Reactive wetting and filling of boron nitride nanotubes by molten aluminum during equilibrium solidification

Interactions between long boron nitride nanotube (BNNT) fibrils and molten aluminum (Al) pool are probed in this study to assess the feasibility of fabricating composite materials by solidification route. BNNTs were found to survive high temperature and reactive conditions present in molten aluminum. Very limited interfacial reaction was observed, resulting in the formation of AIN, AIB(2) and AIB(10) in trace amounts. AIN was the principal reaction product, resulting in improved interfacial wetting. Calculations based on surface energies revealed improved work of interfacial adhesion due to AIN formation. BNNTs were found to be well integrated in the aluminum matrix, signifying AIN induced excellent wetting. We also report capillarity-induced high temperature filling of BNNT by molten Al. The filling was promoted by AIN formation. In addition, formation of B-rich AlBio phase inside the nanotube was observed. Nanotube filling by metal and subsequent reaction to form nano-ceramic phases is expected to alter mechanical properties of the cast Aluminum-BNNT composites. This study establishes the suitability of solidification route for developing high strength Al-BNNT composites in future. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.