Beta-si 3 n 4 nanoneedles in polyhydridomethylsilazane-derived ceramic products by polymeric precursor pyrolysis

A polymeric precursor, polyhydridomethylsilazane, was pyrolysed in an active ammonia atmosphere at 873 K with subsequent pyrolysis in an inert nitrogen atmosphere at 1873 K, and the polymer-derived ceramic products were studied using a field emission scanning electron microscope, X-ray diffractometer and high-resolution transmission electron microscope. No nanoneedles were observed in the 873 K pyrolysed products, while beta-Si3N4 nanoneedles were obtained after pyrolysis at 1873 K. The as-received nanoneedles were about 100-200 nm in diameter, and the maximum length reached about 10 μm. There were no bulbs or droplets on the tips of the nanoneedles, and no catalysts were used during the pyrolysis of the polymeric precursor.