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mahmudi--niaz-mohammad
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Photocatalytic Degradation of Dye in Wastewater Using Nanomaterials Based Zinc-iron
,
M.Sc. Thesis
Sharif University of Technology
;
Kazemeini, Mohammad
(Supervisor)
;
Mahmudi, Niaz Mohammad
(Co-Supervisor)
;
Baqalha, Morteza
(Co-Supervisor)
Abstract
Removing pollutants of water and, in general, wastewater treatment is one of the most important issues in the world. In this research, we synthesized a nanophotocatalyst based on znic-iron in the form of a magnetic core-shell Fe3O4@ZIF-8, and used to degrade the malachite green toxic color of wastewater. SEM, XRD and FT-IR analyzes have been taken and analyzed fore all three core, shell and core-shell composite catalysts.Due to the band gap of core-shell nanocomposite and the performance of the malachite green dye, a photocatalytic process under the visible light was obtained, which at an optimum amount of photocatalyst 0.003g, we reach 99.2% dye degradation at the 30ppm concentration. This...
Degradation of Dye in Wastewater Using iron Based Porous Nanocatalyst in a Batch Reactor
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Mahmoudi, Niaz Mohammad (Supervisor)
Abstract
consumption of which (especially azo dyes) have been increasing nowadays, causing the increase of textile wastewaters. Usually, these wastewaters contain an immense number of dyes, and if these dyes release in the environment especially in waters, they cause some problems, such as the change of watercolor as well as taste, and affect creatures' lives severely. Moreover, If the dyes are left untreated in aquatic ecosystems, they can remain in the environment for a very long time, resulting in harmful and irreversible effects. Azo dyes are classified as mono, di-, three, azo dyes due to their bonds. Because dyes are increasingly used, nowadays, different methods are developed for the treatment...
Design & Synthesis of ZnO-based Composite Nanofiber Photocatalysts with Z-Scheme Structure for Degradation of Organic Pollutants
, Ph.D. Dissertation Sharif University of Technology ; Moshfegh, Alireza (Supervisor) ; Pourjavadi, Ali (Supervisor) ; Mahmoodi, Niaz Mohammad (Co-Supervisor)
Abstract
The aim of conducting this research is to study, fabrication and photocatalytic application of electrospun ZnO-based composite nanofibers. One of the most important challenges is to apply photocatalyst under solar irradiation and improve its activity for pollutant degradation. ZnO is a wide band gap semiconductor, hence, it is not active under the visible light. In Iran, we have at least 300 sunny days in a year. Therefore, fabrication and application of photocatalytic material with activity under the sunlight which contains 47% of visible light is so vital in our country. Since CuO is a visible light active photocatalyst and its interface with ZnO forms a type I heterojunction, this...
Role of interfacial fracture energy and laminate architecture on impact performance of aluminum laminates
, Article Composites Part A: Applied Science and Manufacturing ; Volume 39, Issue 11 , 2008 , Pages 1685-1693 ; 1359835X (ISSN) ; Bagheri, R ; Mahmudi, R ; Sharif University of Technology
2008
Abstract
The impact behavior of aluminum/epoxy laminates was studied by changing the number of layers and the interface strength. It should be noted that although the overall thickness did not changed, the individual layers decreased in thickness when the number of layers increased. The results indicate that the impact resistance of the laminate increases with the number of layers, while the interface strength has a less pronounced influence (50%) on the impact resistance of the laminate. It is also deducted that if the ratio of layer thickness to plastic zone size is smaller than or equal to 1, the impact behavior of the laminates is sensitive to the interface strength. © 2008 Elsevier Ltd. All...
Improved corrosion resistance and mechanical properties of biodegradable Mg-4Zn-xSr alloys: effects of heat treatment, Sr additions, and multi-directional forging
, Article Journal of Materials Research and Technology ; Volume 20 , 2022 , Pages 3363-3380 ; 22387854 (ISSN) ; Alizadeh, R ; Mahmudi, R ; Sharif University of Technology
Elsevier Editora Ltda
2022
Abstract
The effects of Sr additions, heat treatment (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biodegradability of Mg-4Zn-xSr alloys were investigated. Corrosion behavior of the alloys was evaluated by the polarization and hydrogen evolution tests. Shear punch and hardness tests were employed to determine the mechanical properties. It was found that mechanical properties and corrosion resistance of the as-cast Mg-4Zn alloy increased by 0.3 wt% Sr addition. However, further increasing the Sr content not only did not improve the mechanical strength, but also had detrimental effects on the corrosion resistance, due to the increased size and...
Determination of tearing energy from uniaxial tension tests of aluminum alloy sheet
, Article Journal of Materials Processing Technology ; Volume 147, Issue 2 , 2004 , Pages 185-190 ; 09240136 (ISSN) ; Mohammadi, R ; Sepehrband, P ; Sharif University of Technology
2004
Abstract
Tearing energy of AA5010 aluminum alloy sheets has been studied by the single tensile testing (STT) and multiple tensile testing (MTT) methods. The total energy required to tear the specimens was assumed to be composed of two components; one associated with uniform plastic deformation, which occurs in the work-hardening range of the material, and the other with post-uniform deformation and tearing which leads to the failure of the specimens. In the STT method, tearing energy was calculated by subtracting the plastic deformation energy, dissipated in the uniform deformation range, from the total energy absorbed by a single specimen during tension. In the MTT method, which uses different...
Effects of number of layers and adhesive ductility on impact behavior of laminates
, Article Materials Letters ; Volume 58, Issue 22-23 , 2004 , Pages 2721-2724 ; 0167577X (ISSN) ; Bagheri, R ; Mahmudi, R ; Sharif University of Technology
2004
Abstract
Laminated composites are made using different routes, including adhesive bonding. In this investigation, Aluminum layers are bonded together using epoxy adhesive (neat, rubber-modified and filled-epoxy). In phase one of this investigation, the influence of number of layers and adhesive ductility have been studied on dynamic behavior of composites. The results of impact behavior of laminates indicate that the impact energy increases with the number of layers. Also, it can be concluded that there is much more sensitivity of the impact energy of the composite to the number of the layers than that to the adhesive composition. © 2004 Elsevier B.V. All rights reserved
Effect of Zn content and processing route on the microstructure, mechanical properties, and bio-degradation of Mg-Zn alloys
, Article Journal of Materials Research and Technology ; Volume 21 , 2022 , Pages 4473-4489 ; 22387854 (ISSN) ; Gerashi, E ; Alizadeh, R ; Mahmudi, R ; Sharif University of Technology
Elsevier Editora Ltda
2022
Abstract
The effects of zinc content (2 and 4 wt%), heat treatment (solution-Treated and T6), as well as hot deformation (extrusion and multi-directional forging (MDF)) on the microstructure, mechanical and degradation behavior of Mg-Zn alloys were studied. As the result of microstructure refinement, solid solution and precipitate strengthening (formation of MgZn second phases), the strength of pure Mg was increased after Zn addition. Solution treatment of the Mg-4Zn alloy resulted in 16% softening due to the dissolution of the MgZn second phases and also grain growth, while aging treatment increased the strength value by 8% in comparison to the as-cast material because of the formation of the fine...
Effects of Sr additions on the microstructural stability and mechanical properties of a cast Mg–4Zn alloy
, Article Materials Science and Engineering A ; Volume 843 , 2022 ; 09215093 (ISSN) ; Asadollahi, M ; Alizadeh, R ; Mahmudi, R ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The effects of Sr additions (0.3, 0.6 and 0.9 wt%) on the microstructural evolution, thermal stability, and mechanical properties of a cast Mg–4Zn alloy were investigated. The extent of grain growth and stability of the intermetallic compounds were studied by optical and scanning electron microscopy (SEM), respectively. Mechanical properties of the studied alloys were evaluated by shear punch testing (SPT) method and also the hardness test. Hardness and shear strength of the base alloy were increased by Sr additions in the as-cast condition, due to the grain refinement effect of Sr and also presence of the Sr-containing Mg17Sr2 and Mg70Zn25Sr5 precipitates. However, the optimum amount of Sr...
Enhanced X-band wave dissipation performance in bilayer absorber composed of bare epoxy resin and epoxy resin filled with [CaTiO3/ZnFe2O4]@C nanocomposite
, Article Journal of Magnetism and Magnetic Materials ; Volume 539 , 2021 ; 03048853 (ISSN) ; Elveny, M ; Niaz Akhtar, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this study, a novel idea was utilized for designing high performance bilayer absorber for X-band frequency. The microwave dissipation features of the bilayer structure absorbers with one-layer bare resin epoxy and the other epoxy resin filled with [CaTiO3/ZnFe2O4]@C nanocomposite as lossy filler were simulated with CST studio suite within 2–18 GHz. The lossy filler was successfully developed via chemical method. In the first step two distinct single layer absorbers of bare resin epoxy and resin epoxy filled with [CaTiO3/ZnFe2O4]@C nanocomposite ([CT/ZF]@C) were prepared and in the second step the measured electromagnetic parameters were considered as input data of CST studio suite for...
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 18, Issue 5 , 2011 , Pages 557-561 ; 16744799 (ISSN) ; Nedjad, S. H ; Behnam, M. M. J ; Sharif University of Technology
2011
Abstract
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2 (Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment
A novel method for materials selection in mechanical design: Combination of non-linear normalization and a modified digital logic method
, Article Materials and Design ; Volume 28, Issue 1 , 2007 , Pages 8-15 ; 02613069 (ISSN) ; Mahmudi, H ; Abedian, A ; Mahmudi, R ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
In this investigation, a novel numerical method is proposed for materials selection. This method is based on the well known weighting factor approach while combining non-linear normalization with a modified digital logic method. The proposed mathematical functions and their applicability to the materials selection process is verified by examining two case studies in mechanical design and comparing the results with those obtained from the classical weighted property method. It is concluded that the new approach is capable of providing more reasonable selections as opposed to those obtained from the existing method. © 2005 Elsevier Ltd. All rights reserved
Physiological and psychological neural system modeling for a key-pressing test
, Article Proceedings of the IASTED International Conference on Biomedical Engineering, Salzburg, 25 June 2003 through 27 June 2003 ; 2003 , Pages 66-70 ; 0889863539 (ISBN) ; Shahdi, S. A ; Vahdat, B. V ; IASTED ; Sharif University of Technology
2003
Abstract
The model introduced in this article for neural system describes both physiological and psychological concepts of neural system and is based on the models of individual elements of the system. This model includes psychological characteristics such as; perception, prediction, learning and response planning, and physiological features such as; sensory analysis, memory and motor execution. The model is designed in such a way that it describes the performance of the neural system for a key-pressing test. The key-pressing experiment consists of a screen with numbers from 1 to 9, which is shown to the operator where one of the numbers is specified by a special color and the operator is to push the...
A simplified fuzzy logic approach for materials selection in mechanical engineering design
, Article Materials and Design ; Volume 30, Issue 3 , 2009 , Pages 687-697 ; 02641275 (ISSN) ; Dehghan Manshadi, B ; Abedian, A ; Mahmudi, R ; Sharif University of Technology
2009
Abstract
Material selection for mechanical designs is an important task. Different approaches have been proposed to fulfill this job, so far. However, most of them work well with only quantitatively measurable properties of materials. Also, due to a wide range of materials available, the selection space finds a fuzzy characteristic. Therefore, here a simplified fuzzy logic approach is introduced to provide a powerful tool for easy dealing with the qualitative properties of materials and the corresponding fuzzy space. With this approach the volume of mathematics involved with the conventional methods reduces, considerably. The results show an excellent match with the Manshadi's method. © 2008 Elsevier...
Effects of hydrothermal coating on the degradation behavior and biocompatibility of an Mg–4Zn–0.3Sr alloy
, Article Materials Letters ; Volume 330 , 2023 ; 0167577X (ISSN) ; Jamalpour, M ; Alizadeh, R ; Labbaf, S ; Mahmudi, R ; Sharif University of Technology
Elsevier B.V
2023
Abstract
Hydrothermal method was applied to create a protective coating on the Mg–4Zn–0.3Sr alloy, using de-ionized water (as precursor) for different synthesizing times of 3, 4, 5, and 6 h. XRD and EDS line-scan confirmed formation of Mg(OH)2 coating. Based on the surface morphological appearance, 5 h coating time at 160 °C was found to be the optimum condition. The corrosion current of 2.58 µA/cm2 in the uncoated sample decreased to 0.48 µA/cm2 in the coated condition. Also, the cytotoxicity assessments using Alamar blue test showed that the cell viability and cell attachment to the formed Mg(OH)2 coating are more pronounced in comparison with the uncoated alloy. © 2022 Elsevier B.V
High-efficiency microwave absorber based on carbon Fiber@La0.7Sr0.3MnO@NiO composite for X-band applications
, Article Ceramics International ; Volume 47, Issue 14 , 2021 , Pages 20438-20446 ; 02728842 (ISSN) ; Li, H ; Niaz Akhtar,, M ; Shi, L ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Carbon fiber (CF) as a multifunctional material with superb performance in aviation industry has serious drawback such as impedance mismatch which restricted the capability of using it as microwave absorber materials. In this research, a novel hierarchical carbon fiber@La0.7Sr0.3MnO@NiO (CF/LS/N) composite was facilely and successfully synthesized via sol-gel and subsequent hydrothermal reactions. The structural, morphological, magnetic and electromagnetic behavior of the composite were precisely evaluated via XRD, FESEM, XPS, VSM and VNA analysis. According to the systematic evaluation results, the synergistic positive effect of adding NiO nanoparticles is revealed in improving the...
ZrN fractal-graphene-based metamaterial absorber in the visible and near-IR regimes
, Article Optik ; Volume 237 , 2021 ; 00304026 (ISSN) ; Choudhury, P. K ; Niaz Akhtar, M ; Sharif University of Technology
Elsevier GmbH
2021
Abstract
The absorption characteristics of zirconium nitride (ZrN)-based metamaterial absorber of fractal geometry are studied. The proposed absorber is comprised of fractal metasurface at the top having subwavelength-sized periodic pattern of specially designed ZrN circular nano-discs arranged over silicon dioxide (SiO2) substrate. A tri-layer graphene, owing to its exhibiting better tunability, is introduced at the interface of metasurface and substrate. The bottom side of SiO2 is coated with silver nanolayer to block transmission. The absorptivity essentially depends on the kind of fractal design used in metasurface to configure the absorber. The obtained results exhibit the absorption...
Evaluations of structural, magnetic and various dielectric parameters of Ni-substituted Zn2W-type hexagonal ferrites for high frequency (1–6 GHz) applications
, Article Ceramics International ; Volume 45, Issue 18 , 2019 , Pages 24202-24211 ; 02728842 (ISSN) ; Shaukat, F ; Niaz Akhtar, M ; Ahmad, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The structural, electrical, magnetic and high frequency properties of Ni-substituted Zn2W-type hexagonal ferrites were investigated for microwave applications. Ferrite powders with chemical compositions Ba0 · 5Sr0.5NixZn2-xFe16O27 (where Ni-substitution was varied from 0.0 to 1.5 with a step size of 0.5) were prepared using sol-gel auto-combustion at 1300 °C. X-ray diffraction (XRD) analysis confirmed the single-phase hexagonal ferrite structure. The lengths of both the axis i.e. minor and major (a, c) obtained from hkl values of XRD peaks were decreased with Ni-substitution due to the difference in ionic radius of the substituted metal ions. DC electrical resistivity obtained by two-point...
Microwave absorption characteristics of polyaniline@Ba0.5Sr0.5Fe12O19@MWCNTs nanocomposite in X-band frequency
, Article Journal of Magnetism and Magnetic Materials ; Volume 524 , 2021 ; 03048853 (ISSN) ; Mustafa Mohamed, A ; Sharifi, A ; Niaz Akhtar, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this research, polyaniline@Ba0.5Sr0.5Fe12O19@MWCNTs nanocomposite was prepared via co-precipitation and in-situ polymerization methods, respectively. Microstructural, magnetic and electromagnetic wave absorption analysis of the prepared nanocomposite were studied via XRD, FESEM, VSM and VNA. Compared with Ba0.5Sr0.5Fe12O19@MWCNTs, the microwave absorption bandwidth of the coated nanocompoite with polyaniline was significantly enhanced, which increased to approxiamately 4 GHz from 3 GHz. The effective microwave absorption performance of the Ba0.5Sr0.5Fe12O19@MWCNTs nanocomposite was attributed to increase in the interfacial polarization, improvement in impedance matching as well as porous...
Degradation behavior of the as-extruded and ECAP-processed Mg-4Zn alloy by Ca addition and hydrothermal coating
, Article Journal of Materials Research and Technology ; Volume 20 , 2022 , Pages 1204-1215 ; 22387854 (ISSN) ; Mohammadi Zerankeshi, M ; Nobakht Farin, F ; Alizadeh, R ; Mahmudi, R ; Sharif University of Technology
Elsevier Editora Ltda
2022
Abstract
Coating is an effective approach to address the high corrosion rate of biodegradable Mg alloys, as their main challenge toward their extensive use. In this regard, it was tried to control the degradation process of an Mg-4Zn alloy by Ca addition, equal channel angular pressing (ECAP), and hydrothermal coating. The obtained results indicated that excellent grain refinement induced by Ca incorporation and ECAP simultaneously, improved both mechanical strength and corrosion resistance of the Mg-based substrate. The achieved grain refinement resulted in a thicker, more compact and integrated coating, where the ECAP-processed Mg-4Zn-0.5Ca alloy exhibited the best coating quality with no...