Sharif Digital Repository

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... 

The morphology of the perovskite layer, the effective extraction of the charge carriers, and their transport are the main factors determining the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). In this work, we demonstrated that the geometric and electronic structures of the PSCs could be modified by using a conductive polymer additive in the lead (Pb) halide layer prepared by a two-step deposition method. Polypyrrole (PPy) as a conductive polymer is used in the perovskite layers which could increase the PCE of CH3NH3PbI3-xClx mixed-halide PSCs. By adding an optimized amount of PPy, PCE has been raised from 10.4 to 13.2%. PPy acts as a conductive channel facilitating... 

Catalytic partial oxidation of methane in short residence time rhodium coated monolithic reactors offers an attractive route for syngas production. The plug flow and boundary layer flow approximations are considered as computationally efficient substitutes for the full Navier-Stokes model of the reactor while including detailed heterogeneous and homogeneous chemistry. The one dimensional plug flow model has trivial computational demands but only a limited range of application. The boundary layer model provides an excellent, computationally manageable substitute for the full Navier-Stokes model over a wide range of operating conditions. Using the 38-step elementary surface reaction mechanism... 

Modified forms of WKB expansion of electromagnetic field distribution with variable coefficients are proposed for both TE and TM polarizations. Based on a method similar to the previously reported differential transfer matrix method [1,2], the analytical expressions of those aforementioned coefficients are then derived. The applicability and accuracy of the presented method are shown via some numerical examples. © 2007 EuMA  

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... 

In this work, synthesis of CuIn0.75Ga0.25S2 (CIGS) nanoparticles, the formation of stable dispersion, deposition of high-quality films and, fabrication of thin-film Perovskite solar cells are reported. The stability of nanoparticle ink is crucial in the formation of device-quality films. The chalcogenide-based materials are widely used in thin-film solar cells; in particular, Cu(In,Ga)S2 are used as an absorber and hole transporting layer. In the present study, the nanoparticles of about 20 nm size and bandgap of 1.5 eV are synthesized using a heat-up method. A variety of solvents are used as dispersing media and the stability of the inks is evaluated by precise optical monitoring. We... 

A method for reducing radar cross-section (RCS) of the slot array antenna by utilising the radar absorbing material, while preserving the radiation performance simultaneously, is proposed and discussed. The scheme is based on the implementation of the multilayer frequency selective surface-radar-absorbing material (RAM) capable of operation over a wide frequency band. The use of radar absorbing material on an antenna’s radiation screen causes a change in surface current, resulting in the radiation pattern of the antenna. Therefore, by designing the coating pattern of the radar absorbent material as a substrate and a capacitive patch as a unit cell on the antenna board, the reduction of 19 dB... 

For the first time, the UIO-66, NH2-UIO, and NH2-UIO particles covalently functionalized by Glycidyl Methacrylate (GMA@NH2-UIO), were utilized as the novel functional anti-corrosive fillers. The functionality, high surface area, phase composition, excellent thermal properties as well as chemical stability of the Zr-MOFs were proved by FT-IR, BET, XRD, TGA, and water stability tests, respectively. The smart pH-sensitive controlled-release activity of the corrosion inhibitors (i.e., Zr ions and organic compounds) from the prepared Zr-MOFs was proved by the water stability test of the Zr-MOFs particles in the acidic (pH = 2), neutral (pH = 7.5), and alkaline (pH = 12) solutions containing 3.5... 

In response to the imperfections of current sequence alignment methods, originated from the inherent serialism within their corresponding electrical systems, a few optical approaches for biological data comparison have been proposed recently. However, due to their low performance, raised from their inefficient coding scheme, this paper presents a novel all-optical high-throughput method for aligning DNA, RNA, and protein sequences, named HELIOS. The HELIOS method employs highly sophisticated operations to locate character matches, single or multiple mutations, and single or multiple indels within various biological sequences. On the other hand, the HELIOS optical architecture exploits... 

This research focused on the corrosion resistance and microstructure of hybrid additively manufactured (HAM) samples of AISI 420/CX (420/CX SS) stainless steels. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses as well as the electrochemical noise (EN) technique were used to evaluate the electrochemical behavior of the as-built and heat-treated HAM parts in NaCl solution. The results showed a more protective passive layer formed on the CX SS side. The distribution of Cr-rich M23C6 carbides in matrix of 420 SS side resulted in a lower corrosion resistance compared to the CX SS side. The noise data analysis confirmed an increase in the... 

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... 

The presence of nodules on the surface of cathode copper plates was the most important reason for the failure of the punch of mechanical clinching of copper cathode sheets. This study demonstrated a comprehensive investigation into the nodulation growth of copper cathodes in the electrorefining plant based on metallographic analysis. More than 15 random samples were selected from the top, middle, and bottom of the cathodes produced in the Khatoon Abad copper refinery, Iran. Studies were carried out based on the determination of growth modes including field oriented isolated crystal (FT), basis-oriented reproduction (BR), field-oriented texture (FT), and unoriented dispersion (UD). A scanning... 

In this research, submicron bioactive glass (BG) particles were synthesized by a sol-gel process and were then coated on a 316L stainless steel substrate using an electrophoretic deposition (EPD) technique. Stable suspension of bioactive glass powders in ethanol solvent was prepared by addition of triethanol amine (TEA), which increased zeta potential from 16.5 ± 1.6 to 20.3 ± 1.4 (mv). Thickness, structure and electrochemical behavior of the coating were characterized. SEM studies showed that increasing EPD voltage leads to a coating with more agglomerated particles, augmented porosity and micro cracks. The results of Fourier transformed infrared (FTIR) spectroscopy revealed the adsorption... 

While energy consumption is increasing worldwide due to population growth, the fossil fuels are unstable and exhaustible resources for establishing sustainable life. Using biodegradable compounds present in the wastewater produced in industrial process as a renewable source is an enchanting approach followed by scientists for maintaining a sustainable energy production to vanquish this problem for ulterior generations. In this research, bioelectricity generation with whey degradation was investigated in a two-chamber microbial fuel cell with humic acid as anodic electron mediator and a cathode compartment including combinational electron acceptor. Escherichia coli was able to use the... 

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.%... 

Surface of polycarbonate substrates were activated by atmospheric plasma torch using different gas pressure, distance from the substrates, velocity of the torch and number of treatments. The modifications were analyzed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-vis spectrophotometry. Plasma treatment caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 88° to 18°. The decrease in contact angle was mainly due to oxidation of the surface groups, leading to formation of polar groups with hydrophilic property. XPS results showed an increase in the intensity of... 

Polyurethane elastomer networks were designed and synthesized based on hydroxyl terminated polybutadiene/polypropyleneoxide (HTPB/PPO) mixtures, 2,4-toluene diisocyanate and 1,4-butanediol. Various networks with different molar ratio of HTPB to PPO (0/100, 25/75, 50/50, 75/25 and 100/0) had been prepared. Depending on the length of soft segment, average functionality of polyol mixtures, mechanical and thermal properties of samples were varied. Our observations confirmed that final properties of the networks can be attributed to two synergistic factors: (a) formation of chemical network (crosslinking) and (b) soft segment length. An optimum composition was found. This optimum composition... 

The present article deals with super-swelling behavior of crosslinked homopolymer of 2-acrylamido-2-methylpropane sulfonic acid, poly(AMPS), in binary mixtures of dimethyl sulfoxide (DMSO) and various polar solvents including water, mono-, and polyhydric alcohols, and amide solvents such as N-methyl pyrrolidone. Extraordinary phase transition sequences including a new unusual swelling phenomenon, referred to as "overentrant" swelling, was observed for this polymeric organogel in the solvent/DMSO mixtures. The swelling behaviors were preliminarily explained based on the major interactions involved in the solvation process and dielectric constant of the swelling media. It was established that... 

Seawater, which has been frequently applied in cooling and injection water systems, imposes severe pitting corrosion to mild steel. Addition of green and sustainable inhibitors based on renewable sources is one of the promising methodologies for restricting metal corrosion in chloride-containing electrolytes. In this study, for the first time, from both theoretical and experimental faces, the role of Juglans regia green fruit shell (JRS) extract as a sustainable potent corrosion inhibitor for mild steel was studied. The chemical structure of the JRS extract was deliberated by Fourier transform infrared spectroscopy (FT-IR). By electrochemical techniques including polarization, EIS and... 

Corrosion of steel rebars in concrete can reduce the durability of concrete structures in coastal environments. The corrosion rate of these concrete structures can be reduced by using suitable concrete additives and coating on rebars. This paper investigates the corrosion resistance of steel rebars by the addition of pozzolanic materials including fly ash, silica fume, polypropylene fibers, and industrial 2-dimethylaminoethanol (FerroGard 901) inhibitors to the concrete mixture. Three different types of rebars including mild steel rebar st37, and two stainless steel reinforcements, AISI 304 and AISI 316, were used. Various types of primer and coating including alkyd based primer, hot-dip...