Unveiling the existence and role of a liquid phase in a high temperature (1400 °C) pyrolytic carbon deposition process

Abstract

Based on experiments aiming at depositing pyrolytic carbon onto carbon nanotubes by means of a chemical vapor deposition (CVD) process at 1400 °C, the work we report here demonstrates that the deposition involves the transient formation of a liquid phase (here organic), and that wetting physics is still able to apply in spite of the high temperature and the nanoscale, i.e., far beyond the condition range usually investigated. This was unexpected, because the high temperature makes all the physical and chemical processes involved transitory, including the fact that the liquid turns itself into solid carbon because of the ongoing carbonization process. The observations provide an estimate of the time scales of the involved processes, as they have to be short enough to complete in spite of the high temperature conditions. From a practical point of view, as the resulting material is a solid, all-graphenic carbon, the work demonstrates that using wetting physics in high temperature CVD can be a way to dramatically modify the surface energetics and the nano/microscale morphology of carbon nanofilaments. The statement is assumed to also apply to other chemical systems.