فهرست مطالب

Ultrafine Grained and Nanostructured Materials - Volume:51 Issue: 1, 2018
  • Volume:51 Issue: 1, 2018
  • تاریخ انتشار: 1397/04/14
  • تعداد عناوین: 12
  • Elham Kamali-Heidari, Ata Kamyabi-Gol, Mahmoud Heydarzadeh Sohi, Abolghasem Ataie Pages 1-12
    Electrochemical energy storage systems are categorized into different types, according to their mechanisms, including capacitors, supercapacitors, batteries and fuel cells. All battery systems include some main components: anode, cathode, an aqueous/non-aqueous electrolyte and a membrane that separates anode and cathode while being permeable to ions. Being one of the key parts of any new electronic device or electric vehicles, lithium ion batteries have gained great attention in recent years. Lithium ion batteries store/provide energy by insertion/extraction of lithium ions in/from the structure of the electrode materials in successive charge/discharge cycles. The energy and power densities, determine the batteries performance. In order to improve the energy/power density and cyclic life of a lithium ion battery, its electrode materials and electrolyte must be properly chosen. Cathode materials store energy through intercalation or conversion reactions, while the energy storage mechanism in anode materials are intercalation, conversion reactions or alloying/dealloying. Depending on the electrode material, one or more of the aforementioned mechanisms may take place which directly affect the battery performance. Each group of electrode materials have their own advantages and shortcomings; therefore, proper selection of the electrode material is an important issue in applicability of a lithium ion battery. This review covers the principles of energy storage in lithium ion batteries, anode and cathode materials and the related mechanisms, recent advancements and finally the challenges associated with enhancement of lithium ion batteries.
    Keywords: Lithium ion batteries, Anode, Cathode, Mechanism, Performance
  • Shiva Morady, Mohammad Talafi Noghani, Morteza Saghafi Yazdi * Pages 13-19
    In this study, molybdenum-copper/alumina nano composite was synthesized with mechano-chemical method using high energy planetary ball milling. The molybdenum oxide, copper oxide and aluminum powder were used as starting materials and reaction appeared to occur through a rapid combustion reaction process. The evaluation of powder particles after different milling times was studied by X-ray diffraction (XRD), differential thermal analysis/thermogravimetric (DTA/TG) and scanning electron microscopy (SEM). XRD results show that with increasing milling time at ambient temperature the peak intensities of powders decreases and significant peak broadening due to decrease in the size of crystallites observed. As a result, after 100 h milling time a molybdenum-copper/alumina metal matrix nanocomposite was formed which matrix had a crystallite size of about 42 nm for cu, calculated from Williamson-Hall equation. In fact by increasing the milling time after reduction of metal oxides, molybdenum dissolves in copper matrix and supersaturated Cu(Mo) solid solution with a homogenous distribution of nano-sized Al2O3 as reinforcement materials was formed. The thermal analysis curves of 10 minutes milled sample shows some peaks related to reduction of copper and molybdenum oxide with aluminum. In addition the small endothermic peak at 650 °C observed from DTA curve is due to the melting of remaining Al.
    Keywords: Ball milling, Mo-Cu-Al2O3, Nano-composite
  • Sajad Emami, Tohid Saeid *, Rasoul Azari Khosroshahi Pages 20-25
    Friction stir processing (FSP) was conducted on a SAF 2205 duplex stainless steel at advancing speed of 50 mm/min and rotational speed of 400 rpm. Characterization of evolved material was studied using electron microscopy equipped with electron back scattered diffraction (EBSD) system. The results indicated that the severe plastic deformation and the heat generated during the FSP developed a very fine microstructure in the stir zone (SZ). It was found that the finest grains with average grain size less than 1 µm were formed in the bottom of the SZ where the material was more likely to receive the lowest temperature in both constituent phases of ferrite and austenite. Therefore, it can be inferred that the material in the bottom of the SZ was less affected from the heat generated by the shoulder. The presence of such severe deformation along with the elevated temperature during the welding procedure inside the SZ activates the occurrence of continuous dynamic recrystallization mechanism throughout the material which seems to be responsible for grain refinement. Moreover, 111 and 110 pole figures of both constituent phases demonstrated that the rotating tool broke the initial microstructure, modified the pre-existence rolling texture of the starting material, and introduced simple shear texture components into the SZ.
    Keywords: Stainless Steels, Ferrite, Austenite, Shear Texture, Continuous Dynamic Recrystallization
  • Mohammad Naserifar, Seyyed Morteza Msoudpanah *, Somaye Alamolhoda Pages 26-31
    Single phase Mn0.8Zn0.2Fe2O4 powders were synthesized by solution combustion method. The solution combustion method relies on the exothermic self-sustained reactions in reactive solution containing of oxidizers and organic fuels. In this work, the effects of various amounts of glycine as fuel on the powder characteristics were investigated. The structure, cation distribution, microstructure, magnetic and microwave absorption properties were characterized by X-ray diffraction, electron microscopy and vibrating sample magnetometry techniques. The cation distributions determined by Bertaut method in which the observed reflection intensities compared with the calculated ones for supposed crystal structures. The Mn0.8Zn0.2Fe2O4 exhibited partially inverse structure in which Zn preferentially occupied tetrahedral (A) sites. The as-combusted Mn0.8Zn0.2Fe2O4 powders showed spongy structure due to the liberation a large amount of gaseous products. However, the porosity decrease with the increase of fuel content due to the increase of adiabatic combustion temperature. The saturation magnetization of the as-combusted Mn0.8Zn0.2Fe2O4 powders increased from 43 to 69 emu/g with the increase of  from 0.5 to 1 and then slightly decreases to 67 emu/g for =1.5. The highest saturation magnetization (69 emu/g) for =1 was attributed to the highest crystallite size and crystallinity. The coercivity also increased from 27 to 67 Oe with fuel content.
    Keywords: Mn0.8Zn0.2Fe2O4, Solution Combustion Synthesis, Fuel, Magnetic Properties
  • Arsalan Ravanbakhsh, Fereshteh Rashchi *, Mahmoud Heydarzadeh Sohi, Rasoul Khayyam Nekouei, Mohammadreza Mortazavi Samarin Pages 32-42
    In this study, porous zinc oxide nano-flakes were successfully synthesized by anodization method on zinc substrate in a 0.025 M NaOH and 0.05 M NH4Cl solution with the voltage of 10 V at room temperature. The field emission scanning electron microscopy’s (FESEM) images show the structural evolution during 90 min of the anodization process. They also demonstrate the dependency of growth of ZnO flakes on the grains of the zinc substrate. Regarding FESEM images and possible chemical reactions taking place during the anodization process, a growth mechanism and sequences for the formation of ZnO have proposed. The Pourbaix diagram also confirmed this possible mechanism. The elemental and phase analysis conducted on films proved the formation of the ZnO after the anodization process. The cyclic voltammetry showed the oxidation of zinc into zinc oxide is related to the -1.28 V peak and the peak of zinc oxide reduction is situated at -1.48 V. The band gap of anodized zinc foil was calculated to be 3.24 eV. The photocatalytic activity of synthesized thin films also was studied and the ImageJ software analysis showed a strong correlation between the photocatalytic activity and the portion of porosity in the synthesized films.
    Keywords: Porous Oxide, Anodization, Electrochemical Synthesis, Photocatalytic Activity, Band Gap
  • Mehrdad Mahdavi Jafari, Gholam Khayati * Pages 43-52
    In this study, Back-propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS) methods were applied to estimate the particle size of silica prepared by sol-gel technique. Simulated annealing algorithm (SAA) employed to determine the optimum practical parameters of the silica production. Accordingly, the process parameters, i.e. tetraethyl orthosilicate (TEOS), H2O and NH3 were introduced to BPNN and ANFIS methods. Average mean absolute percentage error (MAPE) and correlation relation (R) indexes were chosen as criteria to estimate the simulation error. Comparison of proposed optimum condition and the experimental data reveal that the ANFIS/SAA strategies are powerful techniques to find the optimal practical conditions with the minimum particles size of silica prepared by sol-gel technique and the accuracy of ANFIS model was higher than the results of ANN. Moreover, sensitivity analysis was employed to determine the effect of each practical parameter on the size of silica nano particles. The results showed that the water content and TEOS have the maximum and minimum effect on the particle size of silica, respectively. Since, water acts as diluent and synthesis of monodisperse silica in diluent solution will decrease the growth probability of nucleate, leading to a the lower silica particle size.
    Keywords: Silica Particle, fuzzy inference system, simulated annealing, artificial neural network, Process Parameters, Sol-Gel Methods
  • Zohreh Akbari, Alireza Babaei *, Abolghasem Ataie Pages 53-59
    In this paper, the effects of infiltration of La2NiO4 (LNO) as a mixed ionic and electronic conductor (MIEC) on the electrochemical performance of porous strontium doped lanthanum manganite (LSM) oxygen electrode of solid oxide cells, in the temperature ranges of 650-850 °C, is reported. XRD and FE-SEM results of the LNO sample calcined at 900 °C confirmed the formation of single phase LNO nanoparticles and uniform distribution of LNO into the porous LSM backbone with a mean particle size of 40 nm, respectively. To characterize the electrochemical behavior of half-cells, electrochemical impedance spectroscopy (EIS) measurement at temperature intervals of 50 °C was carried out. The LNO infiltrated LSM electrodes showed a noticeably decreased activation energy (from 130 to 103 kJ mol-1) and polarization resistance (from 26.2 to 2.5 Ωcm2 at 650 °C) under open circuit voltage (OCV) condition. Besides, the equivalent circuit (EC) modeling revealed that LNO addition has a major effect on the low frequency arc, which is attributed to the surface exchange mechanisms. Decreased amounts of activation energy and polarization resistance of the infiltrated LSM electrode compared to those for the pure one suggest that introduction of LNO nano-particles to the microstructure of LSM is a promising approach to achieve better electrochemical performance even in the low temperature of 650°C.
    Keywords: La2NiO4, Solid Oxide Cell, LSM, Electro Catalyst, Infiltration
  • Samira Agbolaghi *, Saleheh Abbaspoor Pages 60-70
    The multi-walled carbon nanotubes (CNTs) and reduced graphene oxide (rGO) nanosheets were functionalized with 2-hydroxymethyl thiophene (CNT-f-COOTh) and 2-thiophene acetic acid (rGO-f-TAA) and grafted with poly(3-dodecylthiophene) (CNT-g-PDDT and rGO-g-PDDT) to manipulate the orientation and patterning of crystallized regioregular poly(3-hexylthiophene) (P3HT). Distinct nano-hybrid structures including double-fibrillar (5.11−5.18 S/cm), shish-kebab (2.19−2.28 S/cm), and stem-leaf (6.96−7.51 S/cm) were developed using modified CNTs and P3HT. The most effective parameter on morphology of donor-acceptor supramolecules was the surface functionalization and grafting. The electrical conductivities of supramolecules based on P3HT and rGO, rGO-f-TAA, and rGO-g-PDDT ranged in 3.81−3.87, 3.91−3.95, and 10.67−10.70 S/cm, respectively. P3HT chains preferred to interact with their thiophene rings with bared rGO and CNT surfaces, resulting in a conventional face-on orientation. In P3HT/rGO-f-TAA and P3HT/CNT-f-COOTh supramolecular nanostructures patterned with P3HT, the orientation of P3HT chains changed from face-on to edge-on, originating from the strong interactions between the hexyl side chains of P3HTs and functional groups. Nano-hybrids based on grafted rGO demonstrated a patched-like morphology composed of flat-on P3HTs with main backbones perpendicular to the substrate. Based on the ultraviolet-visible and photoluminescence analyses, the flat-on orientation was the best for P3HT chains assembled onto CNT and rGO, which was acquired for CNT-g-PDDT and rGO-g-PDDT nano-hybrids.
    Keywords: Carbon Nanotube, Reduced Graphene Oxide, Orientation, Grafting, Functionalization, Nano-hybrid
  • Rashadoddin Zamani, Hamed Mirzadeh *, Massoud Emamy Pages 71-76
    The effect of chemical composition and the hot rolling operations on the microstructure and mechanical properties of in situ aluminum matrix composite with Mg2Si phase as the reinforcement was studied. It was revealed that the modification by phosphorous results in the rounder (more spherical) primary and secondary (eutectic) magnesium silicide intermetallics. During hot rolling, the primary particles underwent mechanical fragmentation and the fragmented particles moved along the rolling direction. Moreover, the eutectic Mg2Si fragmented and uniformly dispersed in the microstructure. By increasing the reduction in thickness, it was almost impossible to distinguish primary particles from eutectic ones due to excessive fragmentation of particles. These observations were related to the brittleness of Mg2Si phase and the elongation of the matrix grains during rolling. The grain size of the matrix also changed due to the occurrence of recrystallization and the average grain size decreases from ~ 90 µm to 7 µm for the 98% rolled sample. The change in mechanical properties was related to the fragmentation of particles, destroying the eutectic network, magnificent grain refinement of the matrix, the retardation of recrystallization by the dispersed particles at grain boundaries of aluminum grains, and the fast cooling of thin sheets at high reductions in thickness.
    Keywords: In situ composite, Hot rolling, Microstructure, Tensile properties
  • Narges Ahmadi Khoei, Mahshid Kharaziha *, Sheyda Labbaf Pages 77-83
    Piezoelectric materials are the group of smart materials which have been recently developed for biomedical applications, such as bone tissue engineering. These materials could provide electrical signals with no external source power making them effective for bone remodeling. Between various types of materials, BaTiO3 and CaTiO3 are nontoxic piezoelectric ceramics, which recently have been introduced for bone tissue engineering. It is expected that, the combination of these two ceramics could provide suitable piezoelectricity, bioactivity and biocompatibility for bone tissue engineering applications. The aim of this research is to synthesize (BaxCa1-x)TiO3 (x= 0, 0.6, 0.8, 0.9 and 1) nanopowder using sol-gel method. Moreover, the incorporation of Ca ions in the structure of (BaxCa1-x)TiO3 nanoparticles was chemically, structurally and biologically studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies confirmed the role of substituted Ca content on the chemical properties and morphology of particles. Indeed, increasing the amounts of Ca ions resulted in the reduced crystallite size. While incorporation of more than 20 at.% Ca resulted in the formation of a biphasic structure, monophasic solid solution without any secondary phase was detected at less Ca content. Moreover, SEM images revealed that Ca substitution reduced particle size from 70.5 ±12 nm to 52.4 ±9 nm, while the morphology of synthesized powders did not significacntly change. Furthermore, incorporation of upon 10 at.% Ca content within (BaxCa1-x)TiO3 significantly promoted MG63 proliferation compared to pure CaTiO3.
    Keywords: Piezoelectric, Bone Tissue Engineering, BaTiO3, CaTiO3, Sol-gel
  • Mohammad Ghorbanpour * Pages 84-89
    This study was carried out to synthesize 1D inorganic nanostructure using an electrochemical method without any template and additives. Copper foils were anodized in a KOH bath and were tested for their antibacterial performance. After anodizing, the obtained samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) to determine the corresponding morphology and crystal structure, respectively. Finally, the antibacterial activity of the samples against both E. coli and S. aureus was tested by agar diffusion test. The typical porous surfaces were realized in all samples. These micropores may be beneficial to cell attachment. The morphology of the anodized copper exhibited when the concentration of OH− kept on going up, micropores and simultaneously nanoparticles were formed on the surface. By increasing the concentration of KOH, the water contact angle with anodized Cu foil varied within the range of 65.4 to 89.7°. Parent copper foil did not show antibiotic activity. The anodized copper exhibited acceptable antibacterial activities. The antibacterial action was the same for anodized copper at different concentration of OH−, which had nothing to do with the concentration of KOH electrolyte. The obtained results indicated that the porous copper could be employed to improve antibacterial activities of pure copper to meet the needs of bioactive surfaces.
    Keywords: Antibacterial, Anodizing, Porous, Copper
  • Alireza Shafei, Saeed Sheibani * Pages 90-95
    In this study, TiO2-10%wt. carbon nanotube (CNT) nanocomposite powders were synthesized by sol-gel method at various hydrolysis rate affected by different reaction agents of acetyl acetone and benzyl alcohol. Crystallization of TiO2 was then achieved through calcination at 400 °C. The properties of nanocomposite powder investigated by scanning electron microscopy, X-ray diffraction and diffuse reflectance spectroscopy. The results showed that, the crystalline TiO2 with anatase structure was produced after calcination. The crystallite size of TiO2 depended on the hydrolysis rate which was increased from 25 nm at higher hydrolysis rate by benzyl alcohol to 55 nm at slower hydrolysis rate by acetyl acetone. Before calcination, the results have shown that the slower hydrolysis rate yields relatively large particles with a plate like morphology in contrast to the presence of small particles with significant agglomeration at higher hydrolysis rate by benzyl alcohol. After calcination, high hydrolysis reaction through the use of benzyl alcohol offers easy access to the TiO2-10%wt. CNT nanocomposite with well controlled coating and desirable interactions between TiO2 and the CNTs. The thickness of TiO2 coating on CNTs in this way was 80 nm. Also, TiO2 particle size depended on the hydrolysis rate, decreased from 1 μm in presence of acetyl acetone to 150 nm in presence of benzyl alcohol. The band gap energy at higher hydrolysis rate by benzyl alcohol was 2.95 eV.
    Keywords: Nanocomposite, Carbon Nanotube, TiO2, Sol-gel, Hydrolysis rate