On the Ionic Liquid Film ‘Pinned’ by Core-Shell Structured Fe3O4@Carbon Nanoparticles and Their Tribological Properties

• A strongly ‘pinned’ ionic liquid (IL, [BMIM][PF6]) film onto silicon (Si) surface via carbon capsuled Fe3O4 core-shell (Fe3O4@C) nanoparticles is achieved, revealing excellent friction-reducing ability at a high load. The adhesion force is measured as ~ 198 nN at the Fe3O4@C-Si interface by Fe3O4@C colloidal AFM tip, which is stronger than that at both Fe3O4@C-Fe3O4@C (~ 60 nN) and IL-Si (~ 10 nN) interfaces, indicating a strong ‘normal pin-force’ towards the Si substrate. The resulting strengthened force enables the formation of lateral IL networks via the dipole-dipole attractions among Fe3O4 cores. The observed blue shift of the characteristic band related to the IL anion in ATR-FTIR spectra confirmed the enhanced interaction. The N-Si, P-O chemical bonds formed as a result of the IL interactions with the Si substrate confirmed by XPS spectroscopy suggested that the IL lay on the Si plane. This orientation is favorable for Fe3O4@C nanoparticles to exert ‘normal pin-force’ and press the IL film strongly onto surfaces. The IL ios/clusters are thus anchored by these Fe3O4@C ‘pins’ onto the substrate to form a dense film, resulting in a smaller interaction size parameter, which is responsible for the reduced friction coefficient μ.

Subject headings

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Keyword

Chemistry of Interfaces

Gränsytors kemi

Publication and Content Type

ref (subject category)

art (subject category)