Showing 2 results for Ghamari
M. Ghamari, B. Mirhadi,
Volume 9, Issue 2 (june 2012 2012)
Abstract
Abstract: Glassy samples with xTiO2 .3SiO2 .Na2O composition that (8≤x≤40) (molar) were casted in refractory steel molds after melting at air as parallel palates. After polishing and getting to desire thickness, UV-VIS spectrometry in 200 -1100 nm was measured on samples. Glass density was measured by a sensitive micro balance and was found that by increasing titanium dioxide of glasses, glass density increases. Results from UV-VIS spectroscopy show that increase of titanium dioxide decreases light transmission and this value reaches zero for sample with 40 molar percent of titanium dioxide. One reason of this reduction is formation of crystalline phase in glass, in which, by increasing titanium content crystalline phase will be increased, results of X-ray diffraction and electron microscopy confirm this claim.
M. Ghamari, M. Ghasemifard,
Volume 17, Issue 2 (June 2020)
Abstract
In this research, the dependence of the optical band gap of nano gamma alumina on the OH/Al ratio and concentration of aluminum sulfate is measured through diffuse reflectance spectroscopy (DRS) in the range of 900-1100nm. The samples were prepared via sol-gel method. The results showed that the band gap is pH and concentration-dependent but in a different way. The direct band gap of alumina was determined to be 3.40, 4.37, 3.90, and 3.65 eV for samples prepared at pH 6, 7, 8, and 9, respectively. A decreasing trend was observed with increasing pH (except for pH6). The lowering of the band gap may be associated with the variations in particles size during synthesis due to the quantum size effect. The values of the band gap increased significantly through increasing concentration from 3.90 to 5.65 eV for 0.1M to 0.3M. The role of concentration in band gap control is remarkably more than pH.
