Development of novel ultralight and superstrong hybrid materials made of low density metals/alloys reinforced with boron nitride nanotubes for automobile and aerospace applications

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Aluminum/Boron nitride nanotube (BNNT) composites with up to 5 wt% (i.e. 9.7 vol%) nanotube fractions were prepared via various powder metallurgy routes, namely, Spark Plasma Sintering (SPS) and High Pressure Torsion (HPT) methods. Optical microscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis confirmed the integration of the two phases into decently dense and compact composites. No other phases, like Al borides or nitrides, form in the Al-BNNTs macrocomposites of the two series. The hardness of HPT samples was drastically increased with increasing BNNTs content in Al pellets. The value for Al-BNNT 3.0 wt% sample was more than doubled (190 MPa) compared to a pure Al HPT compact (90 MPa). And the room temperature ultimate tensile strength of Al-BNNTs HPT samples containing 3.0 wt% BNNT (~300 MPa) became ~1.5 times larger than that of a BNNT-free HPT Al compact (~200 MPa).