- Crossed-beam chemiluminescent reactions of titanium and vanadium with O2
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Titanium and vanadium have been reacted with O2 under crossed-beam conditions to form the TiO A 3Φ, B 3Π, C 3Δ, and E 3Π states and the VO B 4Π state.By heating and seeding the O2 nozzle beam the Ti reaction has been studied at relative collision energies of 4.0, 7.6, and 13.3 kcal/mol, and the V reaction at 3.9, 6.9, 7.6, and 13.1 kcal/mol.Computer simulations of the spectra yield relative rates for formation of TiO(A) and VO(B) vibrational states, which are slightly more excited than the prior model predictions.Increasing the relative collision energy does increase the production of all the electronically excited states, but the VO B state population does not increase as quickly as expected from the prior model.The dependence of the chemiluminescent signals on the metal source temperature suggests reaction of ground state Ti to formTiO(A), but metastable V to form VO (B).
- Parson, J. M.,Geiger, L. C.,Conway, T. J.
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- A clean process of preparing VO as LIBs anode materials via the reduction of V2O3 powder in a H2 atmosphere: Thermodynamic assessment, isothermal kinetic analysis, and electrochemistry performance evaluation
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VO is one of the most promising anode materials for lithium ion batteries (LIBs). Herein, we present the clean preparation of VO powder via reduction of V2O3 powder under high-purity H2. Thermodynamic calculation and V–O phase diagram analysis were carried out to ensure reasonable oxygen potential conditions. Isothermal reduction experiments and kinetic analysis using thermogravimetric analysis (TGA) were then performed at 1623 K, 1648 K, and 1673 K under a pure H2 gas flow. The reduction of V2O3 powder appears to obey an unreacted shrinking core model and can be divided into two steps. The first step was controlled by a chemical reaction, the kinetics of which can be described as G(α) = [-ln(1-α)]1/3 with an apparent activation energy of 107.3 kJ·mol?1. The second stage was controlled by gas diffusion, the kinetics of which can be described as G(α) = [1-(1-α)1/3]1/2 with an apparent activation energy of 45.5 kJ·mol?1. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) also were employed for characterizing the morphology of the prepared VO powder. As a result, when the VO was served as the LIBs anode material, the resulting electrodes exhibited a high specific capacity (843 mAh·g?1 after 30 cycles) and remarkable cyclic stability.
- Jin, Xin,Lv, Xuewei,Pei, Guishang,Xiang, Junyi,Zhong, Dapeng
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- Reactions of Atomic Scandium, Titanium, and Vanadium with Molecular Water at 15 K
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Scandium, titanium, and vanadium metal atoms were cocondensed with water molecules in an argon matreix at 15 K.The atomic metals were observed to insert spontaneously into the OH bond of water to form the HMOH molecule, which was found to be nonlinear in
- Kauffmann, J. W.,Hauge, R. H.,Margrave, J. L.
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- Kinetics of Neutral Transition-Metal Atoms in the Gas Phase: Oxidation of Sc(a2D), Ti(a3F), and V(a4F) by NO, O2, and N2O
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The oxidation kinetics of gas-phase, ground-state Sc(a2D), Ti(a3F), and V(a4F) atoms by NO, O2, and N2O is studied in 0.80 Torr of He buffer gas at 300 +/- 5 K.The metal atoms are created in a hollow cathode sputtering source before entering a fast flow reactor.The reactions are monitored by laser-induced fluorescence of the metal atom reactant.All nine M + OX -> MO + X bimolecular oxygen atom transfer reactions are inefficient at 300 K with rate constants in the range 0.45 x 10-12 to 10 x 10-12 cm3s-1.This indicates activation energies not larger than2-4 kcal mol-1 in all cases.The substantial range of reaction rates for a particular metal with the three different oxidants contrasts with the remarkable similarity of rates for all three metal atoms with each oxidant.The rate constants for reaction of each metal with the three oxidants fall in the order kNO > kO2 > kN2O, opposite to the normal expectation of decreasing activation energy with increasing exothermicity.The rate constant ordering kSc > kV > kTi for each oxidant and the small activation energies are interpreted in terms of an electron-transfer mechanism from neutral M + OX reactant surfaces to ion-pair M+O- + X product surfaces.
- Ritter, David,Weisshaar, James C.
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- Reactions of V2O5, Nb2O5, and Ta2O5 with AlN
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Reactions of vanadium, niobium, and tantalum pentoxides with aluminum nitride have been studied using X-ray diffraction. At temperatures from 1000 to 1600°C, we have identified various V, Nb, and Ta nitrides. The composition of the niobium and tantalum ni
- Chumarev,Mar'evich,Larionov,Dubrovskii, A. Ya.
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- Refinement of the V-O phase diagram in the range 25-50 at % oxygen
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The boundaries of the V14O6 + V x O z two-phase region in the V-O system at temperatures from ? 1050 to ? 1650 K have been determined experimentally. The V-O phase diagram has been refined in the range 25-50 at
- Davydov,Rempel
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- Phase transitions and electrical transport in the mixed-valence V 2+/V3+ oxide BaV10O15
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BaV10O15 can be regarded as a Ba-doped V 2O3 in which the Ba2+ ions substitute in the O2- close-packed layers. The Ba2+ ions order within these layers and direct the occupation of the octahedral sites by V2+ and V3+ ions resulting in a structure with subtle differences from that of V2O3 which can be described in Cmca at room temperature. Magnetic susceptibility data show evidence for two phase transitions at 135 and 40K. The higher temperature transition at 135K is shown to be structural in origin to another orthorhombic form, Pbca. The structural transition temperature, Ts, decreases with decreasing V2+ content to a minimum value of 105K. Crystallographic and DSC data support a first-order transition driven by partial bond formation which results in a 7% reduction in the distance between two of the five crystallographically distinct V atoms. There is no conclusive crystallographic evidence for V 2+/V3+ charge ordering in either the Cmca or Pbca forms. Electrical conductivity data show semiconducting behavior above Ts which can be fitted to a small polaron hopping model for the most reduced samples (Ts=135K). The same sample shows a sharp but not discontinuous decrease in conductivity below Ts, consistent with carrier removal due to bond formation. More oxidized materials with T s=105K show a more subtle anomaly. Evidence for correlated (Efros-Shklovskii) variable-range hopping at low temperatures is seen in the Ts=105K sample from analysis using a Hill-Zabrodski (logdE vs. logT) plot. Thermopower data on the Ts=135K material show an anomalously small value of S～+1μV/K at room temperature which increases to >+200μV/K upon cooling to 90K. Plots of dS/dT show evidence for the T s=135K phase transition. These results are not consistent with a simple one carrier model for small polaron hopping assuming that the V 2+ ions are the carriers, which would predict S～-100μV/K, but seem to demand a two carrier model with n～p at room temperature for which n-type carriers are trapped as a result of bond formation at the phase transition as temperature is lowered. The lower temperature phase transition near 40K is magnetic in origin and will be discussed in a subsequent publication.
- Bridges,Greedan
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- Magnetic properties of (Mn1-xVx)Sb2O4 with one-dimensional magnetic arrays
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The magnetic properties of mangan-vanadium antimonate solid solution (Mn1-xVx)Sb2O4 (x = 0 to 0.6) with the tetragonal TX2O4 structure (T = Pb4+, Sn4+; X = Pb2+ or T = Mn2+, Fe2+, Co2+, Ni2+; X = Sb3+, As3+) were investigated. Magnetic measurements on the polycrystalline specimens have shown that characteristic ferromagnetic behavior appears in the case that x is larger than 0.1, whereas the final compound MnSb2O4 is an antiferromagnet with the Neel temperature TN = 60.5 K. The magnetic isotherms of the solid solution at low temperatures show ferromagnetic jumps at low fields but do not tend to saturate up to 5 T. The zero-field cooling magnetic susceptibility has a maximum at Tc = 57 K, which is independent of both the vanadium concentration x and the frequencies of the applied external fields.
- Abe,Yoshii,Kitazawa
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- Trends in the Optical Signatures for Transition-Metal Oxide Carbonyl Complexes. Evaluation of Transition-Metal Carbonyl, M(CO)x, Binding Energies
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Transition-metal atoms entrained in argon, helium, and CO are oxidized with ozone (O3) and nitrogen dioxide (NO2) to study the nature of the metal atom complexation with CO.We establish a method for evaluating M-CO binding energies through comparison of the chemiluminescent emission from the oxidation of argon- and CO-entrained transition-metal atoms.These studies have thus far yielded Ebinding(Ti(CO)x) ca. 1.75 eV and Ebinding(NiCO) ca. 1.10 eV, the latter in excellent agreement with previous experimental and theoretical evaluations of the Ni-CO bond energy.We identify the optical signatures for transition-metal oxide carbonyl (MOCO) complexes formed in the oxidation of M(CO) complexes.We outline trends in the nature of the observed metal oxide complex emissions.The current study suggests a method for obtaining the spectra of transition-metal carbonyl (M(CO)x, x=1,2) complexes.
- McQuaid, M. J.,Morris, K.,Gole, J. L.
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- Preparation of nanocrystalline VOy by high-energy ball milling
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We report high-energy milling of macrocrystalline nonstoichiometric cubic vanadium monoxide (V Oy) powder in a planetary ball mill lined with stabilized zirconia. The results indicate that milling of macrocrystalline VOy powder at 500 rpm for more than 2 h considerably broadens diffraction line profiles, with no changes in the crystal structure of the vanadium monoxide, VO1.00. Microstructural examination of vanadium monoxide powder by high-resolution scanning electron microscopy and X-ray diffraction indicates that highenergy ball milling can be used to produce vanadium monoxide powder with an average crystallite size within 23 nm.
- Valeeva,Schroettner,Rempel
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- Development and structure elucidation of new VO2+, Mn2+, Zn2+, and Pd2+ complexes based on azomethine ferrocenyl ligand: DNA interaction, antimicrobial, antioxidant, anticancer activities, and molecular docking
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An organometallic azomethine ferrocenyl ligand (FCAP) and its transition metal complexes ([M (FCAP)2], where M = VO2+, Mn2+ cations, and [M (FCAP) (CH3COO? or NO3?)], where M = Zn2+/s
- Aljohani, Enas T.,Shehata, Mohamed R.,Alkhatib, Fatmah,Alzahrani, Seraj Omar,Abu-Dief, Ahmed M.
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- Synthesis, spectral, thermal and insulin-enhancing properties of oxovanadium(IV) complexes of metformin Schiff-bases
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A series of VO2+ complexes of Schiff-bases of metformin with each of salicylaldehyde (HL1); 2,3-dihydroxybenzaldehyde (H2L2); 2,4-dihydroxybenzaldehyde (H2L3); 2,5-dihydroxybenzaldehyde (H2L4); 3,4-dihydroxybenzaldehyde (H2L5); and 2-hydroxynaphthaldehyde (HL6) were synthesized by template reaction. The new compounds are characterized through elemental analysis, conductivity measurements, magnetic moment, IR, UV–Vis, ESR and mass spectroscopy. The complexes have square pyramidal structure with μ values of pentacoordinated vanadyl ion. TG, DTG and DTA confirm the proposed stereochemistry, and a mechanism of thermal decomposition was suggested. Mice treated with the complexes [VOL1H2O]·1?H2O and [VOHL4H2O]·2H2O showed glucose-lowering effect of 59.31, 58.79% (20?mg?kg?1) and 64.98, 74.8% (40?mg?kg?1) compared to metformin.
- Mahmoud, Marwa A.,Zaitone, Sawsan A.,Ammar, Alaa M.,Sallam, Shehab A.
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- The structure of an ultrathin VOx (x ≈1) film grown epitaxially on TiO2 (110)
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The analysis by means of multiple scattering cluster (MSC) calculations of full 2π V 2p, Ti 2p and O 1s X-ray photoelectron diffraction (XPD) patterns from an ultrathin film (～4 ML) of VOx (x≈1) deposited on the (1 × 1)-TiO2 (110) (rutile) surface leads to a detailed determination of the structure and orientation of the overlayer and of its epitaxial relationship with the substrate. The comparison of XPD experimental data to theoretical simulations confirms the NaCl-like stacking of the overlayer which is suggested by the direct observation of the experimental 2π plots and reveals its (100) orientation. The [001] azimuth of the overlayer is aligned with the [112] direction on the substrate surface and the overlayer experiences an orthorhombic tensile strain (+ 7%) in order to match the substrate epitaxially, with a consequent 12-16% vertical interlayer spacing contraction. The atomic scale morphology of the (1 × 1)-TiO2 (110) surface induces a strong buckling in the overlayer along the [110] substrate direction [0.5±0.1 A?].
- Della Negra, Michela,Sambi, Mauro,Granozzi, Gaetano
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- Conductivity and stability of cobalt pyrovanadate
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Cobalt pyrovanadate was successfully synthesised by a solid state route and the conductivity in both oxidising and reducing environments was determined for the first time. Impedance measurements between 300 °C and 700 °C in air determined that Co2V2O7 is an intrinsic semiconductor with activation energy of 1.16(3) eV. The conductivity in air reached a maximum of 4 × 10-4 S cm-1 at 700 °C. Semiconducting behaviour was also observed in 5% H2/Ar, albeit with a much smaller activation energy of 0.04(4) eV. Between 300 °C and 700 °C the conductivity ranged from 2.45 S cm-1 to 2.68 S cm-1, which is approaching the magnitude required for SOFC anode materials. Thermogravimetric analysis found a significant weight loss upon reduction of the compound. X-ray diffraction analysis, coupled with data from previous research, suggested compound degradation into Co2-xV1+xO 4, CoO and VO. The redox instability and the low conductivity lead us to the conclusion that cobalt pyrovanadate is unsuitable for utilisation as an anode material for SOFCs although the conductivity is reasonable in a reducing atmosphere.
- Cowin, Peter I.,Lan, Rong,Petit, Christophe T.G.,Zhang, Lei,Tao, Shanwen
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- XPS study of vanadium surface oxidation by oxygen ion bombardment
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Oxidation of vanadium metal surfaces at room temperature by low-energy oxygen ion beams is investigated by X-ray photoelectron spectroscopy (XPS). It is observed that ion-beam irradiation of clean V results in formation of thin oxide layer containing vanadium in oxidation states corresponding to VO, V2O3, VO2 and V2O5 oxides. The composition of the products of ion-beam oxidation depends markedly on oxygen ion fluence. The results of angle-resolved XPS measurements are consistent with a structure of oxide film with the outermost part enriched in V2O5 and VO2 oxides and with V2O3 and VO oxides located in the inner region of the oxide layer.
- Alov,Kutsko,Spirovová,Bastl
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- Novel azomethine Pd (II)- and VO (II)-based metallo-pharmaceuticals as anticancer, antimicrobial, and antioxidant agents: Design, structural inspection, DFT investigation, and DNA interaction
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The new NO bidentate imine ligand, namely, (2-[(3-nitro-benzylidene)-amino]-benzoic acid) (NBA) imine ligand (L), and its Pd (II) and VO (II) complexes have been synthesized and characterized by utilizing different physiochemical methods including elemental analyses, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), molar conductance, and magnetic susceptibility measurements. The stability constant of these complexes has also been determined. In studies of these complexes, they were found to have [M(L)] composition where the ligand acts as a bidentate and coordinates with the various metal ions through azomethine and one oxygen atom. Moreover, the suggested geometrical structure of Pd (II) and VO (II) complexes is square planar and a distorted square pyramid, respectively. Density functional theory (DFT) calculations for the different metal complexes were studied and show a good agreement with the experiment data. The minimum inhibitory concentration method has been applied to evaluate the in vitro antimicrobial activity. Furthermore, the interaction of calf thymus DNA with the metal-imine chelates has been assessed, and Pd (II) complex showed the strongest interaction with DNA for a binding constant value of (9.72 × 104 kcal mol?1). The cytotoxic activity of the new metal chelates has been evaluated against three human cancer cell lines (hepatic carcinoma HepG2 cells, breast carcinoma cells MCF-7, and colon carcinoma cells HCT-116). It has found that NBAPd complex exhibited a significant decrease in the time and dose of the cell viability than did the reference drug vinblastine. The antioxidant activity of the tested compounds was determined and compared with that of vitamin C as a standard drug. It has been found that the metal complexes exhibit higher activity than the free ligand. The finding from this investigation revealed that the new compounds are considered to be prospective antibiotic and anticancer agents.
- Abu-Dief, Ahmed M.,Abdel-Rahman, Laila H.,Shehata, Mohamed R.,Abdel-Mawgoud, Azza A. Hassan
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- Reactions of group V metal atoms with water molecules. Matrix isolation FTIR and quantum chemical studies
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Laser-ablated group V metal atoms (V, Nb, Ta) were co-deposited with water molecules in excess argon. The V atoms reacted with water to form the inserted HVOH molecule spontaneously. The Nb atoms reacted with water to form the NbOH2 complex and
- Zhou,Dong,Zhang,Qin
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p. 135 - 141
(2007/10/03)
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- The effect of carbonyl complexation on highly exothermic vanadium oxidation reactions
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The effects of CO complexation on highly exothermic vanadium oxidation reactions is evaluated. We study the chemiluminescent (CL) reaction products formed when vanadium vapor entrained in Ar or CO is oxidized by O3 or NO2. The multiple collision V + Ar + O3 → VO*(C4Σ-, 4Φ, 2X) + Ar + O2 reactive encounter yields two previously unreported VO excited states, whereas the V + Ar + NO2 → VO* + Ar + NO reactive encounter populates states up to and including VO* C4Σ-. The multiple collision V + nCO + O3 reactive encounter would appear to form a VOCO excited state complex, emitting in the region 420-560 nm, via the formation and oxidation of V(CO)2 viz. V(CO)2 + O3 → VOCO* + CO + O2 and a relaxed VO excited state emitter via V + nCO + O3 → VO* + nCO + O2 where the VO excited state excitation is mediated by V-CO complexation. In complement, the much less exothermic V-NO2 encounter displays an emission which, in concert with previous studies of CO complexation, suggests the formation of a VO(CO)2 excited state complex viz. V(CO)2 + NO2 → VO(CO)2/* + NO. The experiments characterizing CL are complemented by comparative laser-induced fluorescence studies of the VO X4Σ-CO and Ar interactions and their influence on the VO C4Σ-X4Σ- laser-induced excitation spectrum. These studies, in conjunction with further attempts to excite LIF in the 420-560 nm region, suggest that the observed complex emissions result primarily from VO excited state interactions. Complementary time-of-flight mass spectroscopy of vanadium and vanadium-oxide-carbonyl complex formation demonstrates the formation of V(CO), V(CO)2, V2(CO), and VOCO, the latter three of which demonstrate clear metastable-ion dissociation peaks for the processes VOCO+ → V+ + CO2, V(CO)2/+ → V+ + 2CO, and V2(CO)+ → V2/+ + CO, suggesting that these vanadium complexes when formed in a reaction-based environment may be photodissociated with light in the visible and ultraviolet regions. (C) 2000 Elsevier Science B.V.
- McQuaid,Gole, James L.
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p. 367 - 382
(2008/10/08)
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- Vanadium compositions
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There are provided vanadium compositions for use in the treatment of hypertension, obesity and diabetes, in particular improved oral compositions comprising oxovanadium (IV) chelates of monoprotic, bidentate oxygen, oxygen and oxygen, nitrogen coordinating ligands especially kojic acid, maltol and ethyl maltol.
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- Pulsed CO2 laser induced chemistry of vanadium oxytrichloride (VOCl3)
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Pulsed CO2 laser multiple photon excitation of VOCl3, under collisional and collision-free conditions, resulted in dissociation via its ground electronic state and in a visible fluorescence.The photodissociative pathways leading to product formation were found to be both pressure and laser fiuence dependent.Low pressure and laser fluence led to the formation of VOCl2 while high pressure and laser fluence flavored VO.The prompt fluorescence was also studied as a function of pressure and laser fluence, and was shown to arise from a spontaneous one-photon radiative decay from an electronic state belonging to the VOCl2 fragment.The reaction mechanisms leading to product formation as well as models for populating a fragment's electronic state are proposed and discussed in conjunction with present multiphoton excitation and dissociation theory.In addition, CO2 laser induced dielectric breakdown of VOCl3, in the neat and with scavenger gases, resulted in the production of various vanadium oxides.The products are finely divided particles of very large surface area and high purity.
- Sausa, R. C.,Ronn, A. M.
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p. 1716 - 1724
(2007/10/02)
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