فهرست مطالب

  • Volume:6 Issue:3, 2019
  • تاریخ انتشار: 1397/10/29
  • تعداد عناوین: 9
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  • Mahdi Raoufi *, A. Zolanvari, Majid null zarezadeh Pages 3-12

    In this study, thin layers of titanium nitride (TiN) were deposited on H13 steel substrates at different duty cycles and temperature of 520 ˚C using plasma assisted chemical vapor deposition (PACVD). Uniaxial residual stress was calculated by X-ray diffraction (XRD) and Sin2 Ψ method. Then the residual stress of the samples were measured by Grazing Incidence X-ray Diffraction (GIXRD) method and lattice parameter diagrams versus f(Ψ). Depth of penetration and texture coefficient in the samples were also evaluated. The surface morphology was examined using field-emission gun scanning electron microscope (FESEM) and the relationship of the stress and micro hardness test was also expressed. The results showed that by reducing duty cycles, residual stress decreases as well as with more changes of the lattice parameter, more changes of residual stress will be seen. Also, the microstructure result was in good agreement with theory and clearly displayed spherical morphology and uniform distribution of the created phases

    Keywords: TiN, plasma assisted chemical vapor deposition, residual stress, GIXRD
  • Azize Alayli Gungor *, Hayrunnisa Nadaroglu, Aynur Babagil, Hicran Onem Pages 13-25

    In this study, the synthesis of ceria (CeO2) nanoparticles (NPs) was examined by the biosynthesis method. Then, enzyme-like features of synthesized nanoceria were examined. Peroxidase enzyme from fig (Ficus carica) was used as a synthesis and stabilizer reagent. Furthermore, it was investigated whether the obtained nanoceria has superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) activities. UV-VIS absorption spectroscopy was employed for monitoring of creation of ceria nanoparticles. The characteristics of the obtained ceria nanoparticles were studied with X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Also, cerium oxide NPs showed enzyme-like activities, and its activities were determined with specific enzyme activity measuring methods. Surface morphology and size of the synthesized ceria were investigated by chromatographic techniques. The diameter of the biosynthesized ceria nanoparticles was determined to be 14 nm using XRD chromatogram. Advantages of unique properties of nanoceria have been promising for being enzyme-like reagent in nano-biotechnological investigations. This research explored and discussed if ceria nanomaterial s different kinds of enzymes. We examined their kinetics, mechanisms and applications, including in superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) activities. The results showed that the ceria oxide nanoparticles exhibited catalase, peroxidase and superoxide dismutase activities.

    Keywords: Ceria nanoparticles, Bio reduction, Fig (Ficus carica), Peroxidase
  • Asadollah Hassankhani * Pages 26-33

    ESW as a natural byproduct, although non-hazardous and contains calcium, magnesium carbonate and protein, is commonly disposed in landfills without any pretreatment because it was traditionally useless. In this regards, we wish to report the synthesis of a novel CaO/Ca2Fe2O5 nanocomposite based on ESW. At the first, eggshell (ES) nanopowder was prepared by ball-milling. Then, the CaO/Ca2Fe2O5 nanocomposite as a novel and heterogeneous nanomaterial was synthesized by simply adding an aqueous solution of FeSO4 on the ES nanopowder. After coating the FeSO4 on the surface of the ES powder, the precipitate was collected and calcinated. The synthesized nanocomposite was fully characterized by FTIR, FESEM, TEM, TGA, EDX and XRD analysis. The result was shown that the porous structure of the ESW as a cheap and biomaterial source of Ca was provided good contact area for growing the Fe nanoparticles. The suggested strategy for the synthesis of CaO/Ca2Fe2O5 nanocomposite is very interesting due to use of green and low cost starting materials and its simple and clean preparation procedure. The present procedure was successfully provided a useful application of ESW from the environment to synthesis the novel nanomaterials.

    Keywords: Ca2Fe2O5, eggshell waste, CaO, nanocomposite, biomaterial
  • Esmaeil Shahimoridi, Seyed Mohammad Kalantari *, Arman Molaei Pages 34-44

    Recently, Functionally Graded Scaffolds (FGSs) have attracted a lot of attention as bone replacements due to their gradient porosities as well as a bone structure. In present study titanium functionally graded scaffolds (FGSs) were fabricated by powder metallurgy route using Mg and carbamide as space holders. The arranged layers with 20, 40 and 60 Vol.% porosities were compacted in steel die using uniaxial pressure of 500 MPa before sintering in sealed quartz tubes at 1100 °C for 3 hours. Image analyzing results and scanning electron microscope (SEM) observations showed more regular shapes and sizes of pores in FGSs using Mg as a space holder compared to carbamide. The observed compressive strength and Young’s moduli of the FGSs having Mg as a space holder were in the range of 47- 160 MPa and 25-75 GPa , respectively which can be appropriate as bone replacements. The results of MTT assay showed that the values of proliferation rate were higher in samples produced using Mg.

    Keywords: Biocompatibility, compressive properties, Functionally Graded Scaffold (FGS)
  • Masoud Azadi Moghaddam *, Farhad Kolahan, Meysam Beytolamani Pages 45-56

    The main objectives of this research are, therefore, to assess the effects of process parameters and to determine their optimal levels machining of Inconel 718 super alloy. gap voltage, current, time of machining and duty factor are tuning parameters considered to be study as process input parameters. Furthermore, two important process output characteristic, have been evaluated in this research are material removal rate (MRR) and surface roughness (SR). Determination of a combination of process parameters to minimize SR and maximize MRR is the objective of this study. In order to gather required experimental data, design of experiments (DOE) approach, has been used. Then, statistical analyses and validation experiments have been carried out to select the best and the most fitted regression models. In the last section of this research, simulated annealing (SA) algorithm has been employed for optimization of the EDM process performance characteristics. A set of verification tests is also performed to confirm the accuracy of the proposed optimization procedure in determining the optimal levels of machining parameters. The results indicate that the proposed modeling technique and SA algorithm are quite efficient in modeling and optimization of EDM process parameters.

    Keywords: Electrical Discharge Machining (EDM), Inconel 718 super alloy, Optimization, Simulated annealing (SA) algorithm, Analysis of Variance (ANOVA)
  • Sifiso P Nkosi *, Krishnan Kanny Pages 57-65

    A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. Hemicellulose has a random, amorphous structure with little strength. It is easily hydrolyzed by dilute acid or base as well as myriad hemicellulase enzymes. In this study, lignin and hemicellulose was extracted from sugarcane bagasse using the ammonium hydrolysis process. The extraction of hemicellulose was carried out at 250C (room temperature) with 25% Ammonia Solution. The sugarcane bagasse extract was used together with starch to produce thin films. The films were characterized using Fourier transformed infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The FT-IR and XRD analysis of the films confirmed the presence of hemicellulose and lignin. The TGA shows an average of 16.75% and 50.61% for lignin and hemicellulose respectively. The crystallinity index values obtained from XRD showed that film materials were amorphous and have higher values when compared with untreated SCB, due to the partial removal of hemicellulose after ammonium hydrolysis treatment.

    Keywords: Ammonium hydrolysis, Sugarcane bagasse (SCB), Lignin, Hemicellulose, Crystallinity Index (CI)
  • Farzaneh Moosavi, Mojdeh Erfanian, Ramin Hashemi *, Reza Madoliat Pages 66-79

    In this article, the effect of different yield functions on prediction of forming limit curve (FLC) for aluminum sheet is studied. Due to importance of FLC in sheet metal forming, concentration on effective parameters must be considered exactly in order to have better theoretical prediction comparing experimental results. Yield function is one of the factors which are improved by adding new coefficients that follows the behaviour of material with good approximation, so applying different yield functions can change shape and level of FLCs. In this study the yield criteria which are used in determination of forming limit curves, are Hill48, Hosford, BBC2008, Soare2008, Plunkett2008 and YLD2011. The YLD2011 yield function is more appropriate than the other yield function for prediction of the FLD of aluminum alloy. The well-known Marciniak-Kuczynski (M-K) theory and voce hardening law have also been used. To verify the numerical results, the obtained results have been compared with available experimental data.

    Keywords: Forming Limit Diagram, Aluminum, Yield Functions, Marciniak-Kuczynski theory
  • Amir Rofigar Haghighi, Akbar Heidarpour *, Mohsen Eshaghpour Soorani, Mehdi Mansouri Pages 80-88

    In this study, the crystallization behavior of melt-spun Al87Ni10La3 amorphous phase was investigated by using X-ray diffraction and non-isothermal differential thermal analysis techniques. The results demonstrated that the amorphous phase exhibited two-stage crystallization on heating, i.e., at first step the amorphous phase transforms into α-Al phase and at second step Al11La3 and Al3Ni intermetallic phases precipitate, simultaneously. The activation energies of the crystallizations of the amorphous phase were evaluated by the Kissinger equation using the peak temperature of the exothermic reactions. The values of two-step crystallization activation energies were approximately 173.7±6 and 278.4±5 kJ/mol, respectively. The Avrami index was calculated for the first and second step of crystallizations and obtained 0.9 and 3.8 respectively. This kinetics investigation indicated that in the first step of crystallization of Al87Ni10La3 alloy, the nucleation rate decreases with time, and the crystallization is governed by a three-dimensional diffusion-controlled growth, while the second stage was in interface control regime.

    Keywords: Amorphous alloy, Rapid solidi?cation, Crystallization, Thermal Analysis
  • Mahdi Yeganeh, Mahdi Omidi *, Arash Etemad, Mohammad Reza Rostami, Mohammad Esmaeil Shafiei Pages 89-97

    The idea of smart inhibitors is based on the principle that an inhibitor is used where needed. This will reduce the use of inhibitors and protect materials in hostile environments. On the other hand, direct addition of the inhibitor within the coating can be harmful, resulting in the loss of inhibitors ability, deterioration in the coating or both of them. An appropriate method for solving these problems is the use of neutral host systems that act as a nanocontainer system or reservoir and are filled with arbitrary inhibitor. In this study, mesoporous silica with and without corrosion inhibitor (benzotriazole) were dispersed within an epoxy coating to protect the steel sheet. Then, the corrosion properties of these coatings with and without mesoporous silica particles were compared in a saline solution. Electrochemical studies showed that coatings containing particles could protect the surface of steel in the chloride environment. The impedance modulus (Z100 mHz) and corrosion resistance (Rcorr) regarding the coating embedded with mesoporous silica doped with inhibitor showed a value about one order of magnitude higher than that of a coating without inhibitor. This behavior could be due to the release of benzotriazole at the interface of the epoxy coating. In addition, the scratched coating with mesoporous silica doped with inhibitor exhibited less corrosion products compared to the coating without inhibitor which also confirmed the release of benzotriazole on demand of the corrosion process.

    Keywords: mesoporous silica, corrosion, coating, benzotriazole