Liquid-phase deposition of Al₂O₃ coating on quartz fiber for enhanced strength at elevated temperature

In the manuscript, the liquid-phase deposition technique was used to successfully deposit an Al₂O₃ ceramic coating on the quartz fiber. The thickness of the coating was not uniform. The thickest part of the coating can reach to 1159 nm. The main coating formed is Al₂O₃, but there are still hydrous Al(OH)₃. With the extension of the deposition time, the micro-morphology of the coating changed from nano-scale clusters to dense flakes. The coating had an amorphous structure. In this case, the coating effectively improved the mechanical properties of the quartz fiber at high temperatures, and the breaking load of the fiber increased with the extension of the deposition time. After high temperature annealing, the breaking load of the coated fiber deposited for 6 h was 126.1 N, compared to 50.3 N of the blank fiber. The protection mechanism of Al₂O₃ coating was studied from the aspect of microstructure. By observing the surface morphologies of blank fiber and coated fiber after high temperature annealing. It was found that the presence of the coating hindered the damage of the fiber surface by high temperature, and the defects on the fiber surface were reduced, so the mechanical properties were effectively improved.