Angularly resolved x-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure

Abstract

Monochromatized angularly resolved x-ray photoelectron spectroscopy (ARXPS) was used to study PTFE (Teflon) that had been exposed to an Earth orbital environment for approximately six years. The primary interest of the research is on a very reactive component of this environment (atomic oxygen) which, because of the typical orbital velocities of a spacecraft, impinge on exposed surfaces with 5 eV energy. Generation of such particles in a laboratory is not practical, thus, the atomic oxygen aspect must eventually be resolved in a space flight environment. This presentation deals with the method of analysis, the findings as they pertain to a rather complex carbon, oxygen, and fluorine XPS peak analysis, and the character of the valence bands. An improved bias referencing method, based on ARXPS, will also be demonstrated for evaluating specimen charging effects. It was found that the polymer molecule tends to resist the atomic oxygen attack by reorienting itself, so that the most electronegative CF3 groups are facing the incoming hyperthermal oxygen atoms. The implications of these findings to ground-based laboratory studies will also be discussed.