Nanoscale mechanics and ultralow Friction of natural 2D silicates: Biotite and Rhodonite

TL;DR

This study explores the nanomechanical and frictional properties of natural 2D silicates, Biotite and Rhodonite, revealing their potential for applications requiring ultralow friction and specific mechanical characteristics.

Contribution

It provides the first comparative analysis of the mechanical and tribological behaviors of natural 2D silicates using AFM and DFT calculations.

Findings

Rhodonite has higher adhesion and modulus than Biotite.

Biotite exhibits ultralow friction coefficients (~0.6×10^{-3}).

AFM and DFT reveal structure-property relationships in these silicates.

Abstract

Two-dimensional (2D) silicates have emerged as a promising class of ultrathin materials, expanding the landscape of 2D systems beyond conventional van der Waals crystals. Their unique crystal chemistries and structural anisotropies make them attractive for applications ranging from sensors and flexoelectric devices to drug delivery and catalysis. To unlock their full potential, it is critical to understand their thickness-dependent mechanical properties within the family of 2D silicates. In this study, we investigate the nanomechanical and frictional behaviors of two structurally distinct natural silicates: layered Biotite and chain-structured Rhodonite. Using atomic force microscopy (AFM), we found that Rhodonite exhibits nearly ten times higher adhesion force and modulus response compared to Biotite. Despite this, Biotite demonstrates superior frictional performance, with ultrathin (5 nm) flakes showing a remarkably low coefficient of friction ($\sim 0.6 \times 10^{-3}$) versus Rhodonite ($\sim 3.6 \times 10^{-3}$). To further elucidate interlayer adhesion, density functional theory (DFT) calculations with Hubbard correction were employed. These findings offer valuable insights into the design and selection of 2D silicates for advanced mechanical and tribological applications.