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1.
Chances for estimating the FeO/Fe2O3tot ratio in rocks by the K and L series of X-ray fluorescence spectra are studied. The errors in the determination of FeO/Fe2O3tot by the intensity ratio of the Kβ2,5/Kβ1,3 and Lβ/Lα1,2 lines are compared. The relative standard deviation of determining FeO using a set of 49 standard samples of eruptive rocks varies in the range 5–16%, depending on the ratio FeO/Fe2O3tot and the concentration of FeO. The better precision is attainable for a ratio above 0.45 at a FeO concentration in the range 5–15%. For samples of andesites and basalts, the relative standard deviation is better than 4%, for rocks of the granite family it is 23% at FeO concentrations below 3%. For samples of metamorphic and sedimentary rocks, the error of FeO determination is higher than that for the eruptive ones. For samples with the ratio FeO/Fe/Fe2O3tot < 0.25, the deviation may exceed 30 rel %. In contrast to chemical analysis, the X-ray fluorescence method appears advantageous in time and cost of sample preparation and can be used for routine analysis in geochemical research.  相似文献   

2.
A new molybdophosphate (NH4)8{Mo2VO4[(Mo2VIO6)CH3C(O)(PO3)2]2}·14H2O (1), has been synthesized by the reaction of {Mo2VO4(H2O)6}2+ fragments with 1-hydroxyethylidenediphosphonate (hedp HOC(CH3)(PO3H2)2), and it is characterized by 31P NMR, IR, UV, element analysis, TG and single-crystal X-ray analysis. The structure analysis reveals that the polyoxoanion can be described as two {(Mo2VIO6)(CH3C(O)(PO3)2} units connected by a {Mo2VO4}2+ moiety. In the structure, the six Mo atoms are arranged into a new “W-shaped” structure, which represents a new kind of molybdophosphate.  相似文献   

3.
Solid-phase interactions in the V2O5-Ta2O5-MoO3 system were studied. The formation of com- pounds TaVO5 and VTa9O25 in the V2O5-Ta2O5 binary system was verified. Tetragonal VTa9O25-base solid solutions of the general formula Ta5 + 4x V5 − 4x O25 (x = 0.25–1) and TaVO5-base solid solutions of the general formula Ta x Mo1 − x V2 − x O8 − 3x (x = 0.625–1) were found to form. Subsolidus phase equilibria in the V2O5-Ta2O5-MoO3 were determined.  相似文献   

4.
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   

5.
Gravimetry in combination with X-ray phase analysis, X-ray crystallography, and X-ray densitometry were used to determine the contents of V5+, V4+, and Ti4+ ions and vacancies in solid solutions formed by the reaction of V2O5 with TiO2 in air at atmospheric pressure.  相似文献   

6.
New environmentally inorganic pigments based on Bi2O3 doped by metal ions, such as Zr4+ and Dy3+ have been developed and characterized using the methods thermal analysis, X-ray powder diffraction, and spectral reflectance data. The compounds having formula Bi2−x Dy x/2Zr3x/8O3 (x = 0.2, 0.6, 1.0, and 1.2) were prepared by the solid state reaction. Methods of thermal analysis were used for determination of the temperature region of the pigment formation and thermal stability of compounds. The incorporation of doped ions in Bi2O3 changes the color from yellow to orange and also contributes to a growth of their thermal stability. This property gives a direction for coloring ceramic glazes.  相似文献   

7.
Summary This work reports the room-temperature stabilization of the Bi4V2-xFexIIO11-1.5x γ ‘ phase, a promising ionic conductive material that finds application in solid oxide fuel cell and oxygen sensor devices. The Fe(II) cation proved to be a better stabilizer than Fe(III), which was previously used, since a lower substitution degree of V5+ is needed for the former. Powder X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry were used in these experiments.  相似文献   

8.
It is demonstrated by ESR measurements that O 2 (CO + O2) radical anions result from CO + O2 adsorption on the oxidized surface of CeO2. These radical anions are stabilized in the coordination sphere of Ce4+ cations located in isolated and associated anionic vacancies. This reaction shows an activation behavior determined by CO adsorption. The variation of O 2 (CO + O2) concentration with CO adsorption temperature suggests that surface carbonates and carboxylates participate in this reaction. In the (0.5– 10.0)%CeO2/ZrO2 system, O 2 forms on supported CeO2 and is stabilized on Ce4+ and Zr4+ cations. The stability of O 2 -Ce4+ complexes is lower on supported CeO2 than on unsupported CeO2, indicating a strong interaction between the cerium cations and the support.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 423–429.Original Russian Text Copyright © 2005 by Il’ichev, Kuli-zade, Korchak.  相似文献   

9.
Within the framework of the density functional theory (DFT), the electronic structure of monooxodioxovanadium functional groups in tetrahedral coordination, which model the active centers (ACs) of fine supported catalysts V2O5/SiO2 and V2O5/TiO2, has been analyzed. The optimal structures of three ACs as possible models of monomeric and polymeric oxovanadium forms on the carriers with low vanadium content were determined. The modified DFT method involving the time dependence of Kohn-Sham equation (TDDFT) was used for the adopted AC models to calculate the energies of the excited states, and optical spectra of the absorption in 25000–60000 cm?1 region were reconstructed on their base. The spectrum in this region is due to O → V charge transfer. The features of electronic spectra with the charge transfer for V2O5/SiO2 and V2O5/TiO2 catalysts and the vibrational spectra of three AC models corresponding to the monomeric and dimeric oxovanadium forms of the supported catalysts V2O5/SiO2 and V2O5/TiO2 were defined. The detailed interpretation of normal vibration frequencies is given. The frequencies typical of the monomeric and dimeric oxovanadium forms on the carrier surface were identified.  相似文献   

10.
The structural and electrochemical effects of electrospun V2O5 with selected redox-inactive dopants (namely Na+, Ba2+ and Al3+) have been studied. The electrospun materials have been characterised via a range of analytical methods including X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area measurements and scanning and transmission electron microscopy. The incorporation of dopants in V2O5 was further studied with computational modelling. Structural analysis suggested that the dopants had been incorporated into the V2O5 structure with changes in crystal orientation and particle size, and variations in the V4+ concentration. Electrochemical investigations using potentiodynamic, galvanostatic and impedance spectroscopy analysis showed that electrochemical performance might be dependent on V4+ concentration, which influenced electronic conductivity. Na+- or Ba2+-doped V2O5 offered improved conductivities and lithium ion diffusion properties, whilst Al3+ doping was shown to be detrimental to these properties. The energetics of dopant incorporation, calculated using atomistic simulations, indicated that Na+ and Ba2+ occupy interstitial positions in the interlayer space, whilst Al3+ is incorporated in V sites and replaces a vanadyl-like (VO)3+ group. Overall, the mode of incorporation of the dopants affects the concentration of oxygen vacancies and V4+ ions in the compounds, and in turn their electrochemical performance.
Graphical abstract ?
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11.
The crystal structure and the formation conditions of crystals of the LiFe5O8 ordered phase obtained from the solution-melt of the Bi2O3-Fe2O3-B2O3-LiCl quadruple system are refined. The crystals are black, octahedral, of cubic symmetry (space group P4332). Unit cell parameters: a = 8.3339(1) Å, V = 578.82(1) Å3, Z = 4, d calc = 4.753 g/cm3. From 6046 of the collected array I hkl 358 are independent (R int = 0.0321). As a result of anisotropic refinement of structural parameters, R 1 factor is found to be 0.0186 (wR 2 = 0.0467). Lithium atoms are in octahedral environment, Li-O is 2.109(1) Å; iron atoms are of two types: in octahedra with Fe-O (by two) distances of 1.9586(9) Å, 2.0152(9) Å, and 2.0652(10) Å and tetrahedra with Fe-O (three) 1.8848(10) Å and 1.914(2) Å. The structure is of inverted spinel type.  相似文献   

12.
The results of studies of solid solutions with the overall composition of Bi4V2 ? x Ge x O11 ? δ and Bi4Ge3 ? x V x O12 + δ are presented. The process of phase formation are studied during the synthesis of solid solution using the ceramic method and through liquid precursors. Crystallochemical parameters of the obtained compounds are determined. The size distribution of the particles is studied. Conductivity of annealed of polycrystalline samples as a function of temperature and composition is studied using the impedance spectroscopy method. The shape of impedance complex plane plots of the samples obtained in different ways is studied and analyzed.  相似文献   

13.
Ni0.5Zn0.5Fe2O4 nanofibers with addition of 0–5 wt% Bi2O3 were synthesized by calcination of the electrospun polyvinylpyrrolidone/inorganic composite nanofibers at the temperature below the melting point of Bi2O3. The effects of Bi2O3 addition on the phase structure, morphology and magnetic properties of the nanofibers were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, selected area electron diffraction and vibrating sample magnetometer. It is found that the nanofiber diameter, crystallite size and magnetic parameters can be effectively tuned by simply adjusting the amount of Bi2O3 addition. The average diameter of Ni0.5Zn0.5Fe2O4 nanofibers doped with different contents of Bi2O3 ranges from 40 to 63 nm and gradually decreases with increasing Bi2O3 content. The addition of Bi2O3 does not induce the phase change and all the samples are a single-phase spinel structure. The amorphous Bi2O3 tends to concentrate on the nanoparticle surface and/or grain boundary and can retard the particles motion as well as the grain growth, resulting in a considerable reduction in grain size compared to the pristine sample. The specific saturation magnetization and coercivity of the nanofibers gradually decrease with the increase of Bi2O3 amount. Such behaviors are explained on the basis of chemical composition, surface effect, domain structure and crystal anisotropy.  相似文献   

14.
The heteropolytungstate (NH4)20[Na2(H2O)2Ni(H2O)5{Ni(H2O)}2As4W40O140] · 61H2O is obtained by the reaction of Na27[NaAs4W40O140] · 60H2O with NiCl2 · 6H2O and NH4Cl in pH≈4.0. The structure and chemical composition are determined by X-ray diffraction analysis and element analysis. The crystal data and main structure refinement are: a = 1.33135(18) nm, b = 1.9722(3) nm, c = 3.6430(5) nm, α = 78.010(2)°, β = 82.145(2)δ, γ = 74.385(2)°, V = 8.978(2) nm3, triclinic crystal system, space group: P1, Z = 2, R1 = 0.0512, and wR2 = 0.0684(I >2σ). The four S2 sites of the big cyclic ligand [As4W40O140]28- are occupied by two Na+ and two Ni2+ respectively, and each site supplies four Od coordinating to metal ion. The coordination number of Ni2+ is six, and that of two Na+ is five and six respectively. The third Ni2+ locates outside the cyclic [As4W40O140]28- and connects with one Od, and its coordination number is six.  相似文献   

15.
Phase relations in the Zn2V2O7-Cu2V2O7 system were studied by high-temperature X-ray diffraction and differential thermal analysis. The major phase constituents of the system are solid solutions based on Zn2V2O7 and Cu2V2O7 polymorphs and their coexistence regions. The generation of α-Zn2 − 2x Cu2x V2O7 solid solution, where 0 ≤ x ≤ 0.30, leaves almost unchanged the stabilization temperature of the high-temperature zinc pyrovanadate phase. The α-Cu2 − 2x Zn2x V2O7 homogeneity range is 5 mol % Zn2V2O7. In the range 0.050 ≤ x ≤ 0.09 from 20 to ∼ 620°C, there is the two-phase field of α-Cu2V2O7 and β-Cu2V2O7 base solid solutions. At still higher temperatures, β-Zn2 − 2x Cu2x V2O7 and α-Cu2 − 2x Zn2x V2O7 coexist in the mixed-phase region. β-Zn2 − 2x Cu2x V2O7 solid solution, where 0 ≤ x ≤ 0.30, exists above 610 ± 5°C. The extent of the β′-Cu2V2O7-base solid solution is 9 to 65 mol % Zn2V2O7 at 615 ± 5°C, expanding to 0 mol % Zn2V2O7 with rising temperature. Original Russian Text ¢ T.I. Krasnenko, M.V. Rotermel’, S.A. Petrova, R.G. Zakharov, O.V. Sivtsova, A.N. Chvanova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1755–1762.  相似文献   

16.
The synthesis of new compounds based on Bi2O3 is investigated because they can be used as new environmentally friendly inorganic pigments. Chemical compounds of the (Bi2O3)1–x(Er2O3)x type were synthetized. The host lattice of these pigments is Bi2O3 that is doped by Er3+ ions. The incorporation of doped ions provides interesting colours and contributes to an increase in the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments.  相似文献   

17.
The compound [Ni(NH3)6][VO(O2)2(NH3)]2 was prepared and characterized by elemental analysis and vibrational spectra. The single crystal X-ray study revealed that the structure consists of [Ni(NH3)6]2+ and [VO(O2)2(NH3)] ions. As a result of weak interionic interactions V′···Op (Op-peroxo oxygen), ([VO(O2)2(NH3)])2 dimers are formed in the solid-state. The thermal decomposition of [Ni(NH3)6][VO(O2)2(NH3)]2 is a multi-step process with overlapped individual steps; no defined intermediates were obtained. The final solid products of thermal decomposition up to 600°C were Ni2V2O7 and V2O5.  相似文献   

18.
The flower-like phosphors of Sr2MgSi2O7: Eu2+, Dy3+ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased Sr2MgSi2O7 phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists of nano-sized whiskers which are detected for the first time in Eu2+ and Dy3+ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr2MgSi2O7: Eu2+, Dy3+ nanostructure. Finally, the optical properties of flower-like Sr2MgSi2O7 nanostructure have been characterized by photoluminescence (PL) spectra.  相似文献   

19.
Microstructure and conduction of ceramic composites Bi2CuO4 + xBi2O3 (x = 5, 10, 15, 20 wt %) near the eutectic melting point (770°C) are studied. Bismuth oxide, initially randomly distributed over the ceramics bulk, after quenching from temperatures exceeding the eutectic melting point, becomes localized at triple junctions and grain boundaries in Bi2CuO4, which is caused by wetting grain boundaries and forming a liquid-channel structure. The jumpwise change in the composites’ conductivity near 730 and 770°C caused by polymorphic transformation of Bi2O3 and the eutectic melting with simultaneous formation of a liquid-channel structure. Transport numbers of the oxygen ion are measured at 770°C by coulomb-volumetric method. The conduction by oxygen ions increases in the composites with decreasing average size of Bi2CuO4 crystallites.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 596–601.Original Russian Text Copyright © 2005 by Lyskov, Metlin, Belousov, Tret’yakov.  相似文献   

20.
Measurements on a circulation static setup with subsequent XRD analysis of quenched solid phases were used to study phase equilibria implicated in the thermal dissociation of SmMn2O5over the temperature and pressure ranges from 973 to 1123 K and from 10?3 to 10?16 Pa, respectively. The thermal dissociation of SmMn2O5 results in the sequential formation of constant-composition phases: SmMn2O5 → SmMnO3 + Mn3O4 + O2 → SmMnO3 + MnO + O2 → Sm2O3 + MnO + O2. The temperature dependence of the equilibrium oxygen pressure for the observed monovariant phase equilibria was used to calculate the thermodynamic characteristics of dissociation and formation of SmMn2O5 and SmMnO3 from the elements.  相似文献   

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