献
17.
Synthesis and catalytic evaluation of Fe3O4/MWCNTs nanozyme as recyclable peroxidase mimetics: Biochemical and physicochemical characterization
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In this research, the nanocomposite of multiwalled carbon nanotubes and magnetic metal oxide nanoparticles (Fe3O4/MWCNTs), as enzyme mimetic, was synthesized using an in situ chemical reduction method. The structure, composition and morphology of the prepared Fe3O4/MWCNT nanocomposite materials were characterized using X‐ray diffraction, FT‐IR and scanning electron microscopy with energy dispersive X‐ray spectroscopy, respectively. The magnetic properties of the nanocomposite were investigated by the vibrating sample magnetometer. A colorimetric system involving nanozyme, phenol/4‐aminoantipyrine and H2O2 was utilized for the determination of peroxidase mimetic catalytic assay. The obtained results confirmed that the synthesis of Fe3O4/MWCNTs nanostructures was successful. It was found that Fe3O4/MWCNTs nanohybrid exhibited peroxidase‐like activity without any pH limitation. Colorimetric data demonstrated that the prepared nanocatalyst had higher catalytic activity toward H2O2 than MWCNTs. The kinetic parameters of the nanozyme, Km and Vmax, were estimated to be 8.3 mm and 1.4 mm min?1, respectively. The Fe3O4/MWCNTs nanostructures were also successfully applied for glucose detection. In addition, peroxidase‐like activity of the nanozyme increased in the presence of butyl‐imidazolium bromide ionic liquid. These biomimetic catalysts have some advantages, such as simplicity, stability, reusability and cost effectiveness, which makes them great candidates to be used in various fields of biotechnology applications. 相似文献
18.
通过溶剂热和溶胶-凝胶涂层法, 设计并制备了具有分级多孔结构和光催化性质的核-壳纳米球(HP-Fe2O3@TiO2). 透射电子显微镜(TEM)照片证明所得HP-Fe2O3@TiO2样品具备分级多孔结构, 这是因为HP-Fe2O3@TiO2的内核-Fe2O3具有大孔空隙, 同时外壳-TiO2具有介孔空隙. 此外, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)以及氮气吸附-脱附曲线深入研究了HP-Fe2O3@TiO2的结构及其性质. 分别在可见及紫外光照下, 研究了样品在H2O2体系下的光催化降解亚甲基蓝(MB)的性质. 所观察到的HP-Fe2O3@TiO2纳米球的光催化性能, 可归因于核-壳结构的协同作用, 这进一步表明, TiO2外壳对α-Fe2O3的光催化活性有重要影响作用. 在可见光照射下, HP-Fe2O3@TiO2 (1 mL Ti(OC4H9)4 (TBT))具有较优异的光催化活性. 同时, HP-Fe2O3@TiO2 (4mL TBT)具备优异的单分散形貌, 并在紫外光照射下, 表现出最优的光催化活性. 相似文献
19.
Wei-Guo Tian Pan-Pan Wang Ling Ren Gen-Ban Sun Ling-Na Sun Kai Yang Bing-Qing Wei Chang-Wen Hu 《Journal of solid state chemistry》2007,180(12):3551-3559
A controllable synthesis of NiC2O4·2H2O nanorods precursor was obtained via the microemulsion-mediated solvothermal method and a further synthesis of β-Ni(OH)2 nanorods, nickel oxide (NiO) sub-microtubes, Ni nanospheres and flower-like nickel complexes nanostructures by using the precursor. The morphologies and crystalline structures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and the X-ray powder diffraction (XRD). The morphologies and sizes of the precursors can be readily tuned by adjusting experimental parameters of the reverse microemulsion system. The synthesized β-Ni(OH)2 nanorods composed of fine nanosheets shown excellent electrochemical performance as an electrode material in rechargeable battery systems. 相似文献
20.
Effect of Cadmium Substitution on Structural and Magnetic Properties of Nano Sized Nickel Ferrite
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Sanjay Pralhadrao Jadhav Bhagwan Ghanshamji Toksha Kamalakar Marutirao Jadhav Narayan Dadarao Shinde 《化学物理学报(中文版)》2010,23(4):459-464
The structure and crystal phase of the nanocrystalline powders of Ni1-xCdxFe2O4 (0≤x≤0.5) mixed ferrite, synthesized by wet chemical co-precipitation method, were characterized by X-ray diffraction. Results showed that the lattice parameter increased with increasing Cd concentration. Microstructure was studied by scanning electron microscopy. TG/DTA stud-ies were carried out on co-precipitated sulphate complexes. These studies revealed the low ferritization temperature (650 oC) of the ferrite system synthesized by presently adopted route of synthesis and occurrence of simultaneous decomposition and ferritization processes.Further studies by infrared spectroscopy were also conducted. Moreover, magnetic properties of the prepared nanoparticles were studied by magnetization and a.c. susceptibility mea-surements. The response of prepared Ni1-xCdxFe2O4 mixed ferrites to magnetic field was investigated. Results show that, magnetic susceptibility, Curie temperature, and effective magnetic moment decreased as the Cd content increases. 相似文献