Formation mechanism of nano titanium carbide on multi-walled carbon nanotube and influence of the nanocarbides on the load-bearing contribution of the nanotubes inner-walls in aluminum-matrix composites

Abstract

Carbon nanotubes (CNTs), generally do not completely impart their exceptional properties in aluminum-matrix composites because of the poor interfacial bonding between these nanofillers and the matrix. In the present study, surface modification of CNTs with nanocrystalline titanium carbide (TiC) was performed through a pressureless-spark plasma sintering. Mechanisms for the formation of nano TiC during the applied method were proposed. It was found that single nanocrystals of TiC were epitaxially grown on the surface of raw CNTs with the typical orientation relationship of TiC (200)//CNT (002) at the interface. The shapes of carbides were mostly nanolumps and nanoblocks relating to the reacted carbon sources. Different preferential nucleation sites for TiC, such as bamboo-like defects, radially unzipped sites were also investigated in details. Thermal stability of the modified-CNTs, analyzed by thermogravimetric analysis, showed a significant increment in thermal properties compared to raw CNTs. It was shown that TiC-modified CNT hybrid structure is helpful to improve the inner-wall bonding conditions, leading to the effective load transfer between the walls. It was revealed that compressive yield strength of Al-1.5 wt% modified-CNTs with the TiC:CNT mixing ratio of 4:2 is the highest compared with other composites with different amounts of CNTs.