Method for pore stabilized carbon foam
A method for producing carbon foam utilizing a particulate pore stabilizer is described. The method provides for an increase in the uniformity of the pore structure and distribution of pores throughout the carbon foam, as well as an increase in volume of the resultant carbon foam. A pore stabilized carbon foam prepared by the method is also described.
1. A method for producing pore stabilized carbon foam comprising the steps of:
adding a particulate pore stabilizer to a coal starting material to form an admixture, wherein the coal starting material comprises a high-volatile coal of bitumen, anthracite, lignite, and mixtures thereof, comprising about 35% to about 45% by weight volatile matter;
heating the admixture under controlled temperature and pressure to form a liquid phase admixture consisting of liquid coal starting material and suspended solid particulate pore stabilizer;
further heating the liquid phase admixture to form a plurality of pores in a pore stabilized carbon foam, wherein the particulate pore stabilizer particles positioned at an interface of the plurality of pores with the liquid phase admixture provides a wetting angle ranging from about 50 degrees and about 105 degrees, therein decreasing the pore size of the plurality of pores to about 50% of the pore size of a non-pore stabilized carbon foam consisting of only the coal starting material; and
wherein the volume of the pore stabilized carbon foam is increased about 5% to about 50% above the volume of the non-pore stabilized carbon foam.
2. The method of claim 1 , wherein the coal starting material comprises coal particulate, mesophase pitch, and mixtures thereof.
3. The method of claim 1 , wherein the particulate pore stabilizer comprises: carbon black; oxides of alumina; silica, boric acid and titania; aluminosilicate clay or kyanite; non-oxide powders of silicon carbide or metal powders; and mixtures thereof.
4. The method of claim 1 , wherein the initial heating step is performed at a temperature between about 300° C. and about 500° C.
5. The method of claim 1 , further comprising; heating the pore stabilized carbon foam in a non-reactive atmosphere to a temperature of about 3000° C.
6. The method of claim 1 , further comprising; sealing the surface of the pore stabilized carbon foam with a graphitic adhesive.
7. The method of claim 1 , wherein the particulate pore stabilizer is admixed in amounts ranging from about 0.1% to about 10% by weight.
8. The method of claim 1 , wherein the particulate pore stabilizer particle size is between 0 μm and 10 μm.
9. The method of claim 1 , further comprising; carbonizing and graphitizing the admixture.
10. The method of claim 1 , wherein the admixture comprises a mesophase pitch starting material and about 1% by weight carbon black particulate pore stabilizer, resulting in about 15% volume increase above non-pore stabilized carbon foam.
11. The method of claim 1 , wherein the admixture comprises a mesophase pitch starting material and about 1% by weight silica fume particulate pore stabilizer, resulting in about 40% volume increase above non-pore stabilized carbon foam.
12. The method of claim 1 , wherein the admixture comprises a particulate coal starting material and about 4% by weight calcined alumina particulate pore stabilizer, resulting in a more uniform distribution of pores.
13. The method of claim 1 , wherein the pore stabilized carbon foam density is in the range of about 0.1 to about 0.8 g/cm 3 .
14. The method of claim 1 , further comprising; controllably cooling the admixture to a temperature below about 100° C.
15. The method of claim 1 , wherein the heating step is performed in a non-oxidizing atmosphere at a heat up rate of about 1° C. to about 20° C. per hour.
16. The method of claim 1 , further comprising; soaking the admixture at a temperature of between 300° C. and 700° C. for about 10 minutes to about 12 hours.