Low compression set aerogels and aerogel composites and methods of making
This disclosure relates generally to aerogel technology. The disclosure relates more particularly, in various embodiments, to improved methods for producing aerogels and improved aerogel composites having a low compression set.
1. A method comprising:
(a) providing a first aerogel, wherein the first aerogel has a compression set greater than 15% as determined by ASTM D3574-Test D;
(b) heating the first aerogel under an atmosphere comprising greater than 10% oxygen by volume at a temperature between about 200° C. and 400° C. to obtain a second aerogel;
wherein the first aerogel is heated for a time sufficient to alter the compression set of the first aerogel such that the obtained second aerogel has a compression set less than or equal to 15% as determined by ASTM D3574-Test D.
2. The method of claim 1 , wherein the atmosphere comprises between about 15% oxygen to about 25% oxygen by volume.
3. The method of claim 1 , wherein the atmosphere is air.
4. The method of claim 1 , wherein the first aerogel is heated for a time of about 30 seconds or more.
5. The method of claim 1 , wherein the first aerogel is heated for a time of between about 30 seconds and about 3 hours.
6. The method of claim 1 , wherein during heating of the first aerogel the temperature is limited to a temperature below 400° C.
7. The method of claim 1 , wherein the first aerogel comprises silica.
8. The method of claim 1 , wherein the first aerogel comprises a base.
9. The method of claim 8 , wherein the base is an amine base.
10. The method of claim 8 , wherein the first aerogel comprises at least 0.5% of the base by weight.
11. The method of claim 8 , wherein the first aerogel comprises between 0.5% to about 10% of the base by weight.
12. The method of claim 8 , wherein an amount of base in the first aerogel is greater than an amount of base in the second aerogel.
13. The method of claim 1 , wherein the first aerogel is an aerogel composite comprising a reinforcement material.
14. The method of claim 13 , wherein the reinforcement material is a fiber reinforcement material.
15. The method of claim 1 , wherein the first aerogel is an aerogel composite comprising an opacifying additive.
16. The method of claim 15 , wherein the opacifying additive is selected from the group consisting of B 4 C, Diatomite, Manganese ferrite, MnO, NiO, SnO, Ag 2 O, Bi 2 O 3 , TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide, iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, or mixtures thereof.
17. The method of claim 15 , wherein the opacifying additive comprises silicon carbide.
18. The method of claim 1 , further comprising producing the first aerogel by the process comprising:
forming a wet gel material;
aging the wet gel material in a vessel by heating the wet gel material with an aging fluid at an aging temperature and an aging pressure, wherein the aging temperature is above a normal boiling point of the aging fluid, wherein aging pressure of the vessel is maintained above a vapor pressure of the aging fluid during heating; and
extracting the aging fluid from the heated wet-gel material to form the first aerogel.