Crack-free alumina hard coatings through a sol-gel method

• Main Author: Chen, Ruixi
• Other Authors: Huang Yizhong
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/66989
• Institution: Nanyang Technological University

Alumina has been used as a coating material in industry for decades, due to its superior corrosion resistance and excellent wear resistance. Previous researches introduced different deposition methods for alumina coatings, including ion beam reactive sputtering [1], electron beam evaporation deposition and high power impulse magnetron sputtering[2]. Compared with these coating methods that require expensive equipment, the sol-gel method offers a much simpler and cheaper route for large scale and crack-free alumina coatings. This project investigated three different precursor solutions (Al(NO3)3·9H2O in acetylacetone, Al(NO3)3·9H2O in ethylene glycol, and aluminium hydroxide colloids in water) for the sol-gel process, in order to obtain crack-free alumina films on indium doped tin oxide (ITO) glass. Experiments showed both acetylacetone (acac)-based Al(NO3)3·9H2O solution and ethylene glycol (EG)-based Al(NO3)3·9H2O solution were capable to fabricate crack-free alumina films on ITO glass, as evidenced by scanning electron microscope observation. In comparison, the conventional way to deposit alumina films with aluminium hydroxide colloids was not suitable for crack-free high quality alumina films, as the particle size of the aluminium hydroxide in the colloids is around 500 nm. The hardness of those coated ITO glass samples is improved by around 11% compare to those samples without alumina coatings (bare ITO), indicating the effectiveness of the sol-gel process using EG and acac-based Al(NO3)3·9H2O solutions.