Iranian Journal of Materials science and Engineering
Volume:12 Issue: 1, Mar 2015

In this study, the tensile and compressive behaviors of pure and hybrid composite laminates reinforced by basalt–nylon bi-woven intra-ply fabrics were experimentally investigated. Epoxy resin was used as the matrix material. The purpose of using this hybrid composite is to obtain superior characteristics by using the good strength property of basalt fiber with the excellent toughness of nylon fiber. Five different types of woven fabric were used as reinforcement with different volume percentages of nylon (0%, 25%, 33.3%, 50% and 100%). The effects of nylon/basalt fiber content on tensile and compressive parameters were studied. In addition, the after failure visual inspection and scanning electron microscopy (SEM) analysis was used to determine the extent and type of damage on tested specimens. The results indicate that the tensile and compressive performances of these composites are strongly affected by the nylon/basalt fiber content. Also, with a proper choice of fiber content, the nylon/basalt hybrid composites can achieve mechanical properties comparable with the pure ones. The stress–strain curves, after failure visual inspection and SEM analysis of tested specimens reveal that hybridization can prevent catastrophic and complete failure. In hybrid composites, the basalt and nylon fibers cannot reach their maximum strength at the same time and the progressive failure of the various fibers therefore occurred.

Multivariable regression and artificial neural network procedures were used to modeling of the input power and gas holdup of flotation. The stepwise nonlinear equations have shown greater accuracy than linear ones where they can predict input power, and gas holdup with the correlation coefficients of 0.79 thereby 0.51 in the linear, and R2=0.88 versus 0.52 in the non linear, respectively. For increasing accuracy of predictions, Feed-forward artificial neural network (FANN) was applied. FANNs with 2-2-5-5, and 2-2-3-2-2 arrangements, were capable to estimating of the input power and gas holdup, respectively. They were achieved quite satisfactory correlations of 0.96 in testing stage for input power prediction, and 0.64 for gas holdup prediction.

n this paper a finite element model has been proposed for evaluation of primary and secondary current density values on the cathode surface in nickel electroplating operation of a revolving part. In addition, the capability of presented electroplating simulation has been investigated in order to describe the electroplated thickness of the nickel sulfate solution. Nickel electroplating experiments have been carried out. A good agreement between the simulated and experimental results was found. Also the results showed that primary current density can describe the general form of thickness distribution but the relative value of current density using secondary current density can present better description of thickness distribution.

High energetic aluminum nanoparticles are mainly used as additive in solid rocket propellants. However, fabrication of these aluminized energetic materials is associated with decreasing the burning rate of propellants due to problems such as oxidation and agglomeration of nanoparticles. In this study, to improve combustion performance of aluminum nanoparticles, coating by metallic Ni shell was studied. Nickel coating of aluminum nanoparticles was performed through electroless deposition (ED); subsequently, morphology and chemical composition of Ni-coated nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). These studies show that a uniform Ni layer with a thickness of 10nm is coated on the surface of Al nanoparticles. Thermal analysis of uncoated and Ni-coated aluminum nanoparticles was done using differential thermal analysis (DTA) and thermo gravimetric analysis (TGA). The results of thermal analysis indicate that, coating the aluminum particles by Ni, leads to improvement in combustion performance of aluminum nanoparticles through decreasing critical ignition temperature, ignition delay time of the nanoparticles and promoting the ignition by exothermic chemical reactions between Al and Ni.

Pure cobalt coatings were electrodeposited on copper substrate by means of direct electric current in a chloride solution at different current densities in the range of 10-70 mA cm -2. The surface morphology and microstructure were investigated via X-ray diffraction analysis and scanning electron microscopy. Corrosion behavior of cobalt coatings was also studied in a 3.5 wt% NaCl solution using potentiodynamic polarization and impedance spectroscopy techniques. The results showed that corrosion resistance of deposits was strongly influenced by the coating’s morphology. Co deposit obtained in lower current densities exhibited the highest corrosion resistance, due to their lower grain boundaries and so the least density of active sites for preferential corrosion attacks.

In the present study, CrN, TiN and (Ti, Cr)N coatings were deposited on D6 tool steel substrates. Physical and mechanical properties of coatings such as microstructure, thickness, phase composition, and hardness were evaluated. Phase compositions were studies by X-ray diffraction method. Mechanical properties were determined by nano-indentation technique. The friction and wear behaviour of the coatings were investigated using ball-on-disc tests under normal loads of 5, 7 and 9 N at sliding distance of 500 m, at room temperature. Scanning electron microscope equipped with energy dispersive spectroscopy, optical microscope, and 2D/3D profilometry were utilized to investigate the microstructures and wear mechanisms. Wear test results clarified that the wear resistance of (Ti, Cr)N and TiN coatings was better than that of CrN coating. The wear resistance of the (Ti, Cr)N coatings was related to the Ti content in the coatings and reduced by decreasing the Ti content. The dominant wear mechanisms were characterized to be abrasive and tribochemical wear.

The aim of the present study is the prediction of critical conditions (including critical strain and flow stress) for the initiation of dynamic recrystallization during thermo-mechanical processing of plain carbon steels. For this propose, torsion tests were conducted at different temperature (1050, 1100 and 1150˚C) and strain rates (0.002, 0.02 and 0.2/s). All flow curves showed a peak stress indicating that dynamic recrystallization occurs during hot deformation. The critical stress and strain were then determined based on change in strain hardening rate as a function of flow stress. Finally, the effect of deformation conditions on these parameters was analyzed.

A method for producing high surface area nano-sized mesoporous alumina from inexpensive Iranian kaolin as raw material is proposed. In this method, first, kaolin was purified; for purifying Kaolin, High Grade Magnetic Separation and leaching with HCl and chemical bleaching treatment by using sodium dithionite (Na 2 S 2O4) as reducing agent in acidic media (H 2SO 4) were used. Purified kaolin was calcined. After that, Al (hydr) oxide from acid -leachates of calcined kaolin was precipitated with ammonia, in presence of polyethylene glycol. Finally, a white powder of nano-sized alumina particles was obtained after calcination. BET surface area, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize the sample. The resulting alumina with relatively high surface area (201.53 m 2 g -1) and narrow mean pore diameter (6.91 nm), consists of a particle size distribution ranging from 22 to 36 nm.

Ceramic-matrix composites containing TiC-TiN have been used in a variety of application because of their superior properties such as high hardness, good wear resistance and high chemical stability. In this research, effect of coke and coke/calcium beds in synthesis of Al 2O3-Ti(C, N) composites using alumino-carbothermic reduction of TiO 2 has been investigated. Al, TiO 2 and active carbon with additives of extra carbon and NaCl and without additives, in separate procedures, have been mixed. Afterwards, mixtures were pressed and synthesized in 1200oC for 4hrs, in coke and coke/calcium beds, separately. Al 2O3-Ti(C,N) composite was synthesized in ternary system of Al-TiO 2 -C with excess carbon and NaCl additives in calcium/coke bed in 1200. X-ray diffraction patterns (XRD) results showed that existence of calcium in bed resulted in intensification of reduction atmosphere in samples and formation of Ti(C,N) phase enriched from carbon was accelerated. Crystallite sizes of synthesis Ti(C,N) at 1200 °C in reducing conditions were 22-28 nm.

Mn doped ZnO nanocrystals were prepared by co-precipitation route sintered at 450 °C temperature. XRD results indicate that the samples having hexagonal (wurtzite) structure. From X-ray data it is found that the lattice parameters increase with increasing Mn concentration. The X-ray density decreases with increasing Mn concentration of Zn 1-x Mnx O nanocrystals. It indicates that the Mn ions go into the Zn site in the ZnO lattice structure. TEM results reveal that the pure and Mn substituted ZnO samples are spherical in shape with average particle size about 20-60 nm. The crystalline size and lattice strain were evaluated by Williamson-Hall (W-H) analysis using X-ray peak broadening data. All other relevant physical parameters such as strain, stress and energy density were calculated by the different models Viz, uniform deformation model (UDM), uniform deformation stress model (UDSM) and Uniform deformation energy density model (UDEDM) considering the Williamson-Hall analysis. These models reveal different strain values it may be due to the anisotropic nature of the material. It is found that the mean particle size of Zn 1-x MnxO nanoparticles was estimated from TEM analysis, Scherrer’s formula & W-H analysis is highly comparable.