فهرست مطالب

  • Volume:52 Issue:1, 2019
  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 13
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  • Mir Saman Safavi, Mohamadreza Etminanfar * Pages 1-17

    Surface treatments of the biomaterials are of great interest in many biomedical applications. Hydroxyapatite is a favorable candidate for surface modification of the implants. To date, a wide variety of methods have been developed to produce bio-active/biocompatible coatings with desirable features in order to improve the performance of the implants. This paper strives to overview the present prevalent methods for synthesizing the hydroxyapatite based multilayer coatings as well as the various properties of such coatings. The common methods for fabrication of HAp-containing multilayer coatings including electrochemical, sol-gel, and plasma spray routs. It was clearly highlighted that the main drawback in pure HAp coatings is their poor adhesion to the implants. The studies in the field of HAp-ceramic systems showed that the deposited ceramic layers, e.g. TiO2 and ZrO2, are strongly adherent to HAp and substrate which leads to a remarkable improvement in the mechanical properties of pure HAp coatings. Unlike HAp-ceramic systems, there are less studies dealt with the HAp-polymeric systems. The performed studies demonstrated that the corrosion resistance and adhesion strength of the coatings to the substrates can be considerably improved with the deposition of HAp/polymer multilayer coatings. Altogether, HAp based multilayer coatings have bright prospect since they benefit from HAp biocompatibility as well as the enhanced adhesion to the substrate.

    Keywords: Hydroxyapatite, Nanostructured Multilayers, Mechanical Properties, Corrosion Resistance, Implants, Biomedical Applications
  • Seyed Mahmood Fatemi * Pages 18-24

    An ultrafine/nano grained AZ31 magnesium alloy was produced through four-pass ECAP processing. TEM microscopy indicated that recrystallized regions included nano grains of 75 nm. Pole figures showed that a fiber basal texture with two-pole peaks was developed after four passes, where a basal pole peak lies parallel to the extrusion direction (ED) and the other ~20° away from the transverse direction (TD) in the ED–TD plane and 70° from the normal direction (ND ) in the TD–ND plane. The texture of recrystallized grains at the vicinity of grain boundaries was addressed. To investigate the recrystallization texture, the orientation relationships for the recrystallized and parent grains were studied for the material deformed up to first and second passes. The EBSD results implied that the grains recrystallized at the grain boundaries during the first pass, almost follow the orientation of prior deformed grains, while during the second pass the grain boundary recrystallization adopted a texture different from the parent grains. It was rationalized that as the number of passes increased, the grains recrystallized at prior grain boundaries tend to take different orientation to that of deformed grains. The latter finding was discussed relying on the increased share of non-basal slips in evolution of finer grains developed during subsequent deformation passes.

    Keywords: Nonograins, Recrystallization, Texture, Magnesium
  • Farshad Samadpour, Armin Siahsarani, Ghader Faraji *, Mostafa Bahrami Pages 25-31

    It is generally known that severe plastic deformation processes with back pressure not only apply higher hydrostatic stress and more deformation compared to what a regular process can apply to a workpiece but also prevent surface defects in the workpiece during the process. Hydrostatic cyclic expansion extrusion (HCEE) was developed recently for processing long ultrafine-grained metals and alloys. This process applies relatively higher hydrostatic pressure and prevents the formation of defects at the same time dramatically decreases the process load by eliminating the friction. However, increasing the compressive hydrostatic pressure leads to enhance the mechanical properties by minimizing the initiation and propagation of defects. So, back pressure may be considered as a solution. In this paper, first, morphological investigation of HCEE processed aluminum without back pressure is conducted. Second, the plastic deformation behavior of the aluminum sample during this recently introduced process for producing longer samples with different external back pressures is investigated using the finite element method. The homogeneity within the workpiece was analyzed in terms of contours, path plot, and statistics of strain distribution under different conditions regarding back pressure. The simulation results shed some lights on the optimum design of HCEE for homogeneous and large severe plastic deformation.

    Keywords: Severe Plastic Deformation, Hydrostatic Cyclic Expansion-Extrusion, Finite element, Grain refinement
  • Alireza Rezvani, Ramin Ebrahimi * Pages 32-42

    Circular simple shear extrusion process was introduced as a new geometry for simple shear extrusion technique to fabricate ultrafine-grained materials. Similar to the simple shear extrusion method, this process is also based on direct extrusion, and the samples deform in a simple shear manner. In this investigation, the simulations were carried out using the commercial finite element code ABAQUS/Explicit and the process was performed experimentally on commercially pure aluminum (AA1050) samples. Besides, the optimized length of the deformation channel was measured, 26 mm using the commercial simulation package DEFORM 3D. The effects of back-pressure and processing routes on deformation behavior and hardness homogeneity were studied in the simulation and experiment. Uniaxial compression test, X-ray diffraction, and Vickers microhardness test were performed on the samples to determine the mechanical and microstructural properties. The experimental results were in good agreement with the ones obtained by simulation. It was found that in the practical approach with the absence of back-pressure, route D had the most homogeneous distribution of strain in the cross-section and throughout the length of the samples. The results of compression and microhardness tests showed that the mechanical properties of the samples were improved compared to the annealing state. Also, a significant reduction in crystallite size can be seen in the XRD results leading to an average crystallite size of 103 nm after 10 passes.

    Keywords: Circular Simple Shear Extrusion, Severe Plastic Deformation, Finite Element Analysis, Mechanical Properties
  • Touraj Abedi, Shahin Khameneh Asl *, Mohammadreza Etminanfar Pages 43-56

    Synthesis of functionally gradient coating was the main goal of researches to cover some deficiencies of metallic coatings. In this study, a new strategy for generating functionally gradient coatings of nickel-chromium on a carbon steel substrate using pulse electrodeposition has been presented. The gradual changes of the duty cycle and pulse frequency were used to generate the functionally gradient coating, and the chemical composition, microstructure, microhardness, wear and corrosion of them were investigated. Gradual changes of the duty cycle from 45 to 80% led to a gradient structure with a chromium content of 83% on the surface and 3% in the vicinity of the interface. Frequency changes had no significant effect on the chemical composition and did not result in the production of gradient coatings. In both groups, wear resistance improved related to the monolayer one so that weight loss in former group is reduced about 33-62% and in later group decreased almost 13-30%. Also, the corrosion current density in the samples deposited by gradual change of duty cycle was approximately 0.01-0.04 times of that for monolayer coatings. The microhardness value in the top layers of FGD coating was in the range of 650-800 HV 0.01 which reduced gradually towards the substrate. The high Cr content in the top layers is the reason for high hardness and good corrosion resistance.

    Keywords: Electrodeposition, Functionally graded coating, Duty cycle, Frequency
  • Leila Fathyunes *, Jafar Khalil, Allafi, Fatemeh Marashi, Najafi Pages 57-68

    In this study, calcium-phosphate (Ca-P) and graphene oxide (GO)/ calcium-phosphate (Ca-P) coatings were electrodeposited with different pulsed current densities on TiO2 nanotubes. Results showed that the co-electrodeposition rate in the presence of GO, especially at low current densities of 2 and 5 mA/cm2, significantly decreased. This might be due to the large size of GO sheets as compared to the size of calcium and phosphate ions. The SEM micrographs revealed that the surface of the anodized titanium could not be completely covered with the GO/Ca-P coatings applied at such low current densities. However, producing a considerable amount of H2 gases at higher current densities of 10 and 15 mA/cm2 caused the formation of a coating with poor quality. Regarding this, increasing the off part of the pulsed current by changing duty cycle from 0.3 to 0.1 led to the co-electrodeposition of GO/Ca-P coating with an acceptable quality. The FTIR and micro-Raman analyses also demonstrated that the current density of 15 mA/cm2 was more favorable to apply the coating predominantly consisting of hydroxyapatite (HA) phase. At last, studying the ability of apatite mineralization in simulated body fluid (SBF) displayed that both Ca-P and GO/Ca-P coatings electrodeposited at the current density of 15 mA/cm2 and duty cycle of 0.1 are acceptable for biomedical applications.

    Keywords: Calcium Phosphate, Graphene Oxide, coating, Pulsed current densities, Co-electrodeposition, Biocompatibility
  • Saba Fayazzadeh, Mehdi Khodaei * Pages 69-77

    Current study represents the effect of the size and synthesis method on the cation distribution of cobalt ferrite nanoparticles and on the magnetic properties. The nanoferrites have been synthesized through sol-gel auto-combustion method using metal nitrates as precursor and citrate as fuel. In order to obtain the fine and agglomerated-free particles, we have used salt-assisted combustion reaction method. Magnetic properties of the synthesized single phase cobalt ferrite nanoparticles are carried out using vibrating sample magnetometer (VSM) at room temperature. It has been observed that the coercivity and saturation magnetization of the samples reduced by adding salt. The transmission electron microscopy (TEM) confirms the finer nanoparticles formation from around 70-200 nm to 10-40 nm. Structural characterization is done by X-ray diffraction (XRD) and it confirms the spinel structure formation for the samples. The crystallite size and induced strain were derived from the XRD patterns by Williamson-Hall (W-H) method. The magnetic parameters were reduced by crystallite size reduction from 38.5 nm to 11 nm. The further analysis of XRD peaks is fulfilled using Rietveld refinement in order to explain the magnetic properties. The obtained Rietveld refined data allow us to measure the distribution of cations within the available octahedral and tetrahedral sites.

    Keywords: Sol-gel auto-combustion, Magnetic properties, Cobalt ferrite, W-H analysis, Cation distribution, Rietveld refining
  • Seyed Mahmoud Hosseini, Alireza Mashayekhi, Seyed Ali Safiabadi Tali, Zeinab Sanaee * Pages 78-83

    Lithium ion batteries are among the most used rechargeable batteries in the world. Carbon nanostructures including carbon nanotubes (CNTs) are considered as important electrode materials for this kind of batteries. Therefore improving the performance of these carbon based electrodes in Lithium ion batteries is an important issue and attracts much attention in the battery community. In this manuscript, a new method for high content Nitrogen doping on CNTs is reported as an efficient approach for enhancing the battery performance. Direct current-plasma enhanced chemical vapor deposition (DC-PECVD) system was used for nitrogen doping. Annealing with Nitrogen during CNT growth and plasma exposure after the growth has been used for Nitrogen doping of the CNTs. The growth was performed on an Indium Tin oxide (ITO) covered Silicon substrate. Implementation of Silicon substrate enables the possibility of future integration of other electronic circuits with the fabricated Lithium ion battery. Vertically aligned CNTs with an average diameter of around 150 nm and 4 um height has been obtained on this substrate. The synthesized CNTs was subsequently used as the electrode of Lithium ion battery in a half cell configuration. The results show a significant improvement of about 400% in the specific capacity of the battery as a result of Nitrogen doping. For Nitrogen doped CNT based battery, specific capacity of around 0.4 mAh/cm2 and coulombic efficiency of 97% were achieved after 28 cycles of charge/discharge with C rate of 2.5. This Nitrogen doping method is propped as an efficient technique for enhancing the performance of Lithium ion batteries with carbon based electrodes.

    Keywords: Nitrogen doping, CNT, Li ion battery, Capacity, Anode electrode
  • Manoochehr Sobhani *, Hossein Tavakoli Pages 84-89

    In the present study, the gamma alumina (γ-Al2O3) nano powders have been prepared with addition of 1%mol Co using an aqueous sol-gel method at lower temperature than the pure gamma alumina. The synthesis process accomplished by partial hydrolysis of the aqueous solution of metallic ions Al3+ and Co2+, with ammonia. The Al(NO3)3.9H2O and Co(NO3)2.6H2O salts were used as cations sources. The obtained gel at 40 ˚C dried at 120°C and calcined at different temperatures. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET method of surface analysis were applied for powders characterization. The results indicated that the well crystallization of the gamma phase occurred at about 700°C for the Co doped samples while it was 900 °C for the pure sample. The specific surface area and particle sizes of the powders varied from 186 to 140 m2/g and 8 to 11 nm for pure and cobalt added γ-Al2O3, respectively. Both powders have the meso-porous structure according to the hysteresis loop of the adsorption/desorption curves of BET analysis. In addition, the TEM diffraction pattern of the gamma alumina at the presence of Co contains some bright diffracted points due to its higher degree of crystallinity in comparison with the pure powder.

    Keywords: Synthesis, Meso-porous, Aqueous Sol-gel, ?-Alumina
  • Mansoor Anbia *, Atieyeh Alsadate Mousavi, Mohammad Sepehrian Pages 90-97

    A Novel modified Analcime (Na16 (Al16Si32O96) •16H2O) zeolite with a new molar ratio have been successfully synthesized. In order to investigate the role of the template, Different samples were synthesized with and without Tetramethylammoniumhydroxide (TMAOH) template through hydrothermal method. Different synthesis times (24, 36 and 72 hours) and molar ratios have been utilized. The optimum sample with highest Crystallinity (95.2%) has been used as seed for synthesis of analcime membrane on α-alumina support via Seed-assisted crystallization method. The resultant analcime membranes were then modified by Cu+2 and Ni+2 by ion exchange method. Synthesis of these materials is confirmed by the XRD, EDX and SEM methods. The SEM results of modified membranes showed that the surface of the support is shielded with a continuous layer of Ni+2 and Cu+2 crystals and the analcime zeolite are not destructed. Also, the results of XRD patterns verified that the main diffraction peaks of synthesized zeolites are similar to the analcime zeolite component and ion exchange reactions have not disturbed the structure of zeolite. Furthermore, the purity of analcime zeolites and its orthorhombic structure has been established. It should be mentioned that the modified membrane can be merged as a potential material for many applications such as gas separation.

    Keywords: Analcime Zeolite Membrane, ?-alumina Support, Ion Exchange, Modification, Orthorhombic Structure
  • Shafagh Mokhtarzadeh *, Farahman Hakimpour, Samira Agbolaghi, Yaghoub Mansourpanah Pages 98-109

    The novel nanocomposite membranes were successfully prepared by the incorporation of different concentrations (5, 10, and 15 wt%) of montmorillonite (MMT) as a nanoadditive into a blend of chitosan/polystyrene (CS/PS) at a ratio of 3:1 on the basis of solution-casting method and they were subsequently used for the separation of phenol, p-chlorophenol, and 2,4-dichlorophenol from water through pervaporation process. The effects of feed composition, the MMT content, and various feed types were investigated on pervaporation performance. All the membranes were water selective and the permeation rate increased with increasing the MMT content. The presence of MMT, increased the hydrophilicity of CS/PS blend polymer matrix, resulting in the formation of a higher flux to water molecules. The best separation performance was achieved for the CS/PSMMT-15 nanocomposite membrane containing a 15 wt % of MMT with 2,4-dichlorophenol in the feed, i.e., the 2,4-dichlorophenol concentration from 0.1 to 0.4 wt %, the flux values from 10.7 to 14.2 g/m2.h and the separation factor from 1784 to 721. The separation of 2,4-dichlorophenol/water mixture proceeded easier than that of the phenol/water and p-chlorophenol/water mixtures because of the larger molecular size of 2,4-dichlorophenol and the relatively weak coupling phenomenon with the water molecules and hydrophilic membranes.

    Keywords: Pervaporation, phenol, chlorophenols, chitosan, nanocomposite membrane, montmorillonite
  • Gholam Reza Khayati *, Farkhonde Ghanbari Rad Pages 110-121

    Hydroxyapatite (HA) is one of the most common biocompatible ceramic with wide usages in various aspects of medicine due to the resemblance to the mineral bone tissue. The particle size of HA has a key roll in determination of the reaction rate at the interface of natural bones/artificial. Accordingly, this paper tries to propose a novel approach for the preparation of HA nanoparticles from natural source as raw materials using microwave irradiation without any further heat treatment. To compare the proposed approach various combination of micro irradiation and heat treatment as traditional and more recent developments were performed. Characterizations of products were carried out using XRD, SEM and TEM techniques. The results confirmed the presence of minor constituents (Mg, Sr, C, O) and the ratio of Ca/Mg=1.63 in the products. Moreover, the formation of relatively spherical shape like nanoparticles of hydroxyapatite (about 30 nm) was confirmed by TEM images during the direct preparation of HA nanoparticles by employment of microwave irradiation. According to the results, the proposed approach provide the possibility of the preparation of large-scale, spherical and pure HA nanoparticles in acceptable time by usage of low cost natural source, eco-friendly method without the using of organic solvent and expensive raw materials.

    Keywords: Microwave, Hydroxyapatite Nanoparticles, Natural bones, Heat treatment
  • Pejman Monazzam, Azadeh Ebrahimian Pirbazari *, Behnam Fakhari, Ziba Khodaee Pages 122-132

    In this work, we focused on improvement of rutile-type TiO2 degradation efficiency by cobalt doping and decorating on carbon nanotubes walls (CNTs) (Co-TiO2/CNTs). We also synthesized pure TiO2, Co-TiO2 and TiO2/CNTs samples for control experiments. The textural and morphology features of the samples were characterized by a range of analyses including: XRD, FESEM/EDX. FTIR, TEM, UV-Vis DRS and N2 physisorption. The XRD results indicated that we obtained rutile phase as the major phase for TiO2 with crystal size between 18-22 nm. The band gap energy of the samples calculated from DRS analysis and Kubelka-Munk spectra and obtained 2.88, 2.38, 2.97 and 2.20 eV for TiO2, Co-TiO2, TiO2/CNTs and Co-TiO2/CNTs respectively. The effectiveness of the samples was examined through degradation of 2,4-dichlorophenol (2,4-DCP) as a model of organic pollutants in the synthetic wastewater under visible light. We achieved 27% and 50% visible light degradation of 2,4-DCP in the presence of pure TiO2 and Co-TiO2/CNTs after 180 min irradiation, respectively. The high visible light activity of Co-TiO2/CNTs sample could be approved that the presence of cobalt and CNTs reduced the band gap energy and sensitize TiO2 surface to visible light. The mechanism for degradation of 2,4-DCP by Co-TiO2/CNTs photocatalyst under visible light was proposed.

    Keywords: Cobalt, CNTs, Rutile, TiO2, Visible light degradation, 2, 4-dichlorophenol