Interaction of Boron Nitride Nanotubes with Aluminium: A Computational Study

The interaction of boron nitride nanotubes (BNNTs) with Al has been investigated by means of quantum chemical calculations. Two model structures were used: a BNNT adsorbing a four atom Al₄ cluster, and a BNNT adsorbed on Al surfaces of different crystallographic orientations. The BNNTs were modeled as: (i) pristine, and (ii) having a boron (B-) or a nitrogen (N-) vacancy defect. The results indicated that the trends in binding energy for Al₄ clusters were, similar to those of the adsorption on Al surfaces, while the Al surface orientation has a limited effect. In all cases, the calculations reveal that Al binding to a BNNT was strongly enhanced at a defect site on the BNNT surface. This higher binding was accompanied by a significant distortion of the Al cluster or the Al lattice near the respective vacancy. In case of a B-vacancy, insertion of an Al atom into the defect of the BNNT lattice, was observed. The calculations suggest that in the Al/BNNT metal matrix composites, a defect-free BNNT experiences a weak binding interaction with the Al matrix and tthe commonly observed formation of AlN and AlB₂ was due to N- or B-vacancy defects within the BNNTs.