Electromagnetic interference shielding materials, devices, and methods of manufacture thereof
Described are electromagnetic shields comprising a substrate, a conductive additive, and a binder incorporated with the conductive additive and deposited on the substrate, and methods of making thereof.
1. A method of forming an electromagnetic shield comprising:
(a) forming a coating comprising:
(i) at least about 20% by mass of a conductive additive comprising reduced graphene oxide sheets, graphene oxide sheets, carbon black, and graphite;
(ii) a binder;
(iii) a solvent;
(iv) a surfactant; and
(v) a defoamer;
(b) depositing the coating on a substrate; and
(c) drying the coating on the substrate, thereby forming the electromagnetic shield.
2. The method of claim 1 , wherein the coating further comprises a viscosity modifier.
3. The method of claim 1 , wherein the forming of the coating comprises:
(a) mixing the coating;
(b) breaking down agglomerates in the coating;
(c) removing air bubbles from the coating; or
(d) any combination thereof.
4. The method of claim 1 , wherein depositing the coating on a substrate comprises depositing the coating on the substrate with a coating machine, a doctor's blade, a table-top coater, an air sprayer, or any combination thereof.
5. The method of claim 3 , wherein at least one of the breaking down of the agglomerates in the coating and the removing of the air bubbles from the coating is performed until the coating has a viscosity of about 1,000 mPa/s to about 5,000 mPa/s.
6. The method of claim 1 , wherein the conductive additive comprises a carbon-based additive.
7. The method of claim 6 , wherein the carbon-based additive comprises graphite, graphene, reduced graphene, graphene oxide, reduced graphene oxide, carbon black, cabot carbon, a carbon nanotube, a functionalized carbon nanotube, or any combination thereof.
8. The method of claim 6 , wherein the carbon-based additive comprises a carbon nanotube, or a functionalized carbon nanotube.
9. The method of claim 8 , wherein the carbon nanotube is a multiwalled carbon nanotube.
10. The method of claim 8 , wherein the functionalized carbon nanotube is functionalized with hydroxide, carboxy lie acid, or both.
11. The method of claim 8 , wherein the carbon nanotube comprises an outside diameter of about 20 nm to about 60 nm.
12. The method of claim 8 , wherein the carbon nanotube comprises a specific surface area of greater than about 60 m 2 /g.
13. The method of claim 8 , wherein the carbon nanotube has an electrical conductivity of greater than about 100 S/cm.
14. The method of claim 6 , wherein the carbon-based additive has a mean particle size of about 2 μm to about 30 μm.
15. The method of claim 6 , wherein the carbon-based additive comprises a specific surface area of about 2 m 2 /g to about 16 m 2 /g.
16. The method of claim 1 , wherein the solvent comprises a polar aprotic solvent comprising N-Methyl-2-pyrrolidone, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, propylene carbonate, or any combination thereof.
17. The method of claim 1 , wherein the solvent comprises a polar protic solvent comprising water, formic acid, n-butanol, isopropanol, nitromethane, ethanol, methanol, acetic acid, or any combination thereof.
18. The method of claim 1 , wherein drying the coating on the substrate comprises drying at a temperature of about 20° C. to about 120° C.
19. The method of claim 3 , further comprising breaking down agglomerates and removing air bubbles from the coating, wherein the breaking down agglomerates in the coating is performed by high shear mixing, and wherein the removing air bubbles from the coating is performed by vacuum mixing.
20. The method of claim 1 , further comprising calendaring the electromagnetic shield by a roll to roll calendaring machine.