Ultra-high stability and durability of iron oxide micro- and nano-structures with discovery of new three-dimensional structural formation of grain and boundary

In this research, we have applied a facile polyol method with the addition of NaBH4 to synthesize polyhedral α-Fe2O3 oxide microparticles with the large size of 1–10 μm at 200–230 °C for about 25–30 min. The sharp polyhedral shapes and morphologies have been formed in the good assistance of NaBH4 as versatile strong reducing agent. The sharp polyhedral and large Fe oxide microparticles exhibited a uniform characterization of size, shape and morphology with the pure α-Fe2O3 structure. To study durability and stability of the microparticles under temperature, we have rationally carried out isothermal heat treatment of the prepared α-Fe2O3 oxide microparticles at high annealing temperature about 500 °C and 900–910 °C for 1 h. A new structure was found in the pure α-Fe2O3 particles with micro- and nano-structure co-existed with the very good formation of a three-dimensional (3D) structure with the oxide grains and the boundaries. The interesting phenomena of the deformation of surface, size, shape, and structure are discovered in α-Fe2O3 oxide microparticles by isothermal heat treatment. Apart from surface deformation, the new micro- and nano-structure of large α-Fe2O3 microparticles cannot be destroyed but they can be retained in their specific characteristics of size, shape, and morphology because of both plastic and elastic deformation co-existed. The interesting surface deformation by heat treatment is observed in comparison with the case without heat treatment. The typical magnetic properties of α-Fe2O3 microparticles were investigated in the appearance of grain and boundary. Finally, our proposal of the new technologies with particle heat treatment is very crucial to make novel micro- and nano-structures of ultra-high durability and stability with the grains and the boundaries that can be utilized in catalysis, energy and environment for future.