Showing 110 results for Ge
H. R. Shahverdi, R. Alipour Mogadam,
Volume 38, Issue 2 (9-2019)
Abstract
Creep age forming (CAF) process is a novel metal forming method with major benefits including improved mechanical properties and cost reduction for aviation industry applications. CAF happens due to creep phenomenon and stress-release during the artificial aging of heat-treatable aluminum alloys. In this work, the creep age forming of 7075 Aluminum alloy at 120, 150 and 180 °C for 6, 24 and 48 h was done; tensile and hardness tests were used to characterize the samples. Results on spring-back revealed that it was influenced by time and temperature; by increasing the time and temperature, it was reduced from 54.1 to 39.51. Mechanical property evaluation also showed that by increasing the time, the strength and hardness could be enhanced due to microstructural evolution and precipitation during the CAF process. According to the mechanical and CAF results, two samples were selected as the optimum ones and their work hardening behavior and fracture surfaces were investigated
A. Jafari, S. Khademi, M. Farahmandjou, A. Darudi, R. Rasuli,
Volume 38, Issue 2 (9-2019)
Abstract
Titanium dioxide nanoparticles (TiO2) are known as a widely used photocatalyst. In order to improve the performance of these nanoparticles, the recombination of the electron-cavity pair must be reduced and the absorption rate of the visible region should be expanded. One way to increase the performance of these nanoparticles is using cerium doped TiO2. In the present study, pure and doped titanium dioxide nanoparticles were made by the electrical discharge method. The effect of cerium dopants on the structural, morphological and optical properties were studied by x-ray diffraction (XRD), scanning electron microscopy (FESEM), diffused reflection spectroscopy (DRS), photoluminescence (PL) and infrared fourier transform (FTIR) spectroscopy analyses. XRD analysis revealed that the size of TiO2 nanocrystals was decreased to 7.7 nm. The FESEM morphology of the samples also showed that the uniformity of the Ce doped TiO2 was decreased. Further, the DRS results indicated that the band gap energy of Ce-TiO2 was decreased to 2.24 eV. The photoluminescence results demonstrated that the intensity of PL was reduced for the Ce-TiO2 sample, which reduced the recombination of the electron-hole coupling and increased the photocatalytic activity in the doped sample.
M. Afrashi, D. Semnani, Z. Talebi,
Volume 38, Issue 2 (9-2019)
Abstract
In this study, adsorption of fluconazole on silica aerogel was performed successfully by the immersion method in the 1% solution of fluconazole-ethanol at the ambient condition and without using the supercritical method. The hydrophobic and hydrophilic silica aerogels were synthesized by the two-stage sol-gel method and dried at the ambient temperature. This method had most of drug loading at 24 h. It was 1.92% and 1.98% for the hydrophilic and hydrophobic silica aerogels, respectively. Physical properties of the synthesized aerogels were studied by the nitrogen absorption and desorption tests. The presence of fluconazole and the chemical structure of the samples were determined by fourier-transform infrared spectroscopy (FTIR). As well, the loading and release of the drug were investigated using a spectrophotometer. The results showed the structure of the synthesized aerogels had a pore diameter of 6-8 nm and a surface area of about 800-100 m2/g. The study of the drug release also revealed that the release rate of fluconazole in the hydrophilic silica aerogel was higher than that of the hydrophobic sample.
N. Alirezaei Varnosfaderani, S. E. Mousavi Ghahfarokhi, M. Zargar Shoushtari,
Volume 38, Issue 3 (12-2019)
Abstract
In this paper, W-type SrCo2Fe16O27 hexaferrite nanostructures were synthesized by sol-gel auto-combustion method. Effect of annealing temperature on the structural, magnetic and optical properties of these SrCo2Fe16O27 nanostructures was investigated. In order to determine the annealing temperature of samples, the prepared gel was examined by thermo-gravimetric and differential-thermal analyses. Morphology and crystal structure of the prepared samples were characterized by field emission scanning electron microscopy and X-ray diffraction pattern. Based on X-ray diffraction results, at annealing temperature of 1000 °C, the maximum amount of main phase formed. A planar morphology was spectroscopy for the synthesized samples through scanning electron microscope images. Fourier transform infrared analysis was used to confirm the synthesis of the main properties obtained of samples were measured by the vibrating sample magnetometer and the results showed that by increasing temperature, magnetic saturation increases. Moreover, optical properties of samples were investigated by ultraviolet–visible absorption and photoluminescence spectroscopies. The result of measurements of the energy gap approximately is same in the ultraviolet- visible and photoluminescence spectroscopes and also the energy gap is constant with increasing temperature.
F. Mohammadi Bodaghabadi, M. R. Loghman Estarki, M. Ramazani, A. Alhaji,
Volume 38, Issue 3 (12-2019)
Abstract
In this research, synthesis of lithium fluoride (LiF) nanoparticles by fluorolytic sol-gel method has been studied. Moreover, the effect of lithium ion to fluorine source molar ratio and calcination temperature on particle size and phase of LiF nanoparticles were investigated. Lithium acetate (C2H3LiO2), trifluoroacetic acid (TFA), ethylene glycol monobutyl ether and oleic acid were used as sources of Li+ and F- ions, solvent and growth inhibitor, respectively. Thermal and X-ray diffraction (XRD) analyses as well as field emission scanning electron microscopy (FESEM) were used to investigate thermal behavior of the primary gel and to determine the phase and morphology of samples, respectively. The results showed that the 2: 1 molar ratio of Li+/ TFA and the calcination temperature of 400 °C result in LiF nanoparticles with a mean particle size of 80-100 nm.
M. H. Musazadeh, R. Vafaei, E. Mohammad Sharifi, Kh. Farmanesh,
Volume 38, Issue 3 (12-2019)
Abstract
Finite element (FE) simulations in conjunction with experimental analysis were carried out to characterize the deformation behavior of an AISI 321 austenitic stainless steel (ASS) during cold pilgering process. The effect of process parameters including feed rate (4 and 8 mm) and turn angle (15, 30 and 60°) on damage build-up were also evaluated. The Johnson-cook model was used to simulate the flow behavior of material. By considering compressive stresses, a new revised Latham-Cockcraft damage was calculated and used to determine the optimum process parameters. It was found that the radial and hoop strains in all friction conditions were compressive, while the axial strains were observed to be tensile. The amount of strain (whether it is compressive or tensile strain) was also higher on the outside of the tube compared to its inside. By considering fatigue cycles of a tube element during the process, the feed rate of 8mm, turn angle of 60° and the lowest coefficient of friction were determined as optimum parameters.
M. Emami, Sh. Hayashi,
Volume 38, Issue 3 (12-2019)
Abstract
The outer surface of heat exchanger tubes that work under fluidized bed waste or biomass incineration is exposed to severe high-temperature erosion-corrosion (E-C). To evaluate the behavior and enhance the service life of the tubes, the real service conditions ought to be simulated in the laboratory. In this study a test rig with a fluidized bed of hot sand was designed and manufactured to expose nickel-based SFNi4 alloy to high-temperature E-C. In order to increase the corrosiveness of the environment, the silicon oxide sand was mixed with 0, 0.5 and 1 wt.% of a mixture of NaCl and KCl salts with 1:1 molar ratio. The erosive conditions of the environment were changed by altering air flow rate from 20 to 25 L/min and changing the sand incident angle from 45 to 90 degrees. The rate of material removal was calculated by measuring the thickness of each sample before and after the test. After each experiment, the surface and cross-section of specimens were studied using SEM and EDS analysis. Finally, the optimum E-C parameters to ensure actual industrial conditions were obtained.
M. R. Loghman Estarki, H. Ghalibaf Tousi, E. Mohammad Sharifi, H. Sheikh, A. Alhaji,
Volume 38, Issue 4 (1-2020)
Abstract
The purpose of this study was to evaluate the effect of glycyrol (tri-dentate, GLY) and ethylenediamine (double- dentate clay, en) chelating agents on phase and morphology changes of spinel nanoparticles synthesized by sol-gel method. Characterization of samples was performed by X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray spectrometer (EDX). The results showed that both samples synthesized with GLY and en contain cubic spinel phase. The sample synthesized with ethylenediamine has a pyramidal morphology with particle size in the range of 20-25 nm whereas the specimen prepared with glycerol is spherical with particle size in the range of 20-25 nm. Finally, suggested mechanism for morphological changes of spniel nanoparticles was discussed.
A. Karimian, Kalantar,
Volume 39, Issue 1 (5-2020)
Abstract
In this research, barium calcium hexaferrite (Ba1-xCaxFe12O19 , 0≤x£1) nanoparticles were synthesized through a sol-gel combustion method. The dried gel samples were then calcined at 950ºC for 4:30h. The phase and microstructural evolution of calcined samples were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results revealed formation of calcium -barium hexaferrite phase with a small amount of hematite as a secondary phase. The average particle size is between 60-100 nm and the particle morphology is hexagonal or plate like structure. Results of a vibrating sample magnetometer (VSM) showed that the sample with x=0.4, exhibited the lowest value of saturation magnetization in comparison with others. This could be due to structural heterogeneity and presence of higher amounts of non- magnetic phases (BaFe2O4 and Fe2O3) in this sample compared to others. The results of sensory testing in acetone gas showed that the barium-calcium hexaferrite sample with x=0.2 had the highest sensitivity (0.28) and shortest response (15s) at a concentration of 900 ppm and a temperature of 200 °C despite of the long recovery time.
F. Davar, Z. Enteshari,
Volume 39, Issue 1 (5-2020)
Abstract
In this research, Zinc oxide nanoparticles with semi-spherical morphology were synthesized by modified sol-gel method using rosemary extract as a stabilizing agent. The effect of the amount of rosemary extract and calcination temperature on size and shape of the particles was investigated. The samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and elemental analysis (EDX). X-ray diffraction results showed hexagonal structure (wurtzite phase) of zinc oxide. According to the SEM results semi-spherical nanoparticles of 18 nm in size were obtained using 75 ml of rosemary extract. The photocatalytic activity of the modified ZnO nanoparticles was investigated for degradation of the methylene blue dye solution. The results showed 96.87% of dye degradation in the 135 min that confirmed suitable efficiency of as-synthesized nanoparticles in the photocatalytic degradation process of dyes.
M. Farhadian, K. Raeissi, M. A. Golozar,
Volume 39, Issue 2 (8-2020)
Abstract
This work is focused on the effect of amorphous SiO2 addition on the phase transformation and microstructural evolution of ZrO2 particles. Considering the structural similarities between the amorphous ZrO2 and its tetragonal structure, XRD results showed initial nucleation of metastable tetragonal ZrO2 from its amorphous matrix upon heat treatment. This metastable phase is unstable in pure ZrO2 sample and transforms to a stable monoclinic phase at around 600 oC. However, addition of amorphous SiO2 to ZrO2 structure causes metastable tetragonal phase to remain stable up to around 1100 oC. The temperature range for stability of metastable tetragonal ZrO2 structure increased from about 150 oC in pure ZrO2 particles to around 500 oC in ZrO2-10 mol.% SiO2 composite powders. A further increase in SiO2 content up to 30 mol.% did not change the stabilization temperature range but the average particle size reduced around 1.6 times compared to pure ZrO2 particles. Stabilization of metastable tetragonal ZrO2 explained by constrained effect of SiO2 layer surrounding zirconia nuclei. The thickness of this SiO2 layer enhanced by increasing SiO2 content which limited the growth of ZrO2 nuclei resulting in finer particle sizes.
M. Etminan, M. Morakabati, S. M. Qazi Mir Saeid,
Volume 39, Issue 2 (8-2020)
Abstract
The aim of this study was to investigate the effect of temperature and time of homogenization treatment on the microstructure, distribution of alloying elements and hardness of the novel Co-based superalloy Co-7Al-7W-4Ti-2Ta. For this purpose, the specimens were first homogenized at 1250 and 1300 °C for 2, 4, 6 and 8 hours and then water-cooled. Subsequently, the specimens were subjected to hardness testing and microstructural examinations by optical and electron microscopy. The results showed that by increasing the homogenization temperature to 1300 °C, the porosity created by Ti oxidation and local melting of the Co-Al-Ti eutectic compounds led to a decrease in hardness to 90 Vickers. This phenomenon was due to high segregation of alloying elements in the cast structure. The intensity and destructive effects of this segregation were reduced by remelting of alloy. However, by homogenization at 1250 °C, no local melting of eutectic zones or porosity were observed in the specimens and a more uniform structure was obtained with increasing time. Minimum and maximum hardness values after homogenization at 1250°C were 348 and 406 Vickers, respectively. Moreover, the microstructure became more homogenous by increasing the homogenization treatment time at this temperature.
T. Rajabi, M. Vahedi, S. K. Sadrnezhaad,
Volume 39, Issue 2 (8-2020)
Abstract
Zinc/zinc oxide nanoparticles are used in an increasing number of medical and industrial applications due to their attractive physical, chemical and antibacterial properties. Therefore, achieving a simple and beneficial way to produce them is an important aspect. In this study, zinc/zinc oxide nanopowders were synthesized by fast electric discharges between two electrodes of (a) a spark device in distilled water medium and (b) a handmade high-voltage ignition machine in argon gas medium. The resulting powders were characterized by x-ray diffraction (XRD), dynamic light scattering (DLS) and field emission electron microscopy (FESEM). Using the spark device in distilled water, a mixture of zinc crystals with an average diameter of 11.28 nm and zinc oxide crystals with an average diameter of 22.22 nm was produced. However, using the handmade device in argon, zinc crystals with an average diameter of 7.5 nm were obtained and subsequently oxidized due to their extremely high activity. The production rate of the high voltage discharge method was lower than other conventional methods. On the other hand, its ability in reducing the size and increasing the particle activity was higher than other methods.
A. Ghasemi, M. R. Loghman Estarki, S. Torkian, G. R. Gordani,
Volume 39, Issue 2 (8-2020)
Abstract
The purpose of this study was to evaluate phase changes and magnetic properties of neodymium doped Ni0.7Zn0.3NdxFe2-xO4 (x = 0, 0.01, 0.03, 0.05, 0.07, 0.10) nanoparticles synthesized by complexing sol-gel method. In this method, triethanolamine (TEA) acted as both a gelling agent and a chelating agent. Samples were characterized by X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). XRD patterns of all synthesized samples revealed the formation of a spinel ferrite phase. Magnetic evaluation of the specimens showed that the Nd0.01 doped sample with a quasi-spherical morphology and particle size of about 60 nm has the highest saturation magnetization of 50 emu/g and coercive force of 103 Oe.
A. Zamani, M. R. Loghman Estraki, S. R. Hosseini, M. Ramezani, A. Al-Haji,
Volume 39, Issue 3 (12-2020)
Abstract
The aim of the study was to investigate the effect of temperature, time, pH, capping agent concentration (mercaptoacetic acid), Zn to Se and Se to reducing agent (NaBH4) mole ratios on morphology, phase developments and size of zinc selenide nanoparticles prepared by hydrothermal method. Characterization of zinc selenide nanoparticles was performed by Field Emission Electron Microscopy (FESEM), Energy Dispersive X-ray Spectrometry (EDS), X-ray Diffraction (XRD), Induced Coupled Plasma Spectrometry (ICP), Fourier Transform Infrared spectroscopy (FTIR) and Simultaneous Thermal Analysis (STA). The results of EDS showed that the ratio of atomic percentage of Zn to Se in the optimized zinc selenide nanoparticles is 1: 1 and elements are evenly distributed in the nanoparticles. Based on the results of FTIR and STA thermal analyses, MAA as the stabilizing agent binds to and stabilizes zinc selenide nanoparticles. Finally, fine nanoparticles of zinc selenide with narrow size distribution, spherical shape and cubic crystal structure were obtained at the minimum temperature (130 °C) and processing time (15 hours) with the least amount of reducing and capping agents compared to previous researches.
M. Judaki, M. Seifollahi, S. M. Abbasi, S. M. Ghazi Mir Saeed,
Volume 40, Issue 1 (5-2021)
Abstract
In this article, the effects of Pr and Nd were investigated on the microstructure and absorption/desorption characteristics of MmNi5 hydrogen storage alloy. The alloys were prepared in Vacuum induction furnace and the microstructures and phases were analyzed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). Hydrogen absorption/desorption characteristics was performed on Sievert apparatus. The results showed that the microstructure of the alloys consist of matrix, second phase as a result of Al segregation, porosities and cracks. The amount of second phases and Al in this phase in Mm(Pr,Nd)Ni4.7Al0.3 is less than MmNi4.7Al0.3. Al in Mm(Pr,Nd)Ni4.7Al0.3 were more homogenized. Pressure-Composition Isotherms of hydrogen absorption/desorption at 25˚C showed that for MmNi4.7Al0.3 and Mm(Nd,Pr)Ni4.7Al0.3, absorption pressures were 14.52 and 9.90 bar, desorption pressures were 5.53 and 5.49 bar, hydrogen storage capacities were 1.37 and 1.33 wt. % and hysteresis were 0.73 and 0.58, respectively. These results are useful in industrial applications, because of inconsiderable decrease in hydrogen storage capacity and the other positive variation in absorption/desorption characteristics, especially the hysteresis and absorption pressure.
M. Shayestefar, A. R. Mashreghi, S. Hasani ,
Volume 40, Issue 1 (5-2021)
Abstract
Mn0.8Zn0.2Fe2-xDyxO4 (where x= 0, 0.025, 0.05, 0.075, 0.1) ferrite nanoparticles were synthesized by auto- combustion sol-gel method for the first time in this study. The effect of Dy-doping on the structural and magnetic properties of the produced specimens was examined using the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometery (VSM), and field emission scanning electron microscope (FE-SEM). The results showed that a cubic spinel structure was formed in all of the synthesized specimens. It was also found that the addition of Dy increased the lattice parameter while decreased the average of crystallites size. Furthermore, the FE-SEM micrographs showed that Dy not only plays an effective role in reducing the agglomeration of nanoparticles and their distribution, but also reduces the average of particle size. It was also observed that the addition of Dy had no effect on the morphology of the synthesized nanoparticles. Investigation of the magnetic properties revealed a clear decrease in the saturation magnetization and coercivity by the Dy addition. So that the saturation magnetization of the samples decreased from 66.3 to 58.4 emu/g and the coercivity decreased from 78.5 to 71.9 Oe.
M. Ghorbani, H. Khorsand,
Volume 40, Issue 2 (9-2021)
Abstract
Strontium hexaferrite M-type nanoparticles doped with La and Cu (SrFe12-xCuxO19-Sr1-xLaxFe12-xCuxO19) with different mole fractions (x=0.1-0.2-0.3-0.4-0.5) synthesized by self-combustion sol-gel technique. Firstly, a gel of metal nitrates with the above-mentioned mole fractions were fabricated and the obtained powder was cured at 950°C. Microstructural properties and the morphology of the compounds were investigated by employing X-ray diffraction (XRD) and scanning electron microscopy (SEM). Also, in order to investigate the magnetic properties, Vibrating Sample Magnetometer (VSM) was used. SEM images revealed that the particles had an average size of about 100 nm. Cu2+ ions were substituted with Fe3+ ions within the crystalline sites of SrFe12O19 structure. It was shown that the lattice parameter (a) remained approximately unchanged with an increase in Cu-dopped while the lattice parameter (c) decreased with increasing the mole fraction (x). By using VSM hysteresis diagrams, it was observed that the saturated magnetization and coercive force increased with the addition of La; this was attributed to the variation in the distribution of ions and the shape anisotropy of the nanoparticles. These significant changes in the magnetic properties were for the sample with the composition of Sr1-xLaxFe12-xCuxO19 and SrFe12-xCuxO19, for the x=0.1 and x=0.5, respectively.
F. Fareghdeli, M. Karimi, A. Novin, M. Solati-Hashjin,
Volume 40, Issue 3 (11-2021)
Abstract
One challenge in preparing polymer/ceramic composites is non-uniform ceramic particles distribution in a polymer matrix. This research evaluated the effect of stirring time and temperature on hydroxyapatite (HA) distribution through (polylactic acid) PLA matrix. Therefore, to mix the ceramic suspension with the polymer solution, three temperatures, namely 25, 37, and 45°C and four times including 6, 12, 24 and, 48 h were examined. Fourier-transform infrared spectroscopy (FTIR) analysis was used to investigate the bonds, which showed physical bond formation such as carboxyl-calcium-carboxyl between HA and polymer matrix, influenced on particles distribution. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) were used to observe particles distribution and determine samples homogeneity. To fulfill this goal, each obtained photograph representing the calcium presentation was split into nine equal sections, and a method based on the newly defined index called dispersion factor “α” was used to analyze the distribution. Results showed that the sample prepared at 37°C and 48 h had the topmost homogeneity properties.
A. Azimi-Fouladi , S.a. Hasanzadeh-Tabrizi,
Volume 41, Issue 2 (11-2022)
Abstract
Water pollution is one of the big problems of human societies, and the need to find new ways to remove these pollutants has been given much attention in recent years. One of the methods is the use of photocatalysts. In this research, TiO2 and TiO2-CdO nanoparticles were prepared by a sol-gel method as nano photocatalysts. The produced samples have been used to degrade methylene blue under UV light. To characterize the prepared samples, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray Energy Diffraction Spectroscopy (EDS), and Ultraviolet-Visible Spectroscopy (UV-Vis) were used. Microstructural results revealed nanoparticles with dimensions of 18 to 32 nm. XRD results showed that the main phase formed was the anatase. TiO2-4 wt.% CdO nanocomposite showed more photocatalytic activity compared to pure TiO2. Also, the effect of pH, irradiation time, and amount of powder on photocatalytic activity was investigated. The results showed that at pH=9, time of 75 min, and using 0.02 g TiO2-4 wt.% CdO photocatalyst, the maximum photocatalytic activity of about 92 % was obtained.
