فهرست مطالب

  • Volume:8 Issue:3, 2012
  • تاریخ انتشار: 1391/07/11
  • تعداد عناوین: 8
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  • S. F. Mahmud*, J. Taniguchi Pages 127-134
    The price of single point diamond tools with a sharp tip is very high due to complex machining process and highly expensive machining equipments. Yet, the performance is not quite satisfactory. In this paper, we have presented a very simple and cost effective machining process for the sharpening and polishing of diamond stylus using low energy reactive ion beam machining (RIBM). In our method, machining of the stylus was done by 500 eV O+/O2 + ion beam at an off-normal ion incidence angle under rotating condition. Mechanically coarse-finished styli of two different size and shape were used as the specimen- stylus of apex angle 90° with the radius of curvature 5μm and stylus of apex angle 60° with the radius of curvature 2μm. In both cases, the stylus was sharpened down to an apex angle of around 55° with the radius of curvature ≤100 nm. The tilt angle of the specimen for shrapening was predicted from simulation. The surface of the processed stylus was completely smooth and ripple-free and the surface defects on the pristine stylus were also eliminated by the proposed machining method. Due to low energy RIBM, the irradiation damage on the diamond crystalline structure was minimal.
    Keywords: Ultera, sharpening, Diamond, Ion Beam Machine
  • F. Abbasi Nargesi*, R. Azari Khosroshahi Pages 135-142
    In this research, mechanical alloying was used to produce Ti-50Al, Ti-45Al-5Cr and Ti-45Al-5W (at%) alloys. The effect of ternary addition (Cr and W) on microstructure and production efficiency of TiAl alloy were investigated. Alloying was performed in a planetary mill and the milling time varying from 5 to 70h. The structural evaluation in these powders was done by X-ray diffraction (XRD) technique and Scanning Electron Microscopy (SEM) during mechanical alloying and after annealing at 1100°C in vacuum oven. The results showed only a complete amorphous phase after 50h of milling of Ti-50Al powder mixture, but with 5at% addition of Cr, the Cr (Ti, Al) solid solution within the amorphous matrix were identified after 70h milling and with 5at% addition of W, the W lattice was remained with amorphous phase. The time required for solid solution or amorphous phase formation was longer in Cr and W containing powders. After annealing of mechanically alloyed Ti-50Al, the γ-phase with high purity and nanostructured size was produced and for sample with Cr addition, the TiAl(γ) with amount of Ti3Al(a2) were formed and for sample with W addition, the duplex phase (γ+a2) with a minor amount of W, were formed.
    Keywords: mechanical alloying, Titanium Aluminide, Chromium, Tungsten, Nanostructure
  • S. H. Tohidi, A. J. Novinrooz*, M. Derhambakhsh, G. L. Grigoryan Pages 143-148
    Various concentrations of copper were embedded into silica matrix to xerogel forms using copper source Cu(NO3)2∙3H2O. The xerogel samples were prepared by hydrolysis and condensation of Tetraethyl Ortho-Silicate (TEOS) with determination of new molar ratio of the components by the sol-gel method. After ambient drying, the xerogel samples were heated from 60 to 1000˚C at a slow heating rate (50°C/h). The absorption and transmittance spectra of the gel matrices were heat treated at different temperatures. The loss of water and hydroxyl group from the silica network changed the spectral characteristics of Cu2+ ions in the host silica. The shift observed for the broad band of the absorption spectrum of the samples heated up to 600°C was attributed to the legend field splitting and partial removal of the hydroxyl group from the silica matrix. Absorption spectrum of the samples heated to 1000°C confirmed the conversion of Cu2+ ions to Cu+ ions. The effects of thermal treatment were characterized by Fourier Transmission Infrared (FTIR) and Raman spectroscopy at different temperatures. Also, the Transmission Electron Microscope (TEM) micrographs confirmed the average pores size of about 50 nm.
    Keywords: Copper oxide, Nano, composite, Thermal treatment, Silica, Sol, gel
  • M. Hatami, M. H. Majles Ara*, A. Rostami, M. Dolatyari, M. Mahmudi, H. Baghban Pages 149-156
    Well-defined crystalline PbSe nanocubes and nanospheres have been synthesized through a simple hydrothermal method by using Pb2+- EDTA and Pb2+- oleylamine complexes at 180°C for different reaction times. Composition and morphology of the samples have been characterized by means of XRD and SEM. Gradual release process of Pb2+ from Pb2+-EDTA and Pb2+-oleylamine complexes can adjust the growth rate. Both EDTA and oleylamine play important roles in the crystal growth of PbSe nanomaterials. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that PbSe have a direct energy band gap of 0.51 eV. The optical properties, including the dielectric and absorption of the compounds are calculated by DFT method and analyzed based on the electronic structures. Two absorption bands have been observed in the absorption spectra identified from density of state (DOS) calculations.
    Keywords: nanostructures, Lead selenide, Optical properties, DFT calculations
  • B. Maddah, H. Chalabi* Pages 157-164
    Nanocrystalline magnesium oxides were prepared by sol–gel method and were characterized by X-ray diffraction, N2-BET, SEM and infrared spectroscopy techniques. The results confirmed the formation of Nano- MgO materials with crystallite size in range of 5-20 nm and surface areas of 336-556m2/g. The product has been tested as destructive adsorbent for the decontamination of (2-chloroethyl) ethyl sulfide (2-CEES), a mimic of bis(2-chloroethyl) sulfide(“HD” or Mustard Gas). Destructive adsorbent reaction has been carried out in heptanes and methanol media. The reaction was investigated by GC-FID and GC–MS techniques. Reaction rate in heptane has been observed to be higher than methanol. It seems a nonpolar media aided material transfer to the reactive surface sites without blocking them.
    Keywords: Nano, MgO, Decontamination, (2, chloroethyl) ethyl sulfide
  • A. Nasiri, M. Shariaty-Niasar Shariaty-Niasar*, Z. Akbari Pages 165-170
    Improving barrier properties through the use of nanocomposites is an important area of research, especially for the food packaging industry. In this work, Titanium dioxide (TiO2)/Low density Poly Ethylene (LDPE) nanocomposites were synthesized as the oxygen barrier layers through the co-extrusion process. The Oxygen permeability of the nanocomposite with 4% of TiO2 decreased for about 16% compared to the pristine LDPE. Furthermore, the rancidity of almonds in the packaging which is made of the former is about 78% less than the latter. Therefore, from the data obtained from the permeation, mechanical and degradation experiments, it can be concluded that these nanocomposites provide promising applications as O2-barrier and antidegradation agents in food packaging.
    Keywords: Nanocomposite, TiO2 nanoparticle, packaging, permeability
  • M. Fereydouni, S. Sabbaghi*, R. Saboori, S. Zeinali Pages 171-174
    Polyanionic cellulose polymer is used as an additive in drilling mud in order to decrease water loss and mudcake- thickness. In this study effect of bulk and nanosize polyanionic cellulose on water loss and mud-cakethickness in mud drilling is investigated. Polyanionic cellulose nanoparticles are made by using of ball milling. Size of nanoparticles is measured by Particle size analyzer. Polyanionic cellulose and polyanionic cellulose nanoparticles which were prepared by Hamilton batch mixer and with certain percent suggested by API, were added to water-based mud drilling. Filter press system is used to measure the amount of water loss and mud cake thickness. It was found that adding polyanionic cellulose nanoparticles in comparison with conventional polyanionic cellulose resulted in desirable reduction of amount of water loss and mud cake thickness.
    Keywords: Polyanionic cellulose, Nanoparticles, Mud drilling, Water loss, Mud cake thickness
  • F. Ramezani Pages 181-184
    Paper chromatography is an analytical technique for separating and identifying mixtures of materials. It is a useful technique since it is relatively quick, and requires small quantities of the material. By emergence of nanotechnology, paper chromatography has found many applications in biology and biotechnology. In this study, we employed gold and silver nanoparticles to detect protein bands after the paper chromatography method. We first performed paper chromatography on a solution containing Bovine Serum Albumin (BSA) protein. Then, the gold and silver nanoparticles were exploited for paper coloration. As a result, it was noticed that location of the protein bands was clearly distinct and detectable with this technique.
    Keywords: chromatography, detection, Nanoparticle, protein