@article { author = {Mobedpour, Bahareh and Roumina, Reza and Rajabdoust, Sina}, title = {Atomic Insights into the Melting Behavior of Metallic Nano-catalysts}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {81-89}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/jufgnsm.2017.02.01}, abstract = {In the present study, molecular dynamics simulations have been utilized to provide fundamental understanding of melting behavior of pure Pd and Pt nanoparticles with the size of 10 nm in diameter, both free and graphene-supported during continuous heating. The embedded atom method is employed to model the metal-metal interactions, whereas a Lennard-Jones potential is applied to describe the metal-carbon interactions. In addition, interactions between carbon atoms are defined by the adaptive intermolecular reactive bond order potential. Heating curves calculated between 298 K-2000 K are used to determine solid-liquid transitions. Based on simulation results, three approaches are used to investigate the thermal behavior of Pd and Pt nanoparticles. These include potential energy variation, the percentage of FCC atoms as a function of temperature and the mean square displacement method. Melting temperature of nanoparticles is found to decrease when the particles are supported by the graphene substrate. The decrease in melting temperature of particles is ascribed to the interaction of carbon atoms with nanoparticles. Structural changes during melting of nanoparticles are also detected through the common neighbor analysis and the mean square displacement method. The analyses of crystal structure shows that the supported nanoparticles melt from surface. In addition, a sharp increase in the mean square displacement of supported nanoparticles is observed after melting which is suggested to be responsible for the reduction of melting point of nanoparticles.}, keywords = {Molecular Dynamics,Platinum Nanoparticles,Palladium Nanoparticles,graphene}, url = {https://jufgnsm.ut.ac.ir/article_64240.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64240_c985059e3d2e5bceec7cc5e53af54c2b.pdf} } @article { author = {Torabi, Mohsen and Eivani, Ali Reza and Jafarian, Hamidreza and Salehi, Mohammad Taghi}, title = {Re-strengthening in AA6063 Alloy During Equal Channel Angular Pressing}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {90-97}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/jufgnsm.2017.02.02}, abstract = {Equal channel angular pressing (ECAP) is carried out using two different configurations for the exit channel of the ECAP die, i.e., relieved and choked, with angles of 0.2 °. It is found that using a die with relieved exit channel, the sample was extruded for 6 passes with no surface cracks and an average cell size of 727 nm and a fraction of high angle grain boundaries of 54 % were achieved. Measured values of yield strength (YS) and ultimate tensile strength (UTS) were reported to be 201.1 and 259.5, respectively. By using the die with choked exit channel, it was possible to deform the sample for up to 14 passes with no sign of surface cracking. A relatively finer cell structure around 530 nm was achieved and the fraction of HAGBs increased to 64 %. Relative increases in YS and UTS were as well observed indicating that re-strengthening has been activated in the material after saturation at the 4th pass. In addition, the mechanism of grain refinement seemed to change to progressive lattice rotation evidenced by formation of trapped single grains within the size range of less than 100 nm.  }, keywords = {Equal channel angular pressing,Die exit channel,Workability,Re-strengthening}, url = {https://jufgnsm.ut.ac.ir/article_64241.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64241_a359d3815d8ca1bf3df43a1b372650a9.pdf} } @article { author = {Etminanfar, Mohamadreza and Khalil-Allafi, Jafar and Jalili, Kiyumars}, title = {Synthesis and Characterization of Nano-Hydroxyapatite/mPEG-b-PCL Composite Coating on Nitinol Alloy}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {98-104}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/JUFGNSM.2017.02.03}, abstract = {In this study the bioactivity of hydroxyapatite/poly(ε-caprolactone)–poly(ethylene glycol) bilayer coatings on Nitinol superelastic alloy was investigated. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating. The surface morphology of coatings was studied using FE-SEM and SEM. The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized flakes and the polymer coating is uniformly covered the sublayer. Also, High resolution TEM studies on the hydroxyapatite samples revealed that each flake contains nano-crystalline grains with a diameter of about 15 nm. The hydroxyapatite monolayer coating was rapidly covered by calcium phosphate crystals (Ca/P=1.7) after immersion in simulated body fluid confirming the bioactivity of the nanostructured flakes. However, the flakes were weak against applied external forces because of their ultra-fine thickness. Scratch test was applied on hydroxyapatite/polymer coating to evaluate delamination of the coating from substrate. It was shown that, the polymer coating has a great influence on toughening the hydroxyapatite coating. To assess the degradation effect of the polymer layer on hydroxyapatite coating, samples were immersed in phosphate-buffered saline at 37 ᵒC. SEM studies on the samples revealed that the beneath layer of hydroxyapatite appears after 72 h without any visible change in morphology. It seems that, application of a biodegradable polymer film on the nanostructured hydroxyapatite coating is a good way to support the coating during implantation processes}, keywords = {Nitinol,HA film,Nano-sized,mPEG-b-PCL,biodegradable}, url = {https://jufgnsm.ut.ac.ir/article_64242.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64242_8131e393fb05310aa15c3e4c2123ec95.pdf} } @article { author = {Shahjuee, Tahereh and Masoudpanah, Seyyed Morteza and Mirkazemi, Seyed Mohammad}, title = {Coprecipitation Synthesis of CoFe2O4 Nanoparticles for Hyperthermia}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {105-110}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/JUFGNSM.2017.02.04}, abstract = {Cobalt ferrite (CoFe2 O4 ) nanoparticles have attracted significantly attentions for spintronics, recording media and bioapplications due to their unique magnetic and chemical properties. In this work, single phase CoFe2 O4 nanoparticles were synthesized at various coprecipitation temperatures (60, 80 and 90 °C) without post calcination. The effects of oleic acid as surfactant on the microstructure, magnetic properties and heating rate were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and vibrating sample magnetometry techniques. The small particle size and narrow size distribution were achieved using oleic acid. IR spectra showed the oleic acid molecules adsorbed on particle surface, leading to the lower growth rate and then the smaller nanoparticles. The CoFe2 O4 nanoparticles showed ferromagnetic behavior. The highest saturation magnetization of 45 emu/g and coercivity of 950 Oe were achieved at the coprecipitation temperature of 80 °C without using oleic acid. However, the saturation magnetization increased from 8 to 37 emu/g with the coprecipitation temperature due to the increase of crystallinity and particle size. The coprecipitated CoFe2 O4 nanoparticles at 80 °C exhibited the AC heating temperature of 7.5°C and specific loss power of 18.3 W/g under magnetic field of 100 Oe and frequency of 200 kHz. The heat generation mechanism was attributed to the hysteresis loss.}, keywords = {CoFe2O4,Coprecipitation, Magnetic properties, Hyperthermia}, url = {https://jufgnsm.ut.ac.ir/article_64243.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64243_3bac048e5ee93bbc4476b1fe9482ad38.pdf} } @article { author = {Gholamipour, Reza and Keyvanara, Amir and Shahri, Farzad and Mirdamadi, Shamsoddin}, title = {Effect of Joule-Heating Annealing on Giant Magnetoimpedance of Co64Fe4Ni2B19-xSi8Cr3Alx (x = 0, 1 and 2) Melt-Spun Ribbons}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {111-116}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/jufgnsm.2017.02.05}, abstract = {In this work, we have studied the influence of dc joule-heating thermal processing on the structure, magnetoimpedance (MI) and thermal properties of Co64Fe4Ni2B19-xSi8Cr3Alx (x = 0, 1, and 2) rapidly solidified melt-spun ribbons. The nanocrystallization process was carried out by the current annealing of as-spun samples at various current densities. As-spun and joule-heated samples were studied by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and magnetoimpedance (MI) measurements. DSC results revealed that by the replacement of B by Al the first and second crystallization peaks are overlapped with each other and the initial nanocrystallization temperature is decreased with the increase in Al content of the alloy. Also it was shown that the replacement of B by Al atoms can improve soft magnetic properties confirmed by magnetoimpedance ratio (MIR%) results for the amorphous joule-heated ribbons. Furthermore, increase in dc joule current density increases the MI ratio first, however; after formation of crystalline phases, it decreases. }, keywords = {Co-based alloy,Joule-heating annealing,giant magnetoimpedance,melt-spinning}, url = {https://jufgnsm.ut.ac.ir/article_64244.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64244_07be15f5d2fe0a8aaee4a9a6d3690af0.pdf} } @article { author = {Ahmadi, Masoud and Ansari, Reza and Darvizeh, Mansour and Rouhi, Hessam}, title = {Effects of Fluid Environment Properties on the Nonlinear Vibrations of AFM Piezoelectric Microcantilevers}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {117-123}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/jufgnsm.2017.02.06}, abstract = {Nowadays, atomic-force microscopy plays a significant role in nanoscience and nanotechnology, and is widely used for direct measurement at atomic scale and scanning the sample surfaces. In tapping mode, the microcantilever of atomic-force microscope is excited at resonance frequency. Therefore, it is important to study its resonance. Moreover, atomic-force microscopes can be operated in fluid environments such as their applications in chemical and biological sensors. Additionally, piezoelectric microcantilevers are used to enhance atomic-force microscope scanning. Motivated by these considerations, presented herein is a finite element investigation into the nonlinear vibration behavior of piezoelectric microcantilever of atomic-force microscopes in fluid environment. For this purpose, a 3D finite element model coupled with a computational fluid dynamics model is introduced based upon a fluid-solid interaction analysis. First, the reliability of present fluid-solid interaction analysis is revealed by comparison with experimental data available in the literature. Then, numerical results are presented to study the influences of fluid dynamic viscosity and density on the resonance frequency, resonance amplitude and time response of piezoelectric microcantilever. It was shown that increasing the fluid density and dynamic viscosity results in the decrease of resonance frequency. For example, for density equal to 1000 kg/m3 , increasing the viscosity of fluid environment from 0.1 to 1, 10 and 20 mPa.s leads to decrease of resonance frequency about 3%, 29% and 42%, respectively. Also, the resonance amplitude of microcantilever increases as the density increases, while increasing dynamic viscosity has a decreasing effect on the resonance amplitude.}, keywords = {Piezoelectric microcantilever,Atomic-force microscopy,Nonlinear vibration,Fluid-solid interaction analysis}, url = {https://jufgnsm.ut.ac.ir/article_64245.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64245_8cf8339b2715c0d4cd35d8a77ffb3468.pdf} } @article { author = {Ghorbanpour, Mohammad and Mazloumi, Maryam and Nouri, Afsaneh and lotfiman, Samaneh}, title = {Silver-Doped Nanoclay with Antibacterial Activity}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {124-131}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/JUFGNSM.2017.02.07}, abstract = {The aim of this study was to synthesize Ag-nanoclay composite by solid ion exchange, then characterize, and evaluate the antibacterial activity. This newly introduced ion exchange is a simple and low cost technique, which provides a quicker method. Without chemical treatment, nanoclay was subjected to an ion exchange process in media containing molten salt of silver at 300 and 400 °C and at different periods. Scanning electron microscopy showed that the flakes’ structure was opened by higher temperature and longer time. DRS graph revealed that Ag particles were successfully loaded, and that higher temperature and longer time increased the loading amount. Changes in basal reflection in XRD peak validated the presence of Ag. The Release test indicate that the materials do not present any risk for drinking water treatment since the leached metals were very small and in acceptable concentrations. The constant amount of release after four hours of sharp releasing. The antibacterial activity of the prepared composites was tested against gram-negative Escherichia coli and Staphylococcus aureus using the disc diffusion method. Presence of an inhibition zone clearly indicates the antibacterial effect of the composites. The results demonstrate that silver can be introduced onto nanoclay by single-step ion exchange.}, keywords = {Solid ion exchange,silver-doped nanoclay,Antibacterial activity,nanocomposite}, url = {https://jufgnsm.ut.ac.ir/article_64246.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64246_818761d9f3f868e40afa32b4923dce2c.pdf} } @article { author = {Pourbahari, Bita and Mirzadeh, Hamed and Emamy, Massoud}, title = {Grain Refinement and Enhancement of Mechanical Properties of Hot Extruded Rare-Earth Containing Magnesium Alloy}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {132-136}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/JUFGNSM.2017.02.08}, abstract = {The effects of rare earth addition and hot extrusion process on the grain refinement of magnesium alloy were studied. The as-cast Mg-6Al-1Zn (AZ61) alloy had the average grain size of ~ 64 µm and its microstructure consisted of α-Mg and Mg17Al12 phase. By partial substitution of Al with Gd to reach Mg-4.8Gd-1.2Al-1Zn alloy, it was observed that the Mg17Al12 phase disappeared and two new intermetallic phases, i.e. (Mg,Al)3Gd and Al2Gd, were identified. The extrusion process showed significant effects on the shape and size of intermetallics and grain size of the matrix. The grain size of the extruded Mg-6Al-1Zn alloy was refined from 64 µm to 13.4 µm as a result of recrystallization. Regarding the Mg-4.8Gd-1.2Al-1Zn alloy, the grain refinement was much more pronounced, where the extruded grain size has been refined from 698 µm to 2.4 µm (extruded at 385 °C) and 1.3 µm (extruded at 320 °C). This was related to the presence of fine and widely dispersed intermetallic phases. Tensile strength and total elongation of extruded alloys were much higher than their as-cast counterparts and the extruded Mg-6Zn-1Al alloy showed magnificent mechanical properties. The latter was related to the absence of intermetallic particles, which act as stress risers.}, keywords = {Magnesium alloys,Rare-earth addition,Microstructure,Tensile properties}, url = {https://jufgnsm.ut.ac.ir/article_64247.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64247_2ba0bb772b32b08ea3e810b2eddb84bc.pdf} } @article { author = {Agbolaghi, Samira and Zenoozi, Sahar and Abbaspoor, Saleheh and Nazari, Maryam}, title = {Scattering Study of Conductive-Dielectric Nano/Micro-Grained Single Crystals Based on Poly(ethylene glycol), Poly(3-hexyl thiophene) and Polyaniline}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {137-151}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/jufgnsm.2017.02.09}, abstract = {Two types of rod-coil block copolymers including poly(3-hexylthiophene)-block-poly(ethylene glycol) (P3HT-b-PEG) and PEG-block-polyaniline (PANI) were synthesized using Grignard metathesis polymerization, Suzuki coupling, and interfacial polymerization. Afterward, two types of single crystals were grown by self-seeding methodology to investigate the coily and rod blocks in grafted brushes and ordered crystalline configurations. The conductive P3HT fibrillar single crystals covered by the dielectric coily PEG oligomers were grown from toluene, xylene, and anisole, and characterized by atomic force microscopy (AFM) and grazing wide angle X-ray scattering (GIWAXS). Longer P3HT backbones resulted in folding, whereas shorter ones had a high tendency towards backbone lamination. The effective factors on folding of long P3HT backbones in the single crystal structures were the solvent quality and crystallization temperature. Better solvents due to decelerating the growth condition led to a higher number of foldings. Via increasing the crystallization temperature, the system decreased the folding number to maintain its stability. Poorer solvents also reflected a higher stacking in hexyl side chain and π-π stacking directions. The dielectric lamellar PEG single crystals sandwiched between the PANI nanorods were grown from amyl acetate, and analyzed using the interface distribution function (IDF) of SAXS and AFM. The molecular weights of PANI and PEG blocks and crystallization temperature were focused while studying the grown single crystals.}, keywords = {P3HT,PEG,PANI,single crystal,self-seeding,GIWAXS,SAXS}, url = {https://jufgnsm.ut.ac.ir/article_64248.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64248_9ba507a91f9e81b2270f976e5c96a86a.pdf} } @article { author = {Rezaei, Mohammad Reza and Toroghinezhad, Mohammadreza and Ashrafizadeh, Fakhreddin}, title = {Analysis of Strengthening Mechanisms in an Artificially Aged Ultrafine Grain 6061 Aluminum Alloy}, journal = {Journal of Ultrafine Grained and Nanostructured Materials}, volume = {50}, number = {2}, pages = {152-160}, year = {2017}, publisher = {University of Tehran}, issn = {2423-6845}, eissn = {2423-6837}, doi = {10.22059/JUFGNSM.2017.02.10}, abstract = {The current study adopted a quantitative approach to investigating the mechanical properties, and their relationship to the microstructural features, of precipitation-strengthened 6061 aluminum alloy processed through accumulative roll bonding (ARB) and aging heat treatment.  To serve this purpose, the contributions of different strengthening mechanisms including grain refinement, precipitation, dislocation and solid-solution strengthening to the yield strength of five-cycle ARB samples processed under pre-aged (ARBed) and aged (ARBed+Aged) conditions were examined and compared. Microstructural characterizations were performed on the samples through the transmission electron microscope (TEM) and X-ray diffraction (XRD). Also, the mechanical properties of the samples were investigated through the tensile test. The obtained results showed that an equiaxed ultrafine grain structure with nano-sized precipitates was created in the both ARBed and ARBed+Aged samples. The grain refinement was the predominant strengthening mechanism which was estimated to contribute 151 and 226 MPa to the ARBed and ARBed+Aged samples, respectively, while the dislocation and Orowan strengthening mechanisms were ranked second with regard to their contributions to the ARBed and ARBed+Aged samples, respectively. The overall yield strength, calculated through the root mean square summation method, was found to be in good agreement with the experimentally determined yield strength. It was also found that the presence of non-shearable precipitates, which interfered with the movement of the dislocations, would be effective for the simultaneous improvement of the strength and ductility of the ARBed+Agedsample .}, keywords = {Accumulative roll bonding (ARB),Aging,Strengthening mechanisms,Microstructure,Mechanical properties}, url = {https://jufgnsm.ut.ac.ir/article_64249.html}, eprint = {https://jufgnsm.ut.ac.ir/article_64249_28d2b887839c77be33a41185370a21cc.pdf} }