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71.
Raman spectroscopy studies of concentrated vanadium redox battery positive electrolytes 总被引:3,自引:0,他引:3
Spectroscopic changes in highly concentrated vanadium(V)-sulfate solutions to be used in the vanadium redox battery are consistent with the presence of more than one V(V)-sulfate species. The results of Raman spectroscopy indicate that the major species in highly acidic conditions are VO2SO4
–, VO2(SO4)2
3–, VO2(HSO4)2
–, VO3
–, V(V) dimers with V2O3
4+ and V2O4
2+ central units. The nature and amount of these species depends upon the V(V) and total sulfate concentrations as well as on S to V and H+ to V ratios in the positive half-cell electrolyte. V(V) forms V2O3
4+, VO2(SO4)2
3– and their copolymer species at higher total sulfate concentrations, which tends to stabilize the vanadium (V) positive electrolyte in the vanadium redox battery. The V(V) and V(IV) species show the least interaction with each other. Ageing of concentrated V(V) solutions at elevated temperature (50 °C) produces decomposition of species causing formation of V2O5 precipitates with a decrease in the amount of vanadium polymer. 相似文献
72.
Jose E. Herrera Ja Hun Kwak Jian Zhi Hu Yong Wang Charles H. F. Peden 《Topics in Catalysis》2006,39(3-4):245-255
The advantages of the atomic layer deposition (ALD) method for preparation of tungsten, vanadium, titanium, and molybdenum
oxide catalyst supported on mesoporous silica are discussed, with emphasis on the importance of synthesis conditions on dispersion,
structure and activity of the resulting materials. A suite of complementary techniques such as DRS-UV/Vis, BET, 1H-NMR, XRD, and TEM were used to study the structural properties of the supported metal oxides, and probe reactions such as
2-butanol dehydration and ethanol partial oxidation were used to demonstrate the potential advantages of the ALD-prepared
catalysts. Specifically, highly dispersed oxides of titanium, molybdenum, and tungsten oxide on mesoporous silica were synthesized
using the ALD method. It is also demonstrated that attainment of high dispersions of vanadium oxide on mesoporous silica requires
the presence of at least a single layer of titanium oxide due to the well-known poor interaction between vanadia and silica.
The highly dispersed catalysts prepared here by ALD methods exhibited superior catalytic performance relative to those prepared
using conventional incipient wetness impregnation. 相似文献
73.
Monoclinic metahewettite CaV 6 O 16 ·3H 2 O has been fabricated via thermal hydrolysis of calcium vanadate(Ca 10 V 6 O 25). High purity calcium vanadate precipitate, featuring column structure with surface area of 8.61 m2/g, can be obtained by reacting sodium orthovanadate(Na 3 VO 4) with calcium oxide at 90 ℃ for 2 h. By acidifi cation of calcium vanadate in hot water at pH of 1.0-3.0, the monoclinic metahewettite crystals with uniform particle distribution, layered structure and nonporous structure can be fabricated. With the well crystallized layered structure, CaV 6 O 16 ·3H 2 O may be a potential cathode material for secondary batteries as well as super capacitor materials. 相似文献
74.
Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons 总被引:2,自引:0,他引:2
V.G.Efremenko ;K.Shimizu ;A.P.Cheiliakh ;T.V.Kozarevskaya ;K.Kusumoto ;K.Yamamoto 《北京科技大学学报(英文版)》2014,(11):1096-1108
The objective of this investigation is to study the influence of vanadium(5.0wt%–10.0wt%) and chromium(0–9.0wt%) on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys' microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic(based on M7C3), pearlite, martensite, and austenite. Their combinations and area fraction(AF) ratios are reported to be influenced by the alloys' chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic(γ-Fe + М7С3), preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure. 相似文献
75.
为探讨银离子缓释的载体制备及载银抗菌剂的抑菌功能,采用浸渍提拉法制备银系无机抗菌材料,通过银离子的抗菌机理,调试银离子浓度对抗菌性能的影响.实验证明将TiO2与银、铜等离子复合发挥相互补充的抗菌作用,具有明显的抑菌功能. 相似文献
76.
77.
Characteristics of graphite felt electrode electrochemically oxidized for vanadium redox battery application 总被引:2,自引:0,他引:2
The graphite felt was oxidized at a positive electrode potential in sulfuric acid solution.The electrochemical performance of the treated graphite felt served as electrode for vanadium redox battery was investigated with FT-IR,SEM,XPS,BET,cyclic voltammetry and testing VRB system,respectively.The results show that the molar ratio of O to C increases from 0.085 to 0.15 due to the increase of—COOH functional groups during electrochemical oxidation treatment,and the GF surface is eroded by electrochemical oxidation,resulting in the surface area increase from 0.33 m2/g to 0.49 m 2/g.The VRB with modified GF electrode exhibits excellent performance under a current density of 30 mA/cm 2 .The average current efficiency reaches 94%and average voltage efficiency reaches 85%.The improvement of electrochemical activity for the electrode is ascribed to the increase of the number of—COOH group and the special surface of GF. 相似文献
78.
工业VO2薄膜的电阻突变及其稳定性 总被引:4,自引:0,他引:4
以工业V2O5为原料,采用热分解法和还原法制备工业VO2薄膜。研究了制备工艺参数对电阻突变的影响及其在自然放置条件下的稳定性。结果表明:1)VO2薄膜的电阻突变达到了2.0-3.4个数量级,突变温度约为35℃,比纯VO2薄膜突变温度约低33℃;2)石英玻璃上的VO2薄膜的电阻突变数量级比普通玻璃上的大;3)H2还原法制备的VO2薄膜电阻突变数量级比N2热分解法制备的大;4)在自然放置条件下短时间内VO2薄膜可承受连续、反复多次的电阻突变,其突变数量级降低不多,突变温度滞后几乎没有变化;5)同等条件下石英玻璃上的VO2薄膜的电阻突变数量级降低较小、稳定性较好。 相似文献
79.
Fe-8-12Cr ferritomartensitic steels are widely used in the power generation, petrochemical and nuclear industries where they
are subject to high operating temperatures and stresses. Resistance to creep deformation is therefore a critical materials
property. One method of providing creep resistance is to precipitate a fine homogeneous distribution of vanadium nitride (VN)
particles in the matrix. Maximizing this precipitation hardening effect requires a high nitrogen content, but this could cause
gas bubble formation during conventional fabrication processes. It is therefore necessary to determine how much N can be added
without encountering such problems. Phase stability calculations, using Thermo-Calc, were carried out to find high-N compositions
to optimize the fraction of VN and the fabrication route for obtaining fine particles. Several experimental compositions,
including nine high-nitrogen alloys, were fabricated as ingots; out of these, two exhibited porosity Thermo-Calc predicts
that, in all of the high-nitrogen alloys, nitrogen gas is a stable phase around the solidus temperature. It is evident that
porosity cannot simply be predicted from the presence of the gas phase on the equilibrium diagram. However, detailed analysis
of the equilibrium phases predicted in these alloys, including their variation with composition, allowed a porosity criterion
to be obtained. This criterion links porosity formation to the nature of the liquid-to-solid transformation. Further calculations
were carried out to predict the dependence of gas phase evolution on both composition and pressure. Thermodynamic calculations
are a valuable tool for the design of these industrially important alloys. Input from experimental data has enabled the refinement
of the initial design criteria such that it should now be possible to propose compositions with high VN hardening but without
the risk of porosity.
This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference
and Exposition. Columbus, Ohio, 18–20 October, 2004. 相似文献
80.
Nanocrystalline titania films codoped with aluminum and boron were prepared by cathodic vacuum arc deposition. In the process, titanium alloy target was used under an O2/Ar atmosphere, and sensitization of films were carried out by natural dye-sensitized complex in anhydrous ethanol. The structure, surface morphology and UV-vis spectra of titania films codoped were measured by X-ray diffraction analysis, scanning electron microscopy and ultraviolet-visible spectrometer. Theas-deposited films are found to be amorphous. The films annealed were examinedto be of anatase structure with orientation along the (101) planes, the averagecrystal size is in the range between 41 and 45 nm. SEM results show that thereare some pores in the codoped titania films, the optical properties of the dye-sensitized films were also measured which reveals that the spectral responses of films shift to the visible region. Under simulated sunlight illumination, the overall energy conversion efficiency of dye-sensitized nanocrystalline solar cell is 0.9%. 相似文献