Showing 110 results for Ge
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.
