Fast shape evolution of TiN microcrystals in combustion synthesis

resumo

Single-phase TiN crystalline powder consisting of microcrystals has been prepared by combustion synthesis. During the drastic combustion reaction with a high reaction temperature and rapid heating rate, TiN microcrystals undergo a fast shape evolution process and finally develop into various crystallization shapes, such as quasi-spherical grains, faceted cubes or pyramids, and dendrites. The formation mechanisms of different crystal shapes are discussed in light of basic crystal growth theories. It is proposed that, at the initial stage, quasi-spherical TiN crystals are formed first by diffusion-controlled continuous growth; by a faceting process, flat surfaces then appear in several low-index directions on the quasi-spherical crystals, and at last, well-faceted crystals are produced by two-dimensional nucleation and layered growth. In addition, interesting TiN dendrites are observed, probably arising from the fast cooling rate in combustion synthesis. The dendrites grow quickly in three orthogonal directions, with each growth unit exhibiting a 4-fold symmetry and sometimes a half-octahedral pyramid head.

palavras-chave

TITANIUM NITRIDE; NITROGEN PRESSURE; GROWTH; WHISKERS; MECHANISM; TIN(001); KINETICS

categoria

Chemistry; Crystallography; Materials Science

autores

Liu, GH; Chen, KX; Zhou, HP; Tian, JJ; Pereira, C; Ferreira, JMF

nossos autores

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