Wetting of carbon nanotubes by aluminum oxide

Most ceramic - carbon nanotube ( CNT) composite processing utilizes solid state sintering, hence the concept of wetting of CNTs by molten ceramic is absolutely new. In the present work on a plasma sprayed Al2O3-CNT nanocomposite, it is observed that molten Al2O3 spreads uniformly on the CNT surface by forming a thin (similar to 20-25 nm) ceramic layer without any cracks. The wettability of the Al2O3 - CNT system is associated with the surface tension and capillary forces as captured from the evolution of microstructure. The dynamic equilibrium between melting and solidification of Al2O3 was deduced from the meniscus height, curvature, contact perimeter and projection area of solidified Al2O3 on the CNT surface. This interfacial phenomenon illuminates the mechanisms of microstructure evolution from Al2O3-coated CNT bridge structures to CNT mesh formation. Consequent ab initio modeling depicted distorted iso-surface contours at the interface, suggesting partial bonding and good wettability of Al2O3 on the CNT surface.