Journal of Advanced Materials in Engineering (Esteghlal)

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In this study, at first Al-Al2O3 composite powders having different volume fractions of Al2O3 (0, 10, 20, 30 and 40 vol.%) were produced by low energy mechanical alloying, which were used as foam materials. Then, composite foams with 50, 60, and 70 percent of porosity were produced by space-holder technique. Spherical carbamide particles (1-1.4 mm) were used to achieve spherical porosities. In order to investigate the compressive behavior of foams, the compression test with strain rate of 10-3 S-1 was performed on the foam samples. The results showed that the compressive properties depended on the volume fraction of Al2O3 and porosity fraction. Generally, by decreasing the porosity fraction, the compressive properties were improved. The composite foams containing 10 vol.% Al2O3 showed superior compressive properties in comparison to other foams studied in this work.

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This study was intended to investigate the effect of injection of aluminium into the crystallizator on type, composition and activity of inclusions in low carbon steel grade USD7. The steel is made in Zob-e-Ahan Isfahan factory and its porosities and inclusions results in the problem of rupturing during rolling process. To improve the quality of this steel, 2.4 mm diameter pure aluminum wires were injected in to the crystallizator at the rate of 2, 4, 6 or 8 m/min in certain periods and then sampling was done. The results indicated that much of the added aluminum changed to aluminum oxide slag, and the remaining part altered the chemical composition of the inclusions. Increased aluminum caused an increase in the activity of alumina and reduction in the activity of other oxides in the slag and existing inclusions in the melt. By increasing Al2O3 activity from 0.313 to 0.649, the Al2O3 formation and oxygen exclusion probability increased in the system. Scanning electron microscopy showed that without aluminium injection, most of inclusions were FeO-MnO type placed around existing porosities in the ingot. The optimum rate of aluminum injection was found to be 4 m/min.

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In the present study, 304 stainless steel (SS) was electrochemically plated with nanocrystalline Mn-Cu alloy coatings from a bath containing ammonium sulfate. The effects of current density on the microstructure, crystallographic structure, and chemical composition of the deposits were studied. The results showed that at low current densities, discontinuous coatings with a large amount of Cu can be obtained. Further increase in current density resulted in amorphous, compact and heterogeneous coatings with a small amount of Cu. The presence of Cu at low contents in precipitated coatings delayed the phase transformation of as-deposited ductile g-Mn to the brittle and hard a-Mn. However, the results did not show any specific changes in the grain size of the coatings with variation of current densities.

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In the present investigation, spherical nanoparticles of nickel ferrite with uniform structure were successfully produced by hydrothermal method in the presence of polyethylene glycol (PEG) as a polymeric surfactant at 180°C for 12 hour aging time and the effects of the synthesis time, temperature and surfactant were investigated. According to the X-ray analysis, conversion of nickel oxide and hematite to nickel ferrite was a way to produce NiFe2O4. At 140‌°C, agglomerated particles without specific shape were formed, but at 180°C particles were homogenous with spherical shape. Saturation magnetization increased by increasing the hydrothermal process aging time.

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In this research, crystallization of Fe36Cr12Mo10 and α-Fe phases in devitrification of Fe51Cr18Mo7B16C4Nb4 amorphous alloy was studied using X-ray diffraction and transmission electron microscopy. For evaluation of crystallization kinetics, differential scanning calorimetric tests were carried out at different heating rates. Results showed that two-step crystallization led to the formation of Fe36Cr12Mo10 and α-Fe phases in the structure of alloy. Activation energy of crystallization of Fe36Cr12Mo10 and α-Fe phases measured according to Kissinger-Starink model were 747 and 880 kJ/mol, respectively. Results growth mechanism along with the decreasing nucleation rate in crystallization of Fe36Cr12Mo10 and α-Fe phases.

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In this study, AlN whiskers were prepared in a tube furnace at 1000˚C for 1h with 500 nitrogen gas flow. Al powders with particle size of 3 μm and 45 μm and NH4Cl were used as raw materials. SEM, TEM and XRD analysis were used to characterize AlN whiskers. The results showed that the diameters of AlN whiskers would range from 140 nm to 340 nm if different amounts of NH4Cl and 3 μm Al powder were used. In the case of using NH4Cl more than 40wt%, pure AlN without any unreacted Al was formed as the final product. Using NH4Cl and Al with particle size of 45 μm led to AlN whiskers with 630 nm to 870 nm in diameter. By adding 50%wt NH4Cl, pure AlN was formed. The diameter of the whiskers was increased by increasing NH4Cl content in starting materials (about 200 nm). Also, an increase in the diameter of AlN whisker resulted from coarse Al powder. By adding NH4Cl to Al, thermodynamically spontaneous cholororination - nitridation reactions were increased in vapor phase and whiskers and pure AlN powder were produced.

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In this investigation, the effect of Polyvinylpyrrolidone (PVP) additive on microstructure, morphology and magnetic properties of cobalt ferrite nanoparticles prepared by hydrothermal method was studied. X-ray diffraction (XRD) studies in different synthesis conditions showed the formation of cobalt ferrite and cobalt oxide. Comparing IR spectrum of PVP additive, sol prepared before hydrothermal process and C-0.1PVP3, 190 obtained by FTIR spectroscopy indicated the formation of bond between PVP and surface of metallic hydroxide and cobalt ferrite particles, which prevented them from growing and coarsening. Scanning electron microscope (SEM) was used to study the morphology of samples. According to vibration sample magnetometer (VSM) results, as PVP amount increases from 0.1 to 0.3 volume percent, coercive field increases from 298 to 684 Oe and saturation magnetization decreases from 58 to 51 emu/g.

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The positive effect of Si and Zn ions on bone formation and metabolism has already been confirmed. The aim of this study was preparation and characterization of Willemite (Zn2SiO4) for the repair of bone defects. Willemite was prepared through solid state reaction. Phase analysis and chemical compositions were investigated. The zeta potential of the nanoparticles was determined in physiological saline, and compressive strength and Young's modulus of the samples were measured. The ability of hydroxyapatite formation was investigated in simulated body fluid (SBF) and cytotoxicity of the particles was evaluated in contact with human bone marrow stem cells. The results of this study showed that Willemite nanobioceramic is obtained with the expected chemical composition and negative zeta potential. The results also showed that the hydroxyapatite forming ability in SBF was not strong. MTT assay confirmed the cell proliferation and availability in contact with a specific concentration of Willemite nanoparticles. All these findings indicate that Willemite nanobioceramic with proper biocompatibility can be suggested as a novel biomaterial for the repair of bone defects.

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Effects of discontinuous ultrasonic treatment on the microstructure, nanoparticle distribution, and mechanical properties of cast Al413-SiCnp nanocomposites were studied. The results showed that discontinuous ultrasonic treatment was more effective in improving the mechanical properties of the cast nanocomposites than the equally timed continuous treatment. The yield and ultimate tensile strengths of Al413-2%SiCnp nanocomposites discontinuously treated for two 20 minute periods increased by about 126% and 100% compared to those of the monolithic sample, respectively. These improvements were about 107% and 94% for the nanocomposites continuously treated for a single 40 minute period. The improvement in the mechanical properties was associated with severe refinement of the microstructure, removal of the remaining gas layers on the particles surfaces, more effective fragmentation of the remaining agglomerates as well as improved wettability and distribution of the reinforcing particles during the first stage of solidification.

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Ni–SiC composite coatings are successfully employed as a protective coating in the inner walls of engine cylinders. In this study, Ni-SiC, Ni-SiC-MoS2 and Ni-SiC-Gr composite coatings were prepared from a sulfamate bath. Both mechanical and ultrasonic stirring were used simultaneously during the process. Taking into account the working temperature of engine cylinders, the wear behavior of coatings was evaluated at 25 to 300 ºC and the high temperature tribological properties of the coatings were investigated. Based on the results obtained from the wear tests, all three coatings showed almost good friction coefficient values at 25 and 100 ºC, which were close to each other. By increasing the temperature to 200-300 °C, the friction coefficient and weight loss values strongly increased. However, addition of solid lubricants caused the values to decrease. The Ni-SiC-Gr coating at all temperatures showed a good and stable behavior.

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this study, MoSi2-TiB2 nanocomposites with 10 and 20 wt.% of TiB2 were synthesized by mechanical alloying through two different methods. In the first method, elemental powders of molybdenum, silicon, titanium and boron were milled together for 60 hours. In the second method, MoSi2 was made by 30-hours milling of Mo and Si. Then, commercial TiB2 was added to the matrix and milling was continued for another 30 hours. Heat treatment was carried out on the resultant specimens at 1000˚C for 60 min. The effect of mechanical alloying on grain size and lattice strain was investigated by Williamson-Hall method using XRD patterns. The mechanical properties of the samples were determined by hardness test. It was found that TiB2 added to MoSi2 increased hardness considerably. Agglomeration process was carried out on the powders to be used in thermal spray process. The morphology and microstructure of the milled powders before and after agglomeration process were studied by SEM. The sphericity and particle size distribution of agglomerated particles were evaluated using Clemex software. The results showed that the nanocomposite powder produced by the first method had a higher quality for thermal spray process due to its higher hardness compared to the second one. It also had adequate particles sphericity.

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Based on molecular dynamics simulation results, a model was developed for determining elastic properties of aluminum nanocomposites reinforced with silicon carbide particles. Also, two models for prediction of density and price of nanocomposites were suggested. Then, optimal volume fraction of reinforcement was obtained by genetic algorithm method for the least density and price, and the highest elastic properties. Based on optimization results, the optimum volume fraction of reinforcement was obtained equal to 0.44. For this optimum volume fraction, optimum Young’s modulus, shear modulus, the price and the density of the nanocomposite were obtained 165.89 GPa, 111.37 GPa, 8.75 $/lb and 2.92 gr/cm3, respectively.

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The aim of this investigation was to produce Ti47Al48Mn5 intermetallic compounds with different microstructures in order to study their oxidation behavior. The reason for selecting manganese as an alloying element was to enhance the toughness of the compound. Ti47Al48Mn5 alloys were obtained through mechanical alloying, cold pressing and heat treatment. XRD results showed that milling of the elemental powder mixture for 30 hours causes the formation of Al and Mn in Ti solid solution, while by increasing milling time up to 50 hours, amorphization of powder mixture occurs. To obtain duplex and fully lamellar microstructures, the mechanically alloyed powders were cold pressed and then heat treated at 1100 °C and 1400 °C in argon atmosphere for 50 hours, respectively. The results of the oxidation test at 1000 °C revealed that the different microstructures of Ti47Al48Mn5 alloy investigated in this study have little effect on the oxidation resistance, and similar oxidation mechanisms existed for the two microstructures.

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To evaluate the effect of inoculant addition on functionally graded microstructure of centrifugally cast Al-Mg2Si composites, two cylinders of Al-13.8 wt.% Mg2Si with and without the addition of 1 wt.% Al-5Ti-B inoculant were cast in a vertical centrifugal casting machine. The chemical composition, microstructures and microstructural phases of the different radial sections of the cast cylinders were studied using induction coupled plasma (ICP) method, optical/scanning electron microscopes, and X-ray diffractometry, respectively. The results showed that in the inoculant content cylinder, owing to the prevailing thermal regime as well as the specific mode of eutectic solidification in this composite, the titanium and boron compounds were segregated towards the middle layer of the cylinder and caused the formation of primary Mg2Si particles and non-eutectic Al () in this layer. In addition, due to the effect of centrifugal force during solidification, a higher volume fraction of the light primary Mg2Si particles, according to Stocks law, was segregated towards the inner layer of the cast cylinders.

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In this investigation, the effect of heat treatment on magnetic properties of glass and nano-structured cobalt-ferrite glass-ceramic was studied. The glass was synthesized in the system of Na2O-Fe2O3-CoO-B2O3-SiO2. Based on DTA results, heat treatment was done at different times and temperatures. X-ray diffraction pattern of glass-ceramic showed the crystallization of CoFe2O4 and some nonmagnetic phases. The highest magnetization of 11.8 emu/g was obtained for the sample heat-treated for 2 hr at 670C in graphite bed. Average crystallite size of CoFe2O4 in this sample was 50 nm. Scanning Electron Microscopy (SEM) confirmed the formation of cobalt ferrite nanoparticles in the glass matrix.

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In the present study, the copper anode slime was leached in chloride media. Then, pregnant leach solution (PLS) was purified using solvent extraction method and Octanol-kerosene solution. HAuCl4.2L was determined as the extracted macromolecule, and separation of impurities, such as copper, iron and selenium was done in the presence of gold. McCabe-Thiele diagram of Au–HCl (3 M)– Octanol (40% v/v) in O/A=3/4 showed that Au concentration in aqueous phase decreased from the initial value of 200 to 7 mg/L, after 5 stages. Ammonia solution was proposed as the stripper and McCabe-Thiele diagram was presented to obtain the number of gold stripping steps by ammonia solution

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Certain amount of retained austenite can increase ductility of steels because of the TRIP phenomenon during plastic deformation. One method for achieving this is partitioning of carbon into austenite to stabilize it at room temperature. The quenching and partitioning (Q&P) heat treatment leads to a microstructure consisting of martensite and stabilized retained austenite between martensite plates, which provides a better combination of strength and ductility. In this study, the effect of parameters of Q&P process (quenching temperature, partitioning temperature and partitioning time) on the microstructure and retained austenite volume fraction of a low alloy medium carbon steel was investigated. The results showed that the high increase in partitioning time causes the disappearance of martensite blades and reduction of austenite volume fraction. However, increasing of partitioning temperature made the retained austenite films become thicker and its volume fraction increase. On the other hand, by increasing the quenching temperature, carbon content of retained austenite increased sharply.

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This paper reports on the mechanical properties of the dissimilar joints between AISI 316 austenitic stainless steel and St 37 low carbon steel achieved using friction stir welding technique. The welding was carried out by means of rotational speed of 800 rpm and linear speeds of 50,100,150 mm/min. EDS and XRD techniques were employed in order to determine possible phase transformations. Tensile test, shear punch test and microhardness measurements were conducted to evaluate the mechanical properties of the joints. The results of phase investigations showed that no carbide and brittle phase were detected at the joint boundary. Also, tensile test results demonstrated that failure occurred in the St 37 base metal. According to the shear punch test, the highest ultimate shear strength and yield shear strength was achieved for the sample welded at rotational speed of 800 rpm and linear speed of 150 mm/min, while this sample showed the least elongation. In addition, the highest microhardness was measured in the stir zone of austenitic stainless steel sample welded in the above mentioned welding condition, which can be attributed to the decrease in grain size caused by recrystallization process.

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In this study, the effect of mechanical alloying on the microstructure and phase constituents of Mg-6Al-1Zn-1Si system was investigated. To understand the thermal behavior, isothermal annealing was performed at three different temperatures of 350, 400 and 450 °C for 1h. The results showed the grain size initially decreases with increasing the milling time up to 35h and then slightly increases. In contrast, the lattice strain increases sharply with increasing the milling time up to 35h and then decreases. Second-phase intermetallic particle Mg2Si was produced during annealing and the amount of this phase was increased with increasing annealing temperature. The mechanical alloying process decreased the formation temperature of Mg2Si.

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In the last decade, a significant progress has been made in the wearable medical devices. Scientists are extensively involved in the design of the flexible instruments equipped with garments to fulfill the daily needs and requirements. The fulfillment of this demand particularly needs a conductive fabric substrate with a high level of homogeneity, and the lowest barrier against electrical current. In this study, textile based ECG electrode was prepared by screen printing of activator followed by electroless plating of copper particles. The data acquisition showed the best outcome with pH=8.5 and the plating temperature of 70 ˚C. The electrical resistance showed a range around 0.08 Ω/sq, which sounds quite proper for ECG signal acquisition since the potential difference according to heart activity on skin surface is in milivolt range. We tested the cardiac signal with a reference electrode of Electroshock monitoring system and the results revealed a very high quality receiving signal. Employing of these types of sensors in textile surface due to their flexibility can bring the users more freedom of action.