Effect of hydrated ions and wettability on ice friction

Ice friction is a vital phenomenon in both fundamental research and practical applications. However, one unsolved puzzle regarding ice friction is the effect of hydrated ions and wettability on its tribological properties. Here, we report the discovery of the extent of hydrated ions, different surface wettability and their combination on ice friction. By selecting the type and concentration of ions, the coefficients of ice friction were reduced over 70 percent. Experimental spectra, low-field nuclear magnetic resonance (LF-NMR), density functional theory (DFT) calculations, and Molecular dynamics (MD) simulations demonstrated that the addition of ions could break the H-bonds. For negatively charged surfaces, cations play an important role in ice friction. Ionic ice had a lower friction coefficient because of hydration repulsive force and more free water molecules produced by H-bond breaking. Wettability regulates ice friction coefficients by changing the adhesion between water-solids, and hydrophilic surface exhibited stronger adhesion force. Regulation of surface wettability can modulate ice friction by about 20 percent. The effect of regulating wettability to modulate ice friction coefficient is relatively weak comparing with hydrated ions. This study provides guidance for the selection of ions and surface wettability to modulate ice friction.