Fabrication and mechanical characterization of highly preferentially oriented montmorillonite thin films

This paper presents an experimental protocol developed to prepare highly preferentially oriented montmorillonite thin films, and then to probe with nanoindentation their intrinsic mechanical properties (e.g., Young's modulus and hardness). Such highly parallel oriented clay thin films were prepared by dispersing varying amounts of montmorillonite powder (e.g., 1 to 4 g) in deionized water, followed by drying onto silicon wafers. Results indicate that the thin films possess a laminated fabric with a prominent preferred orientation along the basal (00l) plane. Depth-dependent Young’s modulus and hardness were also observed consistently across different specimens. Specifically, Young's modulus and hardness of 4.33 and 0.19 GPa respectively are found at the indentation depth of 100 nm, equivalent to montmorillonite tactoids consisting of ~80 layers of montmorillonite platelets, respectively.