Synthesis, mechanical properties, and microstructure of dual-matrix (DM) aluminum-boron nitride nanotube (Al-BNNT) composites

Boron nitride nanotubes (BNNTs) are structurally similar to carbon nanotubes (CNTs) and have comparable mechanical properties. In addition, they surpass CNTs in terms of thermal stability and inertness. This opens many additional opportunities for taking advantage of their unique properties. Contrary to the extensive research conducted on aluminum (Al)-CNT composites, few studies have focused on Al-BNNT composites. In the present work, a novel Al-BNNT dual matrix composite is investigated. Pure unmilled Al powder is mixed with an equal weight of milled Al-2wt% BNNT composite powder with the objective of forming a dual matrix composite combining strength and ductility. The bulk composite was fabricated using milling and low-energy mixing followed by uniaxial compaction, tube cold rolling, and sintering. Bi-modal pure Al samples were also prepared using the same technique and used as reference samples. The dual matrix Al-BNNT composite exhibited an enhancement in mechanical properties, namely, a (+ 35.5%) increase in tensile strength, a (+ 91%) increase in indentation hardness, and a (+ 9%) increase in modulus of elasticity compared to the bi-modal Al without any significant reduction in ductility (- 2.25%). A detailed investigation of the structure of the composite is presented.

Automated summary

Boron nitride nanotubes (BNNTs) are structurally similar to carbon nanotubes (CNTs) and have comparable mechanical properties. In addition, they surpass CNTs in terms of thermal stability and inertness. A novel Al-BNNT dual matrix composite is investigated in this study, and it is found that the dual matrix composite exhibits enhanced mechanical properties without significant reduction in ductility, compared to the bi-modal Al.