Iranian Journal of Materials Science and Engineering

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Corrosion behavior of mild steel in chloride contaminated alkaline solution has been studied for the period up to 100days. Saturated Calcium hydroxide solution was used as alkaline solution and 0.5M NaCl solution was used to accelerate mild steel corrosion. The Charge transfer resistance Rct, Current density Icorr and inhibition efficiency values were obtained from tafel polarization and electrochemical impedance spectroscopic technique for sodium nitrite, sodium citrate and sodium benzoate mixed inhibitors. The results were compared with nitrite inhibitive system. The combination of nitrite inhibitor along with benzoate and citrate inhibitors enhanced the durability of mild steel through formation of nanosized -Fe2O3 film on steel suface even in presence of high chloride contamination. The results obtained from gravimetric method proved that the 100 days exposure of mild steel in nitrite with citrate, nitrite with citrate and benzoate mixed inhibitors showed the maximum inhibition efficiency of 98% in comparison with nitrite inhibitive system alone (41.5%). The maximum corrosion resistance performance of these mixed inhibitors system was due to the formation of thick layer of nano : Fe2O3 fibrous film on steel surface.

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In this paper, gold leaching of a refractory sulfide concentrate by chloride–hypochlorite solution was investigated and effects of stirring speed, temperature and particle size on the leaching rate were reported. Experimental data for leaching rate of gold were analyzed with the shrinking–core model. Results were consistent with chemical reaction control mechanism in the first 1 h of leaching and diffusion control mechanism in the second 1 h. Apparent activation energy also was found to be 22.68 kJ/mol in the first step and 3.93 kJ/mol in the second step of leaching.

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Present paper investigates the dissolution behavior of copper from chalcopyrite concentrate sample using cupric chloride solution in detail. Response surface modeling (RSM) in combination with d-optimal design (DOD) was utilized for modeling and optimizing the cupric chloride leaching process. At first, a quadratic polynomial model was developed for the relationship between the recovery of copper and influential factors. The predictions indicated an excellent agreement with the experimental data (with R² of 0.9399). Then, the effects of main factors including pH (1-4), liquid/solid ratio (2-7 mL/g), temperature (70-90 °C), CuCl₂ concentration (6-35 g/L), and leaching time (0.5-16) were determined. The findings demonstrated that the temperature and CuCl₂ concentration were the most effective factors on the dissolution rate of copper from chalcopyrite sample, while liquid/solid ratio had the lowest impact. The recovery of copper increased linearly with an increment in the liquid/solid ratio and the decrease in the pulp pH. Additionally, the recovery enhanced by increasing the temperature and CuCl₂ concentration owing the generation of Cu–Cl complexes species and reached a plateau point and then almost remained unchanged. Meanwhile, it was found out that the recovery of copper was independent of the interaction between factors. Moreover, the optimization of leaching process was carried out by Design Expert (version 7) software and desirability function method and the highest recovery of copper was found to be about 86.1% at a pH of ~1.4, temperature of 89 °C, liquid/solid ratio of 6.8 mL/g, CuCl₂ concentration of 21.79 g/L and leaching time of ~8 h.
 

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Microscopic studies has shown that adjacent to the interface between cement paste and aggregate, there exists an area with high porosity and low binding compounds that is referred to as interfacial transition zone (ITZ). ITZ in concrete and mortar imposes a number of negative effects, including flexural and compressive strengths reduction and permeability enhancement. That’s why many research attempts have been devoted to limit ITZ and its negative effects. The present study investigates the possibility of utilizing fine Portland cement (PC) clinker as a reactive aggregate in mortar for the same purpose. For this, natural quartz sand in normal mortar (NM) was totally replaced with PC clinker of the same particle size distribution and the most important engineering properties of the new mortar referred to as Reactive Aggregate Mortar (RAM) were measured and compared with NM as control. The results of compressive strengths measurements represented 65% and 21% increases at curing ages of 7 and 90 days, respectively, for RAM compared to NM. Chloride penetration depth in RAM displayed reductions by about 33% and 26% after 14 and 28 days of exposure, respectively. The effect of PC clinker reactivity on the microstructure and size of ITZ was studied by using scanning electron microscopy.

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Iron oxide nanoparticles has attracted extensively due to their supermagnetic properties, preferred in biomedicine because of their biocompatibility and potential nontoxicity to human beings. Synthesis of iron nanoparticles (FeNPs) was prepared with the help of ferric chloride and ferrous sulphate by using the coprecipitation method. The variation and combination of ferric and ferrous concentrations affect the physical and magnetic properties of iron oxide nanoparticles.  The effect of 0.1 M ferric and ferrous concentration on iron oxide nanoparticles studied separately and in combination. The obtained nanoparticles were characterized by Particle size, zeta potential, Ultraviolet (UV-visible), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Thermal gravimetric analysis (TGA), and Vibrating-sample magnetometer (VSM) techniques. Particle size was below 200nm and zeta potential was within the limit for all the batches. UV visible spectra at 224 nm, and FTIR exhibit two peaks at 510 and 594 cm-1, indicating iron oxide NPs and XRD confirmed the crystalline nature of Fe. SEM showed a spherical shape for all batches. The use of a combination of ferric and ferrous is more effective than its individual use. TGA and VSM studies confirmed its magnetic properties.