Boron nitride nanotubes as nanocrucibles for morphology and phase transformations in encapsulated nanowires of the Mg-O system

摘要

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 MgO_2-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.