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 (Al 18 B 4 O 33 ) heterogeneous core-shell nanowires using Al 4 B 2 O 9 nanowhiskers as rigid templates. This method allows the fabrication of Al 18 B 4 O 33 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/Al 18 B 4 O 33 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 Al 4 B 2 O 9 nanowhisker's decomposition temperature. The experimental results show that the BN on the BN/Al 18 B 4 O 33 heterogeneous core-shell structured nanowires conforms to the vapor–solid (VS) growth mechanism.