Showing 14 results for Magnesium
M. Reza Afshar, M. R. Aboutalebi, M. Isac, R.i.l. Guthrie,
Volume 28, Issue 1 (6-2009)
Abstract
In this research, a 3-D mathematical model is developed for simulating electromagnetic continuous removal of inclusions from molten metals. The model includes the computation of electromagnetic force field and fluid flow in the presence of electromagnetic forces. The results of flow field together with electromagnetic force field were further used for calculating the trajectory of inclusions in the molten metal. Parametric studies were performed to evaluate the effects of various parameters such as magnetic field intensity, inclusion size, and fluid velocity on inclusion removal efficiency in molten magnesium. In order to verify the mathematical model and visualize the trajectories of particles in the melt flow under electromagnetic force, a physical model was constructed. The predicted particle trajectories and separation in the physical model were compared with those obtained from experiments, which showed a relatively good agreement.
M. Ashuri, F. Moztarzadeh, N. Nezafati, A. Ansari Hamedani, M. R. Tahriri,
Volume 31, Issue 1 (6-2012)
Abstract
In the present study, a bioceramic-based composite with remarkable mechanical properties and in vitro apatite forming ability was synthesized by sintering compacts made up of mixtures of hydroxyapatite (HA) and sol-gel derived bioactive glass (64SiO2-26CaO-5MgO-5ZnO) (based on mole %). HA was synthesized through co-precipitation method. The stabilization temperature of the bioactive glass was set to be 700 ºC according to simultaneous thermal analysis (STA). Laser Particle Size Analysis (LPSA) was used to compare the particle size distributions of the synthetic powders. HA matrix was mixed with different weight percentages of bioactive glass (5, 10, 15, 20, 25 and 30 wt. %) and compressed by 80 MPa pressure. After sintering the uniaxial compression test of the samples was done and the specimen with the highest compressive strength (20 wt. % bioactive glass) was selected to be immersed in the Simulated Body Fluid (SBF) for 3, 7 and 14 days. The results showed that the compressive strength of the sample decreased after keeping it in the SBF. Also, inductively coupled plasma analysis (ICP) was used to study the ion release behavior of the sample in the SBF. Finally, phase composition, microstructure and functional groups in the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infra-red spectroscopy (FTIR) techniques, respectively.
Kh. Biralvand, M.h. Abbasi, A. Saidi,
Volume 31, Issue 1 (6-2012)
Abstract
Carbothermic reduction of Molybdenite in the presence of Magnesium oxide was thermodynamically studied. The stability diagrams for MoS2-MgO and MoS2-MgO-C Systems was prepared. The reduction of MoS2 with Carbon in the presence of Magnesium oxide proceeded through the direct oxidation of MoS2 by MgO to form intermediate molybdenum oxidized Species, MoO2 and MgMoO4. The results showed that the gaseous phase is mainly composed of CO. Stability diagrams for Mo-O-C (Reduction of MoO2 with carbon) and Mo-Mg-C-S-O (Reduction of MgMoO4 with carbon) were also investigated. The results showed that the Reduction of oxidized species leads to the formation of Mo, Mo2C, MoC or MgO products.
S. Otroj, F. Mohammadi, M.r. Nilforushan,
Volume 33, Issue 1 (7-2014)
Abstract
In this paper, the effect of MgCl2 addition on the kinetics of MA spinel formation was investigated. For this purpose, the stoichiometric mixture of MgCO3 and calcined aluminum was calcined at 1100 °C for 1 hr. Then, the calcined composition was wet-milled and after addition of 6% MgCl2 the compositions were pressed and fired at 1300 and 1500 °C for different times. Spinel phase content was determined using semi-quantitative phase analysis. With regard to Jander's equation, the rate constant was calculated, and the activation energy was obtained from Arrhenius equation. The results showed that the addition of MgCl2 leads to the acceleration of the spinel formation reaction. Besides, 55.71 Kcal/mol as the activation energy was calculated for the composition containing 6 wt.% MgCl2 compared with 93.06 Kcal/mol for the composition without MgCl2.
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.
M. Rajabi, R. A. Sedighi , S. M. Rabiee,
Volume 34, Issue 2 (7-2015)
Abstract
In this study, the effect of mechanical alloying on the microstructure and phase constituents of Mg-6Al-1Zn-1Si system was investigated. To understand the thermal behavior, isothermal annealing was performed at three different temperatures of 350, 400 and 450 °C for 1h. The results showed the grain size initially decreases with increasing the milling time up to 35h and then slightly increases. In contrast, the lattice strain increases sharply with increasing the milling time up to 35h and then decreases. Second-phase intermetallic particle Mg2Si was produced during annealing and the amount of this phase was increased with increasing annealing temperature. The mechanical alloying process decreased the formation temperature of Mg2Si.
M. Jafarian, M. Paidar, M. Jafarian,
Volume 35, Issue 1 (6-2016)
Abstract
In this study, microstructure and mechanical properties of diffusion joints between 5754, 6061 and 7039 aluminum alloys and AZ31 magnesium alloy were investigated. Diffusion joints were done between the alloys at 440 °C, for duration of 60minutes, at 29 MPa pressure and under 1×10-4 torr vacuum. The interface of joints was studied using optical (OM) and scanning electron microscopy (SEM) equipped with EDS analysis and the line scan. According to the results of EDS analysis, the presence of intermetallic compounds including Al12Mg17, Al3Mg2 and their mixture was observed at the diffusion zone. Also, according to the results of the line scan, the hardness value of aluminum alloys has a considerable effect on diffusion of the magnesium atoms toward aluminum alloy and the greatest diffusion of magnesium was observed when 6061 aluminum alloy was used. More diffusion resulted in a stronger bond between atoms of magnesium and aluminum, and maximum strength of approximately 42 MPa was obtained when 6061 aluminum alloy was used.
M. Soltani, B. Niroumand, M. Shamanian,
Volume 36, Issue 2 (9-2017)
Abstract
In this paper, the optimization of the surface composite of Mg AZ31B-carbon nanotub(CNT) via friction stir processing was investigated. Then, the most effective process parameters such as transverse speed, rotational speed, CNT weight percent and welding passes were studied by Response Surface Methodology (RSM) design of experiment. The specimens were also characterized by micro-hardness, tensile, shear punch and pin on disk dry sliding wear tests. The optimization results of hardness and weight reduction responses showed that the best conditions would be achievable with a transverse speed of 24 mm/min, rotational speed of 660 rpm, 4wt.% CNT and 3 welding passes. Moreover, fracture analysis of the surfaces proved a uniform distribution of CNTs in the matrix resulted in higher tensile and shear strength.
S. Yousefi, B. Ghasemi, M. Tajalli, A. Asghari,
Volume 36, Issue 4 (3-2018)
Abstract
In this paper, high purity magnesium hydroxide nanoplates were successfully synthesized by using brine rich in magnesium ions as precursor and NaOH as precipitating agent without using dispersant agent in the room temoerature. The study and characterization of various properties of obtained nanopowder was carried out by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Fluorescence Spectrometer (EDX), Fourier Transform Infrared Spectrophotometer (FTIR) and Ultraviolet–visible spectroscopy (UV-Vis). The FESEM and XRD analysis results showed that magnesium hydroxide powder had nanoplates with the average crystallite size 17.1nm and no impurity; that was in agreement with the result of EDX and FTIR perfectly. Furthermore, optical characteristics of magnesium hydroxide nanoplates by UV-Vis spectroscopy showed an optical band gap of 5.5 eV. This wide band gap can be a useful innovation in optoelectronic sub-micron devices.
S. Ghadiri, A. Hassanzadeh-Tabrizi,
Volume 37, Issue 1 (6-2018)
Abstract
In this study, the synthesis of nano-porous calcium magnesium silicate was performed and studied to improve drug properties and drug release. This synthesis was carried out by using the tetraethyl ortho silicate precursor (TEOS) and the Cetyltrimethyl ammonium bromide surfactant (CTAB) in a sol-gel alkaline environment; and the product was heat treated at 600° C and 800° C temperatures. The purpose of this study is to investigate the effect of the calcination temperature on the potential for ibuprofen release by the production produced compound. The product was studied using X-ray diffraction patterns (XRD), Nitrogen adsorption / desorption, Fourier-transform infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV) and Transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The results of Nitrogen absorption-desorption assay showed a surface area of 42-140 m2 /g The drug release after 240 hours showed that the calcite sample had a lower release at 600 ° C, temperature that which was is due to the smaller size of the cavities and the more surface area, as compared tothan the other specimens. Also, calcium and magnesium elements increased the loading capacity, and createcreating a suitable substrate for for the slower drug release. Overall, This this study showed that nano-porous magnesium silicate calcium has had the ability to load and release the ibuprofen and can could be, therefore, used as a modern drug delivery system in the bone tissue engineering field.
B. Pourbahari, H. Mirzadeh, M. Emamy,
Volume 37, Issue 4 (3-2019)
Abstract
Microstructural evolutions during the high-temperature annealing of Mg alloys containing Al and Gd and after the extrusion process were evaluated and compared to those of the AZ61 alloy. It was revealed that during exposure at the elevated temperatures, the presence of (Mg,Al)3Gd phase, in the form of fine and dispersed particles in the matrix after the extrusion process, could be favorable for the inhibition of grain growth. It was also found that the Al2Gd particles could not effectively retard the coarsening of grains. On the other hand, the grain growth of AZ61 alloy was found to be problematic, which was related to the dissolution of the Mg17Al12 intermetallic phase at temperatures higher than 300°C. In the Mg alloys containing both Al and Gd elements, the increased thermal stability was observed, which was ascribed to the rise of the melting temperature. Finally, some abnormal grain growth was observed in the presence of Al2Gd phase, which was attributed to the nonuniform pinning of grain boundaries by this intermetallic compound.
N. Safari, M. Toroghinejad, M. Kharaziha, V. Saeedi,
Volume 38, Issue 3 (12-2019)
Abstract
The aim of this study was to fabricate the Mg-1Al-Cu alloys with various amounts of Cu content (0, 0.25, 0.5 and 1 wt.%) using spark plasma sintering (SPS) approach and evaluation of their degradation rate and biological properties. The results indicated that Cu incorporation (0.25 wt.%) significantly diminish degradation rate from 0.039 cm/h in pure Mg to 0.00584 cm/h in Mg-1Al-0.25Cu alloy. In addition, Mg-1Al-0.25Cu alloy could noticeably (1.25 times) promote viability of MG63 cells compared to pure Mg, owing to the optimized ion release. Moreover, the antibacterial activity of Mg-1Al-0.25Cu was considerable. In summary, Mg-1Al-0.25Cu alloy with appropriate degradation rate, good biocompatibility and antibacterial properties can be introduced as a biodegradable orthopedic implant.
M. Toorani Farani,
Volume 39, Issue 1 (5-2020)
Abstract
In this study, Plasma Electrolytic Oxidation (PEO) at three frequencies of 500, 1000 and 3000 Hz was applied on Mg surface and the effect of PEO surface preparation on protective behavior of three types of epoxy, fusion bond epoxy (FBE) and polyurethane coatings was investigated. The microstructural and protective properties of PEO coatings were studied by SEM, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the coating formed at frequency of 3000 Hz had smaller pore size and better protection properties. EIS test in 3.5 Wt.% NaCl solution was also used to investigate the protective behavior of the two-layered coatings. The results showed that PEO process had a favorable effect on the protective behavior of the polymer layers. Moreover, the best protection behavior was related to the PEO/FBE coating system.
M. Soltani, A. Seifoddini, S. Hasani,
Volume 39, Issue 1 (5-2020)
Abstract
In this research, the effect of heating rate on oxidation kinetics of magnesium powder particles under non-isothermal conditions was studied. For this purpose, differential thermal analysis (DTA) and thermogravimetry analysis (TGA) was done on magnesium powder particles at three heating rates of 5, 10 and 20 K min-1 up to 1000 °C under air atmosphere. Also, in order to better understand the oxidation process of magnesium powder, three temperatures were selected according to the DTA curve at a heating rate of 20 K min-1. Then, samples of magnesium powder were heated up to these three temperatures with heating rate of 20 K min-1 and were subjected to X-ray diffraction (XRD) and scanning electron microscopy (SEM) for phase and microstructural analysis. Then, kinetic studies were performed using some isoconversional methods such as Starink and Friedman as well as direct and indirect fitting methods. The activation energy (E) and pre-exponential factor (lnA) for oxidation of magnesium powder were in the range of 327-956 kJ mol-1 and 45-135 min-1, respectively. The reaction models for heating rates of 5, 10 and 20 K min-1 were obtained to be A3/2, R2 and D1, respectively.
