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A two step Microwave-assisted coke resistant mesoporous Ni-Co catalyst for methane steam reforming
, Article Fuel ; Volume 317 , 2022 ; 00162361 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Methane steam reforming (MSR) is an assuring reaction using steam to produce H2 as clean energy over a nicκel-based catalyst. We synthesized mesoporous monometallic NiMgAl2O4 and bimetallic NiCoMgAl2O4 catalysts in a two-step combustion method using a mix of fuels and powder metallurgy. BET-BJH, XRD, TGA, TPR, FESEM, and EDX-mapping characterized surface area, porosity, morphology, crystalline structure, and metal-support interaction behavior. The products exhibited strong interaction of well-structured MgAl2O4 spinel with NiO, in both specimens. The MSR evaluation tests at 750 °C under atmospheric pressure, CH4:H2O feed ratio of 1:1.2 showed the bimetallic catalyst has the highest...
Preparation and characterization of visible light sensitive nano titanium dioxide photocatalyst
, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1626-1631 ; 10263098 (ISSN) ; Kazemeini, M ; Fattahi, M ; Sharif University of Technology
2012
Abstract
Dye sensitizers loaded on TiO2 decrease the electron excitation energy, thereby improving the photocatalytic performance by causing an increase in sensitivity under visible light irradiation. Three dye sensitizer precursors, Mordant Orange 1, N3 (red dye) and Cobalt (II) Phthalocyanine Tetrasulfonate (CoPcTs), were utilized to load the photocatalyst. The rate of the electron trapping process on platinum is clearly compatible with the migration rate of boundary electrons. Consequently, the migration of boundary electrons from the conduction band towards electron acceptors is increased by loading platinum onto the titanium dioxide. In this research, TiO2 was synthesized from a titanium...
Synthesis of W17O47 nanothick plates with preferred orientation and their photocatalytic activity
, Article Surface and Interface Analysis ; Volume 43, Issue 11 , 2011 , Pages 1397-1402 ; 01422421 (ISSN) ; Khosravi, P ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
A simple method for synthesis of W17O47 nanothick plates by annealing sol-gel-deposited tungsten oxide thin films on soda lime substrate has been reported. After heat treatment of the dried thin films at 700 °C in N2 ambient for 60 min, W17O47 nanothick plates with [100] orientation were obtained. The synthesized product was characterized and analyzed by, X-ray diffraction (XRD), SEM, XPS and ultraviolet-visible spectrophotometery. According to SEM observations, nanothick plates grew with random orientations on the surface. In addition, it was observed that some of the nanothick plates were constituted from several nanosheets. XRD analysis determined that the nanothick plates were mainly...
Effect of annealing temperature on growth of Ce-ZnO nanocomposite thin films: X-ray photoelectron spectroscopy study
, Article Thin Solid Films ; Volume 520, Issue 2 , November , 2011 , Pages 721-725 ; 00406090 (ISSN) ; Azimirad, R ; Amiri, M ; Moshfegh, A. Z ; Sharif University of Technology
2011
Abstract
Ce-doped ZnO nanocomposite thin films with Ce/Zn ratio fixed at optimum value (10 at.%) have been prepared via sol-gel method at different annealing temperatures varied from 180 to 500 °C. The synthesized samples were characterized employing atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. According to AFM analysis, the average grain size increased from about 70 nm to 150 nm by increasing the annealing temperature from 300 to 500 °C. Moreover, based on the XPS data analysis, it was found that three major metal ions namely Ce 3+, Ce4+, and Zn2+ coexist on the surface of the nanocomposite films. XPS data analysis also revealed that...
A photocatalytic approach in micro arc oxidation of WO3-TiO 2 nano porous semiconductors under pulse current
, Article Materials Chemistry and Physics ; Volume 128, Issue 3 , 2011 , Pages 427-432 ; 02540584 (ISSN) ; Golestani Fard, F ; Moshfegh, A. Z ; Molaei, R ; Sharif University of Technology
2011
Abstract
Since ultraviolet (UV) irradiation cannot be applied for a long time in practical applications, it is necessary to develop a narrow band gap photocatalyst to decompose environmental pollutants under visible irradiation. In this research, (WO3)x-(TiO2)1-x nano-porous layers were fabricated by micro arc oxidation (MAO) and influence of the electrical current type on their physical and chemical properties was investigated. Morphological studies, performed by SEM technique, revealed that pore size and roughness decreased with the frequency and increased with the duty cycle. The pulse-grown layers had a finer structure when compared to those fabricated under direct current. XRD and XPS results...
Factors influencing the preparation of TiO2 nanopowders from titania sol
, Article Ceramics - Silikaty ; Volume 55, Issue 1 , 2011 , Pages 31-35 ; 08625468 (ISSN) ; Rashidzadeh, M ; Nemati, A ; Irandoukht, A ; Sharif University of Technology
2011
Abstract
Titania nanoparticles with high photocatalytic activity were prepared from titanium alkoxide dissolved in alcohol and water under acidic conditions. The effects of the key parameters including (alkoxide/water) ratio, (alkoxide/alcohol) ratio, precursor type, solvent type, type and concentration of stabilizer, calcination temperature, presence of methylcellulose (MC) and hydrothermal treatment were studied. The optimal conditions were obtained through an experimental design technique. This technique is also used to find the main factors influencing the degradation of methylene blue (MB) and mass percent of anatase phase. The powders characteristics were investigated by XRD and...
Synthesis of a nanostructured MgH2-Ti alloy composite for hydrogen storage via combined vacuum arc remelting and mechanical alloying
, Article Materials Letters ; Volume 65, Issue 7 , 2011 , Pages 1120-1122 ; 0167577X (ISSN) ; Kaflou, A ; Simchi, A ; Sharif University of Technology
Abstract
To improve the hydrogen kinetics of magnesium hydride, TiCr 1.2Fe0.6 alloy was prepared by vacuum arc remelting (VAR) and the alloy was co-milled with MgH2 to process nanostructured MgH2-5 at.% TiCr1.2Fe0.6 powder. The hydrogen desorption properties of the composite powder were studied and compared with pure magnesium hydride. X-ray diffraction (XRD) analysis showed that the composite powder prepared by VAR/mechanical alloying (MA) procedure consisted of β-MgH2, γ-MgH2, bcc Ti-Cr-Fe alloy, and small amount of MgO. The average size of particles and their grain structure after 4 h MA were determined by a laser particle size analyzer and XRD method and found to be 194 nm and 11 nm,...
Comparative study of ZnO nanostructures grown on silicon (1 0 0) and oxidized porous silicon substrates with and without Au catalyst by chemical vapor transport and condensation
, Article Journal of Alloys and Compounds ; Volume 509, Issue 11 , March , 2011 , Pages 4295-4299 ; 09258388 (ISSN) ; Dariani, R. S ; Zad, A. I ; Sharif University of Technology
2011
Abstract
ZnO tetrapods and rods were grown on silicon and thermally oxidized porous silicon substrates with and without Au catalyst layer by carbothermal reduction of ZnO powder through chemical vapor transport and condensation method (CVTC). Porous silicon was fabricated by electrochemical etching of silicon in HF solution. The effect of substrates on morphology, structure and photoluminescence spectra of ZnO nanostructures has been studied. The texture coefficient (TC) of each sample was calculated from XRD data that demonstrated random orientation of ZnO nanostructures on the oxidized porous silicon substrate. Moreover, TC indicates the effect of Au catalyst layer on formation of more highly...
Synthesis and electrochemical properties of LiNi0.8Co 0.2O2 nanopowders for lithium ion battery applications
, Article Journal of Power Sources ; Volume 196, Issue 1 , 2011 , Pages 337-342 ; 03787753 (ISSN) ; Asgari, S ; Sharif University of Technology
Abstract
Nitrates of lithium, cobalt and nickel are utilized to synthesize LiNi 0.8Co0.2O2 cathode material through sol-gel technique. Various synthesis parameters such as calcination time and temperature as well as chelating agent are studied to determine the optimized condition for material processing. Using TG/DTA techniques, the optimized calcination temperatures are selected. Different characterization techniques such as ICP, XRD and TEM are employed to characterize the chemical composition, crystal structure, size and morphology of the powders. Micron and nano-sized powders are produced using citric/oxalic and TEA as chelating agent, respectively. Selected powders are used as cathode material...
On the photocatalytic activity of the sulfur doped titania nano-porous films derived via micro-arc oxidation
, Article Applied Catalysis A: General ; Volume 389, Issue 1-2 , 2010 , Pages 60-67 ; 0926860X (ISSN) ; Moshfegh, A. Z ; Golestani Fard, F ; Sharif University of Technology
2010
Abstract
Sulfur doped TiO2 layers containing nano/micro-sized pores were synthesized by micro-arc oxidation process. Effect of the applied voltage and the electrolyte composition on physical and chemical properties of the layers was investigated using SEM, AFM, XRD, XPS, and EDS techniques. A UV-vis spectrophotometer was also used to study optical properties of the layers. It was found that the doped layers were porous with a pore size of 40-170 nm. They consisted of anatase and rutile phases with varying fraction depending on the applied voltage and electrolyte concentration. Our XPS investigations revealed the existence of sulfur in the forms of S4+ and S6+ states which substituted Ti4+ in the...
Investigation of the gas barrier properties of PP/ciay nanocomposite films with EVA as a compatibiliser prepared by the melt intercalation method
, Article Polymer - Plastics Technology and Engineering ; Volume 49, Issue 10 , 2010 , Pages 991-995 ; 03602559 (ISSN) ; Ahmad Ramazani, S. A ; Danaei, M ; Sharif University of Technology
2010
Abstract
In this research, polypropylene (PP) nanocomposite films were prepared by melt intercalation method and their properties have been evaluated. To facilitate the formation of either intercalated or exfoliated nanocomposites, ethylene vinyl acetate copolymer (EVA) was used as a compatibiliser. Morphology of composites was determined by X-ray Diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM analyses confirmed that increasing of EVA content leads to achievement of intercalated nanocomposites. Furthermore, differential scanning calorimetry (DSC) measurement indicated a decrease in crystallinity, melting point and crystallization temperature. Also, permeability tests showed...
Fractional factorial design for the optimization of hydrothermal synthesis of lanthanum oxide nanoparticles under supercritical water condition
, Article Journal of Supercritical Fluids ; Volume 52, Issue 3 , 2010 , Pages 292-297 ; 08968446 (ISSN) ; Abolghasemi, H ; Moosavian, M. A ; Golzary, A ; Ghannadi Maragheh, M ; Sharif University of Technology
2010
Abstract
In this research, synthesis of lanthanum oxide nanoparticles using supercritical water as a reaction medium in batch type reactor was studied. The crystallographic identity and morphology of the synthesized nanoparticles were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate that the well-crystallized lanthanum oxide nanocrystals can be easily obtained under the current synthetic conditions. The effect of four parameters includes temperature, reaction time; primary concentration of aqueous solution of lanthanum (III) nitrate and pH of starting solution on reaction efficiency, particle size and the BET surface area were investigated...
Superhydrophilic stability enhancement of RF co-sputtered TixSi1-xO2 thin films in dark
, Article Applied Surface Science ; Volume 256, Issue 8 , 2010 , Pages 2500-2506 ; 01694332 (ISSN) ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
2010
Abstract
TixSi1-xO2 compound thin-film systems were deposited by reactive RF magnetron co-sputtering technique. The effect of Ti concentration on the hydrophilicity of TixSi1-xO2 compound thin films was studied and it was shown that the films with Ti0.6Si0.4O2 composition possess the best hydrophilic property among all the grown samples. Surface ratio and average roughness of the thin films were measured by atomic force microscopy (AFM). Surface chemical states and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). In addition, XPS revealed that the amount of Ti-O-Si bonds in nanometer depth from the surface of the Ti0.6Si0.4O2 films was the maximum, which resulted...
Phase formation and change of magnetic properties in mechanical alloyed Ni0.5Co0.5Fe2O4 by annealing
, Article Journal of Magnetism and Magnetic Materials ; Volume 322, Issue 1 , 2010 , Pages 56-59 ; 03048853 (ISSN) ; Yoozbashizadeh, H ; Yourdkhani, A ; Mohammadi, M ; Sharif University of Technology
Abstract
The effects of milling time and annealing temperature on phase formation, microstructure and magnetic properties of nickel-cobalt ferrite synthesized from oxide precursors by mechanical alloying were studied. The study of milling time effects on phase formation of milled materials showed that if milling continues up to 55 h, single phase nano-sized nickel-cobalt ferrite is obtained. Also, magnetic properties of powders versus milling time and annealing at different temperatures extensively changed, so that annealing at 1200 °C increased the magnetization saturation of the as-milled powder from 15.1 to 53.6 emu/g. X-ray powder diffraction technique (XRD) with Cu-Ka radiation was employed for...
Effect of operation conditions on the catalytic performance of the Co/Mn/TiO2 catalyst for conversion of synthesis gas to light olefins
, Article Scientia Iranica ; Volume 17, Issue 2 C , November , 2010 , Pages 168-176 ; 10263098 (ISSN) ; Ghotbi, C ; Bozorgmehry Boozarjomehry, R ; Rashtchian, D ; Sharif University of Technology
Abstract
The effect of operation variables, such as the H2/CO molar feed ratio, gas hourly space velocity (GHSV), temperature, and pressure, on the catalytic performance of the Co/Mn/TiO2 catalyst prepared at the Research Institute of the Petroleum Industry (RIPI) was investigated, and optimum reactor conditions were obtained to produce the maximum amount of light olefins. The catalyst was prepared by co-precipitation of Co and Mn phases in the presence of commercial TiO2 with maximum selectivity for ethylene and propylene production. It was found that the [H2]/[CO]=2/1, space velocity (GHSV) of 1800 h-1, 280°C temperature and 4 bar pressure were optimum operating conditions for the modified catalyst...
Microstructural evolution of Al-20Si-5Fe alloy during rapid solidification and hot consolidation
, Article Rare Metals ; Volume 28, Issue 6 , 2009 , Pages 639-645 ; 10010521 (ISSN) ; Vahidi, M ; Simchi, A ; Davami, P ; Sharif University of Technology
Abstract
Al-20Si-5Fe melt was rapidly solidified into particles and ribbons and then consolidated to near full density by hot pressing at 400°C/250 MPa/1 h. According to the eutectic-growth and dendritic-growth velocity models, the solidification front velocity and the amount of undercooling were estimated for the particles with different sizes. Values of 0.43-1.2 cm/s and 15-28 K were obtained. The secondary dendrite arm spacing revealed a cooling rate of 6 × 105 K/s for the particles with an average size of 20 μm. Solidification models for the ribbons yielded a cooling rate of 5 × 107 K/s. As a result of the higher cooling rate, the melt-spun ribbons exhibited considerable microstructural...
Growth and field emission study of molybdenum oxide nanostars
, Article Journal of Physical Chemistry C ; Volume 113, Issue 44 , 2009 , Pages 19298-19304 ; 19327447 (ISSN) ; Azimirad, R ; Zavarian, A. A ; Zaker Moshfegh, A. R ; Sharif University of Technology
2009
Abstract
The field emission properties of MoO2 nanostars grown on a silicon substrate and their emission performance in various vacuum gaps are reported in this article. A new structure of molybdenum oxides, named a nanostar, is grown by thermal vapor deposition with a length of ̃1 μm, a thickness of ̃50 nm, and its width in the range of 500-700 nm. The morphology, structure, composition, and chemical states of the prepared nanostars were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to XRD analysis, the grown nanostructures are composed of both crystalline Mo4O11 and...
ZnO nanoparticles prepared by electrical arc discharge method in water
, Article Materials Chemistry and Physics ; Volume 118, Issue 1 , 2009 , Pages 6-8 ; 02540584 (ISSN) ; Iraji zad, A ; Mahdavi, M ; Ahadian, M. M ; Sharif University of Technology
2009
Abstract
We produced ZnO nanoparticles by high current electrical arc discharge of zinc electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis shows formation of crystalline ZnO phase with hexagonal structure and 14 nm single crystalline domain size. Dynamic light scattering (DLS) result indicates that at 5 A arc current, the size of the particles is about 100 nm and increases by increasing the arc current. Absorption spectroscopy of the samples obtained at different arc currents shows an absorption edge on 370 nm which has a red shift by increasing the arc current. Band gap of the produced ZnO nanoparticles at 5 A arc current corresponds to 3.8 eV which decreases to 3.3 eV by...
Effect of SAPO-34's composition on its physico-chemical properties and deactivation in MTO process
, Article Applied Catalysis A: General ; Volume 364, Issue 1-2 , 2009 , Pages 48-56 ; 0926860X (ISSN) ; Farhadi, F ; Khorasheh, F ; Sahebdelfar, S ; Asadi, M ; Feng, Y. Z ; Sharif University of Technology
2009
Abstract
Several SAPO-34 samples with different Si/Al ratio (0.05-0.5) of synthesis gel were prepared hydrothermally at crystallization temperature of 190-215 °C. The products were characterized by XRD, SEM/EDX, NH3-TPD, FT-IR and nitrogen adsorption techniques. EDX data showed a deviation of elemental composition of products with respect to the Al, Si, and P from that of the gel mixture, but the increasing trend of Si/Al ratio of the products was confirmed. According to XRD and SEM results, crystallinity of samples increased with Si/Al ratio up to the low to medium range of ca. 0.13. However, a reduction in the crystallinity was observed with further increase of the silicon content of the synthesis...
CdO/PSi/Si photo detector
, Article International Journal of Nanotechnology ; Volume 6, Issue 10-11 , 2009 , Pages 997-1005 ; 14757435 (ISSN) ; Iraji zad, A ; Mahdavi, S. M ; Samadpoor, M ; Sharif University of Technology
2009
Abstract
In spite of various works which were carried out on CdO and porous Si (PSi) separately, the interesting properties of CdO/PSi/Si system are not known well. In this work, we study the photoconductivity of deposited CdO layer on PSi/Si system. PS and CdO layers were prepared by electrochemical anodisation of p-type crystalline silicon and pulsed laser deposition (PLD) of cadmium oxide target. Then samples were annealed in air at 500°C to increase their optical transmissions to a value as large as 90% for wavelengths above 700 nm. The XRD study reveals that the annealed films are polycrystalline with grain size of about 25 nm. SEM micrograph of the CdO/PSi/Si system indicates that CdO layer has...