Journal of Advanced Materials in Engineering (Esteghlal)

---

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.

---

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.

---

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.

---

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.

---

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.

---

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.

---

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

---

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.

---

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.

---

Sodium molybdate (Na₂MoO₄) as a grain refiner was used to refine the microstructure of Al-0.7Fe alloy. Al-Fe samples with the addition of 0.1, 0.2, 0.3, 0.4 and 0.5 wt.% sodium molybdate were fabricated by casting in sand molds at 750 ͦC. The microstructures of the as-cast samples were investigated by scanning electron microscopy (SEM) and the present phases were revealed by X-ray diffraction (XRD). The effect of sodium molybdate on the microstructure was examined by measuring the average grain sizes of the alloys, determining the widths of intermetallic compounds and carrying out hardness and tensile tests. The results showed that the addition of sodium molybdate modified the microstructure of Al-Fe alloy by reducing the average grain sizes. Also, it was found that the optimum amount of sodium molybdate to add to Al-0.7Fe alloy melt was 0.3 wt.% in this study.

---

In this study, the effect of nano-titania addition on the mechanical strength of mullite-bonded alumina-siliconcarbide nano-composites was investigated. To this end, the gel-casting process via nano-silica sol was used for shaping the nano-composite.The firing temperature of composition was determined by use of STA. The compressive and bending strengths of samples were measured after firing at 1300 °C. Besides, the physical properties, phase composition and microstructure of the composites were evaluated after firing. The results showed that the use of nano-titania up to 1 wt.% had a higher effect on improvement of nano-composite mechanical strength. The nano-titania addition led to increasing of mullite phase and higher growth of its needle-like grains. Enhancing of ceramic bonds between grains and the improvement of mechanical strength were obtained by increasing the mullite phase.

---

In this research, stiffness of polymer-clay nanocomposites was simulated by Mori-Tanaka and two and three dimensional finite element models. Nanoclays were dispersed into polymer matrix in two ways, namely parallel and random orientations toward loading direction. Effects of microstructural parameters including volume fraction of nanoclays, elastic modulus of nanoclays and interphase, thickness of interphase, aspect ratio of nanoclays and random orientation of nanoclays on elastic modulus of the nanocomposite were investigated by finite element model. Comparing the simulation with experimental results showed that the Mori-Tanak simulation results were closer to the experimental results. Analysis of results showed that the volume fraction of nanoclay, elastic modulus of nanoclay, deviation of nanoclay layers with respect to loading direction, nanoclays aspect ratio, thickness of interphase and the elastic modulus of interphase had respectively the most to the least effect on elastic modulus of nanocomposite.

---

Titanium dioxide-nickel oxide porous coatings were synthesized by Plasma Electrolytic Oxidation (PEO)/ ElectroPhoretic Deposition (EPD) in one step and within a short time. The main purpose of this research was to increase photocatalytic activity of titanium oxide by increasing surface area and coupling of titanium oxide with nickel oxide. Applied voltage effects on phase structure, surface morphology and photocatalytic efficiency of coatings were studied. Phase structure and surface morphology of the synthesized catalysts were investigated by XRD and SEM, respectively. Photocatalytic efficiency of the samples was studied through measuring the decomposition rate of 4-chlorophenol. The results showed that the coatings mainly consisted of anatase and nickel oxide phases whose amounts in coatings increased with the voltage. There was an enhancement of the photocatalytic efficiency in TiO₂/NiO composite coatings compared with TiO₂ coatings. Besides, there was an optimum amount of NiO to reach maximum photocatalytic efficiently.

---

Precipitation has always been one of the important methods in the preparation of ceramic nanopowders. In this study, the most important parameters, ageing time and concentration parameters, have been studied. Yttrium oxide (Yttria) nanopowder was synthesized by precipitation method. Yttria micropowder and ammonium hydrogen carbonate were used as precursor materials. The study involved aging time and concentration in four and three levels, repectively (3, 6, 12 and 24h for ageing time and 0.25, 0.5 and 0.75 mol/L for concentration). Synthesized phases, thermal behavior and particle size were studied by X-ray diffraction pattern (XRD), thermogravimetry (TG), differential thermal analysis (DTA) and field emission scanning electron microscopy (FE-SEM). Fourier transform infrared spectroscopy analysis (FTIR) was used for studying bonding before and after the heat treatment at 900, 1000 and 1100 ^°C.

---

Aluminium 5xxx alloys excellent properties make them suitable for many industrial applications. The corrosion behavior of this alloy family in industrial environments such as sea water is the main focus of many researches. Due to need for joining large segments of this alloys, the effect of single as well as multipass (double and triple pass) gas metal arc welding (GMAW) on microstructure and corrosion behavior of Al5083-H321 alloy was studied. For this purpose, ER5183 filler metal was used. Microstructures were evaluated using optical and scanning electron microscopy (SEM). Corrosion measurements were performed using open circuit potential test, immersion test in 3.5%NaCl solution and polarization tests. Results indicated that the corrosion resistance of the two passes weldment was improved in comparison with the base metal and its icorr and Ecorr were equal to 0.087´10^-6 (µA/cm²) and -0.4395 (V), respectively.

---

In this study, the effect of Al₂O₃ addition as a diluent during mechanically activated self-propagating high temperature synthesis (MASHS) of Al₂O₃-ZrB₂ composite was investigated. For this purpose, the thermite mixture of Al, ZrO₂, H₃BO₃ and different amounts of Al₂O₃ (0, 3, 6, 9 wt.%) were used as the raw materials and mechanically activated for 5 h, then furnace sintering was performed at 650 °C. The results showed that by increasing the Al₂O₃ content up to 6 wt.%, the intensity of exothermic peak in the DSC curves increases, but for higher additive contents it decreases. In this case, more homogenous distribution of ZrB₂ particles with finer grain size was observed.

---

In this study, synthesis of silicon nitride by mechanical alloying and the effects of important parameters of milling time and heat treatment temperature, time and rate are presented. Silicon micro powder and nitrogen gas were used as precursor materials. Synthesized phases, morphology and particle size were investigated by X-ray diffraction pattern (XRD) and Field emission scanning electron microscopy (FE-SEM), respectively. X-ray fluorescence analysis (XRF) was used for silicon nitride purity investigation.The optimum sample was produced at 30 h milling time, heat treatment at 1300 ℃ and 22 ℃/min heating rate conditions. X-ray fluorescence analysis showed more than 98% purity.

---

Nanoparticles of Mg–Co–Ti substituted strontium hexaferrite with nominal composition of SrFe_12-2x(Mg,Co)_0.5x Ti_xO₁₉ (x=0-2.5) were synthesized by a co-precipitation method. The structural, magnetic and electromagnetic properties of samples were studied as a function of x by thermal gravimetric (TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and vector network analysis. It was found that the synthesis temperature increases with an increase in Mg–Co–Ti substitution and hence the particle size decreases. The XRD results showed that whole samples had good crystallinity and with an increase incations, the impurity phase of Fe₂O₃ appears. The results of hysteresis loops indicated that the saturation of magnetization of ferrite decreases from 40 emu/g to 19 emu/g with an increase in x. The Mössbauer spectroscopy showed that the cations are substituted in the 12k site of magnetoplumbite structure. Vector network measurements showed that the doped samples had much more effective reflection loss values than those of undoped ferrites. As a result, Mg–Co–Ti doped Sr-hexaferrites with x=2 can be proposed as suitable absorbers for applications in microwave technology with a good deal of consistency.

---

Bio-inspired silver nanoparticles were synthesized with the aid of a novel method, using leaves of the plant Nigella sativa. After drying the leaves in air, they were first sweltered in boiling distilled water and the liquid was filtered subsequently. The result was the brothused to reduce solutions including various concentrations of silver nitrate in a proper amount of pH. The displayed UV–visible spectra identified formation of silver nanoparticles whenever the colorless initial acclimated mixture turned brown. The centrifuged powder samples were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (FESEM) and energy dispersive X-ray diffraction analysis (EDX) methods. The results clearly revealed that the final particles of precipitated powder are high purity agglomerates of silver nanoparticles. Besides, the effects of various amounts of the silver salt on particle size of nano silver were studied, using a particle size analyzer. FTIR results also indicated the role of different functional groups in the synthetic process.

---

In this research, TiAl/Al₂O₃ composite was synthesized from mechanically activated TiO₂-Al powder mixtures using microwave heating.The initial powder mixtures were mechanically activated and pressed into cylindrical tablets and then heated in a microwave oven. The effect of different amounts of excess Al and microwave susceptor material (SiC or graphite) on the ignition time and the resultant reaction products were evaluated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used for characterization of the synthesized samples. XRD patterns revealed that when there was no excess Al in the initial powder mixture, the main resulting intermetallic phase would be Ti₃Al with negligible amounts of TiAl, while with 10 wt% excess Al, TiAl phase could be formed in the composite product.The results also showed that microwave synthesis took place faster and more reproducible when samples were packed in the graphite powder than when placed between two SiC blocks.