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Nickel Nano Particles Pulse Electrodeposition
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Syntheses of coats including nickel nano-particles by electrodeposition have been
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode...
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode...
Study of CdS thin Film Deposition on Single Layer Grapheme using Close Space Sublimation and SILAR Methods
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Cadmium sulfide (CdS) thin films were successfully fabricated in argon atmosphere on glass slides and Single Layer Graphene(SLG)/Cu foil stack by close space sublimation technique in three different deposition temperatures. Successive Ionic Layer Adsorption and Reaction (SILAR) technique is used as a complementary technique for better and denser layers. Analysis techniques such as Grazing Incident X-ray Diffraction (GIXRD) and Scanning Electron Microscope images were used for structural study of the deposited layers. Polycrystallinity and hexagonal wurtzite structure of the thin films is confirmed. For band gap calculations and for determination of optical behavior of the layers in different...
Investigation on Electrical Properties and Band Structure of Barium Strontium Titanate Thin Films Grown by Pulsed Laser Deposition
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Mahdavi, Mohammad (Co-Advisor)
Abstract
In this research the microstructural, electrical and optical properties of Strontium Titanate and Barium Strontium Titante thin films, fabricated through Pulsed Laser Deposition (PLD), were investigated. X-ray Photoelectron Spectroscopy and X-ray Diffraction study showed that the stoichiometry of the target material was highly preserved by using PLD method. Scanning Electon Microscopy as well as Atomic Force Microscopy depicted that the using of pressed and sintered target is a suitable metod for improving the surface quality of the thin films. Using the pressed target decreased the quality of the thin films and the average roughness of the films increased. The main reason for this...
XPS study of size effects of Fe3O4 nanoparticles on crosslinking degree of magnetic TFN membrane
, Article Polymer Testing ; Volume 73 , 2019 , Pages 232-241 ; 01429418 (ISSN) ; Poursalehi, R ; Wiesner, M ; Mousavi, S. A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The control of thin film nanocomposite (TFN) membranes cross-linking degree is an important factor to design new membranes and optimizing permeation characteristics. The Fe3O4 nanoparticle's based TFN membranes due to potentially added magnetic responsive properties to the membrane has a great importance in developing membrane architectures. Fe3O4/polyamide (PA) TFN membranes filled with nanoparticles in different sizes and concentrations have been synthesized. Cross-linking degree of PA layer characterized with Fourier transform spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) methods to evaluate size dependency of the cross-linking degree of PA layer network. Obvious...
Visible light-induced photocatalytic reduction of graphene oxide by tungsten oxide thin films
, Article Applied Surface Science ; Volume 276 , 2013 , Pages 628-634 ; 01694332 (ISSN) ; Akhavan, O ; Sharif University of Technology
2013
Abstract
Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten...
The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au-Ag:SiO2 thin films
, Article Journal of Alloys and Compounds ; Volume 486, Issue 1-2 , 2009 , Pages 22-28 ; 09258388 (ISSN) ; Akhavan, O ; Zaker Moshfegh, A. R ; Sharif University of Technology
2009
Abstract
Gold-silver alloy nanoparticles with various Au concentrations in sputtered SiO2 thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H2 atmosphere at different temperatures. The UV-visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au-Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing...
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...
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...
Structural ordering, morphology and optical properties of amorphous AlxIn1- xN thin films grown by plasma-assisted dual source reactive evaporation
, Article Journal of Alloys and Compounds ; Volume 632 , May , 2015 , Pages 741-747 ; 09258388 (ISSN) ; Ganesh, V ; Mehdipour, H ; Nazarudin, N. F. F ; Goh, B. T ; Shuhaimi, A ; Rahman, S. A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Amorphous aluminum indium nitride (AlxIn1- xN) thin films were deposited on quartz substrates by plasma-assisted dual source reactive evaporation system. In-rich (x = 0.10 and 0.18) and Al-rich (x = 0.60 and 0.64) films were prepared by simply varying an AC voltage applied to indium wire. The X-ray-diffraction patterns revealed a small broad peak assigned to Al0.10In0.90N (0 0 2) plane, but no perceivable peaks assigned to crystalline AlxIn1- xN were observed for the films with x = 0.18, 0.60 and 0.64. The morphology of the film was changed from clusters of small grains to uniformly shaped particles with decrease of x. The band gap energy of the films increased from 1.08 eV to 2.50 eV as the...
Plasma surface functionalization of boron nitride nano-sheets
, Article Diamond and Related Materials ; Volume 77 , 2017 , Pages 110-115 ; 09259635 (ISSN) ; Achour, A ; Solaymani, S ; Islam, M ; Vizireanu, S ; Arman, A ; Ahmadpourian, A ; Dinescu, G ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
On silicon substrates, boron nitride nanosheets (BNNS) consisting of interconnected hexagonal boron nitride nano-layers were produced via chemical vapor deposition process at 1200 °C whose roughness's are at the micrometer- and nanometer-scale. The BNNS were functionalized in argon plasma admixed with ammonia or nitrogen or oxygen. The samples were characterized to investigate the surface chemistry and structural changes after plasma treatment using X-ray photoelectron spectroscope and Micro-Raman spectroscope techniques, respectively. While no significant changes in the surface features, upon plasma treatments of the BNNS, were noticed during SEM and TEM examination, the oxygen functional...
Photoresponse and H2 production of topographically controlled PEG assisted Sol-gel WO3 nanocrystalline thin films
, Article International Journal of Hydrogen Energy ; Volume 36, Issue 21 , October , 2011 , Pages 13461-13472 ; 03603199 (ISSN) ; Yousefzadeh, S ; Daryaei, E ; Moshfegh, A. Z ; Sharif University of Technology
2011
Abstract
WO3 thin films were fabricated by sol-gel method using polyethylene glycol (PEG) as dispersing agent. Physical and photoelectrochemical properties of the synthesized nanocrystalline films were studied by varying weight ratio of PEG to tungsten precursor (x). Based on AFM observations and statistical modeling of the WO3 surface, the thickness of the films increased by increasing the amount of x with a nearly linear fashion while the surface roughness reached to a saturated value. However, the film synthesized with x = 4 showed a chaotic surface behavior. Optical analysis revealed that by increasing the x, transmittance of the films decreased while their band gap energies remained unchanged....
Pd doped WO3 films prepared by sol-gel process for hydrogen sensing
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 2 , 2010 , Pages 854-860 ; 03603199 (ISSN) ; Iraji zad, A ; Rahimi, F ; Ghasempour, R ; Sharif University of Technology
Abstract
The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride salt was dissolved in the sol with different Pd:W molar ratios and coated on Al2O3 substrates by spin coating method. XRD and XPS techniques were used to analyze the crystal structure and chemical composition of the films before and after heat treatment at 500 °C. We observed that Pd can modify the growth kinetic of tungsten trioxide nanoparticles by reducing the crystallite size and as a result can improve hydrogen sensitivity. Resistance-sensing measurements indicated sensitivity of about 2.5 × 104 at room temperature in hydrogen concentration of 0.1% in air. Considering all sensing parameters,...
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...
Micro-arc oxidized S-TiO2 nanoporous layers: Cationic or anionic doping?
, Article Materials Letters ; Volume 64, Issue 20 , 2010 , Pages 2215-2218 ; 0167577X (ISSN) ; Moshfegh, A. Z ; Golestani Fard, F ; Sharif University of Technology
2010
Abstract
S-doped TiO2 layers were grown on titanium substrates by MAO process. SEM results revealed a porous morphology with a pore size of 40-100 nm. Our XRD analysis showed that the anatase relative content reached its maximum value at the voltage of 500 V. The existence of sulfur in the states of S 4+ and S6+ which substituted Ti4+ in the titania crystalline lattice was confirmed by XPS results; meanwhile, no S 2- was detected. That is, a cationic doping was observed. EDS results showed that sulfur concentration in the layers increased with the voltage. The band gap energy was also calculated as 2.29 eV employing a UV-Vis spectrophotometer
Micro arc oxidation of nano-crystalline Ag-doped TiO2 semiconductors
, Article Materials Letters ; Volume 65, Issue 5 , March , 2011 , Pages 840-842 ; 0167577X (ISSN) ; Aminzare, M ; Molaei, R ; Sadrnezhaad, S. K ; Sharif University of Technology
2011
Abstract
Simple synthesis of silver doped TiO2 nanostructured layers by micro arc oxidation process is reported for the first time. The layers consisted of anatase and rutile phases whose characteristic XRD-peaks shifted toward lower diffraction angles when compared to the pure micro arc oxidized TiO 2 layers. Silver-doping was confirmed by XPS technique. The anatase phase crystalline size was determined as 27.6 and 21.8 nm for the layers grown under the voltages of 350 and 500 V. Employing a UV-Vis spectrophotometer, a red shift in the absorption edge of the layers was observed when silver was incorporated into the titania lattice
Melatonin as a powerful bio-antioxidant for reduction of graphene oxide
, Article Journal of Materials Chemistry ; Volume 21, Issue 29 , 2011 , Pages 10907-10914 ; 09599428 (ISSN) ; Akhavan, O ; Irajizad, A ; Sharif University of Technology
2011
Abstract
Graphene is usually synthesized through deoxygenation of graphene oxide (GO) by hydrazine as the most common and one of the strongest reducing agents. But, due to the high toxicity of hydrazine, it is not a promising reductant in large-scale production of graphene. Here, for the first time, we used melatonin (MLT), as a powerful antioxidant and a biocompatible competitor of hydrazine in reduction of GO suspension. X-ray photoelectron spectroscopy (XPS), current-voltage and optical characteristics of the sheets indicated that the deoxygenation efficiency of the GO suspensions by MLT and under heating in an alkaline condition for 3 h was comparable with the efficiency obtained by hydrazine in...
Low temperature self-agglomeration of metallic Ag nanoparticles on silica sol-gel thin films
, Article Journal of Physics D: Applied Physics ; Volume 41, Issue 19 , 2008 ; 00223727 (ISSN) ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
2008
Abstract
A facile sol-gel synthesis for self-agglomeration of metallic silver nanoparticles, with fcc crystalline structure, on the silica surface in a low annealing temperature has been introduced. X-ray photoelectron spectroscopy (XPS) revealed initial agglomeration (∼30 times greater than the nominal concentration of Ag) of the nanoparticles on the surface of the dried film (100 °C) and also their oxidation as well as easy diffusion (with 0.08 eV required activation energy) into the porous silica thin films, by increasing the annealing temperature (200-400 °C). By raising the Ag concentration from 0.2 to 1.6 mol% in the sol, the average size of the Ag nanoparticles increased from ∼5 to 37 nm...
Investigation of Tabas anthracite coal devolatilization: Kinetics, char structure and major evolved species
, Article Thermochimica Acta ; Volume 654 , 2017 , Pages 74-80 ; 00406031 (ISSN) ; Askari, M ; Fabritius, T ; Sharif University of Technology
Elsevier B.V
2017
Abstract
The pyrolysis of low-volatile Tabas anthracite coal was investigated by thermogravimetric technique (TGA) in the temperature range from ambient to 1100 °C under non-isothermal heating conditions (1.5, 3, and 7 °C/min heating rates). Higher heating rates showed a small retarding effect on devolatilization toward higher temperatures. Iso-conversional method was used for the kinetic study of non-isothermal Thermogravimetric data. Activation energy calculated for coal conversion of 20–80% was about 319 kJ/mol which may be a result of stable ordered structure of this type of coal. Analysis of evolved gases by Fourier transform infrared spectrometry (FTIR) in 7 °C/min heating rate was conducted...
Improved electrochromical properties of sol-gel WO3 thin films by doping gold nanocrystals
, Article Thin Solid Films ; Volume 518, Issue 8 , 2010 , Pages 2250-2257 ; 00406090 (ISSN) ; Azimirad, R ; Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
2010
Abstract
In this investigation, the effect of gold nanocrystals on the electrochromical properties of sol-gel Au doped WO3 thin films has been studied. The Au-WO3 thin films were dip-coated on both glass and indium tin oxide coated conducting glass substrates with various gold concentrations of 0, 3.2 and 6.4 mol%. Optical properties of the samples were studied by UV-visible spectrophotometry in a range of 300-1100 nm. The optical density spectra of the films showed the formation of gold nanoparticles in the films. The optical bandgap energy of Au-WO3 films decreased with increasing the Au concentration. Crystalline structure of the doped films was investigated by X-ray diffractometry, which...
Hydrogen sensor based on surface activated WO3 films by Pd nanoclusters
, Article World Academy of Science, Engineering and Technology ; Volume 76 , 2011 , Pages 639-642 ; 2010376X (ISSN) ; Zad, A. I ; Mahdavi, S. M ; Sharif University of Technology
2011
Abstract
Tungsten trioxide has been prepared by using P-PTA as a precursor on alumina substrates by spin coating method. Palladium introduced on WO 3 film via electrolysis deposition by using palladium chloride as catalytic precursor. The catalytic precursor was introduced on the series of films with different morphologies. X-ray diffractometry (XRD), Scanning electron microscopy (SEM) and XPS were applied to analyze structure and morphology of the fabricated thin films. Then we measured variation of samples' electrical conductivity of pure and Pd added films in air and diluted hydrogen. Addition of Pd resulted in a remarkable improvement of the hydrogen sensing properties of WO 3 by detection of...