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The effect of microstructure on the photocatalytic properties of TiO2
, Article Advanced Materials Research, 26 October 2009 through 29 October 2009 ; Volume 264-265 , 2011 , Pages 1340-1345 ; 10226680 (ISSN) ; 9783037850534 (ISBN) ; Kianpour Rad, M ; Sadrnezhaad, S. K ; Vaezi, M. R ; Sharif University of Technology
2011
Abstract
Titanium dioxide is a cheap, chemically stable and non-toxic material. However its photocatalytic properties are unstable and it is a modest semiconductor and a mediocre insulator. For several applications it would be interesting to make it either more insulating or more conducting. The goal of this work was to modify the photocatalytic properties of nano-crystalline TiO2 powders by wet chemical routes and hydrothermal methods to understand the mechanism leading to these modifications The principal factors that influence the photocatalytic properties are on the one hand the concentration and nature of the chemical and physical conditions in TiO2, and on the other hand the morphology of the...
The dynamics of wettability driven droplets in smooth and corrugated microchannels
, Article Journal of Statistical Mechanics: Theory and Experiment ; Volume 2012, Issue 10 , 2012 ; 17425468 (ISSN) ; Moosavi, A ; Mazloomi, A ; Sharif University of Technology
IOP
2012
Abstract
A multi-component lattice Boltzmann scheme is used to investigate the dynamics of a wettability driven droplet within a microchannel. The driving force for the motion is created by a stepwise change in the wettability of the channel walls. Moreover, an analytical solution is developed for evaluation of the dynamics of the droplet inside the channel. The effects of various parameters such as the height of the channel, the wetting pattern of the channel walls, the viscosity and the density ratio on the dynamics are studied. Also, the effect of grooves of different sizes on the channel surfaces on the dynamics of the droplet is investigated for both hydrophilic and hydrophobic surfaces....
Synthesis of spherical silica/multiwall carbon nanotubes hybrid nanostructures and investigation of thermal conductivity of related nanofluids
, Article Thermochimica Acta ; Volume 549 , 2012 , Pages 87-94 ; 00406031 (ISSN) ; Rashidi, A ; Rashtchian, D ; Lotfi, R ; Amrollahi, A ; Sharif University of Technology
2012
Abstract
In this study, a hybrid of silica nanosphere/multiwall carbon nanotube (MWCNT) has been synthesized by wet chemical method at room temperature. The effect of MWCNTs, silica nanospheres and hybrid nanostructures (80% silica nanosphere/20% MWCNT and 50% silica nanosphere/50% MWCNT) on the thermal conductivity of distilled water has been investigated. SDBS was used as the dispersant to stabilize nanomaterials in the aqueous suspension and its concentration was 1.5 times of the concentration of nanomaterials. As results show, by increasing the concentration of nanomaterials, effective thermal conductivity of nanofluids increased. The most and the least enhancement in the effective thermal...
Synthesis of Reduced Graphene Oxide-Carbon Nanotubes (rGO-CNT) Composite and Its Use As a Novel Catalyst Support for Hydro-Purification of Crude Terephthalic Acid
, Article Industrial and Engineering Chemistry Research ; Volume 54, Issue 31 , 2015 , Pages 7591-7603 ; 08885885 (ISSN) ; Rashidi, A. M ; Safekordi, A. A ; Aghabozorg, H. R ; Khorasheh, F ; Sharif University of Technology
American Chemical Society
2015
Abstract
Palladium nanocatalysts supported on reduced graphene oxide (rGO), multi walled carbon nanotubes (MWCNT), and rGO/CNT composite were synthesized by a wet impregnation method using PdCl2 as a precursor. Palladium loading was 0.3 wt %, and the catalysts were reduced at 300°C. The catalysts were characterized by inductively coupled plasma, Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, temperatue-programmed reduction, temperatue-programmed desorption, and Raman spectroscopy. The performance of the catalysts was investigated for hydro-purification of crude terephthalic acid (CTA) containing...
Synthesis of dimethyl ether over modified H-mordenite zeolites and bifunctional catalysts composed of Cu/ZnO/ZrO2 and modified H-mordenite zeolite in slurry phase
, Article Catalysis Letters ; Volume 129, Issue 1-2 , 2009 , Pages 111-118 ; 1011372X (ISSN) ; Kazemeini, M ; Aghaziarati, M ; Sharif University of Technology
2009
Abstract
Synthesis of dimethyl ether (DME) via methanol dehydration were investigated over various catalysts, and via direct CO hydrogenation over hybrid catalysts composed of Al-modified H-Mordenite zeolite and Cu/ZnO/ZrO 2. H-Mordenite zeolite exhibited the highest activity in dehydration of methanol. However, its selectivity toward dimethyl ether was rather low. For this reason, the H-Mordenite was modified. Modification of zeolites was performed by wet impregnation method and considered catalysts were characterized by AAS, XRD and NH3-TPD analyses. Results of catalytic tests indicated that H-Mordenite modified with 8 wt% aluminum oxide was the best catalyst for synthesis of dimethyl ether from...
Synthesis and characterization of a new nanocomposite by filling of CNT with CoFe2O4 Magnetic nanoparticles and grafting to polymer
, Article Nano ; Volume 4, Issue 6 , 2009 , Pages 371-376 ; 17932920 (ISSN) ; Adeli, M ; Actinchap, B ; Bahari, A ; Sharif University of Technology
Abstract
In this work, the synthesis and characterization of a new nanocomposite from carbon nanotubes-graft-polymer (CNTs-g-P) is reported. The products were obtained by the filling of multi-walled carbon nanotubes (MWCNTs) (inner diameter 2040 nm) with CoFe2O4 magnetic nanoparticles, been grafted with poly (caprolactone). The filling process was carried out by using acid treatment through wet chemistry. The structure and the properties of the new nanocomposite were studied with TEM, VSM, TGA, and spectroscopic techniques. © 2009 World Scientific Publishing Company
Surface wettability effect on the rising of a bubble attached to a vertical wall
, Article International Journal of Multiphase Flow ; Volume 109 , 2018 , Pages 178-190 ; 03019322 (ISSN) ; Davoudian, S. H ; Sharif University of Technology
Abstract
This paper deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though, bubbles rising freely in a liquid have extensively been studied, bubbles attached to a wall have not been fully understood. Therefore, in this work, rising bubbles attached to a vertical wall were numerically investigated by applying the ALE method along with adaptive mesh refinement schemes to properly resolve the bubble interface and its deformation. To consider wall wettability effects, different contact angles of 45° 90° and 105° were considered along with the case of freely rising bubbles. The problem was carried out at different Bond numbers of 0.27,...
Super gas wet and gas wet rock surface: state-of- the art evaluation through contact angle analysis
, Article Petroleum ; 2021 ; 24056561 (ISSN) ; Dehghan Monfared, A ; Shayegh, F ; Barzegar, F ; Ghazanfari, M. H ; Sharif University of Technology
KeAi Communications Co
2021
Abstract
Recently, super gas wet and gas wet surfaces have been extensively attended in petroleum industry, as supported by the increasing number of publications in the last decade related to wettability alteration in gas condensate reservoirs. In many cases, contact angle measurement has been employed to assess the wettability alteration. Even though contact angle measurement seems to be a straightforward approach, there exist many misuses of this technique and consequently misinterpretation of the corresponding results. In this regard, a critical inspection of the most recent updated concepts and the intervening parameters in the contact angle based wettability evaluation of liquid-solid-gas...
Supercritical gasification of biomass: Thermodynamics analysis with Gibbs free energy minimization
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 34, Issue 2 , Dec , 2011 , Pages 163-176 ; 15567036 (ISSN) ; Pazuki, G. R ; Vossoughi, M ; Saboohi, Y ; Hashemi, N ; Sharif University of Technology
2011
Abstract
Gasification of biomass in supercritical water is a successful technology for hydrogen production especially by using wet biomass. The whole process, from feeding to purification of hydrogen, consists of a lot of equipment, such as pumps, heat exchangers, heaters, reactors, etc. Because the main reactions take place in the gasification reactor, the gasifier is the most important equipment of the process. In this article, a thermodynamic model, including chemical equilibrium in the reactor that is based on Gibbs free energy minimization, is developed to estimate equilibrium composition for gasification of biomass in supercritical water for hydrogen production. For this analysis, we use three...
Suction-induced hardening effects on the shear modulus of unsaturated silt
, Article International Journal of Geomechanics ; Volume 16, Issue 6 , 2016 ; 15323641 (ISSN) ; Salam, S ; McCartney, J. S ; Dadashi, A ; Sharif University of Technology
American Society of Civil Engineers (ASCE)
Abstract
The small-strain shear modulus Gmax is a key material parameter in modeling the behavior of soils subjected to dynamic loading. Recent experimental results indicate that seasonal weather interaction with near-surface soils causes Gmax to change by up to an order of magnitude in some climates, with a hysteretic response upon drying and wetting. The increase in Gmax during drying and the stiffer response during subsequent wetting have been postulated to be due to plastic hardening during drying. To further understand this behavior, a series of isotropic compression tests were performed on compacted silt specimens at different values of matric suction to evaluate changes in the preconsolidation...
Studies on the catalyst preparation methods and kinetic behavior of supported cobalt catalysts for the complete oxidation of cyclohexane
, Article Reaction Kinetics, Mechanisms and Catalysis ; Volume 114, Issue 2 , Jan , 2015 , Pages 611-628 ; 18785190 (ISSN) ; Khorasheh, F ; Shayegan, J ; Sharif University of Technology
Springer Netherlands
2015
Abstract
Low cost dispersed supported cobalt oxide nanocatalysts on activated carbon (AC) were prepared by two different methods: (1) combined impregnation and deposition–precipitation (IMP-DP) and (2) heterogeneous deposition–precipitation (HDP). XRD, TEM, FESEM, BET and Boehm techniques were used for the characterization of the support and the catalysts. Characterization analyses indicated the negative effect of the wet impregnation method on the IMP-DP technique for the preparation of catalysts for the total oxidation of cyclohexane in air. The catalysts prepared by HDP and IMP-DP methods were found to have significant differences in oxidation activity, morphology, particle size, and shape of...
Streaming potential measurement to quantify wetting state of rocks for water based EOR, inhouse novel setup experience
, Article IOR NORWAY 2017 - 19th European Symposium on Improved Oil Recovery: Sustainable IOR in a Low Oil Price World, 24 April 2017 through 27 April 2017 ; 2017 ; 9789462822092 (ISBN) ; Jafarlou, A ; Nejadali, M ; Esmaeili, S ; Pahlavanzadeh, H ; Ayatollahi, S ; Sharif University of Technology
Abstract
The wetting condition of the reservoir rock is the key to the success of any EOR technique and the ultimate oil recovery. Wettability is dictated by the surface chemistry related to the interactions between the fluids and the rock surface which determines the stability of the water film between the rock and the oil phase. Streaming potential measurement is one of the electrokinetic techniques used to determine the average zeta potential of porous rock which can provide reliable information on fluid-rock interaction and wettability state of the rock surface. Streaming potential measurement has recently been introduced in the oil reservoirs applications and there are still significant...
Stick-slip behavior of sessile drop on the surfaces with irregular roughnesses
, Article Chemical Engineering Research and Design ; Volume 160 , 2020 , Pages 216-223 ; Shayesteh, M ; Shafiei, Y ; Ghazanfari, M. H ; Sharif University of Technology
Institution of Chemical Engineers
2020
Abstract
In this work, sessile drop and low-bond axisymmetric drop shape analysis methods were coupled to provide some new aspects on stick-slip behavior as well as stick time of a drop on calcite surfaces. Slightly hydrophobic calcite surfaces typified with three irregular roughnesses were used to create irregular surfaces to mimic defects for the water-calcite-air systems. Polishing papers of 200, 600, and 1200 grit and a polishing machine were used to prepare surfaces. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared, and atomic force microscopy techniques were employed to evaluate the chemical and physical properties of surfaces. A model was developed to predict...
Steganographic schemes with multiple q-ary changes per block of pixels
, Article Signal Processing ; Vol. 108, issue , 2014 , pp. 206-219 ; Khosravi, K ; Sharif University of Technology
Abstract
A family of matrix embedding steganographic schemes for digital images is investigated. The target schemes are applied to blocks of n pixels in a cover image. In every block, at most m pixels are allowed to change with q-ary steps. We have derived some upper bounds on the embedding efficiency of these schemes for different values on m. It is also shown that these upper bounds approach the general upper bound on the embedding efficiency of q-ary steganography. For the case of q=3, we have shown that there is no feasible optimum member of the family for m=2, although for m=1, a well-known example exists. Instead, for m=2, a new close-to-bound scheme in the family is presented which exploits...
Steganographic schemes with multiple q-ary changes per block of pixels
, Article Signal Processing ; Volume 108 , 2015 , Pages 206-219 ; 01651684 (ISSN) ; Khosravi, K ; Sharif University of Technology
Elsevier
2015
Abstract
A family of matrix embedding steganographic schemes for digital images is investigated. The target schemes are applied to blocks of n pixels in a cover image. In every block, at most m pixels are allowed to change with q-ary steps. We have derived some upper bounds on the embedding efficiency of these schemes for different values on m. It is also shown that these upper bounds approach the general upper bound on the embedding efficiency of q-ary steganography. For the case of q=3, we have shown that there is no feasible optimum member of the family for m=2, although for m=1, a well-known example exists. Instead, for m=2, a new close-to-bound scheme in the family is presented which exploits...
Static pull-in analysis of micro-cantilevers in wet etching fabrication process
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 9 November 2012 through 15 November 2012 ; Volume 9, Issue PARTS A AND B , November , 2012 , Pages 347-350 ; 9780791845257 (ISBN) ; Moeenfard, H ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Parallel micro actuators are mostly fabricated using the wet etching process within which the presence of capillary force and the resulting pull-in instabilities can severely affect the success of the fabrication process. In the case the capillary force is large enough then the beam like structure of the micro actuators is collapsed. The current paper investigates; static behavior of microcantilevers under effect of capillary force. It is observed that with increasing the instability number defined in the paper, the deflection of the micro-cantilevers is increased. This study shows in the wet etching fabrication process, if the distance between the beam and substrate is small enough, the...
Static and dynamic behavior of foam stabilized by modified nanoparticles: Theoretical and experimental aspects
, Article Chemical Engineering Research and Design ; Volume 158 , 2020 , Pages 114-128 ; Ashoori, S ; Ghotbi, C ; Moghadasi, J ; Kharrat, R ; Sharif University of Technology
Institution of Chemical Engineers
2020
Abstract
Gas flooding is a practical secondary scenario for enhanced oil recovery. Channeling and fingering of the injected gas are the major problems facing this technique. These challenges can be mitigated by the injection of gas as foam. However, foam stability influences the overall efficiency of the process, which could be improved by nanoparticles (NPs). This work provides a theoretical and experimental analysis of the NPs wettability effects on foam behavior, in both static and dynamic states. The treated calcite (CaCO3) NPs along with a cationic surfactant (HTAB) were used for this purpose. By comparison of theoretical and experimental data, it was shown that the foam stability in the...
Some important factors in the wet precipitation process of hydroxyapatite
, Article Materials and Design ; Volume 24, Issue 3 , 2003 , Pages 197-202 ; 02641275 (ISSN) ; Ghorbani, M ; Ehsani, N ; Saeri, M. R ; Sorrell, C. C ; Sharif University of Technology
Elsevier Ltd
2003
Abstract
The precipitation process considered here, involved the addition of orthophosphoric acid solution to a calcium hydroxide solution. Several parameters such as the effects of atmosphere controlling, pH, adding extra acid solution, the amount of stirring speed, and post-chemical treatment were studied. In order to study the thermal stability of synthesised powders, they were sintered for 2 h at 1200 °C and the as-precipitated and sintered powder samples were examined using SEM, XRD, FTIR and ICP methods. The results clearly revealed that the final precipitated powder is hydroxyapatite (HA) with good purity, stoichiometry and successful thermal stability. SEM high magnification micrographs...
Smartwater flooding in a carbonate asphaltenic fractured oil reservoir - Comprehensive fluidfluid-rock mechanistic study
, Article 19th European Symposium on Improved Oil Recovery: Sustainable IOR in a Low Oil Price World, IOR NORWAY 2017, 24 April 2017 through 27 April 2017 ; 2017 ; 9789462822092 (ISBN) ; Afzali, S ; Ahmadi, Z ; Mokhtari, R ; Ayatollahi, S ; Sharifi, M ; Kazemi, A ; Nasiri, M ; Fathollahi, S ; Sharif University of Technology
European Association of Geoscientists and Engineers, EAGE
2017
Abstract
Waterflooding has been regarded as an efficient method for pressure maintenance of oil reservoirs. x Improved techniques such as Smart Water flooding as a new EOR/IOR process has gained more momentum based on the recent research activities in this field and the reduction of oil price. Despite many efforts on achieving the governing mechanisms of Smart Water flooding in many individual fields, most of data are sparse and more possible mechanisms which explains all the interactions yet to be introduced. This experimental study used a systematic laboratory framework which is based on seawater treatments at fixed ionic strength to eliminate the ionic strength effects, NaCl considered as the...
Small signal circuit modeling for semiconductor self-assembled quantum dot laser
, Article Optical Engineering ; Volume 50, Issue 3 , 2011 ; 00913286 (ISSN) ; Faez, R ; Sharif University of Technology
Abstract
In this paper, for the first time, we present a small signal circuit model of InGaAs/GaAs self-assembled quantum dot (QD) laser, based on the standard rate equations. By using the presented model, modulation response of QD laser is investigated. The simulation results show that retarded carrier relaxation due to phonon bottleneck degrades the modulation and impulse responses of a QD laser. It is shown that modulation bandwidth is increased with larger inhomogeneous broadening. Also, our model describes the effects of carrier recombinations inside and outside of a QD region, on the modulation response behavior