Friction and chemical action of deionized water on microscopic wear of sapphire surface

Nano wear testing of C-directional single crystal sapphire was conducted using atomic force microscopy in deionized water. The friction and chemical action of deionized water on the micro wear of sapphire was studied by comparing it with the anhydrous ethanol environment. The experimental results indicate that deionized water has both positive and inhibitory action on the micro wear of sapphire materials. It is closely related to the sliding speed of the probe tip. In the low sliding speed range, deionized water has a negative influence on the surface wear of sapphire. When the sliding speed reaches 4 μm/s, the average wear depth of sapphire surface in deionized water is significantly improved. In addition, the influence of cycles on micro wear of sapphire surface is not related to the liquid environment of the contact interface. When the load is 0.24, 0.96, and 2.40 μN, the surface wear depth of sapphire in deionized water is 128 %, 48 %, and 35 % higher than that in anhydrous ethanol, respectively. The promoting effect of deionized water on the removal of sapphire is attributed to the Si-O-Al bridge bond formed between the silicon tip and the substrate. Besides, the soluble substance (Al(OH)₄^-) is generated by the reaction between the sapphire surface and water. The research results can provide reference for understanding the mechanical and chemical wear of sapphire.