فهرست مطالب

Ultrafine Grained and Nanostructured Materials - Volume:49 Issue: 2, Dec 2016

Journal of Ultrafine Grained and Nanostructured Materials
Volume:49 Issue: 2, Dec 2016

  • تاریخ انتشار: 1395/10/10
  • تعداد عناوین: 10
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  • Soha Mohajeri *, Abolghassem Dolati, Mohammad Ghorbani Pages 51-63
    In this research, a sol-modified composite electrodeposition technique that combines the sol-gel method with the conventional electrodeposition process was utilized to deposit Ni-TiO2 nanocomposite coatings. Cyclic voltammetry and chronoamperometry techniques were applied to study the influence of the TiO2 sol concentration on the deposits’ electrochemical behavior. The results clearly showed that for higher sol concentrations, the onset potential of the nanocomposite deposition decreased compared to that of the pure Ni. The Scharifker-Hill model was utilized at the initial times of deposition to study the nucleation mechanism. It was demonstrated that the nucleation mechanism of the nanocomposite at low overpotentials followed the progressive system, whereas at higher overpotentials it was found to be instantaneous with the three-dimensional growth mechanism. The weight percentages of the codeposited TiO2 nanoparticles were measured, and according to the results, the higher sol concentrations in the plating bath led to a higher TiO2 nanoparticle content. The XRD results confirmed the presence of the anatase phase in the Ni-TiO2 nanocomposite coatings after 3 hours of heat treatment at 450°C. The surface morphology was studied by the scanning electron microscopy, confirming that the addition of higher sol concentrations refined the microstructure, particularly under higher deposition overpotentials. This was attributed to increased nucleation sites and the slow growth rate of the nuclei.
    Keywords: Electrodeposition, Ni, TiO2, Nanocomposite, Mechanism
  • Mansoor Anbia *, Mohammad Javad Habibi, Mojgan Haghsenas, Majideh Babaei Pages 64-71
    In this study, a novel solid dendrimer amine (hyperbranched polymers) was prepared using mesoporous carbon nitride functionalized by melamine based dendrimer amines. This adsorbent was denoted MDA-MCN-1. The process was stepwise synthesis and hard-templating method using mesoporous silica SBA-15 as a template. Cyanuric chloride and N,N-diisopropylethylamine (DIPEA, Merck) were used for functionalization of the MCN-1. Fourier transform infrared spectroscopy (FT-IR), Nitrogen adsorption-desorption analysis, Small Angle X-ray Scattering (SAXS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used for characterization of the adsorbent. This material was used for carbon dioxide gas (CO2) and methane gas (CH4) adsorption at high pressure (up to 20 bar) and room temperature. The volumetric method was used for the tests of the gas adsorption. The CO2 adsorption capacity of modified mesoporous carbon nitrides was about 4 mmol CO2 per g adsorbent. The methane adsorption capacity of this material was less than that CO2. Modified Mesoporous Carbon Nitride adsorbed about 3.52 mmol CH4 /g adsorbent. The increment of melamine based dendrimer generation on mesoporous surface increased adsorption capacity of both carbon dioxide and methane gases. According to the results obtained, the solid dendrimer amines, (MDA-MCN-1), performs excellently for CO2 and CH4 capture from flow gases and CO2 and CH4 storage.
    Keywords: Carbon dioxide, Methane, Adsorption, Mesoporous carbon nitride, Melamine
  • Mohsen Hosseinzadeh, Seyyed Ali Seyyed Ebrahimi *, Shahram Raygan, Seyed Morteza Masoudpanah Pages 72-79
    In this study, the removal of cadmium and lead ions from aqueous solution by nanocrystalline magnetite was investigated. The nanocrystalline magnetite was synthesized by mechanochemical activation of hematite in a high energy planetary mill in argon atmosphere for 45 hours. The ability of the synthesized nanocrystalline magnetite for removal of Cd(II) and Pb(II) from aqueous solutions was studied in a batch reactor under different experimental conditions with different pHs, contact times, initial metal ion concentrations and temperatures. The solution’s pH was found to be a key factor in the adsorption of heavy metal ions on Fe3O4. The optimum pH of the solution for adsorption of Cd(II) and Pb(II) from aqueous solutions was found to be 6.5 and 5.5, respectively. The best models to describe the kinetics and isotherms of single adsorption were both the pseudo first and second-order kinetic models and Langmuir models, respectively, indicating the monolayer chemisorption of Cd(II) and Pb(II) on Fe3O4 nanoparticles. Moreover, the thermodynamic parameters (i.e., ∆H°, ∆S°, ∆G°) were evaluated which indicated that the adsorption was spontaneous and exothermic. The results suggested that the synthesized material (magnetite nanocrystalline particles) may be used as effective and economic absorbent for removal of Cd(II) and Pb(II) from aqueous solutions.
    Keywords: Cadmium ions, Lead ions, Magnetite, Adsorption
  • Mustafa Aghazadeh* Pages 80-86
    Gd2O3 nanoparticles were prepared by a two–step process; cathodic electrodeposition followed by heat-treatment method. First, Gd(OH)3 nanoparticles was galvanostatically deposited from nitrate bath on the steel substrate by pulse current (PC) mode. The deposition experiments was conducted at a typical on-time and off-time (ton=1ms and toff=1ms) for 60 min. The electrodeposited precursor was then heat-treated at 600 oC for 3h to obtain oxide product (i.e. Gd2O3). The morphological and structural analyses confirmed that the gadolinium hydroxynitrate nanoparticles with composition of [Gd(OH)2.5(NO3)0.5 yH2O] and uniform size about 10 nm have been prepared during pulse cathodic electrodeposition process. Furthermore, mechanism of the gadolinium hydroxynitrate nanoparticles was explained based on the base (OH–) electrogeneration process on the cathode surface. The morphological observations by SEM and TEM, and structural analyses via XRD and FT-IR revealed that the oxide product is composed of well-dispersed Gd2O3 nanoparticles with pure cubic crystalline structure. It was observed that the calcination process has no effect on the morphology of the Gd2O3 nanoparticles. Mechanism of oxide formation during heat-treatment step was investigated by DSC-TG analysis and discussed in detail. The results of this work showed that pulse current deposition followed by heat–treatment can be recognized as an easy and facile method for preparation of the Gd2O3 fine nanoparticles.
    Keywords: Gd2O3, Nanoparticles, Pulse electrodeposition, Heat treatment
  • Ibrahim Sharifi, Ali Zamanian*, Aliasghar Behnamghader Pages 87-91
    Magnetic nanoparticles attracted a great deal of attention in the medical applications due to their unique properties. The most exceptional property of magnetic particles is their response to a magnetic force, and this property has been utilized in applications such as drug targeting, bioseparation, contrast agents in magnetic resonance imaging (MRI) and heating mediators for cancer therapy. In this study, a ternary system of Co0.4Zn0.6Fe2O4 was synthesized by thermal decomposition method using metal acetylacetonate in high temperature boiling point solvent and fatty acids. Unlike other synthesis techniques this method can be get nearly monodispersed nanoparticles that makes them suitable for medical applications like hyperthermia. X-ray diffraction study was used to determine phase purity, crystal structure, and average crystallite size of cobalt-zinc ferrite nanoparticles. The average diameter of particles was determined by field emission scanning electron microscope (FESEM) around 16 nm. Fourier transform infrared (FT-IR) measurement confirmed mono phase spinel structure of ferrite. The as-prepared ferrite nanoparticles were characterized extensively by other analytic techniques like vibrating sample magnetometer (VSM) to achieve magnetic properties of nanoparticles. Room temperature magnetization measurements showed the magnetization Ms and coercivity of magnetic nanoparticles as high as 74 emu/g and 114 Oe, which can be a good candidate for use in hyperthermia applications.
    Keywords: Ferrite nano particles, Thermal decomposition, Cobalt, Zinc, Rietveld refinement method
  • Maryam Azadeh, Cyrus Zamani *, Abolghasem Ataie Pages 92-96
    Silica exists in Rice husk, an agriculture waste, as a naturally occurring phase. In first step, acidic pre-treatment and calcination of the rice husk were performed to obtain nano-silica, in which various sizes of the nano-silica, totally with sizes under 80 nm, were achieved. Second, to reduce nano-silica to elemental Si and subsequently formation of the composite, Mg used as the reducing agent. In this work, the as-obtained composite mainly is the product of magnesiothermic reduction reaction of the nano-silica, which finally resulted in formation of elemental Si (silicon), MgO (magnesia) and Mg2SiO4 (magnesium silicate). The as-synthesized composite can be used as anode in lithium ion batteries. The products in each step were characterized using X-ray powder diffraction (XRD) and scanning electron microscopy (FESEM and HRSEM) techniques. X-ray powder diffraction patterns confirmed the formation of almost amorphous silica while the FE-SEM images were representing the spherical silica particles at various calcination temperatures. After the magnesiothermic reduction process, HRSEM micrographs indicated the formation of Si-MgO-Mg2SiO4 composite with particle sizes of 180-300 nm. The phase composition analysis was calculated by Rietveld method The electrical response of the Si/MgO/Mg2SiO4 composite was measured to be of 6×108 Ω.m resulted from I-V measurement.
    Keywords: Nano, silica, Silicon, Rice husk, Magnesiothermic reduction, Composite
  • Reza Ansari *, Shahram Ajori, Sina Malakpour Pages 97-102
    Importance of covalent bonded two-dimensional monolayer nanostructures and also hydrocarbons is undeniably responsible for creation of new fascinating materials like polyphenylene polymer, a hydrocarbon super honeycomb network, so-called porous graphene. The mechanical properties of porous graphene such as its Young’s modulus, Poisson’s ratio and the bulk modulus as the determinative properties are calculated in this paper using ab initio calculations. To accomplish this aim, the density functional theory on the basis of generalized gradient approximation and the Perdew–Burke–Ernzerhof exchange correlation is employed. Density functional theory calculations are used to calculate strain energy of porous graphene with respect to applied strain. Selected numerical results are then presented to study the properties of porous graphene. Comparisons are made between the properties of porous graphene and those of other analogous nanostructures. The results demonstrated lower stiffness of porous graphene than those of graphene and graphyne, and higher stiffness than that of graphdyine and other graphyne families. Unlikely, Poisson’s ratio is observed to be more than that of graphene and also less than that of graphyne. It is further observed that the presence of porosity and also formation of C-H bond in the pore sites is responsible for these discrepancies. Porous graphene is found to behave as the isotropic material.
    Keywords: Porous graphene, Nanostructure, Elastic properties, Density functional theory
  • Moluk Aivazi *, Mohammadhossein Fathi, Farahnaz Nejatidanesh, Vajihesadat Mortazavi, Batoul Hashemibeni Pages 103-111
    Ceramic dental materials have been considered as alternatives to metals for dental implants application. In this respect, zirconia tetragonal stabilized with %3 yttrium, is of great importance among the ceramic materials for endosseous dental implant application. Because of its good mechanical properties and color similar to tooth. The aim and novelty of this study was to design and prepare Y-TZP nano-composite to reduce the degradation process at low temperature by alumina addition and maintaining submicron grain sized. Also, flexural strength of nano-composite samples was evaluated. Toward this purpose, alumina-Y-TZP nano-composites containing 0–30 vol% alumina (denoted as A-Y-TZP 0-30) were fabricated using α-alumina and Y-TZP nano-sized by sintering pressure less method. The synthesized samples were characterized using x-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive x-ray spectroscopy techniques. Nano-composite samples with high density (≥96%) and grain sized of ≤ 400 nm was obtained by sintering at 1270 °C for 170 min. After low temperature degradation test (LTD), A-Y-TZP20 and A-Y-TZP30 not showed monoclinic phase and the flexural strength in all of samples were higher than A-Y-TZP0. It was concluded that the grains were remained in submicron sized and A-Y-TZP20 and A-Y-TZP30 did not present biaxial strength reduction after LTD test.
    Keywords: Alumina, zirconia nanocomposite, Low temperature degradation process, Endosseous dental implant, Y, TZP matrix
  • Lima Amiri Talischi, Ahad Samadi * Pages 112-119
    The synthesis of nanocrystalline Fe3Al powder by mechanical alloying as well as the structural ordering of the synthesized Fe3Al particles during the subsequent thermal analysis were investigated. Mechanical alloying was performed up to 100 hours using a planetary ball mill apparatus with rotational speed of 300 rpm under argon atmosphere at ambient temperature. The synthesized powders were characterized using X-ray diffraction, SEM observations and differential scanning calorimetry (DSC). The results show that the A2-type Fe3Al with disordered bcc structure is only formed after 70 hours milling. The corresponding lattice strain, mean crystallite and particle sizes for the 70 hours milled Fe3Al powder were determined as 2.5%, 10 and 500 nm, respectively. The subsequent heating during DSC causes a DO3-type Fe3Al ordering in 70 and 100 hours milled powders, however in 40 hours milled powder it only assists for the formation of disordered solid solution. Longer milling time induces a large amount of lattice strain in Fe3Al powder particles and consequently facilitates the atomic diffusion thus decreases the activation energy of ordering. The activation energy for ordering transformation of 100 hours Fe3Al milled powder was calculated as 152.1 kJ/mole which is about 4 kJ/mole lower than that for 70 hours milled powder.
    Keywords: Fe3Al intermetallic compound, Mechanical alloying, Nanocrystalline powder, X-ray diffraction, Ordering
  • Reihane Nafar Dehsorkhi *, Soheil Sabooni, Abdoulmajid Eslami, Fathallah Karimzadeh, Behzad Sadeghian Pages 120-127
    In the present study, an ultrafine grained (UFG) 304L stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing. Weldability of the UFG sample was studied by Nd: YAG laser welding under different welding conditions. Taguchi experimental design was used to optimize the effect of frequency, welding time, laser current and laser pulse duration on the resultant microstructure and mechanical properties. X-ray Diffraction (XRD), Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), microhardness measurements and tension tests were conducted to characterize the sample after thermomechanical processing and laser welding. The results showed that the ultrafine grained steel had the yield strength of 1000 Mpa and the total elongation of 48%, which were almost three times higher than those of the as-received sample. The microstructure of the weld zone was shown to be a mixture of austenite and delta ferrite. The microhardness of the optimized welded sample (315 HV0.5) was found to be close to the UFG base metal (350 HV). It was also observed that the hardness of the heat affected zone (HAZ) was lower than that of the weld zone, which was related to the HAZ grain growth during laser welding. The results of optimization also showed that the welding time was the most important parameter affecting the weld strength. Overall, the study showed that laser welding could be an appropriate and alternative welding technique for the joining of UFG steels.
    Keywords: 304 stainless steel, Ultrafine grain, Laser welding, Taguchi experimental design