Showing 2 results for Sol-Gel.
M. Farhadian, K. Raeissi, M. A. Golozar,
Volume 39, Issue 2 (8-2020)
Abstract
This work is focused on the effect of amorphous SiO2 addition on the phase transformation and microstructural evolution of ZrO2 particles. Considering the structural similarities between the amorphous ZrO2 and its tetragonal structure, XRD results showed initial nucleation of metastable tetragonal ZrO2 from its amorphous matrix upon heat treatment. This metastable phase is unstable in pure ZrO2 sample and transforms to a stable monoclinic phase at around 600 oC. However, addition of amorphous SiO2 to ZrO2 structure causes metastable tetragonal phase to remain stable up to around 1100 oC. The temperature range for stability of metastable tetragonal ZrO2 structure increased from about 150 oC in pure ZrO2 particles to around 500 oC in ZrO2-10 mol.% SiO2 composite powders. A further increase in SiO2 content up to 30 mol.% did not change the stabilization temperature range but the average particle size reduced around 1.6 times compared to pure ZrO2 particles. Stabilization of metastable tetragonal ZrO2 explained by constrained effect of SiO2 layer surrounding zirconia nuclei. The thickness of this SiO2 layer enhanced by increasing SiO2 content which limited the growth of ZrO2 nuclei resulting in finer particle sizes.
A. Azimi-Fouladi , S.a. Hasanzadeh-Tabrizi,
Volume 41, Issue 2 (11-2022)
Abstract
Water pollution is one of the big problems of human societies, and the need to find new ways to remove these pollutants has been given much attention in recent years. One of the methods is the use of photocatalysts. In this research, TiO2 and TiO2-CdO nanoparticles were prepared by a sol-gel method as nano photocatalysts. The produced samples have been used to degrade methylene blue under UV light. To characterize the prepared samples, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray Energy Diffraction Spectroscopy (EDS), and Ultraviolet-Visible Spectroscopy (UV-Vis) were used. Microstructural results revealed nanoparticles with dimensions of 18 to 32 nm. XRD results showed that the main phase formed was the anatase. TiO2-4 wt.% CdO nanocomposite showed more photocatalytic activity compared to pure TiO2. Also, the effect of pH, irradiation time, and amount of powder on photocatalytic activity was investigated. The results showed that at pH=9, time of 75 min, and using 0.02 g TiO2-4 wt.% CdO photocatalyst, the maximum photocatalytic activity of about 92 % was obtained.
