Influence of Glycerol Additive on the Chemical Structure, Hydrophobicity, Morphology and Optical Properties of Sol-gel Based Zirconia Coatings
Abstract
This work represents the influence of glycerol additive on the chemical structure, hydrophobicity, morphology and optical properties of the sol-gel based zirconia coatings. Drying control chemical additives (DCCAs) are found to sustain the porous structure of the materials reducing the risk of cracking. Amongst various DCCAs like oxalic acid, glycerol (GLY), formamide etc., GLY is observed to be an effective DCCA because of its low vapour pressure (2.13 x 10-6 at 20oC). Therefore, the effect of GLY additive on the properties of zirconia coatings has been studied by varying the molar ratio of GLY:Zr4+ from 0 to 2.15. During the sol-gel process the molar ratio of ZrPro: PrOH: Acac: H2O was kept constant for 1:79.8:0.615:35.08 respectively with 0.1 M HCl. The FTIR and XPS analyses revealed that the coating material is of zirconia. SEM images manifested the porous morphology of the zirconia coatings having the optical transmission larger than 90%. Moreover, the porous nature of the zirconia coatings was confirmed by calculating their refractive indices. The zirconia coatings synthesized using the GLY:Zr4+ molar ratio of 0.429 exhibited the high contact angel of 108o and low refractive index of 1.66 which evident their optically transparent and hydrophobic characteristics.
