From Al4B2O9 nanowires to BN-coated Al18B4O33 nanowires

A novel route was proposed to completely coat aluminum borate nanowires by in situ providing the precursor for BN coating. Uniformly BN-coated Al18B4O33 nanowires could be obtained by the reaction of Al4B2O9 nanowires with ammonia at high temperature. The high-temperature unstable Al4B2O9 nanowires were converted into Al18B4O33 nanowires, simultaneously evaporated boron oxide. The reaction between the in situ generated vapors and ammonia ensures that the BN layers are attached tightly on the surface of the as-formed Al18B4O33 nanowires.