Publication Date

2004

Document Type

Dissertation/Thesis

First Advisor

Lin, C. T. (Chhui-Tsu)

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Chemistry and Biochemistry

LCSH

Metals--Surfaces; Environmental chemistry--Industrial applications

Abstract

This dissertation focuses on green chemistry methods to replace existing techniques of metal treatment as well as treated or untreated metal surface analysis and low-temperature sol-gel preparation of a fluorescent frequency converter. Conventional metal surface pretreatments frequently use some form of chromium (VI), a carcinogen. Several chrome-free metal pretreatments were formulated using the sol-gel process. These sol-gel pretreatments were thin, showed extensive crosslinking (6H+ hardness on cold-rolled steel), and performed comparably to the chromated pretreatment in corrosion tests as well as outperforming the chromated pretreatment in electrochemical impedance testing (10⁷ ohm cm² greater at 10 mHz). Galvanized steel is frequently treated with a chromate conversion coating, another source of chromium (VI). An antifingerprint primer (AFP) was developed using aqueous emulsions of organic resins, water, organic HAPs (hazardous air pollutants)-free cosolvents, and corrosion inhibitors. AFP test panels passed alkali resistance testing (no coating removed in 2 wt% sodium phosphate solution at 65°C for 2 min) followed by salt spray testing (<5% surface corrosion after 120 h in 35°C, 98% humidity, 5 wt% salt spray). Laser-induced breakdown spectroscopy (LIBS) was investigated as a possible tool for qualitative determination of metal alloys and their pretreatments. It was shown that this method could be used to distinguish between three aluminum alloys (2024-T3/bare, 2024-T3/clad, and 7075-T6) as well as to distinguish between an untreated aluminum surface, a chromated surface, and a chrome-free AFP coating. A sol-gel nanocoating for the iron powder used to make transformer cores was developed. The coating increased the temperature at which significant oxidation of the iron particles occurred by about 20–30°C while not affecting the interior structure of the iron particles. Fluorescent glass can be formed by doping the glass with a fluorescent material at high (∼1500°C) temperatures. A sol-gel-derived frequency converter was produced that was capable of converting ultraviolet light to 544 nm green light by use of terbium (III)-doped xerogels at room temperature. The xerogels were monolithic and large (1–6 inches).

Comments

Includes bibliographical references.

Extent

xii, 192 pages (some color pages)

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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