Carbon based composite material

Abstract

The present disclosure relates to a process for producing sheets of a composite material comprising a graphene film arranged on an amorphous carbon substrate, the process comprising the steps of: a) providing a lignin source and an aqueous solution to form a composition, b) depositing the composition on a metal surface, c) heating the composition on the metal surface to form the composite material.

Claims

1. A process for producing a composite material comprising a graphene film arranged on an amorphous carbon substrate, the process comprising the steps of a) providing a lignin source, a poly(vinyl alcohol), an alcohol, and an aqueous solution to form a composition; b) depositing the composition on a metal surface; and c) heating the composition on the metal surface to form the composite material on the metal surface.

2. The process according to claim 1, wherein the process further comprises a step d) removing the composite material from the metal surface to form flakes of the composite material.

3. The process according to claim 1, wherein the alcohol is isopropanol.

4. The process according the claim 3, wherein the composition comprises, by weight of the composition 10-30 weight- % of the lignin source 1-5 weight- % of poly(vinyl alcohol); 45-65 weight- % of isopropanol; and the balance comprising water.

5. The process according to claim 1, wherein the lignin source is a particulate lignin source, and wherein the step a) further comprises milling of the composition.

6. The process according to claim 1, wherein the metal surface is made of a metal selected from copper, a copper alloy, aluminum and an aluminum alloy.

7. The process according to claim 1, wherein the metal surface is a copper surface.

8. The process according to claim 1, wherein the composition on the metal surface is performed at a reaction temperature in the range of 500-1100° C.

9. The process according to claim 1, wherein the step c) is performed in an atmosphere comprising argon gas and/or hydrogen gas.

10. The process according to claim 1, wherein the step c) is performed in an atmosphere comprising argon gas and hydrogen gas.

11. The process according to claim 2, wherein the flakes formed in step d) have an average size in the range of 1 μm.sup.2-50 mm.sup.2.

12. The process according to claim 11, wherein the flakes formed in step d) have an average size in the range of 1 μm.sup.2-1 mm.sup.2.

13. The process according to claim 11, wherein the flakes formed in step d) have an average size in the range of 1 mm.sup.2-50 mm.sup.2.

14. A process for producing a composite material comprising a graphene film arranged on an amorphous carbon substrate, the process comprising the steps of a) providing a lignin source and an aqueous solution to form a composition; b) depositing the composition on a metal surface; c) heating the composition on the metal surface to form the composite material on the metal surface; and d) removing the composite material from the metal surface to form flakes of the composite material; wherein the flakes formed in step d) have an average size in the range of 1 μm.sup.2-50 mm.sup.2.

15. The process according to claim 14, wherein the lignin source is a particulate lignin source, and wherein the step a) further comprises milling of the composition.

16. The process according to claim 14, wherein the metal surface is made of a metal selected from copper, a copper alloy, aluminum, and an aluminum alloy.

17. The process according to claim 14, wherein the metal surface is a copper surface.

18. The process according to claim 14, wherein heating the composition on the metal surface is performed at a reaction temperature in the range of 500-1100° C.

19. The process according to claim 14, wherein the step c) is performed in an atmosphere comprising argon gas and/or hydrogen gas.

20. The process according to 22, wherein the flakes formed in step d) have an average size in the range of 1 μm.sup.2-1 mm.sup.2.

Description

BRIEF DESCRIPTION OF APPENDED DRAWINGS

(1) The invention will be described with reference to the following figures, in which

(2) FIG. 1 shows a light optical microscope image of flakes according to the present disclosure, before the flakes have been removed from the copper surface;

(3) FIG. 2 shows a light optical microscope image of flakes according to the present disclosure, after the flakes have been removed from the copper surface;

(4) FIG. 3 shows a Raman spectrum of the flakes when they are still attached to copper;

(5) FIG. 4 shows a Raman spectrum of the of the flakes after removal from the copper;

(6) FIG. 5 shows a schematic cross-section of a flake according the present disclosure;

(7) FIG. 6 shows a schematic cross-section the intermediate material according to the present disclosure.

DETAILED DESCRIPTION

(8) The present invention will be described by way of the following, non-limiting examples

Example 1

(9) Sample Preparation

(10) A carbon based composite material was prepared according to the following.

(11) 0.5 grams of particular lignin (Sigma Aldrich) was provided to a beaker along with 0.4 grams of deionized water, 0.05 g of poly(vinyl alcohol) (PVA) solution (10 mol-% PVA in water) and 1.05 g of isopropanol to form a slurry. The slurry was thereafter transferred to a ball mill (Planetary Mill Pulverisette) where the slurry was milled using grinding balls having a diameter in the range of 0.6-0.8 mm, in an amount of approximately two times the weight of the slurry. The slurry was milled in a scheme of 5×30 minutes, with a rest period of 15 minutes between each milling repetition. The milled slurry was thereafter collected from the mill using 60 ml a 1:1 solution of isopropanol and water.

(12) After milling, the milled slurry was treated in an ultrasonic bath.

(13) The milled slurry was thereafter deposited on a copper substrate, by drip coating the milled slurry onto the substrate to obtain a layer of slurry which substantially covered the copper substrate.

(14) The slurry was then allowed to dry on the copper surface for approximately 30 minutes.

(15) The slurry deposited copper surface was then heated in a tubular oven (Carbolite Gero) to a temperature of approximately 805° C. in an inert atmosphere of hydrogen gas and argon gas in an ratio of 0.05:0.95 at a flow of approximately 130 cc/min. The heat treatment was performed at 805° C. for approximately 20 minutes, after which the heat was turned off and the slurry deposited substrate was allowed to cool. The gas flow was lowered to 5 cc/min. When the temperature in the oven had decreased to 100° C., the gas flow was turned off. After this treatment, an intermediate product which comprised a carbon based composite material and the copper substrate was achieved.

(16) The composite material was removed from the copper substrate by sinking the substrate into a container comprising 4.5 M hydrochloric acid to etch the copper and to form flakes of the carbon based composite material.

(17) Light Optical Microscopy

(18) FIGS. 1 and 2 shows a light optical micrograms of flakes obtained according to the present invention. FIG. 1 shows the composite material in its intermediate form when the flakes are still attached to a metal surface, in this case a copper surface. As can be seen in FIG. 1, the composite material substantially covers the copper substrate.

(19) FIG. 2 shows the flakes of the present invention after removal from the metal substrate. It is clearly shown that the inventive method forms flakes of the composite material.

(20) The materials shown in FIGS. 1 and 2 were investigated using Raman spectroscopy.

(21) Raman Spectroscopy

(22) Raman spectrum of the flakes before removal from the copper surface is shown in FIG. 3. Raman spectrum of the flakes after removal from the metal surface is shown in FIG. 4.

(23) The Raman spectra was recorded with a Renishaw inVia Confocal Raman microscope with a 532 nm excitation wave length and constant power of 0.1% of the nominal maximum power of 500 mW. A 20× magnification objective was used and 20 cumulative acquisitions of 20 s for each single spectrum was taken.

(24) The spectrum in FIG. 3 shows a D peak at 1350 cm.sup.−1. The D peak represents the breathing mode of sp.sup.2-hybridized carbon in rings at defects and grain boundaries. The spectrum also shows a G peak at 1590 cm.sup.−1 indicating the in-plane vibration of sp.sup.2-boned crystalline carbon. The D/G band intensity ratio is characteristic for amorphous carbon. No 2D peak is visible as the spectra was taken from the top surface, where the graphene structure is not visible since the flakes are still attached to the copper with the graphene film adjacent to the copper.

(25) The spectrum in FIG. 4 shows a D peak at 1350 cm.sup.−1. The D peak represents the breathing mode of sp.sup.2-hybridized carbon in rings at defects and grain boundaries. The spectrum also shows a G peak at 1590 cm.sup.−1 indicating the in-plane vibration of sp.sup.2-boned crystalline carbon. The D/G band intensity ratio is characteristic for amorphous carbon. The 2D peak (2720 cm.sup.−1) which is visible in FIG. 4 indicates the presence of few layer graphene. The spectrum furthermore shows a D+G peak at 2958 cm.sup.−1.

Example 2

(26) A second sample was prepared in the same manner as in Example 1, but instead of removing the flakes using hydrochloric acid a step of electro-delamination was used. The metal surface was used as a first electrode, a graphite electrode as a second electrode and a solution of 0.05 M NaOH was used as electrolyte. A current of 25 mA/cm.sup.2 was then applied to the electrodes. The copper electrode was thereafter transferred to a container of MilliQ water which removed flakes of the composite material. The procedure was then repeated four times in order to remove all flakes from the copper surface.

Example 3

(27) FIG. 5 shows a schematic illustration of a cross section of the intermediate material 10 according to the present disclosure. The intermediate material comprises a metal surface 15. Adhered to a first side of the metal surface 15 is the composite material, wherein the first side of the film 11 comprising graphene adheres to a first side the metal surface 15. The substrate 13 comprising amorphous carbon adheres to the other side of the film 11. The film and the substrate forms the composite material 12.

(28) FIG. 6 shows a schematic illustration of a flake 10 according to the present disclosure, after the flake has been removed from the metal surface. The flake 12′ comprises a substrate 13 comprising amorphous carbon having a first side onto which a film 11 comprising graphene is adhered.

(29) Additionally, variations to the disclosed embodiments and examples can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Itemized List of Embodiments

(30) 1. A process for producing a composite material comprising a graphene film arranged on an amorphous carbon substrate, the process comprising the steps of a) providing a lignin source and an aqueous solution to form a composition b) depositing the composition on a metal surface c) heating the composition on the metal surface to form the composite material on the metal surface.

(31) 2. The process according to item 1, wherein the process further comprises a step d) removing the composite material from the metal surface to form flakes of the composite material.

(32) 3. The process according to any one of the preceding items, wherein the step a) further comprises providing a poly(vinyl alcohol) and an alcohol to the composition.

(33) 4. The process according to item 3, wherein the alcohol is isopropanol.

(34) 5. The process according the item 4, wherein the composition comprises, by weight of the composition 10-30 weight-% of the lignin source 1-5 weight-% of poly(vinyl alcohol) 45-65 weight-% of isopropanol

(35) the balance comprising water.

(36) 6. The process according to any of the preceding items, wherein the lignin source is a particulate lignin source, and wherein the step a) further comprises milling of the composition.

(37) 7. The process according to any of the preceding items, wherein the metal surface is a copper surface.

(38) 8. The process according to any of the preceding items, wherein the step c) further comprises heating the composition on the metal surface to a reaction temperature in the range of 500-1100° C.

(39) 9. The process according to any of the preceding items, wherein the step c) is performed in an atmosphere comprising argon gas and hydrogen gas.

(40) 10. The process according to any items 2-7, wherein the flakes formed in step d) has an average size in the range of 1 mm.sup.2-50 mm.sup.2.

(41) 11. A composite material formed as flakes having an average size of at least 1 mm.sup.2, wherein the flakes comprises a substrate comprising amorphous carbon having a first side oppositely arranged a second side, and a graphene film arranged on at least the first side of the substrate.

(42) 12. The composite material according to item 11, wherein the graphene film substantially covers the first side of the substrate.

(43) 13. The composite material according to any one of items 11-12, wherein the flakes has an average size in the range of 1 mm.sup.2-50 mm.sup.2.

(44) 14. The composite material according to any one of items 11-13, wherein the composite material is obtainable from a lignin containing source.

(45) 15. An intermediate composite material comprising a substrate comprising amorphous carbon having a first side oppositely arranged a second side, and a graphene film arranged on at least the first side of the substrate wherein one side of the substrate is arranged on a metal surface.