共查询到20条相似文献,搜索用时 15 毫秒
1.
V. D. Zozulya 《Combustion, Explosion, and Shock Waves》2003,39(1):64-67
The paper reviews published data on structural–phase changes in Cu–Al and Ni–Al metal powders during in situ combustion. The heatconservation properties of various structures located around reactive cells in the combustion wave zone are revealed. The mechanism providing for nearly adiabatic combustion conditions is discussed and a microstructural model for this mechanism is justified. 相似文献
2.
Mohammad Siddiq Guangming Liu Guangzhao Zhang Abbas Khan Peter M. Budd 《Polymer Bulletin》2010,65(5):521-531
The adsorption of poly(ethylene oxide)-b-poly(butylene oxide) diblock copolymers at the solid–liquid interface was studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). The effect of modifying the end group of the hydrophilic block was investigated by comparing the behaviour of trimethylammonium- and dimethylamino-tipped copolymers, designated as TE m B n and DE m B n , respectively. For adsorption from aqueous solution onto a gold surface, results for DE49B22 were similar to those of the T-analogue, but for DE80B34 adsorbed amounts were substantially higher, and for DE27B25 enormously higher, than for the T-analogue. It is suggested that very high levels of adsorption are associated with the formation of a multilayer structure. 相似文献
3.
《Ceramics International》2017,43(14):10698-10707
To prevent undesirable reactions between the cathode and electrolyte materials in cathode-supported solid oxide fuel cells (SOFCs), the co-sintering temperature of these two layers must be lowered. In the present work, we employed different strategies to lower the co-sintering temperature of cathode–electrolyte bilayers for micro-tubular SOFCs by increasing the cathode sintering shrinkage and adding sintering aids to the electrolyte. Strontium-doped lanthanum manganite (LSM) and yttria-stabilized zirconia (YSZ) were used as the cathode and electrolyte materials, respectively. To facilitate densification of the electrolyte layer by controlling the shrinkage of the cathode support, the particle size of the LSM powder was reduced by high-energy ball milling and different amounts of micro-crystalline cellulose pore former were used. Sintering aids, namely NiO and Fe2O3, were also added to the YSZ electrolyte to further improve its low-temperature sintering. Our results indicate that with the improvement in the cathode support shrinkage and use of the small amounts of sintering aids, the cathode–electrolyte co-sintering temperature can be reduced to 1250–1300 °C. It was also observed that the presence of the sintering aids helps to reduce the reactivity between the LSM cathode and YSZ electrolyte. 相似文献
4.
5.
《Journal of the European Ceramic Society》2000,20(4):497-503
Porous calcium hydroxide particles have been equilibrated with water vapor in the relative pressure range 0.4–0.85 at the temperature of 20°C. Then the particles were used in the reaction with gaseous carbon dioxide at the same temperature and at pressure of 0.65 kPa. The system is converted up to 85% into a non-protective layer of calcium carbonate which is all distributed inside the initial porous particles. The same reaction with dry-calcium hydroxide powders converts up to 10% at a temperature of 100°C. The observed catalytic effect is dependent upon the initial amount of water adsorbed. A minimum number of four layers of water adsorbed onto the calcium hydroxide surfaces is required to promote the catalytic effect. 相似文献
6.
Electrochemical performance of La2NiO4+δ cathode for intermediate-temperature solid oxide fuel cells
《Ceramics International》2015,41(4):5984-5991
The application of the La2NiO4+δ (LNO), one of the Ruddlesden–Popper series materials, as a cathode material for intermediate temperature solid oxide fuel cells is investigated in detail. LNO is synthesized via a complex method using ethylenediaminetetraacetic acid (EDTA) and citric acid. The effect of the calcination temperature of the LNO powder and the sintering temperature of the LNO cathode layer on the anode-supported cell, Ni–YSZ/YSZ/GDC/LNO, is characterized in view of the charge transfer resistance and the mass transfer resistance. Charge transfer resistance was not significantly affected by calcination and sintering temperature when the sintering temperature was not lower than the calcination temperature. Mass transfer resistance was primarily governed by the sintering temperature. The unit cell with the LNO cathode sintered at 1100 °C with 900 °C-calcined powder presented the lowest polarization resistance for all the measured temperatures and exhibited the highest fuel cell performances, with values of 1.25, 0.815, 0.485, and 0.263 W cm−2 for temperatures of 800, 750, 700, and 650 °C, respectively. 相似文献
7.
《Ceramics International》2016,42(9):11239-11247
In this study, Cu and Mo ions were doped in Ca3Co4O9−δ to improve the electrical conductivity and electrochemical behavior of Ca3Co4O9−δ ceramic and the performance of a solid oxide fuel cell (SOFC) single cell based on NiO-SDC/SDC/doped Ca3Co4O9−δ-SDC were examined. Cu substitution in the monoclinic Ca3Co4O9−δ ceramic effectively enhanced the densification, slightly increased the grain size, and triggered the formation of some Ca3Co2O6; however, no second phase was found in porous Mo-doped Ca3Co4O9−δ ceramics even when the sintering temperature reached 1050 °C. Substitution of Cu ions caused slight increase in the Co3+ and Co4+ contents and decrease in the Co2+ content; however, doping with Mo ions showed the opposite trend. Doping the Ca3Co4O9−δ ceramic with a small amount of Cu or Mo increased its electrical conductivity. The maximum electrical conductivity measured was 218.8 S cm−1 for the Ca3Co3.9Cu0.1O9−δ ceramic at 800 °C. The Ca3Co3.9Cu0.1O9−δ ceramic with a coefficient of thermal expansion coefficient of 12.1×10−6 K−1 was chosen as the cathode to build SOFC single cells consisting of a 20 μm SDC electrolyte layer. Without optimizing the microstructure of the cathode or hermetically sealing the cell against the gas, a power density of 0.367 Wcm−2 at 750 °C was achieved, demonstrating that Cu-doped Ca3Co4O9−δ can be used as a potential cathode material for IT-SOFCs. 相似文献
8.
《Ceramics International》2016,42(10):11772-11779
Equal amounts of Gd0.1Ce0.9O2−δ (GDC) were added to La0.65Sr0.3MnO3−δ/(Y2O3)0.08(ZrO2)0.92 (LSM/YSZ) powder either by physical mixing or by sol–gel process, to produce a porous cathode support for solid oxide fuel cells (SOFCs). The effect of the GDC mixing method was analyzed in view of sinterability, thermal expansion coefficient, microstructure, porosity, and electrical conductivity of the LSM/YSZ composite. GDC infiltrated LSM/YSZ (G-LY) composite showed a highly porous microstructure when compared with mechanically mixed LSM/YSZ (LY) and LSM/YSZ/GDC (LYG) composites. The cathode support composites were used to fabricate the button SOFCs by slurry coating of YSZ electrolyte and a nickel/YSZ anode functional layer, followed by co-firing at 1250 °C. The G-LY composite cathode-supported SOFC showed maximum power densities of 215, 316, and 396 mW cm−2 at 750, 800, and 850 °C, respectively, using dry hydrogen as fuel. Results showed that the GDC deposition by sol–gel process on LSM/YSZ powder before sintering is a promising technique for producing porous cathode support for the SOFCs. 相似文献
9.
Yttria-stabilized zirconia (YSZ)/stainless steel joints made using two commercial silver-based interlayers containing palladium (58Ag–32Cu–10Pd and 65Ag–20Cu–15Pd), were systematically analyzed for the microstructures of the interlayer matrices, interlayer–steel interface, and interlayer–YSZ interface using scanning electron microscopy (SEM) and transmission electron microscopy coupled with energy dispersive spectroscopy (TEM/EDS). In the interlayer matrix, a face-centered cubic (FCC) Cu-rich phase formed in the vicinity of the YSZ and dissolved a significant amount of Zr from the ZrO2 and minor amounts of Fe and Cr from the steel. The Cu-rich phase in the interlayer matrix in the vicinity of the steel substrate was the ordered phase Cu3Pd with antiphase boundaries (APBs) and the L12 crystal structure. Silver particles precipitated within the Cu3Pd phase in 58Ag–32Cu–10Pd; a Fe(Cr) needle-like phase, instead of Ag particles, precipitated within the Cu3Pd phase in 65Ag–20Cu–15Pd. Although no reaction products at the interlayer–steel interface were found, dislocations appeared within the Ag- and Cu-rich phases. At the interlayer–YSZ interface, two reaction products, SiO2 (impurity in YSZ) and Ti3O5 (from the reaction of YSZ with Ti impurities in the steel) were observed. Diffusion and chemical reactions led to the compositional changes and interface reconstruction, thereby yielding metallurgically sound YSZ/steel joints. 相似文献
10.
2-Phenyl ethanol (2-PEA) is an important chemical which finds several applications in perfumes, deodorants, soaps and detergents. It is prepared by different polluting and dangerous routes. The current work is concerned with production of 2-PEA by hydrogenation of styrene oxide using polyurea encapsulated catalysts (EnCat) in methanol and supercritical carbon dioxide (scCO2). Bimetallic Pd–Cu catalyst encapsulated with polyurea, Pd–Cu EnCat, is the best catalyst. The epoxide ring in styrene oxide is selectively hydrogenated to give 2-PEA in scCO2 without formation of any isomerization or deoxygenated products, which are formed in methanol. A complete conversion of styrene oxide with 100% selectivity to 2-PEA was obtained without addition of any promoter. Effects of various parameters were studied and a bifunctional site Langmuir–Hinshelwood–Hougen–Watson kinetic model was found to be in good agreement with the experimental data. The process is clean and green. 相似文献
11.
The influence of oxide–oxide interaction on the catalytic properties of Co/Al2O3 in CO hydrogenation
The influence of oxide–oxide interaction on the catalytic properties of cobalt in CO hydrogenation is investigated on the example of a Co/Al2O3 catalyst. Oxide–oxide interaction was prevented by modification of the alumina surface with magnesia. It has been shown that oxide–oxide interaction affects catalytic activity and the amount of carbon deposited on the catalyst surface. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
The reactions of mixtures of zirconium alkoxide and cerium or yttrium acetate in 1,4-butanediol at 300°C (glycothermal reaction) yielded microcrystalline tetragonal zirconia–rare earth oxide solid solutions. The products maintained large surface areas even after calcination at high temperatures. The surface area of the products with low rare earth contents strongly depended on the drying conditions because of compaction at the drying stage, and the product dried by microwave irradiation had the highest surface area. 相似文献
13.
Ralf Hansch Mohammad Rahul Reza Chowdhury Norbert H. Menzler 《Ceramics International》2009,35(2):803-811
The idea of using the sol–gel technique for producing low-cost components for solid oxide fuel cell (SOFC) application has attracted great interest. Besides its economic advantages, the sol–gel technique additionally offers the chance to reduce either the thickness of the electrolyte and therefore to reduce ohmic resistances or to lower the sintering temperature of single components like the electrolyte layer, due to the clearly reduced particle sizes of colloidal distributed particles in the sol.The work presented here deals with the development of sols and their application in combination with yttria fully stabilized zirconia mixed-oxide powders for the preparation of screen-printing pastes. Besides physical, chemical and thermal characterization of the sols, variations of the composition of the sol as well as of the pastes composed of sol and mixed-oxide powder were evaluated for preparing dense, gas-tight layers sintered at various temperatures, resulting in sufficient gas-tightness to ensure high power density SOFCs. Additionally, technological screen-printing parameters were studied.Single cell tests (50 mm × 50 mm) revealed current densities of approx. 1 A/cm2. These values are comparable to current densities obtained by cells based on normal electrolyte layers, which were prepared in parallel. 相似文献
14.
Owing to the complexity of the multivalence states of vanadium oxides in slag systems and experimental difficulties, thermodynamic properties of vanadium oxides have not been established yet. In the present study, the mixed-valence states and activities of the vanadium oxides in CaO–SiO2–VOx slag were investigated experimentally at 1873 K and oxygen partial pressures of 3.2 × 10–9 and 3.1 × 10–7 atm. After the CaO–SiO2–VOx slag had equilibrated with a platinum strip, the mixed-valence states of the vanadium oxides in the slag were estimated by performing X-ray photoelectron spectroscopy, and the activities of the vanadium oxides in the slag were calculated using the activity of vanadium in the platinum strip at equilibrium using thermodynamic equations. At an oxygen partial pressure of 3.2 × 10–9 atm, V3+ was the dominant ion and V4+ was the second most abundant ion. With increasing VOx content or basicity (CaO/SiO2 ratio), the fraction of V3+ decreased, whereas that of V4+ increased. The activity of VO1.5 was greater than those of the other vanadium oxides. On the other hand, when the oxygen partial pressure increased to 3.1 × 10–7 atm, V4+ became the dominant ion. As the slag basicity increased, the fraction of V4+ increased further, whereas that of V3+ decreased to less than that of V5+. The activity of VO1.5 was greater than those of the other vanadium oxides, limiting the effect of the slag basicity. Consequently, the valence state of vanadium oxide was affected by the slag basicity at a low oxygen partial pressure by acting as a network modifier. In contrast, at a higher oxygen partial pressure, the activity of vanadium oxide increased further but was not affected by the slag basicity because of its contribution to the network structure formation. The present findings can be applied to optimize the slag composition in steel refining or vanadium pentoxide production processes to increase the yield rate of vanadium. 相似文献
15.
Ba0.5Sr0.5Co1?xFexO3?δ (x = 0.2, 0.6, and 0.8) and Ba0.5Sr0.5Cu1?xFexO3?δ (x = 0.6 and 0.8) perovskite oxides have been investigated as cathode materials for intermediate temperature solid oxide fuel cells. All the samples synthesized by a citrate–EDTA complexing method were single-phase cubic perovskite solid solutions. Then, the thermal expansion coefficient, electrical conductivities, the oxygen vacancy concentrations, the polarization resistances (Rp), and the power densities were measured. An increase in the Co content resulted in a decrease in the polarization resistance, the electrical conductivities at low temperatures, and the inflection point of the thermal expansion coefficient, but it led to an increase in the electrical conductivities at high temperatures, the oxygen vacancy concentrations, and the maximum power densities. The Cu-based system has similar behavior to the Co-based system; yet, in terms of the electrical conductivities, high Cu content gave a better result than low content for the entire range of temperatures. 相似文献
16.
The kinetics of sulfur transfer from H2S to cuprous sulfide (digenite) at 500°C has been established by the resistance relaxation technique. The resistance measurements have been carried out by the van der Pauw method, which uses a four probe configuration. The rate of the forward reaction decreases with the increase in the activity of sulfur in the sulfide (rate a
s
–0.55
) while the rate of the backward reaction is found to be nearly independent of the sulfur activity. Based on these results, the rate limiting step for sulfur transfer reaction to digenite is shown to be: H2S (g) + 2e– = S2–(ad) + H2(g). 相似文献
17.
《Journal of the European Ceramic Society》2000,20(2):139-145
Ultrafine powders of ZrO2–Y2O3 solid solutions have been synthesized by hydrothermal treatment at 110°C. Zirconia gel, crystalline Y2O3 and various mineralizing solutions have been utilized as precursors for the hydrothermal synthesis. Yttria-stabilized zirconia (YSZ) with different Y2O3 content and characterized by different crystallite sizes have been produced by changing the hydrothermal treatment temperature, and the nature and concentration of the mineralizer solution. The role of mineralizer solutions on the crystallization-stabilization of zirconia gel at low temperature of hydrothermal treatment is discussed. 相似文献
18.
Guillermo Díaz-Sainz Manuel Alvarez-Guerra José Solla-Gullón Leticia García-Cruz Vicente Montiel Angel Irabien 《American Institute of Chemical Engineers》2020,66(9):e16299
The use of bismuth-based catalysts is promising for formate production by the electroreduction of CO2 captured from waste streams. However, compared to the extensive research on catalysts, only a few studies have focused on electrochemical reactor performance. Hence, this work studied a continuous-mode gas–liquid–solid reaction system for investigating CO2 electroreduction to formate using Bi-catalyst-coated membrane electrodes as cathodes. The experimental setup was designed to analyze products obtained in both liquid and gas phases. The influence of relevant variables (e.g., temperature and input water flow) was analyzed, with the thickness of the liquid film formed over the cathode surface being a key parameter affecting system performance. Promising results, including a high formate concentration of 34 g/L with faradaic efficiency for formate of 72%, were achieved. 相似文献
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20.
《应用陶瓷进展》2013,112(5):202-210
AbstractMixed conducting anode materials for solid oxide fuel cells are desirable in order to extend the electron transfer reaction zone for fuel gas conversion and to minimise the nickel content for achieving a redox stable anode. Partial substitution by titania in yttria stabilised zirconia (YSZ) is known to increase the electronic conductivity in reducing atmospheres. Nine different compositions were selected from the quasi ternary phase diagram according to principles used in statistical design of experiments covering the whole stoichiometric regime relevant for ionic applications. The dc electrical conductivity values increase strongly with high Ti contents under reducing (Ar–4%H2) conditions, whereas they decrease continuously with increasing Ti content under oxidising conditions (air). The results clearly show that the chosen screening process for materials selection can considerably reduce the number of samples. For solid oxide fuel cell anodes, the compositions in the YO1.5–ZrO2–TiO2 system should be restricted to low Ti contents. 相似文献