Lin, C. T. (Chhui-Tsu)
Ph.D. (Doctor of Philosophy)
Department of Chemistry and Biochemistry
Metals--Surfaces; Environmental chemistry--Industrial applications
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).
Sizemore, Charles A., "A green chemistry approach to multifunctional materials and coatings" (2004). Graduate Research Theses & Dissertations. 346.
xii, 192 pages (some color pages)
Northern Illinois University
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Includes bibliographical references.