Search for: vanadium
Total 76 records
Photo-degradation of methelyne blue over V2O5- TiO2 nano-porous layers synthesized by micro arc oxidation, Article Catalysis Letters ; Volume 134, Issue 1-2 , 2010 , Pages 162-168 ; 1011372X (ISSN) ; Golestani Fard, F ; Zaker Moshfegh, A ; Sharif University of Technology
V2O5-TiO2 porous layers were synthesized via micro-arc oxidation for the first time. The effect of the applied voltage on morphology, composition, and photo-activity of the layers was investigated. The layers, which consisted of anatase, rutile, and vanadium pentoxide phases, revealed an enhanced photo-activity. About 93% of methylene blue solution was degraded on the synthesized layers after 120 min UV-irradiation with a reaction rate constant of k = 0.0228 min-1. The band gap energies of the vanadia-titania and pure titania layers were calculated as 2.56 and 3.39 eV, respectively
Synthesis of NO-bidentate- and ONO-Tridentate-Oxovanadium(IV) Complexes Supported on Fe¬3O4@SiO2 Core-Shell Magnetic Nanoparticle and Their Application in Oxidation of Sulfides and Alkenes
Sharif University of Technology
To synthesizeFe3O4@SiO2 core-shellnanoparticles,at first,Fe3O4 magnetic nanoparticle synthesisedby usingcoprecipitation method.Then tetraethyl orthosilicate (TEOS) was used to coverthe surface of this nanoparticle with layer of silica. In the next step, the surface of Fe3O4@SiO2 core-shellnanoparticlesfunctionalized by NO-bidentate and ONO-tridentate ligands. Finally the functionalized nanoparticle coordinated to oxovanadium(IV) to achieve Fe3O4@SiO2@NO-VO2+ and Fe3O4@SiO2@ONO-VO2+nanocatalysts for selective oxidation of sulfides to corresponding sulfoxide and oxidation of alkene. FT-IR, 1HNMR, 13CNMR, SEM, VSM and ICP analysis were used for characterization of this nanocatalysts. This...
Nanoparticle supported, magnetically separable vanadium complex as catalyst for selective oxidation of sulfides, Article Journal of Coordination Chemistry ; Volume 65, Issue 4 , 2012 , Pages 591-601 ; 00958972 (ISSN) ; Haghdoost, M. M ; Shahbazirad, A ; Sharif University of Technology
A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica-coated Fe 3O 4 nanoparticles. This straightforward preparation yields magnetically separable Fe 3O 4@SiO 2@VO(salen) nanoparticles with high vanadium loading. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles
Article Journal of Coordination Chemistry ; Volume 63, Issue 21 , May , 2010 , Pages 3849-3858 ; 00958972 (ISSN) ; Amini, M ; Sharif University of Technology
The monoanionic bidentate Schiff base, N-(phenolyl)-benzaldimine (HL), has been employed to synthesize a new vanadium(IV) complex of general composition [VO(L)2] (where L = O, N donor of Schiff base). The ligand and complex have been fully characterized by elemental analyses, molar conductance data, FT-IR, 1H- and 13C-NMR, and UV-Vis spectroscopies. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this complex catalyst using Oxone as oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature
Morphological investigations of nanostructured V2O5 over graphene used for the ODHP reaction: From synthesis to physiochemical evaluations, Article Catalysis Science and Technology ; Volume 5, Issue 2 , Sep , 2015 , Pages 910-924 ; 20444753 (ISSN) ; Kazemeini, M ; Khorasheh, F ; Rashidi, A. M ; Sharif University of Technology
Royal Society of Chemistry 2015
Oxidative dehydrogenation of propane (ODHP) in a fixed-bed reactor over synthesized vanadia nanocatalysts was investigated physicochemically. Several vanadium pentoxide (V2O5) nanostructures including rod-, belt-, tube-, needle- and flower-like forms were successfully synthesized via reflux and hydrothermal processes utilizing different templates such as monoamines, diamines, aromatic and alcoholic amines. The morphologies of the obtained products were found to be sensitive to the types of templates used. Nanorods obtained were 1.4 μm in length and about 97 nm in width while the VO2(B) nanotubes were of about 76 nm average diameter and up to 1.2 μm long. The diameters of the V2O5 nanotubes...
Article International Journal of Mineral Processing ; Volume 138 , May , 2015 , Pages 49-54 ; 03017516 (ISSN) ; Ardakani, M. S ; Keshavarz Alamdari, E ; Haghshenas Fatmesari, D ; Darvishi, D ; Sadrnezhaad, S. K ; Sharif University of Technology
In the present study, the thermodynamics and mechanisms of vanadium extraction by a mixture of bis-2-ethylhexyl phosphoric acid (D2EHPA) and tri-n butyl phosphate (TBP) from sulfate medium were investigated. It was found that the maximum extraction percent of vanadium occurs at pH 1.8 under ambient conditions; this phenomenon was ascribed to the predominant presence of cationic species of vanadium (VO
2+) at this pH. Based on the Fourier Transform Infrared (FT-IR) spectrums, the POH bond of D2EHPA was found responsible for the extraction of VO 2+ species through a cationic exchange mechanism. Employing the slope analysis method showed that the stoichiometric reaction...
Article Applied Surface Science ; Volume 253, Issue 5 , 2006 , Pages 2581-2588 ; 01694332 (ISSN) ; Iraji zad, A ; Sharif University of Technology
We have investigated segregation of copper at the surface of V 2 O 5 films deposited onto Cu substrate by employing surface analysis techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirmed that the Cu is segregated at the surface and its chemical state is Cu 2 O. According to secondary ion mass spectroscopy (SIMS) and glow discharge spectroscopy (GDS), the Cu concentration inside the deposited V 2 O 5 layer is low. Ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS) revealed the segregation alters the surface local density of states. Surface analysis of deposited samples in ultra high vacuum (UHV) condition...
Investigation of Vanadium Dopant and SiO2 Prelayer on the Self-Cleaning Property of TiO2 Coatings by Sol-Gel Dip Coating Method, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali
Because of limitation of titania coating that can act as self-cleaning surface under UV light irradiation, introduction of transition metal ions into titania lattice can decrease band gap energy of titania in order to activate the coating under visible light irradiation. In this research, by using vanadium element and silica prelayer, a titania coating was deposited on the soda-lime glass substarte to produce self-cleaning surface. The scope of coating was to increase the photocatalytic activity and hydrophilicity of vanadium doped titania coating on the soda-lime glass and silica coated glass by sol-gel dip coating method. XRD and FTIR analysis were done on the powders with different...
An Investigation on Photocatalytic Behavior of N-doped and N-V-doped TiO2 Thin Film, Coated on Glass Surface by Sol-gel Dip Coating Method, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali
In this study, the photocatalytic activity and hydrophilicity of coat improved using Nitrogen and Vanadium elements as dopant in TiO2 coating. By using vanadium and nitrogen elements and silica prelayer, a titania coating was deposited on the soda-lime glass substrate by sol-gel dip coating method to produce self-cleaning surface. XRD and FTIR analyses were done on the powders after heat treating at in 450˚C for 30 min. XPS analysis was done for investigation of N replacement in titania structure. The band-gap energy of formed anatase was derived using UV-Vis analysis. The coating morphology and thickness were also investigated by SEM. Hydrophilicity of coatings was determined by measuring...
Article Mechanics and Industry ; Volume 16, Issue 2 , 2015 ; 22577777 (ISSN) ; Elyasi, S ; Mollazadeh, M ; Sharif University of Technology
EDP Sciences 2015
Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demonstrated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation,...
Vanadium dioxide-anchored porous carbon nanofibers as a Na+ intercalation pseudocapacitance material for development of flexible and super light electrochemical energy storage systems, Article Applied Materials Today ; Volume 10 , 2018 , Pages 72-85 ; 23529407 (ISSN) ; Shahrokhian, S ; Sharif University of Technology
Elsevier Ltd 2018
The development of a flexible binder free electrode based on 3D vanadium dioxide (VO2) nano-architectures has materialized as an effective strategy for fabrication of advanced wearable, portable, and stretchable electronic devices. However, most of the stretchable energy storage devices based on VO2 suffer from a relatively low operating voltage, high weight, low specific capacitance, and thus low energy density. Here, a novel binder free supercapacitor electrode composed of hierarchical VO2 nanosheet arrays grown on porous carbon nanofibers (VO2@PCNFs) is designed using a simple hydrothermal method followed by annealing treatment. The electrochemical evaluation confirmed that the energy...
Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 1-7 ; 09215093 (ISSN) ; Rassizadehghani, J ; Asgari, S ; Sharif University of Technology
Tensile and room temperature Charpy V-notch impact tests along with microstructural studies were used to evaluate the variations in the as-cast mechanical properties of low-carbon steels with and without vanadium and niobium. Tensile test results indicate that good combinations of strength and ductility can be achieved by microalloying additions. While the yield strength and UTS increase up to respectively 370-380 and 540-580 MPa in the microalloyed heats, their total elongation range from 20 to 25%. TEM studies revealed that random and interphase fine-scale microalloy precipitates play a major role in the strengthening of the microalloyed heats. On the other hand, microalloying additions...
In situ growth of vanadia-titania nano/micro-porous layers with enhanced photocatalytic performance by micro-arc oxidation, Article Electrochimica Acta ; Volume 55, Issue 9 , 2010 , Pages 3093-3102 ; 00134686 (ISSN) ; Moshfegh, A. Z ; Golestani Fard, F ; Sharif University of Technology
Micro-arc oxidation process was used to synthesize V2O5-TiO2 porous layers for the first time. Surface morphology and topography of the layers were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were also employed to evaluate phase structure and chemical composition of the layers. It was found that the V2O5-TiO2 layers consisted of anatase, rutile, and vanadium pentoxide phases fraction of which varied with the applied voltage and the electrolyte concentration. It was also revealed that pore size and surface roughness increased with the applied voltage and the electrolyte...
Article Applied Surface Science ; Volume 256, Issue 9 , 2010 , Pages 2903-2909 ; 01694332 (ISSN) ; Moshfegh, A. Z ; Golestani Fard, F ; Sharif University of Technology
V2O5-TiO2 layers with a sheet-like morphology were synthesized by micro arc oxidation process for the first time. Surface morphology and topography of the layers were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). Phase structure and chemical composition of the layers were also studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. It was revealed that the composite layers had a sheet-like structure average thickness of which was about 100 nm depending on the applied voltage. The layers consisted of anatase, rutile, and vanadium pentoxide phases fractions of which varied with the applied voltage. The optical properties...
Article Optik ; Volume 127, Issue 11 , 2016 , Pages 4615-4620 ; 00304026 (ISSN) ; Faez, R ; Moreno, E ; Rasouli, F ; Radfar, F ; Zaimbashi, M ; Sharif University of Technology
In this paper characteristics of a linear, 6H-SiC photoconductive semiconductor switch are presented. The vanadium-doped semi-insulated 6H-SiC PCSS device is designed in a back-triggered, radial switch structure. For this purpose, three-dimensional (3D) device modeling tool was used to model and test the optically initiated 6H-SiC switch. Dark I-V characteristic results show that newly proposed rear-illuminated radial switch structure extends the blocking voltage by reducing the peak electric fields near electrodes. Also this radial structure has higher dark resistance as compared to the previous 6H-SiC PCSS experimental results. The ON-state characteristics of vanadium compensated 6H-SiC...
Extraction of molybdenum (VI) and vanadium (V) from nitrate solutions using coupling of acid and solvating extractants, Article International Journal of Engineering, Transactions A: Basics ; Volume 32, Issue 10 , 2019 , Pages 1366-1371 ; 17281431 (ISSN) ; Torab Mostaedi, M ; Outokesh, M ; Asadollahzadeh, M ; Sharif University of Technology
Materials and Energy Research Center 2019
In this study, solvent extraction method has been utilized for separation of molybdenum and vanadium from nitrate solution by utilizing coupling of acid and solvating extractants (D2EHPA and TBP extractants). The outcomes demonstrated that synergistic solvent extraction improves stability of formatted complexes for transfer to the organic phase. The main parameters such as pH value, concentration of extractants, NH4OH concentration as the stripping agent and contact time were optimized at 0.4, 15% (v/v) D2EHPA, 10% (v/v) TBP, 2 M and 30 min, respectively. The maximum separation factor of 24.84 was obtained with a new synergistic mixture of D2EHPA and TBP diluted with kerosene. According to...
M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad
In the present work, aluminothermic reduction of vanadium pentoxide have been used to produce aluminium vanadium alloys. The effect of addition of lime and excess aluminium on the produced alloy was studied. The experiments were carried out in air and in argon. The alloys microstructure were analyzed bu light and scanning electron microscopy. Other methods such as XRD, XRF, ICP, AAS and titration were employed to analyzed the alloy and the slag. It was found that the addition of lime and excess aluminium increase the yield of the alloy. Vanadium recovery was not affected by the atmosphere used.
M.Sc. Thesis Sharif University of Technology ; Roosta Azad, Reza ; Safdari, Jaber ; Firouzzare, Mohammad Ali
In this work bioleaching of vanadium has been done from Saghand Ore (Anomaly II). Leaching of vanadium was done in several stages. First, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxxidans were used for dissolution of pure vanadium pentoxide and it was observed that these bacteria are able to dissolve and reduce vanadium with high efficiency. After that these bacteria were employed to leaching of vanadium from ore; however there were no results by those experiments and no vanadium dissolved in liquor although bacterial activity was visible. In the second stage, oxalic acid 0.1 M as an organic acid and three inorganic acids, namely sulfuric, hydrochloridric and nitric acids, in...
One step electrodeposition of V2O5/polypyrrole/graphene oxide ternary nanocomposite for preparation of a high performance supercapacitor, Article International Journal of Hydrogen Energy ; Volume 42, Issue 33 , 2017 , Pages 21073-21085 ; 03603199 (ISSN) ; Shahrokhian, S ; Iraji zad, A ; Sharif University of Technology
A new ternary nanocomposite based on graphene oxide (GO), polypyrrole (PPy) and vanadium pentoxide (V2O5) is obtained via one-step electrochemical deposition process. Electrochemical deposition of V2O5, PPy and GO on a stainless steel (SS) substrate is conducted from an aqueous solution containing vanadyl acetate, pyrrole and GO to get V2O5/PPy/GO nanocomposite. Characterization of the electrode material is carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The electrochemical performance of the as-prepared nanocomposite is evaluated by...
Synthetic study of symmetrical and unsymmetrical schiff base complexes of VO(IV) and Mn(III) derived from 2,2′-diaminobiphenyl, Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 35, Issue 4 , 2005 , Pages 261-267 ; 15533174 (ISSN) ; Behzad, M ; Sharif University of Technology
The symmetrical and unsymmetrical Schiff base complexes of VO(IV) and Mn(III) derived from 2,2′-diaminobiphenyl and derivatives of salicylaldehyde and 1-hydroxy-2-napnthaldehyde have been synthesized and characterized by elemental analysis, NMR, infrared and electronic absorption spectroscopies, and conductivity measurements. The reaction of the ligands with oxovanadium(IV) was found to be kinetically unfavored, probably due to the small ionic radius of the metal ion, which is not in accordance with the cavity size of the ligands. Copyright © 2005 Taylor & Francis, Inc