Composite articles
View Patent ↗A composite structure is formed by depositing a one or more coatings on an open-cell foam skeleton to form a higher-density composite foam. In accordance with one aspect of the invention, the composite foam can be a carbon/carbon composite formed by a rapid densification process. The composite structure is suitable for use, for example, as a friction material employed in clutch and brake devices.
1. A carbon-carbon composite foam, having a structure of interconnecting pores that allow fluid to flow through the carbon-carbon composite foam, the carbon-carbon composite foam comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and
b) a pyrolytic carbon coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%.
2. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has an essentially isotropic structure.
3. The carbon-carbon composite foam of claim 1 , wherein the open lattice of carbon ligaments comprises one of amorphous carbon or crystalline carbon.
4. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has a solid density of at least about 40%.
5. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has a solid density of at least about 50%.
6. The carbon-carbon composite foam of claim 1 , wherein the foam is a pyrolysis product of a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
7. The carbon-carbon composite foam of claim 1 , wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor.
8. The carbon-carbon composite foam of claim 1 , comprising a ceramic coating comprising at least one of silicon carbide and silicon nitride.
9. The carbon-carbon composite foam of claim 8 , wherein the ceramic coating is deposited by the thermal decomposition of a liquid precursor selected from the group consisting essentially of methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane, and ti-is-n-methyl amino silane.
10. The carbon-carbon composite foam of claim 1 , wherein the pyrolytic carbon coating is a dielectric.
11. The carbon-carbon composite foam of claim 10 , wherein the pyrolytic carbon coating has a dielectric constant of at least 0.5.
12. The carbon-carbon composite of claim 1 , further including a chemical vapor deposition coating deposited on the pyrolytic carbon coating.
13. The carbon-carbon foam of claim 1 , wherein said foam includes pores being in the range of between about 500 and about 1,000 microns in diameter.
14. The carbon-carbon foam of claim 1 , wherein said foam includes micrographic porosity in the range of between about 60 and about 100 pores/inch.
15. The carbon-carbon foam of claim 1 , wherein said foam includes a bulk density of about 0.04 g/cm 3 .
16. The carbon-carbon foam of claim 1 , wherein said foam includes a surface area density of about 1.6 m 2 /g.
17. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has a solid density of at least about 67%.
18. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has a solid density of at least about 76%.
19. The carbon-carbon composite foam of claim 1 , wherein the carbon-carbon composite foam has a solid density of at least about 82%.
20. The carbon-carbon composite foam of claim 1 , wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor selected from a group consisting of cyclohexane, n-hexane, and benzene.
21. A carbon-carbon composite foam, comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and
b) a pyrolytic carbon coating on the open lattice of carbon ligaments, wherein an interior portion of the carbon-carbon composite foam has a solid density that is greater than the solid density of a peripheral portion of the composite foam.
22. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam defines a structure of interconnecting pores that allow hydraulic fluid to flow through the carbon-carbon composite foam.
23. The carbon-carbon composite foam of claim 21 , wherein the open lattice of carbon ligaments comprises one of amorphous carbon or crystalline carbon.
24. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam has a solid density of at least about 40%.
25. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam has a solid density of at least about 50%.
26. The carbon-carbon composite foam of claim 21 , wherein the foam is a pyrolytic product of a thermosetting polymer selected from the group consisting of polyurethanes, phenolics, and polyimides.
27. The carbon-carbon composite foam of claim 21 , wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor.
28. The carbon-carbon composite foam of claim 21 , comprising a ceramic coating comprising at least one of silicon carbide and silicon nitride.
29. The carbon-carbon composite foam of claim 28 , wherein the ceramic coating is deposited by the thermal decomposition of a liquid precursor selected from the group consisting essentially of methyltrichlorosilane, dimethyldichlorosilane, methyldichlorosilane, and tris-n-methyl amino silane.
30. The carbon-carbon composite foam of claim 21 , wherein the pyrolytic carbon coating is a dielectric.
31. The carbon-carbon composite foam of claim 30 , wherein the pyrolytic carbon coating has a dielectric constant of at least 0.5.
32. The carbon-carbon composite of claim 21 , further including a chemical vapor deposition coating deposited on the pyrolytic carbon coating.
33. The carbon-carbon foam of claim 21 , wherein said foam includes pores being in the range of between about 500 and about 1,000 microns in diameter.
34. The carbon-carbon foam of claim 21 , wherein said foam includes micrographic porosity in the range of between about 60 and about 100 pores/inch.
35. The carbon-carbon foam of claim 21 , wherein said foam includes a bulk density of about 0.04 g/cm 3 .
36. The carbon-carbon foam of claim 21 , wherein said foam includes a surface area density of about 1.6 m 2 /g.
37. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam has a solid density of at least about 67%.
38. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam has a solid density of at least about 76%.
39. The carbon-carbon composite foam of claim 21 , wherein the carbon-carbon composite foam has a solid density of at least about 82%.
40. The carbon-carbon composite foam of claim 21 , wherein the pyrolytic carbon coating is deposited by the thermal decomposition of a liquid precursor selected from a group consisting of cyclohexane, n-hexane, and benzene.
41. A composite foam having a structure of interconnecting pores that allow fluid to flow through the composite foam, the composite foam comprising:
a) an open lattice of carbon ligaments forming a network of three-dimensionally interconnected cells; and
b) a pyrolytic coating formed on the open lattice of carbon ligaments, wherein the carbon-carbon composite foam has a solid density of greater than 30%, and wherein the pyrolytic coating comprises at least one of silicon carbide and silicon nitride.