Phase formation and decrystallization effects on BaCO3 + 4 Fe3O4 mixtures; A comparison of 83 GHz, multimode millimeter-wave and 2.45 Ghz single mode microwave H-field processing

Ramesh Peelamedu, Rustum Roy, Larry Hurtt, Dinesh Agrawal, Arne W. Fliflet, David Lewis, Ralph W. Bruce

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Samples of BaCO3 + 4 Fe3O4 mixtures were microwave irradiated in an 83 GHz gyrotron beam system and a 2.45 GHz single mode system. Twenty seconds of irradiation with 2-6 kW and 83 GHz energy lead to the formation of the BaFe12O19 form in major quantities, with unreacted Fe2O3 in minor quantities. A combination of 3 kW power and 90 s irradiation time resulted in selective absence of some X-ray diffraction (XRD) peaks and considerable reduction of other XRD peak intensities, suggesting that the BaFe12O19 surface is partially decrystallized. However, in a 2.45 GHz H-field system, irradiation of the BaCO3 + Fe3O4 mixture resulted in a total disappearance of peaks in the XRD, establishing complete decrystallization in 5 s. The 83 GHz effects appear to be mainly on the surface of the materials processed, whereas for the mixture reacted in the 2.45 GHz H-field the decrystallization effect occurs in bulk. These findings correlate well with the greatly different absorption lengths at the two frequencies.

Original languageEnglish (US)
Pages (from-to)119-129
Number of pages11
JournalMaterials Chemistry and Physics
Volume88
Issue number1
DOIs
StatePublished - Nov 15 2004

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Millimeter waves
millimeter waves
Microwaves
Irradiation
microwaves
X ray diffraction
irradiation
Processing
diffraction
x rays
energy

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Peelamedu, Ramesh ; Roy, Rustum ; Hurtt, Larry ; Agrawal, Dinesh ; Fliflet, Arne W. ; Lewis, David ; Bruce, Ralph W. / Phase formation and decrystallization effects on BaCO3 + 4 Fe3O4 mixtures; A comparison of 83 GHz, multimode millimeter-wave and 2.45 Ghz single mode microwave H-field processing. In: Materials Chemistry and Physics. 2004 ; Vol. 88, No. 1. pp. 119-129.
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Phase formation and decrystallization effects on BaCO3 + 4 Fe3O4 mixtures; A comparison of 83 GHz, multimode millimeter-wave and 2.45 Ghz single mode microwave H-field processing. / Peelamedu, Ramesh; Roy, Rustum; Hurtt, Larry; Agrawal, Dinesh; Fliflet, Arne W.; Lewis, David; Bruce, Ralph W.

In: Materials Chemistry and Physics, Vol. 88, No. 1, 15.11.2004, p. 119-129.

Research output: Contribution to journalArticle

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AU - Peelamedu, Ramesh

AU - Roy, Rustum

AU - Hurtt, Larry

AU - Agrawal, Dinesh

AU - Fliflet, Arne W.

AU - Lewis, David

AU - Bruce, Ralph W.

PY - 2004/11/15

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N2 - Samples of BaCO3 + 4 Fe3O4 mixtures were microwave irradiated in an 83 GHz gyrotron beam system and a 2.45 GHz single mode system. Twenty seconds of irradiation with 2-6 kW and 83 GHz energy lead to the formation of the BaFe12O19 form in major quantities, with unreacted Fe2O3 in minor quantities. A combination of 3 kW power and 90 s irradiation time resulted in selective absence of some X-ray diffraction (XRD) peaks and considerable reduction of other XRD peak intensities, suggesting that the BaFe12O19 surface is partially decrystallized. However, in a 2.45 GHz H-field system, irradiation of the BaCO3 + Fe3O4 mixture resulted in a total disappearance of peaks in the XRD, establishing complete decrystallization in 5 s. The 83 GHz effects appear to be mainly on the surface of the materials processed, whereas for the mixture reacted in the 2.45 GHz H-field the decrystallization effect occurs in bulk. These findings correlate well with the greatly different absorption lengths at the two frequencies.

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