Increasing Vanadium Content Research Articles

Strengthening mechanisms in vanadium-microalloyed medium-Mn steels

In this work, the impact of adding vanadium, ranging from 0 to 2 wt%, on the microstructure and mechanical properties of as-cast medium manganese steel was explored. A dual phase microstructure consisting of martensite and retained austenite was observed in the 0 V, 0.05 V and 0.8 V conditions. The 2 V condition contained retained austenite, lath martensite, and δ-ferrite bands. The retained austenite fraction and prior austenite grain size initially increased at lean vanadium concentrations but significantly dropped at the highest vanadium concentration. The element distribution in the constituent phases was investigated in detail. Mn, C and Si partitioning to austenite was observed in the 0 V, 0.05 V and 0.8 V conditions. V and C segregation to the grain boundaries and significant grain refinement were evident in the 2 V condition. The findings also revealed that increasing the vanadium content led to an increase in the hardness of the steel. This assessment was validated by tensile testing, which showed an improvement in yield and tensile strength of the steel with increasing vanadium content, and were supported by reconstruction of the parent austenite grains employing martensitic structures. Finally, the influence of different strengthening mechanisms on the yield strength of as-cast, microalloyed medium-manganese steels was also discussed in terms of simulated stacking fault energy, as well as the quantitative contributions from solid solution, grain boundary, and precipitation strengthening mechanisms.

A detailed kinetic model for the methanol oxidative dehydrogenation on vanadia-based catalysts: Aggregation state role and active site requirements

A kinetic model was derived for the methanol oxidative dehydrogenation to formaldehyde, methyl formate and dimethoxymethane on sub-monolayer and multilayer V2O5/TiO2 catalysts. Considering a hemiacetal intermediate, the model combines Langmuir-Hinshelwood/Eley-Rideal/Mars-van Krevelen mechanisms, accounting for lattice oxygen redox sites and Brønsted acid sites. The fitted model depends on 4 thermodynamically consistent parameters, adequately simulating yield trends with temperature, residence time, and partial pressure of methanol, oxygen and added water. Oxidation steps follow a Mars-van Krevelen redox cycle, while the dimethoxymethane formation is reversible, as the water addition favored the hemiacetal intermediate. The catalyst with higher vanadia surface density was intrinsically more active (lower activation energy of the rate limiting step), attributed to its higher reducibility, while showing weaker methanol adsorption (lower enthalpy of chemisorption). The increase in reducibility correlates with the transition from monomers to polymers to crystalline vanadia when vanadium content increases, as observed by XRD, Raman spectroscopy and DRS-UV–vis.

Revealing the Removal Mechanism of Vanadium Addition on Nitrogen Pores in 30Cr15Mo1N High‐Nitrogen Steel Ingot

The removal mechanism of vanadium addition on nitrogen pores in 30Cr15Mo1N ingot is systematically investigated through statistical analysis and theoretical calculation. The nitrogen solubility is obtained by the thermodynamic model, and the nitrogen content is obtained by combining the ProCAST software and the C–K model. Then, according to the formula of critical nucleation radius and growth rate of nitrogen bubbles, the variation of critical nucleation radius and growth rate of nitrogen bubbles with different vanadium contents is calculated. As the vanadium content increases, the number and mean area of nitrogen pores decrease. In comparison to the 0 V ingot, the number of nitrogen pores decreases in the 0.2 V ingot, but there is an increase in the number of large‐sized nitrogen pores (>3000 μm in diameter). When the vanadium content increases to 0.4, the nitrogen pores are completely removed. The results demonstrate that increasing vanadium content can remove nitrogen pores. Since the solidification mode remains unchanged with increasing vanadium content, increasing the vanadium content cannot remove nitrogen pores by changing the solidification mode of the 30Cr15Mo1N ingots. Therefore, increasing the vanadium content removes the nitrogen pores mainly by inhibiting the nucleation of nitrogen bubbles and promoting nitrogen bubble overflow in 30Cr15Mo1N ingots.

Novel investigation by TB-mBJ potential of magneto-electronic properties and magnetic exchange coupling in vanadium (V)-doped PbTiO3 perovskite oxide

ABSTRACT In this paper, we investigated the structural and magneto-electronic properties, and exchange coupling in new vanadium (V)-doped PbTiO3 perovskite oxide such as PbTi1−xVxO3 compounds with compositions of x = 0, 0.25, 0.5, 0.75, and 1. The calculations of these properties are based on density functional theory using the generalized gradient approximation of Wu-Cohen (GGA-WC) and the Tran-Blaha-modified Becke–Johnson potential (TB-mBJ). Our calculations with GGA-WC revealed that the lattice constant for PbTiO3 is in good concordance with other theoretical and experimental results, while for PbTi1−xVxO3 at x = 0.25, 0.5, 0.75, and 1, the lattice constant decreases with increasing vanadium concentration owing to the difference in sizes of Ti and V ionic radii. The improved electronic structures obtained by employing the TB-mBJ potential, demonstrated that the half-metallic ferromagnetic and half-metallic gaps are present in PbTi1−xVxO3 materials at x = 0.25, 0.5, 0.75, and 1, which makes them promising candidate materials for spintronics applications.

Molecular Dynamics Simulation of the Interaction between Dislocations and Iron–Vanadium Precipitates in Alpha Iron: Effect of Chemical Composition

In this study, molecular dynamics simulations were employed to study the interaction between dislocations with Fe-V precipitate with different vanadium concentrations. Increasing the vanadium concentration in the precipitate results in a strong interaction between the dislocations and the precipitate, and the dislocation line bows out more as a result of increasing the energy of the dislocation line, and the critical stress needed for depinning the dislocations increases. However, at a low vanadium concentration (1:3 atomic ratio) the dislocations cut through the precipitate without changing the speed. An increasing vanadium concentration not only affects the dislocation shape and movement speed, but also affects the configuration of the junction between the a/2[111] and a/2[100] dislocations, and the void formation after the cutting process. The formation of strong junctions and a high number of voids locks the a/2[111] dislocation motion, and increases the strength of the alloy. The results of the radial distribution function before and after the cutting process show that the structure of the precipitate changes from crystalline to amorphous, and the degree of amorphization decreases with an increasing vanadium concentration.

Investigation of the structural, electrical and magnetic properties of vanadium substituted Mn–Zn ferrites

This work revealed the role of altering vanadium (V) content in Mn–Zn ferrites. We used the traditional solid-state reaction method to prepare the {mathrm{Mn}}_{0.5}{mathrm{Zn}}_{0.5}{mathrm{V}}_{mathrm{x}}{mathrm{Fe}}_{2-mathrm{x}}{mathrm{O}}_{4} (x = 0.0, 0.05, 0.10, 0.15, 0.20) ferrites. Powder X-ray diffraction was used to analyze the samples’ crystal structures, revealing the prepared sample’s spinal cubic crystal structure. With increasing Vanadium concentration, the lattice constant drops proportionately. We used Debye–Scherrer (D–S), Williamson–Hall (W–H) Plot, Halder–Wagner (H–W) Langford, and Size Strain Plot (SSP) methods to compare different structural properties. We also used the impedance analyzer to investigate the samples’ dielectric characteristics and AC conductivity at room temperature over a frequency range of 1 kHz–100 MHz. The magnetic properties, i.e., Saturation magnetization (Ms), Coercive field (Hc), and Remanent magnetization (Mr), were estimated from the ferromagnetic hysteresis behavior of the samples measured using a vibrating sample magnetometer (VSM). The saturation magnetization was observed to decrease with an increase in V content. The Mr and HC vary non-linearly with V contents. The prepared samples’ initial permeability was tested, and a reasonably constant complex permeability (µ') was recorded over a wide frequency range (~ 1000 Hz).

Synthesis, characterizations and magnetic properties of nanoscale CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) materials synthesized via sol-gel autocombustion route

Nanostructured materials of CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) have been synthesized by sol-gel autocombustion method. Phase purity and nanocrystalline nature of the materials were examined by powder XRD measurements. Morphology and microstructure of the materials were ascertained by FESEM technique. The estimated crystallite sizes (d) decrease from 30 nm to 8 nm, as a result of progressive increase in V content, x, in CoVxFe2-xO4 materials. The values of the observed lattice parameters (a) decrease continuously as a function of increasing V content, x, i.e. from 8.349(5) Å to 8.284(5) Å for the values of x = 0.0 and x = 0.9, respectively. Alterations of M − O bond lengths in CoVxFe2-xO4 materials in FTIR studies indicate the incorporation of vanadium in cobalt ferrite. The values of the saturation magnetizations (Ms) and coercivities (Hc) of CoVxFe2-xO4 materials are found to be in the range of 77.58 emu/g – 37.76 emu/g and 1264 Oe – 991 Oe for various values of x from x = 0.0 to x = 0.9, respectively. The observed trends in magnetic parameters of CoVxFe2-xO4 materials have been interpreted on basis of increasing vanadium content in the materials, cation distributions, size and surface effects.

Regulating phase ratio of β/α and static recrystallization of Ti-5Al-5Mo-5Cr-3Nb-2Zr with high plasticity alloyed by vanadium

To research the recrystallization mechanism without deformation of the α phase and control the phase ratio of β/α, Ti-5Al-5Mo-5Cr-3Nb-2Zr alloys with different vanadium contents were melted. The results indicate that with increasing vanadium content, the content and aspect ratio of the primary α (αp) and secondary α (αs) phases decrease, and the ratio of the β phase increases from 7% to 88%. The degree of recrystallization of αp and grain boundary α (αGB) phases increases, and their morphology changes from lath to equiaxed. The mechanism of static recrystallization is that the enrichment of V aggravates the local lattice strain and leads to the migration of the α phase interface. The V element aggravates the atomic size mismatch and the local lattice strain and reduces the β transition temperature of the enrichment region. The strength in the Ti-0 V alloy is the highest at ∼1056 MPa and then decreases. The Ti-2 V alloy had the highest toughness of ∼68.4 MPa·m1/2. The elongation of the Ti-6 V alloy is the highest at ∼16.1% due to the increase of β phase content and α phase recrystallization, which is ∼1.8 and ∼ 1.7 times that of the Ti-0 V and Ti-8 V alloys, respectively. The equiaxed αp phase and αs phase lead to shortening of the crack deflection path, and crack propagation is easier due to the increase of β phase content, which causes the crack propagation path to change from tortuous to straight.

Isovalent substitution of vanadium in LiFePO4: Evolution of monoclinic α-Li3Fe2(PO4)3 phase

We report the synthesis and characterization of isovalent substitution of vanadium at phosphorus site in orthorhombic lithium iron phosphate (LiFePO4) nanoparticles by non-aqueous sol–gel method. Detailed analysis of X-ray diffraction patterns reveals the evolution of monoclinic α-Li3Fe2(PO4)3 phase and its formation is favored for the vanadium content higher than 20%. A continuous increase in unit cell volume of LiFePO4 is observed with increase in vanadium content from x = 0.05 to 0.20, followed by rapid decrease above x = 0.20, due to the creation of a greater number of Li-ion vacancies. FTIR studies demonstrate that the wavenumbers of various absorption maxima and the covalency strength parameter do not show a variation with x, thus confirm the substitution of vanadium in the form of VO4. Our results through Mössbauer and electron paramagnetic resonance spectroscopy unambiguously demonstrate the enhancement in the formation of α-Li3Fe2(PO4)3 phase for vanadium content higher than 20%.

Effect of vanadium alloying on microstructure and wear behavior of two-body abrasive particles of Fe–5.5 wt% B surfacing alloy

The effects of vanadium addition on the microstructure and two-body abrasive wear behavior of an Fe–5.5 wt.% B surfacing alloy prepared by the plasma arc welding technique were investigated. The results show that the Fe–5.5 wt.% B surfacing alloys with different contents of vanadium are mainly composed of the primary Fe 2 B phase, Fe 2 B+Fe eutectic structure, and a vanadium boride (VB) precipitate. With increasing vanadium content in the Fe–5.5 wt.% B surfacing alloys, the number of microcracks in the primary Fe 2 B phase decreases, and the microcracks finally disappear, while the volume fraction of VB increases concurrently. The primary Fe 2 B phase can be remarkably refined, and the growth orientation changes from preferential to disordered staggered growth. The hardness of the surfacing alloy shows a trend of initial increase and subsequent decrease. Meanwhile, the wear resistance of the two bodies shows a continuous increasing trend, and the change trend is the same under contact loads of 24 N and 48 N. Alloying element V can effectively refine the primary Fe 2 B, promote the precipitation of VB, and form a microstructure reinforced by fine interlaced rod-shaped Fe 2 B and spherical VB, which effectively improves the crack resistance and wear resistance of the surfacing alloy.

Variation in Gemological Characteristics in Tsavorites with Different Tones from East Africa

In this paper, the influencing factors of the color and the gemological changes of tsavorites with different tones from East Africa were studied. The gemological characteristics of 35 different green tones in tsavorites were collected based on the results of color measurement, X-ray fluorescence, ultraviolet–visible, infrared and Raman spectroscopy. V and Cr are responsible for the samples’ color: with the increase of vanadium content, lightness L* and chroma C* decreased while hue h° increased, and the hue tends to blueish green. The color of tsavorite is related significantly to the absorption bands at about 430 nm and 605 nm through the UV-VIS spectrum. Under long-wave ultraviolet light, the samples show inert or red fluorescence. The G, H, and I peaks of the infrared spectrum are shifted towards the long-wave direction with the reduction of the V content. The peaks at 275 nm, 412 nm and 545 nm on the Raman spectrum tend to move towards the direction of decreasing wavelength with the increase of V content.

Effect of Vanadium on the Microstructure, Transformation Temperatures, and Corrosion Behavior of NiTi Shape Memory Alloys

Abstract Ni50Ti50-xVx (x = 0, 1, 2, 3 at%) shape memory alloys were prepared by vacuum induction melting. They were homogenized and then hot rolled. Carbon hydrogen nitrogen oxygen sulfur (CHNOS) and X-ray diffraction (XRD) analyses were carried out on the alloys to find out the oxygen and carbon contents and the phases present in the alloys. Transformation temperatures determined by differential scanning calorimetry indicate that the addition of vanadium reduces the transformation temperatures. Corrosion studies were carried out in Hanks’ solution, while potentiodynamic polarization tests were done to calculate the rate of corrosion of the alloys. Two significant parameters were analyzed from the Tafel graph, namely, corrosion rate and corrosion potential. A comparison of these properties of the alloys was also made with commercially pure titanium and binary NiTi alloys. Among the NiTiV alloys, Ni50Ti47V3 (at%) alloy was found to undergo the least rate of corrosion. With the increasing vanadium content, the rate of corrosion was found to decrease. Scanning electron microscopy (SEM) analysis of the corroded surface shows that pitting was the main mechanism of corrosion in these alloys. Results show that the addition of V to NiTi has a positive effect on the corrosion properties of the alloys. Elaborate results are discussed in detail in this article.

Role of vanadium content in hydrogen diffusion behavior in X80 pipeline steel

ABSTRACT The role of vanadium content in hydrogen diffusion behaviour in X80 pipeline steel has been investigated. The results show that the hydrogen diffusion coefficient decreases from 1.54 × 10−6 cm2 s−1 in 1# steel with 0.03 wt-% vanadium to 9.97 × 10−7 cm2 s−1 in 3# steel with 0.14 wt-% vanadium due to the increase in irreversible and reversible traps. With the increase in vanadium content, more vanadium carbides precipitate in tested steels. The length (or number) of the low angle grain boundaries and special grain boundaries increase because of grain refinement, making the number of reversible traps increase. The dynamic condition of diffusible hydrogen in 3# tested steel with the largest number of hydrogen traps is the weakest. To weaken hydrogen-induced cracking dynamic condition, it is recommended to add 0.14 wt-% vanadium to X80 pipeline steel.

Effect of Dimethyl Formamide (DMF) on Vanadium Reloading Over V-Ti SCR Catalyst

Active components reloading is critical process for the catalyst regeneration, which is limited by the low adsorption capacity and unwilling distribution of desired components to the catalyst surface. Herein we demonstrated that with dimethyl formamide(DMF) modification and sequentially reloading of vanadium, the traditional V-Ti SCR catalyst, which uses vanadium as the active components and titanium as the carrier, showed the significantly improved DeNOx performance, owing to the increased adsorption capacity and desired distribution of vanadium. When the DMF concentration was 6%, the adsorption capacity of the promoted catalyst was 3.58 and 6.57 mg/g under vanadyl ion concentrations of 1.5 and 3 g/L, respectively, 135 and 147% higher than that of the original catalyst. Adsorption kinetics demonstrated that the pseudo-second-order kinetic model better describes the process by which vanadyl ions adsorb onto the catalyst. In addition, the adsorption equilibrium indicated that Langmuir model was a closer fit for the vanadyl ion adsorption to the promoted catalyst. After DMF modification, the vanadyl ions were first adsorbed onto the functional groups on the catalyst surface, substantially increasing the vanadium loading on the catalyst surface while limiting the increase in vanadium content within the interior of catalyst, which was conducive to enhancing the DeNOx activity and reducing the increase in the SO2/SO3 conversion. When the vanadium adsorption capacity was 3.5 mg/g, the increase in the DeNOx activity of the promoted catalyst was 68.1% higher than that of the original catalyst, whereas the increase in SO2/SO3 conversion was 28.9% lower than that of the original catalyst. Thus, in the regeneration of SCR catalysts vanadium initial concentration and loading could be reduced.

Preparation and performance study of V2O5/TiO2 catalysts supported on ceramic filter

As the country pays more and more attention to air pollution, the ceramic filter catalyst that can achieve the effects of dust removal and NO reduction simultaneously has a promising prospect. In this paper, ceramic fiber filter supported catalyst was prepared by impregnation method and tetrabutyl titanate method. The effects of vanadium content, space velocity, temperature, and tetrabutyl titanate concentration on the NO conversion of ceramic fiber catalysts were studied, and various physical and chemical methods were used for characterization. The results show that ceramic fiber had excellent multi-dimensional space and bridging structure. The NO conversion of impregnation catalyst and tetrabutyl titanate catalyst increased with the increase of vanadium content and tetrabutyl titanate concentration; At 6700h−1 and a temperature of 300°C, both catalysts can reached the highest catalytic efficiency, tetrabutyl titanate method catalyst was 93.67%. The tetrabutyl titanate catalyst can be loaded more evenly and the filtration pressure drop of the catalyst was smaller than that of the impregnation catalyst. The filtration pressure drop was increased by about 20% compared with the unsupported ceramic fiber.

Structural and spectroscopic studies of V2O5 incorporated lithium-bismuth-boro-tellurite glass ceramics

The effect of dopant concentration on the spectroscopic characteristics of multi-component glass ceramics with the composition 25Li2O-(15-x) Bi2O3-45B2O3-15TeO2-xV2O5(x = 0, 2, 5, 7, 10 mol %) fabricated using traditional melt-quenching process is shown in this study. The prepared glass ceramics were extensively characterised using XRD, FTIR, EPR, etc. The x-ray diffraction (XRD) study reveals that the glasses were semi-crystalline (ceramic) in nature. In addition, Rietveld refinement was used to investigate the crystalline component in the glass network that is responsible for a ceramic nature of the prepared samples. Structural results reveal that the Bi2O3 was found in the crystalline cubic structure of 2 and 5 mol% V2O5 doped glass systems. In other words, the incorporation of V2O5 into the host glass matrix alters the structure of the glass, resulting in semi-crystallization of glass samples. Surprisingly, crystalline structure of LBBTV samples decreases as the V2O5 concentration was increased, owing to the stabilizing of the glass structure at higher doping concentrations. Physical parameters for instance, molar volume is in accordance (decreases till 5 mol % and then increases) with the XRD data. As the vanadium content increases, the FTIR spectra indicate a drastic shift in borate units. EPR spectra of glass ceramics and glasses show resonance signals typical of VO2+ ions.

The Effect of Vanadium Content Coupling with Heat Treatment Process on the Properties of Low-Vanadium Wear-Resistant Alloy.

The development of wear-resistant materials with excellent properties is of great research value in the manufacturing industry. In this paper, a new kind of low-vanadium wear-resistant alloy was designed and characterized to unveil the influence of vanadium content coupling with heat treatment on the microstructure, hardness, and abrasive wear property. The performances of commercial high chromium cast iron (HCCI) and the new low-vanadium wear-resistant alloy are compared. The alloy with 3 wt.% vanadium quenched at 900 °C and tempered at 250 °C, possessing VC, Mo2C, and M7C3 distributed in the martensite matrix, displayed a wear resistance two times better than the HCCI. The results showed that the increase of vanadium content from 0.98 wt.% to 3.00 wt.% resulted in a decrease in the size of M7C3 and a more homogeneous distribution of M7C3. VC with a bimodal distribution is effective for impeding grooving or indenting by abrasives because of their high hardness, which plays a vital role in improving the wear resistance of low-vanadium wear-resistant alloy.

Effect of Vanadium and Strain Rate on Hot Ductility of Low-Carbon Microalloyed Steels

Hot tensile tests were conducted in this study to investigate the effect of strain rate (10−3 and 10 s−1) and vanadium content (0.029 and 0.047 wt.%) on the hot ductility of low-carbon microalloyed steels. The results indicate that a hot ductility trough appears at a low strain rate (10−3 s−1) because of the sufficient time for ferrite transformation and the growth of second particles, but it disappears at a high strain rate (10 s−1). The hot ductility is improved with the increase in strain rate at 700 °C or higher temperatures. In addition, with the increase in vanadium content, the large amounts of precipitate and increased ferrite transformation result in poor hot ductility of steels fractured at a low temperature range (600~900 °C). However, when the steel is fractured at a high temperature range (1000~1200 °C), more vanadium in the solid solution in the austenite inhibits the growth of parental austenite grains and results in grain refinement strengthening, slightly improving the hot ductility.

Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

Controllable p‐Type Doping of 2D WSe2 via Vanadium Substitution

AbstractScalable substitutional doping of 2D transition metal dichalcogenides is a prerequisite to developing next‐generation logic and memory devices based on 2D materials. To date, doping efforts are still nascent. Here, scalable growth and vanadium (V) doping of 2D WSe2 at front‐end‐of‐line and back‐end‐of‐line compatible temperatures of 800 and 400 °C, respectively, is reported. A combination of experimental and theoretical studies confirm that vanadium atoms substitutionally replace tungsten in WSe2, which results in p‐type doping via the introduction of discrete defect levels that lie close to the valence band maxima. The p‐type nature of the V dopants is further verified by constructed field‐effect transistors, where hole conduction becomes dominant with increasing vanadium concentration. Hence, this study presents a method to precisely control the density of intentionally introduced impurities, which is indispensable in the production of electronic‐grade wafer‐scale extrinsic 2D semiconductors.