Study On The Tribo-electrical Performance Of Polymer Film Under Reciprocating Sliding

Gradually exhaust of the traditional fossil energy inspires the development of the new energy harversting technology.Scientist has invented a triboelectric nanogenerator for converting the small dimensional mechanical energy into electrical power based on the triboelectrification and electrostatic induction effects of two kinds of materials.Recently,there are large number of researches on the electrical output performance of triboelectric nanogenerator in research groups at home and aboard,however,the mechanism of the triboelectrification is still not clear.From the perspective of tribology,a customized tribological and electrical evaluation system was design and assembly to investigate the triboelectrical behavior of various polymer films under reciprocating sliding condition.Low friction coefficient and high electrical output performace were achieved,and the mechanism for the low friction high electrical performance of the polymer film was discussed.To find a suitable counterpart material,the effect of material on the triboelectrical behavior was carried out.The results of three polymer films as up tribopair sliding against silicon substrate showed that 0.2 mm PTFE film demonstrated the best frictional and electrical properties,and thus it was considered as the best candidate material for the up tribopair.The results of three materials as down tribopair rubbing against PTFE film indicated that the friction coefficient was approximately 0.15 and aluminum substrate provided the best electrical output behavior when compared with silicon and copper substrates.To realized the low friction and high electrical output performaces of the PTFE film,firstly,the effect of surface roughness on the triboelectrical performance of PTFE film was studied based on the sandpaper sanding method.With the increase of the surface roughness of PTFE film,the triboelectrical behaivors of the PTFE film sliding against aluminum and silicon substrates showed little changes.Whereas,the friction coefficient greatly decreased from 0.14 to 0.076,open-circuit voltage increased from 3.08 V to 6.4 V,and the short-circuit current decreased from 40.02 nA to 36.76 nA.The contact combination of PTFE film and copper substrate provided a relative low friction coefficient.Secondly,through adding graphene nanoplates into the contact interface of PTFE and copper substrate,the friction coefficient was further decreased to 0.031,while the electrical output slightly decreased,thus the low frciton behavior in the triboelectrification of polyer film was achieved.Finally,the effect of surface modification with oxygen plasma on the triboelectrical performance of PTFE film was examined.The short-circuit current and open-circuit voltage of the modified PTFE film sliding against copper substrate were 101.75 nA and 14.01,respectively,which were 7.5 and 7.6 times higher than those values of the initial PTFE film,hence,the high electrical output performance of the polymer film was achieved.Accoding to the analysis of the worn surfaces by using optical microscopy and Raman spectroscopy,furrow wear of the PTFE film due to the sandpaper sanding was clearly observed.Through optimization of the contact interfaces,the friction force was reduced and low friction ceoffiicent was observed.Through adding graphene nanoplates to the interface,the extremely low shear strength of the graphene layer could further reduce the friction coefficient of the sliding interface of PTFE film.Through plasma irradiation of the PTFE film,the reactivity of the fluoride ion was further excited,a lot of static charge was accumulated and resulted in more transfer charge,and therefore higher electrical output performance of the PTFE film was osberved.