فهرست مطالب

Advanced Materials and Processing - Volume:3 Issue: 3, Summer 2015

Journal of advanced materials and processing
Volume:3 Issue: 3, Summer 2015

  • تاریخ انتشار: 1394/08/24
  • تعداد عناوین: 7
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  • M. Riazat, Ghader Faraji Pages 3-12
    The influence of the sample size (diameter while keeping the length constant) in equal channel angular pressing (ECAP) of pure aluminum is examined using finite element method (FEM) and experiment. Different sized aluminum rods were processed via ECAP and the effect of sample size on the strain homogeneity, process load, and the ratio of the friction to the total force were evaluated. The results showed that there is no distinct trend in variation of the strain homogeneity when the sample diameter is changed though largest diameter sample exhibits the best strain homogeneity. It was apparent that an increase in the sample diameter caused to an increase in the total required load. A decrease in the sample size led to a significant increase in the ratio of the friction to the total force. On the other hand, the friction force is more sensitive than the deformation force to the sample size. More precisely, the friction to total load ratio may be related to the ratio of sample length to the sample diameter (l/d). In a constant sample length, friction to total load ratio amplifies significantly with a decrease in the sample diameter. The present study showed some limitation for the scaling up of the ECAP process for the industrial application especially when increase in the sample length. It may be concluded that ECAP processing is not suitable method for producing of long UFG materials.
    Keywords: ECAP, size effect, strain homogeneity, total force, friction force
  • Behrooz Shayegh Pages 13-24
    The TiO2–SiO2 thin films were deposited on AISI 316L stainless steel via sol-gel method. Then, the effect of the added amount of SiO2 on the structure, morphology and mechanical properties of the films and corrosion behavior of AISI 316L stainless steel substrate were investigated. So, X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, depth-sensing indentation technique supporting micro-scratch mode and potentiodynamic polarization test were used. It was observed that the appropriate amount SiO2 addition into TiO2 film not only decreased the particle size of TiO2–SiO2 crystal but also could help to improve the surface quality. The mechanical and tribological properties of the films were found to be improved in the range of 10–15%mol SiO2 addition compared with the pure TiO2. The minimum root mean square value was obtained from the film with a silica content of 10%mol. In addition, the corrosion behavior of AISI 316L stainless steel was improved by adding 15%mol SiO2. Under UV illumination conditions, photo-generated electrons accumulated in this film could perfectly protect the substrate photocathodically.
    Keywords: TiO2–SiO2 nanocomposite films, sol, gel method, depth, sensing indentation technique, photocathodic protection effect
  • Mohammad Velashjerdi, Hossien Sarpoolaky, Alireza Mirhabibi Pages 25-34
    Zirconium Diboride (ZrB2) powder was synthesized at low temperature via a Direct Molten Salt Reaction (DMSR) method. The influence of different salt compositions including eutectic mixture of (KF-NaF), (KF-KCl) and (KCl-NaCl) on the morphology and purity of the reaction products was studied. The obtained samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore, the formation mechanism of ZrB2 was investigated by DTA/TG. The results show that alongside eutectic mixture of chloride salt, ZrB2 powder can be obtained with eutectic mixture of fluoride salt. In addition, obtained ZrB2 powder without additional salt has hexagonal prism morphology, whereas ZrB2 particles prepared with eutectic mixture of fluoride salt have higher purity and particle size and hexagonal morphology as well. Synthesized ZrB2 Powder in chlorofluoride salt has lower particle size and purity and non-uniform morphology. Synthesized ZrB2 powder is different from starting material in term of morphology and particle size therefore the dissolution–precipitation mechanism may play a dominant role on the synthesis of ZrB2 during DMSR process.
    Keywords: Zirconium Diboride, Molten Salt, Reaction, Low Temperature, Composition
  • Dalia Radwan, Mohamed Ebiad, Sara Mekhail Pages 35-46
    Shape selective xylene production is very important in the polymer industry because of its extensive use as raw material for monomer preparation. The acidity associated with the Lewis and Broensted centers present in the pillars interlayered clay and its textural properties allows good catalytic activity and shape selectivity toward p-xylene production. So, in the present study, ultrasonic and microwave as a new and efficient method was used in the preparation of Co, Cr and ZrO2-pillared clay with enhanced textural properties, improved thermal stability and significant reduction in processing time. Catalytic alkylation of toluene with methanol was carried out over the prepared catalysts in a catalytic flow system operated under atmospheric pressure at a temperature range 250-450oC. Results indicated that the pillaring of montmorilonitic clay material with polyoxy-metalic cations (Zr-, Cr- and Co-) improves the texture properties and thermal stability of the obtained catalysts. The Co-PILC catalyst is the most active and selective catalyst towards p-xylene formation, i.e. Co-PILC catalyst is a shape selective for p-xylene formation.
    Keywords: Pillared clay, ultrasonic, Microwave, alkylation, shape selective catalysts
  • Hamed Aghajani Derazkola, Majid Elyasi, Morteza Hossienzadeh Pages 47-60
    In this article effects of friction stir welding (FSW) tool rotational and traverse speeds were studied on heat generation and temperature distribution in welding zone of AA1100 aluminum alloy and A441 AISI joint. Computational fluid dynamics method was used to simulate the process with commercial CFD Fluent 6.4 package. To enhance the accuracy of simulation in this Study, the welding line that is located work-pieces interface, defined with pseudo melt behavior around the FSW pin tool. Simulation results showed that with increase of FSW tool rotational speed, the generated heat became more and dimensions of the stir zone will be bigger. The calculation result also shows that the maximum temperature was occurred on the advancing side. The computed results demonstrated that with increasing tool linear speeds the heat generation experienced growth down trend. With increasing traveling speeds the time to reach maximum temperature in stir zone growth but the tool rotational speed dose not effect on time to reach maximum temperature. The model outcomes show that more than 85% total heat was produced by tool shoulder and the maximum heat with selected parameters in this study was 935 kelvin degrees. The computed results shows that the maximum value of strain rate achieved was 29 S-1 for A441 AISI side and 42 S-1 at AA1100 side.
    Keywords: Friction stir welding, Dissimilar joint, Computational fluid dynamic, Thermal modelling
  • Akbar Chami, Bahman Nasiri-Tabrizi Pages 61-70
    Due to the high hardness and wear resistance, electroless nickel-boron (Ni-B) coatings have found numerous applications. In the present study, the influence of the heating rate on the morphological features of oxidized electroless Ni-B coatings was investigated. The oxidation behavior of electroless coating layers was studied with TGA method under non-isothermal conditions at heating rates 5, 9 and 13 °C/min. The phase compositions, elemental constituents and microstructural characteristics were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) techniques, respectively. Results showed that the morphological features of the oxidized coating were influenced significantly by the heating rate so that under the heating rate of 5 °C/min the morphology of oxidized layer was a porous film with an average pore size of around 2 μm. With increasing the heating rate to 9 °C/min, more recessed pores or intervals were gradually overlaid by a film. Further increasing the heating rate to 13°C/min caused to the formation of polygonal protuberances on the surface.
    Keywords: Electroless plating, Ni, B, Morphological features, Oxidation, Heating rate
  • Ahmad Gholizadeh Pages 71-83
    In this work, structural and magnetic properties of LaMnO3+δ compound prepared by citrate precursor method and annealed in presence of oxygen are investigated. The structural characterization of LaMnO3+δ by X-ray powder diffraction and using X’pert package and Fullprof program is evidence for a rhombohedral structure (R-3c space group) confirmed by FTIR measurement. The magnetic measurements show a super-paramagnetic behavior of LaMnO3+δ due to low values of coercive field and romance magnetization and also high value of saturation magnetization. In addition, a comparative study of the crystallite size of the compounds obtained from powder XRD is reported. The Williamson-Hall analysis, size-strain plot and Halder-Wagner methods were used to study the individual contributions of crystallite sizes and lattice micro-strain on isotropic line broadening of all the reflection peaks of the LaMnO3+δ compound. The results show the Halder-Wagner method is more accurate, with all data points touching the fitting line better than the other methods. The crystallite sizes estimated from XRD (30.86 nm) and particle size estimated from TEM method (36 nm) and also the magnetic core size (33.6 nm) estimated from magnetic measurement agree well, while a little difference reflects a spherical shape of the nanoparticles.
    Keywords: Manganite, Nano, Perovskite, Hexagonal to Rhombohedral Lattice Conversion, Peak Broadening