Evaluation of isocyanate functionalization ratio on multi-walled carbon nanotubes during N2/CO2 plasma treatment

Abstract

We recently reported how effective and important carbon nanotubes with isocyanate groups after plasma treatment are to polyimide composite. This article is the following report showing the monitoring method for the isocyanate functionalization by plasma treatment on carbon nanotubes using optical emissions from nitrogen and oxygen atoms. We measured the functionalization ratio on the nanotubes with the fluorescent measurement and measured the number density in the gas phase with plasma actinometry. The number of the functionalized nanotubes became maximized when the plasma contained almost the same number density of nitrogen atoms as the number density of oxygen atoms in the gas phase. Our plasma utilized in this article reached this condition when the gas mixture of nitrogen and carbon dioxide had 90% of nitrogen content. These overall results indicated that the functionalization during plasma processing can be evaluated with the optical emission from the plasma.