Claims
- 1. A precursor for a microcellular carbon foam characterized by a density in the range of about 30 to 1000 mg/cm.sup.3, substantially uniform distribution of cell sizes of diameters less than 100 .mu.m with a majority of the cells being of a diameter of less than about 10 .mu.m, well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.5 angstroms, with said foamed precursor prepared by
- a) dissolving polyacrylonitrile in a heated solution consisting essentially of at least one alkali metal halide and a solvent for the dissolution of a polyacrylonitrile in the heated solution and the phase inversion of the dissolved polyacrylonitrile to a liquid gel upon sufficient cooling of the heated solution, said heated solution of a solvent and at least one alkali metal halide containing the polyacrylonitrile consisting essentially of about 0.75 to about 30 wt. % polyacrylonitrile, about 68 to 97 wt. % solvent, and a sufficient concentration of at least one alkali metal halide to promote solubilization and the unraveling of molecules of polyacrylonitrile in solution and maintain these molecules in extended positions to promote a firm gel, an interconnected strut formation and an expanded d(002) X-ray turbostatic spacing during the formation of the gel by phase inversion;
- b) placing the heated solution including the dissolved polyacrylonitrile in containment means provided with one of a nucleating promoting means and a relatively smooth surface;
- c) sufficiently cooling the heated solution in the containment means to form a liquid gel of the polyacrylonitrile by phase inversion;
- d) removing the solvent and substantially all of the dissolved alkali metal halide from the gel to provide a porous foam consisting essentially of polyacrylonitrile;
- e) removing the residual solvent under vacuum;
- f) cross linking the dry polyacrylonitrile foam at an elevated temperature;
- g) curing the porous foam at an elevated temperature in an oxygen containing environment.
- 2. A precursor for a microcellular carbon foam as claimed in claim 1, wherein the solvent is selected from the group consisting of propylene carbonate, tetramethylene sulfone, gamma-butyrolactone, and mixtures thereof.
Parent Case Info
This application is a division of application Ser. No. 07/960,600, filed Oct. 13, 1992, now U.S. Pat. No. 5,208,003.
Government Interests
This invention was made with the support of the United States Government under contract No. DE-AC05-84OR21400 awarded by the U.S. Department of Energy. The United States Government has certain rights in this invention.
US Referenced Citations (22)
Divisions (1)
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Number |
Date |
Country |
Parent |
960600 |
Oct 1992 |
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