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

Papers by Changiz Dehghanian

The dependency of uniform corrosion of structural steel on the average grain size (D) should be q... more The dependency of uniform corrosion of structural steel on the average grain size (D) should be quantified for design purposes. In the present work, a spectrum of grain sizes was obtained by simple heat treatment routes in st37 structural steel. It was revealed that the corrosion current density (icorr) increased by grain refinement, which was related to the increased density of grain boundaries. The data on the plots of hardness and icorr versus 1/√D were successfully fitted by a straight line and an exponential function, respectively. Therefore, the mechanical response was rationalized by a Hall-Petch type relationship with a slope of 237.8 MPa/µm0.5. Moreover, the obtained simple relationship between icorr and 1/√D can be used for prediction of the dependency of uniform corrosion on the average grain size.

Tempering kinetics and corrosion resistance of quenched and tempered AISI 4130 medium carbon steel

Materials and Corrosion, 2021

The kinetics and the effects of tempering on the corrosion resistance of AISI 4130 steel were stu... more The kinetics and the effects of tempering on the corrosion resistance of AISI 4130 steel were studied. The tempering activation energy was close to that for the diffusion of C in α‐iron. This implies that the tempering kinetics in this steel is controlled by carbon diffusion. By increasing the time and temperature of tempering, the corrosion current density (icorr) in the polarization curves decreased whereas the diameter of the semicircular arc in the Nyquist plots increased, which implies higher corrosion resistance. The icorr was successfully related to hardness, which actually indicates the effect of microstructure. Based on these findings, the quench and tempering treatment was used to adjust both the hardness and corrosion resistance of the AISI 4130 steel.

Archives of Civil and Mechanical Engineering, 2020

The effects of surface preparation on the corrosion resistance of AISI 316L austenitic stainless ... more The effects of surface preparation on the corrosion resistance of AISI 316L austenitic stainless steel were studied using the cyclic potentiodynamic polarization method. Grinding, mechanical polishing, and electropolishing were considered as the surface modifier methods. Regarding the surface roughness parameters, besides the conventional height parameter (R a ), the kurtosis (Rku) as the shape parameter was also considered to rationalize the pitting resistance for the first time. Based on the results of the Tafel extrapolation method, it was revealed that the uniform corrosion can be adequately correlated to R a . However, the pitting resistance was found to mainly relate to the kurtosis, where by decreasing Rku (increased bluntness of topographic features), the pitting resistance enhanced. It was also found that a surface with Rku less than three (platykurtic) is resistant to pitting attack, where this surface can be obtained via electropolishing performed for an optimum time. The effect of electropolishing on the chromium content at the surface and its relation to the corrosion properties were also discussed.

Materials Today Communications, 2019

The mechanical and corrosion behaviors of low carbon dual phase (DP) steel were studied based on ... more The mechanical and corrosion behaviors of low carbon dual phase (DP) steel were studied based on different tempering conditions. By increasing the time and temperature of tempering, the ultimate tensile strength (UTS), the hardness, and the corrosion current density (i corr ) in the polarization curves decrease while the total elongation and the diameter of the semicircular arc in the Nyquist plots increase. Tempering treatment resulted in the appearance of the yield point phenomenon and an initial rise in the yield stress (YS). While the UTS values were related to hardness through a single relationship for both tempered and DP steels, two separate trends were observed for the relation of the YS and hardness. The latter was related to the high work-hardening rate of DP steels that increased the hardness during indentation. The tempering kinetics were also studied and the average value of the Avrami exponent (n) was determined as 0.65, which was interpreted as precipitation on dislocations (theoretical n-value of 0.667). The tempering activation energy was determined as ∼ 40 kJ/mol, which was indicative of the rapid diffusion of carbon atoms along the dislocation core (pipe diffusion), and hence, it was concluded that the kinetics of tempering is essentially controlled by carbon atom diffusion.

steel research international, 2019

The effect of martensite volume fraction on the mechanical and corrosion properties of low‐carbon... more The effect of martensite volume fraction on the mechanical and corrosion properties of low‐carbon dual‐phase steel is studied based on both step quenching (SQ) and intercritical annealing (IA) routes. For SQ samples, hardness and ultimate tensile strength decrease with increasing holding time at the intercritical temperature and reach a plateau, which is related to the decrease in the amount of martensite during annealing. Conversely, for the IA samples, hardness increases during holding at the intercritical temperature due to austenitization and reaches the same plateau. At a same martensite volume fraction, the work‐hardening behavior of SQ samples is better than IA samples, which is related to both the finer grain size and smaller martensite islands in the former. At low martensite fractions, the corrosion properties are comparable with the as‐received ferritic–pearlitic sample. It is revealed that by decreasing the volume fraction of martensite in SQ samples, the corrosion curre...

Phase transformation mechanism and kinetics during step quenching of st37 low carbon steel

Materials Research Express, 2019

Step quenching of st37 low carbon steel was studied for understanding the phase transformation ki... more Step quenching of st37 low carbon steel was studied for understanding the phase transformation kinetics. During step quenching, the amount of martensite (formerly austenite) decreased by increasing the holding time at the intercritical annealing temperature. Based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis using the hardness data, Avrami exponents in the range of 0.3 to 0.8 were determined, which indicate that the austenite to ferrite transformation in the intercritical temperature region is diffusion controlled. The activation energy of 84.2 kJ/mol was obtained, which is close to the activation energy for the diffusion of carbon in α-iron (87.4 kJ/mol). Consequently, the diffusion of carbon in α-iron was found to be responsible for the microstructure formation via transformation of austenite to ferrite during step quenching. In fact, the grain-boundary ferrite phase grows into the surrounding austenite phase during step quenching while the austenite phase forms in place of pearlite and also nucleates on the ferrite grain boundaries during intercritical annealing of ferrite-pearlite microstructure. Based on these findings, the slower kinetics of the microstructure formation during step quenching (as compared to the conventional intercritical annealing) was related to the atomic diffusion mechanisms, where the diffusion of carbon in α-iron was calculated to be slower than that in γ-iron at 850 °C.

Journal of Solid State Electrochemistry, 2018

This paper compared the applicability of nickel-copper and nickel-nickel oxide metallic foams as ... more This paper compared the applicability of nickel-copper and nickel-nickel oxide metallic foams as current collectors for supercapacitor. A comprehensive characterization of foams was presented and includes the analysis of their structural, chemical, and electrochemical properties. Several techniques such as structural characteristics and electrochemical methods were used to examine the surface morphology and surface chemical composition of these materials. The process was studied under welldefined experimental conditions using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge and discharge (GCD). The outcome of these experiments demonstrated that the Ni-NiO foam had a higher specific capacitance than Ni-Cu foam. The best specific capacitance for Ni-NiO foam was calculated to be 924 F/g at 1 A/g, which was higher than that obtained for Ni-Cu foam (536 F/g at 1 A/g). Ni-NiO foam maintained 81.8% of its specific capacitance at a current density of 20 A/g and after 3000 cycles, without significant loss of supercapacitor activity.

Surface and Coatings Technology, 2019

In this study, a Si-HA coating was deposited on Mg-5Zn-0.3Ca alloy substrate by pulse electrodepo... more In this study, a Si-HA coating was deposited on Mg-5Zn-0.3Ca alloy substrate by pulse electrodeposition. The effect of varying electrodeposition parameters like current density (20, 40, 60 mA/Cm -2 ), duty cycle (0.1, 0.2), pH (4, 5, 6) and temperature (25, 85, 100 ̊C) on the composition and morphology of coating were investigated. A homogenous nano-needle morphology of Si-HA coating was chosen as optimum coating. Regarding to results obtain from SEM and XRD, in low current density of 20 mA/cm -2 a coarse and non-uniform coating was deposited and in high current density of 60 mA/cm 2-, high amounts of hydrogen gas at interface was produced and a non-uniform coating was formatted once more. At middle current density of 40 mA/cm -2 , nano-needle like coating could be deposited. According to results, an increase in duty cycle from 0.1 to 0.2 increased the t on and the pH of electrolyte vicinity of cathode and cause calcium phosphate of DCPD deposited along with HA on surface and morphology of coating was also changed from needle like to think plate like. The results also indicated coatings had micro size sheets and agglomerated morphology in 25 ̊C and 100 ̊C, respectively, whereas coating had nano-sized needle-like blades approximately 100-200 nm in length and < 100 nm in thickness in 85 ̊C. the pH less or > 5 for electrolyte (4 and 6) made the plate like morphology for coating. Moreover, the results indicated that the selection of composited Mg alloy with nano-HA as a substrate caused the deposition of Si-HA coatings on it to be more homogenous with better interface in comparison to that of Mg alloy selection as a substrate. fectively control deterioration of implant and indorses the bone tissue

Transactions of Nonferrous Metals Society of China, 2018

Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) p... more Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) powders by powder metallurgy method. The effect of various mass fractions of nHA (1%, 2.5%, 5%) as reinforcement on the corrosion properties of Mg-5Zn-0.3Ca alloy was investigated. The corrosion resistance of biocomposite samples was investigated by immersion tests and electrochemical techniques in SBF solution. The results showed that the corrosion resistance of Mg alloy was improved by adding 1% and 2.5% nHA. Bioactive nHA motivated the formation of stable phosphate and carbonate layers on surface and improved corrosion resistance of nanocomposites. However, addition of large contents of nHA in Mg alloy as reinforcement increased the density of this precipitated layer, so gases produced from localized corrosion were accumulated underneath this layer and decreased its adhesiveness and lowered its corrosion resistance. Indirect cytotoxicity evaluation for Mg alloy and its nanocomposites also showed that their extraction was not toxic and nanocomposite with 1% nHA indicated almost similar behavior as negative control.

Journal of Materials Engineering and Performance, 2018

The effects of near-surface severe plastic deformation (NS-SPD) on the inhibition performance of ... more The effects of near-surface severe plastic deformation (NS-SPD) on the inhibition performance of sodium molybdate (SM) and 1H-benzotriazole (BTA) for mild steel were investigated using weight loss, polarization and electrochemical impedance spectroscopy measurements. The crystal grain size of NS-SPD-processed surface was analyzed by x-ray diffractometry and field emission scanning electron microscopy. A deformed layer with thickness of 20 ± 5 lm was produced on mild steel surface after NS-SPD process due to accumulated strains. The NS-SPD process caused more effective adsorption of corrosion inhibitors due to the fabrication of a surface with a high density of preferential adsorption sites. However, the stability of protective layer was predominantly influenced by the effect of NS-SPD process on inhibition efficiency. The fairly good persistence of protective layer formed on the surface by SM-containing solution and also positive effect of NS-SPD process on adsorption of molybdate ions caused higher inhibition performance for sodium molybdate. However, NS-SPD process encouraged deterioration of protective layer formed on steel surface in the presence of BTA inhibitor. It was ascribed to partial coverage of surface, low stability of adsorbed layer and thus more adsorption of aggressive ions on unprotected area which was uncovered during immersion time.

Journal of Applied Electrochemistry, 2018

This study introduces a novel, non-toxic, scalable, two-step method for the fabrication of highly... more This study introduces a novel, non-toxic, scalable, two-step method for the fabrication of highly nanoporous nickel and nickel oxide (Ni-NiO) foam/Electrochemically reduced graphene oxide (ERGO) electrodes with exceptional capacitance suitable for supercapacitor application. This procedure includes drop cast and graphene oxide (GO) reduction by galvanostatic process. To create the electrodes, electrodeposition process and selective electrochemical dealloying accompanied by a hydrogen evolution reaction (HER) were performed on a copper substrate. Afterwards, drop cast and galvanostatic processes were accomplished to coat GO nanosheets on Ni-NiO foam. The structure of achieved nanocomposites was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). High-specific capacitance of 1995 F g -1 at a current density of 1 A g -1 (galvanostatic charge-discharge) (GCD) was achieved for the Ni-NiO foam/electrochemically reduced graphene oxide (ERGO) electrode with excellent cycling stability. A constant, high-specific capacitance (95.1% of the initial value) was achieved after 6000 cycles at 20 A g -1 .

Applied Surface Science, 2018

 Cathodic deposition with the dynamic hydrogen bubble template was coupled to make nanostructure... more  Cathodic deposition with the dynamic hydrogen bubble template was coupled to make nanostructured Nickel-Copper foams.  ERGOs are grown on Ni-Cu foam by constant potential method.  The effects of reduction currents on the capacitance are remarkable  The composite exhibits a high specific capacitance and good stability.

Materials Research Bulletin, 2019

A new and applicable method for the synthesis of flower-like NiCo2O4 was developed based on the e... more A new and applicable method for the synthesis of flower-like NiCo2O4 was developed based on the electrochemical method of chronoamperometry and subsequent heat treatment. This synthesis involved electrochemical deposition of nickel and cobalt hydroxide on ERGO/Ni-NiO and heat treatment for conversion of hydroxide to oxide. The crystalline structure and electrochemical performance of flower-like 3D NiCo2O4 were manipulated by varying the potential of deposition. The optimized nanocomposite at the potential of -1.0 V vs. saturated calomel electrode (SCE) had the highest surface area (85 m 2 /g). The smart combination of NiCo2O4 and electrochemically reduced graphene oxide (ERGO) on nickel-nickel oxide (Ni-NiO) foam showed a remarkable synergy effect and demonstrated a high specific capacitance and cycling stability improved performance. This new material not only exhibited a specific capacitance of over 2461 F/g, but after 4000 cycles, it maintains 94% of its specific capacitance.

Journal of Materials Engineering and Performance, 2016

The present work explores how deposition parameters affect structural and morphological character... more The present work explores how deposition parameters affect structural and morphological characteristics of ZnNi/nano-SiC composites in order to engineer an environmentally benign corrosion-resistant coating. In this regard, ZnNi and ZnNi coatings containing SiC nanoparticles were electrodeposited from chloride bath by direct current method, and the effects of SiC concentration, deposition current density and two types of surfactant (sodium dodecyl sulfate, SDS, and hexadecyltrimethyl ammonium bromide, HTAB) were investigated. Increasing SiC nanoparticles concentration in the electrolyte enhances the SiC content of the coating and can affect the coating composition, structure and morphology. Elevation of deposition current density may reduce SiC content of the coating, yet this decline can be compensated by the addition of HTAB. Application of 11 g/L SiC nanoparticles produced a coating with a more even surface and less porosity that had the highest corrosion resistance. The presence of nanoparticles seemingly reduces the available surface for electrochemical reactions and decelerates corrosion.

Investigation on the phase transformation of electroless Ni–B coating after dry sliding against alumina ball

Journal of Alloys and Compounds, 2016

Abstract The purpose of the work was to evaluate the possibility of tribochemical reactions durin... more Abstract The purpose of the work was to evaluate the possibility of tribochemical reactions during dry sliding of electroless Ni–B coating against an alumina ball. The effect of probable tribochemical products on the tribological behavior of Ni–B/Al2O3 tribosystem was investigated. Wear experiments were performed in a ball-on-disc configuration pressing alumina balls towards rotating disc specimens. Wear tests were carried out at normal loads of 5, 20, 40 and 60 N at the sliding distance of 100 m. Electroless Ni–B coatings with a mean thickness of 50–60 μm were applied on the mild carbon steel substrates. The worn surfaces of Ni–B coatings were studied with Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-Ray Diffractometer (XRD) and X-ray Photoelectron Spectrometer (XPS). The results showed that the structure of the worn surfaces of the coatings changed from amorphous to the crystalline. The dominant wear mechanism in the present tribosystem was combination of adhesive and abrasive wear. As the load was increased the friction coefficient and its fluctuations were decreased. The wear rate of alumina balls changed from increasing to decreasing at the load of 40 N. XPS and XRD analysis revealed the phase transformation and production of Ni–Al compounds on the worn surface of electroless Ni–B coating. It was elucidated that tribochemical reactions between the mating surfaces were responsible for tribological behavior of Ni–B coating and unexpected wear behavior of alumina balls.

Synthesis, characterization and electrochemical performance of a new imidazoline derivative as an environmentally friendly corrosion and scale inhibitor

Research on Chemical Intermediates, 2015

A new imidazoline derivative, {[(benzimidazol-2-ylmethyl)imino]bis(methylene)} bis(phosphonicacid... more A new imidazoline derivative, {[(benzimidazol-2-ylmethyl)imino]bis(methylene)} bis(phosphonicacid), named as BMIBMBPA, was synthesized as an environmentally friendly corrosion and scale inhibitor. The performance of BMIBMBPA for carbon steel in cooling tower water was evaluated using weight loss, electrochemical measurements and a scale test and compared to that of sodium tungstate. The optimum concentration of BMIBMBPA was measured to be 40 mg/L and a much higher value, even at lower inhibition efficiencies, was determined for sodium tungstate. The electrochemical measurements demonstrated that BMIBMBPA acts as a mixed-type corrosion inhibitor. Surface analyses revealed adsorption of BMIBMBPA and scale inhibition through disruption in growth of precipitates.

Surface and Coatings Technology, 2015

Commercially pure (CP) titanium was treated by plasma electrolytic oxidation in phosphate and zir... more Commercially pure (CP) titanium was treated by plasma electrolytic oxidation in phosphate and zirconate electrolytes. The microdischarge behavior and corrosion properties of plasma electrolytic oxidation coatings containing zirconium on CP-Ti prepared in electrolytes containing various additive concentration under different duty cycles was studied by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Electrochemical corrosion tests indicated that the PEO coating formed in zirconate solution under an appropriate duty cycle showed a much superior stability during the corrosion tests and provided an efficient corrosion protection. Relationships are drawn between PEO applied duty cycle, electrolyte concentration and corrosion performance. The protective coatings treated at lower duty cycles had higher corrosion resistance during long time immersion in sodium chloride solution due to more compact microstructural features. The EIS analysis of the PEO coating provided information about the evolution of internal structure of the coating with duty cycle of the process.

Improvement in the corrosion resistance of stainless steel 304L in sodium chloride solution by a nanoclay incorporated silane coating

RSC Advances, 2015

An eco-friendly silane sol–gel coating incorporating nanoclay was formulated to provide an effect... more An eco-friendly silane sol–gel coating incorporating nanoclay was formulated to provide an effective corrosion protection for stainless steel 304L in a NaCl solution.

The Influence of Grain Size of Pure Iron Metal on Corrosion Inhibition in Presence of Sodium Nitrite

International Journal of Modern Physics: Conference Series, 2012

The effects of grain size reduction on the corrosion inhibition of sodium nitrite were investigat... more The effects of grain size reduction on the corrosion inhibition of sodium nitrite were investigated using polarization curves and electrochemical impedance spectroscopy (EIS). Nanocrystalline iron (~ 45 nm) was produced by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM). The most intensive first-order peak (211) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The tests were carried out in 25 mg / l NaCl + 57 mg / l Na 2 SO 4 with different concentration of sodium nitrite aqueous solutions. The results revealed that due to the adsorption process which leads to the formation of a protective layer with a greater charge transfer resistance the inhibition effect and corrosion protection of sodium nitrite inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to na...

Corrosion Science, 2015

In this study, an epoxy/polyaniline-camphorsulfonate nanocomposite (epoxy/PANI-CSA) is employed t... more In this study, an epoxy/polyaniline-camphorsulfonate nanocomposite (epoxy/PANI-CSA) is employed to protect reinforcing steels in chloride-laden concrete environment. The synthesized nanocomposite was characterized using Fourier transform infrared spectroscopy and transmission electron microscopy. Bare, epoxy-coated and epoxy/PANI-CSA nanocomposite-coated steel rebars were embedded in normal and self-compacting concretes. To evaluate their corrosion behaviors, open circuit potential and impedance measurements were performed for the duration of 1 year. Ultimate bond strength of concrete with the reinforcement bars were measured in corroded and uncorroded conditions. It was found that epoxy/PANI-CSA coating provides good corrosion resistance and durable bond strength with concrete for steel rebars.