Loading...
Search for:
dipping
0.007 seconds
Total 68 records
, M.Sc. Thesis Sharif University of Technology ; Moshfegh, Ali Reza (Supervisor) ; Akhavan, Omid (Supervisor)
Abstract
In photocatalitic activity of titana an effective approach to achieve high charge separation efficiency and high level of sensitivity under visible light is coupling it with another semiconductor with smaller band gap and appropriate banding energy structure. achieving all mentioned above, we used bilayer structure and coupled TiO2 with hematite which its small band gap(Eg ~ 2.1 ev) is sensitive to visible light. Bilayer systems of TiO2/Fe2O3 , Fe2O3/TiO2 were fabricated by sol-gel process and variable parameter was upper layer thickness. The layers were deposited on glass substrate via sol-gel process. The upper layers were prepared in different thicknesses in two ways. First, they...
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 (Supervisor)
Abstract
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...
Effect of content silver and heat treatment temperature on morphological, optical, and electrical properties of ITO films by sol-gel technique
, Article Journal of Nanoparticle Research ; Volume 16, Issue 9 , September , 2014 ; ISSN: 13880764 ; Dolati, A ; Sharif University of Technology
Abstract
Silver-doped indium tin oxide thin films were synthesized using sol-gel dip-coating technique. The influence of different silver-dopant contents and annealing temperature on the electrical, optical, structural, and morphological properties of the films were characterized by means of four-point probe, UV-Vis spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscope (XPS). XRD analysis confirmed the formation of cubic bixbyte structure of In2O3with silver nanoparticles annealed at 350 °C. XPS analysis showed that divalent tin transformed to tetravalent tin through oxidization, and silver nanoparticles embedded into ITO...
An analytical study for low voltage ride through of the brushless doubly-fed induction generator during asymmetrical voltage dips
, Article Renewable Energy ; Volume 115 , 2018 , Pages 64-75 ; 09601481 (ISSN) ; Oraee, A ; Tohidi, S ; Oraee, H ; McMahon, R. A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The Brushless Doubly-fed Induction Generator (BDFIG) has high potential for wind energy systems, especially for offshore applications where minimum maintenance is vital. The machine low voltage ride through (LVRT) capability in the light of current grid code requirements was investigated using a precise dynamic model. This is particularly important for future multi- MW BDFIGs. This paper shows the necessity for improvements of the BDFIG LVRT capability with presenting a comprehensive analytical study during asymmetrical voltage dips. Analytical studies are conducted to extract a more precise equivalent circuit model of the BDFIG used for analyzing machine dynamic behavior under various fault...
Fabrication of Mn/Co and Co Coatings on AISI 430 for SOFC Interconnect Via Sol-Gel and Dip Coating
, M.Sc. Thesis Sharif University of Technology ; Askari, Masoud (Supervisor)
Abstract
With regard to recent progress in decreasing of operating temperature of Solid Oxide Fuel Cell (SOFC), metallic interconnect use widely than ceramic interconnect. Metallic interconnect have interested due to their low cost, easy fabrication and high electronic and thermal conductivity.oxidation resistance of metals is big challenge, because of low conductivity of formed oxide layers that led to increasing of electrical conductivity. Ferritic stainless steel is among the most thriving candidate alloy because of BCC structure that its coefficient of temperature expansion is close to that of other SOFC. Nonetheless, the increase of electrical resistance over the time and the evaporation of...
Numerical Analysis of Failure Mechanisms in Saw-Tooth and Natural Joints of Rock Mass Under Shear
, M.Sc. Thesis Sharif University of Technology ; Sedghiani, Mohammad Hossein (Supervisor)
Abstract
Needs for construction of rock structures and underground ones such as underground tunnels, dam foundations, trenches for roads and railways, power plants and caverns built to keep oil, gas and nuclear waste has increased dramatically. In order to design, construct and excavate these underground structures safely and economically, full understanding of rock mass properties, suitable tools and practical techniques of drilling are necessary. Because of existing discontinuities, including joints and layered rock masses and their effects on mechanical behavior of rock mass, it is necessary for the geo-mechanical profile, shear strength and failure mechanism of rock mass to be accurately...
Low voltage ride-through of DFIG and brushless DFIG: Similarities and differences
, Article Electric Power Systems Research ; Vol. 110 , May , 2014 , p. 64-72 ; ISSN: 03787796 ; Tavner, P ; McMahon, R ; Oraee, H ; Zolghadri, M. R ; Shao, S ; Abdi, E ; Sharif University of Technology
Abstract
The brushless doubly fed induction generator (BDFIG) has been proposed as a viable alternative in wind turbines to the commonly used doubly fed induction generator (DFIG). The BDFIG retains the benefits of the DFIG, i.e. variable speed operation with a partially rated converter, but without the use of brush gear and slip rings, thereby conferring enhanced reliability. As low voltage ride-through (LVRT) performance of the DFIG-based wind turbine is well understood, this paper aims to analyze LVRT behavior of the BDFIG-based wind turbine in a similar way. In order to achieve this goal, the equivalence between their two-axis model parameters is investigated. The variation of flux linkages,...
Feasibility Study of Painting Line by Electro Deposition in Zagrosskhodro
,
M.Sc. Thesis
Sharif University of Technology
;
Hooshmand, Mahmoud
(Supervisor)
Abstract
Assurance about projects and industrial plans success always had been one of the most important concerns of investors. Car manufacturing industry is not excluded. In this project the painting line in zagrosskhodro company using electro deposition method is reviewed , analyzed, and investment feasibility study of such method is investigated . All aspect of investment including financial and economic aspect is reviewed by UNIDO methodology.
The outcome is described here briefly.
1- Production volume in this plan in complete capacity is equal to 40000 bodies in a year.
2- The primary fixed investment capital is 132,187,912,140 Rls.
3- Sum of fixed expenses of production is ...
The outcome is described here briefly.
1- Production volume in this plan in complete capacity is equal to 40000 bodies in a year.
2- The primary fixed investment capital is 132,187,912,140 Rls.
3- Sum of fixed expenses of production is ...
Lanthanum Chromite Coating on Stainless Steel by sol–Gel Dip Coating Technique
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Because of the high operating temperature, interconnect surface tends to be oxidized and Cr2O3 oxide layer will be created on the surface. This phenomenon is undesirable due to decreasing electrical conductivity, so a preservative coating is needed to improve the interconnect properties. In this paper, a dense perovskite thin film was successfully synthesized on a ferritic stainless steel (type 430) substrate by a sol-gel dip coating method. This coating improved chemical stability, oxidation behavior of the substrate and decreased cathode poisoning. The lanthanum chromite was coated on the substrate by sol-gel dip coating process. First, during a hydrolyze process, a stable sol was made up...
Preparation and Stabilizing Graphene Sheets for Gas Sensing Application
, M.Sc. Thesis Sharif University of Technology ; Iraji zad, Azam (Supervisor)
Abstract
Graphene is one of the most attractive subjects for scientists in the last decade. Its unique properties has been probed by many research groups and innumerable projects have been developed to investigate applications of graphene in electronics, mechanics, biophysics etc. Due to high surface to volume ratio and magnificent electron mobility in graphene, it is a suitable candidate for gas sensing. This has been proved by several theoretical and experimental researches for various gases such as CO, NH3 and NO2 etc. In present thesis, graphene has been prepared chemically and transferred to silicone substrates that are previously coated with a 300 nanometer silicone dioxide layer, by dip...
BiFeO3 Thin Films Deposition by Sol-Gel and Dip Coating Process
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Alizadeh, Masoud (Supervisor)
Abstract
Dark and light conductivity has been investigated in Ca-doped bismuth ferrite thin films. Higher conductivity in the order of 105 magnitude of pure Bismuth ferrite has been observed for Bi0.85Ca0.15FeO3-δ. Structural analysis using Rietveld refinement showed a deviation from volume reduction for Bi0.85Ca0.15FeO3-δ that could be the reason of the abnormally high conductivity for this compound. Although higher calcium doping reduced conductivity but photoresponse could be revived. Atomic Forec Microscopy investigations showed that surface roughness decreases with increasing calcium concentration. Enhanced photoconductivity is reported for Bi0.7Ca0.3FeO3-δ with ~2.9 eV direct optical band gap...
Preparation and Characterization of ZrO2 Antistatic Coatings on Glass
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor) ; Afshar, Abdollah (Supervisor)
Abstract
In this study, the zirconia antistatic coating was synthesized by dip coating sol-gel route on glass substrate. The solution contains ZrCl4 as precursor and isopropanol as solvent to synthesize zirconium oxide. The effects of environmental humidity and solution concentration on the coating characterization were analyzed. MPTS and primer binder were added as binding agents in the solution to observe the effect of binding agents on the coating adhesion. Solution stability and antistatic coating characterization were analyzed by zita potential test, FTIR spectroscopy, EDX analysis, FESEM and AFM microscopy, pencil hardness test, thickness test, antidust ability and spectrophotometer. The...
YSZ Coating on Ferritic Stainless Steel Interconnect through Sol-Gel Method and Studying its Reaction with Glass Sealant in SOFC
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor) ; Nemati, Ali (Supervisor)
Abstract
Solid oxide fuel cells are used to convert solid-state energy to direct electrical current by electrochemistry mixing a gas fuel and an oxidant in an oxide electrolyte. One of the most interesting aspects of this field for the researchers is the reaction between the metal interconnect and the glass sealant. In the current research, deposition of the YSZ coating onto the metal interconnect in order to impede the reaction with glass sealant and prohibition of its oxidation in oxidizing/reducing environment in high temperature, was mainly investigated. Effect of applying YSZ Thin layer in the intersection of Crofer steel and glass sealant on strength and chemical durability of these two...
H2S Gas Sensing Characterization of Nano-Structured SnO2-CuO Multilayer Sensor
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Co-Advisor)
Abstract
Hydrogen sulfide, H2S, is a toxic gas and has detrimental effects on human health and the oil and gas industry. Therefore, its identification is very important. According to the devastating effects of this gas, then, the general mechanisms have been studied for gas detection. In addition, by highlighting the benefits of the multilayer nanostructure electrochemical sensors, an applicable and efficient method for the industrial production of these sensors has been investigated. In this regard, the sol-gel method is used to prepare the SnO2-CuO multilayer thin film and the advantages of this method was compared to PVD method. Also sensor properties of both deposition methods have been...
Design and Implement a High Voltage Switching DC Power Supply Based on Voltage Multiplier for High Regulation and Controllable Output Voltage
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High DC voltage is widely used in many applications such as X-Ray machines ,CRT , photocopy machines and etc. One idea to produce this high DC voltage is to use transformers, but it will be large in volume. We can increase frequency to reduce the volume of transformers but high voltage of primary and secondary winding will limited this volume reduction. Furthermore high turn ratio in transformers increases non idealities that cause voltage and current spike, and increase loss and noise. The main goal of this thesis is to reduce differential mode voltages on transformers to reduce the volume of power supply. Voltage multiplier will be used to reduce differential mode voltage. Voltage...
Low voltage ride-through capability improvement of DFIG-based wind turbines under unbalanced voltage dips
, Article International Journal of Electrical Power and Energy Systems ; Vol. 60,Issue , 2014 , pp. 82-95 ; ISSN: 01420615 ; Parniani, M ; Sharif University of Technology
Abstract
This paper proposes a competent and effective scheme to enhance the ride-through capability of DFIG-based wind turbines under unbalanced voltage dip conditions. The proposed method is realized through joint use of the rotor-side converter control and a three-phase stator damping resistor (SDR) placed in series with the stator windings. By means of an asymmetrical SDR idea, during the unbalanced voltage dip the SDR resistors are activated only in phase(s) experiencing low voltage. Then, the rotor current is controlled such that no unbalance voltage appears on the stator voltage. The proposed ride-through approach limits the peak values of the rotor inrush current, electromagnetic torque and...
Characterization and photocatalytic activities of nanosized titanium dioxide thin films
, Article International Journal of Environmental Science and Technology ; Volume 8, Issue 3 , 2011 , Pages 545-552 ; 17351472 (ISSN) ; Rashidzadeh, M ; Nemati, A ; Irandoukht, A ; Faridnia, B ; Sharif University of Technology
2011
Abstract
Thin films of titanium dioxide with high surface area are prepared by sol-gel dip-coating technique. In this regards, Titania nano sols with high photocatalytic activity were prepared by dissolving titanium alkoxide in alcohol and water under acidic conditions. Photocatalytic activities of titanium dioxide thin films were measured in the presence of methylene blue. Microstructure and photocatalytic activity of the films, nanopowders and titanium dioxide sols were investigated using X-ray diffraction, scanning electron microscopy, specific surface area, zeta sizer and ultraviolet-visible spectrometry techniques. Particle size analysis of sols showed that the mean particle sizes were 15 to 128...
Enhancing seebeck coefficient and electrical conductivity of polyaniline/carbon nanotube–coated thermoelectric fabric
, Article Journal of Industrial Textiles ; 2021 ; 15280837 (ISSN) ; Ramazani Saadatabadi, A ; Pourjahanbakhsh, M ; Siadati, M. H ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the...
Protection of titanium metal by nanohydroxyapatite coating with zirconia and alumina second phases
, Article Protection of Metals and Physical Chemistry of Surfaces ; Volume 48, Issue 6 , 2012 , Pages 688-691 ; 20702051 (ISSN) ; Solati Hashjin, M ; Nik, S. N ; Nemati, A ; Sharif Universty of Technology
2012
Abstract
In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD)....
Pre-treatment and oxidation behavior of sol-gel Co coating on 430 steel in 750°C air with thermal cycling
, Article Surface and Coatings Technology ; Volume 206, Issue 16 , 2012 , Pages 3495-3500 ; 02578972 (ISSN) ; Askari, M ; Gannon, P ; Sharif University of Technology
2012
Abstract
Research and development efforts continue to improve oxidation resistance and electrical conductivity of solid oxide fuel cell (SOFC) interconnects. This research evaluates the performance of a ferritic stainless steel (AISI 430 - a candidate SOFC interconnect material) with and without a Co coating (via sol-gel dip coating technique) with various pre-treatments, during cyclic oxidation exposures up to 750°C in laboratory air. A pre-treatment exposure of Co coated samples to a 750°C reducing atmosphere (prior to oxidation exposures) led to the formation of an effective Co-based spinel oxide coating that lowers oxidation rates by more than 40 times, and substantially lowers area specific...