AVS 46th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Invited Paper TF-TuM1
Coatings from Liquid and Supercritical Carbon Dioxide

Tuesday, October 26, 1999, 8:20 am, Room 615

Session: Advanced Thin Film Formation Chemistry
Presenter: R.G. Carbonell, North Carolina State University
Authors: B.J. Novick, North Carolina State University
E.N. Hoggan, North Carolina State University
D. Flowers, University of North Carolina
Y. Chernyak, North Carolina State University
J.M. DeSimone, North Carolina State University and University of North Carolina
R.G. Carbonell, North Carolina State University
Correspondent: Click to Email
Carbon dioxide offers several environmental as well as performance advantages over conventional solvents. The recent development of CO@sub 2@-soluble polymers and surfactants has broadened significantly the number of potential applications for supercritical and liquid carbon dioxide as a solvent for the formation of thin films and coatings. This paper discusses recent work on coatings of polymeric materials from both supercritical as well as liquid carbon dioxide. The rapid expansion of supercritical solution (RESS) process using CO@sub 2@ can produce thin films and sub-micron powders of a wide variety of inorganic and polymeric materials. The process involves the expansion of a solution through a nozzle to an ambient downstream pressure. The present work is aimed at gaining an understanding of the relationship between the morphology and dimensions of the precipitates and RESS operating conditions. A computational fluid dynamic analysis of the process path can help relate the rates of change of pressure and temperature in the nozzle to the thermodynamics of binodal and spinodal decomposition. These relationships govern deposition rates and the rates of droplet nucleation and growth. Liquid carbon dioxide also offers some advantages over conventional solvents for spin coating and free meniscus (dip coating) applications. Because of its low viscosity and low surface tension, it has the potential of forming thinner films and of penetrating into narrower features on the surfaces being coated. As examples, results are shown on the spin coating and development of CO@sub 2@-soluble polymers for photolithography, and the deposition of polymeric lubricants on the surface of hard disk drive materials by dip coating.