Iranian Journal of Materials science and Engineering
Volume:7 Issue: 2, Jun 2010

nanoparticles. All the extracts were used separately for the synthesis of gold anoparticles through the reduction of aqueous AuCl gold ions to gold nanoparticles. The ethanol extract of black tea and its tannin free ethanol extract produced gold nanoparticles in the size ranges of 2.5-27.5 nm and 1.25-17.5 nm with an average size of 10 nm and 3 nm, respectively. The prepared colloid gold nanoparticles, using the ethanol extract of black tea, did not show the appropriate stability during storage time (24 hours) at 4 showed no particle aggregation during short and long storage times at the same coditions. To the best of our knowledge, this is the first report on the rapid synthesis of gold nanoparticles using ethanol extract of black tea and its tannin free fraction. In this research the ethanol extract of black tea and its tannin free fraction used for green synthesis of gold4¯. Transmission electron microscopy and visible absorption spectroscopy confirmed the reduction ofoC. In contrast, gold colloids, which were synthesized by a tannin free fraction

nanocrystalline nickel samples with the grain size of ~25 nm were prepared via direct current electrodeposition and aluminized for different durations by pack cementation method at 500 means of SEM, EDS and XRD techniques. According to results, short time aluminizing resulted in the formation of a single aluminide layer whereas at long duration two distinct aluminide layers were formed. The growth kinetics of the coating was non-parabolic at short times while it obeyed the parabolic law at long duration. The parabolic growth rate constant of single phase coating formed on electrodeposited samples was about 30 ìm / h1/2 approximately 3 times greater than the data reported for coarse grained nickel (8.4 ìm / h1/2). Meanwhile, the overall growth rate constan was decreased to 11.7 ìm / h1/2, when double aluminide layers formed on nanocrystalline nickel. In this research, aluminizing behavior of ultra fine-grained nickel was investigated. For this purpose,oC. The aluminide layers were examined by

properties of AA6082 aluminum alloy. Considering that aging phenomenon affects the distribution of alloying element in matrix, and the fact that different distribution of alloying elements has different impediments to dislocation movement, a material model based on microstructure, has been developed in this research. A relative volume fraction or mean radius of precipitations is introduced into the flow stress by using the appropriate relationships. The GA-based optimization technique is used to evaluate the material constants within the equations from the uni-axial tensile test data of AA6082 alloy. Finally, using the proposed model with optimized constants, the flow behavior of the alloy at different conditions of heat treatment is predicted. The results predicted by the model showed a good agreement with experimental data, indicating the capability of the model in prediction of the material flow behavior after different heat treatment cycles. Also, the calculated flow stress was used for determination of the material property in AbaqusSoftware to analyze the uniaxial compression test. The force- displacement curves of the analysis were compared to the experimental data obtained in the same condition, and a good agreement was found between the two sets of results. A novel constitutive equation has been proposed to predict the effect of aging treatment on mechanical

mechanical properties of AISIH 13 hot-work tool steel have been studied. Cast samples made of the modified new steel were homogenized and austenitized at different conditions, followed by tempering at the specified temperature ranges. Hardness, red hardness, three point bending test and Charpy impact test were carried out to evaluate the mechanical properties together with characterizing the microstructure of the modified steel using scanning electron microscope. The results show that niobium addition modifies the cast structure of Nb–alloyed steel, and increases its maximum hardness. It was found that bending strength; bending strain, impact strength, and red hardness of the modified cast steel are also higher than those of the cast H13 steel, and lower than those of the wrought H13 steel. In this research, the effects of partially replacing of vanadium and molybdenum with niobium on the

has been investigated. It has been shown that the mechanism of leaching reaction is diffusion through the product layer and does not undergo any change as a result of mechanical activation in a wide range of experimental conditions.Leaching rate is strongly influenced by milling intensity and the effect of ball to powder mass ratio is stronger than milling time. Curve fitting of experimental data shows that leaching rate constant is approximately a linear function of ball to powder mass ratio, while it obeys a power function with regard to the milling time.The kinetics of chalcopyrite leaching in a ferric sulfate media for raw and mechanically activated samples

as magnetic materials, semiconductors, pigments, catalysts, refractories and electronic ceramics. In this paper, we reported the preparation of NiAl The resulting powder was chracterized by XRD, particle size analysis and SEM. The XRD patterns show that thecombustion technique was excellent to prepare single – phased cubic NiAl found to be around 14 nm. From the particle size analysis, it was found that the 50 % of the particles lie below 30 µm. The micrographs show the formation of fluffy agglomerates composed of fine particles.Spinels constitute an advanced group of materials with great technologial appeal, being able to be applied2O4 spinels by low temperature combustion technique using glycine and urea as fuels.2O4 particles and the crystallite sizes were

the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance.In the present work, study on the kinetics of cobalt electrowinning and the mechanism of the involved reactions have been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The effects of temperature and scan rate parameters were studied on electrowinning of cobalt by cyclic voltammetrytechnique. The diffusion coefficient and rate constant of the reactions were measured and calculated by performed experiments.Nowadays cobalt is mostly produced through the electrowinning process of sulfate solutions. Regarding to