Doctoral Dissertations

Author

Liying Zhang

Abstract

"The main objectives of this research were to synthesize iron phosphate compounds, study phase equilibria in the iron phosphate system, focusing on the glass forming area, and investigate glass formability and properties based on the liquidus regions. Twelve iron phosphate compounds were successfully prepared and studied in terms of liquidus temperature or decomposition behavior. The liquidus surface of the Fe₃PO₇- Fe(PO₃)₃ system was re-determined and found to be significantly different from that originally presented by Wentrup in 1935. Eutectic points exist at 58.0 mole% Fe₂O₃ (1070⁰C), 42.7 mole% Fe₂O₃ (925°C), and 37.0 mole% Fe₂O₃ (907°C). The latter two eutectic points bracket the conventional iron phosphate glass-forming range. The liquidus surface of the Fe₂P₂O₇-Fe(PO₃)₂ system was also determined. A eutectic point exists at 52.8±0.5 mole% FeO and 935°C in the Fe₃PO₇- Fe(PO₃)₃ system. Glass formation of iron-rich phosphate glasses (nominal Fe/P ratios between 1.0 and 1.6) requiresa critical cooling rate in the range 10³-10⁴ ⁰C/sec, compared to 1-10⁰C/sec for conventional iron phosphate melts (nominal Fe/P ratios near 0.50). The structures of the iron-rich phosphate glasses are based on isolated orthophosphate tetrahedra, similar to those found in α-FePO₄. The stability of melts (with nominal Fe/P compositions between 0.50 and 0.67) against crystallization, described by the Angell and Weinberg parameters, generally decreases with increasing O/P and Fe/P ratios. The structures of crystalline and glassy iron phosphates were studied using Raman spectroscopy. The correlation of the structure of iron phosphate compounds and the Raman modes was summarized and established. The structural parameters (like P-O bond length) of glassy iron phosphates were predicted and discussed"--Abstract, page iv.

Advisor(s)

Schlesinger, Mark E.
Brow, Richard K.

Committee Member(s)

Smith, Jeffrey D.
Fahrenholtz, William
James, William Joseph

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Ceramic Engineering

Sponsor(s)

National Science Foundation (U.S.)

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2010

Journal article titles appearing in thesis/dissertation

  • Phase equilibria in the Fe₂O₃-P₂O₅ system
  • Glass formation from iron-rich phosphate melts
  • Thermal stability of glasses from the Fe₄(P₂O₇)₃ - Fe(PO₃)₃ system
  • Raman study of Iron-phosphate compounds and glasses

Pagination

xiii, 186 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2010 Liying Zhang, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Library of Congress Subject Headings

Phase diagrams
Radioactive wastes -- Storage

Thesis Number

T 9658

Print OCLC #

746209483

Electronic OCLC #

746212487

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