recrystallisation of nanomaterials (rus. рекристаллизация наноматериалов) — change in the size of grain in polycrystalline solids through diffusion of substance between the grains of the same phase.

Description

Nanomaterials have rather extensive grain boundaries and result in a large excess of free energy, therefore, recrystallisation of nanomaterials proceeds rather intensively; grain growth can occur even at room temperature. Spontaneous grain growth (collective recrystallisation) occurs as a result of chemical diffusion, i.e., the diffusion process in the chemical field, where there is no concentration gradient, but there is a nonzero chemical potential gradient. The difference in chemical potential between grains of different sizes is due to the contribution of surface energy to the total energy of the grain. The relative magnitude of this contribution is larger, the smaller the grains, therefore, other things being equal, small grains have excess energy compared to larger ones. Since the thermodynamic reason for the spontaneous grain growth in a homogeneous polycrystalline substance is the reduction of the total energy in the system, large grains grow in the process of collective recrystallisation due to the disappearance of a number of small grains. Recrystallisation is more complex than diffusion and may not be limited to the latter. Recrystallisation is characterised by its activation energy. Change of average grain size in recrystallisation in nanomaterials and its duration t are described by the relation , where n = 1-4. Given the intensity of the recrystallisation process, in order to preserve the small grain size of nanomaterials, sintering duration and temperature should be reduced.

Author

  • Gusev Alexander I.

Sources

  1. Gusev A. I. Nanomaterials, Nanostructures, and Nanotechnologies (in Russian) // Fizmatlit, Moscow (2007) - 416 pp.
  2. Gusev A. I., Rempel A. A. Nanocrystalline Materials. — Cambridge: Cambridge International Science Publishing, 2004. — 351 p.

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