Methods and compositions for preparing silica aerogels
Cross-linked sol-gel like materials and cross-linked aerogels, as well as methods for making such cross-linked sol-gel like materials and cross-linked aerogels are described.
1. A method of preparing a cross-linked aerogel comprising:
contacting an oxide-based sol-gel preformed material with a cross-linking agent thereby forming a surface layer of an organic or inorganic substance on a surface of said oxide-based sol-gel preformed material by chemical bonding to form a cross-linked oxide-based sol-gel material, wherein the surface layer is present in an amount at least about 2% by weight based on the total weight of the cross-linked oxide-based sol-gel material; and
drying the cross-linked oxide-based sol-gel material to form the cross-linked aerogel.
2. The method of claim 1 , wherein drying the cross-linked oxide-based sol-gel material comprises drying the cross-linked oxide-based sol-gel material supercritically.
3. The method of claim 2 , wherein drying the cross-linked oxide-based sol-gel material comprises drying the cross-linked oxide-based sol-gel material with liquid carbon dioxide.
4. The method of claim 1 , wherein the cross-linking agent comprises an isocyanate.
5. The method of claim 4 , wherein the isocyanate comprises a monoisocyanate, a diisocyanate, a triisocyanate, a tetraisocyanate, a polyisocyanate, an oligoisocyanate, a hexamethylene diisocyanate, a poly(hexamethylene diisocyanate), a toluene diisocyanate, a diphenylmethane diisocyanate, an aliphatic polyisocyanate, a triphenylmethyl triisocyanate, or a mixture thereof.
6. The method of claim 1 , wherein the cross-linking agent comprises an acid anhydride, an acylchloride, a bis(acid anhydride), a bis(acylchloride), or a mixture thereof.
7. The method of claim 1 , wherein the cross-linking agent comprises one or more attached groups.
8. The method of claim 7 , wherein the one or more attached groups include at least one of an absorbant, a catalyst, a biomolecule, a redox active label, a reactive group, or a mixture thereof.
9. The method of claim 1 , wherein the cross-linked aerogel is a silica aerogel.
10. The method of claim 1 , wherein the oxide-based sol-gel preformed material is substantially filled with a solvent.
11. The method of claim 10 , wherein the solvent comprises at least one of water, a ketone, an alcohol, an ester, a carbonate, a lactone, propylene carbonate, ethyl acetate, butyrolactone, or a mixture thereof.
12. The method of claim 10 , wherein the solvent comprises acetonitrile.
13. The method of claim 1 , wherein the oxide-based sol-gel material comprises silica.
14. The method of claim 13 , further comprising preparing the silica of the oxide-based sol-gel material from an alkoxy silica via an acid or a base-catalyzed route.
15. The method of claim 1 , wherein the cross-linking agent is contained in a solvent.
16. The method of claim 15 , wherein the solvent comprises at least one of water, a ketone, an alcohol, an ester, a carbonate, a lactone, an ether, a carboxylic acid, a phosphoric acid, a liquefied gas, propylene carbonate, ethyl acetate, butyrolactone, or a mixture thereof.
17. The method of claim 15 , wherein the solvent comprises acetonitrile.
18. The method of claim 1 , wherein the oxide-based sol-gel preformed material comprises one or more reactive groups on surfaces of the oxide-based sol-gel preformed material.
19. The method of claim 18 , wherein the one or more reactive groups comprises at least one of a hydroxyl group, a non-hydroxyl group, or a mixture thereof.
20. The method of claim 18 , wherein the one or more reactive groups comprises at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.
21. The method of claim 7 , wherein the one or more attached groups comprises at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.
22. The method of claim 1 , wherein the oxide-based sol-gel preformed material comprises linked oxide particles.
23. The method of claim 22 , wherein the linked oxide particles comprises one or more metal oxides.
24. The method of claim 22 , wherein the linked oxide particles comprises one or more metalloid oxides.
25. The method of claim 1 , wherein the cross-linked oxide-based sol-gel material comprises a material resulting from a sol-gel process.
26. The method of claim 1 , wherein the oxide-based sol-gel preformed material is in a form of a wet gel.
27. The method of claim 1 , wherein the cross-linking agent comprises one or more reactive groups includes at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.
28. A method of preparing a cross-linked oxide-based sol-gel material comprising:
forming an oxide-based sol-gel preformed material; and
contacting the oxide-based sol-gel preformed material with a cross-linking agent thereby forming a surface layer of an organic or inorganic substance on a surface of said oxide-based sol-gel preformed material by chemical bonding to form the cross-linked sol-gel material, wherein the surface layer is present in an amount at least about 2% by weight based on the total weight of the cross-linked oxide-based sol-gel material.
29. The method of claim 1 , wherein drying the cross-linked oxide-based sol-gel material comprises drying the cross-linked oxide-based sol-gel material subcritically.
30. The method of claim 29 , wherein drying the cross-linked oxide-based sol-gel material comprises drying the cross-linked oxide-based sol-gel material ambiently.
31. The method of claim 30 , wherein drying the cross-linked oxide-based sol-gel material ambiently comprises drying the cross-linked oxide-based sol-gel material in air.
32. The method of claim 30 , further comprising substantially filling the cross-linked oxide-based sol-gel material with pentane prior to drying ambiently.
33. The method of claim 1 , further comprising forming the cross-linked aerogel into a film.
34. The method of claim 1 , further comprising pyrolyzing the cross-linked aerogel.
35. The method of claim 34 , wherein the pyrolyzed cross-linked aerogel comprises carbon.
36. The method of claim 28 , further comprising forming the oxide-based sol-gel preformed material into a film.
37. The method of claim 28 , wherein the cross-linking agent comprises an isocyanate.
38. The method of claim 37 , wherein the isocyanate comprises a monoisocyanate, a diisocyanate, a triisocyanate, a tetraisocyanate, a polyisocyanate, an oligoisocyanate, a hexamethylene diisocyanate, a poly(hexamethylene diisocyanate), a toluene diisocyanate, a diphenylmethane diisocyanate, an aliphatic polyisocyanate, a triphenylmethyl triisocyanate, or a mixture thereof.
39. The method of claim 28 , wherein the cross-linking agent comprises an acid anhydride, an acylchloride, a bis(acid anhydride), a bis(acylchloride), or a mixture thereof.
40. The method of claim 28 , wherein the cross-linking agent comprises one or more attached groups.
41. The method of claim 40 , wherein the one or more attached groups include at least one of an absorbant, a catalyst, a biomolecule, a redox active label, a reactive group, or a mixture thereof.
42. The method of claim 28 , wherein the cross-linked aerogel is a silica aerogel.
43. The method of claim 28 , wherein the oxide-based sol-gel preformed material is substantially filled with a solvent.
44. The method of claim 43 , wherein the solvent comprises at least one of water, a ketone, an alcohol, an ester, a carbonate, a lactone, propylene carbonate, ethyl acetate, butyrolactone, or a mixture thereof.
45. The method of claim 43 , wherein the solvent comprises acetonitrile.
46. The method of claim 28 , wherein the oxide-based sol-gel material comprises silica.
47. The method of claim 46 , further comprising preparing the silica of the oxide-based sol-gel material from an alkoxy silica via an acid or a base-catalyzed route.
48. The method of claim 28 , wherein the cross-linking agent is contained in a solvent.
49. The method of claim 48 , wherein the solvent comprises at least one of water, a ketone, an alcohol, an ester, a carbonate, a lactone, an ether, a carboxylic acid, a phosphoric acid, a liquefied gas, propylene carbonate, ethyl acetate, butyrolactone, or a mixture thereof.
50. The method of claim 48 , wherein the solvent comprises acetonitrile.
51. The method of claim 41 , wherein the oxide-based sol-gel preformed material comprises one or more reactive groups on surfaces of the oxide-based sol-gel preformed material.
52. The method of claim 51 , wherein the one or more reactive groups comprises at least one of a hydroxyl group, a non-hydroxyl group, or a mixture thereof.
53. The method of claim 51 , wherein the one or more reactive groups comprises at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.
54. The method of claim 40 , wherein the one or more attached groups comprises at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.
55. The method of claim 28 , wherein the oxide-based sol-gel preformed material comprises linked oxide particles.
56. The method of claim 55 , wherein the linked oxide particles comprises one or more metal oxides.
57. The method of claim 55 , wherein the linked oxide particles comprises one or more metalloid oxides.
58. The method of claim 28 , wherein the cross-linked oxide-based sol-gel material comprises a material resulting from a sol-gel process.
59. The method of claim 28 , wherein the oxide-based sol-gel preformed material is in a form of a wet gel.
60. The method of claim 28 , wherein the cross-linking agent comprises one or more reactive groups includes at least one of an amine, an epoxide, a hydroxyl, an anhydride, an acylhalide, a carboxyl, or a mixture thereof.