Synthesis of amorphic and hexagonal boron nitride via high temperature treatment of NH 3 BH 3 and Li(BH 3 NH 2 BH 2 NH 2 BH 3 ).

Thermal decomposition of NH 3 BH 3 and Li(BH 3 NH 2 BH 2 NH 2 BH 3 ) was investigated at temperatures up to 1000 °C under various conditions with an inert atmosphere. It was found that complete dehydrogenation of ammonia borane towards amorphous boron nitride (a-BN) occurs at 850 °C when using monel reactors or at 1000 °C with the hot isostatic pressing method (HIP), which is significantly lower than was earlier reported. Li(BH 3 NH 2 BH 2 NH 2 BH 3 ) was found to decompose towards hexagonal boron nitride (h-BN) at 1000 °C with the HIP method but at 850 °C in monel reactors towards a mixture of a-BN and h-BN. The findings are confirmed by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM).