Sharif Digital Repository

Effects of SiC nanoparticles addition on synthesis and antibacterial properties of TiCu nanocrystalline powder prepared through high energy mechanical milling were studied. The results showed that the synthesis of TiCu powder in the presence of the nanoparticles was accelerated and after mechanical alloying for 20 h, a TiCu/SiC nanocrystalline powder with the crystallite size <5 nm, and 3.3% lattice micro-strain obtained. Further milling resulted in fully amorphous TiCu intermetallic alloy with more uniform distribution of SiC nanoparticles. The antibacterial activity of the synthesized powders was investigated by disk diffusion test. The TiCu/SiC nanocomposites showed enhanced antibacterial... 

In this work, nanostructured aluminum titanate (Al2TiO5 or AT) was synthesized by the citrate sol gel method. Then, different volume fractions of this ceramic were blended with Al powder through different durations of the high-energy vibratory milling. The effect of mechanical milling on the thermal degradation of AT in exposure to Al and formation mechanism of in-situ Al2O3 and Al3Ti particles were explored in three conditions: (i) in the powder form; (ii) after annealing of green compact; and (iii) after hot extrusion. In the powder form, it was shown that the mechanical milling is able to significantly diminish the thermal stability of AT, so that the required temperature for the Al3Ti... 

In the present study, hardness and tribological properties of nanostructured copper reinforced with SiC nanoparticles of various volume fractions (0, 2, 4, and 6 vol%) were investigated. The nanocomposites were fabricated by high-energy mechanical milling and hot pressing method. The Cu-SiC nanocomposites showed enhanced hardness and wear resistance against WC counterface. The hardness and wear resistance of the nanocomposite increased with increasing the amount of SiC nanoparticles up to 2 vol% in the matrix, but they decreased at higher percentages of SiC (4 and 6 vol%). Flake formation-spalling and abrasion were identified as the predominant wear mechanisms. It was found that reducing the... 

In this study, an equiatomic mixture of Ni and Ti powders has been mechanically milled for 180 h in a planetary mill in order to study the product phase of milling process. Miedema's semi empirical method has been used in order to calculate the energy of solid solution and amorphous phases and the effect of defects like dislocations and grain boundaries have been considered in this thermodynamic approach. The results showed that amorphous phase is more stable than solid solution after mechanical milling process. It seems these results are in contrast with Mousavi et al. [1] results but there are some points that we should consider in this approach. Applying of common tangent rule and... 

The effect of milling time on the magnetic properties of FINEMET amorphous ribbons has been investigated using X-ray diffraction, Mössbauer spectroscopy, thermo-magnetic measurements, transmission electron microscopy and SQUID magnetometery. Ribbons were melt-spun at a wheel speed of 38 ms-1 and then mechanically milled for different periods up to 45 min. The results showed that the partially crystallization of the amorphous powder occurs during milling. TEM observations confirmed the formation of small volume fraction of the crystalline phase with ∼9 nm crystallite size in the amorphous matrix for the ribbon milled for 45 min. Thermo-magnetic measurements indicated the enhancement of the... 

Nanostructured Cu and Cu-2. vol% SiC nanocomposite were produced by high energy mechanical milling and hot pressing technique. Microstructure development during fabrication process was investigated by X-ray diffraction, scanning electron microscope, scanning transmission electron microscope, and electron backscatter diffraction techniques. The results showed that the microstructure of copper and copper-based nanoco mposite composed of a mixture of equiaxed nanograins with bimodal and non-random misorientation distribution. The presence of SiC nanoparticles refined the grain structure of the copper matrix while the fraction of low angle grain boundaries was increased. Evaluation of mechanical... 

In this study, the microstructural and mechanical features of monolithic pure Cu and Cu matrix nanocomposites reinforced with three different fractions (2, 4, and 6. vol%) of SiC nanoparticles (n-SiC) fabricated via a combination of high energy mechanical milling and hot pressing techniques were investigated. The fabricated composites exhibited homogeneous distribution of the n-SiC with few porosities. It was found that the grain refinement, the planar features within the grains, and the lattice strains increase with increase in the n-SiC content. The yield and compressive strengths of the nanocomposites were significantly improved with increases in the n-SiC content up to 4. vol%; then they... 

The effect of high-energy ball milling on the textural evolution of alumina nanopowders (compaction response, sinter-ability, grain growth and the degree of agglomeration) during post sintering process is studied. The applied pressure required for the breakage of the agglomerates (P y) during milling was estimated and the key elements of compressibility (i.e. critical pressure (P cr) and compressibility (b)) were calculated. Based on the results, the fracture point of the agglomerates decreased from 150 to 75 MPa with prolonged milling time from 3 to 60 min. Furthermore, the powders were formed by different shaping methods such as cold isostatic press (CIP) and uniaxial press (UP) to better... 

The effect of particle size, lattice strain and crystallite size on the hydrogen desorption properties of nanocrystalline magnesium hydride powder was investigated. Commercial MgH2 powder was milled in a Spex 8000M up to 16 h and its structural evolution and desorption characteristics at different time intervals were examined using various analytical techniques. At the early stage of milling, the formation of metastable γ-MgH2 phase was noticed. While the crystallite size gradually decreased to 12 nm with increasing the milling time, the accumulated lattice strain gained a maximum value of 0·9% after 4 h milling. The highest drop in the desorption temperature (∼100°C) was attained at the... 

Al6063 powder was subjected to severe plastic deformation via high-energy mechanical milling to prepare ultrafine-grained (UFG) aluminium alloy. Uniaxial compression test at various temperatures between 300 and 450 °C and strain rates between 0.01 and 1 s-1 was carried out to evaluate hot workability of the material. Microstructural studies were performed by EBSD and TEM. The average activation energy and strain rate sensitivity of the hot deformation process were determined to be 280 kJ mol-1 and 0.05, respectively. The deformation temperature and applied strain rate significantly affected the grain structure of UFG Al alloy. A finer grain structure was obtained at lower temperatures and... 

A mixture of MgO and graphite with a molar ratio (1:1) was subjected to planetary ball milling for 1, 2, 4, and 8 h with the intention of enhancing carbothermic reduction reaction of MgO during subsequent thermal treatment. Unmilled and milled mixtures were characterized using a combination of X-ray diffraction (XRD) analysis, Raman spectroscopy, scanning electron microscopy (SEM), surface area analysis (SSA), and thermogravimetric analysis (TGA). The reduction reaction of milled samples occurred at lower temperature than that of the unmilled sample. A longer milling time engenders a lower reaction temperature. These results are attributable to the increased interfacial area of the sample... 

This paper presents experimental results on the synthesis of nanostructured aluminium matrix nanocomposite powders by comilling of nanoscaled SiC and Al2O3 particles and micrometric aluminium powder. The effect of the nanometric reinforcement particles on the mechanical milling (MA) process of the soft matrix was studied by scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscopy, laser particle size analyser and standard metallographic techniques. It was found that at the early stage of milling, the nanoparticles are smeared on the surface of the aluminium powder and thus do not significantly contribute in the MA process. As the milling continues, the hard... 

The hydrogen desorption properties of nanocrystalline magnesium hydride processed by high-energy mechanical milling was investigated. MgH2 powder was milled for various times (up to 16 h) under a high purity argon atmosphere and the effect of milling on the particle size and morphology, grain refinement, lattice strain, and desorption temperature was studied. It was shown that accumulated lattice strain combined with nanometric grain structure significantly decrease the desorption temperature. The effect of powder particle size was found to be of less importance. The lowest desorption temperature was obtained after 4 h high-energy milling. Nanostructured magnesium hydride with grain size of... 

In the present work, ultrafine-grained Al-5vol.% Al2O3 nanocomposite was synthesized through mechanical milling followed by direct powder extrusion method. The characteristics of the processed nanocomposite were examined by electron microscopy (SEM and TEM), Xray diffraction (XRD), tensile test and Vickers hardness measurement. It was shown that the addition of the reinforcement nanoparticles accelerates the milling process of the aluminum matrix and enhances the grain refinement of the aluminum matrix. An improved mechanical strength as compared with Al-Al2O3 microcompoiste was obtained. A dimple-type fracture mode was observed, which is a clear evidence of micro-deformation. In addition,... 

The morphological and microstructural changes during mechanical milling of Al powder mixed with 5 vol% nanoscaled alumina particles (35 nm) were studied. The milling was performed in a planetary ball mill under argon atmosphere for various times up to 24 h. The process was also conducted for Al and Al-5 vol% Al2O3 (1 μm) powders to explore the role of reinforcement nanoparticles on the mechanical milling stages. The results showed that the addition of hard particles accelerate the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Meanwhile, the structural evolution during mechanical milling of the microcomposite powder occurred faster than that of...