فهرست مطالب

  • Volume:51 Issue: 2, 2018
  • تاریخ انتشار: 1397/09/12
  • تعداد عناوین: 12
|
  • Hossein Asghari Shivaee , Nahid Izadpanah Mehrkish, Mahdiyeh Kakoo, Tayebeh Gheiratmand, Hamid Reza Madaah Hosseini Pages 96-100
    In this study, melt-spun Finemet ribbons were coated by a thin layer of SiO2 using dip coating method. Amorphous ribbon prepared by melt spinning method and dip coating were done by using a solution of tetraethylen orthosilicate as a SiO2 precursor, ethanol as solvent and distilled water for hydrolysis. Different thicknesses of SiO2 layer, namely 304, 349, 451, 526 and 970 nm were obtained proportional to the number of dipping. Surface morphology and chemical composition of the coatings were analyzed by using Scanning Electron Microscope equipped with an energy dispersive spectroscope. The results clearly verified the presence of Si and O elements and confirmed the presence of silica layer on the surface of all coated ribbons. Microstructure and surface morphology of samples showed a smooth and brittle layer. Electrical resistivity of the samples was measured with a standard four-point probe device. The results confirmed an intense in increase of resistivity. Average value of electrical resistivity for coated samples was around 104 Ω-m compared to 10-6 Ω-m for Finemet ribbons. Capacity of the samples was evaluated by electronic parameter analyzer device in two different frequencies of 100 kHz and 1000 kHz. Impedance measurements of coated samples in 100 and 1000 kHz showed an increase about 70 and 10 times respectively.
    Keywords: Finemet, Electrical resistivity, SiO2, Dip coating, Surface morphology
  • Raana Sarvari, Samira Agbolaghi , Younes Beygi, Khosrowshahi, Bakhshali Massoumi, Ali Bahadori Pages 101-114
    The hydrophilic, conducting, biocompatible and porous scaffolds were designed using poly(2-hydroxy ethyl methacrylate)-co-poly(N-isopropylacrylamide)-co-poly(ε-caprolactone) (P(HEMA-b-NIPAAm-b-CL))/polyaniline (PANI) for the osteoblast applications. To this end, the PHEMA and P(HEMA-b-NIPAAm) were synthesized via reversible addition of fragmentation chain transfer (RAFT) polymerization, and in next step, the ε-caprolactone was polymerized from –OH group of PHEMA segments through the ring opening polymerization (ROP). The electroactivity, mechanical properties, and hydrophilicity of designed scaffolds played an important role in the adhesion, differentiation, and proliferation of MG63 cells. By using the PHEMA and PNIPAAm, the hydrophilicity and biocompatibility, and by employing the PCL, the appropriate mechanical properties were acquired. The addition of PANI in the composition induced the conductivity to scaffolds. The morphology, electrical conductivity, biocompatibility, hydrophilicity and mechanical characteristics of the nanofibers were thoroughly investigated. The scaffolds possessed a porous nanostructure (nanofiber diameter ranged in 60–130 nm) with a large surface area, electrical conductivity of 0.03 S cm–1 and contact angle of 49 ± 5 ͦ , which imitated the natural microenvironment of extra cellular matrix (ECM) to regulate the cell attachment, proliferation and differentiation. In vitro cytocompatibility studies were performed over 168 h and indicated that the nanofibers were non-toxic to MG63 cells and potent to the artificial nanostructured osteoblasting
    Keywords: Scaffold, osteoblast, electrospun nanofiber, poly(2-hydroxyethylmethaacrylate), poly(N-isopropylacrylamide), polycaprolactone
  • Mehrdad Dorri, Cyrus Zamani , Alireza Babaei Pages 115-122
    Nanostructured manganese cobalt oxide spinel (MnCo2O4) are prepared by co-precipitation method and calcined at 650 and 750°C. Morphological studies show that by increasing the calcination temperature from 650 to 750°C, morphology of the particles changes from quasi-plate to polyhedral. The MnCo2O4 calcined at 650°C could deliver an initial discharge capacity of 1438 mAh g-1 under current density of 45 mA g-1. The effects of calcination temperature on the initial discharge capacity of the electrode have also been investigated, The MnCo2O4 calcined at 650°C shows the higher initial discharge capacity due to the higher surface area (due to smaller particles) and weaker crystallinity. The influences of electrode porosities also have been studied, which suggest the electrochemical performance is determined by both the particle-to-particle contact and wettability of the electrode. An increase of the internal resistance of the electrode is observed with increasing electrode thickness (active material loading), which is the main factor responsible for the significant capacity loss for thicker electrode.
    Keywords: Lithium-Ion Battery, MnCo2O4, Electrode Porosity, Transition Metal Oxide Anode, Discharge Capacity
  • Majid Naseri , Mohsen Reihanian, Ehsan Borhani Pages 123-138
    In the present work, nano/ultrafine structured Al/Brass composite was produced by accumulative roll bonding (ARB) up to eight cycles. The evolution of grain refinement and deformation texture and their effect on the mechanical properties were investigated. It was observed that by increasing the ARB cycles, due to the difference in flow properties of the metal constituents, brass layers necked, fractured and distributed in aluminum matrix. After eight cycles, a composite was produced with almost homogeneous distribution of brass fragments in aluminum matrix. Microstructural characterization by electron backscatter diffraction (EBSD) revealed the formation of bimodal structure consisting of equiaxied grains with an average size of ~120 nm and elongated grains after eight cycles, which was attributed to the occurrence of redundant shear and recrystallization. The crystallographic texture results indicated that the major texture components in the aluminum matrix were Brass {011}, S {123}, Goss {011} and Rotated Goss {011}. Moreover, it was concluded that Goss {011} and Rotated Goss {011} components appeared for high number of ARB cycles due to the adiabatic heat during ARB processing. The tensile strength of Al/Brass composite reached 330 MPa, which was 4.23 times and 1.83 times higher than those of annealed aluminum and monolithic aluminum, respectively. Finally, fracture surfaces of samples were studied, using field emission scanning electron microscope (FESEM), to reveal the failure mechanism.
    Keywords: Aluminum matrix composites (AMCs), Accumulative roll bonding (ARB), Electron backscatter diffraction (EBSD), Microstructure characterization, Deformation texture, Mechanical properties
  • Bahareh Hakimi, Mohammad Ghorbanpour , Atabak Feizi Pages 139-146
    Photocatalyst nanocomposites of ZnO/bentonite clay are synthesized by Solid-state ion exchange method. Ion exchange intercalation process of clays is used to incorporate the catalyst into the basal space of the layered structure of clays. The purpose of this study is to find a new method, which is focused on simplifying and saving time to prepare ZnO-bentonite composite with photocatalyst property. The synthesis of ZnO-doped bentonite nanocomposite is accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The nanocomposites are characterized by morphological (SEM), optical (UV/vis reflection) and analytical (EDX) techniques. According to SEM results, after ion exchanging, the parent structure of bentonite remains and only the distance between flakes increased significantly. EDX analysis clearly suggest the success of ion exchange of the expense of Ca2+, Na+ and Mg2+ cations with Zn2+. The calculated band gap for the composites were 3.14 eV (10 min), 2.64 eV (20 min) and 2.54 eV at longer times, respectively. All the prepared composites showed acceptable degradation performances. The greatest photocatalytic activity is detected in ZnO/bentonite composite solid-state ion exchanges which lasts 60 and 90 min. Leaching test results showed that the concentrations of Zn are less than 4 mg/l between 0 and 6 h. These results indicated that the photocatalytic property of composites would last longer
    Keywords: ZnO, bentonite, Nanocomposites, Solid-state ion exchange, Photocatalysts
  • Erfan Alimohammadi, Saeed Sheibani , Abolghasem Ataie Pages 147-152
    Strontium carbonate (SrCO3) is one of the most important strontium compounds that have been used in a variety of technological and industrial applications. In the present investigation, nano-structured strontium carbonate was synthesized by mechano-chemical reaction of celestite ore (SrSO4) collected from Dasht-e kavir, Iran and sodium carbonate during high energy mechanical milling.The milling were performed for different durations of time up to 16 hours in a high-energy planetary ball mill with the rotational speed and ball to powder weight ratio of 300 rpm and 30, respectively. X-Ray diffraction (XRD), X-ray fluorescence spectrometer (XRF) and scanning electron microscope (SEM) were used to characterize the obtained samples. XRD results showed that at a Na2CO3:SrSO4 molar ratio of 1.05:1, mechano-chemical reaction started after 1 hour of milling. Although the longer milling times gives a more conversion of SrSO4 to SrCO3 but it has not been completed even after 16 hours of milling. However, by increasing the molar ratio of Na2CO3:SrSO4 to 1.25:1, the SrCO3 formation was completed after 2 hours. The results also showed that the mean crystallites sizes of produced nano-powder were approximately 32 nm. XRF result indicated that the final product was obtained with a purity of 95 wt.%. SEM studies confirmed the formation of SrCO3 nano-powder with a mean particle size of 80 nm.
    Keywords: Strontium carbonate, Celestite ore, Nano-structured, Mechanochemical
  • Morteza Saghafi Yazdi , Mohammad Noghani, Alireza Najari Pages 153-162

    In this study, a high energy planetary ball milling technique was used to synthesize nano-crystalline Mo-Cu alloys. Molybdenum trioxide (MoO3) and copper oxide (CuO) were used as the starting materials. Carbo-thermal co-reduction of mixed Mo and Cu oxides powders was done with milling followed by a heat treatment at a high temperature. Differential thermal analysis/thermogravimetric (DTA/TG) was used to determine the heat treatment temperature of activated powders. X-ray diffraction (XRD) analysis was used to investigate the phase structure during the milling and heat treatment. Field emission scanning electron microscopy (FESEM) has been employed to investigate the morphology of powder particles. It was found that the complete carbo-thermal reduction of the oxides mixture may not be possible by the mechanical milling at the ambient temperature and based on thermodynamic investigations, thermal activation was necessary to reduce a MoO3-CuO mixture to a metallic structure. Some peaks at 400, 600 and 950 °C from DTG results of the mixture sample milled for 10 h were observed which were related to the Cu6Mo5O18, MoO2-Cu and Mo formation during carbo-thermal reduction of the MoO3-CuO mixture, respectively. XRD results showed 10 h milled sample after reduction at 1000 °C contained nano-crystalline Mo-Cu alloys with a mean crystallite size of 42 nm for Mo and 37 nm for Cu calculated by the Scherrer equation
    Keywords: Nano-crystalline, Mechanical milling, Mo-Cu alloy, Nano particles, Refractory
  • Mahdi Madandar Motlagh, Seyyed Morteza Msoudpanah , Masoud Hasheminiasari, Rasoul Beigdelou Pages 163-168
    Magnetite (Fe3O4) nanoparticles were synthesized by coprecipitation route. Coprecipitation is a simple, reproducible and accessible technique relying on the coprecipitation of Fe2+ and Fe3+ cations by NaOH as base at low temperature (~80 °C). In this work, the role of different solvents (H2O, ethylene glycol, diethylene glycol, triethylene glycol) on phase, structure, microstructure and magnetic properties were characterized by X-ray diffractometry, electron microscopy and vibrating sample magnetometry techniques. Single phase Fe3O4 nanoparticles were crystallized in water and organic solvents. The particle size decreased from 53 to 33 nm by precipitating in the presence of organic solvents in contrast to water due to the introduction of more nucleation of particles caused by decrease in surface energy. Furthermore, the organic solvents prevent particle growth by adsorbing on the nucleus surface, leading to smaller particles. The as-coprecipitated Fe3O4 nanoparticles exhibited ferromagnetic behavior without any coercivity, confirming the superparamagnetism. The maximum saturation magnetization (Ms) of 54 emu/g was achieved for the as-coprecipitated Fe3O4 nanoparticles using ethylene glycol as solvent, possibly due to their higher crystallinity. However, the Ms decreased to 41 and 45 emu/g for precipitation in the presence of diethylene glycol and triethylene glycol, respectively, due to the more particle size reduction, leading to the spin canting on the particle surface
    Keywords: Coprecipitation, Fe3O4, Solvent, Magnetic properties
  • Mohsen Balavar, Hamed Mirzadeh Pages 169-173
    Thermal treatments and thermo-mechanical processing routes were applied on a conventional structural steel (st37 steel: 0.12C-1.11Mn-0.16Si) for improvement of tensile properties and enhancement of work-hardening behavior. Full annealing resulted in a sheet with coarse ferrite grains and pearlite colonies arranged alternatively in distinct bands, which showed high ductility, low strength, and the presence of the yield point elongation at the beginning of the plastic flow. The cold-rolled sheet, however, showed poor ductility but much higher strength level. The dual phase (DP) sheet, resulted from intercritical annealing in the austenite plus ferrite region, showed a remarkable strength-ductility balance. The latter was related to the excellent work-hardening behavior as a result of the glide and interaction of the quench-induced unpinned dislocations. A bimodal-sized ferritic structure with the appearance of a poor strain hardening regime after experiencing a high yield stress was obtained from the subcritically annealed cold-rolled DP microstructure. The ultrafine-grained sheet was processed by applying the abovementioned route on a martensitic microstructure, which resulted in low ductility but high strength at ambient temperature. These results demonstrated the ability to control the properties of conventional steels by simple thermal and thermo-mechanical treatments. Low carbon steel, Grain refinement, Mechanical properties, Strain hardening rate
    Keywords: Low carbon steel, Grain refinement, Mechanical properties, Strain hardening rate
  • Majideh Banaei, Mansoor Anbia , Maryam Kazemipour Pages 174-182
    In this work, we have modified a synthesized Y-type zeolite (Si/Al = 2.5), with three different amines to investigate of the influence of adsorbent’s surface modification on CO2 selectivity over CH4. The pristine and amine-functionalized NaY zeolites were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), and N2 adsorption. The results showed that the structure of zeolite was preserved after amine modification. The adsorption capacity of CO2 and CH4 on these adsorbents was measured by the volumetric method at 298 K and 348 K. In comparison to CH4, CO2 was preferentially adsorbed on these adsorbents. the results demonstrated that incorporation of amines into zeolites structure improved significantly the selectivity towards carbon dioxide so that the optimal selectivity of CO2 over CH4 reached to 4.04 on zeolite modified with 2-methylaminoethanol at 348 K. Chemical interaction between adsorbate and sorbents as well as the steric effects were assessed to be the main reasons of high selective adsorption of carbon dioxide on amine-functionalized zeolites. Two of the most common adsorption models, the Langmuir and Sips isotherms, were used to correlate the experimental data of CO2 adsorption on the adsorbents The results revealed that the amine-functionalized NaY zeolites could be a good sorbent for use in flue and natural gas separation processes
    Keywords: CO2, CH4 separation, Y-Type Zeolite, adsorption, Amine modification
  • Malihe Zeraati, Gholam Reza Khayati Pages 183-192
    Cu–Cr-Zr alloys had wide applications in engineering applications such as electrical and welding industrial especially for their high strength, high electrical as well as acceptable thermal conductivities and melting points. It was possible to prepare the nano-structure of these age hardenable alloys using mechanical alloying method as a cheap and mass production technique to prepare the non-equilibrium materials such as solid solution structures. In this study, artificial neural networks (ANNs) program was developed to establish the relationship between the practical parameters of mechanical alloying, i.e., weight percentages of Cr and Zr as alloying element, milling times, milling speed, sintering time and temperature, on the micro hardness of prepared Cu-Cr-Zr nanostructure alloys. The results of sensitivity analysis showed that the alloying elements and sintering temperature had the highest and lowest effect on the micro hardness of products, respectively. Also, the optimum milling speed and sintering temperature proposed as 255-291 rpm and 530-590°C, respectively. The established models of ANN introduced to genetic algorithm (GA) for determination of the optimal condition. The results were evaluated using the confirmation experiments. Moreover, the optimal condition of nanostructures alloy preparation with the highest micro hardness had been proposed as 310 Hv with the root mean square error (RMSE) of lower than 3.4%.
    Keywords: Artificial neural network, Genetic algorithm, Cu-Cr-Zr nanocomposite, Micro hardness optimization
  • Zahra Noroozi, Masoud Rajabi, Behrooz Bostani Pages 193-200
    In this study, functionally graded Ni-Al2O3 composite coating (FGN-A) has been produced from nickel Watt’s bath containing different concentrations of Al2O3 particles. For this, different composite coatings were electroplated in the same bath with different particles concentration to find the optimum concentration of particles in which the maximum content with uniform distribution of Al2O3 particles in the coating can be achieved. So, Al2O3 concentration was continuously increased in the electroplating bath. The composite coatings were characterized by SEM and EDS. Structure and phase composition were identified by XRD analysis. Microhardness of the coatings was evaluated employing Vickers Instrument. Three-point bend test was carried out to compare the adhesion strength of the coatings and dry sliding wear tests were performed using a pin-on-disk wear apparatus. Study on the resulting sample shows that FGN-A by Al2O3 gradient distribution in cross-section is coated successfully. By increasing Al2O3 particles content in Ni matrix, microhardness grows from interface toward the surface of the coating. The result of bending test show that the functionally graded composite coating shows excellent adhesion to substrate compared with the uniformly distributed Ni-Al2O3 (UN-A) on the same substrate. This has been attributed to lower mechanical mismatch between coating and substrate in functionally graded composite coating compared with uniformly distributed one. The results of wear resistance measurements test revealed that wear resistances of functionally graded Ni-Al2O3 is higher than that of ordinary distributed composite coating
    Keywords: functionally composite coating, co-electrodeposition, microhardness, adhesion, wear resistance