共查询到20条相似文献,搜索用时 46 毫秒
1.
M. S. Shchelkanova G. Sh. Shekhtman E. G. Vovkotrub S. V. Plaksin 《Russian Journal of Electrochemistry》2018,54(9):702-708
Lithium-vanadium oxide with the formal composition Li6V5O15, uniform microsctructure, and the particle size of 100 nm is synthesized by a solution method. The synthesized compound is characterized by the methods of X-ray diffraction analysis, Raman spectroscopy, and synchronous thermal analysis. The total electric conductivity is measured by the method of impedance spectroscopy and its electronic component is estimated by dc method. In the temperature range of 200–400°C, Li6V5O15 represents a mixed electronic- ionic conductor with predomination of the ionic component and is thermally stable up to 550°С. Preliminary tests of a laboratory model of electrochemical cell Li|LiPF6|Li6V5O15 are carried out. 相似文献
2.
A. A. Solov’ev N. S. Sochugov A. V. Shipilova K. B. Efimova A. E. Tumashevskaya 《Russian Journal of Electrochemistry》2011,47(4):494-502
Data on the mid-temperature solid-oxide fuel cells (SOFC) with thin-film ZrO2-Y2O3 (YSZ) electrolyte are shown. Such a fuel cell comprises a carrying Ni-YSZ anode, a YSZ electrolyte 3–5 μm thick formed by
vacuum ion-plasma methods, and a LaSrMnO3 cathode. It is shown that the use of a combined method of YSZ electrolyte deposition, which involves the magnetron deposition
of a 0.5–1.5-μm thick sublayer and its pulse electron-beam processing allows a dense nanostructured electrolyte film to be
formed and the SOFC working temperature to be lowered down as the result of a decrease in both the solid electrolyte Ohmic
resistance and the Faradaic resistance to charge transfer. SOFC are studied by the methods of voltammentry and impedance spectroscopy.
The maximum power density of the SOFC under study is 250 and 600 mW/cm−2 at temperatures of 650 and 800°C, respectively. 相似文献
3.
Jitka Hreščak Barbara Malič Jena Cilenšek Andreja Benčan 《Journal of Thermal Analysis and Calorimetry》2017,127(1):129-136
The solid-state synthesis of undoped K0.5Na0.5NbO3 (KNN) and KNN doped with 1, 2 and 6 mol% Sr, from potassium, sodium and strontium carbonates with niobium pentoxide, was studied using thermal analysis and in situ high-temperature X-ray diffraction (HT-XRD). The thermogravimetry and the differential thermal analyses with evolved-gas analyses showed that the carbonates, which were previously reacted with the moisture in the air to form hydrogen carbonates, partly decomposed when heated to 200 °C. In the temperature interval where the reaction was observed, i.e., between 200 and 750 °C, all the samples exhibited the main mass loss in two steps. The first step starts at around 400 °C and finishes at 540 °C, and the second step has an onset at 540 °C and finishes with the end of the reaction between 630 and 675 °C, depending on the particle size distribution of the Nb2O5 precursor. According to the HT-XRD analysis, the perovskite phase is formed at 450 °C for all the samples, regardless of the Sr content. The formation of a polyniobate phase with a tetragonal tungsten bronze structure was detected by HT-XRD in the KNN with the largest amount of Sr dopant, i.e., 6 mol% of Sr, at 600 °C. 相似文献
4.
The electrochemical behavior of the LaSrCuO4 − δ/Ce0.9Gd0.1O2 − δ interface is studied by impedance spectroscopy and cyclic voltammetry methods. By analyzing the dependence of the impedance
frequency spectra on the oxygen partial pressure, the rate-determining stages of oxygen exchange are determined in the temperature
interval of 500–900°C. For temperatures above 700°C, the adsorption of oxygen molecules and their dissociation to oxygen atoms
are shown to make a substantial contribution to the polarization resistance of the overall electrode process, besides the
charge-transfer resistance. 相似文献
5.
Lifen Xiao Yanqiang Zhao Yanyan Yang Xinping Ai Hanxi Yang Yuliang Cao 《Journal of Solid State Electrochemistry》2008,12(6):687-691
LiNi0.5Mn1.5O4 powders were prepared through polymer-pyrolysis method. XRD and TEM analysis indicated that the pure spinel structure was
formed at around 450 °C due to the very homogeneous intermixing of cations at the atomic scale in the starting precursor in
this method, while the well-defined octahedral crystals appeared at a relatively high calcination temperature of 900 °C with
a uniform particle size of about 100 nm. When cycled between 3.5 and 4.9 V at a current density of 50 mA/g, the as prepared
LiNi0.5Mn1.5O4 delivered an initial discharge capacity of 112.9 mAh/g and demonstrated an excellent cyclability with 97.3% capacity retentive
after 50 cycles. 相似文献
6.
N. V. Zaletova A. O. Turakulova S. V. Kutsev V. V. Lunin 《Moscow University Chemistry Bulletin》2009,64(1):1-5
The temperature of soot oxidation and efficiency of Ce0.5Zr0.5O2 catalyst depends on its morphology, which determines the area of intergranular contact between the solid substrate and the catalyst. The temperature-programmed reduction in hydrogen to 1000°C and oxidation at 500°C (redox cycles) cause the mobility of oxygen in oxide to be enhanced and decrease the temperature of soot combustion. Oxidation of soot in the air flow on the Ce0.5Zr0.5O2 catalyst result in its activation. Reuse of the catalyst decreases the temperature of soot oxidation. 相似文献
7.
Žaneta Dohnalová Petra Šulcová Miroslav Trojan 《Journal of Thermal Analysis and Calorimetry》2010,101(3):973-978
The main aim of this work was to synthesize the magnesium orthostannate doped by terbium cations and tested whether these
materials can be used for colouring of the different materials, e.g. organic binder and ceramic glazes. Initial composition
of pigments was counted according the general formula 2MgO(1 − x)SnO2–xTbO2, where values of x varied from 0.1 to 0.5 in 0.1 steps. The simultaneous TG/DTA measurements of mixture containing tin oxide, magnesium carbonate
hydroxide and terbium oxide showed that the formation of a new compound started at temperature 1,029 °C, but single-phase
system was not prepared. Granulometric compositions of samples that were prepared by calcining at temperatures 1,300–1,400 °C
are characterized by values of median (d
50) in range 4–8 μm. The calcining temperature 1,500 °C caused the increase of the particle sizes at around 12 μm. The composition
of sample 2MgO–1.5SnO2–0.5TbO2 and heating temperature 1,500 °C are the most suitable conditions for preparation of colourfully interesting pigment that
can be recommended also for colouring of ceramic glazes. Especially, for colouring of decorative lead containing glaze G 07091
containing 5 wt% of PbO and 8 wt% of Al2O3. 相似文献
8.
K. S. Dhindsa A. Kumar G. A. Nazri V. M. Naik V. K. Garg A. C. Oliveira P. P. Vaishnava Z. X. Zhou R. Naik 《Journal of Solid State Electrochemistry》2016,20(8):2275-2282
We have studied LiFePO4/C nanocomposites prepared by sol-gel method using lauric acid as a surfactant and calcined at different temperatures between 600 and 900 °C. In addition to the major LiFePO4 phase, all the samples show a varying amount of in situ Fe2P impurity phase characterized by x-ray diffraction, magnetic measurements, and Mössbauer spectroscopy. The amount of Fe2P impurity phase increases with increasing calcination temperature. Of all the samples studied, the LiFePO4/C sample calcined at 700 °C which contains ~15 wt% Fe2P shows the least charge transfer resistance and a better electrochemical performance with a discharge capacity of 136 mA h g?1 at a rate of 1 C, 121 mA h g?1 at 10 C (~70 % of the theoretical capacity of LiFePO4), and excellent cycleability. Although further increase in the amount of Fe2P reduces the overall capacity, frequency-dependent Warburg impedance analyses show that all samples calcined at temperatures ≥700 °C have an order of magnitude higher Li+ diffusion coefficient (~1.3?×?10?13 cm2 s?1) compared to the one calcined at 600 °C, as well as the values reported in literature. This work suggests that controlling the reduction environment and the temperature during the synthesis process can be used to optimize the amount of conducting Fe2P for obtaining the best capacity for the high power batteries. 相似文献
9.
Electrical conductivity in the monoclinic Li2TiO3, cubic Li1.33Ti1.67O4, and in their mixture has been studied by impedance spectroscopy in the temperature range 20–730 °C. Li2TiO3 shows low lithium ion conductivity, σ300≈10–6 S/cm at 300 °C, whereas Li1.33Ti1.67O4 has 3×10–8 at 20 °C and 3×10–4 S/cm at 300 °C. Structural properties are used to discuss the observed conductivity features. The conductivity dependences
on temperature in the coordinates of 1000/T versus loge(σT) are not linear, as the conductivity mechanism changes. Extrinsic and intrinsic conductivity regions are observed. The change
in the conductivity mechanism in Li2TiO3 at around 500–600 °C is observed and considered as an effect of the first-order phase transition, not reported before. Formation
of solid solutions of Li2–
x
Ti1+
x
O3 above 900 °C significantly increases the conductivity. Irradiation by high-energy (5 MeV) electrons causes defects and the
conductivity in Li2TiO3 increases exponentially. A dose of 144 MGy yields an increase in conductivity of about 100 times at room temperature.
Electronic Publication 相似文献
10.
Yan-Hua Zhang Hai-Long Zhang Yi Cao Yi Yang Bao-Qiang Xu Ming Zhao Mao-Chu Gong Hai-Di Xu Yao-Qiang Chen 《Chemical Papers》2016,70(10):1370-1379
A series of Co-modified Ce0.5Zr0.5O2 catalysts with different concentrations of Co (mass %: 0, 2, 4, 6, 8, 10) was investigated for diesel soot combustion. Ce0.5Zr0.5O2 was prepared using the coprecipitation method and Co was loaded onto the oxide using the incipient wetness impregnation method. The activities of the catalysts were evaluated by thermogravimetric (TG) analysis and temperature-programmed oxidation (TPO) experiments. The results showed the soot combustion activities of the catalysts to be effectively improved by the addition of Co, 6 % Co/Ce0.5Zr0.5O2 and that the 8 % Co/Ce0.5Zr0.5O2 catalysts exhibited the best catalytic performance in terms of lower soot ignition temperature (Ti at 349°C) and maximal soot oxidation rate temperature (Tm at 358°C). The reasons for the improved activity were investigated by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). These results revealed that the presence of Co could lower the reduction temperature due to the synergistic effect between Co and Ce, thereby improving the activity of the catalysts in soot combustion. The 6 % Co catalyst exhibited the best catalytic performance, which could be attributed to the greater amounts of Co3+ and surface oxygen species on the catalyst. 相似文献
11.
The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 Å3, and Z = 2. Its structure is isotypic with that of Na4Mn(MoO4)3. It is formed by Cu2O10 distorted bi-octahedral dimers linked by two bridging bidentate Mo2O4 tetrahedra and, additionally, two monodentate Mo1O4 tetrahedra to form Cu2Mo4O20 units. These units are linked by the insertion of Mo3O4 tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu2+ cations adopt the [4+2] CuO6 Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra. 相似文献
12.
Phase equilibria in the system K,Cа∥SO4,CO3,HCO3–H2O have been studied at 25°С. This system at 25°С involves 7 invariant points, 21 monovariant curves, and 22 divariant fields. The data gained served to plot the first phase diagram (phase complex) of the studied system at 25°С. 相似文献
13.
Morteza Afshar Alireza Badiei Hamed Eskandarloo Ghodsi Mohammadi Ziarani 《Research on Chemical Intermediates》2016,42(10):7269-7284
Charge separation plays a key role in the conversion of solar energy into chemical energy for use in the redox reaction and as well as in the photocatalytic activity. In this study, SrTiO3 particles with different morphologies including irregular, tetrahexahedron, and cube were synthesized by an in situ solvothermal method. The photocatalytic activity of the synthesized nanoparticles was investigated in the photocatalytic decomposition of methylene blue under UV light irradiation. Tetrahexahedron SrTiO3 particles exhibited high decomposition activity (70 %), which is about two times higher than those of the irregular and cubic SrTiO3 particles. The high decomposition activity of tetrahexahedron SrTiO3 particles could be attributed to the improvement of charge separation achieved on different crystal facets. To reach a good charge separation, tetrahexahedron SrTiO3/TiO2 coupled nanoparticles were fabricated by impregnation method. Results showed that coupling tetrahexahedron SrTiO3 with TiO2 could produce efficient charge separation between tetrahexahedron SrTiO3 and TiO2 due to their matched band edges. In order to achieve better charge separation, the tetrahexahedron SrTiO3/90 %TiO2 sample was calcined at different temperatures in the 450–750 °C range. Tetrahexahedron SrTiO3/90 %TiO2 coupled nanoparticles calcined at 650 °C show high photocatalytic activity compared with other samples. The prepared samples were characterized by using various techniques such as X-ray diffraction, scanning electron microscopy, photoluminescence emission spectra, and UV–Vis diffuse reflectance spectroscopy. 相似文献
14.
Liyuan Han Caiyin You Qin Wang Shaohua Guo Ke Xu Weihua Zhang Rong Yang 《Russian Journal of Electrochemistry》2018,54(1):49-55
α-NaFeO2 layered LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by mechanical milling accompanied by the solid phase sintering. The sample exhibited a good crystallinity and layered structure while sintered at 900°C, which can be further improved by adding a pre-sintering process at 500°C before high temperature sintering. The sample with a pre-sintering process presents an average particle size about 0.6 μm, and a hexagonal crystalline structure. The optimally fabricated sample showed a first charge capacity of 210.2 mA h/g, discharge capacity of 171.2 mA h/g with a current rate of 0.2 C within the voltage range of 2.7~4.5 V. With increasing the current rate to 1 C, the charge–discharge capacity faded quickly during the cycling process, which can be partially recovered while operated at a low current rate. However, the capacity fading at a current rate of 2 C was largely irreversible. The evolution of the surface chemical states was evaluated using X-ray photoelectron spectroscopy on the charged and discharged samples to understand the high rate capacity fading. 相似文献
15.
M. A. Shuvaeva I. V. Delii O. N. Mart’yanov O. A. Bayukov E. I. Osetrov A. A. Saraev V. V. Kaichev N. S. Sakaeva G. A. Bukhtiyarova 《Kinetics and Catalysis》2011,52(6):896-906
The effect of calcination temperature on the state of the active component of iron-containing catalysts prepared by the impregnation of silica gel with a solution of FeSO4 and on their catalytic properties in selective H2S oxidation to sulfur was studied. With the use of thermal analysis, XPS, and Mössbauer spectroscopy, it was found that an X-ray amorphous iron-containing compound of complex composition was formed on the catalyst surface after thermal treatment in the temperature range of 400–500°C. This compound contained Fe3+ cations in three nonequivalent positions characteristic of various oxy and hydroxy sulfates and oxide and sulfate groups as anions. Calcination at 600°C led to the almost complete removal of sulfate groups; as a result, the formation of an oxide structure came into play, and it was completed by the production of finely dispersed iron oxide in the ?-Fe2O3 modification (the average particle size of 3.2 nm) after treatment at 900°C. As the calcination temperature was increased from 500 to 700°C, an increase in the catalyst activity in hydrogen sulfide selective oxidation was observed because of a change in the state of the active component. A comparative study of the samples by temperature-programmed sulfidation made it possible to establish that an increase in the calcination temperature leads to an increase in the stability of the iron-containing catalysts to the action of a reaction atmosphere. 相似文献
16.
A. N. Il’ichev D. P. Shashkin T. I. Khomenko Z. T. Fattakhova V. N. Korchak 《Kinetics and Catalysis》2010,51(5):743-753
It was established by X-ray diffraction, TPR, and EPR that microemulsion (m.e.) synthesis yields the binary oxides ZrO2(m.e.) and CeO2(m.e.) and the mixed oxide Zr0.5Ce0.5O2(m.e.) in the form of a tetragonal, cubic, and pseudocubic phase, respectively, having crystallite sizes of 5–6 nm. The bond
energy of surface oxygen in the (m.e.) samples is lower than in their analogues prepared by pyrolysis. Hydrogen oxidation
on the oxides under study occurs at higher temperatures than CO oxidation. ZrO2(m.e.) and CeO2(m.e.) are active in O2− formation during NO + O2 adsorption, while CeO2 is active during CO + O2 adsorption, too. However, its amount here is one-half to one-third its amount in the pyrolysis-prepared samples, signifying
a reduced number of active sites, which are Zr4+ and Ce4+ coordinatively unsaturated cations and Me4+-O2− pairs. O2− radical anions are stabilized in the coordination sphere of Zr4+ coordinatively unsaturated cations via ionic bonding, and in the sphere of Ce4+ cations, via covalent bonding. Ionic bonds are stronger than ionic-covalent bonds and do not depend on the ZrO2 phase composition. Zr0.5Ce0.5O2 is inactive in these reactions because of the strong interaction of Zr and Ce cations. It is suggested that Ce(4 + β)+ coordinatively unsaturated cations exist on its surface, and their acid strength is lower than that of Zr4+ and Ce4+ cations in ZrO2 and CeO2, according to the order ZrO2 > CeO2 ≥ Zr0.5Ce0.5O2. Neither TPR nor adsorption of probe molecules revealed Zr cations on the surface of the mixed oxide. 相似文献
17.
Among the various positive electrode materials investigated for Li-ion batteries, spinel LiMn2O4 is one of the most important materials. Small particles of the active materials facilitate high-rate capability due to large
surface to mass ratio and small diffusion path length. The present work involves the synthesis of submicron size particles
of LiMn2O4 in a quaternary microemulsion medium. The precursor obtained from the reaction is heated at different temperatures in the
range from 400 to 900 °C. The samples heated at 800 and 900 °C are found to possess pure spinel phase with particle size <200 nm,
as evidenced from XRD, SEM, and TEM studies. The electrochemical characterization studies provide discharge capacity values
of about 100 mAh g−1 at C/5 rate, and there is a moderate decrease in capacity by increasing the rate of charge–discharge cycling. Studies also
include charge–discharge cycling and ac impedance studies in temperature range from −10 to 40 °C. Impedance data are analyzed
with the help of an equivalent circuit and a nonlinear least squares fitting program. From temperature dependence of charge-transfer
resistance, a value of 0.62 eV is obtained for the activation energy of Mn3+/Mn4+ redox process, which accompanies the intercalation/deintercalation of the Li+ ion in LiMn2O4. 相似文献
18.
A. N. Kharlanov A. O. Turakulova A. V. Levanov V. V. Lunin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(4):678-688
The effect the means of synthesis have on the texture, phase composition, redox properties, and catalytic activity of binary oxide systems with the composition Ce0.5Zr0.5O2 are studied. The obtained samples are characterized via BET, SEM, DTA, XRD, and Raman spectroscopy. A comparative analysis is performed of the physicochemical properties of biomorphic systems Ce0.5Zr0.5O2 obtained using wood sawdust and cellulose as templates and the properties of binary oxides of the same composition obtained by template-free means. The catalytic properties of the obtained oxide systems Ce0.5Zr0.5O2 are studied in the reaction of carbon black oxidation. It is shown that the texture of the oxide depends on the means of synthesis. When biotemplates are used, fragile porous systems form from thin binary oxide plates containing micro-, meso-, and macropores. Oxide obtained via coprecipitation consists of dense agglomerates with pores around 30 Å in size. In supercritical water, nanoparticles of metal oxide form that are loosely agglomerated. The intermediate spaces between them act as pores more than 100 Å in size. A system of single-phase pseudocubic modification is obtained using a cellulose template. The crystal lattices of all the obtained systems contain a great many defects. It is shown that the system prepared via synthesis in supercritical water has the best oxygen-exchange properties. A comparative analysis is performed of the effect the physicochemical properties of the samples have on their activity in the catalytic oxidation of carbon black. 相似文献
19.
A. I. Kovrova V. P. Gorelov A. V. Kuz’min B. A.-T. Melekh 《Russian Journal of Electrochemistry》2018,54(9):733-740
Comparative impedance measurements of electric conductivity of nominally undoped yttria are carried out for samples with sharply differing morphologies, namely, single crystals and porous ceramics (with a density of 67%) over a 980–350°С temperature range in air atmosphere of different humidity (рН2О= 40–3000 Pa). Dilatometric analysis of possible structure changes is carried out. The effects of uncontrolled impurities on the yttria defect structure are analyzed. 相似文献
20.
E. G. Shkvarina A. N. Titov S. G. Titova O. M. Fedorova 《Journal of Structural Chemistry》2016,57(4):710-716
Changes in the crystal structure, which are accompanied by iron intercalation and release in the layered intercalation compound TiSe2, demonstrating the retrograde solubility in the completely solid state, are considered. Various concentration regions not exceeding, exceeding, and corresponding to the leakage limit of the overlap of titanium orbitals coordinated by iron are analyzed. It is shown that at low temperatures (below 400°С) the behavior of iron in the TiSe2 lattice is governed by a covalent bond of iron with the lattice whereas at high temperatures (above 1000°С) iron becomes an ionic impurity. In the intermediate temperature range, iron atoms are involved in either covalent or ionic bond with the lattice. When the concentration of iron in the form of the ionic impurity increases, an increase in the cell parameter in the direction perpendicular to the layers is accompanied by a compression of the Se–Ti–Se sandwich and an increase in the van der Waals gap. When the covalent bond forms, there is a decrease in the lattice parameter in the direction perpendicular to the layers, which is accompanied by an increase in the width of the Se–Ti–Se sandwich and a decrease in the van der Waals gap. 相似文献