The Influence of Gel Preparation and Thermal Treatment on the Optical Properties of SiO2-ZnO Powders Obtained by Sol–Gel Method

Abstract

The effect of gel preparation and heat treatment on the structural and optical properties of SiO2-ZnO materials prepared by the sol–gel method was investigated. Zinc acetate dehydrate, TEOS (tetraethylortosilicate), ethanol, distillated water and HCl were used as a starting material, solvent and catalyst, respectively. Four powders (G1–G4) were prepared in different ways from the starting materials mentioned above. The method of adding Zn precursors during the synthesis differed from one another. For the G1 synthesis, only Zn acetate powder was employed; for the G2 synthesis, Zn acetate was dissolved in distilled water; and for the G3 synthesis, Zn acetate was dissolved in ethanol. When synthesizing G4, TEOS was added last, after Zn acetate had been combined with water and ethanol. The SiO2-ZnO materials were dried at 200 °C and then heat-treated at 700 °C and 900 °C. All samples were investigated by X-ray diffraction and infrared spectroscopy in order to investigate their structure. SEM measurements were performed to investigate the morphology of materials. Optical properties were influenced by gel preparation and heat treatments. A reflectance of over 60% was obtained for G3 and G4 powders, while for G1 and G2, the reflectance was below 30%. In conclusion, synthesis steps and heat treatment can control the structure and properties of the powders.

Effect of Thermal Treatment on the Structure and Morphology of Vanadium Doped ZnO Nanostructures Obtained by Microwave Assisted Sol–Gel Method

“…Figure 2 shows the FTIR spectra of the V doped ZnO gels obtained by the microwave assisted sol–gel method (MW) and the classic sol–gel method (SG). The bands in the 3600–2000 cm −1 region corresponded to the vibration mode of the organic groups such as the CH 3 , CH 2 as well as OH group from alcohols [ 37 , 38 , 39 , 40 , 41 ]; these overlapped into a wide band identified in the FTIR spectra of gels. Two bands at 1419 cm −1 and 1570 cm −1 were assigned to symmetric and asymmetric stretching of the C=O bond in the acetate group.…”

“…The bands at 1045 cm −1 and 1070 cm −1 were characteristic to the symmetric and asymmetric stretching modes of the C–O bond in the acetate group. Below 677 cm −1 , bands could be seen due to the Zn–O vibration [ 37 , 38 , 39 , 40 , 41 ]. In the spectra of the samples, the Zn–OH band was observed at 677 cm −1 , and the bands at 502 and 445 cm −1 were attributed to Zn–O vibration.…”

Fabrication of High-Resolution Fine Microneedles Derived from Hydrolyzed Hyaluronic Acid Gels in Vacuum Environment Imprinting Using Water Permeable Mold

“…Figure 6 shows (a) the chemical structures of the water permeable surface material and (b) hydrolyzed hyaluronic acid as a raw material of fine microneedles. The water permeable surface materials with four components, 40 wt% 3-(acryloyloxy)propyltrimethoxysilane, 35 wt% methyltrimethoxysilane, 15 wt% tetraethyl titanate, and 10 wt% tetraethoxysilane, were prepared using the sol–gel polymerization [ 36 , 37 , 38 ]. The polymerized water permeable surface materials with an average molecular weight of 5500 relative to a polystyrene standard were measured using gel permeation chromatography (GPC, EcoSEC Elite HLC-8420GPC, Tosoh, Japan).…”

Hydrophobic and Transparent Tantalum Pentoxide-Based Coatings for Photovoltaic (PV) Solar Panels

“…The band gap and the refractive index were correlated with the zinc oxide amount in the film. The good effect of zinc oxide can be observed in the properties of other nanomaterials and glasses used as semiconductors [34,41].…”