University of Queensland
The integration of boron nitride nanotubes (BNNTs) into a metal (Al, Ti and Cu) matrix has been investigated by means of quantum chemical calculations. While the metal matrix was modelled employing a single atom, M4 clusters and whole surfaces with different orientations, the BNNTs interacting with metal were pristine, with B or N vacancy defects or exhibited C substitutions. Our results showed a signifficantly increased binding strength in the presenence of N or B vacant site as well as in the case were a C substitues a N. Furthermore, single atom and M4 cluster adsorption exhibited a similar trend compared to metal surfaces, however the obtained binding energies differed signifficantly. We found that the orientation of the surface present effected the binding strength of the BNNTs investigated. In cases of an increased binding strength, a signifficant relaxation of the Al and Ti surface below the respective impurity or vacancy defect was noted. In addition, especially in case of Ti, the BNNT was found to strongly deform.
Overall our data suggestes that high purity (pristine) BNNT based metal matrix composites (MMCs) are rather less likely to form due to too weak/strong interaction between the BNNTs and the Al/Ti surface. We further speculate that the often observed formation of aluminium borides or nitrides is caused through defects and impurities in the BNNTs, since these systems reveal a much stronger binding to the Al surface.