Performance evaluation of VACNT arrays under simulated LEO plasma environment

Abstract

The space applications of vertical aligned carbon nanotube (VACNT) arrays have attracted many researchers' interest in recent years. However, the influences of various space environmental factors on the VACNT arrays are mostly unknown. In this paper, the ground-based experiments of simulated plasma environment in low earth orbit (LEO) were presented. VACNT arrays synthesized by chemical vapor deposition are exposed in the vacuum chamber under different plasma parameters (time, plasma temperature, and plasma density). The morphological, structural as well as chemical surface modifications were investigated by scanning electron microscopy, Raman spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. Correlations of the plasma parameters to the adhesion of VACNT arrays were analyzed at micro-scale and nano-scale by nanoindentation and atomic force microscopy. The obtained data confirm that exposure to simulated LEO plasma environment will lead to the increase of defect degree, the damage of tube walls between CNTs, which will weaken the adhesion of VACNT arrays. However, the plasma will also react with the carbon tubes on the surface and introduce many polar groups, thus consolidating the adhesion of VACNT arrays. Our results provide experimental predictions needed to guide the design of VACNT arrays for space applications.