Doctoral Dissertations

B. W. Jong

Abstract

"The formation sequence of (Cd,Mn,Fe) (Mn,Fe)₂O₄ from the individual oxides,x CdO + (1-x) MnCO₃ + α-Fe₂O₃,was found by X-Ray diffraction. Cd(Mn,Fe)₂O₄ was formed completely from CdO·Fe₂O₃ and CdO·Fe₂O₄ at 900°C and reacted with MnFe₂O₄ for 0 < x < 0.5 and with α-Fe₂O₃ for 0.5 < x < 1.0 to form a single phase of (Cd,Mn,Fe) (Mn,Fe)₂O₄ at 1150°C. This is the first time that the details involved in the formation sequence of CdMn-ferrite have been shown. A mixture of 0.5 CdO + 0.5 MnCO₃ + α-Fe₂O₃ was calcined at 900°C for 2 hrs forming Cd(Mn,Fe)₂O₄ with no Cd present in the other phases. Sintering was accomplished at 1150°C for 30 minutes forming a single phase of Cd₀.₅Mn₀.₅Fe₂O₄ with a bulk sintered density of 98-99% of the X-Ray density. The rate of changing density followed the relationship, p = K ln t + c, at temperatures between 1050°C and 1300°C. Magnetic properties of CdₓMn₁₋ₓFe₂O₄ were affected by composition x. A relationship, B = gx + h, was found between maximum magnetic flux density B and composition x at room temperature for 0 <̲ x <̲ 0.3. This was rationalized by a modification of Néel's theory. The maximum magnetic flux density decreased with increasing cadmium concentration for 0.3 < x <̲ 0.5. This decrease was attributed to the changing direction of the magnetic moment in the octahedral site sub-lattice according to the superexchange theory. No magnetic properties were observed due to the formation of a compensated antiferromagnetic phase for 0.5 < x <̲ 1.0. Maximum magnetic flux density increased with bulk density, while the coercive force decreased with the grain growth and the initial permeability increased with the bulk density and grain size. A stator core used for a-c electric motor application was formed by pre-sintering at 900⁰C for 2 hrs. Slots were then sawed with a tungsten carbide blade and final sintering was accomplished at 1150⁰C for 1 hr"--Abstract, pages iii-iv.

Advisor(s)

Ownby, P. D.

Committee Member(s)

Sorrell, Charles A.
James, William Joseph
Moore, Robert E., 1930-2003
Kreidl, N. J.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Ceramic Engineering

Sponsor(s)

Emerson Electric (Firm)
University of Missouri--Rolla. Ceramic Engineering Department
University of Missouri--Rolla. Materials Research Center

Publisher

University of Missouri--Rolla

Publication Date

1972

Journal article titles appearing in thesis/dissertation

  • Cadmium manganese ferrite formation study by x-ray diffraction
  • Cadmium manganese ferrite calcination and sintering
  • Cadmium manganese ferrite magnetic properties

Pagination

164 pages

Note about bibliography

Includes bibliographical references

Rights

© 1972 Bing-Wen Jong, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Ferrites (Magnetic materials) -- SynthesisFerrites (Magnetic materials) -- PropertiesCadmium compoundsManganese compounds

Thesis Number

T 2758

Print OCLC #

6034233

Electronic OCLC #

893629726

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