Figure 6: (i) New Fe oxide (A-H) The evolution of α-Fe₂O₃ microstructure from their re-nucleation and re-crystallization through particle heat treatment in a mixture of H₂/air at high temperature (around 900 °C) for 1 h. Scale bars: D3: 100 nm; A, B, C (1–5), D(1,2,4,5), E, F, G, H (1-5): 1 μm.
(ii) New Fe oxide with grain and grain boundary (A-D) The evolution of α-Fe₂O₃ microstructure in critical heat treatment at high temperature (around 900°C) for 1 h. (E) E1. Model of new 3D nanostructure of large α-Fe₂O₃ microparticle with the small grains and the large grains for C(C1). E2. Model of new grains on surface of large α-Fe₂O₃ microparticle for E(D5). Scale bars: B5, C3-5, D5: 100 nm; A(1–5), B(1–4), C(1–4), D(1,2): 1 μm [80]. © 2014 Elsevier Colloids Surf. A. All rights reserved. N. V. Long, Y. Yang, C. M. Thi, Y. Cao, M. Nogami, “Ultra-High Stability and Durability of α-Fe₂O₃ Oxide Micro- and Nano-Structures with Discovery of New 3D Structural Formation of Grain and Boundary”, Colloids Surf. A, vol. 456, pp. 184-194, 2014.
(iii) Instruments: Ovens and furnaces (A-D) from Japan & China (Photos by N.V. Long). Note: Some furnaces in China, annealing temperature can reach near 2000°C with or without pressure control for making FeC or SiC. Particle heat treatment processes in here for making Fe-based alloys and oxides are recommended in the most common range of 100-1000oC in this review.