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Electro-mechanical behaviour or rough surfaces

Dr. Hanaor - Department of Ceramic Materials - TU Berlin's picture

Understanding electrical contact resistance 

Electrical contact resistance at interfaces between pairs of rough surfaces is of great importance in the performance of diverse systems, particularly in miniaturised electromechanical systems containing switches.


In this study, the role of pressure and surface structure is explored with a view towards gaining a beter understanding of electrical contact resistance.



Image result for Interfacial electro-mechanical behaviour at rough surfaces

Illustration of contact resistance at rough surfaces



In a range of energy systems, interfacial characteristics at the finest length scales strongly impact overall system performance, including cycle life, electrical power loss, and storage capacity. In this letter, we experimentally investigate the influence of surface topology on interfacial electro-mechanical properties, including contact stiffness and electrical conductance at rough surfaces under varying compressive stresses. We consider different rough surfaces modified through polishing and/or sand blasting. The measured normal contact stiffness, obtained through nanoindentation employing a partial unloading method, is shown to exhibit power law scaling with normal pressure, with the exponent of this relationship closely correlated to the fractal dimension of the surfaces. The electrical contact resistance at interfaces, measured using a controlled current method, revealed that the measured resistance is affected by testing current, mechanical loading, and surface topology. At a constant applied current, the electrical resistance as a function of applied normal stress is found to follow a power law within a certain range, the exponent of which is closely linked to surface topology. The correlation between stress-dependent electrical contact and normal contact stiffness is discussed based on simple scaling arguments. This study provides a first-order investigation connecting interfacial mechanical and electrical behaviour, applicable to studies of multiple components in energy systems.


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