Except for cubic system, most of the crystals have faces with different atomic arrangements, and accordingly these faces might have different surface wettability. However, less attention has been paid to the crystal face related wetting behavior. In the present work, with the contact angle goniometer and atomic force microscopy (AFM) the wettabilities of different crystal faces were studied by measuring the contact angles between several solid-liquid pairs at both macroscopic and microscopic scale. The solid substrates investigated include (001), (100) and (110) faces of a-sapphire and a-quartz, and the liquids are water, glycerol, and phosphoric acid (85 wt%). The results obtained show that the solid-liquid contact angles, which were measured by optical goniometer and AFM, are nearly identical, indicating that both methods are reliable, although optical goniometer measured the contact angle at macroscale and AFM yielded results at nanoscale. For both sapphire and quartz, the contact angles becomes greater on the crystal faces in the order of (001), (110) and (100), although the differences in contact angle between different faces of sapphire are less than those of quartz. Moreover, among the three liquids tested, the contact angles of phosphoric acid on different faces changes the most.

Wettabilities of different faces of the same crystal

254th National Meeting (2017)

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