Influence of water vapor on nanotribology studied by friction force microscopy

Abstract

To simulate the nanotribological effects of adsorbed water molecules and the capillary condensation of water around contacting asperities, we have studied the friction and adhesive forces acting on the tip of a friction force microscope in contact with a flat surface as function of humidity. On the hydrophilic surface of silicon oxide strong capillary formation occurs around the tip. In contrast, on the hydrophobic surface of silicon oxide covered with a perfluoropolyether lubricant, the water capillary formation around the tip is greatly suppressed. Friction and adhesive forces decrease substantially with increasing humidity during sliding of the tip across both sample surfaces, implying that the surfaces are lubricated by adsorbed water.

Compositional dependence of the microscopic frictional properties of single crystal metal carbides

“…As previously mentioned, friction properties can be strongly influenced by water vapor through condensation at contacting asperities [10,11,14]. The results presented in figures 3 and 5 illustrate that condensation of water vapor with increasing relative humidity results in an increase in the frictional response for all three carbide samples.…”

“…The condensation of water vapor at contacting asperities is a common physical phenomenon and can dramatically influence the tribological properties of sliding solid-solid contacts [10,14]. Figure 3 presents the friction-load plots of TiC(100), Ti 0.3 V 0.6 C(100), and VC(100) obtained under these conditions as a function of decreasing applied load.…”

“…The frictional properties were measured under dry nitrogen conditions and further investigated as a function of relative humidity in order to investigate the tribological behavior of these materials in the presence of condensed water vapor [10,11]. Careful calibrations of normal and lateral forces in this study have allowed the quantitative determination of a microscopic friction coefficient for these materials.…”

Influence of atmosphere humidity on tribological properties in scanning probe microscope observation

“…The interaction forces between the tip-sample surfaces are more complicated than the meniscus force. One reported explanation was that the chemical potential of the water in the tip-sample gap changes, and the force from water becomes less attractive with increasing relative humidity [13].…”

“…It is important to evaluate the extent of the effects, because the imaging mechanism is not well understood [12]. Recently, the influence of adsorbed water molecules and capillary condensation on nanotribological phenomena has been characterized by means of LFM friction experiments on silicon wafers [13]. It was reported that friction and adhesive forces were affected by the relative humidity of ambient air, but the behavior of these forces in atomic-scale imaging was not mentioned.…”