Tribology of Langmuir-Blodgett Layers

Abstract

Dynamic friction and wear were measured for tribological pairs of silicon substrates and ceramic sliders, both with oxidized surfaces coated with Langmuir-Blodgett (LB) monolayers and multilayers of cadmium arachidate. A novel technique combining scanning microellipsometry with the tribological experiments followed the wear of these thin organic films. The most stable couple had one LB monolayer at each surface and had wear rates up to 5 orders of magnitude lower than those of uncoated surfaces at contact pressures up to 108N/m2. With multilayers, the outer layers, except the very first one next to the solid surfaces, were removed rapidly, even for external contact pressures down to 106N/m2. This is in agreement with the fact that interlayer interaction forces are weak compared with the forces between the first layer and hydrophilic substrate surfaces. In comparison to physisorbed, fully fluorinated lubricants of the same thickness, mechanical durability orders of magnitude higher was observed with LB layers. © 1989, American Chemical Society. All rights reserved.