  A novel stearic acid (SA)/3-aminopropyltrethoxysilane (APS) composite
structure was fabricated using the combined method of the Langmuir-Blodgett
technique and self-assembly monolayer (SAM) technique. Its frictional, adhesive
properties and interface contact types between the atomic force microscope tip
and the samples were evaluated based on Amonton's laws and the general
Carpick's transition equation, respectively. The results showed that the
tip-sample contacts corresponded to the
Johnson-Kendall-Robert/Derjaguin-Muller-Toporov (DMT) transition model for
SiO2, APS-SAMs, and the unheated SA-APS composite structure, and for the heated
SA-APS bilayer to the DMT model. Frictional forces for the four samples were
linearly dependent on external loads at higher loads, and at lower loads they
were significantly affected by adhesive forces. Frictional and scratching tests
showed that the heated SA-APS composite structure exhibited the best
lubricating properties and adhesion resistance ability, and its wear resistance
capacity was greatly improved due to the binding-mode conversion from hydrogen
bonds to covalent bonds. Thus, this kind of composite bilayer might be
promising for applications in the lubrication of nano/microelectromechanical
systems. I.
