Apparatus and method for bulk production of atomically thin 2-dimensional materials including graphene

Abstract

The present invention provides an apparatus for the production of Graphene and similar atomic scale laminar materials by the delamination of a bulk laminar material, such as graphite; the apparatus comprising a pump (112) for pumping a fluid, the fluid being a suspension of solid particles of the bulk laminar material, at a pressure of greater than 1 MPa, along a fluid conduit (12) and against an impact head (16) having an impact face perpendicular or substantially perpendicular to the trajectory of the incoming fluid, being the principal axis relative to the proximal end of the conduit (24) so as to form a narrow and variable gap (20) and where in the impact head is symmetric about a longitudinal axis which is in line with the principal axis and such that the symmetry allows rotation of the head. This apparatus provides prolonged head life and avoids catastrophic head wear in an isolated region. Overall product quality over time is better maintained. Also, the benefit of a self-unblocking delamination apparatus can be achieved whilst maintaining high product quality and consistency. Relatively small variation in gap size being sufficient to avoid blockage, such as occurs by the aggregation of large particles or groups of particles in the high shear gap used for delamination.

Claims

1. An apparatus for the production of Graphene and similar atomic scale laminar materials by the delamination of a bulk laminar material; the apparatus comprising: a main pump (112) suitable for pumping a fluid, the fluid being a suspension of solid particles of the bulk laminar material, at a pressure of greater than 1 MPa, towards and in fluid communication with; core components (10), the core components comprising: a fluid conduit (12) having a principal axis suitable for conveying said fluid, wherein the fluid conduit is arranged to direct fluid at said pressure from that conduit against; an impact head (16) having an impact face perpendicular or substantially perpendicular to said principal axis; the impact head and the conduit being arranged so that an annular gap (20) of between 500 μm and 1 μm results between an end of the conduit proximate to the impact head and the impact head wherein the gap forms a continuous region surrounding the end of the conduit and being substantially coplanar with the impact head; and an impact head surround (26) which extends the region in which the fluid is constrained before exiting the core components, wherein, the impact head is symmetric about a longitudinal axis which is in line with the principal axis and such that the symmetry allows rotation of the head.

2. The apparatus of claim 1, further comprising a pressure drop valve (124) downstream of the impact head (16) so as to provide backpressure.

3. The apparatus of claim 1 wherein the arrangement between the impact head face and the principal axis is 1° or less from perpendicular to the principal axis.

4. The apparatus of claim 1 wherein the impact head (16) of the apparatus is movable along the principal axis relative to the proximal end of the conduit (24) for adjusting the annular gap (20).

5. The apparatus of claim 1 wherein the impact head (16) of the apparatus is freely rotatable about the principal axis.

6. The apparatus of claim 1 wherein the impact head (16) of the apparatus is configured to be rotatable about the principal axis as constrained by a mechanism.

7. The apparatus of claim 1 wherein the impact head (16) of the apparatus is configured to, in use, be rotatable at a rate of between 0.01 and 50 rpm.

8. The apparatus of claim 1 wherein the impact head (16) of the apparatus is located in a housing and the lateral clearance fit between a bore of the housing which houses the impact head and the impact head lateral wall is as defined by ISO 286-2 H6 to H9.

9. The apparatus of claim 1, wherein the fluid that exits the core components is recycled back or is configured in use to be recycled back to the inlet of the main pump.

10. A method for exfoliation of laminar materials to produce atomic scale laminar materials by the delamination of bulk material; the method comprises the steps of: providing the apparatus described in claim 1 and; passing through the apparatus a suspension of laminar material in a liquid at a pressure of greater than 1 MPa at the impact head.

11. The method of claim 10, wherein the fluid that exits the core components is recycled back or is configured in use to be recycled back to the inlet of the main pump.

12. A method comprising: utilizing the apparatus of claim 1 for the production of Graphene and similar atomic scale laminar materials by the delamination of a bulk laminar material.

Description

SPECIFIC DESCRIPTION

(1) The apparatus of the present invention will now be illustrated by means of the following figures in which:

(2) FIG. 1 shows a schematic view of the fluid path through the apparatus of the present invention and illustrates core components;

(3) FIG. 2 shows a schematic view in cross-section of a first arrangement of core components of the apparatus of the present invention;

(4) FIG. 3 shows a schematic view in cross-section of a second arrangement of core components of the apparatus of the present invention;

(5) FIG. 4 shows a schematic view in cross-section of a second arrangement of core components of the apparatus of the present invention;

(6) FIG. 5 shows a schematic view of a system or apparatus of the present invention comprising the core components in conjunction with auxiliary components to provide an optimal processing system for performing the method of the present invention.

(7) FIG. 6 shows an impact head having suffered damage by use over prolonged use and which was constrained from rotation.

(8) FIG. 7 shows an impact head having suffered minimal wear from use over prolonged use and which was not constrained from rotation.

(9) The diagrams provide the following features: 10 assembly of core components; 12 fluid conduit/volume; 14 entrance to fluid conduit at a point distal from the impact head; 16 impact head assembly; 18 optional facing (impact face) of impact head assembly; 20 annulus; 202 frusto conical annulus; 204 outer annulus; 22 support structure; 24 exit of fluid conduit proximal to the impact head/proximal end of the conduit; 242 proximal end of the conduit, alternative form; 26 impact head surround; 28 face of the impact head; 32 conduit/pipe; (when the bottom line in FIG. 5) 100 system or (extended) apparatus of the present invention; 110 starting material vessel; 112 high pressure pump; 114 valve; 124 pressure drop valve; 116 finished product vessel; 118 chiller/cooler.

(10) Referring to FIGS. 1 to 4 In use the apparatus of the present invention has fluid pumped from a pump 112 through a conduit 32 in the form of a pipe which terminates as part of the core assembly 10. The core assembly 10 has a proximal end 24 of the pipe 32 in which fluid in the volume of the conduit 12 exits the conduit under pressure so as to impact upon impact head 16; which can have a face of a hardened material 18. When the fluid impacts upon the face of the impact head it then travels through annulus 20 defined between the face of the impact head 28 and the proximal end of the conduit 24 before exiting the core components, such as to be recirculated or to recover it as finished product. In the particular figure a further impact head surround 26 is provided so as to extend the region in which the fluid is constrained before exiting the core components in use. The impact head 16 of the apparatus is configured so as to be preferably movable relative to the proximal end of the conduit 24 and thus definition of an optimal annular gap 20 can be achieved.

(11) In FIG. 3 the proximal end of the conduit 242 has an internally bevelled face such that in use fluid being transferred from the volume of the conduit 12 through the core components accelerates in the annulus (which is now frusto conical) until a pinch point is arrived at giving maximal shear.

(12) In FIG. 4 the proximal end of the conduit 24 does not abut the impact head surround and provides an outer annulus region 204 in which turbulent flow may occur for improved processing. The outer annulus region 204 is presented in FIG. 3 in conjunction with the internally bevelled face but FIG. 3 may be provided without region 204.

(13) Referring to FIG. 5 a processing system of the present invention comprises core components 10 as previously described. The system is configured so that raw material is provided in vessel 110 and is pumped through high pressure pump 112 into the conduit 12/32 into the core components 10 and in particular the impact head 16 before exiting to optional pressure drop valve 124 so as to provide backpressure to the core components for improved processing. The system is further configured so that fluid then passes through directional control valve 114 either as finished product to product vessel 116 or is recirculated through chiller 118 before entering high pressure pump 112 for optional recirculation.

(14) Experimental

(15) An apparatus of the present invention comprising a 3 kw impeller pre-pump at 400 kPa output feeds a 30 kW multiple piston main pump pumping a graphite suspension of average particle size 20 μm and 100 g/l of graphite solid particles at a pressure of 60 MPa (+/−1 MPa) and a flow rate of 1200 l/hr along a fluid conduit having a principal axis a cylindrical impact head having an end impact face perpendicular to said principal axis. The cylinder is 15 mm diameter and 25 mm long and set in corresponding bore of a housing (itself a 20 cm long cylinder), the bore accommodating 15 mm of the cylindrical impact head. The gap is set at 5 μm. The suspension is initially at a temperature of 20° C. and is maintained at a temperature of 30° C. by cooling before recirculating back into the apparatus. The recirculation loop having a hold-up of 500 litres. The base of the cylindrical impact head (the face remote from the impact face) is supported by the housing. The impact head is located in the housing according to ISO 286-2 H7. The head is lightly scribed with an indicium on the side of the cylinder and this aligned with a similar indicium in the housing. The machine was run for 15 minutes. The foregoing is runs 1 and 4. The experiment was repeated with fresh suspension and the head sealed in place with an epoxy adhesive to stop rotation and to fill the ISO 286-2 H7 clearance, the indicia being re-aligned. This is runs 2 and 3.

(16) Results

(17) TABLE-US-00001 Rotation by inspection of Result indicia on dismantling Run Clean run, no blockage Moved by more than 90° 1 Run Blockage evidenced by 50% increase None - indicia still aligned 2 in backpressure after 5 minutes. Run Run 2 unblocked and continued None - indicia still aligned 3 blockage evidenced by 50% increase in backpressure after 8 minutes Run Clean run, no blockage - repeat of Moved by more than 90° 4 run 1 after adhesive removed and parts polished.

(18) It is thought that the rotating head serves to stop blockages building up by breaking up and dislodging the material before significant back-pressure is created. The blockage was also indirectly evidenced by seeing the residue on the apparatus when taken apart. Whilst blockage could be avoided by using a finer starting material this would require a pre-processing run to reduce the feedstock size and turn a continuous process into a less efficient batch process. A larger gap could also be used by this would give rise to a much longer processing time as the equipment would be run in two stages of gap size. The degree of rotations is not known from the above. However, from other experiments a rotation rate in the order of 10 rpm was inferred in a run-inspect-run etc. Run 5 otherwise equivalent to Run 1. The product of Runs 1 and 4 comprised graphene.

(19) The present invention provides an apparatus more resistant to blockage when used with a suspended solid capable of delamination. It is likely that solid which is not laminar would not be so easily broken up by a rotating head.

(20) Pressures herein are pressures above atmospheric pressure. Temperatures herein are 20° C. unless stated otherwise.

(21) Preferred embodiments of the present invention are as numbered below:

(22) 1. An apparatus for the production of Graphene and similar atomic scale laminar materials by the delamination of a bulk laminar material; the apparatus comprising: a main pump (112) suitable for pumping a fluid, the fluid being a suspension of solid particles of the bulk laminar material, at a pressure of greater than 1 MPa, towards and in fluid communication with; core components (10), the core components comprising: a fluid conduit (12) having a principal axis suitable for conveying said fluid, wherein the fluid conduit is arranged to direct fluid at said pressure from that conduit against; an impact head (16) having an impact face perpendicular or substantially perpendicular to said principal axis; the impact head and the conduit being arranged so that an annular gap (20) of between 500 μm and 1 μm results between an end of the conduit proximate to the impact head and the impact head wherein the gap forms a continuous region surrounding the end of the conduit and being substantially coplanar with the impact head; and an impact head surround (26) which extends the region in which the fluid is constrained before exiting the core components, wherein,

(23) the impact head is symmetric about a longitudinal axis which is in line with the principal axis and such that the symmetry allows rotation of the head.

(24) 2. The apparatus of embodiment 1, further comprising a pressure drop valve (124) downstream of the impact head (16) so as to provide backpressure.

(25) 3. The apparatus of embodiment 1 wherein the arrangement between the impact head face and the principal axis is 1° or less from perpendicular.

(26) 4. The apparatus of embodiment wherein the impact head (16) of the apparatus is movable along the principal axis relative to the proximal end of the conduit (24) for adjusting the annular gap (20).

(27) 5. The apparatus of embodiment wherein the impact head (16) of the apparatus is freely rotatable about the principal axis.

(28) 6. The apparatus of any of embodiments 1 to 4 wherein the impact head (16) of the apparatus is configured to be rotatable about the principal axis as constrained by a mechanism.

(29) 7. The apparatus of embodiment wherein the proximal end of the conduit (242) has an internally bevelled face such that the annular gap is frusto-conical, whereby in use fluid being transferred from the volume of the conduit (12) through the core components accelerates in until a minimum height of the annular gap is arrived at for giving maximal shear.

(30) 8. The apparatus of embodiment 5 wherein the width of the annular gap is between 500 μm and 200 μm at its widest point, and between 200 μm and 1 μm at its narrowest point.

(31) 9. The apparatus of embodiment wherein the proximal end of the conduit (24) does not abut the impact head surround (26) and provides an outer annulus region (204).

(32) 10. The apparatus of embodiment, wherein the impact face (18) of the impact head (16) comprises material selected from the group tungsten carbide, zirconia, silicon nitride, alumina silicon carbide, boron nitride and diamond.

(33) 11. The apparatus of embodiment, wherein the impact face of the impact head comprises diamond.

(34) 12. A method for exfoliation of laminar materials to produce atomic scale laminar materials by the delamination of bulk material; the method comprises the steps of: providing the apparatus described in Embodiment 1 and; passing through the apparatus a suspension of laminar material in a liquid at a pressure of greater than 1 MPa at the impact head.

(35) 13. The apparatus or method of embodiment, wherein the fluid that exits the core components is recycled back to the inlet of the main pump.

(36) 14. The apparatus or method of embodiment, wherein the temperature of the fluid is maintained in the range 30° C. to 80° C.

(37) 15. The method or apparatus of embodiment, where the impact head is maintained at a temperature less than 50° C.

(38) 16. The method or apparatus of embodiment 15, where the impact head (16) is maintained at a temperature less than 10° C.

(39) 17. The method or apparatus of embodiment wherein the fluid is impacted upon the impact head (16) at a pressure in the range 10 MPa to 150 MPa.

(40) 18. The method or apparatus of embodiment wherein the fluid is impacted upon the impact head at a pressure in the range 50 MPa to 70 Mpa.

(41) 19. The method or apparatus of embodiment wherein the fluid is impacted upon the impact head at a flow rate of greater than 1000 l/hr.

(42) 20. The method or apparatus of embodiment wherein the laminar material loading in the liquid phase is in the range up to 500 grams per litre (g/l).

(43) 21. The use of the apparatus of any of embodiments 1 to 11 for the production of Graphene and similar atomic scale laminar materials by the delamination of a bulk laminar material.

(44) 22. The use of the apparatus of any of embodiments 1 to 11 for the production of Graphene and similar atomic scale laminar materials wherein the solid particles are particles of graphite, hexagonal boron nitride or molybdenum disulphide.

(45) 23. The use of the apparatus of any of embodiments 1 to 12 for the production of graphene from an aqueous suspension of graphite.