Figure 9: (a)-(b) Important new particle models and systems of grain and grain boundary structures belonging to polyhedral oxide and alloy particles with various size scales. Each particle contains hundreds to thousands grains inside its crystal structure. © 2014 “Materials and Design”. All rights reserved. N. V. Long, Y. Yang, T. Teranishi, C. M. Thi, Y. Cao, M. Nogami, “Synthesis and magnetism of hierarchical hematite and cobalt iron ferrite particles”, Materials and Design, vol. 86, pp. 797-808, 2015 [87].