Exceptionally strong boron nitride nanotube aluminum composite interfaces

We report the direct strength property measurements along boron nitride nanotube (BNNT) aluminum (Al) composite interface using in situ scanning electron microscopy single-nanotube pullout techniques. The nanomechanical measurements reveal that the BNNT-Al interface possesses an average interfacial shear strength of ∼46 MPa and a maximum shear load of ∼340 nN, and is over 60% stronger than the comparable carbon nanotube (CNT) -Al interface. This strong interface enables significant loading of the nanotube during pull-out from the metal matrix with a generated maximum tensile stress close to its intrinsic strength limit. Density functional theory (DFT) calculations reveal stronger interfacial physio- and chemisorption interactions on an oxidized Al interface with hexagonal boron nitride (hBN) as compared to graphene, which are in contrast to comparable binding properties of hBN and graphene with pure Al. The exceptional Al-BNNT strength properties can thus be attributed to a partially oxidized metal-nanotube binding interface, which has important implications for optimizing the local interfacial load transfer and bulk properties of BNNT-metal nanocomposites.