阅读说明：本技术 用于批量生产包括石墨烯的原子级薄的二维材料的装置和方法 (Apparatus and method for mass production of atomically thin two-dimensional materials including graphene ) 是由 保罗·拉迪斯劳斯 李·格拉斯哥 罗兰·马歇尔 于 2017-10-13 设计创作，主要内容包括：本发明提供了一种通过使得块体层状材料如石墨分层来制备石墨烯和类似原子级层状材料的装置；该装置包括：泵(112)以及冲击头(16),泵(112)用于在大于1MPa压力下沿着流体管道(12)泵送流体并且抵靠冲击头(16),该流体是块体层状材料的固体颗粒的悬浮液；冲击头(16)具有与进入流体的轨迹垂直或基本垂直的冲击面并且相对于管道(24)的近端作为主轴,以便形成狭窄且可变化的间隙(20),其中所述冲击头关于与所述主轴对齐一致的纵轴对称,使得该对称允许冲击头的旋转。该装置提供了延长的头部寿命并且避免了在隔离区中灾难性头部磨损。更好地保持整个过程的产品质量。并且可以实现自动解锁的分层装置所带来的益处,同时保持高产品质量和一致性。间隙尺寸相对小的变化足以避免堵塞,例如通过用于分层的高剪切间隙中大颗粒或颗粒组的聚集而发生的堵塞。(The present invention provides an apparatus for preparing graphene and similar atomic scale layered materials by layering bulk layered materials such as graphite; the device includes: a pump (112) and an impact head (16), the pump (112) for pumping a fluid at a pressure greater than 1MPa along the fluid conduit (12) and against the impact head (16), the fluid being a suspension of solid particles of a bulk laminar material; an impact head (16) having an impact face perpendicular or substantially perpendicular to the trajectory of the incoming fluid and acting as a main axis relative to the proximal end of the conduit (24) so as to form a narrow and variable gap (20), wherein the impact head is symmetrical about a longitudinal axis aligned with the main axis such that the symmetry allows rotation of the impact head. The device provides extended head life and avoids catastrophic head wear in the isolation zone. The product quality of the whole process is better maintained. And the benefits of an automatically unlocking layered device can be realized while maintaining high product quality and consistency. A relatively small change in gap size is sufficient to avoid clogging, such as occurs by the aggregation of large particles or groups of particles in the high shear gap used for stratification.)

1. An apparatus for producing graphene and similar atomic scale layered materials by layering of bulk layered materials; the apparatus comprises a main pump (112) and a core member (10):

the main pump (112) being adapted to pump a fluid at a pressure of more than 1MPa towards the core member (10) and in fluid communication with the core member (10), the fluid being a suspension of solid particles of a bulk laminar material;

the core component (10) comprising a fluid conduit (12), an impact head (16) and an impact head surround (26);

said fluid conduit (12) having a main shaft adapted to convey said fluid, wherein the fluid conduit is arranged to direct fluid under said pressure from the conduit against said impact head (16);

the impact head (16) has an impact surface perpendicular or substantially perpendicular to the main axis; the impact head and the conduit are arranged such that an annular gap (20) of between 500 μm and 1 μm is formed between the end of the conduit proximate the impact head and the impact head, wherein the gap is formed as a continuous region around the conduit end and substantially coplanar with the impact head; and

the impact head surround (26) allows the region in which the fluid is confined to extend before exiting the core component, wherein the impact head is cooled, whereby the device comprises a cooled impact head.

2. The apparatus of claim 1, wherein the apparatus is configured to enable the impact head to maintain a temperature below 50 ℃ at flow rates greater than 1000 liters/hour.

3. The apparatus of claim 2, wherein the apparatus is configured to maintain a temperature below 25 ℃.

4. The apparatus of claim 3, wherein the apparatus is configured to maintain a temperature below 10 ℃.

5. An apparatus according to any preceding claim, wherein the impact head is a diamond impact head.

6. The device according to any one of claims 1-5, further comprising a pressure drop valve (124) downstream of the impact head (16) to provide back pressure.

7. The device according to any one of the preceding claims, wherein the impact head (16) of the device is freely rotatable about the main shaft.

8. The device according to any of claims 1-4, wherein the impact head (16) of the device is configured to be rotatable about a main axis and constrained by a mechanism.

9. The apparatus of any preceding claim, wherein the impact head (16) of the apparatus is configured to be rotatable at a rate of 0.01rpm to 50rpm in use.

10. An apparatus according to any preceding claim, wherein the apparatus is arranged, in use, to recirculate the fluid exiting the core components back to the inlet of the main pump.

11. A method of exfoliating a laminar material by delamination of a bulk material to produce an atomically laminar material; the method comprises the following steps: providing the device of claim 1; passing a liquid suspension of a layered material through the device at the impact head at a pressure greater than 1 MPa.

12. The method of claim 11 wherein the fluid exiting the core components is recirculated back to an inlet of the main pump.

13. The method of claim 11 or 12, wherein the temperature of the fluid is maintained in the range of 30 ℃ to 80 ℃.

14. The method according to any one of claims 11-13, wherein the temperature of the impact head is kept below 50 ℃.

15. The method of claim 12, wherein the temperature of the impact head (16) is maintained below 10 ℃.

16. Use of the device according to any one of claims 1-10 for the preparation of graphene and similar atomic scale layered materials by delamination of bulk layered materials.

Background

Graphene is a two-dimensional allotrope of carbon, consisting of sheets of hexagonal structure of several atoms thick. Analogs of this material may include other chemicals including boron nitride and molybdenum disulfide.

Graphite, a widely used mineral, is actually a crystalline form of graphene in which graphene layers are bonded together by van der waals forces. Since 2004 as an isolating material, graphene has attracted considerable interest. The novel mechanical, thermal and electrical properties of the material suggest many uses. Graphene can be produced on a laboratory scale sufficient for experimental analysis, but commercial quantities are still a developing area of production. Other monolayer structures such as boron nitride are expected to exhibit similar interesting properties in the nanotechnology field.

Min Yi and Zhiging Shen write reviews Of this technology entitled "A review on mechanical evolution for the scalable production Of graphics" Journal Of Materials Chemistry, A,2015,3,11700 outlines the state Of the art with respect to graphene production.

Bottom-up techniques, such as chemical vapor deposition and epitaxial growth, can produce high quality graphene with few defects. The resulting graphene is a good candidate for electronic devices. However, these thin film growth techniques have a limited scale and complicated and therefore expensive production, and cannot meet the requirements for producing industrially relevant quantities of graphene.

The large-scale production of graphene at low cost has been demonstrated using top-down techniques, where graphene is produced by direct exfoliation of graphite, sometimes suspended in a liquid phase. The starting material for this is three-dimensional graphite, which is separated by mechanical and/or chemical methods to reveal graphene sheets several atoms thick.

The original technique used by graphene discoverers, the Scotch Tape method, can be used to prepare high quality and large area graphene sheets. It is limited to laboratory studies and does not appear to be feasible for scaling up industrial production.

The three-roll grinding technique is a method of expanding the scotch tape process, using polyvinyl chloride (PVC) dissolved in dioctyl phthalate (DOP) as an adhesive on a moving roll, which can provide continuous peeling. Although a three-roll mill is a known industrial technology, it is not easy and brings additional complexity to completely remove the residual PVC and DOP to obtain graphene.

High yields of graphene were developed by ultrasound assisted liquid phase graphite exfoliation in 2008 by the three colleges of Dublin (Trinity College Dublin). Starting from graphite powder dispersed in a specific organic solvent, followed by sonication and centrifugation, they obtained graphene dispersions. This method of producing graphene can be scaled up, but one disadvantage is that the resulting suspension has a very low graphene concentration (about 0.01mg/mL), which is not necessarily suitable for mass production.

In addition, the ultrasonic processor can only achieve the high power density required for small volumes, and it is therefore difficult to scale up the process to achieve any economies of scale. A related disclosure can be found in WO2013/010211A 1.

Shear force technique

It is well known that graphite layers have low resistance to shear forces, which makes graphite a useful lubricant. This has been exploited in a number of techniques that use shear forces to exfoliate graphene from graphite.

Ball milling is a common technique in the powder industry and is a method of generating shear forces. A secondary effect is the collision or vertical impact of the balls during the rolling action, which can break the graphene sheets into smaller sheets and sometimes even destroy the crystalline nature of the structure.

Several improvements to ball milling techniques have been attempted, such as wet ball milling with solvent addition, but these techniques still require very long processing times (about 30 hours) and produce a number of drawbacks even if suitable for industrial scale mass production. A related disclosure can be found in WO2012117251a 1.

Some shear force generation techniques use an ion intercalation step before applying shear force to weaken interlayer bonding. This reduces the energy required to exfoliate graphite into graphene, but the resulting graphene can be contaminated with residual ions contaminating the finished product, and the process requires additional time and cost, which reduces the industrial application of the technology.

A fluid dynamics based approach has recently emerged for graphite exfoliation. These are based on mixing graphite in powder or flake form with a fluid to form a suspension, which can then be subjected to turbulent or viscous forces, which exert shear stress on the suspended particles. Typically, the fluid is a liquid of the type commonly used as a solvent, and it may include a surfactant mixture suitable for removing the solvent from the finished product.

One method of creating shear is to use high shear forces, such as a rotary mixer. Graphene exfoliation has been demonstrated using a kitchen blender to generate shear forces on graphite particles in suspension. The process has been scaled up using commercial high shear mixers, including rotating blades passing near a mesh screen to generate high shear. Due to the difference in velocity of the mixing blades and the static shear screen, the graphite particles are subjected to shear forces exerted by the fluid. Related disclosures may be found in WO2012/028724a1 and WO2014/140324a 1.

Another method is to use a high pressure homogenizer with a microfluidizer. In this case, the microfluidizer consists of channels having microscale dimensions, meaning about 75 μm. High pressure is used to force fluid from the inlet to the channel. This technique is derived from the treatment of fluids for the production of milk, as disclosed for example in EP0034675, US8585277B2 and WO2016174528a1, but this device is not suitable for use with suspended solids, since this would lead to clogging and high wear rates, since milk production plants for the homogenization of fluids are a different technical problem in terms of engineering. Due to the narrow dimensions of the channels, viscous friction between the walls and the bulk flow generates high shear forces, which leads to graphite delamination. This process requires very high pressures and the starting graphite must have been crushed to the micron size range. A related disclosure can be found in WO 2015/099457.

Further variations can be found in Nacken, SC Advances,2015,5, 57328. Here, the fluid is discharged through the nozzle into the void against the valve, creating a back pressure to avoid cavitation in the expansion chamber. Here, a material such as graphene delaminates as the fluid exits the nozzle into the expansion chamber.

To accomplish a surface-analogous technique as described in WO 2004/052567. Where the solid suspension collides with a rotating disk, the disk rotating at high rpm accelerates the suspension outward to impact a collision ring spaced from the edge of the disk with high force. The high rotational speed and the grooves in the drive disc mean that there is a relatively large gap (mm instead of μm) at the inlet and outlet of the disc to allow vibration of the disc, particularly at acceleration and deceleration, through the resonant frequency (between 0 and 40000 rpm). The additional generation of insufficient shear stress, or the possible absence of voids, means that such devices are not suitable for delaminating layered materials.

There is a need for a graphene production process that can produce graphene using less energy, which can be scaled up to high production rates without losing the quality of the final product. Such devices are disclosed in co-pending patent applications GB15181.5 and PCT/GB 2016/053177. The apparatus provides a fluid conduit for impacting a particle suspension to be delaminated against an impact head having an impact face and an annular gap. In practice it has been found that the device has a limited lifetime before maintenance is required, since the annular gap may become clogged with particulate material and/or worn, providing an uneven gap through which the suspension flows preferentially and which in turn makes the gap larger. While these two problems tend to be mutually exclusive, this is not necessarily so. When new suspension is introduced, i.e. larger particles and unworn head, clogging tends to occur. This type of wear tends to occur after prolonged use and can create paths of least resistance through which larger particles can escape but with poor stratification. If the purpose of the apparatus is for industrial scale layering of layered material suspensions, for example for the production of graphene from graphite, and the industrial production requires long operation times (e.g. several days or hours of operation), it would be desirable to provide an improved apparatus. This application mainly addresses the problem of wear.

The present invention seeks to overcome the problems of the prior art to provide a fast, scalable to industrial volume and energy efficient graphene apparatus and production method.

Definition of the invention

Various aspects of the invention are as set out in the appended claims.

In a first aspect, the present invention provides:

an apparatus for producing graphene and similar atomic scale layered materials by delaminating a bulk layered material, such as graphite; the apparatus comprises a main pump (112) and a core member (10),

the main pump (112) being adapted to pump fluid at a pressure greater than IMPa towards and in fluid communication with the core member, the fluid being a suspension of solid particles of a bulk laminar material;

the core component (10) comprising a fluid conduit (12), an impact head (16) and an impact head surround (26),

said fluid conduit (12) having a main axis and being adapted to convey said fluid, wherein the fluid conduit is arranged to direct fluid under said pressure from the conduit against said impact head (16);

the impact head (16) has an impact surface perpendicular or substantially perpendicular to the main axis; the impact head and the conduit are arranged such that an annular gap (20) of between 500 μm and 1 μm is formed between the end of the conduit proximate the impact head and the impact head, wherein the gap forms a continuous region around the conduit end and substantially coplanar with the impact head;

the impact head surround (26) extends the confined area before the fluid exits the core component, wherein

The impact head is symmetrical about a longitudinal axis, which coincides with said main axis, is adapted to convey said fluid and this symmetry allows the impact head to rotate.

Suitable symmetries will thus include that the impact head is cylindrical and/or (frusto-) conical or consists of cylindrical and/or (frusto-) conical sections. The symmetry is preferably radial symmetry about the main axis. This is because asymmetric devices such as shown in WO2015/099378 provide less uniform product layering. This is believed to be because there are various ways of passing through high shear fields. Also, the low turbulence areas collect solid deposits from the fluid, which can lead to clogging and plugging. This occurs gradually, especially when the flow rate is changed (e.g., at start-up), the deposit cake can move and clog the flow path and require equipment stripping and cleaning.

Preferably, the solid particles are graphite, hexagonal boron nitride or molybdenum disulphide particles. Most preferably, the solid particles are graphite.

The fluid may be a suspension, preferably having a particle size in the range of 1 μm to 1000 μm. The suspension is preferably an aqueous suspension.

The advantages and capabilities of this general type of device are disclosed in co-pending uk patent application GB 15181.5. It has been found that the device is capable of delaminating graphite and similar layered materials at pressures and energy levels lower than those required for microfluidizers. This has the additional advantage of reducing heat build-up in the process.

The annular gap is very advantageous for providing a consistent product, arranged (substantially) vertically and within the narrow band of the pneumatic adjustment movement. Thus, substantially perpendicular includes at most a 10 ° offset, preferably no more than 1 °, and most preferably no more than 0.1 °. This offset may be conical.

However, consistent product quality may not be achieved after prolonged use, sometimes not exceeding several hours. As can be seen from the exaggerated example in fig. 6, weak points in the impact head can cause local erosion and the annular gap can become non-uniform, creating a larger sized local channel, which can wear down to the extent shown in fig. 1, during which the product quality rapidly degrades as the amount of suspension passing through the required shear/impact conditions of the equipment is reduced and the pressure drop over the impact head is also reduced.

It has been found that providing an impact head that is symmetrical about a longitudinal axis and that conforms to a main shaft adapted to convey the fluid overcomes the problem of selective wear. Preferred forms of symmetry are represented by cylindrical and/or (frusto-) conical. A portion of the impact head may be asymmetric to control rotation in cooperation with the mechanical axis, provided that the degree of symmetry present is required to enable rotation of the impact head in the device.

It appears that there is symmetry enabling the rotation of the head in the device, such a symmetrical head allowing a certain degree of rotation for even wear. This is surprising because in the initial view the rotatable head should rotate to give the maximum aperture size in order to relieve the incoming pressure and therefore local wear should be exacerbated. However, while not wishing to be bound by theory, it is speculated that the high turbulence in the device generates non-linear forces and may be combined with vibrations. This means that the force causing the head to rotate may exceed the force that preferentially orients it to provide maximum clearance.

The effect of this rotational capability due to the symmetry of the impact head with respect to the incoming fluid can be seen by operating the replacement head for a similar length of time, as shown in fig. 7. Some evidence suggests local wear in the range of about 50 deg., as indicated by the lighter color, but this is by no means the extent shown in fig. 1, where local wear is understood to widen rapidly to provide the notch shown.

The impact head of the device can rotate freely around the main shaft. As mentioned above, this has proven to be effective.

In designing the device, the impact head is seated in a housing (not shown in the schematic for clarity). The fit of the impact head in the housing will be determined by the skilled person in order to allow rotation but also to provide dimensional stability, for example to stop potentially damaging asymmetric rotations at the high pressures involved. Similarly, larger fit tolerances may allow excessively rapid rotation and cause lateral wear of the impact head and consequent leakage and loss of fit. Wording is here used in an engineering sense. In particular, ISO is an internationally recognized standard for defining engineering fits, but ANSI is used in north america.

The two groups of ISO and ANSI are divided into three groups: gaps, transitions and disturbances. There are several codes in each category to define the size limits of the holes or axes-the combination of which determines the type of fit. The mating is selected at the design stage depending on whether the mating parts need to be precisely positioned, slide or rotate freely, be easily separated or resist separation. In the present case, the impact head and housing fit falls into a free sliding or rotating class of clearance fit. This allows the design engineer to select the appropriate tolerances for any given material combination. As a guide, the preferred clearance fit is:

easy-to-operate clearance fit-medium clearance, minimum accuracy requirements-e.g. high operating speed, ISO286-2H 9/e9

Close running clearance fit-small clearances, moderate accuracy requirements-e.g. moderate running speeds, ISO286-2H 8/f7

Sliding clearance fit-minimum clearance, meets high precision requirements, can be easily assembled, can freely rotate and slide, ISO286-2H7/g6

Positioning clearance fit-very tight clearance, can meet precise accuracy requirements, can be assembled without force, and rotates and slides during lubrication, ISO286-2H 7/H6.

In practice, it has been found that sliding and positioning are preferred because the large forces present at the required pressures above IMPa and the required gap between 500 μm and 1 μm in the present invention allow sufficient rotational force to be applied by turbulent flow while maintaining. Particularly when these tolerances are used. If there is a question, an "H" ISO tolerance is preferred. The practical considerations discussed above have kept the device away from techniques such as that found in WO2004/052567, where there are gap sizes in the order of mm.

The impact surface of the impact head may be symmetrical. This is preferred, for example to cause the impact head to rotate and thus be more prone to even wear, since asymmetry has not been found to be beneficial, in practice local wear does occur (e.g. if there is a notch) or, if configured to cause rotation, the high pressure of the device creates such a degree of rotation that rotation, chatter and wear of the orifice in which the impact head is located may occur. In particular, it appears that a fully symmetrical impact head on a surface located in the housing, though a clearance fit, should not rotate, but in practice may rotate due to turbulence in the fluid flow and/or vibration of the device. The induced rotation is preferably 0.05 to 50 revolutions per minute (rpm), preferably 0.1 to 10 rpm. For any given device, some trial and error may be required to achieve this, for a given bulk laminar material, at a given pressure, without exceeding the trial and error of testing a narrow range fit.

However, it is also envisaged that the impact head (16) of the device is configured to be rotatable about the main shaft and constrained by the mechanism. The mechanism may for example be a shaft having a drive rate, for example in the range described above. But this is not preferred as it creates additional complexity and may be difficult to implement in view of the forces and pressures involved. However, it is a mechanism that avoids the trial and error method described above, thus allowing a wider range of feedstocks and pressures for a given plant set-up.

In summary, the impact head of the device of the invention can be used rotatably. The term will be interpreted by the skilled person to mean that rotation may occur under the action of an operating force. This does not mean that the head must be free to rotate or be able to be moved by hand or even with a simple tool, for example when not in operation, for example in an equipment hole in which an impact head can be accommodated, as the clearance of the components is tight. If leakage between the head and the housing may be a problem for a given impact head in the housing, an O-ring seal may be used to prevent this.

The impact head of the present invention may be combined with a pneumatic adjustment mechanism so that the gap in the device varies according to the pressure exerted by the incoming fluid during use. This is advantageous because, in addition to the rotational movement, an axial movement can also take place in order to be able to clear any blockage in the gap.

The impact head may comprise a common engineered material, such as steel. This is not surprising since the prior art discloses that all use steel or stainless steel equipment, considering that graphite and graphene are good lubricants. In particular, the graphite has a hardness (mohs hardness) of 1 to 2 and a hardness (vickers hardness) of VHN10 ═ 7 to 11kg/mm²In contrast, conventional 4-4.5 hardness (mohs hardness) steels compared to high speed steels, VHN10 ═ 7-11kg/mm². However, we have surprisingly found that harder impact head materials provide greater throughput. While not wishing to be bound by theory, it is believed that for harder materials, the impact head is less elastic and therefore peels more effectively. However, chromium with a hardness (mohs hardness) of 8.5 is not necessarily better than steel (wear and abrasion with high quality graphite is not an issue), and alumina, silicon nitride, tungsten carbide, silicon carbide, boron nitride and diamond are preferred. In particular, diamond is most preferred. While not wishing to be bound by theory, it appears that the energy of interaction between diamond and graphite (both carbon materials) is minimal, but the difference in the crystal structure of diamond and graphite creates the necessary hardness.

It has been found that the apparatus of the present invention is more efficient when the impingement head is cooled. It is not entirely clear why this occurs because the viscosity of the fluid should be greater at low temperatures. The apparatus of the present invention preferably comprises a cooled impact head, the apparatus preferably being configured such that the impact head can be maintained at a temperature below 50 ℃ at a flow rate of greater than 1000 litres/hour. Preferably less than 25 c and most preferably less than 10 c. It has been found that the most effective surface cooling of the impact head can be obtained using a diamond impact head.

In a second aspect, the invention therefore also includes the use of the apparatus described herein for the preparation of graphene and similar atomically layered materials by delamination of bulk layered materials, such as graphite.

Method of the invention

In a third aspect, the present invention provides a method of exfoliating a laminar material to produce an atomically laminar material by delamination of a bulk material; the method comprises the following steps: providing an apparatus as hereinbefore described and passing a liquid suspension of the layered material through the apparatus, wherein in operation the impact head is allowed to rotate or is forced to rotate.

This has the effect of balancing the wear on the impact head, thereby avoiding local wear which forms a preferential flow path and therefore causes further local wear. Surprisingly, the rotation achievable by providing an axially symmetric part (e.g. a cylinder or cone) in which the rotation is not actively forced to rotate by an external mechanism, no external driving force being provided, e.g. by a mechanical linkage, has proven to be sufficient to substantially mitigate the problem of local wear. Providing an external mechanical driving force ensures that more even wear occurs and can be used if the cost of additional mechanical complexity is acceptable in a given situation.

In the method of the present invention, the layered material is preferably graphite, and the atomic-scale layered material is graphene.

The liquid in which the layered material is suspended is preferably water. Water is preferred because it has a high specific heat capacity, which enables the process to be operated at temperatures in the range of 30 ℃ to 80 ℃. In addition, the aforementioned local head temperature is preferably lower than room temperature (in particular lower than 10 ℃), which is easier to maintain with water as the liquid. Other suitable liquids are liquid hydrocarbons.

The process of the invention is preferably operated at a temperature of from 30 ℃ to 80 ℃.

The particle size range of the graphite is preferably from 1 μm to 1000 μm, more preferably from 3 to 50 μm, most preferably from 15 to 25 μm. The dimensions may be determined using a Malvern Mastersizer using D4, 3 particle size measurement.

The layered material, preferably graphite, loaded in the liquid phase is preferably in the range of up to 500 grams per liter (g/l). More preferably, the loading of the layered material is from 10 to 125g/l, most preferably 125 g/l.

The fluid of the invention impacts the impact head at a pressure greater than IMPa, more preferably at a pressure of from 10MPa to 150MPa, more preferably at a pressure of from 40MPa to 100MPa, most preferably at a pressure in the range of from 50MPa to 70 MPa. Pressure selection can provide optimum yield, productivity and energy consumption.

It has surprisingly been found that instead of simply having a higher pressure the better, which may result in a higher impact force on the impact head, an optimal pressure range is found. This optimal range provides the highest quality laminate, such as graphene. While not wishing to be bound by theory, it is believed that excessive system energy causes the laminate to rupture. Thus, there is an optimum pressure range for a system configured with an impact head so that solids in the fluid are laminated (peeled off) while the peeled laminar sheet is not excessively damaged.

The process of the present invention preferably comprises a fluid in which the surfactant is present. Suitable surfactants include sodium alkyl benzene sulphonate and tetrabutylammonium chloride. The preferred surfactant is sodium cholate.

The surfactant is preferably an anionic or cationic surfactant which can be neutralised to remove its anionic or cationic character respectively, so that the surfactant can be easily removed from the fluid. Thus, the process of the invention optionally comprises the following neutralization step: the fluid resulting from the process is taken, which comprises an anionic or cationic surfactant and the resulting fluid comprising sheets of layered material, preferably graphene, and the surfactant is neutralised before washing the surfactant from the sheets, which may precipitate in the process, to produce a composition consisting of sheets of layered material.

The process of the present invention preferably comprises a filtration step wherein particulate material is removed by said filtration step (using any mechanism). The filtration step may preferably be performed after the neutralization step.

The present invention also includes a second aspect of using a high pressure homogenizer, for example of the type disclosed with respect to the drawings, for the preparation of graphene from graphite in aqueous suspension.

The conditions and parameters associated with the method of the invention are also applicable to the configuration of the apparatus of the invention. Unless otherwise stated, the temperature is 25 ℃ and the atmospheric pressure is 1 atm.

DETAILED DESCRIPTIONS

The apparatus of the present invention will now be described by way of the following figures, in which:

FIG. 1 shows a schematic view of the fluid path through the device of the present invention and shows the core member;

figure 2 shows a schematic cross-sectional view of a first arrangement of core parts of the inventive device;

figure 3 shows a schematic cross-sectional view of a second arrangement of core parts of the inventive device;

figure 4 shows a schematic cross-sectional view of a second arrangement of core parts of the inventive device;

fig. 5 shows a schematic view of the system or apparatus of the invention comprising a core component and an auxiliary component to provide an optimal handling system for performing the method of the invention.

Fig. 6 shows an impact head that is damaged and rotationally constrained during prolonged use.

Fig. 7 shows an impact head that suffers minimal wear and is not rotationally constrained over extended use.

The chart provides the following features:

10 assembly of core parts;

12 fluid conduits/volumes;

14 into the fluid conduit at a point remote from the impact head;

16 a percussion head assembly;

18 an optional face (impact face) of the impact head assembly;

20 rings/ring gaps;

202 frustoconical ring/frustoconical annular gap;

204 outer ring/outer ring gap;

22 support structure:

24 an outlet of the fluid conduit proximate the impact head/conduit proximal end;

242 proximal end of tubing, alternative forms;

26 impact head surround;

28 impact the head face;

32 pipes/tubes; (FIG. 5 below).

100 systems or (expansion) devices of the invention;

110 a raw material container;

112 a high pressure pump;

114 a valve;

124 a pressure reducing valve;

116 a finished container;

118 water chiller/cooler.

Referring to figures 1 to 4, in use, the apparatus of the present invention has fluid pumped from a pump 112 through conduits 32 and 12 in the form of tubes, the conduits 32 and 12 being end portions of the core assembly 10. Core assembly 10 has proximal end 24 of tube 12/32, wherein fluid in the volume of pipe 12 exits the pipe under pressure to impact head 16, which impact head 16 may have a hard material face 18; when the fluid strikes the surface of the impact head, it passes through the annular space 20 defined between the surface 28 of the impact head and the proximal end of the conduit 24, and then exits the core components, for example, to be recycled or recovered as a finished product. In the particular figure, a further impact head surround 26 is provided to extend the region of fluid confinement prior to exiting the core components in use. The impact head 16 of the device is configured to be movable relative to the proximal end of the conduit 24 so that the definition of the annular gap 20 can be achieved.

In figure 3, the proximal end of the conduit 242 has an internal bevel such that, in use, fluid passing through the core member from the volume of conduit 12 is accelerated in the annular space (now frusto-conical) until the pinch point is reached, creating maximum shear forces.

In fig. 4, the proximal end of the conduit 24 does not abut the impact head barrier and provides an outer annular region 204 in which turbulent flow can occur to improve processing. Outer annular region 204 is presented in fig. 3 with an inner inclined surface, fig. 3 may be provided without region 204.

Referring to fig. 5, the treatment system of the present invention comprises a core component 10 as previously described. The system is configured such that the feedstock is provided in a vessel 110 and pumped by a high pressure pump 112 into a conduit 12/32, into the core components 10, particularly the impact head 16, and then out to an optional pressure drop valve 124, thereby providing back pressure to the core components to improve processing. The system is further configured such that the fluid then passes as a finished product through the directional control valve 114 to the product container 116, or through recirculation through a cooler 118 into the high pressure pump 112 for optional recirculation.

Experiment of

The apparatus of the invention comprises a 3kW impeller pre-pump at 400kPa output, a 30kW multi-piston main pump fed, graphite suspension with an average particle size of 20 μm and 100g/l graphite solid particles pumped, a pressure of 60MPa (+/-1MPa), a flow rate of 1200 litres/hour along a fluid conduit having a main axis, and a cylindrical impact head having an end impact surface perpendicular to said main axis. The cylinder is 15mm in diameter and 25mm in length and is located in a corresponding bore in the housing (itself a 20cm long cylinder) which receives a 15mm cylindrical impact head. The gap was set to 5 μm. The suspension was initially at a temperature of 20c, maintained at a temperature of 30 c by cooling and then recycled back to the apparatus. The recirculation loop has 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 a housing according to ISO286-2H 7. The head is lightly scored and has a mark on the side of the cylinder and aligned with a similar mark in the housing. The machine was run for 15 minutes. The foregoing are runs 1 and 4. The experiment was repeated with fresh suspension and the head was sealed in place with epoxy adhesive to stop rotation and fill the ISO286-2H7 gap, realigning the marks. These are runs 2 and 3.

As a result:

it is believed that head movement serves to prevent clogging by breaking and removing material before significant back pressure is created. Clogging was also indirectly evidenced by the visual residue on the equipment upon disassembly. While plugging can be avoided by using finer starting materials, this requires a pretreatment run to reduce the feedstock size and convert the continuous process to a less efficient batch process. Since the apparatus will be run with two gap sizes, larger gaps can also be used, which will result in longer processing times. The degree of rotation is not known from the above. However, from other experiments, a rotation rate of about 10rpm was inferred in run-check-run, etc. Run 5 is equal to run 1. The products of runs 1 and 4 included graphene.

The present invention provides a device that is more resistant to plugging when used with suspended solids that are capable of delaminating. A possible reason is that solids that are not laminar will not be broken up as easily by the rotating head.

Pressure herein is a pressure above atmospheric pressure. Unless otherwise stated, the temperature herein is 20 ℃.

The preferred embodiment of the invention is:

1. an apparatus for producing graphene and similar atomic scale layered materials from layered bulk layered materials; the apparatus comprises a main pump (112) and a core member (10),

the main pump (112) being adapted to pump fluid at a pressure greater than IMPa towards and in fluid communication with the core member (10), the fluid being a suspension of solid particles of a bulk laminar material;

the component (10) comprises a fluid conduit (12), an impact head (16) and an impact head surround (26):

a fluid conduit (12) having a main shaft adapted to convey the fluid, wherein the fluid conduit is arranged to direct fluid under the pressure from the conduit against an impact head (16);

the impact head (16) has an impact surface perpendicular or substantially perpendicular to the main axis; the impact head and the conduit are arranged such that an annular gap (20) of between 500 μm and 1 μm is created between the end of the conduit proximate the impact head and the impact head, wherein the gap forms a continuous region around the end of the conduit and substantially coplanar with the impact head; and

an impact head surround (26) extends the confined region of the fluid prior to exiting the core component, wherein,

the impact head is symmetrical about a longitudinal axis coincident with the main axis, and the symmetry allows the impact head to rotate.

2. The apparatus of embodiment 1 further comprising a pressure drop valve (124) downstream of the impact head to provide back pressure.

3. The apparatus of embodiment 1 wherein the arrangement between the impact head face and the main axis is 1 ° or less from vertical.

4. The device according to any preceding embodiment, wherein the impact head (16) of the device is movable along the main axis relative to the proximal end of said duct (24) to adjust said annular gap (20).

5. The device according to any preceding embodiment, wherein the impact head (16) of the device is freely rotatable about the main shaft.

6. The device according to any of embodiments 1 to 4, wherein the impact head (16) of the device is configured to be rotatable about a main axis and constrained by a mechanism.

7. The device according to any preceding embodiment, wherein the proximal end of the conduit (242) has an internal inclined surface such that the annular gap is frusto-conical, whereby in use fluid is transferred from the volume of the conduit (12) through the core member, accelerating until a minimum height of the annular gap is reached to generate maximum shear forces.

8. The device 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.

9. The apparatus according to any preceding embodiment, wherein the proximal end of the conduit (24) does not abut the impact head surround (26) and provides an outer annular region (204).

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

11. The apparatus according to any preceding embodiment, wherein the impact face (18) of the impact head (16) comprises diamond.

12. A method of exfoliating a laminar material to produce an atomically laminar material by layering of a bulk material; the method comprises the following steps: providing the apparatus described in example 1; the liquid suspension of the layered material is passed through the apparatus at the impact head at a pressure greater than 1 MPa.

13. The apparatus or method according to any preceding embodiment, wherein fluid exiting the core components is recirculated back to the inlet of the main pump.

14. The apparatus or method according to any preceding embodiment, wherein the temperature of the fluid is maintained in the range of 30 ℃ to 80 ℃.

15. The apparatus or method according to any preceding embodiment, wherein the temperature of the impact head is maintained below 50 ℃.

16. The apparatus or method according to embodiment 15, wherein the temperature of the impact head (16) is maintained below 10 ℃.

17. The method or apparatus of any preceding embodiment, wherein the fluid impinges on the impact head (16) at a pressure of 10MPa to 150 MPa.

18. The method or apparatus of any preceding embodiment, wherein the fluid impinges on the impingement head at a pressure of 50MPa to 70 MPa.

19. The method or apparatus of any preceding embodiment, wherein the fluid impinges on the impingement head at a flow rate greater than 1000 liters/hour.

20. The method or apparatus according to any preceding embodiment, wherein the layered material is loaded in the liquid phase in a range of up to 500 grams per liter (g/l).

21. Use of the apparatus of any one of embodiments 1 to 11 for the preparation of graphene and similar atomically layered materials by delamination of bulk layered materials.

22. Use of the apparatus of any one of embodiments 1 to 11 for the preparation of graphene and similar atomically layered materials, wherein the solid particles are particles of graphite, hexagonal boron nitride or molybdenum disulphide.

23. Use of the apparatus of any one of embodiments 1 to 12 for the preparation of graphene from an aqueous graphite suspension.