Crystal lattice imaging of the silica and alumina faces of kaolinite using atomic force microscopy

The crystal lattice images of the two faces of kaolinite (the silica face and the alumina face) have been obtained using contact-mode atomic force microscopy (AFM) under ambient conditions. Lattice resolution images reveal the hexagonal surface lattice of these two faces of kaolinite. Analysis of the silica face of kaolinite showed that the hexagonal surface lattice ring of oxygen atoms had a periodicity of 0.50 ± 0.04 nm between neighboring oxygen atoms, which is in good agreement with the surface lattice structure of the mica basal plane. The center of the hexagonal ring of oxygen atoms is vacant.Analysis of the alumina face of kaolinite showed that the hexagonal surface lattice ring of hydroxyls surround a hydroxyl in the center of the ring. The atomic spacing between neighboring hydroxyls was determined as 0.36 ± 0.04 nm. Ordering of the kaolinite particles for examination of the silica and alumina surfaces was accomplished using different substrates, a procedure previously established. Crystal lattice imaging supports previous results and independently confirms that the two faces of kaolinite have been properly identified.

Graphical abstractCrystal lattice imaging of (A) silica face and (B) alumina face of kaoliniteFigure optionsDownload full-size imageDownload high-quality image (176 K)Download as PowerPoint slideResearch highlights► AFM crystal lattice imaging validates silica and alumina faces of kaolinite. ► Silica face shows hexagonal ring of oxygen atoms with a hole. ► Alumina face shows hexagonal ring of hydroxyls with a central hydroxyl group.