Masters Theses

Yun Wang

Abstract

"The technique used to grow single zinc crystals was based on the Bridgman method. Zinc-gold, zinc-aluminum, and zinc-magnesium alloys were prepared and their single crystals were grown. Four crystallographic planes of the single zinc crystals were used for both chemical and anodic etching. The zinc alloys were etched more easily by acids than the purest (99.999%) zinc. The etching patterns changed for the different crystallographic planes of the single zinc crystals.

The appearance of particles during anodic dissolution of the single zinc crystals depended on time, acid concentration and current density. The partial disintegration of single zinc crystals is promoted by strong and prolonged etching. Four acids (HC1, HCIO4, H2SO4 and HNO3) were used as etchants; of them hydrochloric acid was the most effective. The particles were examined under high magnification with oil immersion. The black tiny particles with metallic luster were opaque to light, suggesting the presence of zinc metal.

The degree of disintegration of single zinc crystals in neutral salt solutions was determined quantitatively. The partial disintegration of a dissolving zinc anode in a 3 percent sodium bromate solution was studied. The apparent valence of Zn ions in bromate solution was smaller than that in nitrate solution. The degree of disintegration of zinc in bromate solution was about three times of that in nitrate solutions. The crystal structure and orientation do not affect the partial disintegration of zinc in nitrate and in bromate solutions to a noticeable extent. The dark film formed at the beginning of electrolysis, was obtained after twenty seconds by dipping the zinc anode into dry acetone. The flakes which spalled from the anode were collected and examined optically. They were composed of many small metallic zinc particles embedded in a matrix of zinc hydroxide. After thirty seconds of electrolysis the dark film gradually turned white and fell into the electrolyte.

The conclusion is that the normal valence of zinc ion does not change during anodic dissolution in bromate solutions, but rather that the apparent valence of less than two arises as a consequence of partial disintegration of the anode. The dissolution of zinc outside the electrical circuit thus accounts for the lower coulombic equivalent"-- Abstract, pp. ii-iii

Advisor(s)

Straumanis, Martin E., 1898-1973

Committee Member(s)

James, William Joseph
Leighly, Hollis P., 1923-2004
Proctor, Paul Dean, 1918-1999

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering

Publisher

University of Missouri at Rolla

Publication Date

1964

Pagination

xi, 89 pages

Note about bibliography

Includes bibliographical references (pages 86-87)

Rights

© 1964 Yun Wang, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Thesis Number

T 1607

Print OCLC #

5959181

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