Dr M. Tavoosi, S. Arjmand,
Volume 37, Issue 1 (6-2018)
Abstract
In this study, the formation of the Al3Ti intermetallic compound at the junction interface of aluminum-titanium was investigated during deposition and annealing. The results illustrated that during the deposition process, one thin layer of Ti3Al2 intermetallic compound was created at the junction interface. During the annealing at 550 °C, this layer was transformed to the Al3Ti intermetallic phase and the layer growth occurred. By performing annealing at higher temperatures, the growth rate of Al3Ti intermetallic layer was increased; at the same time, the formation of Kirkendall cavities and coupling in the cavities and fragmentation of diffusional coupling from the junction with aluminum were observed
A. R. Parvanian, H. R. Salimijazi, M. H. Fathi,
Volume 38, Issue 4 (1-2020)
Abstract
The concentrated solar power (CSP) is one of the renewable energy sources in which solar irradiation heat energy will be used in a steam turbine to generate electrical grid. Solar radiation is absorbed by a solar receiver reactor on the surface of a porous solar absorber. In this survey, synthesis and mechanical/thermal characterization of micro-porous silicon carbide (SiC) absorber to be used in solar reactor is carried out. SiC foams were synthesized and categorized based on three different pore sizes i.e. 5, 12 and 75 ppi. Mechanical behavior and thermal shock resistance of porous foams in the working temperature range for absorber (25-1200 °C) were evaluated. Results revealed that the specific compressive strength (σc/ρ) of foams increase exponentially by a decrement in the porosity percentage and the average pore size. Moreover, for foams with smaller pore size, a considerable decrease in mechanical strength due to thermal shock was observed. This could be due to increase in the number of struts per unit volume i.e. more weak struts to withstand the mechanical loading. So, porous foams with coarser pore sizes were distinguished to be more capable of tolerating thermal shock while serving as solar absorbers.
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.
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.
Z. Rezay Marand, A. Kermanpur, F. Karimzadeh,
Volume 40, Issue 3 (11-2021)
Abstract
Increased demand for clean energy sources, solar cell technology is expanding rapidly. One of the most critical challenges in constructing perovskite solar cells is the lack of an effective hole transport layer with stability and reasonable price. Inorganic p-type semiconductors such as nickel oxide are very cost-effective compared to organic ones. Features such as wide energy gap, high conductivity, stability and resistance to moisture, and solution-based manufacturing process, make the nanostructured inorganic hole transport layer a viable alternative to organic materials. The purpose of this project was to evaluate the characteristics and mechanism of nickel oxide as a hole transport material and fullerene as an interlayer in the structure of inverted nanostructured perovskite solar cells. These solar cells obtained a fill factor of about 71%, a current density of 21.5 mA/cm2, an open-circuit voltage of 1000 mV, and an efficiency of 15.2%.
A. Mohammadi, B. Niroumand, A. Saboori,
Volume 40, Issue 4 (3-2022)
Abstract
Electron beam melting (EBM) is among the modern additive manufacturing processes whereby metal powders are selectively melted to produce very complicated components with superior mechanical properties. In this study, microstructure, hardness, and surface roughness of EBM fabricated Ti6Al4V samples were characterized. The results showed that the microstructure consisted of epitaxially-grown primary columnar β phase transformed to basketweave and Widmanstatten-type α phase during the subsequent rapid cooling. Martensitic needle-type α phase was also observed on the surfaces of the specimens. It was shown that higher parts of the sample had finer microstructures than the lower parts reaching to less than 340 nm in average thickness of the α layers due to distancing from the hot build platform rendering less opportunity for diffusional β → α+β transformation. The porosity content of the samples was lower than that of some other additive manufacturing processes. Vickers micro-hardness of the samples was measured to be around 337 HV which was higher than those reported for other additive manufacturing processes of the alloy.
A. Mehdikhani, H. Fallah-Arani, F. Dabir, A. Ghanbari,
Volume 41, Issue 2 (11-2022)
Abstract
In this research, the effect of hydrogen peroxide (H2O2) and benzoyl peroxide (BPO) on the structural properties, porosity, active pores, and surface area of the MOF-5 (Zn4O(BDC)3) metal-organic framework was studied. For this purpose, the metal-organic framework was synthesized by direct mixing and the molar ratios of the precursors to the ligand were modified to minimize the stoichiometric calculation error as well as the washing process to improve the properties of the synthesized MOF-5. In order to characterize the synthesized compounds and to investigate the effect of peroxides and washing process on the properties of the samples, X-ray diffraction (XRD), fourier Transform infrared spectroscopy (FTIR), and thermogravimetric/Differential scanning calorimetry (TG-DSC) analysis were performed. Structure, pore volume (1.212 cm3/g), and specific surface area (2307 m2/g) were compared to the sample synthesized with H2O2. DM-P-03 was selected as the optimal sample and prepared for thermal stability. According to TG-DSC analysis, the remaining zinc compounds in the sample were checked and the thermal stability of MOF-5 structure was confirmed up to 470°C.
