Prolonging the reaction time to 5 ~ 7 h, the fraction of Fe3O4 polyhedral LY2603618 clinical trial particles as well as the particle size of Fe3O4 increases gradually. As shown in Figure 7b,c, the values of saturation magnetization increase to 55 and 66 emu/g and the coercive forces decrease to 6.5 and 5.4 Oe for the reaction time of 5 and 7 h, respectively. Finally, the phase transition was completed at the reaction time of 9 h. The
Fe3O4 polyhedral particles show strong ferromagnetic behaviors with the highest saturation magnetization selleck chemical of 80 emu/g and the lowest coercive force of 5 Oe, as shown in Figure 7d. The magnetic properties of α-Fe2O3 hexagonal plates and Fe3O4 polyhedral particles are similar to the previous reports [27, 43]. Figure 8 Magnetic properties of mixed α-Fe 2 O 3 and Fe 3 O 4 particles prepared by hydrothermally induced phase transformation at 200°C. (a) 2 h, (b) 5 h, (c) 7 h, and (d) 9 h. Conclusions α-Fe2O3 nano/microhexagonal
plates can be successfully reduced to octahedral Fe3O4 particles with EDA in an alkaline solution under a low-temperature hydrothermal process. In general, the transformation consists of four stages: (1) the formation of α-Fe2O3 hexagonal plates triggered by KOH, (2) the dissolution of the α-Fe2O3 hexagonal plates, (3) the reduction of Fe3+ to Fe2+, and (4) the nucleation and growth of new Fe3O4 polyhedral particles. The Avrami equation can be used to describe the transformation kinetics. As the phase transformation proceeded, the magnetic properties of the sample gradually transformed selleck chemicals from weak ferromagnetic behaviors to strong ferromagnetic behaviors. Authors’ information JFL is a Ph.D. student at National Tsing Hua University. CJT holds a professor
position at National Tsing Hua University. Acknowledgements The authors acknowledge the support from the National Science Council through grant no. 101-2221-E-007-061-MY2. References 1. Wang Y, Cao J, Wang S, Guo X, Zhang J, Xia H, Zhang S, Wu S: Facile synthesis of porous α-Fe 2 O 3 nanorods and their application in ethanol sensors. J Phys Chem C 2008, STK38 112:17804–17808.CrossRef 2. Souza FL, Lopes KP, Longo E, Leite ER: The influence of the film thickness of nanostructured α-Fe 2 O 3 on water photooxidation. Phys Chem Chem Phys 2009, 11:1215–1219.CrossRef 3. Wu PC, Wang WS, Huang YT, Sheu HS, Lo YW, Tsai TL, Shieh DB, Yeh CS: Porous iron oxide based nanorods developed as delivery nanocapsules. Chem Eur J 2007, 13:3878–3885.CrossRef 4. Zou Y, Kan J, Wang Y: Fe 2 O 3 -graphene rice-on-sheet nanocomposite for high and fast lithium ion storage. J Phys Chem C 2011, 115:20747–20753.CrossRef 5. Dong FZ, Ling DS, Chun JJ, Zheng GY, Li PY, Chun HY: Hierarchical assembly of SnO 2 nanorod arrays on α-Fe 2 O 3 nanotubes: a case of interfacial lattice compatibility.