Size-dependent structural transition thermodynamics of octahedral nanoparticles: Theoretical and experimental study

Abstract

The structural transition of nanoparticles is greatly different from corresponding bulk materials, where particle size plays an important role. However, the effect of particle size on structural transition thermodynamics of octahedral nanoparticles has not been reported. Herein, the relations of structural transition temperature and thermodynamic properties with length of octahedral nanoparticles were derived, the effects of length on structural transition temperature and thermodynamic properties of octahedral nanoparticles were discussed. In experiment, the structural transition of octahedral nano-Fe2O3 from phase γ to α was taken as a system to research the size-dependent structural transition thermodynamics; and the structural transition temperature and thermodynamic properties were determined by DSC. The experimental results are consistent with the theoretical relationships.The results show that there are significant effects of the length on the temperature, the enthalpy and the entropy of structural transition of octahedral nanoparticles, and phase transition temperature and thermodynamic properties decrease with the length decreasing. Besides, within the length range of the experimental study, there exist linear relationships of phase transition temperature and thermodynamic properties with the reciprocal of the length, respectively. This research will play guiding roles for the preparation, research and application of octahedral nanoparticles.