Showing 5 results for Ramazani
E. Sadri, F. Ashrafizadeh, M. Ramazani,
Volume 32, Issue 2 (Dec 2013)
Abstract
In plasma sprayed nanostructured composite coatings with ceramic matrix, the feedstock must consist of nanoparticles of appropriate specifications. In this research, the procedure for production of Cr2O3-Ag agglomerated nanostructured composite powder to produce comosite coatings has been investigated. Nanopowders of Cr2O3 with 0, 2, 5, and 10 volume percentages of silver were dispersed to obtain a homogeneous aqueous dispersion appropriate for spray drying process. In the second stage, Cr2O3-Ag composite powders were produced by agglomeration process. The nanostructured composite powders were, then, used in the atmospheric plasma spray (APS) process to deposit a series of composite coatings for evaluation. The composite powders, with a granulated morphology, had uniform distribution of silver in a ceramic matrix and the coatings were composed of nanoparticles and particles of nano-sized crystallites. Experimental results indicated that presence of nanoparticle zones within the microstructure led to non-uniform porosities formed between splats and these zones. Furthermore, use of nanopowders in the feedstock caused a reduction in lamellae thickness of plasma sprayed coatings.
M. Fazel, M.r. Garsivaz Jazi1, S. Bahramzadeh, S.r. Bakhshi, M. Ramazani, A. Bahramian,
Volume 34, Issue 1 (Journal of Advanced Materials-Spring 2015)
Abstract
Ni–SiC composite coatings are successfully employed as a protective coating in the inner walls of engine cylinders. In this study, Ni-SiC, Ni-SiC-MoS2 and Ni-SiC-Gr composite coatings were prepared from a sulfamate bath. Both mechanical and ultrasonic stirring were used simultaneously during the process. Taking into account the working temperature of engine cylinders, the wear behavior of coatings was evaluated at 25 to 300 ºC and the high temperature tribological properties of the coatings were investigated. Based on the results obtained from the wear tests, all three coatings showed almost good friction coefficient values at 25 and 100 ºC, which were close to each other. By increasing the temperature to 200-300 °C, the friction coefficient and weight loss values strongly increased. However, addition of solid lubricants caused the values to decrease. The Ni-SiC-Gr coating at all temperatures showed a good and stable behavior.
F. Mohammadi Bodaghabadi, M. R. Loghman Estarki, M. Ramazani, A. Alhaji,
Volume 38, Issue 3 (Journal of Advanced Materials-Fall 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.
F. Dehghani Firoozabadi, A. Ramazani Saadatabadi, A. Asefnejad,
Volume 41, Issue 1 (Journal of Advanced Materials-Spring 2022)
Abstract
Today, many people need to use bone grafts and implants because of damage to bone tissue. Due to the stimulation of the immune system after implantation, infection at the operation site is very common, which causes swelling and pain in the operation area. The use of zinc oxide nanoparticles reduces infection at the operation site and reduces the patient's need for antibiotics. In the present study, the morphology of the scaffolds was investigated by field emission scanning electron microscope (FE-SEM). The toxicity of the samples was evaluated using MTT assay. The behavior of nanocomposites against Escherichia coli and Staphylococcus aureus was investigated by measuring the diameter of the growth inhibition zone. It was found that modification of scaffolds with nanoparticles caused a growth inhibition in bacterial culture medium. It was also observed that fibroblast cells on the surface of the modified scaffolds had longer survival than polymer scaffolds. This study showed that the addition of oxidizing nanoparticles improves the antibacterial properties of scaffolds and cell viability and reduces scaffold toxicity.
R. Zarei, E. Mohammadsharifi, M. R. Loghman, M. Ramazani, Kh. Zamani,
Volume 41, Issue 1 (Journal of Advanced Materials-Spring 2022)
Abstract
The present research has examined the effect of adding Si3N4 on the mechanical and structural properties of NiCrAlY alloy. The structural and mechanical properties of the manufactured samples were characterized by SEM, XRD, micro-hardness evaluation and pin on disk wear test. Various concentrations of Si3N4 powder (1, 3, and 5 wt.%) were mixed with NiCrAlY powder using a mechanical ball mill. Next, the mixtures were sintered at 1100 °C using the spark plasma sintering (SPS) technique. The XRD patterns indicated that the samples were composed of two phases of solid solution γ-Ni(Cr) and intermetallic compounds β-NiAl. The results of micro-hardness measurements showed that adding 1% Si3N4 to NiCrAlY enhanced the hardness from 418 to 614 HV. However, with an increase in the Si3N4 content from 1 to 5 wt%, the hardness diminished from 614 to 543 HV, and by Adding Si3N4 to the NiCrAlY, its tribological properties were significantly improved.
