Showing 2 results for Marashi
Kaviani S., Marashi S. P. H.,
Volume 1, Issue 3 (Apr 2004)
Abstract
The surface condition and microstructure of near stoichiometric (Fe823Ndll.8B5.9) Nd-Fe-B alloy ribbons and the effect of melt spinning parameters were investigated using optical, scanning and transmission electron microscopes (SEM, TEM). The formation of gas pockets on the roll surface of the ribbons during melt spinning can prevent heat transform and result in local coarse grains. The local thickness would also be less in these places and thus perforates preferentially during ion beam milling. Therefore different areas of the sample should be carefully observed in the TEM. Reducing inert gas pressure in the chamber will eliminate the gas pockets. As a general trend, decrease in the ribbon thickness and mean Nd2 Fe14B grain size were observed on increasing the roll speed. By careful adjustment of the melt spinning parameters, the nanostructure will develop. An orientation relationship was found between Nd2 Fe14B and α-Fe precipitates for coarse grain samples melt spun at low roll speed. Dark field image of such grain also shows that some of these α-Fe precipitates have the same orientation. X-ray diffraction evident the development of texture by decreasing the roll speed.
M. R. Ghaani, P. Marashi,
Volume 15, Issue 3 (September 2018)
Abstract
Na super ionic conductive (NASICON) materials are ceramics with three-dimensional scaffolds. In this study, Li1.4Al0.4Ti1.6(PO4)3 with NASICON structure was synthesized by Pechini method. As a result, a sample having a total conduction of 1.18×10-3 S cm-1 was attained. In addition, various parameters were studied to obtain high value of conductivity, by optimizing the process. The optimization was made using L16 Taguchi based orthogonal array, followed by ANOM, ANOVA and stepwise regression. As a result, the optimum synthesis parameters can be obtained, while pH of the solution was adjusted to 7. The ratio between the concentration of citric acid to metal ions and ethylene glycol concentration stuck to 1 and 2.5, respectively. The best heat treatment can be carried out with a combination of pyrolysis at 600 ºC and sintering at 1000 ºC.
