Enhanced hardness and corrosion resistance of Zn/SiO2 films by electrodeposition

, Article Journal of the Electrochemical Society ; Volume 162, Issue 9 , 2015 , Pages D480-D485 ; 00134651 (ISSN) Ghorbani, M ; Salehi, F ; Razavizadeh, O ; Sharif University of Technology

Electrochemical Society Inc 2015

Abstract

The electrodeposition of Zn-SiO2 nanocomposites has been investigated with different electrolytes: triethanolamine as a dispersing agent, and cetyl trimethylammonium bromide and dodecyl dimethylamine oxide as ionic (cationic) and non-ionic surfactants. Appropriate electrophoretic potentials for each solution were obtained using cyclic voltammetry. The results show that the most stable SiO2 nanoparticles with zeta potential range of 25 to 41 mV, along with highest SiO2 mobility of 0.4 to 0.7 m2/V.s were dispersed by triethanolamine in ethanol and the resulting coating adhesion improved up to 5.87 MPa in the standard pull off test, with the enhanced hardness of...

Sol–gel preparation and corrosion properties of Zn–SiO2 nanocomposite thin film

, Article Journal of Sol-Gel Science and Technology ; Volume 79, Issue 1 , 2016 , Pages 133-143 ; 09280707 (ISSN) Razavizadeh, O ; Ghorbani, M ; Sharif University of Technology

Springer New York LLC 2016

Abstract

In this study, a novel nanocomposite thin film of Zn–SiO2 is considered. The thin film is a viable alternative for higher abrasion-resistant coatings. DLS technique revealed that the nanoparticle size is to be below 10 nm, and FE-SEM showed particle size to be below 17 nm in the obtained coating. The coating was found to be highly adhesive with an amorphous structure and hardness value above 1000HV. Corrosion resistance studies using linear polarization technique revealed that this unique nanocomposite has a lower corrosion rate than hot-dip galvanized steel at higher positive potentials. A conclusive mechanism for corrosion and erosion improvement has been proposed. Graphical Abstract:...

Surface modification of carbon steel by ZnO-graphene nano-hybrid thin film

, Article Surface and Coatings Technology ; Volume 363 , 2019 , Pages 1-11 ; 02578972 (ISSN) Razavizadeh, O ; Ghorbani, M ; Sharif University of Technology

Elsevier B.V 2019

Abstract

Application of corrosion resistant coatings is one of the most widely used means of protecting steel. Zinc coated (galvanize) steel, is well known for galvanic protection of steel substrates and nowadays, particular attention has been paid to the coupling of graphene oxide (GO) with metallic materials, in order to lessen corrosion rate. In this research, an isopropanol supercritical reducing environment prepared to make zinc ions bond directly with graphene oxides, to form a button shape hybrids of ZnO-Graphene (ZnOG). The hybridized bonding between zinc and graphene oxide is confirmed by Fourier Transform Infra-Red analysis. And the morphology revealed, using a Field Emission Scanning...

The Structure and Corrosion Behavior of Synthesized Zn-SiO2 Nano-composite Coating by Sol-Gel Method

, M.Sc. Thesis Sharif University of Technology Razavizadeh, Omid (Author) ; Ghorbani, Mohammad (Supervisor)

Abstract

Zinc–silicanano-composite coatings were produced by successive dip coatand sintering procedure from different sol-gel solutions. The surface and cross-sectional morphologies of Zn-SiO2 nano-particles (NPs) were examined using field emission scanning electron microscopy (FE-SEM). Corrosion resistance evaluated by means of polarization and electrochemical impedance spectroscopy showed that even thin films of Zn-SiO2 in orders of 200 nm can have corrosion rates as low as conventional hot dip galvanized steels. Multi-layers coatings have been studied and showed that 10 layers coating with the thickness of 2m has the lowest corrosion rate with the passive region in anodic branch. Corrosion...

Photo-Electrochemical application of ZnOG thin film for in situ monitoring of steel sour corrosion

, Article Surface Engineering and Applied Electrochemistry ; Volume 56, Issue 2 , 2020 , Pages 242-247 Razavizadeh, O ; Ghorbani, M ; Shafiekhani, A ; Sharif University of Technology

Pleiades Publishing 2020

Abstract

Abstract: Further to traditional corrosion monitoring techniques for rated deteriorations, nowadays modern electrochemical monitoring methods are promising for the control of non-rated damage mechanisms. Considering carbon steel as the most commonly used alloy in the oil and gas industry, there are special grades under NACE MR0175 standard which are immune to sour corrosion. However, according to the industry reports, their immunity can be terminated by upset conditions or on site repairs. This issue will impose either a high operational risk or exorbitant maintenance and inspection costs. Hence, in this paper, a new monitoring technology framework is discussed to lessen a catastrophic...

Dynamic relay selection and resource allocation in cooperative networks based on OFDM

, Article 17th European Wireless Conference 2011, EW 2011 ; 2011 , Pages 328-332 ; (Print ISBN): 978-3-8007-3343-9 Javidbakht, O ; Alizadeh, N. N ; Razavizadeh, S. M ; Sharif University of Technology

2011

Abstract

In this paper, we are planning to introduce a new method for relay selection and resource allocation in OFDM-based cooperative networks. Up to now, there have been relatively few works clearly concentrating on the combination of relay selection and resource allocation in such networks. In our work, a network with a single transmitter, a single receiver and a group of relays is considered. Relays work on Amplify and Forward (AF) method and there is no direct link between the transmitter and the receiver. The optimization problem is to maximize the throughput of the receiver with constraints on the amounts of the power of the transmitter and relays, and subcarriers. We will introduce an...

Effect of photoelectrochemical activity of ZnO-graphene thin film on the corrosion of carbon steel and 304 stainless steel

, Article Journal of Materials Engineering and Performance ; Volume 29, Issue 1 , 2020 , Pages 497-505 Razavizadeh, O ; Bahadormanesh, B ; Ghorbani, M ; Simchi, A ; Sharif University of Technology

Springer 2020

Abstract

In this research, the ZnOG hybrid thin film was produced via solgel method. The surface morphology, band gap and photoactive properties of the films were studied by means of SEM, UV–Vis and photoluminescence analysis. In addition, the ability of the thin film in photocathodic protection of carbon steel (CS) and 304 stainless steel in 3.5 wt.% NaCl and Na2S solutions under dark and UV illumination was investigated by polarization test as well as OCP and current measurements during coupling of steels with ZnOG photoanode. The mix band gap is reduced to the orders of 1.17 eV through hybridization of ZnO with graphene oxide. In both NaCl and Na2S solutions, the ZnOG thin film could effectively...

ECG Denoising by Deterministic Approaches

, M.Sc. Thesis Sharif University of Technology Taghavi Razavizadeh, Marjaneh (Author) ; Shamsollahi, Mohammad Bagher (Supervisor)

Abstract

The goal of the research presented in this thesis is removing noise from electrocardiogram (ECG) signals. The electrocardiogram is a test that measures the electrical activity of the heart. The information obtained from an electrocardiogram can be used to diagnose different types of heart disease. It may be useful for seeing how well the patient is responding to treatment. The extraction of high resolution ECG signals from noisy measurements is among the most tempting open problems of biomedical signal processing. Extracting useful clinical information from the real (noisy) ECG requires reliable signal processing techniques. Numerous methods have been reported to denoise ECG signals based on...

Simulating dynamic plastic continuous neural networks by finite elements

, Article IEEE Transactions on Neural Networks and Learning Systems ; Volume 25, Issue 8 , August , 2014 , Pages 1583-1587 ; ISSN: 2162237X Joghataie, A ; Torghabehi, O. O ; Sharif University of Technology

2014

Abstract

We introduce dynamic plastic continuous neural network (DPCNN), which is comprised of neurons distributed in a nonlinear plastic medium where wire-like connections of neural networks are replaced with the continuous medium. We use finite element method to model the dynamic phenomenon of information processing within the DPCNNs. During the training, instead of weights, the properties of the continuous material at its different locations and some properties of neurons are modified. Input and output can be vectors and/or continuous functions over lines and/or areas. Delay and feedback from neurons to themselves and from outputs occur in the DPCNNs. We model a simple form of the DPCNN where the...

A Deep Learning Approach for Detecting Covid-19 Using the Chest X-Ray Images

, Article Computers, Materials and Continua ; Volume 74, Issue 1 , 2023 , Pages 751-768 ; 15462218 (ISSN) Sadeghi, F ; Rostami, O ; Yi, M. K ; Hwang, S. O ; Sharif University of Technology

Tech Science Press 2023

Abstract

Real-time detection of Covid-19 has definitely been the most widely-used world-wide classification problem since the start of the pandemic from 2020 until now. In the meantime, airspace opacities spreads related to lung have been of the most challenging problems in this area. A common approach to do on that score has been using chest X-ray images to better diagnose positive Covid-19 cases. Similar to most other classification problems, machine learning-based approaches have been the first/most-used candidates in this application. Many schemes based on machine/deep learning have been proposed in recent years though increasing the performance and accuracy of the system has still remained an...

Vertically aligned ZnO@CdS nanorod heterostructures for visible light photoinactivation of bacteria

, Article Journal of Alloys and Compounds ; Vol. 590 , 2014 , pp. 507-513 ; ISSN: 09258388 Zirak, M ; Akhavan, O ; Moradlou, O ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology

2014

Abstract

Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve...

Metallurgical and mechanical properties of underwater friction stir welds of Al7075 aluminum alloy

, Article Journal of Materials Processing Technology ; Volume 262 , 2018 , Pages 239-256 ; 09240136 (ISSN) Rouzbehani, R ; Kokabi, A. H ; Sabet, H ; Paidar, M ; Ojo, O. O ; Sharif University of Technology

Elsevier Ltd 2018

Abstract

Travel speeds between 25–300 mm/min and tool rotational speeds of 800 and 1250 rpm were employed for this study. The microstructure, mechanical properties and fracture surfaces of the joints were studied. Underwater environment and an increase in travel speed significantly increase the precipitates’ volume fraction, reduce the average grain and precipitate sizes of the weld nugget zones. A critical travel speed of 150 mm/min is attained in underwater welds beyond which the average grain sizes remain relatively the same. Average grain and precipitate sizes have linear relationships with the tool rotational and travel speed ratio. Optimum weld strengths of 396 and 360 MPa were obtained in the...

Pre-threaded hole friction stir spot welding of AA2219/PP-C30S sheets

, Article Journal of Materials Processing Technology ; Volume 273 , 2019 ; 09240136 (ISSN) Paidar, M ; Ojo, O. O ; Moghanian, A ; Karami Pabandi, H ; Elsa, M ; Sharif University of Technology

Elsevier Ltd 2019

Abstract

This paper examines the use of pre-fabricated interlocking arms/threading in enhancing the strength of friction stir spot welded hybrid joints of AA2219/PP-C30S polypropylene polymer by varying parameter combination. The process involves the fabrication of a pre-threaded hole on the Al alloy prior to the joining process, and the threading/crest-pitch profile aids mechanical interlocking. The peak temperature, crest-pitch interlocked profiles, microstructural and mechanical properties of the joints were examined. The results show that an increase in the tool rotational speed increases the thickness of the reaction layer (between the Al and the polymer substrates), the shear-tensile load...

Flexible bactericidal graphene oxide–chitosan layers for stem cell proliferation [electronic resource]

, Article Journal of Applied Surface Science ; 15 May 2014, Volume 301, Pages 456–462 Mazaheri, M ; Akhavan, O ; Simchi, A. (Abdolreza) ; Sharif University of Technology

Abstract

Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured...

Superparamagnetic zinc ferrite spinel-graphene nanostructures for fast wastewater purification

, Article Carbon ; Vol. 69 , April , 2014 , pp. 230-238 ; ISSN: 00086223 Meidanchi, A ; Akhavan, O ; Sharif University of Technology

2014

Abstract

Superparamagnetic ZnFe2O4/reduced graphene oxide (rGO) composites containing ZnFe2O4 nanoparticles (with ∼5-20 nm sizes) attached onto rGO sheets (with ∼1 μm lateral dimensions) were synthesized by hydrothermal reaction method. By increasing the graphene content of the composite from 0 to 40 wt%, the size as well as the number of the ZnFe2O4 nanoparticles decreased and the saturated magnetization of the composites reduced from 10.2 to 1.8 emu/g, resulting in lower responses to external magnetic fields. Concerning this, the time needed for 90% separation of ZnFe2O4/rGO (40 wt%) composite from its solution (2 mg/mL in ethanol) was found 60 min in the presence of an external magnetic field (∼1...

Visible light-induced photocatalytic reduction of graphene oxide by tungsten oxide thin films

, Article Applied Surface Science ; Volume 276 , 2013 , Pages 628-634 ; 01694332 (ISSN) Choobtashani, M ; Akhavan, O ; Sharif University of Technology

2013

Abstract

Tungsten oxide thin films (deposited by thermal evaporation or sol gel method) were used for photocatalytic reduction of graphene oxide (GO) platelets (synthesized through a chemical exfoliation method) on surface of the films under UV or visible light of the environment, in the absence of any aqueous ambient at room temperature. Atomic force microscopy (AFM) technique was employed to characterize surface morphology of the GO sheets and the tungsten oxide films. Moreover, using X-ray photoelectron spectroscopy (XPS), chemical state of the tungsten oxide films and the photocatalytic reduction of the GO platelets were quantitatively investigated. The better performance of the sol-gel tungsten...

Ethylbenzene dehydrogenation to styrene over fresh and used commercial catalysts

, Article AIChE Annual Meeting, Conference Proceedings ; 2011 ; 9780816910670 (ISBN) Baghalha, M ; Ebrahimpour, O ; Sharif University of Technology

2011

Abstract

Dehydrogenation of ethylbenzene (EB) to produce styrene (ST) monomer is commercially performed over potassium-promoted iron oxide catalysts. Catalyst deactivation due to coke deposition and loss of potassium is a major operation and economic drawback in this process. To better evaluate the performance change of these catalysts over their life-cycle, dehydrogenation of EB to ST over the fresh and used commercial catalysts was experimentally investigated at temperatures from 590 to 639°C under atmospheric pressure. The fresh and the used catalysts were obtained from a styrene plant. The used catalyst had been continuously operated for two years under severe plant conditions. The catalyst...

Improving the photocatalytic activity of graphene oxide/ZnO nanorod films by UV irradiation

, Article Applied Surface Science ; Volume 371 , 2016 , Pages 592-595 ; 01694332 (ISSN) Rokhsat, E ; Akhavan, O ; Sharif University of Technology

Elsevier 2016

Abstract

Graphene oxide (GO) sheets with a low concentration (∼1 wt%) were deposited on surface of hydrothermally synthesized ZnO nanorod films. The deposited films were heat treated at 450 °C in order to achieve suitable GO/ZnO hybrid thin films for photocatalytic purposes. The photocatalytic activity of the nanocomposite films was investigated based on degradation of methylene blue (MB) dye which is a typical pollutant model. The GO/ZnO hybrid thin films could degrade higher MB (∼90%) than the bare ZnO nanorods (which showed only ∼75% degradation) after 450 min UV irradiation. A further significant improvement (resulting in a nearly complete degradation of MB) was achieved by exposing the GO/ZnO...

Roles of surface coverage increase and re-peening on properties of AISI 1045 carbon steel in conventional and severe shot peening processes

, Article Surfaces and Interfaces ; Volume 11 , 2018 , Pages 82-90 ; 24680230 (ISSN) Maleki, E ; Unal, O ; Sharif University of Technology

Elsevier B.V 2018

Abstract

Surface coverage as one of the most effective parameters of shot peening process has substantial influence on the functionality of the peened component. The aim of this study is to investigate the effects of surface coverage increase on the properties of treated specimens experimentally before and after re-shot peening. Different shot peening treatments from conventional to severe; were performed on the AISI 1045 steel. Microstructural observations and XRD measurements were applied to characterize the circumstance of microstructure changes. In order to investigate the mechanical properties, microhardness profiles were achieved, surface roughness was evaluated and the residual stresses...

Ultrahigh permeable C2N-inspired graphene nanomesh membranes versus highly strained c2n for reverse osmosis desalination

, Article Journal of Physical Chemistry B ; Volume 123, Issue 41 , 2019 , Pages 8740-8752 ; 15206106 (ISSN) Fakhraee, M ; Akhavan, O ; Sharif University of Technology

American Chemical Society 2019

Abstract

The reverse osmosis (RO) desalination capability of hydrogenated and hydroxylated graphene nanomesh membranes (GNMs) inspired by the morphology of carbon nitride (C2N) has been studied by using molecular dynamics simulation. As an advantage, water permeance of the GNMs is found to be several orders of magnitude higher than that of the available RO filters and comparable with highly strained C2N (S-C2N) as follows: 6,6-H,OH > 12-H > S-C2N > 5,5-H,OH > 10-H. The reverse order is found for salt rejection, regardless of S-C2N. The hydrophilic character of the incorporated -OH functional group is believed to be responsible for linking the water molecules in feed and permeate sides via the...