Mechanism for the effects of surface chemical composition and crystal face on the wettability of α-quartz surface

Abstract

Quartz is a ubiquitous matter in natural rock and industrial production, and the wetting property of quartz surface plays a critical role in determining numerous industrial processes. However, the key mechanism for the effects of surface chemical composition (based on surface pretreatment) and crystal face on the wettability of quartz surface remains vague. Herein, by applying an advanced atomic force microscopy (AFM), we measured the contact angles of liquids on three common crystal faces of α-quartz after different pretreatments. The time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis and molecular dynamics (MD) simulations were further conducted to uncover the microscopic mechanism involved. It is found that the surface pretreatment does significantly affect the wettability of α-quartz faces, mainly because of the variation in surface hydroxyl concentration after different surface pretreatments. The magnitude of change in contact angle after distinct pretreatments is also affected by the liquid property. After certain pretreatments, although there is no difference in the wettability of different faces, the inherent atomic arrangement of crystal faces still causes discrepancies in other interface properties, e.g., liquid structure, diffusion coefficient of liquid molecule. The reasonable pretreatments of α-quartz for a range of applications are recommended based on the current findings.