Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-15T02:19:46.350Z Has data issue: false hasContentIssue false
  • English
  • Français

Micro/nanostructure observation of microwave-heated Fe3O4

Published online by Cambridge University Press:  31 January 2011

Noboru Yoshikawa ,
Ziping Cao ,
Dmitri Louzguin ,
Guoqiang Xie  and
Shoji Taniguchi
Noboru Yoshikawa*
Affiliation:
Tohoku University, Metallurgy, Sendai, Miyagi 980-8579, Japan
Shoji Taniguchi
Affiliation:
Tohoku University, Metallurgy, Sendai, Miyagi 980-8579, Japan
*
a) Address all correspondence to this author. e-mail: yoshin@material.tohoku.ac.jp
Get access

Abstract

To investigate the microwave (MW) processing of Fe3O4, for which occurrence of decrystallization has been reported, the micro/nanostructures of MW-heated Fe3O4 powder were observed in this study. The specimens were irradiated by 2.45 GHz MW at the position of magnetic (H)-field maximum in a TE10 single mode applicator. The specimen was heated well above the Curie temperature in H-field. The heated specimen above 1000 °C revealed the glass-like surface with the diminished x-ray diffraction (XRD) peak intensities. They resemble the reported features of decrystallization in an earlier work performed at Penn State University. According to the XRD profiles of the MW-heated specimens, formation of FeO and shift of Fe3O4 peaks to the lower angle with the broadened width were observed. To account for the findings, a model is presented that phase separation occurred into FeO and Fe3O4 resulting in an increased lattice parameter due to the increased oxygen content. This activity is caused by local transport of oxygen in nanoscale. Considering the shape of the main XRD Fe3O4 peak with a shoulder and the existence of halo in nanobeam diffraction (NBD), amorphous phase areas exist. As a result of transmission electron microscopy observation, it was shown that they were in nanoscaled localized regions, and it was not confirmed that the glass-like morphologies (or decrystallized morphologies) are totally amorphous. The observed micro/nanostructures and mechanism of the amorphous phase formation were discussed considering the Fe-O phase diagram.

Keywords

MicrostructureMicrowave heatingOxide
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 5 , May 2009 , pp. 1741 - 1747
Copyright
Copyright © Materials Research Society 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1.Katz, J.D.: Microwave sintering of ceramics. Annu. Rev. Mater. Sci. 22, 153 (1992).CrossRefGoogle Scholar
2.Clark, D.E. and Sutton, W.H.: Microwave processing of materials. Annu. Rev. Mater. Sci. 26, 299 (1996).CrossRefGoogle Scholar
3.Wroe, R. and Rowley, A.T.: Evidence for a non-thermal microwave effect in the sintering of partially stabilized zirconia. J. Mater. Sci. 31, 2019 (1996).CrossRefGoogle Scholar
4.Bykov, Y.V., Rybakov, K.I., and Semenov, V.E.: High-temperature microwave processing of materials. J. Phys. D: Appl. Phys. 34, R55 (2001).CrossRefGoogle Scholar
5.Microwave processing of materials. Committee on Microwave Proc. of Mater.: An Emerging Industrial Technology, editor (National Academy Press, Washington, DC, 1994), p. 2.Google Scholar
6.Sato, M., Roy, R., Ramesh, P., and Agrawal, D.: Microscopic non-equilibrium heating a possible mechanism of microwave effects, in Proc. Int. Symp. on Microwave Science and its Application to Related Fields (Takamatsu, Japan, 2004), pp. 339–340.Google Scholar
7.Roy, R., Peelamedu, R., Hurtt, L., Cheng, J., and Agrawal, D.: Definitive experimental evidence for microwave effects: Radically new effects of separated E and H fields, such as decrystallization of oxides in seconds. Mater. Res. Innovations 6, 128 (2002).CrossRefGoogle Scholar
8.Cheng, J., Roy, R., and Agrawal, D.: Experimental proof of major role of magnetic field losses in microwave heating of metallic composites. J. Mater. Sci. Lett. 20, 1561 (2001).CrossRefGoogle Scholar
9.Kimura, T., Takizawa, H., Ueda, K., and Endo, T.: Microwave synthesis of x-ray amorphous ferrites and the magnetic properties, in Proc. Inf. Conf. Microwave Chemistry (2000), p. 335.Google Scholar
10.Roy, R., Peelamedu, R., Grimes, C., Cheng, J., and Agrawal, D.: Major phase transformation and magnetic property changes caused by electromagnetic fields at microwave frequency. J. Mater. Res. 17(12), 3008 (2002).CrossRefGoogle Scholar
11.Peelamedu, R., Roy, R., Hurtt, L., Agrawal, D., Fliflet, A.W., Lewis, D. III, and Bruce, R.: Phase formation and decrystallization effects on BaCO3 + 4Fe3O4 mixtures; A comparison of 83 GHz, multimode millimeter-wave and 2.45 GHz single mode microwave H-field processing. Mater. Chem. Phys. 88, 119 (2004).CrossRefGoogle Scholar
12.Roy, R., Fang, Y., Cheng, J., and Grawal, D.A.: Decrystallizing solid crystalline titania, without melting using microwave magnetic field. J. Am. Ceram. Soc. 88(6), 1640 (2005).CrossRefGoogle Scholar
13.Peelamedu, R., Roy, R., Agrawal, D., and Drawl, W.: Field decrystallization and structural modification of highly doped silicon in a 2.45 GHz microwave single-mode cavity. J. Mater. Res. 19(6), 1599 (2004).CrossRefGoogle Scholar
14.Yoshikawa, N., Ishizuka, E., and Taniguchi, S.: Heating of metal particles in a single-mode microwave applicator. Mater. Trans. 47(3), 898 (2006).CrossRefGoogle Scholar
15.Kubaschewski, O.: Iron-Binary Phase Diagrams (Springer-Verlag, Berlin, Germany, 1982), p. 80.Google Scholar