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Showing 38 results for Subject: Surfe coating and corrosion

Mr Mohammadtaher Safarzadeh, Mr Seyed Mohammad Ali Boutorabi, Mr Asghar Arab,
Volume 7, Issue 3 (8-2010)
Abstract

The effects of anodizing condition and post treatment on the growth of nickel nanowires, were investigated. A two-step anodizing process was applied in phosphoric and oxalic acid solution. Nickel electrochemical plating was applied to fill Anodic Aluminum Oxide (AAO) pores. For pore filling enhancement, AAO surfaces were treated by silver predeposition. After electroplating, aluminum and oxide layer of some specimens were removed. The results showed that silver preplating increases the pore filling and as the applied voltage becomes higher, the pores diameter decreases.
A. Jafaria, S. H. Seyedeina, M. R. Aboutalebia, D. G. Eskinb, L. Katgermanb,
Volume 7, Issue 3 (8-2010)
Abstract

ABSTRACT Macrosegregation has been received high attention in the solidification modeling studies. In the present work, a numerical model was developed to predict the macrosegregation during the DC Casting of an Al-4.5wt%Cu billet. The mathematical model developed in this study consists of mass, momentum, energy and species conservation equations for a two-phase mixture of liquid and solid in an axisymmetric coordinates. The solution methodology is based on a standard Finite Volume Method. A new scheme called Semi-Implicit Method for Thermodynamically-Linked Equations (SIMTLE) was employed to link energy and species equations with phase diagram of the alloying system. The model was tested by experimental data extracted from an industrial scale DC caster and a relatively good agreement was obtained. It was concluded that a proper macrosegregation model needs two key features: a precise flow description in the two-phase regions and a capable efficient numerical scheme
A. m. Hadian, B. Nazari,
Volume 7, Issue 3 (8-2010)
Abstract

  ABSTRACT

Dolomite refractories have a good production potential in Iran due to the existence of high-quality dolomite ore in many regions of the country, particularly in Isfahan and Hamedan. The basic problem associated with the production and use of this type of refractories is inherent tendency to hydration of calcined dolomite. One of the methods to overcome this problem is to increase the amount of magnesia in doloma. This study focuses on the use of Iranian dolomite to produce magnesia –doloma (mag-dol) refractory with high resistance to hydration and corrosion. It was found that addition of 20wt% magnesite to dolomite would result in capsulating of CaO by MgO that protects doloma from further hydration
P. Karimi, K. S. Hui, K. Komal,
Volume 7, Issue 3 (8-2010)
Abstract

Abstract:

(Y2O3) and ethyl acetate as a mineralizer by hydrothermal method at a low temperature (T=.230°C, and

P=100bars).The as-prepared powders were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared

Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), UV-V Spectroscopy and Chemical Oxygen Demand

(COD) of the sewage water, respectively. The results show that hydrothermal method can greatly promote the

crystallization and growth of YVO4 phase. XRD pattern clearly indicates the tetragonal structure and crystallanity. An

FTIR spectrum of the YVO4 shows the presence of Y-O and V-O bond, respectively. The presence of these two peaks

indicates that yttrum vanadate has been formed. UV-V is absorption spectra suggesting that YVO4 particles have

stronger UV absorption than natural sunlight and subsequent photocatalytic degradation data also confirmed their

higher photocatalytic activity.

In this paper, YVO4 powder was successfully synthesized from Vanadium Pentaoxide (V2O5), Yttrium Oxide

Z. Ghaferi, K. Raeissi, M. A. Golozar,, A. Saatchi, S. Kabi,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract:

current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism of

tungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containing

ion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place via

reduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot be

ruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition current

density. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. In

Co-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared at

higher current densities. In this system the grain size remained almost constant with increasing current density. The

microhardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease in

tungsten content.

Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different

H. Rafiee*,, S. Rastegari, H. Arabi, M. Mojaddami,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract:

activity gas diffusion process has been investigated in this research. Effects of coating temperature and aluminum

concentration in powder mixture on formation mechanism were studied using optical and scanning electron

microscopes, EDS and X-ray diffraction (XRD) techniques. For this purpose two different packs containing 1 and 2

wt% aluminum powder, were used for coating the samples at two temperatures, 850ºC and 1050ºC. The ratio of Al to

activator was kept constant in both packs. By increasing the Al content in high activity powder mixture, the

concentration of diffused Al increased in the coating layers, and the thickness of coating increased. At 1050ºC as the

rate of diffused Al to the interdiffusion zone increased, this zone gradually transformed to outer coating phases. At

850ºC coating formed by inward diffusion of Al, but at 1050ºC it was initially formed by inward diffusion of Al followed

by outward diffusion of Ni.

Formation mechanism of an aluminide coating on a nickel base superalloy IN738LC via a single step high

Y. Fouad,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract: Rotating bending fatigue tests have been performed using smooth specimens of a rolled AZ31 magnesium alloy in laboratory air at ambient temperature. Fatigue strength and characteristic was evaluated and fracture mechanism was discussed on the basis fracture surface analysis. Electrical polishing (EP) as well as deep rolling (ball burnishing (BB)) U-notched specimens were performed on two groups of samples, to evaluate optimum conditions for fatigue life. The microstructure and tensile properties of roll cast (RC) Mg- 3% Al- 1% Zn (AZ31) was investigated. The fatigue strength of 107 cycles around 100 MPa for deep rolling while it was around 40 MPa for Electrical polishing. It was very important to understand the effect of (ball burnishing (BB)) conditions on the hardness of the surface through to the core. The two procedures improved the fatigue performance, but better improve in results were found in ball burnishing. The growth of small cracks initiated at the surface coincided with the FCP characteristic after allowing for crack closure for large cracks, but the operative fracture mechanisms were different between small and large cracks. At the subsurface crack initiation site, smooth facets were always present regardless of applied stress level.
Mr. Hossein Minouei, Dr. Mohammadhossein Fathi, Dr. Mahmood Meratian, Mr. Hossein Ghazvinizadeh,
Volume 9, Issue 3 (9-2012)
Abstract

ASTM F-75 Cobalt-base alloy castings are widely used for manufacturing orthopedic implants. This alloy needs both homogenization and solutionizing heat treatment after casting, as well as bioactivation of the surface to increase the ability of tissue bonding. In this study, ASTM F-75 Cobalt-base substrate was heat treated at 1220°C for 1 hour in contact with Hydroxyapatite-Bioglass powder in order to solutionize and homogenize the microstructure and promote surface bioactivation. For bioactivity evaluation, heat treated specimens were immersed in Simulated Body Fluid (SBF). Surface of specimens before and after the immersion was analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX) and X-Ray Diffraction (XRD). Results showed an appropriate microstructure with bioactive layer on the surface of specimens after heat treatment. In vitro result and formation of bone-like apatite layer on specimens indicated that heat treated samples were potentially suitable for bone replacement and tissue regeneration under highly loaded conditions.
Dr Mohammad Reza Sarmasti Emami,
Volume 9, Issue 3 (9-2012)
Abstract

This paper presents an experimental and theoretical investigation of the causes of corrosion of stack in a cement plant. In this paper, information related to metallic stack failures are given in the form of a case study in Neka Cement Plant, Mazandaran, Iran. Heavy corrosion attacks were observed on the samples of stack. The failure can be caused by one or more modes such as overheating, stress corrosion cracking (SCC), hydrogen embrittlement, creep, flame impingement, sulfide attack, weld attack, dew point corrosion, etc. Theoretical calculations and experimental observations revealed that, the corrosion had taken place due to the condensation of acidic flue gases in the interior of stack. Also, the chemical analysis of the corrosion deposits and condensates confirmed the presence of highly acidic environment consisting of mostly sulfate ions.
A. M. Rashad,
Volume 10, Issue 1 (3-2013)
Abstract

The  current  research  aims  to  investigate  alkali-activated  fly  ash  (AAFA)  concrete/mortar  modified  with
granulated ground blast-furnace slag (slag). FA was partially replaced with slag at levels of 0, 5, 10 and 15%, by
weight. The workability and mechanical properties of alkali-activated concretes were studied. Drying shrinkages of
alkali-activated mortars were investigated. All results of alkali-activated FA/slag concretes/mortars were compared to
control  concretes/mortars  based  on  plain AAFA.  The  results  indicated  that  the  workability  decreased  as  the  slag
content increased. Mechanical strengths and drying shrinkages increased with increasing slag content

F. Khorasanizadeh, B. Eftekhari Yekta, Y. Safaei-Naeini,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract:Some types of glass and glass ceramics have a great potential for making bone tissue engineering scaffolds, drug carrier and bone cements as they can bond to host bone, stimulate bone cells toward osteogenesis, and resorb at the same time as the bone is repaired. Calcium phosphate glass ceramics have very attractive properties that allow them to use in bone tissue engineering. Calcium phosphate glasses could be used for the fabrication of resorbable constructs, with controlled biodegradability. This work was investigated crystallization and sinterability of biodegradable glass ceramics in the CaO–P2O5–Na2O–TiO2 system using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Sinterability of the glasses also was investigated by measurement of sintering parameters. Different thermal treatments were applied to control the degree of devitrification of glasses. In the developed glass ceramics Ca2P2O7 were the first phase to precipitate in the mother glass structure, followed by Ca(PO3)2 and TiP2O7 at elevated temperature. Ca2P2O7 and Ca(PO3)2 seem to have a very positive effect in bone formation in vivo. It is therefore expected that glass ceramics understudy have good potential to be used for bone regeneration applications
A. Shahcheraghi, F. Dehghani, K. Raeissi, A. Saatchi, M. H. Enayati,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract: Mg2Ni alloy and Mg2Ni–x wt% TiO2 (x = 3, 5 and 10 wt %) composites are prepared by mechanical alloying. The produced alloy and composites are characterized as the particles with nanocrystalline/amorphous structure. The effects of TiO2 on hydrogen storage properties are investigated using anodic polarization and electrochemical impedance spectroscopy. It is demonstrated that the initial discharge capacity and exchange current density of hydrogen are increased by adding 5wt% TiO2, while the cycle stability and bulk hydrogen diffusivity don’t change. It is found that the charge transfer resistance of Mg2Ni–5wt% TiO2 composite is lower than that of Mg2Ni alloy. On the other hand, the hydrogen oxidation during the discharge process proceeds more easily on the electrode surface containing TiO2 additive.
V. Tajer-Kajinebaf, H. Sarpoolaky, T. Mohammadi,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract:Nanostructured titania was synthesized by colloidal and polymeric sol-gel routes. Stable colloidal and polymeric titania sols were prepared by adjusting the proper values of the acid/alkoxide and the water/alkoxide molar ratios. The properties of sols were determined by dynamic light scattering technique and synthesized titania was characterized by thermogravimetry and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy and field emission scanning electron microscopy. The results showed particle size distribution of colloidal sol 10-50 nm compared to polymeric one which was 0.5-2 nm. Phase analysis of the colloidal sample revealed anatase as the major phase up to 550 °C, while the polymeric route resulted only anatase phase up to 750 °C. On the basis of results, titania prepared by the polymeric route showed better thermal stability against phase transformation than the sample prepared by the colloidal route. Also, microstructural studies showed that titania nanopowder can be produced by both sol-gel routes
S. R. Allahkaram, R. Faezi Alivand, M. S. Bakhsh,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract:Electroless Nickel-phosphorus (EN) coatings provide high performance in various industrial fields due to their unique properties such as excellent corrosion and wear resistance. This paper aims to study the effect of ZnO nano-particles addition on corrosion behavior of EN coatings. Various amounts of ZnO nano-particles with average diameter of 50 nm were added to hypophosphite reduced EN bath to deposit composite coatings. Microstructural investigations were carried out via scanning electron microscopy (SEM). Chemical composition of the coatings was investigated via energy dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS) and polarization tests were used to study the corrosion properties of the coatings in a 3.5 wt.% NaCl solution. SEM investigations showed that the coating deposited from the bath containing 2 g/L of ZnO nano-particles had the most amount of nano-particles incorporated in the coating. EDS results revealed that incorporation of ZnO nano-particles in the composite coating resulted in a decrease in phosphorous content of the coating. Corrosion tests showed that corrosion resistance of the electroless Ni-P/nanoZnO composite coatings in 3.5 wt.% NaCl solution had an improvement in comparison to electroless Ni-P base coating
Sh. Shahriari, M. Ehteshamzadeh,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract: Plasma electrolytic oxidation (PEO) technique was used to prepare ceramic coatings on the casted aluminum alloys containing ~5 and ~9.5 wt.% Mg. The applied voltage was controlled at 450V and 550V for evaluating the effect of this main parameter, as well as, magnesium content of the substrate on the microstructure and electrochemical corrosion behavior after PEO treating. The results of X-ray diffraction confirmed formation of galumina and MgSiO3. It was found that higher applied voltage caused fewer and minor discharge channels which led to higher corrosion resistance. Also, increasing of magnesium content of the substrate caused decreasing of polarization resistance, which could be associated to the formation of MgSiO3.
M. Alzamani, A. Shokuhfar, E. Eghdam, S. Mastal,
Volume 10, Issue 1 (3-2013)
Abstract

Abstract:In the present research, SiO2–TiO2 nanostructure films were successfully prepared on windshields using the sol–gel technique for photocatalytic applications. To prevent the thermal diffusion of the sodium ions from the glass to TiO2 films, the SiO2 layer was pre-coated on the glass by the sol–gel method. The substrates were dipped in the sol and withdrawn with the speed of 6cm/min-1 to make a gel coating film. The coated films were dried for 2 days at 27 °C to allow slow solvent evaporation and condensation reactions due to rapid sol–gel reaction of Titania precursor. Then, the films were annealed at 100 °C for 30min and at the final temperature (500, 700 °C) for 30 min continuously. The structure and surface morphology properties, which are as a function of annealing temperature, have been studied by SEM FE-SEM and XRD. The FE-SEM surface morphology results indicate that the particle size increases from 19 to 42 nm by increasing the annealing temperature from 500 °C to 700 °C. Likewise, XRD illustrate the crystal anatase and rutile as main phases for TiO2-SiO2 films annealed at 500 °C and 700 °C respectively. This procedure resulted in transparent, crack-free SiO2–TiO2 films.
A. Qaed Amini Haroooni, H. Eskandari, M. H. Maddahy, I. Danaee,
Volume 12, Issue 4 (12-2015)
Abstract

The electrochemical behavior of 6063 aluminum alloy in ethylene glycol-water mixture was investigated by polarization curves and AC impedance measurements (EIS).  The results obtained from polarization curves showed that corrosion rate decreased with increasing ethylene glycol concentration. EIS data showed the decrease in the interface capacitance which caused by adsorption of ethylene glycol at the surface of aluminum alloy. The cathodic current increased with the increase in rotating speeds of solution and the anodic current decreased. The effect of temperature was studied and the corrosion rate was increased with increasing the temperature. In addition, thermodynamic parameters were calculated in different ethylene glycol concentrations


N. Bahrami Panah, N. Ajami,
Volume 13, Issue 1 (3-2016)
Abstract

The epoxy coatings containing multi-walled carbon nanotube/ poly ortho aminophenol nanocomposite were prepared and used as anticorrosive coatings. The nanocomposites with different contents of carbon nanotube were synthesized in a solution of sodium dodecyl sulfate and ammonium peroxy disulfate as a surfactant and an oxidant, respectively. The morphology and structural properties were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy methods. The mean size of nanocomposite particles was 20-35 nm determined by scanning electron microscopy. The epoxy coatings containing the nanocomposites were applied over mild steel panels and their corrosion performance was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization measurements in a 3.5 % sodium chloride solution. The results showed that epoxy coatings consisting of nanocomposite with 1 wt.% multi-walled carbon nanotube exhibited higher anticorrosive properties than other prepared coatings of different carbon nanotube contents, which could be due to the strong interaction between the mild steel surface and the conjugated nanocomposite.

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M. R. Khorram, M. R. Shishesaz, Iman Danaee, D. Zaarei,
Volume 13, Issue 1 (3-2016)
Abstract

The micro layers micaceous iron oxide and nano-TiO 2 were incorporated into the epoxy resin by mechanical mixing and sonication process. Optical micrographs showed that the number and diameter size of nanoparticle agglomerates were decreased by sonication. The structure and composition of the nanocomposite was determined using transmission electron microscopy which showed the presence of dispersed nano-TiO 2 in the polymer matrix. The anticorrosive properties of the synthesized nano-composites coating were investigated using salt spray, electrochemical impedance spectroscopy and polarization measurement. The EIS results showed that coating resistance increased by addition of micaceous iron oxide micro layers and nano-TiO 2 particles to the epoxy coatings. It was observed that higher corrosion protection of nanocomposite coatings obtained by the addition of 3 %wt micaceous iron oxide and 4%wt nano-TiO 2 into epoxy resin.

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S. Yazdani, S. Javadpour, Sh. Mehdizadeh Naderi, M. Javidi,
Volume 13, Issue 2 (6-2016)
Abstract

The inherent reactivity of the Al–Cu alloys is such that their use for structural, marine, and aerospace components and structures would not be possible without prior application of a corrosion resistance system. Historically these corrosion resistance coatings were based on the use of chemicals containing Cr (VI) compounds. Silane coatings are of increasing interest in industry due to their potential application for the replacement of current toxic hexavalent chromate based treatments. In this study, hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7M NH4OH) at a molar ratio of 1:25:4.31 respectively. The coatings were applied by a dip-technique to 2024-T3 Al alloy, and subsequently cured at room temperature and there after heat treated in an oven at 150°C. The anticorrosion properties of the coatings within 3.5 wt% NaCl solution were studied by Tafel polarization technique. The sol–gel coating exhibited good anticorrosion properties providing an adherent protection film on the Al 2024-T3 substrate. The surface properties were characterized by water contact angle measurement, scanning electron microscopy (SEM), and the composition was studied by Fourier transform infrared spectroscopy (FTIR).

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