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Ammonium tetrafluoroborate, a cheap and commonly used chemical, was successfully utilized in this study to synthesize BN-coated MgF2nanowires and collapsed BN nanotubes, although previous investigations have indicated that the compound cannot be used as a chemical vapour deposition (CVD) reaction precursor of amorphous or crystalline BN. Our study reveals that when MgCl2is used as a promoter a crystalline BN phase can be obtained on a large scale. The MgCl2also controls the product morphology, resulting in collapsed BN-coated MgF2nanowires at the first stage of CVD. The detailed morphology of the composite nanowires also depends on the reaction temperature. Increase in temperature stimulates the nanowire formation. The MgF2inclusions can be fully removed via a simple high-temperature evaporation procedure, forming collapsed BN nanotubes of high purity and yield. [ABSTRACT FROM AUTHOR]

Due to fast decomposition of Mg3N2 in the presence of water in the atmosphere (Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3), the synthesis of single-crystalline Mg3N2 nanowires has been a challenge. Here, we demonstrate that carbon nanotubes may serve as nanoreactors for a simple thermal reaction process resulting in the first fabrication of high-quality, large-yield, single-crystalline Mg3N2 nanowires. The Mg3N2 nanowires are homogeneously sheathed over their entire lengths with very thin graphitic carbon tubular layers, which effectively prevent their decomposition (even when the samples are put into water or exposed to atmosphere for several months). We have systematically analyzed for the first time the Mg3N2 nanomaterial by means of transmission electron microscopy (TEM), high-resolution TEM, and electron diffraction. Successful fabrication of carbon sheath protected Mg3N2 nanowires may promote further experimental studies on their crystal structures and properties. [ABSTRACT FROM AUTHOR]