Method of low pressure and/or evaporative drying of aerogel

• US 5,420,168 A
• Filed: 04/01/1993
• Issued: 05/30/1995
• Est. Priority Date: 04/01/1993
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Pekala, Richard W., Mayer, Steven T., Kaschmitter, James L.
• Primary Examiner(s): Kight, III, John
• Assistant Examiner(s): Truong, Duc
• Application Number:
  US08/041,503
• Time in Patent Office: 789 Days
• Field of Search: 521/99, 521/113, 521/114, 521/64, 521/181, 502/418, 502/437
• US Class Current: 521/99
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: C08J 2361/00 Characterised by the use of condensation polymers of aldehydes or ketones with polyalcohols C08J2359/00; with polynitriles C08J2377/00; Derivatives of such polymers
• CPC Class Codes: C08J 9/28 by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• CPC Class Codes: Y02P 20/54 using solvents, e.g. supercritical solvents or ionic liquids

Abstract

A process whereby Resorcinol/Formaldehyde (RF) aerogel having a density of about 0.4-1.2 g/cc can be manufactured using a simple air drying procedure. This process is inherently simpler, quicker, and less expensive than the more conventional supercritical or subcritical CO₂ extraction procedures. RF aerogels can be used as produced, such as in insulation applications, or pyrolyzed to form carbon aerogels with a density of about 0.9 g/cc for use in applications such as batteries, supercapacitors, etc.

Claims

1. In a process for producing organic aerogels, the improvement comprising:

positioning the aerogel such that at least one surface thereof is exposed to air; and

removing the fluid from the pores of the aerogel by air drying.

2. The improvement of claim 1, additionally including the step of positioning the aerogel material such that opposite surfaces thereof are exposed to the air so as to enable comparable drying rates of the opposite surfaces.

3. The improvement of claim 1, additionally including the step of forming the aerogel precursor to be dried by:

forming a mixture of reactants in a solvent;

allowing the thus formed mixture to gel;

curing the thus formed gel to increase the cross-linking density;

exchanging the pore fluid in the gel with a selected solvent; and

allowing the selected solvent to evaporate during the air drying step, thereby forming an aerogel.

4. The improvement of claim 3, wherein the step of forming the mixture is carried out by at least mixing a monomer selected from the group consisting of resorcinol, phenol, catechol, phloroglucinol, and other polyhydroxybenzene compounds, with either formaldehyde or furfural in the presence of a base catalyst selected from the group of sodium carbonate, lithium carbonate, and potassium carbonate.

5. The improvement of claim 3, wherein the step of forming the mixture is carried out by mixing resorcinol, formaldehyde, and sodium carbonate in selected proportions.

6. The improvement of claim 5, wherein the step of curing is carried out at room temperature for a first period of time, at 50°

C. for a second time period, and then at 90°

C. for a third time period.

7. The improvement of claim 6, wherein the step of exchanging the pore fluid with a selected solvent is carried out by exchanging the fluid with acetone, and then exchanging the acetone with cyclohexane.

8. The improvement of claim 1, additionally including the step of pyrolyzing the thus dried aerogel in an inert atmosphere to form a carbonized aerogel.

9. The improvement of claim 8, wherein the atmosphere is nitrogen, and wherein the step of pyrolyzing is carried out at a temperature of 1050°

C.

10. The improvement of claim 9, wherein the organic aerogel is a resorcinol/formaldehyde aerogel.

23. The improvement of claim 1, additionally including the step of forming the thus produced aerogel in a desired configuration, which step of forming may be carried out prior to or after the air drying step.

24. The improvement of claim 6, wherein the step of exchanging the pore fluid with a selected solvent is carried out by exchanging the fluid with acetone, followed by evaporation and air drying, thereby forming the aerogel.

11. A method for producing an aerogel having a density in the range of 0.4-1.2 g/cc, comprising the steps of:

forming a mixture of a polymeric material with a solvent;

allowing the mixture to gel while minimizing any evaporation;

curing the thus gelled mixture to form an aquagel;

exchanging water in the aquagel with a selected solvent;

allowing the selected solvent to at least partially evaporate; and

air drying to form an aerogel.

12. The method of claim 11, additionally including the step of pyrolyzing the thus formed aerogel in an inert atmosphere to produce a carbonized aerogel.

13. The method of claim 12, wherein the step of pyrolyzing is carried out at a temperature of 1050°

C.

14. The method of claim 13, wherein the inert atmosphere is formed of nitrogen.

15. The method of claim 12, wherein the thus produced carbonized aerogel has a density of about 0.9 g/cc.

16. The method of claim 11, wherein the step of forming the mixture is carried out by mixing resorcinol, formaldehyde, and sodium carbonate in selected proportions.

17. The method of claim 16, wherein the step of curing the thus gelled mixture is carried out at room temperature for a specified time, at 50°

C. for a specified time, and then at 90°

C. for a specified time.

18. The method of claim 17, additionally including the step of forming selected size pieces of the aerogel by cutting the thus formed aquagel so as to form pieces of a selected size and thickness.

19. The method of claim 17, wherein the step of exchanging water with a selected solvent is carried out by exchanging the water with acetone and then exchanging the acetone with cyclohexane.

20. The method of claim 19, additionally including the step of positioning the formed aquagel such that opposite surfaces thereof are exposed to the air to provide comparable drying rates of the opposite surfaces.

21. The method of claim 11, wherein the step of air drying is carried out at a pressure of about 0.1-1.0 atmosphere.

22. The method of claim 11, wherein the step of air drying is carried out following the step of solvent exchanging.