Iranian Journal of Materials Science and Engineering

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A large number of reinforced concrete structures subjected to chloride ions. Two basicapproaches for preventing corrosion of reinforcing steel embedded in concrete are: Increasing theconsolidation of concrete and using different coating on rebars. In present research steel rebarsare coated in different ways: a) 40 µm of zinc electroplated on steel rebar b) Zinc powder withepoxy paste (zinc rich). The rebars were placed in a macrocell design according to ASTM G109-92. Concrete operations were done with mixture designs of high and normal strength concrete.The results show corrosion decrease of zinc coated rebars.

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Anodes are critical component of cathodic protection systems. As part of this effort, three different anodes were tested in a cathodic protection system that was designed and constructed to prevent further corrosion of reinforced concrete. This anodic system includes an electrically conductive coating composition applied in fluid form over an outer surface of the concrete mix. The composition further includes a predetermined amount of electrically conductive carbon material (coke, carbon black, graphite) uniformly distributed in the epoxy resin (as a binder) whereby the coating composition has a predetermined value of resistively. This investigation attempts to find the best type and optimum content of conductive carbon filler in poxy coating, to ensure optimal anode working parameters for marine environments (basically marine and sewer environments) and if any of the coating systems tested in this study excel over the other. In this study, electric and electrochemical parameters of three layer (with average coating thickness of 300µm) coke-epoxy, carbon black-epoxy and graphite-epoxy conducting paints (with different amount of filler) have been determined during long-term anodic polarization (70 days) in a seawater solution. During this test, on the basis of impedance measurements, the electrical resistances of these coatings have been calculated every 14 days. if conductive paints exhibit good electric and electrochemical stability, they will be attractive for cathodic protection of reinforced concrete.

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Abstract: In this research, the oxidation behaviour of high Aluminum heat resistant steel (%25Cr,%20Ni,%8Al) hasbeen evaluated at the temperature range of (1000-1300ºC).The results showed that there was no countinous healinglayer on the surface of the alloy when Al increased up to %5.5 and the oxidation resistance of steel decreased due toformation of spinel oxides on the surface.By increasing the aluminum amount to %8, only Al oxide formed due to decreasing carbon potential of thealloy,homogenity of elemental concentration in matrix and no diffusion of  oxygen through oxide–metalinterface,therefore it has superior oxidation resistance. Meanwhile,oxidation tests showed that the weight gain of thesteel at high temperature oxidation even at 1300ºC was too low.

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Abstract: Equal channel angular extrusion (ECAE) is a promising technique for production of ultra fine-grain (UFG) materials of few hundred nanometers size. In this research, the grain refinement of aluminium strip is accelerated by sandwiching it between two copper strips and then subjecting the three strips to ECAE process simultaneously. The loosely packed copper-aluminium-copper laminated billet was passed through ECAE die up to 8 passes using the B_c route. Then, tensile properties and some microstructural characteristics of the aluminium layer were evaluated. The scanning and transmission electron microscopes, and X-ray diffraction were used to characterize the microstructure. The results show that the yield stress of middle layer (Al) is increased significantly by about four times after application of ECAE throughout the four consecutive passes and then it is slightly decreased when more ECAE passes are applied. An ultra fine grain within the range of 500 to 600 nm was obtained in the Al layer by increasing the thickness of the copper layers. It was observed that the reduction of grain size in the aluminium layer is nearly 55% more than that of a ECA-extruded single layer aluminium billet, i.e. extruding a single aluminium strip or a billet without any clad for the same amount of deformation. This behaviour was attributed to the higher rates of dislocations interaction and cell formation and texture development during the ECAE of the laminated composite compared to those of a single billet

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Abstract:

composition of MgO and nano boehmite. The reactant and potassium chloride, as the reaction media, were fired at

800-1000 °C at different dwell times (0.5-5 h) in the ambient atmosphere. After washing and filtration, the spinel nano

powder was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-

Teller (BET) techniques. It was demonstrated that the formation temperature decreased to 850

particles revealed an average size of 30 nm with a narrow size distribution. The mechanism of MgAl

was found to be a template type where the morphology and size of product were similar to those of alumina formed

from boehmite decomposition. Prolonging the reaction time from 0.5 to 3 h, the reaction was further completed and

crystallinity was improved. However, the increase of temperature was more effective in this regard.

MgAl2O4 (MA) nano powder was synthesized via molten salt technique, by heating stochiometric°C. The nano spinel2O4 formation

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Ultraviolet–Visible (UV–Vis) spectroscopy was used, in the current investigation, to explore the dispersion and stability of titania nanoparticles in an aqueous media with different types of dispersants. Hydrochloric and nitric acids as well as ammonia were used to determine the stability of the suspension in the acidic region (pH=2.5) and basic area (pH=9.5), respectively. In addition, for measuring sustainability of suspension and creating steric, and electrosteric repulsive forces, ethylene glycol and ethylene glycol plus ammonia were employed, respectively. UV–V is
spectrometry was applied to realize the effect of nano titania concentrations and different types of dispersants of samples containing different amounts of nano titania and different types of dispersants on stability of TiO2-containing suspensions. In addition, the stability of dispersion could be evaluated in colloidal mixtures containing ethylene glycol plus ammonia. It was demonstrated that the mixtures containing ethylene glycol plus ammonia were stable over a period of 4 days. To support the UV–Vis results, other techniques such as atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to study the degree of agglomeration of titania nanoparticles in terms ofmorphology and size.

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The rapidly solidified prealloyed alpha brass powder with a size range of 40 to 100 μm produced by water atomization process was consolidated using liquid phase sintering process. The relationships between sintering temperature, physic-mechanical properties and microstructural characteristics were investigated. Maximum densification was obtained at 930 °C, under 600 MPa compacting pressure, with 60 min holding time. The microstructure of the sintered brass was influenced by dezincification and structural coarsening during supersolidus liquid phase sintering. As a consequence of Kirkendall effect atomic motion between Cu and Zn atoms caused to dezincification at the grain boundaries and formation of ZnO particles on the pore surfaces. It was concluded that microstructural analysis is in a well agreement with obtained physical and mechanical properties. Also, the amount of liquid phase, which depends on sintering temperature, results in different load bearing cross section areas, and it affects the type of fracture morphologies.

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In this research, infiltration behavior of W-Ag composite compacts with Nickel and Cobalt as additives has been investigated. Nickel and Cobalt were added to Tungsten powder by two distinct methods: mixing elementally and reduction of salt solution. The coated Tungsten powders were compacted under controlled pressures to make porous skeleton with 32-37 vol. % porosity. Infiltration process was carried out at 1100 ̊C under a reducing atmosphere for 1h. The effect of additives on infiltration of Ag and density were evaluated by SEM and Archimedes methods. Properties of the specimens were compared following two distinct processes namely: I) sintering simultaneously with infiltration process and II) sintering prior to infiltration (pre-sintering process). It was found that specimens which were pre-sintered and then infiltrated with molten silver represent higher hardness and finer microstructure than the specimens infiltrated simultaneously with sintering.

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In this paper, the effect of MgO, BaO, Na 2 O and SrO addition to a pre-melted CaO-Al2O3 -Si 2 O synthetic slag on sulfur removal from plain carbon steel was studied under the same experimental conditions. The slags were pre-melted at 1400°C in an electric resistant furnace and desulfurization experiments were carried out in a high frequency induction furnace. The results showed that the optimum reaction time for desulfurization was 15 min. It was found that while SrO addition to the ternary slag enhances the sulfur removal capability, MgO, Na 2O and BaO additions reduce desulfurization efficiency of the ternary slag. Moreover, it was observed that restricting access to oxygen from the atmosphere by using a covered crucible, could increase desulfurization efficiency of the slag by more than two fold

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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

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In this study, Boron carbide was synthesized using Mesoporous Carbon CMK-1, Boron oxide, and magnesiothermic reduction process. The Effects of temperature and magnesium grain size on the formation of boron carbide were studied using nano composite precurser containg mesoporous carbon. Samples were leached in 2M Hydrochloric acid to separate Mg, MgO and magnesium-borat phases. SEM, XRD and Xray map analysis were caried out on the leached samples to characterize the  boron carbide. results showed that the reaction efficiency developed in samples with weight ratio of B₂O₃:C:Mg = 11:1.5:12, by increasing the temperature from 550 to 650 °C and magnesium powder size from 0.3 m to 3 m.

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In this work, the facile synthesis and identification of hexylmethylimidazolium bis(trifluoromethyl­sulfonyl)­amide ([HMIM]­TFSA) and hexylmethylimidazolium triethyltrifluorophosphate ([HMIM]FAP) ionic liquids (ILs), as multifunctional and multipurpose gear oil additives, is introduced. The tribological tests indicated that both ([HMIM]TFSA) and ([HMIM]FAP) ILs demonstrate antiwear/extreme pressure properties (AW/EP) to the gear oils by preventing wear and scar of the lubricated system at low and high temperatures. [HMIM]TFSA provided superior performance in comparison to [HMIM]FAP. Because of the presence of heteroaromatic imidazole moiety in the ILs structure, the prepared ILs also imparted anticorrosion, antioxidant, and anti-rust properties to the lubricant. All these observations confirmed that the ILs are single component multifunctional and multipurpose oil additives. In addition, due to avoiding the use of toxic and harmful elements in the preparation of ILs make the fabricated oils potential candidates for green lubricants.

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Carbon-based chemical substances persistence can contribute to adverse health impacts on human lives. It is essential to overcome for treatment purposes. The semiconducting metal oxide is Zinc Oxide (ZnO), which has excellent biocompatibility, good chemical stability, selectivity, sensitivity, non-toxicity, and fast electron transfer characteristics. The ZnO nanoparticles are more efficient compared to other metal oxide materials. Thus, the nanoparticles are in the present research situation to receive increasing attention due to their potential performance of the human body to feel comfortable. The nanoparticles become more promising for biomedical applications through the development of anticancer agents to recovery different types of malignant cells in the human body. The ZnO nanoparticles can be the future potential materials for biomedical applications. The purpose of this paper is to review the cost-effective approach to synthesize the ZnO nanoparticles. Moreover, these ideas can develop for synthesized ZnO biomaterial to perform easily up-scaled in biomedical applications.

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Acrylic resins are one of the most important thermoplastic resins used in various industries due to their significant properties. However, they are inherently brittle and addition plasticizers to them is very common. In this study, role of both Polyethylene Glycol (PEG) and Triacetin on the mechanical properties of acrylic resin have been investigated. To do so tensile test, bending and wear tests have been performed. To achieve the optimal mixture of plasticizers, a tensile test has been carried out, and the best percentage of the mixture has been determined. Subsequently, bending and wear tests were conducted, which showed a significant increase in the bending strength of the acrylic resin after the addition of plasticizers. Furthermore, it was found that the abrasion mechanism of the resin was significantly altered compared to its pure state.