Experimental Study Of Polycarbonate(PC) Scrtach Behavior At Nanoscale

Polycarbonate(PC)is a tough thermoplastic polymeric material that has been widely used in electronic appliances,medical field equipment,aerospace and other fields.With the development of nano-science and technology,micro-and nano-scale devices have been significantly developed due to their small size,light weight,low energy consumption,high degree of integration and intelligence.These miniaturized devices made of polymeric materials are subject to wear and scratch at micro-or nano-scale,which will cause nano-scale surface damage.Therefore,studying the scratch behavior of polymeric material at nanoscale will help to understand the nanoscale scratch mechanism and performance,and provide guidance for improving the surface quality of microdevices.In order to investigate the scratch behavior of PC at nanoscale,the following research works were carried out in this paper:(1)Based on the operation principle of atomic force microscope(AFM),an experimental method to study the nanoscale scratch of polymeric materials was designed.Experiments were conducted to investigate the scratch behavior of PC under different normal loads,and the nanoscratch friction force was characterized;(2)Using AFM,the surface morphology of PC was observed before and after the nanoscratch tests.The evolution of the scratch deformation of the material under different scratching normal loads was analysised,as well as the deformation mechanism.With the increasing of the normal load applied on the tip,the scratch damage mechanisms change and can be categorized into three modes accordingly: sliding on asperities,elastic deformed groove and permanent scratch groove;(3)The friction force during nanoscratch and the evolution mechanism of the nanofriction behavior were discussed.The stick-slip phenomenon during nanoscratch deformation was compared with the periodic fluctuation phenomenon in the nanoscratch friction force,and its mechanism analysis was performed.The friction force between the scratch tip and sample surface changes with the increasing of the normal load,and also can be classified into three stages.The stick-slip phenomena are found for all studied scratch normal levels.The amplitude-frequency characteristics of friction force along scratch path are well correlated to the stick-slip.There is a good agreement among scratch deformation modes,friction force and stick-slip.