At most solid-solid interfaces of technological relevance, contact occurs at numerous asperities. A sharp AFM/FFM tip sliding on a surface simulates just one such contact. However, asperities come in all shapes and sizes. The effect of radius of a single asperity (tip) on the friction performance can be used using tips of different radii. AFM/FFM are used to study various tribological phenomena. AFM/FFM techniques are increasingly used for tribological studies of engineering surfaces at scales, ranging from atomic and molecular to microscales; studies include surface roughness, adhesion, friction, scratching, wear, indentation, detection of material transfer, and boundary lubrication.

Variations in atomic-scale friction and the observed displacement can be explained by the variation in interatomic forces in the normal and lateral directions. Microscale friction is generally found to be smaller than the macrofriction as there is less ploughing contribution in mircoscale measurements.

Modified AFM can be used to obtain load-displacement curves and for measurement of nanoindentation hardness and Young´s modulus of elasticity, with depth of indentation as low as 1 nm.

Boundary lubrication studies and measurement of lubricant-film thickness with a lateral resolution on a nanoscale can be conducted using AFM. Self-assembled monolayers and chemically-bonded lubricant films with a mobile fraction are superior in wear resistance.

Investigations of wear, scratching and indentation on nanoscales using the AFM can provide insights into failure mechanism of materials. Coefficients of friction, wear and mechanical properties such as hardness have been found to be different on the nanoscale than on the macroscale; generally, coefficients of friction and wear rates on micro- and nanoscales are smalles, whereas hardness is greater. Therefore, micro/nanotribological studies may help define the regimes for ultra-low friction and near zero wear.

These studies indicate that micromechanical devices may behave in ways that cannot be predicted from their larger counterparts. It is encouraging in this regard to find that materials properties at small scales can be superior - wear is lower, friction less. Moreover, new lubrication strategies such as the use of self-assembles monolayers promise to be very versatile and effective at these scales. In summary, these fundamental micro/nanotribological studies provide insight to molecular origins of adhesion, friction, wear and lubrication mechanisms.

Ort: Wilhelm-Klemm-Str. 10, SR C, IG I

Zeit: 11 Uhr c.t. Einladender: Fuchs