Method for the manufacture of pristine graphene from Kish graphite

1. A method for the manufacture of pristine graphene from kish graphite comprising:

A. providing kish graphite,

B. pre-treating the kish graphite, said pre-treatment of kish-graphite including the following successive sub-steps:

i. a sieving step wherein the kish graphite is classified by size as follows:

a) kish graphite having a size below 50 μm,

b) kish graphite having a size above or equal to 50 μm,

the fraction a) of the kish graphite having the size below 50 μm being removed,

ii. a flotation step with the fraction b) of the kish graphite having the size above or equal to 50 μm,

iii. an acid leaching step wherein an acid is added so that a ratio in weight (acid amount)/(the kish graphite amount) is between 0.25 and 1.0,

iv. optionally washing and drying the kish graphite

C. synthesizing pristine graphene from the kish-graphite including the following successive sub-steps:

i. intercalating the kish graphite with a nitrate salt and an acid to obtain intercalated kish graphite,

ii. thermal expanding the intercalated kish graphite to obtain expanded kish graphite at a temperature above 600° C.,

iii. exfoliating the expanded kish graphite by ultra-sonication to obtain exfoliated kish graphite,

iv. separating unexfoliated kish graphite from the exfoliated kish graphite to obtain pristine graphene.

2. The method as recited in claim 1 wherein in step C.i, the nitrate salt is chosen from the group consisting of: NaNO 3 , NH 4 NO 3 , KNO 3 , Ni (NO 3 ) 2 , Cu(NO 3 ) 2 , Zn(NO 3 ) 2 , Al(NO 3 ) 3 and a mixture thereof.

3. The method as recited in claim 1 wherein in step, C.i the acid is chosen from the group consisting of: H 2 SO 4 , HCl, HNO 3 , H 3 PO 4 , C 2 H 2 Cl 2 O 2 (dichloroacetic acid), HSO 2 OH (alkylsulfonic acid) and a mixture thereof.

4. The method as recited in claim 1 wherein in step C.ii), the temperature is above 900° C.

5. The method as recited in claim 4 wherein in step C.ii), the temperature is between 900 and 1500° C.

6. The method as recited in claim 5 wherein in step C.ii), the temperature is between 900 and 1200° C.

7. The method as recited in claim 1 wherein in step C.ii), the expansion is performed during 1 min to 2 hours.

8. The method as recited in claim 1 wherein in step C.iii), before the mechanical exfoliation, the expanded kish graphite obtained in step Cii) is mixed with vitamin B2.

9. The method as recited in claim 8 wherein in step C.iii), the mixture of the expanded kish graphite and vitamin B2 is dispersed into water.

10. The method as recited in claim 1 wherein in step C.iii), the ultra-sonication is performed during a time above 1 hour.

11. The method as recited in claim 10 wherein in step C.iii), the time is between 1 h 30 min and 5 hours.

12. The method as recited in claim 1 wherein in step C.iii), during the ultra-sonication, the mixture is cooled down.

13. The method as recited in claim 12 wherein in step C.iii), the mixture is cooled down using an ice-bath.

14. The method as recited in claim 1 wherein in step C.iv), the separation is performed by centrifugation, decantation distillation or flotation.

15. The method of claim 1 , wherein the pristine graphene comprises one single layer of carbon atoms bonded together in a honeycomb lattice having less than 5% of oxygens groups, less than 5% of nitrogen groups and less than 0.5% of hydrogen atoms.

16. The method of claim 1 , wherein:

in step C.i), the nitrate salt is chosen from the group consisting of: NaNO 3 , NH 4 NO 3 , KNO 3 , Ni (NO 3 ) 2 , Cu(NO 3 ) 2 , Zn(NO 3 ) 2 , Al(NO 3 ) 3 and a mixture thereof, and the acid is chosen from the group consisting of: H 2 SO 4 , HCl, HNO 3 , H3PO 4 , C 2 H 2 Cl 2 O 2 (dichloroacetic acid), HSO 2 OH (alkylsulfonic acid) and a mixture thereof;

in step C.ii), the expansion is performed for 1 min to 2 hours; and

in step C.iii), the ultra-sonication is performed for at least 1 hour.