In-situ synthesis of BN/Al18B4O33 heterogeneous core-shell nanowires with different BN shell thicknesses and the microstructure evolution mechanism

A simple method was developed for the controllable synthesis of novel BN-coated aluminum borate (Al18B4O33) heterogeneous core-shell nanowires using Al4B2O9 nanowhiskers as rigid templates. This method allows the fabrication of Al18B4O33 nanowires with BN coatings of different thicknesses. The phases, microstructures, and chemical compositions of the samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and other characterization techniques. The heterogeneous core-shell nanowires of BN/Al18B4O33 had diameters and tube lengths of 35–60 nm and 400–600 nm, respectively, and the thickness of the BN cladding shell was between 2 and 7 nm. The concentration of B* volatilized on the whisker surface could be controlled by varying the ammonia flow rate, which in turn regulated the thickness of the BN cladding layer. The thickness of the BN cladding changed more significantly when the ammonia flow rate was varied at the Al4B2O9 nanowhisker’s decomposition temperature. The experimental results show that the BN on the BN/Al18B4O33 heterogeneous core-shell structured nanowires conforms to the vapor–solid (VS) growth mechanism.