M.godarzi, A. Saidi,
Volume 33, Issue 2 (3-2015)
Abstract
In recent years, much research has been performed in the field of nanomaterials synthesis using mechanochemical process. In this research, TixAly/Al2O3 ceramic matrix nanocomposite was produced by the mechanochemical method. Aluminum and inexpensive titanium oxide powders were used as raw materials, and milling was performed under N2 atmosphere. The results showed that reduction of TiO2 by Al is the first step of synthesis process, and then Ti reacts with residual Al. The synthesis after 10 hours of milling resulted in titanium aluminide and aluminium oxide. With the increase of milling time to 80 hours, titanium aluminide quantity was increased. Also, the results showed that the heating of samples containing titanium aluminide in the argon and nitrogen atmospheres does not lead to complete decomposition of aluminides.
Sh. Seyyedin, S. M. Hosseini-Golgoo, M. H. Ghezel Ayagh, F. Agend,
Volume 33, Issue 2 (3-2015)
Abstract
In this paper, manufacturing and evaluation of ethanol gas sensors based on thin films of nanostructure tin oxide have been investigated. SnO2 thin films were prepared by both thermal evaporation (type I) and sputtering (type II) methods and heat treated on silicon wafer substrates. Scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) and energy dispersive spectra (EDS) are employed to study the morphology and chemical composition of the semiconductor samples. Nano-scale grain size with homogenous distribution showed in SEM images of both types. Sensors resistance in air and its variation-transient response toward ethanol vapours (3000 ppm) was determinated. The response of the stable sensors was obtained 3 and 1.18 for type I and type II, respectively. That showes thin film of nanostructure tin oxide by thermal evaporation (type I) has better sensitivity than the other. More effective surface, adsorption sites and base-line resistance due to the more fine grain size in type I nanostructure, are its important reasons. however, it is slow due extensive rise time and fall time.
Sh. Masoumi, Hosein Sarpoolaky, B. Eftekhari Yekta , M. Soltanieh,
Volume 33, Issue 2 (3-2015)
Abstract
Hercynite, FeAl2O4, was synthesized via molten salt synthesis method in the coke bed at 800°C with 3h of holding time. It was synthesized by reacting stoichiometric compositions of Al2O3 and FeCl2.4H2O in eutectic compositions of alkaline chlorides NaCl-KCl-LiCl. The reactant to salt ratio was 1 to 3. The phase formation, and morphology of these synthesized powders after washing and filtration were characterized via X-ray diffraction (XRD), and scanning electron microscopy (SEM). Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were performed at temperatures up to 1000 °C at a heating rate of 10 °C/min in argon atmosphere, to elucidate the different reaction mechanisms in the synthesis of Hercynite by the molten-salt method. The effects of processing parameters including the temperature and holding time on the formation of FeAl2O4 were investigated. The results demonstrated that the formation of FeAl2O4 spinel could be initiated at 700°C. By increasing the temperature to 900 °C and holding time, the amounts of FeAl2O4 particles in the resulting powder increased at
the expense of Hematite and Al2O3. Morphology of the synthesized powder was cubic and tetragonal, increased by increasing the holding time and temperature.
M. Mashhadi, A. Abdollahi, Z. Nasiri,
Volume 33, Issue 2 (3-2015)
Abstract
In this study, ZrB2-HfB2 composite was produced by pressureless sintering method. MoSi2 B4C and SiC particles were used as reinforcement. ZrB2 powder was milled in planetary ball mill apparatus and then reinforcement particles were added to the milled powder. The composite powders were then CIPed and sintered at 2100oC and 2150oC. Scanning electron microscopy (SEM) with an energy dispersive X-ray spectrometer (EDS), flexural test, and resonance frequency method were used to compare the added particle effects on mechanical properties and pressureless sintering behavior of ZrB2-HfB2 composite. The analysis showed that the ZrB2-HfB2-MoSi2-SiCnano composite displays the largest gain in flexural strength. Furthermore, increasing the sintering temperature leads to an increase in flexural strength of samples.
S. Mirtalebi , D. Ghasemi ,
Volume 33, Issue 2 (3-2015)
Abstract
In the present study, pure Aluminum powder with 5%wt Titanium Dioxide was mechanically milled at different times. Using phase analysis through X-ray diffraction (XRD), it was found that increasing of the milling times over 10 hours causes the reduction of Titanium by Aluminum and formation of Al2O3 in the structure. Also, it was shown that if the process persists, Aluminum reacts with Titanium and causes the formation of Al3Ti in the composition. The reactions were studied through the thermodynamic relations. Furthermore, after distribution of reinforcement particles in the matrix,
using X-ray diffraction peak broadening, according to Williamson-Hall equation, the mean crystallite size and lattice strain were determined, and by scanning electron microscopy (SEM), the structure and morphology of the powder particles were studied.
K. Sheybani, M.h. Abbasi, M. Shamanian ,
Volume 33, Issue 2 (3-2015)
Abstract
in this research, the kinetics of carbothermic reduction of molybdenite in the presence of sodium carbonate was studied. For this purpose, mixed powder of molybdenite, graphite, and sodium carbonate with 1:4:2 mole ratio was investigated using simultaneous thermal analysis (STA) at the heating rates of 10, 15 and 20 0C /min. The results of thermal analysis were evaluated through Friedman, Kissinger, Ozawa and Coats-Redfern methods. The activation energy of reduction reaction was determined 220 kj/mole, and it was found that the reaction was chemically controlled. To study the reaction mechanism, the mixed powder was heated to 400, 800 and 1100 0C in argon atmosphere at the heating rate of 10 0C/min. X- Ray diffraction
of the reaction products and thermodynamic analysis at these temperatures indicated that carbothermic reduction of molybdenite in the presence of sodium carbonate would advance through the formation of intermediate phases, Na2MoO4 and MoO2
M. Rahmani, K.janghorban, S. Otroj,
Volume 33, Issue 2 (3-2015)
Abstract
In this study, the effect of different amounts of Y2O3 on the properties of mullite-zirconia composites was
investigated. For this purpose, these composites were fabricated by reaction-sintering of alumina and zircon as raw materials.
Besides, the slip casting method was used for forming these composites, and sintering process was carried out at 1600 °C. Then,
the physical and mechanical properties, phase composition and the microstructure of these composites were investigated. The
results showed that yittria addition up to 0.5 wt.% has no effect on the properties of these composites. Besides, addition of more
than 0.5 wt.% yittria formed solid solution with zirconia grains and led to stabilization of tetragonal zirconia phase and
increasing of its amount. Hence, yittria addition increases the hardness and bending strength of composite by stabilizing
tetragonal zirconia phase and then, decreasing the micro-crack formation during zirconia phase transformation. As results show,
addition of 0.75 wt.% yittria leads to a considerable increase in the bending strength
Reza Eshghi, S.m.hadavi, V.varmazyar,
Volume 33, Issue 3 (3-2015)
Abstract
In this research, Ti-6Al-4V alloy was brazed with 410 stainless steel by three different filler metals as silver-base,
nickel-base, and titanium-base alloys. In order to obtain optimum clearance, brazing was done in three different clearances
of 0.02, 0.04 and 0.06 mm. Also, the strength and hardness of the brazing zone were investigated. The results of shear strength
showed that the brazed samples with titanium-base alloy at the clearance of 0.02 mm had the maximum strength among the
different samples which was 149.5 MPa.
R. Jahadi Naeini, M. Sedighi, H. R. Jahedmotlagh,
Volume 33, Issue 3 (3-2015)
Abstract
In this paper, the effect of Equal Channel Angular Pressing (ECAP) process on the structure and mechanical properties of AM30 magnesium alloy was studied. The results showed a considerable effect of ECAP process on creating an ultrafine grain size structure. Scanning Electron Microscope indicated that the grain size dropped from 20.4 µm in the extruded form to 7.2 µm in the first pass and 3.9 µm in fourth pass. The fourth pass presented higher ductility and lower yield stress in comparison with the extruded case. This behavior can be explained based on higher rate of texture softening versus the effects of the grain refinement on strength. The hardness test on the samples cross-section showed an increase in hardness and a uniform strain distribution at higher ECAP passes.
F.s. Sayyedan, M.h. Fathi, H. Edris, A. Doostmohamadi, V.s., Mortazavi, F. Shirani,
Volume 33, Issue 3 (3-2015)
Abstract
The objective of this study was to synthesize glass ionomer–forsterite nanocomposite and study the effect of
incorporating forsterite nanoparticles to the ceramic part of glass ionomer cement in order to improve mechanical properties and
bioactivity. So, Forsterite nanoparticles were made by the sol-gel process using different weight percentages added to the ceramic
part of commercial GIC (Fuji II GC). X-ray diffraction (XRD) was used in order to characterize and determine grain size of the
produced forsterite nanopowder. In order to study the mechanical properties of the produced glass ionomer cement-forsterite
nanocomposite, the compressive strength (CS), three-point flexural strength (FS) and diametral tensile strength (DTS) of
specimens were measured. Statistical analysis was done by one Way ANOVA and differences were considered significant if
P‹0.05. The morphology of fracture surface of specimens was studied using scanning electron microscopy (SEM) technique.
Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electron microscopy
(SEM), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results of XRD analysis confirmed the
nanocrystalline and pure forsterite synthesis. According to the mechanical properties measurements, the optimum weight
percentages of forsterite nanoparticles for enhancement of CS, FS, and DTS were obtained equal to 3, 1 and 1 wt.%, respectively.
Statistical analysis showed that the differences between all the groups were significant (P<0.05). SEM images and results of the
ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Glass ionomer-forsterite nanocomposite containing 1 to
3 wt.%-forsterite nanoparticles can be a suitable candidate for dentistry and orthopedic applications due to the improvement of
mechanical properties and bioactivity.
Zahra Omidi, Saeed Reza Bakhshi, Ali Ghasemi,
Volume 33, Issue 3 (3-2015)
Abstract
Silicon nitride has attracted a considerable attention because of its excellent properties such as high-temperature strength, good oxidation resistance, high corrosion resistance, good thermal shock resistance, high creep resistance and good thermal and chemical stability. There are several different fabrication methods for synthesizing Si3N4 particles. Such methods are mostly costly and kinetically slow and require lengthy heat treatment. In this study, Si3N4 compounds were synthesized by means
of mechanical milling. In the mechanical milling route,Si powder (≤99.0%) was milled under nitrogen gas for 25 h and heated at various temperatures 1100-1200-1300 and 1400 C for 1 h at the nitrogen atmosphere at a rate of 200 ml/min. Silicon powder was also annealed under a similar condition in order to evaluate the impact of milling process on the low temperature synthesizing of Si3N4. Phase identification and microstructural characteristics of products were evaluated by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The Fourier transform infrared spectroscopy and thermal analysis were used for characterization of the formed bands and thermal treatment of the sample, respectively. The obtained results exhibited that Si3N4 powder was fully formed with two kinds of morphologies including globular particles and wire with a width of 100–300 nm and length of several microns at sintering temperature of 1300 C. This was confirmed by the Si–N absorption bonds in the FTIR trace. Based on XRD results, 25 h milling reduced temperature of reaction remarkably in comparison with direct nitridation of Si powders for 1 h. With an increase in the reaction temperature, the Si3N4 samples had a phase transformation 𝛂→𝛃, and variation of the morphology followed the vapor–liquid -solid mechanism.
M.r. Garsivaz Jazi, M.a. Golozar , K. Raeissi,
Volume 33, Issue 3 (3-2015)
Abstract
In this study, the chemical composition, thickness and tribocorrosion behavior of oxide films prepared on Ti-6Al-4V alloy by anodising treatment in H2SO4/H3PO4 electrolyte at the potentials higher than the dielectric breakdown voltage were evaluated. The thickness measurement of the oxide layers showed a linear increase of thickness by increasing the anodizing voltage. The EDS analysis of oxide films demonstrated precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. Tribocorrosion results indicated that the tribocorrosion behavior of samples was significantly improved by anodising
process. Furthermore, the tribocorrosin performance of thesamples anodised at higher voltages was enhanced. SEM and EDS of worn surfaces indicated that the oxide layer on the samples anodised at lower voltages was totally removed, but for the samples anodised at higher voltages, the oxide layer was only locally removed within the wear track. Moreover, measurement of wear volume of the treated samples exhibited lower values on the samples anodised at higher voltages.
Fatemeh Mohtaram, Vahid Mottaghitalab, Gholamreza Baghersalimi, Akbar Khodaparast Haghi,
Volume 33, Issue 3 (3-2015)
Abstract
Today, along with the advances in circuit printing technology it has become possible to fabricate band lines integrated with circuit elements. The band lines are known as microstrip lines and the whole packages are called microstrip antennas. The microstrip antennas have three layers, including conductive patch layer, dielectric sub layer, and ground conductive layer. One of the most important problems of prevalent antennas is their inflexibility, which was addressed in the current paper using textile based structure with proper flexibility and flexural stiffness. This was done using ink jet printing techniques followed by electrolytic plating to provide diverse antenna patterns based on nickel particles. The coated surface was characterized by scanning electron microscope, elemental analysis and optical microscope. Moreover, the washing fastness and the other physical and mechanical specifications were measured using standard techniques. The elemental analysis of metal-coated fabric clearly indicated a high level of nickel. Furthermore, the morphological investigation proved the formation of homogenous nickel nanoparticle in a diameter range of 100-500 nm with an evident boundary and semi-spherical shape. In addition, the cumulative presence of particles in a sequence followed a cabbage-like structure originating from metallic crystals. The washing fastness tests revealed a high stability in electrical resistance after several washing steps. In the meantime, the antenna gain and the corresponding bandwidth were measured using spectrum analyzer. The results indicated a 1 kHz increase in bandwidth and 11 dB decrease in antenna gain for a large size compared to a small one. Meanwhile, the bandwidth of rectangular pattern showed a 0.2 kHz increase and 2.5 kHz decrease compared to spiral pattern. Finally, the four-probe electrical conductivity test demonstrated a high level of conductivity around 2632 S/cm.
R. Tajalli, H. Baharvandee, H. Abdizadeh,
Volume 33, Issue 3 (3-2015)
Abstract
In this research, ZrC nano particles were synthesized by self-propagating high temperature (SHS) using the mixed powder of ZrO2-C-Mg and NaF or NaCl diluent. The effect of different proportions of raw materials, milling time, composition
of the diluent and also pickling on the synthesis of ZrC was investigated. Optimal amounts of magnesium and sodium fluoride for the synthesis of ZrC were 2.8 and 2 mol, respectively. Milling process of 120 minutes decreased the diffusion gap of raw material and increased the combustion reaction progress. XRD and SEM analysis showed that the NaF diluent more than NaCl caused a reduction in the size of the particles of ZrC and increased the progress of the combustion reaction. Synthesized samples were subjected to pickling in order to remove impurities of MgO by 37% HCl, and distilled water was used to wash off NaF and NaCl residues. ZrC particle size of different samples were in the range of 50-90 nm.
M. Tehrani Dehkordi, S. H. Bahrami, R. Nategi Jahromi,
Volume 33, Issue 3 (3-2015)
Abstract
In this study, the effects of different parameters on charpy impact properties of pure and hybrid composite laminates reinforced with basalt and glass filaments were investigated. For this purpose, five types of basalt and glass laminates with
quasi-isotropic stacking sequence, namely, a pure basalt, a pure glass, two inter-ply hybrid and one intra-ply hybrid composites were produced. Epoxy resin was used as matrix material. After that, the impact test was performed and the average absorbed energy of each type of specimens was determined. The results indicated that the pure basalt and nylon laminates had the highest and least absorbed energy, respectively. The hybrid laminates had the absorbed energy somewhere between the pure basalt and glass ones. Also, between the hybrid composites, the intra-ply laminate had a better impact performance than the inter-ply ones.
S.m.h. Mirbagheri, M. Daneshmand, Y. Tabatabaie,
Volume 33, Issue 3 (3-2015)
Abstract
In this paper, the behavior of energy absorption of crush-boxes, made of Aluminum foam advanced material, was investigated based on foam cellular structure homogeneity. Therefore, thin-walled tubes of Cu-Zn30wt.%.brass alloy with 27 mm diameter and 1 mm thickness were filled with A356-10vol.%SiC-Xwt.%. of TiH2 foam liquid. Foam samples with 1, 1.5, 2wt.%. of TiH2 were prepared by Form Grip into the brass tubes in order to produce crush-box .Then the crush-boxes as energy absorber elements were compressed by un-axial loading and then behaviors of progressive buckling foams were measured. Results showed by decreasing A356-10vol.% SiC foam density from 0.93 to 0.88 and then 0.43 g/cm3, the energy absorption would be changed from 12955 to 13465 and then to 11192 J, respectively. The sample with 1.5wt.% of TiH2 and density of 0.88 g/cm3 had the maximum energy absorption. Also, the results of foams cellular structure images showed that foams of homogenous cellular structure had a sizeable effect on the progressive buckling behavior. We developed a new parameter as "sorting coefficient", which can release the foams cellular structure non-homogeneity, and change the crush-boxes energy absorption during the progressive plastic buckling.
P. Zarrabian, M. Kalantar, M. Mosallaeepour, A. Mashreghi,
Volume 33, Issue 3 (3-2015)
Abstract
Nickel ferrite based cermets and their relevant composites have been widely used as inert anodes for aluminum electrolysis due to their good combination of chemical resistance, thermal stability and mechanical properties. In this study, various NiO/NiFe2O4 composites consisting of 5, 10 and 15% NiO in conjunction with Cu/NiFe2O4 cermets containing 0.5, 10 and 15% Cu were prepared by powder metallurgy method. The degradation resistance of the developed inert composites was examined under hot corrosion condition by plunging samples in to the molten electrolyte at 1000ºC. The strength, toughness, hardness, relative density, microstructural observation, phase analysis and electrical resistivity were evaluated by 3-points bending tests, Vickers method, Archimedes method, scanning electron microscope, x-ray diffraction and conventional direct current four-probe techniques, respectively. The experimental results for NiO/NiFe2O4 composites showed that a significant improvement of toughness and degradation resistance continuously occurred with a moderate decrease in strength by increasing NiO content, while the relative density was increased only up to 5%NiO content. By increasing the Cu content in the cermet samples, all the properties such as strength, toughness and electrical conductivity were improved considerably but the degradation resistance decreased.
P. Seifollahzadeh, M. Kalantar, A. Mashreghi, S.s. Ghasemi,
Volume 34, Issue 3 (12-2015)
Abstract
Mullite and alumina are common in high-temperature applications because of their low thermal expansion coefficient and good thermal shock resistance. Evolution of SiC in the matrix and using it as reinforcing phase can improve thermo-mechanical properties of these materials. Also, in-situ formation of the reinforcing phases by using inorganic materials is an economical process. In this work, crystallization of SiC as reinforcing phase in the matrix of mullite-alumina by carbothermal reaction processes of inorganic materials (andalusite and kaolinite) was studied. According to the ratio of C/SiO2 and process conditions, some properties of the composite such as phase transformation, microstructure and physical and mechanical properties were investigated. The results showed that optimal ratio of C/SiO2 and firing temperature of densification to form SiC crystals were 3.5 and 1600°C for andalusite and 5.5 and 1500°C for kaolinite.
M.a. Yousefpour, F. Safari Kooshali, B. Khoshandam,
Volume 34, Issue 3 (12-2015)
Abstract
The purpose of this work was to study the hydrogen adsorption on the surface of mesoporous materials based on silica (SBA-16) modified with palladium via temperature. Since mesoporous silica materials have a high specific surface area, and the ordered mesoporous size of 2-10nm, they are suitable for adsorption and storage of hydrogen. SBA-16 is suitable for this purpose due to its cubic crystalstructure and open pores. Single-stage sol-gel method was used to produce nanostructure composite from salt of palladium (PdCl3) and mesoporous silica precursor. The aging time was selected as 12 hr at 80˚C. Furthermore, the obtained materials were heated at 550˚C for 6 hr to remove surfactant and to form pores. Then the materials were characterized by large angle and small angle x-ray diffraction analysis, and hydrogen absorption analysis at upto 200kPa pressure at three different temperatures of -196˚C (77 K), -123˚C (150 K) and 30˚C (303 K). Furthermore, adsorption-desorption of nitrogen gas was studied. The surface morphology was observed by field emission scanning electron microscope (FESEM). In addition, the amount of palladium, oxygen, and silicon were measured by using energy dispersive spectroscopy) EDS ). Finally, the functional groups on the surface of mesoporous silica materials were evaluated using Fourier transform infrared spectroscopy (FTIR). The results of XRD and EDS analyses confirmed the presence of palladium and palladium oxide in mesoporous amorphous silica. In addition, BET results showed that addition of palladium in SBA-16 decreased the surface area, and produced 791 and 538m2/g for SBA-16 and SBA-16/Pd, respectively. Hydrogen absorption in nano structure composite was decreasing with temperatur in comparison with SAB-16. On the other hand, the maximum hydrogen absorption in the nano structure composite containing palladium was obtained at -196˚C (77 K).
A. Ghotbi Varzaneh, P. Kameli, F. Karimzadeh, H. Salamati,
Volume 34, Issue 3 (12-2015)
Abstract
In this investigation, Ni47Mn40Sn13 ferromagnetic shape memory alloy was prepared by mechanical alloying. The metal powders were ball milled in argon atmosphere for 20 hours. X-ray diffraction pattern confirmed formation of crystalline structure of Heusler alloy. As-milled powder samples were sealed in quartz tubes under high vacuum and subjected to heat treatments at 950°C for different time durations. Then, the effect of isothermal ageing on structural, magnetic and electrical properties of samples was investigated. Results of electrical resistance displayed a metal-like behavior around martensitic transformation. The results showed that 16 hours of annealing was the optimal time for producing this alloy which could be an appropriate candidate for magnetic refrigerant.
