Boron nitride nanotubes as nanocrucibles for morphology and phase transformations in encapsulated nanowires of the Mg–O system Original Research Article

Boron nitride (BN) nanotubes were filled with nanowires made of Mg-containing compounds: a metallic Mg-based material; a MgO-based phase; and a thermally and chemically unstable oxygen-rich MgO2-based phase. Crystallography of the tubes and their fillings was studied using high-resolution transmission electron microscopy, electron energy loss spectroscopy and energy dispersive X-ray analysis. These compounds displayed markedly different behavior inside BN nanotube channels during in situ TEM electron-irradiation-induced and thermal heating. The interplay between phases, their morphology and phase transformations were observed under heating. Thus the applicability of chemically and thermally stable BN nanotubes as one-dimensional nanocrucibles for novel nanoscale metallurgy/chemistry in the practically important Mg–O system has been thoroughly documented. This opens up a pathway for BN nanotube-channel-confined reactions in other inorganic systems.