Decomposition mechanism of melamine borate (MB) in pyrolytic and thermo-oxidative conditions is investigated in the condensed and gas phases using solid state NMR (C-13 and B-11), X-ray photoelectron spectroscopy (XPS), pyrolysis-gas chromatography-mass spectrometry (py-GCMS) and thermogravimetric analysis coupled with a Fourier transform infrared spectrometer (TGA-FTIR). It is evidenced that orthoboric acid dehydrates to metaboric and then to boron oxide. The melamine is partially sublimated. At the same time, melamine condensates, i.e., melem and melon are formed. Melon is only formed in thermo-oxidative conditions. At higher temperature, melem and melon decompose releasing ammonia which reacts with the boron oxide to form boron nitride (BN) and BNO structures. (C) 2014 Elsevier B.V. All rights reserved.