Presence Of Vanadium Pentoxide Research Articles

Strong enhancement of the optical properties of SiNWs by the deposition of snowball-like V2O5 nanoparticles

In this work, the morphological and optical properties of vanadium pentoxide (V2O5) nanoparticles deposited on silicon nanowires (SiNWs) have been investigated. SiNWs are obtained by metal-assisted chemical etching (MACE) method. The deposition of vanadium pentoxide on SiNWs layer was performed by vacuum thermal evaporation system for different durations. Scanning electronic microscope (SEM) images show the formation of snowball-like V2O5 nanoparticles on the SiNWs surface. A large condensation of V2O5 elements was observed by increasing the evaporation time. The changes in bonds and chemical composition at the surface of the SiNWs-V2O5 nanocomposites were examined by Raman and Fourier transform infrared (FTIR) spectroscopies. The X-ray Diffraction (XRD) technique revealed the presence of orthorhombic structure of V2O5 layer with good crystallinity. The SiNWs-V2O5 composites show strong visible PL due to the contribution of the radiative band edge transitions of vanadium pentoxide. The emission of V2O5 layer is in the same energy range as that of SiNWs thus leading to a large increase in PL intensity. Optical band gap (Eog) was determined from UV–Vis-IR spectroscopy. The presence of vanadium pentoxide on the SiNWs surface causes an increase in the value of Eog from 1.851 to 2.075 eV. This increase was explained by Burstein-Moss effect.

Preparation and formulation of bird repellent pesticide

ln this research, Anthraquinone was prepared from the oxidation of anthracene (obtained from coal tar) by sodium perchlorate in presence of vanadium pentoxide as a catalyst in a good yield and high purity. Anthraquinone was formulated as a wettable powder (w.p.) to prepare a bird repellent pesticide> which leave no toxic residue in crop plants.

Understanding the influence of microstructure on hot corrosion and erosion behavior of suspension plasma sprayed thermal barrier coatings

Thermal barrier coatings (TBCs) are bilayer systems comprising a 7–8 wt% yttria partially stabilized zirconia (YSZ) top coat deposited over a metallic bond coat. Suspension plasma spraying (SPS) is an advanced and attractive top coat processing technique due to its capability to yield a variety of microstructures, including the desired columnar microstructure for enhanced strain tolerance and durability. This work attempts to investigate the desirable microstructural features in an SPS processed TBCs to mitigate hot corrosion and minimize erosion related losses that are often responsible for coating degradation. SPS processed TBCs were deposited utilizing three different spray conditions to obtain distinct microstructural features (column density, interpass [IP] porosity bands, column width), porosity content, and mechanical properties. Apart from comprehensive characterization utilizing SEM, XRD and micro-indentation tests, the as-deposited TBCs were subjected to hot-corrosion tests in the presence of vanadium pentoxide and sodium sulfate as corrosive salts. Post-corrosion analysis revealed complete infiltration of the molten salts in all the investigated TBCs. However, the delamination cracks generated due to the infiltrated corrosive species were minimal in case of TBCs with higher fracture toughness. The differences in microstructure and mechanical properties also led to differences in erosion performance, with TBCs possessing minimal total porosity content and high fracture toughness best resisting erosion related damage. Post-erosion analysis revealed that the TBCs with higher fracture toughness and micro-hardness showed superior erosion resistance. Based on the erosion and corrosion results and subsequent post-mortem of failed specimens, plausible damage mechanisms are proposed. Findings from this work provide new insights on developing damage tolerant TBCs microstructures with enhanced durability when exposed to erosion and hot corrosion environments. • SPS TBCs with varying columnar microstructural features and mechanical properties were deposited. • Influence of parameters (suspension feed rate, spray distance, etc.) on microstructural features in SPS TBCs examined. • Desirable microstructural features were identified to minimize erosion and hot corrosion.

Microstructural study and hot corrosion behavior of bimodal thermal barrier coatings under laser heat treatment

In this study, nanostructured YSZ powders were deposited on the Hastalloy X Superalloy substrate coated with a metallic bond coat by plasma spraying to produce a nanostructured thermal barrier coating with bimodal microstructure. After that, the coated samples were heat-treated using a Nd:YAG laser. Then, the microstructures of the conventional and nanostructured TBCs before and after the laser glazing process were examined using a scanning electron microscope (SEM). The coating phases were studied by X-ray diffractometry (XRD). The high-temperature corrosion behavior of the nanostructured plasma sprayed coating in the presence of Vanadium pentoxide and Sodium sulfate molten salt was compared with that of the conventional coatings before and after laser treatment at 1050 °C. The hot corrosion results showed that the coatings had a similar degradation mechanism based on which the corrosive molten salt reacted with the stabilizer of YSZ, producing hot corrosion products such as YVO4. It led to an unwanted phase transformation from tetragonal (t) to monoclinic (m) Zirconia and the final degradation of the TBC system. However, reducing molten salt penetration, decreasing surface roughness and, reduction of the specific surface area are three important mechanisms that improved hot corrosion resistance, finally extending the lifetime of the glazed samples. The results also showed that the nanostructured TBC had higher hot corrosion resistance in comparison with other samples.

Surface modification of CdS quantum dots: an effective approach for improving biocompatibility

The surface of Quantum Dots (QDs) decides the influence of their performance in biomedical, sensing as well as in photocatalysis applications. Herein, we report a surface modification of Cadmium sulfide (CdS) QDs in the presence of Vanadium pentoxide (V2O5) denoted as CdS@V2O5, by single-source inorganic cluster approach. The X-Ray Diffraction (XRD) pattern, Photoluminescence (PL) spectra, Raman spectra as well as biocompatibility results strongly indicate the surface modification of CdS QDs. XRD pattern of CdS@V2O5 QDs shows a crystal structural phase change from Zinc blende to Wurtzite, which was further confirmed by high-resolution TEM and selected area electron diffraction pattern. Biocompatibility test with MCF-10A and HeLa cell lines with optimized dosages of CdS and CdS@V2O5 QDs were carried out, and results show a significant enhancement in the viability of cell lines for CdS@V2O5 QDs, whereas cell lines exposed to CdS QDs has negligible viability. The enhancement in biocompatibility of CdS@V2O5 QDs may be due to bond formation between Cd dangling bond and V2O5. The optimized dosages of CdS@V2O5 QDs can prove very useful application in biomedical science.

Inhibitors and coatings against vanadate-containing oil ash corrosion of boilers

Abstract Corrosion in oil-fired boilers is accelerated in the presence of vanadium, sodium, and sulfur from low grade fuels. In order to avoid vanadate-induced corrosion several ceramic inhibitors and intermetallic coatings and their interaction were studied. Inhibitor ceramics such as CaO and MgO tend to react strongly with vanadium oxides forming vanadates with higher melting temperatures whereas Cr 2 O 3 , Al 2 O 3 , and SiO 2 are the most protective oxides for alloys at high temperatures even in the presence of vanadium pentoxide. Three potential inhibitors were tested on uncoated as well as on Cr, Al, and AlSi diffusion coated 10CrMo9-10 steel by immersion in 60 mol% V 2 O 5 –40 mol% Na 2 SO 4 salt at 650 °C. Materials performance was analyzed by calculating substrate recession rates and by metallographic characterization of the corrosion scales and of the metal subsurface zones so that the mechanism and extent of corrosion could be characterized. In the end different materials combinations (coatings and inhibitors) could be ranked with regard to the detrimental or beneficial role of the different approaches. The present results thus provide a much deeper insight into materials resistance in vanadium-containing environments at boiler simulating conditions than previous studies.

ChemInform Abstract: Thermal Decomposition of Sodium Oxalate in the Presence of V2O5. Mechanistic Approach of Sodium Oxibronzes Formation.

Abstract The thermal decomposition of sodium oxalate in the presence of vanadium pentoxide in 1:2 molar ratio affords the vanadium bronze α'-NaV 2 O 5 . Complementary techniques such as thermogravimetry (TG), differential thermal analysis (DTA), gas analysis (GC), X-ray powder diffraction (XRD) and infrared spectroscopy (IR) were applied to provide information on the operative mechanism. A promotive effect of vanadium pentoxide on the decomposition of sodium oxalate takes place. Carbonate species and carbon monoxide could not be detected as intermediates during the decomposition which occurs over a wide range of temperatures, typically between 200 and 525°C. The progressive formation of Na x V 2 O 5 bronzes with x increasing up to unity with temperature leads us to propose that the carbon-carbon bond cleavage of the oxalate is promoted by electron transfer between the oxalate anion and the vanadium pentoxide matrix. Such behaviour is dependent on the redox potential of the metal ion initially present in the oxalate and of vanadium pentoxide.

Mullite phase enhancement in Indian kaolins by addition of vanadium pentoxide

Mullite phase development in Indian kaolinites was investigated in the presence of vanadium pentoxide and characterized by X-ray diffraction, FESEM and FTIR spectroscopy. The addition of V 2O 5 markedly enhanced the amount of mullite phase and also lowered the mullitization temperature. The mullite phase was highly crystalline with rod shaped particles of average dimensions of 350–500 nm and 70–100 nm. A maximum of 27% increase in mullite phase was obtained at 7% (by mass) V 2O 5 after sintering at 1000 °C for 2 h.

Comparative Analysis of Methods for Determination of Arsenic in Coal and Coal Ash

In this paper the comparative analysis of different methods for the preparation and analysis of arsenic content in coal and coal ash have been presented. The suggested method is coal digestion method, i.e., coal ash digestion using the mixture of acids: nitric and sulphuric in presence of vanadium-pentoxide as catalyzer. The comparative analysis of different recording techniques (AAS-GH, AAS-GF and ICP-AES) has also been presented. For arsenic recording the suggested technique is AAS-GF technique. The obtained results show that the method of high precision, high sensitivity and high reproductivity has been obtained.

The catalytic activity of vanadium pentoxide film modified electrode on the electrochemical oxidation of hydrogen sulfide in alkaline solutions

Abstract The presence of vanadium pentoxide (V2O5) as a deposited film at the glassy carbon electrode was found to promote the electrochemical oxidation of aqueous sulfide solution. The over potential of sulfide oxidation in alkaline buffer solution (pH 10.28) at this film modified electrode is decreased substantially by 500 mV in comparison to that at the bare glassy carbon electrode (GCE). The proposed mechanism indicated that the primary electron transfer and hence the observed anodic current at the modified electrode was due to the oxidation of the reduced species (V2O4) into VO 3 - species which precipitated as V2O5 at the electrode surface. The electrode process found to be controlled by mass transport conditions and the calculated value of diffusion coefficient for sulfide (6.8 × 10−9 m2 s−1) was 10-folds greater than that at the GCE. A Tafel-like plot for the data under the present experimental conditions is used to calculate the standard rate constant for sulfide oxidation. The rate constant adopted a value of 6.6 × 10−5 cm s−1 at high [HS−], where the electrode process is expected to proceed at a slow rate. The reactivity of the present system was insignificantly affected by the formation of elemental sulfur and other insoluble vanadium species.

Pitch and coke combustion in a circulating fluidized bed

Combustion tests were carried out with two hydrocarbon processing residues: a high-volatile pitch from a hydrotreating process and a green petroleum coke. It was demonstrated that both fuels can be treated successfully by circulating fluidized bed combustion, with sulfur capture by limestone addition. Levels of calcium sulfide in the baghouse ash were acceptable in both cases, and were especially low for the pitch. The presence of vanadium pentoxide in the residues from pitch burning appears to have caused significant conversion of SO 2 to SO 3, Limestone addition led to an increase in NO x emissions for the pitch, but to a decrease for the coke, probably because of the low volatile matter of the latter, such that limestone catalysis of NO x reduction by CO predominated over catalysis of N 2O production from fuel volatile nitrogen. N 2O levels were higher for the coke than for the pitch or other fuels investigated.

Thermal decomposition of sodium oxalate in the presence of V 2O 5: Mechanistic approach of sodium oxibronzes formation

The thermal decomposition of sodium oxalate in the presence of vanadium pentoxide in 1:2 molar ratio affords the vanadium bronze α'-NaV 2O 5. Complementary techniques such as thermogravimetry (TG), differential thermal analysis (DTA), gas analysis (GC), X-ray powder diffraction (XRD) and infrared spectroscopy (IR) were applied to provide information on the operative mechanism. A promotive effect of vanadium pentoxide on the decomposition of sodium oxalate takes place. Carbonate species and carbon monoxide could not be detected as intermediates during the decomposition which occurs over a wide range of temperatures, typically between 200 and 525°C. The progressive formation of Na x V 2O 5 bronzes with x increasing up to unity with temperature leads us to propose that the carbon-carbon bond cleavage of the oxalate is promoted by electron transfer between the oxalate anion and the vanadium pentoxide matrix. Such behaviour is dependent on the redox potential of the metal ion initially present in the oxalate and of vanadium pentoxide.

Epoxidation of Allylic Alcohol in the Presence of Vanadium Pentoxide

Reactions of geraniol with TBHP in the presence of several metal oxides such as SiO2, TiO2, WO3, and V2O5 were carried out. V2O5 showed the high catalytic activity in epoxidation reactions. Allylic alcohols such as nerol, cinnamyl alcohol, trans, trans-farnesol, 1-hexen-3-ol, 1-octen-3-ol, (-) -carveol, and (±) -trans-p-menth-6-ene-2, 8-diol were also successfully epoxidized. No epoxidation took place on using geranyl acetate, citral, or cinnamyl acetate.

Formation of sodium and copper vanadium oxibronzes via oxalate decomposition: Thermal and X ray studies

The thermal decomposition of sodium and copper oxalates in the presence of vanadium pentoxide in a 0.5:1 molar ratio affords the vanadium bronzes α′-NaV 2O 5 and β-Cu 0.5V 2O 5. The use of complementary techniques such as TG, DTA, gaz analysis and X-ray powder diffraction permit to propose a reaction scheme for the formation of the above-mentioned compounds. Copper oxalate leads to CO 2 and metallic copper which then incorporates to V 2O 5. The reaction mechanism for sodium oxalate is less straightforward. A new phase, β′Na xV 2O 5 has been characterized during the course of the formation of NaV 2O 5.

Electrochemical study of catalytic oxidation of naphthalene in molten sulphate pyrosulphate at 425� C with vanadium pentoxide

Naphthalene oxidation in a molten mixture of potassium sulphate pyrosulphate at 425° C in the presence of vanadium pentoxide takes place in three stages. The electrochemical study of each stage has led to the proposal of kinetic equations for the initial rates: (i) naphthalene oxidation by the medium $$V_1^0 = 2 x 10^{ - 2} P_{C_{10} H_8 }$$ (ii) mixture regeneration by V2O5 $$V_2^0 = 19.2 x 10^{ - 2} P_{SO_2 }$$ (iii) catalyst regeneration by oxygen $$V_3^0 = 82.8P_{O_2 } [V(IV)]^2$$ This shows that the molten salt acts not only as a solvent but also as a reagent in the catalytic process.

Synthesis of l-Aryl-3-formyl-3-methyltriazenes, Potential Metabolites of l-Ary1-3,3-dimethyltriazenes

Some para-substituted 1-aryl-3,3-dimethyltriazenes were oxidized with tert-butyl hydroperoxide in the presence of vanadium pentoxide as a catalyst. Under these conditions, the corresponding 1-aryl-3-formyl-3-methyltriazenes, 1-aryl-3-tert-butylperoxymethyl-3-methyltriazenes, and p-nitrobenzenes were obtained. The 1-aryl-3-formyl-3-methyltriazenes might play a role in the metabolic oxidation of the 1-aryl-3,3-dimethyltriazenes, which are active as mutagenic, carcinogenic, and antitumor agents.

Effect of Vanadium Pentoxide on the Incorporation of (2‐14C)‐Acetate into Fungal Lipids

AbstractMycelia of Glomerella cingulata grown in the presence of vanadium pentoxide (V2O5), incorporated many times less (2‐14C)‐acetate into their lipids than mycelia of the same organism grown in the absence of V2O5. All neutral and polar lipid fractions investigated were affected. These data suggested that V2O5 depressed lipid biosynthesis in G. cingulata.

Procedure of Direct Conversion of Sulphates into SO2 for Mass Spectrometric Analysis of Sulphur

Thermal decomposition of sulphates in the presence of vanadium pentoxide and metallic copper serves as a quick method of direct conversion of sulphates into sulphur dioxide. It is suitable for the mass spectromeiric measurements of δ34S in natural sulphates. The absolute error of the method is ±0.4‰.

Studies in the corrosion of metals under melts—I: Theoretical survey of fire-side corrosion of boilers and gas-turbines in the presence of vanadium pentoxide

The nature and cause of residual fuel oil-ash corrosion is briefly reviewed. A critical appraisal has been made of the importance of the study of (a) the transport properties of vanadic melts, (b) the characteristics of the metal-slag interface, and (c) the energetics of the corrosion. From elementary concepts of diffusion-controlled processes, equations have been derived for corrosion progress of metals in the presence of molten vanadium pentoxide. It is predicted that the rate-controlling mechanism of vanadic corrosion involves both an inward diffusion of oxygen and an outward diffusion of corrosion products. A mathematical analysis of such sequential mass-transfer processes shows that the experimental activation energy corresponds to the process having the higher energy of activation; however, the experimental action constant involves contributions from both processes. Problems in predicting the possible mechanism of oxygen transport and conductivity are discussed.

Oxidation of High‐Melting Organic Compounds by Potassium Chlorate

AbstractThe oxidation of anthracene, 9,9′‐bianthryl and 1,1,2,2‐tetraphenyl‐ 1,2‐bis (9,10‐dihydro‐anthracenyl‐9) ethane (TPDAE) by potassium chlorate and perchlorate, in the presence of vanadium pentoxide, was studied both by a batch method in closed ampoules and by gravimetry. The reactions took place with the participation of the gaseous phase while certain stages seem to be solid‐solid processes.