Magnetic field alignment of emulsions to produce porous articles
The use of magnetic fields in the production of porous articles is generally described. Certain embodiments are related to methods of producing porous articles in which magnetic fields are applied to an emulsion to align emulsion droplets. In some embodiments, after the emulsion droplets have been aligned, the emulsion droplets and/or the medium surrounding the emulsion droplets can be removed to leave behind a porous article. According to certain embodiments, polyvinyl alcohol can be used, for example, to stabilize the emulsion droplets and/or bind together components of the porous article. In some embodiments, water-soluble liquid alcohol can be used, for example, to stabilize the suspension of electronically conductive material within a phase of the emulsion.
1. A method, comprising:
exposing a matrix comprising a fluid and emulsion droplets within the fluid to a magnetic field such that the magnetic field causes at least a portion of the emulsion droplets to chain; and
at least partially removing the fluid and/or the emulsion droplets from the matrix to form anisotropic pores within the matrix,
wherein at least one of the fluid and the emulsion droplets contain water and a water-soluble liquid alcohol.
2. The method of claim 1 , wherein:
the emulsion droplets contain water and a water-soluble liquid alcohol, and
at least partially removing the fluid and/or the emulsion droplets from the matrix comprises at least partially removing the fluid to form anisotropic pores within the matrix.
3. The method of claim 1 , wherein:
the fluid contains water and a water-soluble liquid alcohol, and
at least partially removing the fluid and/or the emulsion droplets from the matrix comprises at least partially removing the emulsion droplets to form anisotropic pores within the matrix.
4. A method, comprising:
exposing a precursor composition of a porous article to a magnetic field which causes longitudinal axes of elongated regions of emulsion droplets within a fluid of the precursor to become substantially aligned with each other;
consolidating the composition; and
at least partially removing the fluid and/or the elongated regions of the emulsion droplets from the composition, thereby forming the porous article,
wherein the emulsion droplets and/or the fluid comprise a mixture comprising water and a water-soluble liquid alcohol.
5. The method of claim 1 , wherein the water-soluble liquid alcohol comprises a carbon chain length of up to 10 carbon atoms.
6. The method of claim 1 , wherein the water-soluble liquid alcohol comprises at least one of methanol, ethanol, propanol, and butanol.
7. The method of claim 1 , wherein the water-soluble liquid alcohol comprises ethanol.
8. The method of claim 1 , wherein the matrix further comprises a conductive additive.
9. The method of claim 8 , wherein the conductive additive comprises carbon black.
10. The method of claim 1 , wherein the ratio of water to the sum of the water-soluble liquid alcohols in the matrix is at least 2:1, by weight, during at least a portion of the time prior to the at least partially removing the fluid and/or the emulsion droplets.
11. The method of claim 4 , wherein forming the porous article is performed in the substantial absence of sintering.
12. The method of claim 1 , wherein the emulsion droplets comprise a magnetic fluid.
13. The method of claim 1 , wherein the matrix contains electrode material.
14. The method of claim 13 , wherein the electrode material comprises Li(Ni,Co,Al)O 2 , an LiMnO 3 —LiMO 2 alloy, and/or graphite.
15. The method of claim 1 , wherein exposing the matrix to the magnetic field causes emulsion droplets in the matrix to form multiple chains having longitudinal axes that are substantially aligned with each other.
16. The method of claim 3 , wherein at least partially removing the emulsion droplets from the matrix comprises evaporating emulsion droplet material from the matrix.
17. The method of claim 3 , wherein at least partially removing the emulsion droplets from the matrix comprises washing the emulsion droplets with a solvent.
18. The method of claim 3 , comprising, prior to at least partially removing the emulsion droplets, consolidating the matrix.
19. The method of claim 1 , wherein the matrix further comprises polyvinyl alcohol.
20. A method, comprising:
exposing a matrix comprising a fluid and emulsion droplets within the fluid to a magnetic field such that the magnetic field causes at least a portion of the emulsion droplets to chain; and
at least partially removing the fluid and/or the emulsion droplets from the matrix to form anisotropic pores within the matrix,
wherein at least one of the fluid and the emulsion droplets contain polyvinyl alcohol.