Masters Theses

Abstract

"The effect of key parameters on the hydrothermal synthesis and colloidal stabilization of nanocrystalline CeO2 powders was investigated. In the hydrothermal synthesis, the effects of temperature, time, doping with Y3+ cations and the composition of the starting cerium salt on the characteristics of the powders were studied by X-ray line broadening and transmission electron microscopy. Stabilization of the colloidal suspensions was achieved by electrostatic or steric repulsion in an aqueous solvent. For steric stabilization, the adsorption of polymers was studied as a function of pH.

At a given temperature, the coarsening of the particles during hydrothermal synthesis can be described by a parabolic law, indicating that the interfacial reaction (dissolution) step was rate controlling. For powders prepared from Ce(NO3)3, the activation energy for coarsening was 25 ± 1 kJ/mol. The incorporation of Y3+ as a dopant produced a significant reduction in the rate of coarsening, with an activation energy of 27 ± 2 kJ/mol. The coarsening rate for undoped CeO2 prepared from CeCl3 was significantly lower than that for powders prepared from the nitrate. The effect of the particle characteristics on the sintering of powder compacts was also investigated.

In aqueous solvents, polyvinylpyrrolidone, PVP, showed significant adsorption which was dependent on the pH of the suspension. At a pH of 3.7 the largest amount of adsorbed PVP, molecular weight 24,000, was 10 wt%, based on the dry weight of the powder. The significance of the adsorption data for controlling the microstructural homogeneity was tested for by the preparation of films via the spin coating of suspensions and their characterization"--Abstract, page iii.

Advisor(s)

Rahaman, M. N., 1950-

Committee Member(s)

Anderson, H. U. (Harlan U.)
Neogi, P. (Partho), 1951-

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Ceramic Engineering

Publisher

University of Missouri--Rolla

Publication Date

Summer 1997

Pagination

x, 113 pages

Note about bibliography

Includes bibliographical references (pages 108-112).

Rights

© 1997 Shahid Lakhwani, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Thesis Number

T 7340

Print OCLC #

38155546

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