Investigation of characteristics of carbon materials with various structures modified by plasmas using plasma diagnostics and materials-surface analysis

Abstract

This investigation was conducted on the surface modification of the carbon materials by the reactive plasma (O 2 and SF 6 plasma) and the inert gas plasma (Ar plasma) with objective of investigating the effects of plasma on various carbon materials with different structure. The carbon materials used were artificial graphite and glassy carbon. The contact angle and its elapsed change to their surfaces before and after plasma treatment was measured. Moreover, their surfaces were analyzed by ESCA, and we observed them by SEM. O 2 plasma or Ar plasma treatment makes the surface of the carbon materials hydrophilic, and the level of Ar plasma treatment was approximately one-half that with O 2 plasma. SF 6 plasma treatment makes its surface hydrophobic. The modification source was Ar + with the Ar plasma. The modification sources were radicals and ions with O 2 plasma, SF 5 + and SF 3 + and radicals. The role of Ar ion was mainly in the formation of highly reactive radicals with long lifetimes on the surface of samples by the bombardment of Ar ion. The differences in the results of plasma treatment using different types of plasma between AG and GC are considered to be due to the differences in the structure of materials. AG surface is less resistant to shock against plasmas than a GC one and due to the presence of many edge-type carbon sections, the surface becomes highly reactive.