Changiz Dehghanian - Academia.edu (original) (raw)

Papers by Changiz Dehghanian

The effects of intercritical annealing and subcritical tempering on the mechanical properties and... more The effects of intercritical annealing and subcritical tempering on the mechanical properties and corrosion resistance of mild steel were studied. It was revealed that intercritical annealing followed by quenching resulted in the development of a ferritic-martensitic dual phase (DP) microstructure with high tensile strength, disappearance of the yield-point phenomenon, superior work-hardening behavior, and decreased corrosion resistance. Subsequent tempering of the intercritically annealed steel resulted in the formation of carbide particles in a tempered martensitic microstructure, which led to the decline of the strength and hardness, reappearance of the yield-point elongation, and enhanced corrosion resistance. Accordingly, this work demonstrated the possibility of controlling the mechanical properties and corrosion resistance of commercial mild steels by simple heat treatments.

In this research, ceramic oxide coatings were produced on Ti in the different electrolytes of Alu... more In this research, ceramic oxide coatings were produced on Ti in the different electrolytes of Aluminate and carbonate base by micro-arc oxidation. This process was conducted under Constant voltage condition. The effect of KOH and NaF in aluminate base solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was examined by Potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the voltage breakdown had a significant effect on the form and properties of coatings. Coatings obtained from Aluminate-potass base solution had lower breakdown voltage, higher surface homogeneity and a better corrosion resistance than carbonate base solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. ...

ییازریم دیجم ، نایناقهد زیگنچ * یژرولاتم و داوم یسدنهم هدکشناد ، ینف هدکشناد سیدرپ ، نارهت هاگشنا... more ییازریم دیجم ، نایناقهد زیگنچ * یژرولاتم و داوم یسدنهم هدکشناد ، ینف هدکشناد سیدرپ ، نارهت هاگشناد ناریا ،نارهت ،نارهت ، رات ی هچخ هلاقم : تبث لوا ی ه : 22 / 22 / 9991 رد ی تفا ةخسن حلاصا هدش : 99 / 25 / 9999 ذپ ی شر عطق ی : 22 / 27 / 9999 کچ ی د ه قحت رد ی ق شور زا هدافتسا اب ،رضاح اه ی حم اب راگزاس و نازرا ی ط ز ی تس ، نفارگ ( دیسکا GO ) ، یور موف سکا ی د ن ی لک بوسر ، دش یناشن هقرو ،سپس . اه ی کزان GO ، شور اب اه ییایمیشورتکلا فلتخم ی هخرچ یرتماتلو یا ( CV ،) یرتمورپمآونورک و ،یرتمویسناتپونورک دندش ایحا . شور ریثأت سر فلتخم یاه بو یناشن زین صوصخ رب ی تا راتخاس ی ، ژولوفروم ینزاخربا و ی هیلا کزان ERGO ، هعشا شارپ زا هدافتسا اب ا ی سک ( XRD م ،) ی پوکسورک نورتکلا ی یشبور ( SEM ط ،) ی ف جنس ی ،نامار هخرچ یرتماتلو یا ناولاگ و و تاتسا ی ک ژراشد و ژراش ( GCD ) ، سررب دروم ی .تفرگ رارق لیکشت

International Journal of Hydrogen Energy, 2018

Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical ... more Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical dealloying of copper from NieCu porous foam, highly nanoporous nickel and nickel oxide is fabricated on the copper surface. Electrochemically reduced graphene oxide (ERGO) is loaded on the NieNiO foam as high-performance electrodes for supercapacitors through pulsed galvanostatic reduction of drop casted graphene oxide nanosheets at different duty cycles and frequencies. Surface morphology and composition of fabricated ERGO/NieNiO foam composite electrodes are characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Raman Spectroscopy. Electrochemical impedance spectroscopy (EIS) measurements, galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) are carried out to study the electrochemical behavior of ERGO/NieNiO foam electrodes. From structural and electrochemical characterizations, optimized parameters for pulse duty cycle and frequency were found to be 10% and 1000 Hz, respectively. As a result, the ERGO/NieNiO foam film (i c ¼ À10 mA/ cm 2 , f ¼ 1000 Hz and DC ¼ 10%) provides a specific capacitance of 2298 F/g in 1 M KOH at a current density of 1 A/g. Stability study of fabricated film represents a long cycling life up to 4000 cycles with 0.7% decay in specific capacitance at the high current density of 20 A/g in the potential range of 0e0.6 V vs. saturated calomel electrode (SCE).

Acta Metallurgica Slovaca, 2018

Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used f... more Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used for fabrication of nanostructural coatings. This process starts with the appearance of some sparks on the surface and finally by the formation of plasma envelope around the sample, particles and free radicals bombard the surface and diffusion takes place into the work-piece. In this paper, the effect of frequency (500, 1000 and 10000 Hz) as pulse parameters on properties of nitrocarburized layers deposited on AISI 1045 steel were investigated. The analytical characteristics of the coating were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The corrosion behavior of coatings was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. Moreover, the microhardness and wear resistance of coated samples were also studied. The results indicated that applying nitrocarburized layer in all...

Acta Metallurgica Slovaca, 2018

The applicability of nickel-copper metallic foams as a current collector was investigated for sup... more The applicability of nickel-copper metallic foams as a current collector was investigated for supercapacitor. A comprehensive characterization of Ni-Cu based foam was studied and the analysis of their structural, chemical, and electrochemical properties was evaluated. Structural characteristics and electrochemical methods were used to examine the surface morphology, and surface-chemical composition of the materials. The foams deposited at the time deposition of 180s exhibited dual-porosities (macro and mesopores) with pores ranging from13 to16 μm and the branch size ranged from 25 to 50 nm. Ni-Cu foam electrodes are employed as current collector for supercapacitor. Their usefulness as current collector was evaluated by well-defined experimental conditions using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge and discharge (GCD) techniques. The outcome of these experiments demonstrated that the Ni-Cu foams which was synthesized at the ti...

Surface and Coatings Technology, 2016

Effect of duty cycle and electrolyte additive on photocatalytic performance of TiO 2-ZrO 2 compos... more Effect of duty cycle and electrolyte additive on photocatalytic performance of TiO 2-ZrO 2 composite layers prepared on CP Ti by micro arc oxidation method.

Geometrical discontinuities resulting from localized pitting can lead to substantial degradation ... more Geometrical discontinuities resulting from localized pitting can lead to substantial degradation of mechanical properties of steel structures especially in marine environments. This effect is usually evaluated in terms of the reduced section thickness associated with pit geometry which lowers the load carrying capacity of the structure. In this research, the effects of depth, spacing, and distribution of artificially produced, pit like, discontinuities on tensile ductility and fracture behavior of a structural steel have been investigated. Simulated pit distributions were produced on the gage sections of flat tensile specimens using mechanical drilling. A series of tensile tests were performed on specimens with pit area percents from 4 to 64% and various pith depths and spacing. It was found that fracture strain was substantially reduced at low pit area percents, but tended to partially recover at high pit area percents. This effect was further intensified by increasing pith depth. Furthermore, a change in the fracture surface orientation and formation of multiple secondary cracks were noted in pit distributions with higher stress concentration factors. SEM fractographs are presented to characterize the fracture surface morphologies. The overall findings are discussed in terms of mutual interaction of multiple stress concentration sites, triaxial stress state, and strain localization.

Scientia Iranica

The Plasma Electrolytic Saturation (PES) technique is a relatively new process, which uses a high... more The Plasma Electrolytic Saturation (PES) technique is a relatively new process, which uses a high DC voltage power supply with a related organic electrolyte. Within the phenomenological model, the mechanism of the nanocrystalline coating formation processes has been developed to clarify the controlling variations of the procedure. Within the informative model, a feedback parameter for the formed surface state estimation was established. This parameter is the power spectral density of the current. The voltage versus current characteristics of the treatment within the plasma region depend on the main electrolysis conditions, such as current density, electrolyte concentration and agitation rate. Application of the control algorithm of the parameters could increase the e ciency of the plasma electrolytic saturation and nanocrystalline coating formation. In this process, the electric eld strength, \E", within the surface region reached a value of between 106 and 108 V/m, which was su cient for initiation of ionization processes in the vapor envelope. The ionization phenomena initially appeared as a quick sparking in scattered gaseous bubbles and then transformed into a uniform glow distributed throughout the vapor plasma envelope. Because of the hydrodynamic stabilization of the vapor envelope in the region of 180-210 V, the current dropped and the glow discharge transformed into intensive arcing, accompanied by a characteristic low-frequency acoustic emission.

RSC Advances, 2015

In this study, the effect of curing on the structure and protective performance of an eco-friendl... more In this study, the effect of curing on the structure and protective performance of an eco-friendly silane sol–gel coating on stainless steel 304L was investigated using electrochemical methods as well as surface analysis.

Progress in Natural Science: Materials International, 2012

NiP electroless coating was applied on low carbon steel with the incorporation of different amoun... more NiP electroless coating was applied on low carbon steel with the incorporation of different amounts of nano Al 2 O 3 powder (ranging from 3 g/l to 30 g/l) in electroless bath. Corrosion properties and microstructures of the coating were studied. The dispersion stability of alumina colloidal particles stabilized by polymeric (non-ionic) surfactants in an electroless bath was also investigated. The surface morphology and the relevant structure were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Corrosion behavior of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results showed that increasing alumina concentration not only changed the surface morphology, but also promoted the corrosion resistance. Addition of surfactants has an indirect effect on the amount of the incorporated particles. Meanwhile, in the presence of surfactant, corrosion resistance of NiP coating containing even a small quantity of alumina was improved since a stabilized bath was obtained.

Plasma Processes and Polymers, 2007

... Correspondence: Peyman Taheri, School of Metallurgy and Materials ... The authors wish to exp... more ... Correspondence: Peyman Taheri, School of Metallurgy and Materials ... The authors wish to express their sincere appreciation to Dr. Mohseni and Dr. Shayegan at School of Electrical Engineering, University of Tehran who provided the power supply for the present work. ...

Plasma Processes and Polymers, 2009

In this work, the feasibility of a plasma electrolytic carburizing (PEC) treatment on AISI H13 st... more In this work, the feasibility of a plasma electrolytic carburizing (PEC) treatment on AISI H13 steel using an aqueous solution of C3H5(OH)3, and NaOH was investigated. The substrate samples were biased cathodically to a 20 kW pulsed DC power supply with a variable voltage. The formation of hard carbon‐rich layer on the surface of the treated samples was confirmed by XRD analysis. Metallographic and SEM studies revealed that a uniform and compact nanocrystalline carbon‐rich layer was firmly stuck to the surface of the samples, and no cracks were observed between the carburized layer and the substrate. The coating mechanical performances were evaluated using microhardness tests. The microhardness of the carbon‐rich layer on the substrate was 866 HV, while the hardness of the substrate was 210 HV. Pin‐on‐disk abrasion tests were conducted to evaluate the surface wear resistance. Although all treated samples manifested a magnificent increase in wear resistance, the results showed differ...

Journal of Solid State Electrochemistry, 2010

Abstract Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposi... more Abstract Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry and scanning electron microscopy. The electrochemical ...

Journal of Applied Electrochemistry, 2010

Effect of grain size reduction on the electrochemical and corrosion behavior of iron of different... more Effect of grain size reduction on the electrochemical and corrosion behavior of iron of different grain sizes (32-320 nm) produced by direct and pulsed current electrodeposition was characterized using Tafel polarization curves and electrochemical impedance spectroscopy (EIS). The grain size of deposits was determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The most intensive first-order peak (110) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The electrochemical tests were carried out in electrolyte 30 mg L-1 NaCl ? 70 mg L-1 Na 2 SO 4 ? 250 mg L-1 NaNO 2 aqueous solution. It was found that the corrosion potential and corrosion current density significantly changed as the microstructure morphology was changed. Results obtained from electrochemical tests suggested that the inhibition effect and corrosion protection of sodium nitrite inhibitor in nearneutral aqueous solutions increased as the grain size decreased from submicrocrystalline to nanocrystalline. This was attributed to the excess free energy, and concomitantly the increased number of the active sites caused by higher grain boundary and triple junction content in the nanocrystalline surface, which provides sites for electrochemical activity, and effect of sodium nitrite, was more pronounced.

International Journal of Materials Research, 2010

Résumé/Abstract The effect of grain size reduction on the corrosion inhibitor adsorption of nanoc... more Résumé/Abstract The effect of grain size reduction on the corrosion inhibitor adsorption of nanocrystalline Fe produced by pulse electrodeposition was characterized using tafel polarization curves and electrochemical impedance spectroscopy. The grain size of a ...

Corrosion, 1983

Corrosion of steel in concrete is a problem because of the presence of chloride ions at the metal... more Corrosion of steel in concrete is a problem because of the presence of chloride ions at the metal-concrete interface. The chloride ion is introduced as a contaminant in the mix or from the sources such as deicing salt or seawater. The electrochemistry of steel in this system is not well defined. This paper presents the polarization curves for steel in Type I and V portland cement with various salt contents. The degree of corrosiveness of steel in these two portland cement concretes was evaluated. Laboratory-dry and water-saturated concrete samples were used to determine the electrochemical behavior of steel at the presence of chloride ions in these conditions. The anodic polarization curves indicated that the steel passivates in the concrete sample of Type I portland cement with the salt content up to 0.1 %, but the passivity of steel was maintained up to 0.5% in Type V portland cement. (The samples had been exposed to distilled water for 90 days after removal from a water cabinet)....

Corrosion, 2009

The effects of two important factors, namely concentration and hydrodynamics on the inhibition ef... more The effects of two important factors, namely concentration and hydrodynamics on the inhibition efficiency of calcium gluconate (C12H22CaO14), were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy tests. Results showed that calcium gluconate was capable of inhibiting the corrosion of mild steel in simulated cooling water. The inhibition efficiency of calcium gluconate was increased by increasing its concentration and decreased by increasing water circulation velocity due to the adsorption process, which leads to the formation of a protective layer with a greater charge-transfer resistance on the metal surface. The hydrodynamic effect seems to promote the adsorption of calcium gluconate on the metal surface, which was confirmed by the fitting of the Langmuir adsorption isotherm.

Corrosion Science, 2014

ABSTRACT

The effects of intercritical annealing and subcritical tempering on the mechanical properties and... more The effects of intercritical annealing and subcritical tempering on the mechanical properties and corrosion resistance of mild steel were studied. It was revealed that intercritical annealing followed by quenching resulted in the development of a ferritic-martensitic dual phase (DP) microstructure with high tensile strength, disappearance of the yield-point phenomenon, superior work-hardening behavior, and decreased corrosion resistance. Subsequent tempering of the intercritically annealed steel resulted in the formation of carbide particles in a tempered martensitic microstructure, which led to the decline of the strength and hardness, reappearance of the yield-point elongation, and enhanced corrosion resistance. Accordingly, this work demonstrated the possibility of controlling the mechanical properties and corrosion resistance of commercial mild steels by simple heat treatments.

In this research, ceramic oxide coatings were produced on Ti in the different electrolytes of Alu... more In this research, ceramic oxide coatings were produced on Ti in the different electrolytes of Aluminate and carbonate base by micro-arc oxidation. This process was conducted under Constant voltage condition. The effect of KOH and NaF in aluminate base solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was examined by Potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the voltage breakdown had a significant effect on the form and properties of coatings. Coatings obtained from Aluminate-potass base solution had lower breakdown voltage, higher surface homogeneity and a better corrosion resistance than carbonate base solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. ...

ییازریم دیجم ، نایناقهد زیگنچ * یژرولاتم و داوم یسدنهم هدکشناد ، ینف هدکشناد سیدرپ ، نارهت هاگشنا... more ییازریم دیجم ، نایناقهد زیگنچ * یژرولاتم و داوم یسدنهم هدکشناد ، ینف هدکشناد سیدرپ ، نارهت هاگشناد ناریا ،نارهت ،نارهت ، رات ی هچخ هلاقم : تبث لوا ی ه : 22 / 22 / 9991 رد ی تفا ةخسن حلاصا هدش : 99 / 25 / 9999 ذپ ی شر عطق ی : 22 / 27 / 9999 کچ ی د ه قحت رد ی ق شور زا هدافتسا اب ،رضاح اه ی حم اب راگزاس و نازرا ی ط ز ی تس ، نفارگ ( دیسکا GO ) ، یور موف سکا ی د ن ی لک بوسر ، دش یناشن هقرو ،سپس . اه ی کزان GO ، شور اب اه ییایمیشورتکلا فلتخم ی هخرچ یرتماتلو یا ( CV ،) یرتمورپمآونورک و ،یرتمویسناتپونورک دندش ایحا . شور ریثأت سر فلتخم یاه بو یناشن زین صوصخ رب ی تا راتخاس ی ، ژولوفروم ینزاخربا و ی هیلا کزان ERGO ، هعشا شارپ زا هدافتسا اب ا ی سک ( XRD م ،) ی پوکسورک نورتکلا ی یشبور ( SEM ط ،) ی ف جنس ی ،نامار هخرچ یرتماتلو یا ناولاگ و و تاتسا ی ک ژراشد و ژراش ( GCD ) ، سررب دروم ی .تفرگ رارق لیکشت

International Journal of Hydrogen Energy, 2018

Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical ... more Through electrodeposition, controlling hydrogen evolution reaction and selective electrochemical dealloying of copper from NieCu porous foam, highly nanoporous nickel and nickel oxide is fabricated on the copper surface. Electrochemically reduced graphene oxide (ERGO) is loaded on the NieNiO foam as high-performance electrodes for supercapacitors through pulsed galvanostatic reduction of drop casted graphene oxide nanosheets at different duty cycles and frequencies. Surface morphology and composition of fabricated ERGO/NieNiO foam composite electrodes are characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Raman Spectroscopy. Electrochemical impedance spectroscopy (EIS) measurements, galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) are carried out to study the electrochemical behavior of ERGO/NieNiO foam electrodes. From structural and electrochemical characterizations, optimized parameters for pulse duty cycle and frequency were found to be 10% and 1000 Hz, respectively. As a result, the ERGO/NieNiO foam film (i c ¼ À10 mA/ cm 2 , f ¼ 1000 Hz and DC ¼ 10%) provides a specific capacitance of 2298 F/g in 1 M KOH at a current density of 1 A/g. Stability study of fabricated film represents a long cycling life up to 4000 cycles with 0.7% decay in specific capacitance at the high current density of 20 A/g in the potential range of 0e0.6 V vs. saturated calomel electrode (SCE).

Acta Metallurgica Slovaca, 2018

Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used f... more Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used for fabrication of nanostructural coatings. This process starts with the appearance of some sparks on the surface and finally by the formation of plasma envelope around the sample, particles and free radicals bombard the surface and diffusion takes place into the work-piece. In this paper, the effect of frequency (500, 1000 and 10000 Hz) as pulse parameters on properties of nitrocarburized layers deposited on AISI 1045 steel were investigated. The analytical characteristics of the coating were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The corrosion behavior of coatings was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. Moreover, the microhardness and wear resistance of coated samples were also studied. The results indicated that applying nitrocarburized layer in all...

Acta Metallurgica Slovaca, 2018

The applicability of nickel-copper metallic foams as a current collector was investigated for sup... more The applicability of nickel-copper metallic foams as a current collector was investigated for supercapacitor. A comprehensive characterization of Ni-Cu based foam was studied and the analysis of their structural, chemical, and electrochemical properties was evaluated. Structural characteristics and electrochemical methods were used to examine the surface morphology, and surface-chemical composition of the materials. The foams deposited at the time deposition of 180s exhibited dual-porosities (macro and mesopores) with pores ranging from13 to16 μm and the branch size ranged from 25 to 50 nm. Ni-Cu foam electrodes are employed as current collector for supercapacitor. Their usefulness as current collector was evaluated by well-defined experimental conditions using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge and discharge (GCD) techniques. The outcome of these experiments demonstrated that the Ni-Cu foams which was synthesized at the ti...

Surface and Coatings Technology, 2016

Effect of duty cycle and electrolyte additive on photocatalytic performance of TiO 2-ZrO 2 compos... more Effect of duty cycle and electrolyte additive on photocatalytic performance of TiO 2-ZrO 2 composite layers prepared on CP Ti by micro arc oxidation method.

Geometrical discontinuities resulting from localized pitting can lead to substantial degradation ... more Geometrical discontinuities resulting from localized pitting can lead to substantial degradation of mechanical properties of steel structures especially in marine environments. This effect is usually evaluated in terms of the reduced section thickness associated with pit geometry which lowers the load carrying capacity of the structure. In this research, the effects of depth, spacing, and distribution of artificially produced, pit like, discontinuities on tensile ductility and fracture behavior of a structural steel have been investigated. Simulated pit distributions were produced on the gage sections of flat tensile specimens using mechanical drilling. A series of tensile tests were performed on specimens with pit area percents from 4 to 64% and various pith depths and spacing. It was found that fracture strain was substantially reduced at low pit area percents, but tended to partially recover at high pit area percents. This effect was further intensified by increasing pith depth. Furthermore, a change in the fracture surface orientation and formation of multiple secondary cracks were noted in pit distributions with higher stress concentration factors. SEM fractographs are presented to characterize the fracture surface morphologies. The overall findings are discussed in terms of mutual interaction of multiple stress concentration sites, triaxial stress state, and strain localization.

Scientia Iranica

The Plasma Electrolytic Saturation (PES) technique is a relatively new process, which uses a high... more The Plasma Electrolytic Saturation (PES) technique is a relatively new process, which uses a high DC voltage power supply with a related organic electrolyte. Within the phenomenological model, the mechanism of the nanocrystalline coating formation processes has been developed to clarify the controlling variations of the procedure. Within the informative model, a feedback parameter for the formed surface state estimation was established. This parameter is the power spectral density of the current. The voltage versus current characteristics of the treatment within the plasma region depend on the main electrolysis conditions, such as current density, electrolyte concentration and agitation rate. Application of the control algorithm of the parameters could increase the e ciency of the plasma electrolytic saturation and nanocrystalline coating formation. In this process, the electric eld strength, \E", within the surface region reached a value of between 106 and 108 V/m, which was su cient for initiation of ionization processes in the vapor envelope. The ionization phenomena initially appeared as a quick sparking in scattered gaseous bubbles and then transformed into a uniform glow distributed throughout the vapor plasma envelope. Because of the hydrodynamic stabilization of the vapor envelope in the region of 180-210 V, the current dropped and the glow discharge transformed into intensive arcing, accompanied by a characteristic low-frequency acoustic emission.

RSC Advances, 2015

In this study, the effect of curing on the structure and protective performance of an eco-friendl... more In this study, the effect of curing on the structure and protective performance of an eco-friendly silane sol–gel coating on stainless steel 304L was investigated using electrochemical methods as well as surface analysis.

Progress in Natural Science: Materials International, 2012

NiP electroless coating was applied on low carbon steel with the incorporation of different amoun... more NiP electroless coating was applied on low carbon steel with the incorporation of different amounts of nano Al 2 O 3 powder (ranging from 3 g/l to 30 g/l) in electroless bath. Corrosion properties and microstructures of the coating were studied. The dispersion stability of alumina colloidal particles stabilized by polymeric (non-ionic) surfactants in an electroless bath was also investigated. The surface morphology and the relevant structure were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Corrosion behavior of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results showed that increasing alumina concentration not only changed the surface morphology, but also promoted the corrosion resistance. Addition of surfactants has an indirect effect on the amount of the incorporated particles. Meanwhile, in the presence of surfactant, corrosion resistance of NiP coating containing even a small quantity of alumina was improved since a stabilized bath was obtained.

Plasma Processes and Polymers, 2007

... Correspondence: Peyman Taheri, School of Metallurgy and Materials ... The authors wish to exp... more ... Correspondence: Peyman Taheri, School of Metallurgy and Materials ... The authors wish to express their sincere appreciation to Dr. Mohseni and Dr. Shayegan at School of Electrical Engineering, University of Tehran who provided the power supply for the present work. ...

Plasma Processes and Polymers, 2009

In this work, the feasibility of a plasma electrolytic carburizing (PEC) treatment on AISI H13 st... more In this work, the feasibility of a plasma electrolytic carburizing (PEC) treatment on AISI H13 steel using an aqueous solution of C3H5(OH)3, and NaOH was investigated. The substrate samples were biased cathodically to a 20 kW pulsed DC power supply with a variable voltage. The formation of hard carbon‐rich layer on the surface of the treated samples was confirmed by XRD analysis. Metallographic and SEM studies revealed that a uniform and compact nanocrystalline carbon‐rich layer was firmly stuck to the surface of the samples, and no cracks were observed between the carburized layer and the substrate. The coating mechanical performances were evaluated using microhardness tests. The microhardness of the carbon‐rich layer on the substrate was 866 HV, while the hardness of the substrate was 210 HV. Pin‐on‐disk abrasion tests were conducted to evaluate the surface wear resistance. Although all treated samples manifested a magnificent increase in wear resistance, the results showed differ...

Journal of Solid State Electrochemistry, 2010

Abstract Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposi... more Abstract Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry and scanning electron microscopy. The electrochemical ...

Journal of Applied Electrochemistry, 2010

Effect of grain size reduction on the electrochemical and corrosion behavior of iron of different... more Effect of grain size reduction on the electrochemical and corrosion behavior of iron of different grain sizes (32-320 nm) produced by direct and pulsed current electrodeposition was characterized using Tafel polarization curves and electrochemical impedance spectroscopy (EIS). The grain size of deposits was determined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The most intensive first-order peak (110) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The electrochemical tests were carried out in electrolyte 30 mg L-1 NaCl ? 70 mg L-1 Na 2 SO 4 ? 250 mg L-1 NaNO 2 aqueous solution. It was found that the corrosion potential and corrosion current density significantly changed as the microstructure morphology was changed. Results obtained from electrochemical tests suggested that the inhibition effect and corrosion protection of sodium nitrite inhibitor in nearneutral aqueous solutions increased as the grain size decreased from submicrocrystalline to nanocrystalline. This was attributed to the excess free energy, and concomitantly the increased number of the active sites caused by higher grain boundary and triple junction content in the nanocrystalline surface, which provides sites for electrochemical activity, and effect of sodium nitrite, was more pronounced.

International Journal of Materials Research, 2010

Résumé/Abstract The effect of grain size reduction on the corrosion inhibitor adsorption of nanoc... more Résumé/Abstract The effect of grain size reduction on the corrosion inhibitor adsorption of nanocrystalline Fe produced by pulse electrodeposition was characterized using tafel polarization curves and electrochemical impedance spectroscopy. The grain size of a ...

Corrosion, 1983

Corrosion of steel in concrete is a problem because of the presence of chloride ions at the metal... more Corrosion of steel in concrete is a problem because of the presence of chloride ions at the metal-concrete interface. The chloride ion is introduced as a contaminant in the mix or from the sources such as deicing salt or seawater. The electrochemistry of steel in this system is not well defined. This paper presents the polarization curves for steel in Type I and V portland cement with various salt contents. The degree of corrosiveness of steel in these two portland cement concretes was evaluated. Laboratory-dry and water-saturated concrete samples were used to determine the electrochemical behavior of steel at the presence of chloride ions in these conditions. The anodic polarization curves indicated that the steel passivates in the concrete sample of Type I portland cement with the salt content up to 0.1 %, but the passivity of steel was maintained up to 0.5% in Type V portland cement. (The samples had been exposed to distilled water for 90 days after removal from a water cabinet)....

Corrosion, 2009

The effects of two important factors, namely concentration and hydrodynamics on the inhibition ef... more The effects of two important factors, namely concentration and hydrodynamics on the inhibition efficiency of calcium gluconate (C12H22CaO14), were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy tests. Results showed that calcium gluconate was capable of inhibiting the corrosion of mild steel in simulated cooling water. The inhibition efficiency of calcium gluconate was increased by increasing its concentration and decreased by increasing water circulation velocity due to the adsorption process, which leads to the formation of a protective layer with a greater charge-transfer resistance on the metal surface. The hydrodynamic effect seems to promote the adsorption of calcium gluconate on the metal surface, which was confirmed by the fitting of the Langmuir adsorption isotherm.

Corrosion Science, 2014

ABSTRACT