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Hierarchical Co3O4/Co(OH)2 nanoflakes as a supercapacitor electrode: experimental and semi-empirical model
, Article ACS Applied Materials and Interfaces ; Volume 7, Issue 21 , 2015 , Pages 11172-11179 ; 19448244 (ISSN) ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2015
Abstract
In this research, facile and low cost synthesis methods, electrodeposition at constant current density and anodization at various applied voltages, were used to produce hierarchical cobalt oxide/hydroxide nanoflakes on top of porous anodized cobalt layer. The maximum electrochemical capacitance of 601 mF cm-2 at scan rate of 2 mV s-1 was achieved for 30 V optimized anodization applied voltage with high stability. Morphology and surface chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The size, thickness, and density of nanoflakes, as well as length of the porous anodized Co layer were measured about 460 ± 45 nm,...
Ti-rich TiO2 tubular nanolettuces by electrochemical anodization for all-solid-state high-rate supercapacitor devices
, Article ChemSusChem ; Volume 12, Issue 17 , 2019 , Pages 4064-4073 ; 18645631 (ISSN) ; Khajehdehi, O ; Sabbah, A ; Naseri, N ; Sharif University of Technology
Wiley-VCH Verlag
2019
Abstract
Supercapacitors store charge by ion adsorption or fast redox reactions on the surface of porous materials. One of the bottlenecks in this field is the development of biocompatible and high-rate supercapacitor devices by scalable fabrication processes. Herein, a Ti-rich anatase TiO2 material that addresses the above-mentioned challenges is reported. Tubular nanolettuces were fabricated by a cost-effective and fast anodization process of Ti foil. They attained a large potential window of 2.5 V in a neutral electrolyte owing to the high activation energy for water splitting of the (1 0 1) facet. Aqueous and all-solid-state devices showed diffusion time constants of 46 and 1700 ms, as well as...
Fabrication and Investigation of Co3O4 Sponged Shape Nanostructured Supercapacitor Layer Electrodes Modified by Graphene
, Ph.D. Dissertation Sharif University of Technology ; Moshegh, Alireza (Supervisor) ; Naseri, Naima (Supervisor)
Abstract
Recently, Supercapacitors, as one of the most important energy storage devices, have attracted attensions by the scientists. Supercapcitor devices with appoporate design can store energy by two different mechanisms: i) physical (like conventional capacitors, i.e. by using polarization of the electrolyte, and ii) formation of electric double layer) and chemical mechanisms (like batteries, with reversible faradic reactions). These energy storage mechanisms allow these devices not only store high energy density but also they can provide high power density. In this project, two Co3O4/Co(OH)2 and Co3O4@Sponge-like rGO electrodes are made with chemical and electrochemical methods. To characterize...
Selecting Support Layer for Electrodeposited Efficient Cobalt Oxide/Hydroxide Nanoflakes to Split Water
, Article ACS Sustainable Chemistry and Engineering ; Volume 4, Issue 6 , 2016 , Pages 3151-3159 ; 21680485 (ISSN) ; Esfandiar, A ; Qorbani, M ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2016
Abstract
Energy and environment crises motivated scientists to develop sustainable, renewable, and clean energy resources mainly based on solar hydrogen. For this purpose, one main challenge is the low cost flexible substrates for designing earth abundant efficient cocatalysts to reduce required water oxidation overpotential. Here, a systematic morphological and electrochemical study has been reported for cobalt oxide/hydroxide nanoflakes simply electrodeposited on four different commercially available substrates, titanium, copper sheet, steel mesh, and nickel foam. Remarkable dependence between the used substrate, morphology, and electrocatalytic properties of nanoflakes introduced flexible porous...
Synthesis and Characterization of CdS Modified TiO2 Nanotubes for Studying of Photoelectrochemical (PEC) Properties
, M.Sc. Thesis Sharif University of Technology ; Moshfegh, Alireza (Supervisor) ; Azimirad, Rouhollah (Supervisor)
Abstract
In this research, first thin films with nanostructures of titanium nanotube arrays (TNAs) synthesized by anodization under different applied voltage (20- 60 V) and different reaction times (120 and 200 min). The electrolyte solution for synthesizing the samples contained 90% ethylene glycol (EG), 10% DI water, 0.1 M NHR4RF and a little HR3RPOR4R to reach the pH to 5.6. The synthesized samples crystallized under annealing treatment at 500 °C (with heating rate of 9.5 °CminP -1 P). The scanning electron microscopy (SEM) analysis was indicate that the length and the inner diameter of the nanotubes have increased from 1.6 μm and 67 nm (for 30 V anodization and for 2h) to 4.2 μm and 125 nm (for...
How CdS nanoparticles can influence TiO2 nanotube arrays in solar energy applications?
, Article Applied Catalysis B: Environmental ; Volume 162 , January , 2015 , Pages 210-216 ; 09263373 (ISSN) ; Naseri, N ; Moradlou, O ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this study, titanium dioxide (TiO2) nanotube array (TNA) films are fabricated via anodization of titanium (Ti) sheet. After annealing, the films consisted of well ordered, vertically oriented TNAs of 125±6nm diameter, 38±3nm wall thickness, and 2.9±0.3μm in length. Cadmium sulfide (CdS) nanoparticles are deposited on the synthesized TNAs by sequential-chemical bath deposition (S-CBD) method with different immersion cycle (n) to produce heterogeneous TNA/CdS-n (n=10, 20 and 30) nanostructures. UV-visible absorption spectra of the samples revealed that the absorption edge of CdS modified TNAs was shifted to a higher wavelength with respect to the pure TNAs indicating band gap reduction of...
Shedding light on pseudocapacitive active edges of single-layer graphene nanoribbons as high-capacitance supercapacitors
, Article ACS Applied Energy Materials ; Volume 2, Issue 5 , 2019 , Pages 3665-3675 ; 25740962 (ISSN) ; Esfandiar, A ; Mehdipour, H ; Chaigneau, M ; Irajizad, A ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2019
Abstract
In the field of energy storage by high-rate supercapacitors, there has been an upper limit for the total interfacial capacitance of carbon-based materials. This upper limit originates from both quantum and electric double-layer capacitances. Surpassing this limit has been the focus of intense research in this field. Here, we precisely investigate the effect of chemical functional groups and physical confinement on the electrochemical performance of graphene nanoribbons. We present the results of a quasi-one-dimensional single-layer graphene nanoribbon (120 nm in width and -100 μm in length) microelectrode fabricated by mechanical exfoliation of graphite, followed by electron beam lithography...
Stochastic nature of series of waiting times
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 6 , 2013 ; 15393755 (ISSN) ; Aghamohammadi, C ; Dashti Naserabadi, H ; Salehi, E ; Behjat, E ; Qorbani, M ; Khazaei Nezhad, M ; Zirak, M ; Hadjihosseini, A ; Peinke, J ; Tabar, M. R. R ; Sharif University of Technology
2013
Abstract
Although fluctuations in the waiting time series have been studied for a long time, some important issues such as its long-range memory and its stochastic features in the presence of nonstationarity have so far remained unstudied. Here we find that the "waiting times" series for a given increment level have long-range correlations with Hurst exponents belonging to the interval 1/2
Multi-porous Co3O4 nanoflakes @ sponge-like few-layer partially reduced graphene oxide hybrids: towards highly stable asymmetric supercapacitors
, Article Journal of Materials Chemistry A ; Volume 5, Issue 24 , 2017 , Pages 12569-12577 ; 20507488 (ISSN) ; Chou, T. C ; Lee, Y. H ; Samireddi, S ; Naseri, N ; Ganguly, A ; Esfandiar, A ; Wang, C. H ; Chen, L. C ; Chen, K. H ; Moshfegh, A. Z ; Sharif University of Technology
2017
Abstract
The controlled growth of metal oxide nanostructures within hierarchically porous conductive carbon-based frameworks is critically important to achieving high volumetric performance and appropriate channel size for energy storage applications. Herein, we grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly. Maximum specific/volumetric capacitances of 1112 F gCo3O4-1 (at 3.3 A gCo3O4-1), 178 F cm-3 (at 2.6 A cm-2), and 406 F gtotal-1 (at 1 A gtotal-1) and sensible rate capability (80% retention by increasing the charge/discharge...
Construction of an Experimental Device for Foaming Agent and an Experimental Study of the Properties of Foaming Agent
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir....
Numerical Analysis of An Annular Gas Turbine Combustor
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar...
A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]
, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology
Abstract
Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...
Theoretical and Experimental Study to Conversion of AUC to UO2 by Microwave Heating
, Ph.D. Dissertation Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Ghannadi Maragheh, Mohammad (Co-Advisor) ; Ghasemi, Mohammad Reza (Co-Advisor)SAR Imaging Using the TomoSAR Technique to Resolve Multiple Scatterers
, M.Sc. Thesis Sharif University of Technology ; Bastani, Mohammad Hassan (Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
Abstract
During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of...
Estimating Possible Effects of Subsidies in Competition and Development of Fixed Broadband Internet
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor) ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms
Estimating Price Elasticity of Natural Gas Demand in Iran's Residential Sector: A Regression Discontinuity Approach
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
Estimating the price elasticity of gas demand involves complexities depending on the gas market structure and pricing mechanisms in different countries. Distinguishing between supply and demand shocks and block pricing are among the main challenges that can cause endogeneity in elasticity estimates. Iran's domestic gas network, one of the largest and most extensive household gas markets, is divided into five climatic zones based on weather conditions. The pricing steps for these five climates during the five cold months are such that a customer in a warmer climate pays higher prices. Conversely, the pricing steps for the seven warm months are the same for all climates. This policy creates a...
Estimate the Effect of Religiosity on Voter Turnout
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
The correlation between religious adherence and voter turnout is widely studied. However, whether the relation is causal is an open question. We use Household Expenditures and Income Survey (HEIS) data in Iran, which encompasses nine distinct religious expenditures. These expenditures have low correlation with each other and represent different aspects of religious adherence. We use Imamzadeh (some historical holy shrines) as Instruments to estimate the causal effect of religious expenditures on voter turnout. The results reveal that religious expenditures influence both presidential and parliamentary voter turnout, with a notably stronger impact on presidential elections
Joint Optimization of Computation Offloading and Resource Allocation in Mobile Edge Computing Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to...
Non-Scratch, Antibacterial And Self-cleaning SiO2/TiO2 Nano Composite Coating on Surgical Tools By Sol-Gel
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
In this study TiO2/SiO2 thin films were prepared by sol-gel method from Tetra isopropylortho Titanate(TIPT) as the principle of TiO2 material with Tera ethoxysilane(TEOS) as the principle of SiO2 material to achieve high scratch-resistant , antibacterial and self-cleaning surface area under the effect of various percentage of SiO2 . Film deposition was carried out using a dip-coating technique and heat-treatment was used at 700ºC to achieve crystalline of films with excellent adherence the of substrate.
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope...
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope...
Simulation and Control of an Aromatic Extractive Distillation Column
,
M.Sc. Thesis
Sharif University of Technology
;
Shahrokhi, Mohammad
(Supervisor)
Abstract
In this study steady state and dynamic simulation of an NFM extractive distillation unit for seperation of aromatics and non-aromatic components has been carried out. Column output composition obtained with experimental binary coefficients is compared with those obtainded by UNIFAC equation. The results indicate that using UNIFAC for all binrary coefficients results in an unacceptable error in concentration of benzene. If the experimental binary coefficents of benzene with NFM are used and the rest are calculated by UNIFAC equation, the simulation results will be very close to those obtained via experimental binary coefficients. Also it is shown that considering a constant efficiency for all...