Ultralight conductive metallic aerogels

1. A metal aerogel, comprising:

a plurality of metal nanowires formed into a porous three-dimensional structure, wherein the metal nanowires have welded junctions at intersections of the metal nanowires,

wherein pores in the structure are anisotropic.

2. The metal aerogel as recited in claim 1 , wherein the metal aerogel is essentially free of nanoparticles.

3. The metal aerogel as recited in claim 1 , wherein the metal nanowires are silver nanowires.

4. The metal aerogel as recited in claim 1 , wherein the metal aerogel has electrical conductivity.

5. The metal aerogel as recited in claim 1 , wherein an electrical conductivity of the metal aerogel is at least about 35,000 siemens per meter (S/m).

6. The metal aerogel as recited in claim 1 , wherein the pores are primarily aligned along a longitudinal axis of the three-dimensional structure.

7. The metal aerogel as recited in claim 1 , wherein the pores are primarily aligned about perpendicular to a longitudinal axis of the three-dimensional structure.

8. The metal aerogel as recited in claim 1 , wherein the pores of the structure have an average diameter in a range of 25 microns to about 1 micron.

9. The metal aerogel as recited in claim 1 , wherein the pores of the structure have an average diameter in a range of about 1 micron to about 1000 microns.

10. The metal aerogel as recited in claim 1 , wherein the metal aerogel is a metal foam.

11. The metal aerogel as recited in claim 1 , wherein a density of the metal aerogel is at least 4.8 milligrams per cubic centimeter (mg/cc).

12. The metal aerogel as recited in claim 1 , wherein the metal aerogel has tensile elasticity, wherein the metal aerogel has a Young's modulus up to about 16,800 pascals (Pa).

13. The metal aerogel as recited in claim 1 , wherein the plurality of metal nanowires comprises metal nanowires formed from at least one metal selected from the group consisting of gold, silver, copper, and nickel.

14. The metal aerogel as recited in claim 1 , wherein the plurality of metal nanowires comprises more than one type of metal nanowires.

15. A method of forming the metal aerogel as recited in claim 1 , the method comprising:

suspending a plurality of purified metal nanowires having a polymer coating in an aqueous solution thereby creating a suspension;

freeze casting the suspension;

lyophilizing the frozen suspension to a dry structure of metal nanowires; and

sintering the lyophilized structure of metal nanowires.

16. A metal aerogel, comprising:

a plurality of metal nanowires formed into a porous three-dimensional structure,

wherein the metal nanowires have welded junctions at intersections of the metal nanowires,

wherein pores in the structure are primarily aligned along a longitudinal axis of the three-dimensional structure.

17. The metal aerogel as recited in claim 16 , wherein the metal aerogel is essentially free of nanoparticles.

18. The metal aerogel as recited in claim 16 , wherein the metal nanowires are silver nanowires.

19. The metal aerogel as recited in claim 16 , wherein an electrical conductivity of the metal aerogel is at least about 35,000 siemens per meter (S/m).

20. The metal aerogel as recited in claim 16 , wherein the pores of the structure have an average diameter in a range of 25 microns to about 1 micron.

21. The metal aerogel as recited in claim 16 , wherein the pores of the structure have an average diameter in a range of about 1 micron to about 1000 microns.

22. The metal aerogel as recited in claim 16 , wherein a density of the metal aerogel is at least 4.8 milligrams per cubic centimeter (mg/cc).

23. The metal aerogel as recited in claim 16 , wherein the metal nanowires are essentially free of a polymer coating.

24. The metal aerogel as recited in claim 16 , wherein the axis of the pores is aligned along the longest length of the structure.