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1.
The solid-phase interaction in the V2O5-Nb2O5-MoO3 system has been investigated, and the formation of a solid solution bounded by the compositions MoNb2V4O18 ? δ, Mo2NbV5O21 ? δ, Mo2Nb3V3O21 ? δ, and Mo4Nb9V9O57 ? δ has been found (δ is nonstoichiometry). In the V2O5?Nb2O5 system, the formation of three compounds is verified, namely, VNbO5 (tetragonal structure), VNb9O25, and V2Nb23O62.5. The first two compounds are isostructural and form a continuous solid solution with tetragonal symmetry. A new compound of the composition Mo3NbVO14 ? δ has been synthesized. This compound is isostructural to the Mo3Nb2O14 compound described in the literature and forms a tetragonal solid solution with it. The phase equilibria in the V2O5-Nb2O5-MoO3 system in the subsolidus region have been determined.  相似文献   

2.
Compounds described as V2O3(XO4)2, where X = S or Se, were prepared from vanadium(V) oxide mixtures with concentrated sulfuric and selenic acids. The physicochemical properties of the products were studied; for V2O3(SeO4)2, the crystal structure was determined by powder X-ray diffraction and neutron diffraction, and its key differences from the structure of V2O3(SO4)2 were identified. V2O3(SeO4)2 crystallizes in the monoclinic system with the unit cell parameters a = 15.3831(2)Å, b = 5.54096(5)Å, c = 9.71644(7)Å, β = 111.886(1)°, V = 768.51Å3, space group C2/c (no. 15).  相似文献   

3.
It has been demonstrated that Co2V2O7 and InVO4 react with each other forming a new compound of the Co2InV3O11 formula, when their molar ratio is equal to 1:1, or among CoCO3, In2O3 and V2O5, mixed at a molar ratio of 4:1:3. This compound melts incongruently at the temperature of 960±5°C, depositing crystals of InVO4. It crystallizes in the triclinic system and the unit cell parameters amount to: a=0.6524(6) nm, b=0.6885(5) nm, c=1.0290(4) nm, α=96.5°, β=104.1°, γ=100.9°, Z=2. The phase equilibria being established in the Co2V2O7–InVO4 system over the whole components concentration range up to the solidus line were described.  相似文献   

4.
Reduced Clusters with Remarkable Topological and Electronic Properties of the Type of [V18O42(X)]n? (X = SO4, VO4) with Td-Symmetry and Related Clusters [V(18—p)As2pO42(X)]m? (X = SO3, SO4, H2O; p = 3, 4) The novel cluster-compounds Na6[V18O42H9(VO4)] · 21 H2O, (NH4)8[V18O42(SO4)] · 25 H2O, K6[V15As6O42(H2O)] · 8 H2O, (NH4)6[V14As8O42(SO3)], (NH4)6[V14As8O42(SO4)] and [N(CH3)3]4[4V14As8042(H20)] were prepared and characterized by IR- and UV/Vis/NIR-spectroscopy, magnetic measurements and complete crystal structure analysis. For structural data see Inhaltsübersicht. Topological relations to the rhombicuboctahedron spanned by 24 0-atoms of the genuine hypothetical a-Keggin ion, at which the square planes are capped by V?O or As2O groups, are discussed. Of particular interest are the ?extended”? Keggin ions [V18O42(X)]n- (X = SO4 VO4), (formaly derived from the hypothetical genuine a-Keggin ion by addition of six V?O groups) which have quite different electron populations in spite of the same structure of their cluster shells.  相似文献   

5.
2‐Amino‐3‐hydroxypyridinium dioxido(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)vanadate(V), (C5H7N2O)[V(C7H3NO4)O2] or [H(amino‐3‐OH‐py)][VO2(dipic)], (I), was prepared by the reaction of VCl3 with dipicolinic acid (dipicH2) and 2‐amino‐3‐hydroxypyridine (amino‐3‐OH‐py) in water. The compound was characterized by elemental analysis, IR spectroscopy and X‐ray structure analysis, and consists of an anionic [VO2(dipic)] complex and an H(amino‐3‐OH‐py)+ counter‐cation. The VV ion is five‐coordinated by one O,N,O′‐tridentate dipic dianionic ligand and by two oxide ligands. Thermal decomposition of (I) in the presence of polyethylene glycol led to the formation of nanoparticles of V2O5. Powder X‐ray diffraction (PXRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the synthesized powder.  相似文献   

6.
Chemical transport of the vanadium oxides V2O5, V3O7, and V6O13 The suitability of water and some halogenating transport agents (NH4Cl, NH4Br, I2) for the chemical transport (temperature gradient 850/750 K) of V2O5, V3O7, and V6O13 has been investigated. Transport rates for V2O5 and V6O13 could be measured and reproduced. The best transport agent for V2O5 is NH4Cl or H2O. For V3O7 a combination of the transport agents I2/H2O give the best results and for V6O13 the combination of NH4Br/H2O was most appropriate.  相似文献   

7.
The effect of the method used for the synthesis of NH4V3O7 on its morphology, textural parameters, and optical properties was studied. Ammonium vanadate NH4V3O7 was prepared by treating NH4VO3 in the presence of citric acid under hydrothermal (4.0 ≤ pH ≤ 5.5, T = 180–200°C, 48 h) and microwave–hydrothermal (3.5 ≤ pH ≤ 5.0, T = 180–220°C, 20 min) conditions. Self-assembled NH4V3O7 microcrystals crystallizing in monoclinic system with unit cell parameters a = 12.247(5) Å, b = 3.4233(1) Å, c = 13.899(4) Å, β = 89.72(3)°, and V = 582.3(4) Å3 (space group P21) were shown to be formed independently of the method used to treat the reaction mixture. The morphology of NH4V3O7 particles was shown to depend on рН of the reaction mass and the method of synthesis. The structural features of NH4V3O7 were studied by IR, UV, and Vis spectroscopy, and the optical bandgap was determined.  相似文献   

8.
>From Small Fragments to New Poly‐alkoxo‐oxo‐metalate Derivatives: Syntheses and Crystal Structures of K4[VIV12O12(OCH3)16(C4O4)6], Cs10[VIV24O24(OCH3)32(C4O4)12][VIV8O8(OCH3)16(C2O4)], and M2[VIV8O8(OCH3)16(VIVOF4)] (M = [N(nBu)4] or [NEt4]) By solvothermal reaction of ortho‐vanadicacid ester [VO(OMe)3] with squaric acid and potassium or caesium hydroxide the compounds K4[VIV12O12(OCH3)16(C4O4)6] ( 2 ) and Cs10[VIV24O24(OCH3)32(C4O4)12][VIV8O8(OCH3)16(C2O4)] ( 3 ) could be syntesized. With tetra‐n‐butyl‐ or tetra‐n‐ethylammonium fluoride [N(nBu)4]2[VIV8O8(OCH3)16(VIVOF4)] ( 4 ) and [N(Et)4]2[VIV8O8(OCH3)16(VIVOF4)] ( 5 ) could be isolated. In 2 and 3 the corners of a tetrahedron or cube resp. are occupied by {(VO)3(OMe)4} groups and connected along the edges of the tetrahedron resp. cube by six or twelve resp. squarato‐groups. The octanuclear anions in the compounds 3 , 4 , and 5 are assumedly built up by fragments of the ortho‐vanadicacid ester [VO(OMe)3]. Around the anions C2O42— or VOF4 these oligormeric chains are closed to a ring . Crystal data: 2 , tetragonal, P43, a = 18.166(3)Å, c = 29.165(7)Å, V = 9625(3)Å3, Z = 4, dc = 1.469 gcm—3; 3 , orthorhombic, Pbca, a = 29.493(5)Å, b = 25.564(4)Å, c = 31.076Å, V = 23430(6)Å3, Z = 4, dc = 1.892 gcm—3; 4 , monoclinic, P21/n, a = 9.528(1)Å, b = 23.021(2)Å, c = 19.303(2)Å, β = 92.570(2)°, V = 4229.8(5)Å3, Z = 2, dc = 1.391 gcm—3; 5 , monoclinic, P21/n, a = 16.451(2)Å, b = 8.806(1)Å, c = 23.812(1)Å, β = 102.423(2)°, V = 3368.7(6)Å3, Z = 2, dc = 1.534 gcm—3.  相似文献   

9.
The results concerning the synthesis, structure and thermal properties of V2O5-MoO3-Ag2O samples in the molybdenum rich region of ternary system are presented in the form of quasi-binary systems: β-AgVO3-β-Ag2MoO4, AgVMoO6-MoO3, AgVMoO6-Ag2Mo4O13, AgVMoO6-Ag2Mo2O7, AgVMoO6-β-Ag2MoO4 and also of the system in which at V2O5/MoO3 molar ratio 3:7 the content of Ag2O was variable. The ternary phase AgVMoO6 was not described earlier in the literature.  相似文献   

10.
Preparation and Crystal Structure of Potassium Magnesium Oxocuprate/-vanadate: KMg2Cu2V3O12 . Single crystals of KMg2Cu2V3O12 were prepared by solid state reactions below the melting point of the reaction mixture (K2CO3, MgCO3, CuO, V2O5). It crystallizes with monoclinic symmetry space group C? C2/c, a = 12.1592 Å, b = 12.7204 Å, c = 6.8557 Å, β = 111.73°, Z = 4. The structure type is characterized by VO4 tetrahedra, twisted CuO4 square units, MgO6 octahedra and a special 2 + 4 + 2 coordination around the potassium ion.  相似文献   

11.
The hydrothermal reaction of VOSO4, As2O5, piperazine and H2O produces [H2N(CH2)4NH2]4[β‐As8V14O42(SO4)]·2HSO4 ( 1 ), which is the first arsenic‐vanadium cluster containing a spherical β‐As8V14O42 shell. The structure of this compound was characterized by single crystal X‐ray diffraction, elemental analysis, TG, and IR spectrum. Crystal data for 1 : Orthorhombic, Cmcm, a = 15.369(1) Å, b = 16.404(1) Å, c = 25.772(1) Å, V = 6497.4(9) Å3, Z = 4.  相似文献   

12.
Magnetic Properties of Ti3?xMxO5 Phases (M = V3+, Cr3+, Nb4+) The magnetic properties of Ti3?xVxO5, Ti3?xCrxO5, and Ti3?xNbxO5 phases are reported. In the case of V3+ and Cr3+ the magnetic leaping-temperature decreases, however Nb4+ shift the phase-transition towards higher temperatures. All samples show a “memory-effect” in magnetic properties, i. e. the results of heating- and cooling-cycles are higher susceptibilities of the α-phase of Ti3O5. Endowed Ti3O5 phases show for the α- and β-Ti3?xMxO5 til the leap Curie-Weiss characteristic in 1/X vs. temperature measurements. Exception is β-Ti3?xNbxO5, its susceptibility is independend of the temperature up to x ? 0.3.  相似文献   

13.
Additional Magnetic Examinations of Ti3?xMxO5-Phases (M = Al3+, Fe2+, Mn2+, Mg2+) with a Contribution about CrTi2O5 Ti3?xMxO5 was prepared with M = Al3+, Fe2+, Mn2+, and Mg2+. Die magnetic properties of this phases were examinated by the Faraday method in respect to the temperature. The well known magnetic effect of Ti3O5 near 450 K is shifted to lower degrees if Ti is replaced by Al, Fe, Mn, or Mg. Compared to Ti3?xVxO5 and Ti3?xCrxO5 the stability of the low temperature-form of Ti3O5 is much more reduced in Ti3?xMxO5 (M = Al, Fe, Mn, Mg). The crystal structure investigation of CrTi2O5 explained the anomalous behaviour of the Cr3+ and V3+ doped Ti3O5.  相似文献   

14.
Several TiO2 and γ‐Al2O3 supported catalyst systems were prepared by a novel way and characterized by X‐ray diffraction, Raman spectroscopy and BET surface area measurement. The results show: (1) all the samples, including MoO3/TiO2, WO3/TiO2, V2O5/TiO2, FeSO4/γ‐Al2O3, Al2 (SO4)3/γ‐Al2O3, K2CO3/‐Al2O3 and so on, prepared by impregnating TiO2·H2O or pseudo‐boehmite AlO(OH) with the active components then calcining at a high temperature exhibit much larger surface areas than that of pure TiO2 or γ‐Al2O3 calcined at the same temperature; (2) the surface area of the sample increases with the increase in the coverage of active component on the surface of the support; (3) when the content of active component reaches its utmost monolayer dispersion capacity, the surface area of the sample is the largest, and then decreases when the content of active component exceeds its dispersion threshold.  相似文献   

15.
The depression of the freezing point of molten KNO3, as solvent, was measured after the addition of small concentrations of the solutes: 1. WO3, K2WO4, K2W2O7 and 2. V2O5, Cs2V6O16 and Rb2V6O16. DTA-apparatus was used in the measurements. The results showed that the investigated tungstates and vanadates were dissociated in the melt with the formation of monotungstate (WO4)2? and orthovanadate (VO4)3?-ions.  相似文献   

16.
V2O3 single crystals have been grown by chemical vapor transport with HCl and TeCl4. Crystals grown with TeCl4 contain V3O5, as verified by X-ray analysis, and this affects the low temperature transition. Polycrystalline V2O3 has also been prepared containing various amounts of V(IV). Magnetic data for these samples demonstrate the sensitivity of V2O3 to small substitutions of V(IV) for V(III). A similar substitution of Ti(IV) into V2O3 does not result in any change in the transition temperature, although the magnitude of the transition decreases.  相似文献   

17.
Investigation of Chemical Transport in the V2O3/VO2 System The suitability of the transport agent HgCl2 for chemical transport experiments (temperature gradient 1 173/1 113 K) in the system V2O3/VO2 has been investigated. For a constant admixture of transport agent it could be observed that the transport rate, starting with V3O5, increases with increasing ratio O/V for the Magnéli-phases VnO2n–1 of this system (n′(V3O5) = 6 mg/d to n′(V9O17) = 20 mg/d), while the values for n′ = 12 mg/d are even for V2O3 and VO2.  相似文献   

18.
Synthesis was performed and physicochemical properties were studied for the M4V2O3(SO4)4 complexes, where M = K, Rb, or Cs. Their crystal structures were determined using the set of data from X-ray diffraction and neutron diffraction studies. All compounds crystallize in a triclinic lattice (space group \(P\bar 1\), Z = 2) with the parameters: a = 7.7688(2), 7.8487(1), 8.1234(1) Å; b = 10.4918(3), 10.8750(2), 11.1065(1) Å; c = 11.9783(4), 12.1336(2), and 11.8039(1) Å; α = 76.600(2)°, 77.910(1)°, 79.589(1)°; β = 75.133(2)°, 75.718(1)°, 87.939(1)°; γ = 71.285(2)°, 72.189(1)°, 75.567(1)°; V = 881.78(5), 945.42(3), 1014.34(2) Å3 for K, Rb, Cs, respectively. The structure of M4V2O3(SO4)4 was found to be formed by discrete complex anions V2O3(SO4) 4 4? incorporating two oxygen-bridged vanadium atoms in a distorted octahedral oxygen environment. The sulfate groups are coordinated by the vanadium atoms in the chelating mode with a large scatter of S-O interatomic distances and OSO angles. Every VO6 octahedron has a short terminal vanadium-oxygen bond with a length of about 1.6Å. The V2O3(SO4) 4 4? complex anions in potassium and rubidium compounds differ from that in Cs4V2O3(SO4)4 in the type of symmetry and mutual spatial orientation. The vibrational spectra were presented and interpreted in line with the structural analysis data.  相似文献   

19.
In this work, the possible synergy effects between Bi2O3, MoO3 and V2O5, and between Bi2Mo3O12 and BiVO4, were investigated. The catalytic activity of the ??mechanical mixture?? of these compounds was measured. The mixture containing 36.96?mol% Bi2O3, 39.13?mol% MoO3 and 23.91?mol% V2O5 (21.43?mol% Bi2Mo3O12 and 78.57?mol% BiVO4), corresponding to the compound Bi1?x/3V1?x Mo x O4 with x?=?0.45 (Bi0.85V0.55Mo0.45O4), exhibited the highest activity for the selective oxidation of propylene to acrolein. The mixed sample prepared chemically by a sol?Cgel method possessed higher activity than that of mechanical mixtures.  相似文献   

20.
A Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of pure V2O3 and 14 samples of vanadium‐containing slags in the CaO‐MgO‐Al2O3‐SiO2 system in the temperature range 1875–2625 K. The system was calibrated using gold in the liquid state as the standard. Vaporization was carried out from double tungsten effusion cells. First it was shown that, in vapor over V2O3 and the vanadium‐containing slags in the temperature range 1875–2100 K, the following vapor species were present: VO2, VO, O, WO3 and WO2, with the latter two species being formed as a result of interaction with the tungsten crucibles. The temperature dependencies of the partial pressures of these vapor species were obtained over V2O3 and the slags. The ion current comparison method was used for the determination of the V2O3 activities in slags as a function of temperature with solid V2O3 as a reference state. The V2O3 activity coefficients in the slags under investigation indicated positive deviations from ideality at 1900 K and a tendency to ideal behavior at 2100 K. It was shown that the V2O3 activity as a function of the slag basicity decreased at 1900 K and 2000 K and was practically constant in the slag melts at 2100 K. The results are expected to be valuable in the optimization of slag composition in high‐alloy steelmaking processes as well as for their environmental implications. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

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