Microcellular carbon foam and method
AssigneeMartin Marietta Energy Systems, Inc.
InventorsRonald F. Simandl, John D. Brown
Life of this patent
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Abstract
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 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.
Claims23
A method for producing a microcellular carbon foam of a density in the range of about 30 to 1000 mg/cm.sup.3 and open porosity provided by well interconnected strut morphology, comprising the steps of:
- a) dissolving polyacrylonitrile in a heated solution consisting essentially of at leas tone alkali metal halide and a solvent for the dissolution of the polyacrylonitrile in the heated solution and the phase inversion of the dissolved polyacrylonitrile to a liquid gel upon sufficient cooling of the heated solution;
- 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;
- and
- h) heating the porous foam in an inert atmosphere to a temperature sufficient to carbonize the polyacrylonitrile forming the porous foam to provide the microcellular carbon foam.
Dependencies are inferred from the claim text.