Experimental Investigation Of Electrochemical Mechanism Of Voltage-Controlled Friction Phenomenon

In recent years it has been found that the friction coefficient of a metal/ceramic sliding couple in an aqueous solution increases in the presence of an external voltage. In order to clarify the mechanism of this phenomenon, in this thesis, a survey of the previous work on effects of external electric fields on tribological behaviors of materials was presented first, then a series of experiments on the voltage-controlled friction(VCF for abbreviation hereafter) and its response characteristics were undertaken, and several experiments by using electrochemical analysis and Micro Raman spectrum were done too. Based on the obtained experimental results and detailed analysis, an electrochemical model on the mechanism of the VCF phenomenon was proposed. At last a clutch based on the VCF technology was fabricated and tested.In the study of VCF in steady conditions it has been shown that the electrode current of the metal side of a metal/ceramic sliding couple determines whether friction coefficient increases or not, and the experimental conditions, such as the kinds of lubricants and their concentrations,affect the friction through the changes of the current.In the study of VCF responses it has been shown that the response time of friction to a step increase under external voltage can be as short as 0.5 sec. while about 1.5 sec is needed for the recovery process of friction.The static Cyclic Voltammetry(CV) was used to seek for the possible electrochemical reactions on the metal surface, and experiments which combine CV with rubbing experiments were undertaken to study the actual electrochemical reactions when the VCF phenomenon is taking place, and then the Amperometric i-t curve was used to contact electric potential with friction. Moreover, the Micro Raman analysis was used to examine the absorptive films on the metal surface under different voltages or other conditions. All of the experimental results have indicated that the VCF phenomenon was the results of electrochemical reactions and boundary film...