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Modifying Hole Transport in Branched hematite Nanostructures for Photoelectrochemical Water Splitting
, M.Sc. Thesis Sharif University of Technology ; Naseri, Naimeh (Supervisor)
Abstract
Regarding increasing world population, air pollution and depletion of fossil fuels supplies, hydrogen production via photoelectrochemical water splitting is a promising approach for providing a clean and renewable source of energy. Hematite (α-Fe2O3), the most common natural form of iron oxide, with a suitable band gap, high stability, earth-abundant nature and low cost has been widely acknowledged as a photoanode. However, intrinsic drawbacks of hematite like low electrical conductivity, short hole diffusion length and high recombination rate of electron-hole pairs hinder its photoelectrochemical performance with high efficiency. In this research, hematite nanostructures were synthesized...
Gauge Symmetry in Renormalization Group Flow
, Ph.D. Dissertation Sharif University of Technology ; Ardalan, Farhad (Supervisor)
Abstract
Exact Renormalization Equations (ERGE) are powerful non-perturbative tools to study the dynamics of Quantum Field theories, with respect to the change of energy. Putting cut-off on momentums of the system, is the specific regularization that is used to obtain ERGEs. This regularization breaks the gauge symmetry in the case of gauge theories. So the symmetry will be lost through the energy flow as well.Finding a gauge symmetry for a regularized system is the aim of this research. Also we have investigated the related ERGEs and the behavior of symmetry through the flow
Stability Analysis of Fractional Order Systems Described in Lur'e Structure
,
M.Sc. Thesis
Sharif University of Technology
;
Tavazoei, Mohammad Saleh
(Supervisor)
Abstract
Most of the real-world systems can be modeled as closed loop systems which are made up of a LTI subsystem in the forward path and a memoryless nonlinear subsystem in the feedback path. Such systems are called “Lur’e systems”, the name of the first who introduced these systems. Because of the generality and the wide applicability of this type of systems, studying the stability of them has been notable and interesting to many scientists for a long time. Meanwhile, in recent decades, many scientists in physics and engineering sciences have been interested in applications of the fractional order systems and as a result focused on studying the features of the fractional order systems. An...
Newly designed ternary hematite-based heterojunction for PEC water splitting
, Article Applied Surface Science ; Volume 550 , 2021 ; 01694332 (ISSN) ; Eftekharinia, B ; Tayebi, M ; Lee, B. K ; Naseri, N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Hematite is recognized as a promising photoanode for photoelectrochemical water oxidation to produce solar hydrogen due to its favorable properties. However, the high charge carrier recombination rate due to low electrical conductivity and sluggish oxygen reduction kinetics of pure hematite hinder its photocatalytic activity. This work proposed a new hematite-based heterostructure of Ti-Fe2O3/Fe2TiO5/FeOOH, synthesized through a hydrothermal method. The photoanode morphology was branched nanorods that expanded their surface area and improved charge transfer at the photoanode/electrolyte interface. In a novel and complement modification approach, a thin pseudobrookite interlayer was applied...
H2S sensing properties of added copper oxide in WO3
, Article Key Engineering Materials ; Volume 543 , March , 2013 , Pages 145-149 ; Razi Astaraei, F. (Fatemeh) ; Kashani, Sh. (shima) ; Iraji Zad, A. (Azam) ; Sharif University of Technology
2013
Abstract
We study Hydrogen sulfide gas detection properties of pure and 1% copper oxide added WO3 thin films. The spin coated deposits on alumina substrates were annealed at 500 C for 1 hour in order to improve the crystallinity of the films. The sensitivity of pure tungsten oxide is poor even at temperatures of about 100 C but the doped samples exhibit good response to H2S gas. Our data show sensitivity of about 1500 in 10 ppm diluted gas in air at 100 C. The films are sensitive to the gas even at 250 ppb (sensitivity about 2) H2S concentration at 100 C but with rather long recovery time. Crystal structure, morphology and chemical composition of samples were studied by X-Ray diffraction (XRD),...