| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Low temperature oxidation of spinel type MFe_2O_4-Fe_3O_4 solid solutions (M=Zn, Co) prepared by wetmethod was investigated by XRD, VSM, Mossbauer effect and XPS measurements, and TEM observation. The phase separation to MFe_2O_4 and magnetite occurred after the oxidation in air at 300℃. The crystallitesize of separated MFe_2O_4 and magnetite was of the order of 10 nm. The magnetite phase was oxidized to γ-FezOa during the long periods of 300℃ oxidation in air, because the separated magnetite was of the order of 10 nm. Thus we obtained the MFe2O4/γ-Fe_2O_3 nanocomposite after the long periods of oxidation at 300℃.
The phase separation to MFe_2O_4 and γ-Fe_2O_3 also occurred at the initial stage of 600℃ oxidation in air. Onthe other hand, the transformation of γ-Fe_2O_3 to α-Fe_2O_3 was observed after long periods of oxidation at600℃. In the case of M=Co, the coercive force increased after the oxidation in air. The maximum value of coercive force, 2,200 Oe was obtained after the 600℃ oxidation for 90 min. Phase separation of CoZnFe_2O_4-FesO_4 solutions (bulk sample) during the low temperature oxidation in airwas similar to that observed in the spinel type MFe_2O_4-Fe_3O_4 solid solutions (M=Zn, Co) prepared by wetmethod. The increase of the coercive force after oxidation in air was also observed in this system, and themaximum value of 1,500 Oe was obtained in the CoZnFe_2O_4/α-Fe_2O_3 nanocomposite.
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