Resumen
[0001] The present invention relates to a process for preparing graphene dried powder, comprising a) sonication of graphite in a mixture of water and a volatile organic solvent; b) centrifugation of the product obtained in step a); c) filtration of the product obtained in step b) to remove graphene flakes having lateral dimensions larger than 1 µm x 1 µm; d) addition of a precipitating agent to the solution obtained in step c) to precipitate the graphene flakes, and filtration to collect graphene dried powder; or alternatively, d') solvent evaporation to obtain graphene dried powder. The invention also relates to the graphene dried powder obtainable by said process and its use for preparing a graphene flake composition for coating surfaces.
Reivindicaciones
1. Process for preparing graphene dried powder, comprising the following steps: a) sonication of graphite in a mixture of water and a volatile organic solvent; b) centrifugation of the product obtained in step a); c) filtration of the product obtained in step b) to remove graphene flakes having lateral dimensions larger than 1 µm x 1 µm; d) addition of a precipitating agent to the solution obtained in step c) to precipitate the graphene flakes, and filtration to collect graphene dried powder; or alternatively, d') solvent evaporation to obtain graphene dried powder. 2. Process according to claim 1, wherein the graphite is sonicated in a mixture containing at least 10% w/w water, preferably at least 15% w/w water. 3. Process according to any of claims 1 or 2, wherein the volatile organic solvent is selected from dichloromethane, acetonitrile, tetrahydrofurane, acetone, alkyl alcohols and mixtures thereof. 4. Graphene dried powder obtainable according to a process as defined in any of claims 1 to 3. 5. Process for preparing a graphene flake composition comprising graphene flakes having lateral dimensions of less than 1 µm x 1 µm and a matrix, said process comprising the step of redispersing the graphene dried powder obtained according to any of claims 1 to 3 in a matrix. 6. Process according to claim 5, wherein the matrix is selected from a volatile organic solvent, curable material and cement. 7. A graphene flake composition comprising graphene flakes having lateral dimensions of less than 1 µm x 1 µm dispersed in a matrix. 8. A graphene flake composition according to claim 7, wherein the matrix is selected from a volatile organic solvent, curable material and cement. 9. A graphene flake composition according to claim 8, wherein the matrix is a volatile organic solvent selected from dichloromethane, acetonitrile, tetrahydrofurane, acetone, alkyl alcohols and mixtures thereof, and wherein the water content of the composition is equal or lower than 30% (v/v). 10. A graphene flake composition according to claim 9, which is substantially devoid of water. 11. A graphene flake composition according to any of claims 7 to 10, wherein the lateral dimensions of the flakes are between 100 x 100 and 600 nm x 600 nm, and the height of the flakes is between 2 and 10 nm, preferably wherein the flakes have lateral dimensions of 600 nm x 200 nm and a height between 6 and 8 nm. 12. An ink composition comprising a graphene flake composition according to any of claims 7 to 11, optionally including dyes, resins, lubricants, solubilizers or surfactants. 13. Use of graphene dried powder according to claim 4 for the preparation of a graphene flake composition according to any of claims 7 to 12. 14. Use of a composition according to any of claims 7 to 12 for coating surfaces in particular ink-jet printing, spray deposition, centrifugation techniques, spin coating, drop casting, dip coating, electrospray and Meyer rod method. 15. Use according to claim 14, wherein coating, in particular ink-jet printing spray deposition, centrifugation techniques, spin coating, drop casting, dip coating, electrospray and Meyer rod method is performed on SiO<2>, gold, acetate paper, or glass surfaces
