Vanadium Oxide Compounds Research Articles

Innovative 2D dioxonium vanadium oxide: enhancing stability in aqueous zinc-ion battery cathodes.

Vanadium oxide-based compounds have attracted significant interest as battery materials, especially in aqueous Zn-ion batteries, due to favorable properties and compatibility in Zn-ion systems. In a simple hydrothermal method with moderate conditions, a novel vanadium oxide compound has been synthesized using ammonium metavanadate with oxalic acid as a reducing agent. Various characterization techniques confirmed the formation of layered V3O8(H3O)2 nanoplatelets with a tetragonal crystal structure. The as-prepared cathode material was tested in coin cells against a Zn metal anode in two aqueous electrolytes of the same concentration: ZnSO4·7H2O and Zn(CF3SO3)2. Electrochemical results showed high reversibility of Zn insertion/de-insertion and impressive cycling stability with aqueous Zn(CF3SO3)2 electrolyte. Notably, the cathode material delivered a specific capacity of 150 mA h g-1 at 100 mA g-1 and a relatively constant coulombic efficiency near 100%, indicating impressive stability during cycling and reversibility of charge/discharge electrochemical reactions. Post-mortem characterization exposed a significant structural change in the as-prepared cathode material from nanoplatelets to nanoflakes after full discharge, which reverted to nanoplatelets after charging, reflecting the high level of reversibility of the material. DFT calculations revealed a structural change in the material after cycling, providing mechanistic insights in Zn2+-ion storage.

Hollow-cathode plasma deposited vanadium oxide films: Metal precursor influence on growth and material properties

Due to its different polymorphs, including vanadium pentoxide (V2O5) and vanadium dioxide (VO2), the vanadium oxide (VOX) compound is an immensely interesting material with many important applications. While atomic layer deposition (ALD) is among the possible VOX film synthesis methods, literature reports have majorly utilized thermal-ALD, which reveals as-grown amorphous VOX films. Further post-deposition annealing process is needed to crystallize these films. High-temperature crystallization indeed limits the use of low-temperature compatible materials, processes, and substrates. In this work, we report on the low-temperature crystalline VOX film growth in a hollow-cathode plasma-enhanced atomic layer deposition reactor using two different vanadium precursors, tetrakis(ethylmethylamino)vanadium and vanadium(V) oxytriisopropoxide. Oxygen plasmas were used as co-reactants at a substrate temperature of 150 °C. Along with the purpose of investing in the impact of metal precursors on VOX film growth, we also studied Ar-plasma in situ and thermal ex situ annealing to investigate possible structural enhancement and phase transformation. In situ Ar-plasma annealing was performed with 20 s, 20 SCCM Ar-plasma, while post-deposition ex situ annealing was carried out at 500 °C and 0.5 mTorr O2 pressure. In situ ellipsometry was performed to record instant film thickness variation and several ex situ characterizations were performed to extract the optical, structural, and electrical properties of the films. The outcomes of the study confirm that both metal precursors result in as-grown crystalline V2O5 films at 150 °C. On the other hand, post-deposition annealing converted the as-grown crystalline V2O5 film to VO2 film. Finally, we have also successfully confirmed the metal-to-insulator transition property of the annealed VO2 films via temperature-dependent structural and electrical measurements.

Low-temperature synthesis of crystalline vanadium oxide films using oxygen plasmas

Vanadium oxide (VOx) compounds feature various polymorphs, including V2O5 and VO2, with attractive temperature-tunable optical and electrical properties. However, to achieve the desired material property, high-temperature post-deposition annealing of as-grown VOx films is mostly needed, limiting its use for low-temperature compatible substrates and processes. Herein, we report on the low-temperature hollow-cathode plasma-enhanced atomic layer deposition (ALD) of crystalline vanadium oxide thin films using tetrakis(ethylmethylamido)vanadium and oxygen plasma as a precursor and coreactant, respectively. To extract the impact of the type of plasma source, VOx samples were also synthesized in an inductively coupled plasma-enhanced ALD reactor. Moreover, we have incorporated in situ Ar-plasma and ex situ thermal annealing to investigate the tunability of VOx structural properties. Our findings confirm that both plasma-ALD techniques were able to synthesize as-grown polycrystalline V2O5 films at 150 °C. Postdeposition thermal annealing converted the as-grown V2O5 films into different crystalline VOx states: V2O3, V4O9, and VO2. The last one, VO2 is particularly interesting as a phase-change material, and the metal-insulator transition around 70 °C has been confirmed using temperature-dependent x-ray diffraction and resistivity measurements.

Features of the development of the mucosal immune system of the upper respiratory tract in ferrous metallurgy workers

Introduction. The exposure to industrial aerosols triggers the response of the adaptive and innate mucosal immunity in the upper airways. Objective: To analyze the impact of work-related risk factors on the development of local mucosal immunity in workers engaged in extraction of vanadium-bearing iron ore, and cast iron and steel production. Materials and methods. We examined one thousand five hundred forty seven male workers of two mining and metallurgical industries. The first cohort included 788 vanadium-bearing iron ore miners and the second cohort comprised 719 cast iron and steel production workers, both standardized by age and years of employment. Occupational risk factors identified in both cohorts included the exposure to fibrous aerosols and aliphatic hydrocarbons, and poor microclimate (high or low air temperature) at workplaces. The workers of the second cohort were also exposed to manganese compounds, vanadium (V) oxide, chromium, nickel, and iron compounds. The control group consisted of 40 engineering and technical personnel. Results. A significant increase in secretory immunoglobulin A (sIgA) was detected in the miners exposed to aliphatic hydrocarbons and low air temperature. In the ferrous metallurgy workers, the exposure to low air temperature, crystalline silicon, and aliphatic hydrocarbons caused a significant decrease in the level of sIgA while the exposure to manganese oxides induced a decrease in the bactericidal function of neutrophils. Limitations. The main limitations of the research were related to the selected criterion of inclusion in the merged occupational cohorts with account for exposure to adverse microclimate parameters, silicon-containing aerosols, aliphatic hydrocarbons, and manganese compounds. In view of the multiplicity of occupational risk factors in the industry, it is important to conduct additional studies of a larger sample for qualitative and quantitative presentation of convincing evidence of health effects of other factors of the work environment. Conclusions: We established a multidirectional response of the mucosal immunity to production factors in the examined workers. A combined exposure to chemical and physical occupational factors has a stronger health effect than a single one. Differences in the level of sIgA in workers exposed to different occupational hazards prove the advisability of an in-depth immunological examination combined with an assessment of the functional status as indicators of occupational adaptation.

Root cause failure investigation of a boiler waterwall tube employed in a 325 MW thermal power plant: Caustic corrosion phenomenon and its effects

This paper focuses on failure analysis of a boiler waterwall tube, ASTM A213 Grade T2 steel, used in a 325 MW fuel oil-fired thermal power plant. The influence of fire/waterside factors on the failure was identified through multiple characterization techniques. Preliminary macroscopic observations revealed uniform heavy deposition and repair welding indications on the fireside surface of the failed tube. Moreover, a longitudinally hemielliptical inner groove along with excessive weld metal penetration and discrete cavities were observed along the crown of the tube, leading to local wall thinning down to around 50% of its nominal thickness. No noticeable hardness and microstructural variations such as pearlite colonies decomposition caused by long term overheating and formation of decarburized layer were detected. According to the results of micro-zone analyses, considerable quantity of sodium vanadium oxide compounds accumulated throughout the fireside surface of the tube was due to poor fuel quality used. The authors postulated that evaporation at the waterline of the approximately filled tube resulted in water/steam stratification and localized caustic constituents concentration within the inner groove like NaOH and alkaline producing salts containing Na, Mg, Ca and P elements entered into the water/steam cycle through condenser copper-based tube leakages. This trend solubilized protective magnetite film locally and, consequently, triggered caustic corrosion of the bare steel.

K,Na–Vanadium Oxide Compounds for Lithium-Ion Batteries: Synthesis and Electrochemical Performance in a Redox Reaction with Lithium

K,Na–Vanadium Oxide Compounds for Lithium-Ion Batteries: Synthesis and Electrochemical Performance in a Redox Reaction with Lithium

Watching a metal filament grow

Oxide Electronics Resistive switching is a process in which the electrical resistance of a sample changes abruptly in response to a voltage pulse, often by orders of magnitude. This process is at the heart of many neuromorphic computing approaches but visualizing it in both space and time is tricky. del Valle et al. monitored the resistive switching in three different vanadium oxide compounds by measuring time- and space-resolved optical reflectivity (see the Perspective by Hilgenkamp and Gao). A characteristic conducting filament was quickly nucleated on the inhomogeneities in the sample and then propagated due to Joule heating. Science , abd9088, this issue p. [907][1]; see also abh2231, p. [854][2] [1]: /lookup/doi/10.1126/science.abd9088 [2]: /lookup/doi/10.1126/science.abh2231

Spatiotemporal characterization of the field-induced insulator-to-metal transition.

Many correlated systems feature an insulator-to-metal transition that can be triggered by an electric field. Although it is known that metallization takes place through filament formation, the details of how this process initiates and evolves remain elusive. We use in-operando optical reflectivity to capture the growth dynamics of the metallic phase with space and time resolution. We demonstrate that filament formation is triggered by nucleation at hotspots, with a subsequent expansion over several decades in time. By comparing three case studies (VO2, V3O5, and V2O3), we identify the resistivity change across the transition as the crucial parameter governing this process. Our results provide a spatiotemporal characterization of volatile resistive switching in Mott insulators, which is important for emerging technologies, such as optoelectronics and neuromorphic computing.

Oxygen vacancy-rich, binder-free copper pyrovanadate for zinc ion storage

The semiconductor nature of the vanadium oxide compound determines its low conductivity, which is not conducive to the transfer of electrons and affects the performance of an aqueous zinc ion battery (AZIB). Therefore, herein, an efficient strategy was proposed to improve the electrochemical performance of stainless steel (SS) supported highly crosslinked foam-like Cu3V2O7(OH)2⋅2H2O (CVO-SS-2) by creating oxygen vacancies. The effect of oxygen vacancy on the electrochemical behavior of Cu3V2O7(OH)2⋅2H2O grown on SS (Od-CVO-SS-2) was investigated. The experimental results show that the introduction of oxygen vacancies into the lattice significantly produces low oxidation state Cu and V species, thereby improving the conductivity and the interfacial activity of the Od-CVO-SS-2, promoting the reaction kinetics and enabling it to show more excellent electrochemical performance. Density functional theory (DFT) calculations confirmed that oxygen vacancy can effectively reduce the adsorption energy of Zn2+ ions. This means that the adsorption/desorption process of Zn2+ ions on Od-CVO-SS-2 is more reversible than that on pure CVO-SS-2. The Od-CVO-SS-2 electrode shows a high specific capacity of 269.2 mAh g−1 at a current density of 0.2 A g−1 after 100 cycles and excellent cyclic stability (88.2% retention after 3000 cycles 4 A g−1), higher than that of CVO-SS-2 (171.1 mAh g−1 at 0.2 A g−1). Besides, the energy storage mechanism of Zn2+ was studied by different ex-situ characterization methods. Vacancy design is an effective way to obtain electrode materials with excellent comprehensive properties.

Coin cell fabricated symmetric supercapacitor device of two-steps synthesized V2O5 Nanorods

A highly efficient and effective nanostructured vanadium oxide (V2O5) compound was synthesized for supercapacitor applications. A facile two-step method comprising preheating activation, followed by a hydrothermal route was utilized to synthesize V2O5 nanorods. As an electrode, the V2O5 nanorods exhibited a high specific capacitance of 347 F g−1 at 1 A g−1. The remarkable cyclic stability of the V2O5 compound indicates adequate potential for the fabrication of a symmetric supercapacitor device. A coin-cell symmetric supercapacitor device assembled using the V2O5 electrode exhibited excellent electrochemical performance, including a specific capacitance of 172 F g−1, an energy density of 23.9 W h kg−1, a power density of 937 W kg−1, and capacitance retention of 94.3% after 10,000 cycles.

Preparation of Hybrid Composite Materials on the Basis of Vanadium and Molybdenum Oxide Compounds

Hybrid composite oxide material is obtained by transient electrolysis method on the surface of carbon fiber substrate having the ability to reverse electrochemical intercalation of lithium. It is established that electrochemical characteristics of the hybrid composite oxide material depend on the concentration of sodium metavanadate in the solution of cathodic degreasing electrolyte during the preparation of carbon substrate surface.

Temperature dependence of electrical resistivity in oxidized vanadium films grown by the GLAD technique

Abstract Vanadium and vanadium oxide thin films are deposited by DC magnetron sputtering. A first series of pure vanadium films are prepared by glancing angle deposition (GLAD). The incident angle α of the particle flux is systematically changed from 0 to 85°. For the second series, the angle α is kept at 85° and oxygen gas is injected during the growth by means of the reactive gas pulsing process (RGPP). A constant pulsing period P = 16 s is used whereas the oxygen injection time t ON is varied from 0 to 6 s. After depositing, films are annealed in air following 11 incremental cycles from room temperature up to 550 °C. For both series, the DC electrical resistivity is systematically measured during the annealing treatment. Vanadium films sputter deposited by GLAD become sensitive to the temperature for incident angles α higher than 60°. The most significant annealing effect is observed for films prepared with α = 85° with a strong increase of resistivity from 2.6 × 10 − 5 to 4.9 × 10 − 3 Ωm. It is mainly assigned to the oxidation of GLAD vanadium films, which is favoured by the high porous morphology produced for the highest incident angles. The resistivity vs. temperature evolution is also measured and related to the occurrence of the VO 2 phase. By combining GLAD and RGPP processes, the reversible variation of resistivity associated to the VO 2 phase is even more pronounced. Oxygen pulsing during deposition and the voided structure produced for the highest incident angles enhance the oxidation of vanadium through the films thickness. The porous architecture by GLAD and the oxygen injection by RGPP have to be carefully controlled and optimized for the growth of vanadium oxide compounds, especially to favour the formation of the VO 2 phase.

Effect of buffer layer on thermochromic performances of VO2 films fabricated by magnetron sputtering

As a well-developed industrial fabricating method, magnetron sputtering technique has its distinct advantages for the large-scale production. In order to investigate the effect of buffer layer on the formation and thermochromic performances of VO2 films, using RF magnetron sputtering method, we fabricated three kinds of buffer layers SiO2, TiO2 and SnO2 on soda lime float-glass. Then according to the reactive DC magnetron sputtering method, VO2 films were deposited. Due to the restriction of heat treatment temperature when using soda lime float-glass as substrates, dense rutile phase TiO2 cannot be formed, leading to the formation of vanadium oxide compounds containing Na ions. When using SnO2 as buffer layer, we found that relatively high pure VO2 can be deposited more easily. In addition, compared with the effect of SiO2 buffer layer, we observed an enhanced visible transparency, a decreased infrared emissivity, which should be mainly originated from the modified morphology and/or the hetero-structured VO2/SnO2 interface.

Vanadium Oxide Compounds: Structure, Properties, and Growth from the Gas Phase

The structure‐driven properties of vanadium oxide have inspired enormous developments in the last decades, especially as a smart material for energy, sensors, and optoelectronics. The large variety of stable and metastable structures of vanadium oxide is discussed, based on the calculated formation energies and a broad overview of their structure‐related properties. The established chemical deposition processes from the gas phase are reviewed with a particular emphasis on the implemented precursors and the obtained vanadium oxide phases. Although a significant fraction of relevant vanadium oxide compounds is achieved by these methods, there are still rewarding challenges related to their controlled elaboration and the investigation of their responsive properties.

Effects of Reductant on Physical Properties and Formation of Vanadium Oxide Compounds Prepared by Hydrothermal Route

Vanadium oxide nanostructures were successfully synthesized by hydrothermal process using V2O5 as a starting source material. The process was conducted at 120°C for 48 h using different reductants including n-butanol and acetylacetone. The essential physical properties of as-synthesized products were characterized by XRD, FT-IR spectroscopy, SEM and TEM. The XRD and Raman results revealed that the crystalline structure and phase of the samples are highly dependent on the reductant types. The SEM images enclose that as-prepared samples possess different morphologies depending on different reactant. The phase transformation from V2O5 to VO2 can be also carried out by this process with assistance of these reactants.

Exotic Magnetism of NovelS= 1 Kagome Lattice Antiferromagnet KV3Ge2O9

Single crystals of the novel vanadium oxide compound KV 3 Ge 2 O 9 have been synthesized. This compound has a hexagonal unit cell with the space group P 6 3 / m m c . Its lattice constants are a = 5.8624(4) A and c = 13.7094(7) A. KV 3 Ge 2 O 9 contains layers of edge-shared VO 6 octahedra, where V 3+ ions with an S = 1 spin form kagome lattice layers separated by double layers of GeO 4 tetrahedra. The magnetic susceptibility shows a broad maximum at approximately 70 K, suggesting that magnetic transition is suppressed in spite of the presence of strong antiferromagnetic interactions. Below approximately 20 K, the susceptibility under a magnetic field perpendicular to the kagome plane steeply drops toward zero, while the in-plane susceptibility diverges with reduction in temperature.

Direct hydrothermal synthesis of monoclinic VO2(M) single-domain nanorods on large scale displaying magnetocaloric effect

Monoclinic VO2(M) is a prototype material for interpreting correlation effects in solids with fully reversible phase transition between VO2(M) and VO2(R). Although VO2(M) is the thermodynamically most stable phase, few available solution strategies for VO2(M) have been realized since Morin's discovery in the 1950s. Here, we report a controlled oxidation reaction to realize the direct solution-based synthesis of monoclinic VO2(M). The established strategy also achieves highly uniform nanorods with single-domain structure, which is particularly fascinating due to the long-standing limited and sole method for one-dimensional (1D) nanostructures of monoclinic VO2(M). The orientation change of the electron clouds leads to the magnetization change on passing through the phase transition from VO2(M) to VO2(R), making VO2(M) the first case of a vanadium oxide compound to show magnetocaloric effect (MCE). And the MCE performance advantage of solution synthesis sample greatly benefits from the highly uniform nanorods having a single-domain structure, which realizes the rapid magnetization change on passing the phase transition and then leads to higher magnetic entropy change ΔS value for magnetocaloric effect (MCE). The clear physical picture of the first-order phase transition process comes from a series of time-resolved in situ techniques, including the first established in situXAFS technique for vanadium K-edge.

Investigation of the structure and phase transitions of the polymeric inorganic–organic hybrids: [M(Im)4V2O6]∞; M = Mn, Co, Ni, Im = imidazole

The polymeric isomorphous hybrid inorganic-organic vanadium oxide compounds [M(Im)(4)V(2)O(6)](∞), M = Mn, Co, Ni, Im = imidazole, were investigated at various temperatures between 100 and 295 K by single-crystal X-ray diffraction. The crystals all contain two-dimensional polymeric sheets packed perpendicular to c* and are 1:1 disordered in the space group P4(2)/n (Z = 8) at 295 K. The disordered phase is reversibly transformed to an I4(1)/a ordered phase (Z = 32) below 281 K for the Mn compound and below 175 K for the Co compound. Within a localized region of the I4(1)/a phase eight imidazoles are in close proximity and seven of these are hydrogen bonded to framework O atoms. The hydrogen-bond connectivity of six of these ligands is unchanged by the phase transition that allows an inversion of the local geometry using an inversion operator that is a symmetry element of P4(2)/n, but not I4(1)/a. The Mn structure has a well defined phase transition but the Co structure shows a large hysteresis and it was necessary to include stacking faults in the modelling of the Co structure at low temperatures. The Ni structure was shown to be partially twinned, but ordered in the space group P2/n (Z = 8) at 100 K, with two different localized regions each containing four pairs of inversion-related imidazoles, hydrogen bonding to framework O atoms involving eight imidazoles in one region and six imidazoles in the other. Models for the phase transition mechanisms are considered.

Frustrated Magnetism in Vanadium Oxides

The effect of frustration in various localized and itinerant vanadium oxide compounds is discussed within next nearest neighbors Heisenberg and spin fluctuation models, respectively. In the localized moment case the S = 1/2 J1−J2-model on a square lattice exhibits a rich phase diagram with magnetic as well as exotic hidden order phases due to the interplay of frustration and quantum fluctuations. Their signatures in the high field magnetization and in magnetocaloric quantities are surveyed. The possible quantum phase transitions are discussed and applied to layered vanadium oxides of the type AA′VO(PO4)2 where A, A′ = Pb, Zn, Sr, Ba, Cd. In itinerant electron systems magnetic frustration may emerge as a result of electron correlations on a geometrically frustrated lattice. This mechanism causes enhanced spin fluctuations in a large region of momentum space and therefore can lead to a heavy fermion state at low temperatures as in the 3d spinel compound LiV2O4. The evidence from neutron scattering and NMR experiments is discussed within self-consistent renormalization theory based on local density approximation band structure calculations.

ChemInform Abstract: Vanadium Oxide Compounds with Quantum Monte Carlo

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