Synthesis of amorphic and hexagonal boron nitride via high temperature treatment of NH3BH3 and Li(BH3NH2BH2NH2BH3)

Thermal decomposition of NH3BH3 and Li(BH3NH2BH2NH2BH3) was investigated at temperatures up to 1000°C at various conditions under inert atmosphere. It was found that complete dehydrogenation of ammonia borane towards amorphous boron nitride (a-BN) occurs already at 850°C when using monel reactors or at 1000°C by hot isostatic pressing method (HIP), which is significantly lower than it was earlier reported. Li(BH3NH2BH2NH2BH3) was found to decompose towards hexagonal boron nitride (h-BN) at 1000°C by HIP method while 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).