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    Microstructure, mechanical properties, corrosion behavior and cytotoxicity of Mg-Zn-Al-Ca alloys as biodegradable materials

    , Article Journal of Alloys and Compounds ; Vol. 607 , 2014 , Pages 1-10 ; ISSN: 09258388 Homayun, B ; Afshar, A ; Sharif University of Technology
    Abstract
    Recently, considerable attentions have been paid to alloy Mg-4Zn-0.2Ca for biomedical applications due to its suitable biocompatibility and acceptable mechanical properties. In this work, the effects of the addition of different amounts of Al on microstructure, mechanical properties, degradation behavior, and biocompatibility of this alloy were investigated. The corrosion behaviors of the alloys were investigated through polarization tests, chronoamperometry analysis, immersion tests, and EIS experiments. The mechanical properties were analyzed by using tensile tests and compression tests. The results showed that the addition of Al up to 3 wt.% considerably modifies the degradation behaviors... 

    Corrosion resistance enhancement of Ni-P-nano SiO2 composite coatings on aluminum

    , Article Applied Surface Science ; Vol. 303 , 2014 , Pages 125-130 ; ISSN: 01694332 Sadreddini, S ; Afshar, A ; Sharif University of Technology
    Abstract
    In this study, the influences of different concentrations of SiO 2 nano sized particles in the bath on deposition rate, surface morphology and corrosion behavior of Ni-P-SiO2 Composite coatings were investigated. The deposition rate of coating was influenced by incorporation of SiO2 particles. The microstructure was investigated with field emission scanning electron microscopy (FESEM). The amount of SiO 2 was examined by Energy Dispersive Analysis of X-Ray (EDX) and amount of SiO2 nanoparticles co-deposited reached a maximum value at 4.5 %wt. Corrosion behavior of coated aluminum was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results... 

    Microstructure-corrosion resistance relationship of Direct and Pulse Current electrodeposited Zn-TiO2 nanocomposite coatings

    , Article Ceramics International ; Vol. 41, issue. 1 , 2014 , pp. 217-224 ; ISSN: 02728842 Sajjadnejad, M ; Ghorbani, M ; Afshar, A ; Sharif University of Technology
    Abstract
    Zinc-TiO2 nano-composite coatings were synthesized by Direct Current (DC) and Pulse Current (PC) electrodeposition techniques. The effects of the plating parameters on the microstructure, codeposition percentage of TiO2 and corrosion behavior were investigated. The coatings morphology presents hexagonal grains perpendicularly oriented to the surface. Under DC conditions, TiO2 content of the coatings decreased with increasing TiO2 concentration of the electrolyte. Increasing applied current and TiO2 concentration in the bath leads to a fine microstructure with corrosion currents as low as 2.7 μA/cm2. Under PC conditions, incorporation rate of nanoparticles tends to increase with increasing... 

    Double layer bioglass-silica coatings on 316L stainless steel by sol-gel method

    , Article Ceramics International ; Volume 40, Issue 1, Part A , January 2014 , Pages 993–1000 Pourhashem, S ; Afshar, A ; Sharif University of Technology
    Abstract
    The application of bioglass coatings on metallic implants provides link between bone and materials and prevents corrosion of metallic implants in body fluid. Therefore, in this research, 45S5 bioglass-silica coatings on 316L stainless steel were prepared by the sol-gel method and were characterized by different techniques. According to X-ray diffraction (XRD) results, by sintering 45S5 bioglass at 600 C for 5 h, coatings containing both amorphous phase and Na2Ca2Si3O9 crystalline phase were obtained. Scanning electron microscopy (SEM) results showed that coatings prepared via appropriate sol aging and substrate preparations are crack-free. Potentiodynamic polarization tests in simulated body... 

    Tantalum electrodes modified with well-aligned carbon nanotube-au nanoparticles: application to the highly sensitive electrochemical determination of cefazolin

    , Article Applied Biochemistry and Biotechnology ; Volume 173, Issue 6 , July 2014 , Pages 1511-1528 Fayazfar, H ; Afshar, A ; Dolati, A ; Sharif University of Technology
    Abstract
    Carbon nanotube/nanoparticle hybrid materials have been proven to exhibit high electrocatalytic activity suggesting broad potential applications in the field of electroanalysis. For the first time, modification of Ta electrode with aligned multi-walled carbon nanotubes/Au nanoparticles introduced for the sensitive determination of the antibiotic drug, cefazolin (CFZ). The electrochemical response characteristics of the modified electrode toward CFZ were investigated by means of cyclic and linear sweep voltammetry. The modified electrode showed an efficient catalytic activity for the reduction of CFZ, leading to a remarkable decrease in reduction overpotential and a significant increase of... 

    Electrophoretic deposition of bioactive glass coating on 316L stainless steel and electrochemical behavior study

    , Article Applied Surface Science ; Volume 258, Issue 24 , 2012 , Pages 9832-9839 ; 01694332 (ISSN) Mehdipour, M ; Afshar, A ; Mohebali, M ; Sharif University of Technology
    Elsevier  2012
    Abstract
    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... 

    Photoactive and self-cleaning TiO 2-SiO 2 thin films on 316L stainless steel

    , Article Thin Solid Films ; Volume 520, Issue 20 , 2012 , Pages 6355-6360 ; 00406090 (ISSN) Boroujeny, B. S ; Afshar, A ; Dolati, A ; Sharif University of Technology
    Abstract
    In this study, TiO 2-SiO 2 nanocomposite films with different amounts of SiO 2 were prepared by sol-gel process and were coated onto stainless steel 316L. The effect of addition of various amount of SiO 2 in the precursor solution on the photocatalysis, photo-generated hydrophilicity and self-cleaning property of TiO 2 thin films was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements and UV spectroscopy. In the tested ranges of SiO 2 content and sintering temperature, the highest photocatalytic activity and self-cleaning property were observed in the 15 mol% SiO 2 sample sintered at 750 °C. Addition of less than 30 mol% SiO 2 had a... 

    A study of the electrophoretic deposition of bioactive glass-chitosan composite coating

    , Article Ceramics International ; Volume 38, Issue 1 , January , 2012 , Pages 471-476 ; 02728842 (ISSN) Mehdipour, M ; Afshar, A ; Sharif University of Technology
    2012
    Abstract
    Bioactive glass is coated on implant's surface to improve corrosion resistance and osseointegration, when placed in the body. Bioactive glass particles were synthesized through a sol-gel process and deposited along with chitosan to form a composite coating on a stainless steel substrate using electrophoretic deposition technique. Stable suspensions of chitosan-bioactive glass were prepared using bioactive glass particles (<1 μm) and 0.5 g/l chitosan solution. The influence of ethanol-water ratio on deposition yield was investigated. For all process conditions, best results were achieved with suspension of 30 vol% water in ethanol-water containing 2 g/l bioactive glass. FTIR studies showed... 

    Al2O3/Si3N4 nanocomposite coating on aluminum alloy by the anodizing route: Fabrication, characterization, mechanical properties and electrochemical behavior

    , Article Ceramics International ; 2016 ; 02728842 (ISSN) Mohammadi, I ; Afshar, A ; Ahmadi, S ; Sharif University of Technology
    Abstract
    An Al2O3/Si3N4 nanocomposite coating was successfully fabricated on commercial aluminum alloy. Hardness measurements, polarization and electrochemical impedance spectroscopy (EIS) were employed to study the mechanical and corrosion behaviors of the coatings. Field-Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) were utilized to characterize the surface morphology and phase composition of the coatings. Also, coatings abrasive wear properties were evaluated with a modified ASTM G105 standard. FE-SEM image, EDS and XRD analysis revealed the presence of Si3N4 in the coating. Furthermore, the results showed hardness of... 

    Zn-Ni Electrophosphating on galvanized steel using cathodic and anodic electrochemical methods

    , Article Surface and Coatings Technology ; January , 2015 ; 02578972 (ISSN) Darband, G. B ; Afshar, A ; Aliabadi, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn-Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

    Electrodeposition of various au nanostructures on aligned carbon nanotubes as highly sensitive nanoelectrode ensembles

    , Article Journal of Materials Engineering and Performance ; Volume 24, Issue 5 , May , 2015 , Pages 2005-2015 ; 10599495 (ISSN) Fayazfar, H ; Afshar, A ; Dolati, A ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition. Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Facile template-free electrochemical routes were then developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, rod, sheet, and cabbage onto the aligned MWCNTs at room temperature. Especially, among all the synthesis methods for Au nanocrystals, this is the first report using electrochemical technique to synthesize wide variety... 

    Experimental design for optimizing the corrosion resistance of pulse reverse electrodeposited graphene oxide thin film

    , Article Journal of Solid State Electrochemistry ; Volume 19, Issue 5 , May , 2015 , pp 1367–1380 ; 14328488 (ISSN) Yaghoubinezhad, Y ; Afshar, A ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    In this study, linear polarization resistance (LPR) of pulse reverse electrodeposited graphene oxide (PREGO) coating is optimized by design of experiments approach (central composite design). Pulse current density (i), cathodic (Tc) and anodic (Ta) pulse durations, and total electrodeposition time (Tt) are selected as the substantial factors. The best prediction model proposes a definitive linear relation without any significant interaction of the LPR by analysis of variance. The desirable value of LPR was predicted equal to 5358 Ω cm2, obtaining at the pulse current density of 235.62 mA cm−2, Ta of 7.75 ms, Tc equal to 3.25 ms (f = 100 Hz), and Tt of approximately 225 s. Appearance of the... 

    Design of experiments for pulse reverse electrodeposition of graphene oxide toward hydrogen evolution reaction

    , Article ECS Journal of Solid State Science and Technology ; Volume 4, Issue 3 , 2015 , Pages M7-M17 ; 21628769 (ISSN) Yaghoubinezhad, Y ; Afshar, A ; Sharif University of Technology
    Electrochemical Society Inc  2015
    Abstract
    Surface active sites of pulse reverse electrodeposited graphene oxide (PREGO) coating is optimized by design of experiments approach (central composite design). Applied current density (i), cathodic (Tc) and anodic (Ta) pulse durations, and total electrodeposition time (Tt) are selected to interpret the hydrogen evolution reaction (HER). The analyses of variance (ANOVA) are carried out on the outcomes of the designed experiments. A definitive linear relationship without any significant interaction was introduced as the best prediction model. Moreover, the results indicating the Ta and Tc are the most significant model terms. The best desirable value of the exchange charge on the cyclic... 

    Modification of nanostructured anodized aluminum coatings by pulse current mode

    , Article Surface and Coatings Technology ; Volume 278 , 2015 , Pages 48-55 ; 02578972 (ISSN) Mohammadi, I ; Afshar, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    In this study, the effects of pulse current mode on corrosion resistance and mechanical properties of anodized coatings were explored. Thickness and hardness measurements, polarization and electrochemical impedance spectroscopy were employed to take mechanical and corrosion behaviors of the anodized coatings into consideration. Also, field-emission scanning electron microscopy (FE-SEM) was utilized to characterize the surface morphology of the coatings. It was shown that in short anodizing times, coating thickness is controlled by the heat concentrated on coating. Although at prolonged anodizing times, the coating thickness is affected by average current density. Hardness measurements showed... 

    Effects of zirconia content on characteristics and corrosion behavior of hydroxyapatite/ZrO2 biocomposite coatings codeposited by electrodeposition

    , Article Surface and Coatings Technology ; Volume 262 , January , 2015 , Pages 166-172 ; 02578972 (ISSN) Shojaee, P ; Afshar, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    HAp and HAp/ZrO2 composite coatings were successfully electrodepesited on 316L stainless steel substrates in the solutions containing ZrO2 particles at different concentrations. The effects of ZrO2 content on characteristics of the coatings were investigated using X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM) and bonding strength test. Polarization and electrochemical impedance spectroscopy measurements were carried out in order to evaluate corrosion behavior of the coatings. In-vitro test in SBF and further SEM observations were performed to examine bioactivity of the coatings. HAp/ZrO2 composite coatings showed better... 

    Effect of current density on DC electrochemical phosphating of stainless steel 316

    , Article Surface and Coatings Technology ; Volume 205, Issue 7 , December , 2010 , Pages 2302-2306 ; 02578972 (ISSN) Oskuie, A. A ; Afshar, A ; Hasannejad, H ; Sharif University of Technology
    2010
    Abstract
    In this study, tri-cation phosphate coating of zinc, calcium and iron was applied electrochemically to stainless steel 316 substrates. Cathodic current was used as an accelerator for the phosphating process. The effects of current density on the microstructures of the coatings and the time necessary for the reduction of the oxide layer have been established. For this purpose, analyses such as chronopotentiometery, SEM, EDS and linear polarization were carried out. Results indicated that higher electrophosphating current densities result in finer crystal size of the coating. This effect is detrimental to the quality of the layer. In addition, chemical analyses of the layer revealed that the... 

    Effect of treatment time and temperature on microstructure and corrosion behavior of Zn-Ni electrophosphate coating

    , Article Journal of Alloys and Compounds ; Volume 688 , 2016 , Pages 596-604 ; 09258388 (ISSN) BaratiDar Darband, G ; Afshar, A ; Rabani, M ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    In this study, the effect of phosphating time and temperature on microstructure and corrosion behavior of Zn-Ni electrophosphate coating with a galvanized steel as a substrate, were investigated. SEM and X-ray diffraction methods were used for investigation the microstructure and phase analysis, respectively. And immersion test, potentiodynamic polarization test, and Electrochemical Impedance Spectroscopy tests were used for the study of corrosion behavior. The results of this study indicated that the best coating morphology is obtained in the range between 20 and 30 min and 40–50° C. Moreover, results of corrosion studies showed that the corrosion mechanism is under diffusion control due to... 

    Zn–Ni electrophosphating on galvanized steel using cathodic and anodic electrochemical methods

    , Article Surface and Coatings Technology ; Volume 306 , 2016 , Pages 497-505 ; 02578972 (ISSN) Barati Darband, Gh ; Afshar, A ; Aliabadi, A ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn–Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

    Effect of pulse current parameters on the mechanical and corrosion properties of anodized nanoporous aluminum coatings

    , Article Materials Chemistry and Physics ; Volume 183 , 2016 , Pages 490-498 ; 02540584 (ISSN) Mohammadi, I ; Ahmadi, Sh ; Afshar, A ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    In this study, the effects of pulse current parameters on corrosion resistance and mechanical properties of anodized coatings were evaluated. Hardness measurements, polarization and electrochemical impedance spectroscopy tests were employed to investigate the mechanical properties and corrosion behavior of these coatings. Also, field emission scanning electron microscopy (FE-SEM) was used to analyze the surface morphology and microstructure of the coatings. It was found that the properties of anodized coatings were dependent on various parameters, among which, time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were optimized. Analysis of Variance... 

    Analyzing the Impact of Zineband Ziram As Booster Biocides in Antifouling Paints

    , Article Journal of Materials and Environmental Science ; Volume 7, Issue 4 , 2016 , Pages 1436-1444 ; 20282508 (ISSN) Karsaz, A ; Afshar, A ; Sharif University of Technology
    Mohammed Premier University  2016
    Abstract
    Maritime structures such as waterfronts, offshore platforms and hulks all face different maritime sediments. There are different methods to prevent the growth of organic and non-organic material on humid surfaces, but the utilization of antifouling paints has had the most efficiency. The growth of these maritime pollutions has been stopped on hulks by the antifouling paints. Ever since the nineteenth century, antifouling paints have been utilized with different mechanisms and the most important one was the TBT self-polishing paints that were banned in 2003 by the International Marine Organization (IMO) because of the high pollution it creates in the environment. There have been many efforts...