Vitre-Graf Coating on Mullite. Low Cost Silican Solar Array Project: Large Area Silicon Sheet Task. Final Report, December 14, 1977-June 13, 1979

摘要

A technical and economic evaluation was made of a proprietary glass-like carbon glaze coating applied to mullite and graphite to be used either in thin-film silicon manufacture or in container ware applications. Preliminary evaluations had indicated that the glassy carbon coating reacts with molten silicon to form a silicon carbide reaction layer that may serve as a diffusion barrier to prevent silicon reaction with the substrate material. The technical evalution consisted of manufacturing test samples by varying materials and processing parameters in conformance with a pre-selected matrix. Various tests, primarily coating appearance, adherence and silicon reaction behavior was observed as a function of the test parameter variation. The results of these tests indicated that most graphite and carbonaceous materials used as substrates will produce a visually acceptable coating having excellent adherence over a wide range of processing parameters. However, no set of parameters produced a coating that could withstand the chemical attack from molten silicon and prevent reaction with a graphite substrate. The primary consideration of graphite substrates was in container ware applications requiring long-time molten silicon exposure. The conclusion of this study suggested that the glassy carbon coating might provide protection for time periods of 30 minutes or less, and therefore was not suitable for the intended application. The economic analysis generated a process based on the selected parameters for coating glassy carbon onto newly developed mullite substrate material. By using the interim standard price estimating equation a projected cost of $1.30/m exp 2 was calculated based on 1975 dollars. (ERA citation 05:021982)