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1.
Lithium perchlorate (LiClO4) was dissolved in dehydrated chloroform with polyethylene oxides (PEO) having different molecular weights. The mixing ratio of ether oxygen unit (? O? ) of PEO to cation (Li+) was set to 20:1. The solution viscosity of the PEO/LiClO4 mixtures was measured using an Ubbelohde viscometer at 30.0°C. The concentration dependence of the reduced viscosity was analyzed by diluting the initial PEO/LiClO4 mixed solution with pure chloroform to keep the ratio of ? O? to Li+ constant. The increase in the reduced viscosity for a dilute solution was found in every mixture system, but not in the PEO solution without salt. Similar experiments were also carried out in chloroform/dimethylformamide (DMF) mixed solvent (4:1 by volume). These results were analyzed using the Fuoss equation, which was applied for the analysis of a polyelectrolyte aqueous solution. Linear relations are depicted in the Fuoss plots, suggesting that the PEO/LiClO4 mixture shows polyelectrolyte-like behavior in chloroform or in chloroform/DMF mixed solvent. This is attributed to the intramolecular electrostatic repulsion of lithium cations which are trapped by the PEO chains through ion–dipole interaction. 相似文献
2.
Polyethylene oxide (PEO)/SiO2 anion-exchange hybrid materials were prepared through the sol-gel process of alkoxysilane functionalized PEO-1000 (PEO-[Si(OCH3)3]2) and N-[3-(trimethoxysilyl)propyl] ethylene diamine (A-1120). The influence of the multi-step sol-gel processing procedure, i.e. the pre-hydrolysis of either of the two precursors on the homogeneity of the hybrid materials was investigated. Results showed that the sol-gel reaction of A-1120 and PEO-[Si(OCH3)3]2 from the same time would result in hybrid materials with the highest homogeneity, and pre-hydrolysis of A-1120 or PEO-[Si(OCH3)3]2 could only decrease the materials’ compatibility. 相似文献
3.
M.A. Cortés-Jácome J.A. Toledo-AntonioH. Armendáriz I. HernándezX. Bokhimi 《Journal of solid state chemistry》2002,164(2):339-344
Catalysts in the WO3-ZrO2 system were produced by coprecipitation of aqueous solutions of zirconium oxynitrate and ammonium metatungstate. Samples were characterized by X-ray powder diffraction, thermogravimetry, and refinement of their crystalline structures with the Rietveld method. This coprecipitation gave rise to solid solutions of tungsten oxide into zirconia; the initial phase was amorphous and crystallized into two tetragonal crystalline phases, T1 and T2, when samples were annealed at 560°C. The main difference between both phases was the oxygen position along the c axis. In the phase with higher symmetry, T2, an oxygen atom was at one-half of the unit cell, 0.50(2), producing flat crystallite surfaces perpendicular to the c axis, while in the phase with the lower symmetry, T1, it was at 0.447(2), and gave rise to rough crystallite surfaces parallel to (100) planes. The interpenetrating tetrahedra forming the representative polyhedron of the crystalline structure were almost nondeformed in the phase with higher symmetry, because all Zr-O atom bond lengths were very similar. As the annealing temperature of the sample was increased, the dissolved tungsten atoms in the phase with higher symmetry segregated to the crystallite's surface. 相似文献
4.
The effect of a common polymer, polyethylene glycol with molecular weight of 400 (PEG-400) on the microstructure of 1-butyl-3-methylimidazolium
tetrafluoroborate (bmimBF4)/Triton X-100/cyclohexane ionic liquid (IL) reverse microemulsion has been investigated. The addition of PEG-400 leaded to
the linear increase of the microemulsion droplet size, in accordance with the observation of dispersed phase, showing that
PEG-400 was only solubilized into the polar interior of the IL microemulsions. FTIR spectroscopic analysis indicated that
the addition of PEG-400 decreased the electrostatic interaction between the oxygen atoms of OE units and the positive electrical
charged imidazolium cation of bmimBF4. At the same time, the oxygen atoms of PEG-400 can also interact with the imidazolium cation. These results suggested that
small amounts of PEG-400 entered the palisade layers of the IL microemulsion. The conductivity of the IL reverse microemulsions
was decreased owing to the dilution of conducting polar cores by the addition of insulative PEG-400, indicating that PEG-400
was only solubilized into the reverse IL microemulsion interior. The conclusion was further supported by viscosity measurement. 相似文献
5.
The partial substitution of Co by Rh in the [Pb0⋅7Co0.4Sr1.9O3]RS[CoO2]1.8 family has been investigated. By transmission electron microscopy and X-ray powder diffraction, it is shown that the substitution of Rh for Co takes place at the two cobalt sites of the structure but for the low enough Rh contents, this substitution is made preferentially at the level of the CdI2-like layer. Thus, a generic formula [Pb0.7(Co0.4−zRhz)Sr1.9O3]RS[Co1−yRhyO2]b1/b2 (0?y?0.5 and 0?z?0.3) can be proposed for this new family of misfit phase. As observed for the pure misfit cobaltite, the thermoelectric power is also very large, close to +140 μV/K at room temperature. The Rh cation can adopt a mixed valency Rh3+/Rh4+ (4d6/4d5) with low spin states t2g6/t2g5 equivalent to the ones of low spin Co3+/Co4+ (3d6/3d5). The large thermopower observed in the Rh substituted compounds is therefore a direct proof that the coexistence of low spin states t2g6/t2g5 contributes to the thermoelectric power enhancement in these oxides. 相似文献
6.
Electron spin resonance spectra of Gd3+ in diluted solid solutions of Gd2O3 in CeO2 have been studied at room temperature for Gd concentrations between 0.01 and 1.00 mol%. While in the case of Mn2+:CeO2 samples, both the linewidth and the line intensity go through a maximum between 0.2 and 0.4% Mn and then start to decrease, in the case of Gd3+:CeO2 samples the linewidth and the line intensity increase monotonically with the dopant concentration. This as taken as evidence that in Gd2O3-CeO2 diluted solid solutions there are no clustering effects similar to the ones observed in Mn:CeO2 solid solutions. It is not clear why clustering effects are present in Mn:CeO2 solid solutions and not in Gd:CeO2 solid solutions; however, it seems reasonable to assume that this is due to the fact that the ionic radius of Mn2+ (81 pm) is about 25% smaller that that of Gd3+ (107.8 pm). In any case, the fact that Gd:CeO2 solid solutions do not exhibit clustering effects means that ESR linewidth data can be used to estimate the concentration of Gd in CeO2 samples, as it is possible to do in several solid solutions of paramagnetic ions in ceramic materials. The results also suggest that the range of the exchange interaction between Gd3+ ions in CeO2 is about 0.89 nm. 相似文献
7.
采用共沉淀法制备了CeO2,Co3O4和一系列Co3O4/CeO2复合氧化物催化剂,在400 ℃下含SO2的氧化气氛中对催化剂进行了硫中毒处理,通过原位红外光谱、X射线衍射、程序升温脱附和X射线光电子能谱对新鲜和硫中毒的样品进行了表征. 结果表明,所有测试的硫中毒样品上均形成了硫酸盐,CeO2上累积的硫酸盐明显比Co3O4上的多,Co3O4/CeO2复合氧化物在硫中毒过程中形成了硫酸钴和硫酸铈. 对新鲜和硫化样品在NO/O2气氛下进行了催化炭黑燃烧实验,发现Co3O4/CeO2复合氧化物的活性和抗硫性能优于CeO2,但抗硫性能低于Co3O4. 相似文献
8.
The conductivity behavior of Al(OH)3-acrylamide hybrid polyacrylamide (hybrid PAAm) in distilled water was studied. A discontinuity phenomenon of the conductivity (k) versus concentration (c) curve of the hybrid PAAm in a certain concentration regime is found. This phenomenon is dependent on the molecular weight of the hybrid PAAm and on the particle size and content of the AI(OH)3 colloid in the hybrid PAAm. This phenomenon was accounted for assuming ionization of the hybrid PAAm. 相似文献
9.
Gianluca Melillo Lorella Izzo Roberto Centore Angela Tuzi Alexander Z. Voskoboynikov Leone Oliva 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):29-33
The meso ansa zirconocene with dimethylsilyl bridge, activated by methylalumoxane, catalyses the ethylene polymerization, producing ethyl-branched polyethylene. With respect to the polymers obtained with the previously investigated meso zirconocenes, we have found higher branching amount and lower molecular weight. The rapid β-H transfer from the growing chain to the coordinated monomer could account for both these features of the polymer. The investigation on the structural parameters of the complex, through X-ray diffraction analysis, and on the electrophilicity of the cationic center, through NMR experiments, suggests, as a possible rationalization of this behavior, the obstruction in the inward site. 相似文献
10.
Brendan J. Kennedy Christopher J. Howard Yoshiki Kubota 《Journal of solid state chemistry》2004,177(12):4552-4556
The crystal structure of the layered perovskite La1/3NbO3 has been studied between room temperature and 500 °C using synchrotron X-ray powder diffraction methods. The structure shows ordering of the La cations at all temperatures. At room temperature La1/3NbO3 is orthorhombic with the NbO6 octahedra showing out-of-phase tilting about the a-axis. This tilting diminishes as the temperature increases, so that above 200 °C the structure is tetragonal. The transition to the tetragonal structure is found to be continuous and analysis of the spontaneous strains shows it to be tricritical in nature. 相似文献
11.
The lattice parameter changes with respect to temperature (T) have been measured by high temperature X-ray diffraction (HTXRD) technique for ThO2NdO1.5 solid solutions containing 23.8 and 42.5 mol% NdO1.5 in the temperature range from 298 to 2000 K. The temperature versus lattice parameter data have been made use of in calculating the lattice thermal expansivity. The values of thermal expansion of the solid solutions were found to be increased with increase in neodymium oxide content and temperature. The mean linear thermal expansion coefficients in this temperature range for ThO2NdO1.5 solid solutions are 12.28 × 10−6 and 12.90 × 10−6 K−1, respectively. The binding energies of Th 4f7/2 and Nd 3d5/2 energy levels of the solid solutions containing 13.1, 23.8, 31.9, 37.2 and 42.5 mol% NdO1.5 and two-phase mixtures containing 47.6 and 51.8 mol% NdO1.5 were experimentally determined by X-ray photoelectron spectroscopy (XPS). 相似文献
12.
Na2Ti3O7 and Na2Ti6O13 were synthesized by sol-gel method in order to obtain pure phases. Different heat-treatments were applied on powders and pellets of these materials. The effects were studied by XRD, dilatometry, TGA-DTA, SEM and electrochemical impedance spectroscopy. Pure Na2Ti3O7 was obtained at 973 K. Sintering at 1373 K caused a partial decomposition into Na2Ti6O13. The Na2Ti3O7 powder sintered at 1273 K showed polygonal microstructure. Na2Ti3O7 pellets sintered at 1323 K for 10 h exhibited large structures. This latter microstructure decreased the electrical conductivity of Na2Ti3O7. Pure Na2Ti6O13 was obtained at 873 K. Sintering at 1073 K caused a partial decomposition into TiO2 (rutile). Na2Ti6O13 pellets sintered at 1323 K for 10 h exhibited common shrinkage behavior. This shrinkage process increased the electrical conductivity of this material. The presence of TiO2 resulted in a oxygen partial pressure dependence of the electrical conductivity. 相似文献
13.
The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry (CD-IMS). The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/(molecules s) to 8.24×10-9 cm3/(molecules s) as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region,the attachment rate constants are also detected at different sample concentration. The ion-molecule reaction rate constants for the further reaction between Cl- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS. 相似文献
14.
A series of Au/Fe2O3/Al2O3 catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe2O3/Al2O3 exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 °C, while it was only 21% over the 2%Au/Al2O3 catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity. X-ray diffraction results indicated that both Au and Fe2O3 particles were highly dispersed over Al2O3. H2-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe2O3, which made the reduction of Fe2O3 easy. The synergistic effect between Au and Fe2O3 was probably responsible for the good catalytic performance of the Au/Fe2O3/Al2O3 catalyst at low temperature. 相似文献
15.
以水热合成针铁矿为前驱体浸渍偏钒酸铵,分别于300,400和500℃空气中焙烧,制备了不同活性组分负载量的V2O5/赤铁矿(V/H)催化剂,用于氨选择性催化还原(SCR)脱硝。采用X射线衍射、透射电子显微镜、比表面积分析仪、程序升温还原及程序升温脱附等方法对催化剂结构进行了表征,并用标气配制模拟烟气进行了脱硝实验。结果表明,300℃煅烧3%V/H催化剂当烟气温度为250-300℃时NO转化率均可达95%以上;当配气中单独加入水蒸气或低浓度SO2(0.01%)时,V/H催化脱硝的活性不受影响;当系统加入高浓度的SO2(0.03%与0.05%)或同时添加H2O与SO2时,SCR脱硝效率下降,其机制可能是SO2在催化剂表面竞争吸附所致,停止添加后,催化活性迅速恢复。 相似文献
16.
H.U. Anderson M.M. Nasrallah B.K. Flandermeyer A.K. Agarwal 《Journal of solid state chemistry》1985,56(3):325-334
The stability of high-temperature fuel cell electrodes to their ambient environment is important for the long-term reliability of fuel cells. In this report the behavior of oxide electrode materials as a function of oxygen activity and temperature is considered. Models for the oxidation-reduction behavior of both p- and n-type oxides are presented. These models take into account the absorption and evolution of oxygen which take place as oxygen activity is varied. The resulting instability in electrical conductivity is explained as a consequence of changes in carrier concentration due to variability in ionic defect concentration. The proposed models are applied to acceptor-doped LaCrO3 and donor-doped SrTiO3. It is shown that the models explain the experimental data well and as a consequence diagrams can be made which show the regions of oxygen activity and temperature for which stability of electrical conductivity and defect structure might be expected. 相似文献
17.
Rodion V. Panin Nellie R. Khasanova Evgeny V. Antipov Walter Schnelle 《Journal of solid state chemistry》2007,180(5):1566-1574
NaPd3O4, Na2PdO3 and K3Pd2O4 have been prepared by solid-state reaction of Na2O2 or KO2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd3O4 (space group Pm3¯n, a=5.64979(6) Å, Z=2) is isostructural to NaPt3O4. It consists of NaO8 cubes and PdO4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO4 squares are perpendicular to each other. Na2PdO3 (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li2RuO3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na+ and Pd4+ cations alternate with Na3 layers along the c-axis. Na2PdO3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K3Pd2O4, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO4 units connected via common edges to form parallel staggered PdO2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K3Pd2O4 reveal a Curie-Weiss behavior in the temperature range above 80 K. 相似文献
18.
The effect of the incorporation of small amounts (1–5 wt%) of semiconducting BaBiO3 and metallic Ba0.6K0.4BiO3 additives on the rechargeability of electrolytic manganese dioxide (EMD) cathodes in alkaline cells in the one-electron regime has been investigated. Both the BaBiO3 and Ba0.6K0.4BiO3 additives lead to better cyclability compared to the previously known binary oxide additive Bi2O3. X-ray diffraction patterns recorded before and after 30 cycles as well as cyclic voltammograms recorded after first and 30 cycles reveal that the better cyclability in the presence of BaBiO3 and Ba0.6K0.4BiO3 additives is due to the suppression of the formation of unwanted, electrochemically inactive birnessite and hausmannite phases and a shifting of the second-electron capacity of Mn to higher potentials. 相似文献
19.
(WO3)0.15(BiO1.5)0.85 exhibits a tetragonal structure derived from the fluorite subcell. The electrical conductivity of (WO3)0.15(BiO1.5)0.85 is lower than that of Y2O3-doped Bi2O3. The structure and electrical conductivity of samples formulated as (YO1.5)
x
(WO3)0.15(BiO1.5)0.85-
x
(x = 0.1, 0.2, 0.3, and 0.4) were investigated. The as-sintered (YO1.5)0.1(WO3)0.15(BiO1.5)0.75 exhibited a single cubic structure that is isostructural with δ-Bi2O3. For x = 0.2, 0.3, and 0.4, the as-sintered samples consisted of a cubic fluorite structure and rhombohedral Y6WO12. After heat treatment at 600 °C for 200 h, the cubic structures are stable for x = 0.1, 0.3, and 0.4. A transformation from cubic to rhombohedral phase after heat treatment at 600 °C for 200 h was observed
in the sample originally formulated as (YO1.5)0.2(WO3)0.15(BiO1.5)0.65. 相似文献
20.
液相合成铁系元素及其合金纳米微粉,一般是用硼氢化物[1 ̄4]等强还原剂将低价的Fe2 、Co2 、Ni2 还原为金属单质。前文[5]在合成须状Fe-Ni-B-O纳米合金及其组成方面进行了报道。实验中发现,通氢还原的纳米合金在少量氧气的存在下,可以和氯化物反应,产物为FeCl2、NiCl2和Cl2,氯化物中的碳元素镶嵌在纳米合金微粉表面,本文将对所合成的纳米合金与CCl4反应的反应性能进行研究,并对反应的机理做简单的描述。该项研究工作目前国内外尚未见文献报道。1实验部分1.1实验仪器及试剂AgNO3;K2Cr2O7;CCl4;CHCl3;CH2Cl2;200mg·L-1HCl(1 1)… 相似文献