| Résumé | A study of various parameters affecting the crystallization process of amorphous silicon nitride produced by plasma gas-phase reaction was undertaken to determine the conditions under which whiskers are formed. This process is influenced by the ammonium chloride content of the starting powder and the presence of nitrogen in the furnace atmosphere. This last parameter is also influential on the α/β phase ratio, along with other factors like the silica content, temperature and duration of the thermal treatment. Heat treatment at 1500°C for 30 min under argon produced well-defined α-Si₃N₄ crystals with a hexagonal cross section, a mean length around 0.8 μm, and no sign of agglomeration. Under the same conditions, crystallization of silicon nitride in SiC-Si₃N₄ composite did not give crystals, but Si₃N₄ whiskers. Therefore silicon carbide plays a major role in their formation. |
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