Effect Of Vanadium Content Research Articles

Effect of Vanadium Content on Microstructure and Wear Behavior of Fe-Cr-Mn-C Surfacing Alloys

Effect of Vanadium Content on Microstructure and Wear Behavior of Fe-Cr-Mn-C Surfacing Alloys

Effects of vanadium content on the microstructure and tensile properties of NbTiVxZr high-entropy alloys

Vanadium boasts a relatively small atomic radius among numerous refractory alloying elements, yet its effects on the microstructure and mechanical behavior of refractory alloys remain enigmatic. In this work, a series of NbTiVxZr high-entropy alloys (HEAs) with low density were formulated to explore the evolution of microstructures and mechanical properties with varying vanadium content. When the vanadium content was low, the matrix exhibited the single-phase body-centered cubic structure. Excessive vanadium contents (NbTiV0.75Zr, NbTiVZr) disrupted phase stability and tended to aggregate at grain boundaries, forming V-rich and Zr-rich phases. These precipitated phases pinned grain boundaries, impeding grain growth and resulting in both grain boundary strengthening and precipitation strengthening, albeit at the expense of grain boundary cohesion, ultimately leading to brittleness. However, these deleterious phases were redissolved, and fracture elongation increased more than 2 times after water quenching at 1200 °C. The microstructural changes induced by heat treatment were corroborated by alterations in grain boundary relaxation behavior, where the redissolution of precipitated phases after water quenching caused a shift of the grain boundary relaxation internal friction peak to a lower temperature and an increase in peak height. This study elucidates the intrinsic relationship between mechanical properties and microstructures with vanadium content in NbTiVxZr alloys, offering insights for the design of TiV-based lightweight refractory HEAs with high strength and excellent ductility.

Comparative study of the oxidative dehydrogenation of cyclohexane over vanadium isomorphic-substituted hydroxyapatite and hydroxyapatite-supported vanadium oxide

Vanadium oxide-modified hydroxyapatite (HAP) with varying vanadium content was synthesized by the coprecipitation and impregnation methods. The structures of the two series of catalysts were compared, and the effects of vanadium content on catalytic properties in cyclohexane oxidative dehydrogenation (ODH) are evaluated. The XRD, UV‒Vis and XPS analyses indicate that the V species in the two series of samples exist in different chemical environments. The samples prepared by the impregnation method are mainly composed of V2O5 species, while the samples prepared by the coprecipitation method show a replacement of a part of the P in the HAP lattice by VO4. The influence of the preparation method and vanadium content on the reaction rate and reaction route for the ODH of cyclohexane is investigated. VHAP shows higher cyclohexene selectivity. The effect of VOx species on the ODH reaction of cyclohexane was investigated and the reaction mechanism was proposed.

Vanadium doped OMS-2 catalysts for one-pot synthesis of imine from benzyl alcohol and aniline: Effects of vanadium content and precursor

A series of vanadium doped cryptomelane-type manganese oxide (V-OMS-2) catalysts were prepared by a simple, low-cost reflux method, and investigated for one-pot imine synthesis from oxidative coupling of benzyl alcohol and aniline with air. The physicochemical properties of the V-OMS-2 catalysts were characterized by various techniques including XRD, BET, SEM, TEM, XPS, H2-TPR and NH3-TPD. It was found that the surface area, Lewis acid sites, the amount of Mn3+ component and active surface oxygen species were much improved with vanadium doping. Consequently, the activity of V-OMS-2 catalyst for oxidative coupling of benzyl alcohol and aniline to imine was enhanced. The highest conversion and the imine yield were obtained over the 3 mol% V-OMS-2 catalyst, being ∼99% and 92%, respectively. Higher vanadium doping (≥ 6 mol%), however, hindered the preservation of OMS-2 crystal structure, leading to a drop in the catalytic performance. The high specific surface area was suggested to be the key contributor to the high catalytic activity of 3% V-OMS-2(1) catalyst. Among the vanadium precursors studied, the catalyst prepared with vanadium pentoxide exhibited a much higher catalytic activity, which can be attributed to its larger surface area, unique mesoporous structure, increased Lewis acid sites and more readily available surface oxygen species. In addition, the stability and recyclability of the catalyst were also studied, and the reaction mechanism was discussed.

The effect of vanadium content on hierarchical martensite structure and yield strength of petroleum casing steels

In the present study, the influence of V content and tempering temperature on the precipitation behavior of hierarchical martensite and yield strength of petroleum casing steels has been systematically studied. Moreover, the relationship between the precipitation behavior and strengthening mechanisms has been analyzed. It was found that yield strength increased with increase of V content. Especially, the steel with 0.10% V has the most efficient strengthening effect, and its yield strength increased nearly 370 MPa compared with that of steel without V. With increase of tempering temperature, the yield strength of steels with 0.10% V decreased in three stages because of the various precipitation behavior on hierarchical martensite structure. The results of nano-indentation tests showed more precipitates were aggregated preferentially in martensite blocks (MBs) of the high V steels (V10 and V15 steels), while the precipitates of V0 and V5 steels were uniformly distributed in martensite packets (MPs), leading to larger nano-hardness of MBs. Moreover, the precipitates on MBs decreased sharply with increase in tempering temperature, and the residual precipitates aggregated on the boundaries of MBs, leading to a dramatic decrease in the nano-hardness of MBs. Considering the size effect and precipitation behavior on the hierarchical martensite structure under different V content and tempering temperature, the traditional yield strength model was modified. Moreover, it was confirmed that the main strengthening mechanisms of V microalloyed petroleum casing steels were grain refinement strengthening and precipitation strengthening.

Effects of vanadium content on the high temperature oxidation behavior of NbTiZrAlV refractory complex concentrated alloys

Oxidation behavior and microstructural evolution of NbTiZrAlV refractory complex concentrated alloys (RCCAs) with vanadium (V) concentration of 3 and 11 at% were investigated at 500 and 800 °C in the air atmosphere. When NbTiZrAlV RCCAs were exposed at 500 °C, the oxidation behavior was controlled by internal oxygen (O) diffusion, and single oxide layer predominating by Ti2ZrO6 and Nb2Zr6O17 were produced after oxidation for 200 h. The mass gains of alloys with 3 and 11 at% V were 0.042 and 0.018 mg/mm2, and corresponding average thickness of oxide layer was 70 and 30 µm. As oxidation temperature was increased to 800 °C, volatilization of V2O5 brought out the aggravation of oxidation degree for NbTiZrAlV RCCA, and complex oxide layers consisting of Nb9VO25, Nb2Zr6O17 and TiO2 were obtained after thermal exposure for 24 h. The mass gains of alloys with the V content of 3 and 11 at% were 1.135 and 0.514 mg/mm2, and the average thickness of oxide layer was 500 and 300 µm, respectively. In both cases, the antioxidant performance of NbTiZrAlV RCCA was significantly improved by the increased content of V. And the enhanced oxidation resistance could be ascribed to the fact that the increase of V addition enhanced the atom diffusion resistance via minimizing mixing enthalpy and maximizing configurational entropy.

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.

Vanadium Doped Oms-2 Catalysts for One-Pot Synthesis of Imine from Benzyl Alcohol and Aniline: Effects of Vanadium Content and Precursor

Vanadium Doped Oms-2 Catalysts for One-Pot Synthesis of Imine from Benzyl Alcohol and Aniline: Effects of Vanadium Content and Precursor

The Effect of Vanadium Content on Hierarchical Martensite Structure and Yield Strength of Petroleum Casing Steels

The Effect of Vanadium Content on Hierarchical Martensite Structure and Yield Strength of Petroleum Casing Steels

Effect of vanadium content on the microstructure and wear behavior of Fe(13-)VxB7 (x = 0–5) based hard surface alloy layers

In this study, Fe (13- x ) V x B 7 (x = 0, 1, 2, 3 and 5) based hard surface alloy layers were formed on SAE 1020 steel substrate surface by tungsten inert gas (TIG) welding method. The effects of vanadium addition on microstructure, hardness and wear rate in this coating layer were investigated using optical microscope, SEM (EDS), X-ray diffractometer, hardness and wear tests. As a result of microstructure studies and phase analysis, it was determined that the structures of alloy layers consist of α-(Fe,V), α-(Fe,V) + (Fe,V) 2 B eutectic, and (V,Fe)B phases. As a result of the macrohardness tests, it was found that the hardness of the alloy layers varied between 42.3 ± 1.7–57.2 ± 5.1 HRC. Moreover, the microhardness of iron and vanadium borides formed in the coating layers was found to be between 1901 ± 127–3082 ± 299 HV 0.01 , respectively. As a result of the wear tests, it was observed that as the amount of vanadium added to the hard surface alloy layer increased, the wear rates decreased for all applied loads. Morover, Scanning Electron Microscopy (SEM) images of the worn surfaces showed that the wear mechanisms were adhesive, micro-abrasive and oxidative. • Coating on Fe (13- x ) V x B 7 (x = 0, 1, 2, 3 and 5) based hardfacing steel surface with different vanadium content. • The effect of vanadium content on the microstructure of Fe-V-B based coatings. • Determination of the mechanical properties of the hard surface alloy layer depending on the vanadium content.

Effect of vanadium content on microstructure and properties of in situ TiC reinforced VxFeCoNiCu multi-principal-element alloy matrix composites

Effect of vanadium content on microstructure and properties of in situ TiC reinforced VxFeCoNiCu multi-principal-element alloy matrix composites

Effects of vanadium content on the carbides transformation and strengthening mechanism of MPS700V hot-work die steel at room and elevated temperatures

The effects of vanadium content on the microstructural and mechanical properties of a newly developed hot-work die steel (MPS700V) at room and elevated temperatures have been investigated in this paper. It shows that the ultimate tensile strength (UTS) of MPS700V at room temperature and 700 °C are both strongly dependent on the V content. With the increase of V content from 0 to 1.2% V, The UTS at room temperature increases from 1127 MPa to 1442 MPa, and the UTS at 700 °C increases from 400 MPa to 550 MPa. The transmission electron microscope (TEM) shows that the addition of V is beneficial to increase the nucleation rate and volume fraction of MC nano-carbides during the tempering process, and the size of the MC nano-carbides decreases with the increase of V content. The addition of V also increases the thermal stability of MC nano-carbides at 700 °C, which can be related to the reducing the interface mismatch between MC and matrix. Furthermore, a transformation from Orowan bypass strengthening mechanism to shearing strengthening mechanism caused by the V addition is proposed based on the theoretical analysis and TEM observation.

Effect of Vanadium Content on the Microstructure and Mechanical Properties of IN718 Alloy by Laser Cladding.

Microalloying vanadium can change the segregation state of Nb element in IN718 alloy, reduce the formation of harmful Laves phase and refine the dendritic structure of IN718 alloy during the laser process. Therefore, IN718 alloys with V content from 0.081 to 1.88 wt.% were prepared and evaluated. Metallographic microscopy and scanning electron microscopy were used to observe the corresponding morphology, structure, and distribution of elements. First of all, it was found that the addition of V refines the grain size of IN718 alloy and reduces the primary dendrite arm spacing. Secondly, adding V to IN718 alloy can reduce the porosity of the cladding layer. The elements are uniformly distributed in the cladding layer, and the addition of vanadium reduces the segregation degree of the Nb element, which is conducive to homogenization. In addition, microhardness and residual stress were also investigated. Finally, the addition of vanadium was shown to have no apparent effect on the tensile strength and yield strength but can significantly improve the elongation of IN718 alloy. In conclusion, the microstructure and mechanical properties of IN718 alloy with 0.081 wt.% vanadium content provide a new solution to improve the application level of IN718 alloy in laser cladding.

Influence of Vanadium Content on Hot Deformation Behavior of Low-Carbon Boron Microalloyed Steel

Single-pass compression tests were performed to investigate the hot deformation behavior of low-carbon boron microalloyed steel containing three various vanadium contents at 900–1100 °C and strain rate of 0.01–10 s−1 using the MMS-300 thermal mechanical simulator. The flow stress curves of investigated steels were obtained under the different deformation conditions, and the effects of the deformation temperature and strain rate on the flow stress were discussed. The characteristic points of flow stress were obtained from the stress dependence of strain hardening rate; the activation energy of investigated steels was determined by the regression analysis; the flow stress constitutive equations were developed; the effect of vanadium content on the flow stress and dynamic recrystallization (DRX) was investigated. The result showed that the flow stress and activation energy (316.5 kJ mol−1) of the steel containing 0.18 wt% V were significantly higher than those of the steels with 0.042 wt% and 0.086 wt% V, which was related to the increase in solute drag and precipitation effects for higher vanadium content. DRX analysis showed that the addition of vanadium can delay the initiation and the rate of DRX.

Effect of vanadium content on as-cast micro-structure and mechanical properties of alloy 718

Effect of limited amounts of vanadium from 0.081 to 1.88 wt% on the micro-structure and mechanical properties in alloy 718 is evaluated. Corresponding morphology, constituent and structure are measured by metallurgical microscope, energy dispersive spectrum, scanning electron microscopy, electron probe micro-analysis and x-ray diffraction. Results indicate that vanadium can refine secondary dendrite arm spacing and decrease segregated spot volume fraction at the investigated levels. Vanadium does not obviously change the precipitated phase composition or structure, but acts as a grain refiner and reduces the precipitated amount of the harmful Laves phase, which results in an optimized as-cast micro-structure for the next homogenization process. In addition, mechanical properties are also tested. They show vanadium may enhance strength to a certain degree. In other words, vanadium altered the micro-structure characteristics of alloy 718 and affected its mechanical properties, and the alloy containing 0.081 wt% vanadium provides the best compromise between strength and micro-structures.

K+ deactivation of V2O5-WO3/TiO2 catalyst during selective catalytic reduction of NO with NH3: Effect of vanadium content

The effect of vanadium content on the resistance to K+ deactivation of V2O5-WO3/TiO2 SCR catalyst in biomass-fired flue gas was investigated. Catalytic activity and ammonia oxidation were measured, and the properties of fresh and K+-deactivated catalysts were characterized by XRD, N2 physisorption, H2-TPR, NH3-TPD and NH3-DRIFT. The BET surface area decreases with increased vanadium content for both fresh and K+-poisoned samples, but it is not responsible for catalyst deactivation. Ammonia oxidation starts from 300 °C and becomes more important with increasing vanadium content and at higher temperature. K+ can inhibit ammonia oxidation, but inactivates the newly generated NO2 to be reduced. The increase of vanadium content reduces mainly the Lewis acid sites, while the amount of BrØnsted acid sites increases. Monomeric and polymeric vanadium are the dominant species on the TiO2 support, and the amount of isolated vanadyl (V = O) species decreases with V2O5 content while the amount of V-OH species in polymeric vanadia increases. Isolated vanadyl species are advantageous to high-temperature catalytic activity while polymeric vanadia species increase ammonia and K+ adsorption. The (3 wt% V2O5)-WO3/TiO2 catalyst shows the best performance for both NO reduction and K+ resistance due to it containing both monomeric and polymeric vanadia species (or V = O and V-OH). Catalysts with 3 wt% V2O5 are preferable for flue gases with high alkali metal contents. Finally, the mechanism of reaction for different vanadium contents and corresponding K+-poisoning are also discussed.

Effect of vanadium content on hydrogen diffusion behaviors and hydrogen induced ductility loss of X80 pipeline steel

In this study, the number and size distribution characteristics of fine nanoscale precipitates and their effects on hydrogen diffusion and hydrogen induced ductility loss were investigated in X80 pipeline steel. The results showed that with the increase of vanadium content, more vanadium carbides precipitated in the tested steels and the proportion of precipitates with size less than 10 nm distinctly increased, which fixed a large amount of diffusible hydrogen atoms as effective traps. The hydrogen diffusion coefficient decreased from 5.12 × 10−6 cm2 s−1 in the vanadium-free V1 steel to 9.94 × 10−7 cm2 s−1 in the V4 steel with 0.13% V. In addition, for the tested steels containing vanadium, the hydrogen embrittlement gradually decreased with increasing nanoscale vanadium precipitates, which pinned the movable dislocations and weakened the hydrogen-enhanced localized plasticity. The V4 steel with 0.13% V had the best performance to resist to hydrogen induced ductility loss.

Hydrogen Production by Steam Reforming of Natural Gas Over Vanadium-Nickel-Alumina Catalysts.

A series of vanadium-nickel-alumina (xVNA) catalysts were prepared by a single-step sol-gel method with a variation of vanadium content (x, wt%) for use in the hydrogen production by steam reforming of natural gas. The effect of vanadium content on the physicochemical properties and catalytic activities of xVNA catalysts in the steam reforming of natural gas was investigated. It was found that natural gas conversion and hydrogen yield showed volcano-shaped trends with respect to vanadium content. It was also revealed that natural gas conversion and hydrogen yield increased with decreasing nickel crystallite size.

The effect of vanadium content and speciation on the activity of VOx/ZrO2 catalysts in the conversion of ethanol to acetaldehyde

Catalytic conversion of ethanol to acetaldehyde under oxidizing conditions over VOx/ZrO2 catalysts with various surface VOx densities has been investigated. Vanadium complexes anchored on the surface of zirconia oxide support are characterized in detail and their catalytic properties reported. The catalysts were prepared by incipient wetness impregnation from a peroxidic solution of ammonium metavanadate. The texture and crystallinity of the catalysts were investigated by N2 physisorption and XRD analysis. The speciation and redox properties of the vanadium complexes were studied by dispersive Raman spectroscopy and the temperature programmed reduction (TPR) method. The effects of vanadium species distribution and ZrO2 support crystallinity on the catalytic activity in the oxidative dehydrogenation of ethanol to acetaldehyde were analyzed and discussed in a broad context. A comparison of the catalytic results with details of the distribution of vanadium complexes has led to the conclusion that vanadium speciation has a great impact on catalytic behavior and that small oligomeric vanadium complexes dominate in the catalysts with vanadium content slightly above half of monolayer capacity, exhibiting the highest catalytic activity and very high selectivity to acetaldehyde (better than 93%). A comparison of the catalytic behavior of VOx supported on tetragonal and monoclinic ZrO2 phases has not revealed any differences in the activity or selectivity of the ethanol ODH reaction. Long-term catalytic experiments have shown good stability of the catalysts (stable conversion and selectivity for more than 600 h).

Toward the Optimization of a Cr‐V Bimetallic Catalyst for Producing Bimodal Polyethylene: Effect of Vanadium Content and Calcination Temperature

AbstractThis work covers the synthesis of bimodal polyethylene with a SiO2‐supported vanadium‐oxide/silyl‐chromate (Cr‐V) bimetallic catalyst, which is prepared by using the residual hydroxyl groups on the VOx/SiO2 catalyst precursor to support chromium species. The effects of vanadium content and calcination temperature of the support on catalyst activity and polymer properties are investigated in detail. It is found that increasing vanadium content in the Cr‐V catalyst leads to the decline of catalyst activity, while the molecular weight of the resulting polyethylene is raised. On the other hand, the decline of catalytic activity at high vanadium content in the Cr‐V catalyst can be remedied by decreasing the calcination temperature of the support, and the molecular weight of the polymers is reduced at the same time. However, too low a calcination temperature is not beneficial for catalyst activity due to the poisoning effect of the excess hydroxyl groups on the active sites, and this would cause the increase of molecular weight as well.