CN108069417B

CN108069417B - Airflow generation device, graphene dispersion liquid and preparation method thereof

Info

Publication number: CN108069417B
Application number: CN201710350845.7A
Authority: CN
Inventors: 吴定宇; 张廷宇; 李欣錞; 林勃汎
Original assignee: Taiwan Textile Research Institute
Current assignee: Taiwan Textile Research Institute
Priority date: 2016-11-16
Filing date: 2017-05-18
Publication date: 2020-06-09
Anticipated expiration: 2037-05-18
Also published as: CN108069417A

Abstract

The invention provides an airflow generation device, a graphene dispersion liquid and a preparation method of the graphene dispersion liquid. The graphene dispersion liquid is prepared from graphene powder and a processing solvent, the average sheet diameter of graphene in the graphene dispersion liquid is 0.5-1 mu m, the number of layers is 3-5, the solid content is 5-50%, the surface oxygen content is less than 1 wt%, the distribution concentration of the graphene dispersion liquid is gradually increased from the upper layer to the bottom layer after the graphene dispersion liquid is stood for 12 hours, the viscosity is 5000-8000 cps, and the graphene concentration is 20 wt%.

Description

Airflow generation device, graphene dispersion liquid and preparation method thereof

Technical Field

The invention relates to an airflow generating device, graphene dispersion liquid and a preparation method of the graphene dispersion liquid, in particular to an airflow generating device for preparing low-oxygen graphene powder, graphene dispersion liquid and a preparation method of the graphene dispersion liquid.

Background

The graphene has a structure represented by sp from a carbon atom²The two-dimensional structure is formed by covalent bonds, and has special properties of high carrier mobility, hardness, thermal conductivity, current carrying capacity, extremely high surface-to-volume ratio and the like. Therefore, in recent years, graphene has been a target of research with high importance in the fields of biomedicine, electronic and optoelectronic devices, and the like. Meanwhile, the graphene dispersion can be widely appliedThe graphene oxide nano-composite material is used in the field of coatings, and is an important additive in products such as conductive coatings and related conductive aids, lithium ion electrode conductive aids, anticorrosive coating aids, graphene temperature-equalizing sheets and the like.

However, in the existing graphene dispersion liquid preparation technology, the chemical treatment process has the problems of wastewater pollution and toxic waste exhaust such as acid-base and heavy metal waste liquid, and the physical methods such as mechanical stripping method, ultrasonic oscillation or ball milling method have the defects of low solid content, low yield, uneven distribution of the sheet diameter and thickness of the product, and the like. In addition, most of the graphene dispersion liquid which is commonly sold at present has low solid content, and excessive solvent seriously affects the physical properties and the processability of subsequent resin, so that the application of the graphene dispersion liquid in the field of coating is not facilitated. In addition, the common technology for improving the suspension property of the graphene is surface modification or addition of a dispersing aid (more than 5%), and both methods can greatly reduce the physical property of the graphene and even improve the manufacturing cost of the graphene dispersion liquid.

Based on the above, a graphene dispersion solution that can meet the environmental protection requirement, increase the solid content, increase the yield, improve the suspension property, homogenize the product specification, and reduce the manufacturing cost is developed, which is an important subject of the current research.

Disclosure of Invention

The invention provides an airflow generating device for preparing low-oxygen graphene powder, graphene dispersion liquid and a preparation method of the graphene dispersion liquid. Therefore, the high-concentration graphene dispersion liquid with specific concentration variation can be prepared, the environment-friendly requirement is met, the solid content can be remarkably improved, the yield is increased, the suspension property is improved, the specification of a uniform product is improved, and the manufacturing cost of the graphene dispersion liquid can be greatly reduced.

The airflow generating device comprises an outer bushing and a rotating awl. The outer liner is provided with a cavity, an air inlet opening and an air outlet opening, the air inlet opening is communicated with the lower part of the cavity, the air outlet opening is communicated with the upper part of the cavity, and the cavity is provided with a necking part. The rotating awl is arranged in the cavity, the rotating awl is matched with the cavity, a slit interval is formed between the rotating awl and the inner wall of the cavity, the rotating awl comprises a rotating body and a plurality of threads, and the threads are spirally distributed on the outer surface of the rotating body from the bottom of the rotating body to the top of the rotating body. When the rotating awl rotates in the chamber, a cyclone is generated with a component in an upward and horizontal direction by the threads and the slit spacing.

In one embodiment of the invention, the top surface of the rotating awl is flush with the top surface of the constriction.

In an embodiment of the present invention, the rotating body includes a bottom portion, a top portion and a middle portion located between the bottom portion and the top portion, wherein the diameter of the rotating body decreases from the bottom portion to the top portion sequentially. Further, the bottom surface of the bottom portion has a diameter larger than the top surface of the bottom portion. Furthermore, the diameter of the bottom surface of the middle part is larger than the diameter of the top surface of the middle part, and the diameter of the bottom surface of the middle part is equal to the diameter of the top surface of the bottom part. The diameter of the bottom surface of the top part is larger than that of the top surface of the top part, and the diameter of the bottom surface of the top part is equal to that of the top surface of the middle part.

In an embodiment of the present invention, the section of the rotating awl is in a star-shaped manner.

In an embodiment of the present invention, the rotation speed of the rotating awl is in a range from 3000rpm (rotation(s) PerMinute per minute) to 7000 rpm.

In an embodiment of the present invention, the number of threads ranges from 8 to 32; and in another embodiment, the number of threads is between 12 and 18.

In an embodiment of the present invention, the slit pitch ranges from 0.05 mm to 10 mm; and in another embodiment, the slit pitch ranges from 0.1 mm to 1 mm.

The preparation method of the graphene dispersion liquid comprises the following steps. And carrying out a homogenization process on the graphene powder and the treatment solvent to form the graphene paste. And then, carrying out a thin-layer process on the graphene paste to form a graphene dispersion liquid, wherein the graphene powder is prepared by using the airflow generating device.

In an embodiment of the present invention, a method for preparing graphene powder includes the following steps. The graphite material is continuously rolled at high speed to prepare a graphite precursor, and the graphite precursor has a dislocation slip structure. And then, carrying out intercalation reaction on the graphite precursor by compressing airflow in the horizontal direction to form the graphene and gas interlayer compound. Then, graphene and a gas interlayer compound are subjected to an expansion exfoliation reaction by interlayer gas flow pressure release to form a graphene aggregate. Then, the graphene aggregates are floated in suspension in the gas flow and collide with each other to produce graphene powder.

In one embodiment of the present invention, the spacing between layers in the graphite precursor is

To

In an embodiment of the present invention, the wind speed of the compressed airflow in the horizontal direction is from mach 0.3 to mach 1.

In one embodiment of the invention, the volume of the horizontal compressed air stream is 186CMM to 619 CMM.

The graphene dispersion liquid is prepared from graphene powder and a processing solvent by using the preparation method of the graphene dispersion liquid, the average sheet diameter of graphene in the graphene dispersion liquid is 0.5-1 mu m, the number of layers is 3-5, the solid content is 5-50%, the surface oxygen content is less than 1 wt%, the distribution concentration of the graphene dispersion liquid is gradually increased from the upper layer to the bottom layer after standing for 12 hours, the viscosity is 5000-8000 cps, and the concentration of the graphene is 20 wt%.

In an embodiment of the present invention, the difference between the concentrations of the upper layer and the bottom layer in the graphene dispersion is 0.1 wt% to 20 wt%.

In an embodiment of the invention, the number of layers of the graphene powder is 5 to 10.

In an embodiment of the invention, the average sheet diameter of the graphene powder is 3 μm to 15 μm.

In an embodiment of the present invention, the surface oxygen content of the graphene powder is less than 0.1 wt%.

In one embodiment of the present invention, the treatment solvent includes a hydrocarbon solvent, a halogenated hydrocarbon solvent, an alcohol solvent, a phenol solvent, a ketone solvent, an ether solvent, an acetal solvent, an acid anhydride solvent, a nitrogen compound solvent, a sulfur compound solvent, a polyfunctional group solvent, or an inorganic solvent.

In one embodiment of the invention, the treatment solvent has an interfacial tension in the range of 15mN/m to 50mN/m and a Hansen solubility parameter of 5.0MPa^0.5To 15MPa^0.5。

In an embodiment of the invention, the graphene powder is added in an amount of 0.001 wt% to 30 wt% based on the total weight of the graphene dispersion.

Based on the above, the airflow generation device of the present invention utilizes the direct continuous physical method to make the graphite raw material into the graphene powder with low oxygen content, and the graphene powder has the characteristics of fixed layer number, consistent sheet diameter characteristics, easy homogenization under low energy, no structural damage caused by oxidation, and the like. Meanwhile, the graphene dispersion liquid prepared by the graphene powder has the advantages of high yield, high solid content, adjustability of a solid content measuring tool and the like, so that the problems of low solid content and low solvent selectivity of a commercially available graphene dispersion liquid can be solved, the processability and the adaptability of different coating processes can be improved, and the application in the field of coatings is facilitated.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a sectional view of an airflow generating apparatus.

Fig. 2 is a perspective view of the rotating awl of fig. 1.

FIG. 3A is a schematic view of the top and bottom surfaces of the top of the awl.

FIG. 3B is a schematic view of the top and bottom surfaces of the middle portion of the rotating awl.

FIG. 3C is a schematic view of the top and bottom surfaces of the bottom of the rotating awl.

Fig. 4 is a schematic flow chart of a method for manufacturing graphene powder.

Description of the reference numerals

100: airflow generating device

108: slit spacing

110: outer liner

112: chamber

112 a: necking part

114: air inlet opening

116: air outlet opening

120: rotary awl

122: rotating body

124: screw thread

1221: bottom part

1222: top part

1223: middle part

120a, 112b, 1221b, 1222b, 1223 b: the top surface

1221a, 1223a, 1222 a: bottom surface

130: screening device

S: space(s)

S110, S120, S130, S140: step (ii) of

θ 1, θ 2, θ 3: angle of rotation

Detailed Description

The invention provides an airflow generating device for preparing graphene powder, graphene dispersion liquid and a preparation method of the graphene dispersion liquid. Hereinafter, details of the gas flow generating apparatus, the graphene dispersion liquid, and the method for preparing the same according to the present invention will be described in detail.

< airflow generating apparatus >

Fig. 1 is a sectional view of an air flow generating device, and fig. 2 is a perspective view of the rotating awl of fig. 1. Referring to fig. 1 and fig. 2, the airflow generating apparatus 100 includes an outer liner 110 and a rotating awl 120, wherein the outer liner 110 has a cavity 112, an air inlet opening 114 and an air outlet opening 116. The inlet opening 114 is connected to the lower portion of the chamber 112 and the outlet opening 116 is connected to the upper portion of the chamber 112, and the chamber 112 has a necking portion 112 a. The rotating awl 120 is disposed in the cavity 112 in conformity with the cavity 112 with a slit gap 108 between the rotating awl 120 and an inner wall of the cavity 112, wherein the rotating awl 120 includes a rotating body 122 and a plurality of threads 124, and the threads 124 are spirally distributed on an outer surface of the rotating body 122 from a bottom 1221 of the rotating body 122 toward a top of the rotating body 122.

In one embodiment, the number of the threads 124 may be between 8 and 32, and in another embodiment, the number of the threads 124 may be between 12 and 18. The number of threads 124 is not limited by the description herein, and the designer may vary the number of threads 124 according to actual needs, with consideration of other factors. In addition, the top surface 120a of the rotating awl 120 is flush with the top surface 112b of the necked down portion 112a of the chamber 112.

Fig. 3A is a schematic view of the top and bottom surfaces of the top of the rotating awl, fig. 3B is a schematic view of the top and bottom surfaces of the middle of the rotating awl, and fig. 3C is a schematic view of the top and bottom surfaces of the bottom of the rotating awl. Referring to fig. 3A, 3B and 3C, the rotating body 122 may be divided into a bottom 1221, a top 1222 and a middle 1223 between the bottom 1221 and the top 1222, and since the thread 124 is formed on an outer surface (not labeled) of the rotating body 122, the rotating body 120 is taken as a cross section along a circumferential direction of the rotating body 120, and a cross section of the rotating body 120 is substantially shaped like a star burst. The depth and width of the thread 124 can be set according to practical requirements.

As described above, the diameter of the rotating body 122 decreases from the bottom 1221 to the top 1222. Further, the bottom surface 1221a of the bottom portion 1221 of the rotating awl 120 has a diameter greater than a diameter of the top surface 1221B of the bottom portion 1221, the bottom surface 1223a of the middle portion 1223 has a diameter equal to the diameter of the top surface 1221B of the bottom portion 1221, and the bottom surface 1223a of the middle portion 1223 has a diameter greater than the diameter of the top surface 1223B of the middle portion 1223, as shown in fig. 3B and 3C. Also, the bottom surface 1222a of the top 1222 has a diameter equal to the diameter of the top surface 1223B of the middle portion 1223, and the bottom surface 1222a of the top 1222 has a diameter greater than the diameter of the top surface 1222B of the top 1222, as shown in fig. 3A and 3B. The number of threads 124 on each portion varies due to the different diameters of the bottom 1221, middle 1223, and top 1222 portions.

Incidentally, the rotating body 122 may be formed integrally or assembled by three cylinders with different diameters. The threads 124 on the top 1222 of the rotating body 122 may be spaced apart with equal clearance and at a fixed angle θ 1, e.g., 15 degrees to 35 degrees, relative to the top 1222b or bottom 1222a of the top 1222; the threads 124 in the intermediate section 1223 may also be spaced at the same interval and the angle θ 2 relative to the top surface 1223b or the bottom surface 1223a of the intermediate section 1223 is fixed, e.g., 35 degrees to 70 degrees; the threads 124 on the bottom 1221 may be spaced apart by the same gap, and the angle θ 3 with respect to the top surface 1221b or the bottom surface 1221a of the bottom 1221 is fixed, for example, 70 degrees to 90 degrees. However, the angles of the threads 124 of the top 1222, middle 1223, and bottom 1221 portions are not all the same. For example, the angle of the threads 124 at the top 1222 is 25 degrees, the angle of the threads 124 at the bottom 1221 is 60 degrees, and the angle of the threads 124 at the middle 1223 is about 42.5 degrees. In addition, the angle of the thread 124 at the junction of the top 1222, middle 1223, and bottom 1221 portions is adjusted to account for the change in diameter, which may be 35 to 85 degrees.

When the gas flow generating apparatus 100 of fig. 1 is used, the rotating awl 120 is rotated in the chamber 112 at a rotational speed ranging from 3000rpm to 7000 rpm. Generally, when the rotating awl 120 rotates in the chamber 112, if the outer surface of the rotating awl 120 and the surface of the inner wall of the chamber 112 are smooth, the gas entering from the gas inlet opening 114 is driven by the rotation of the rotating awl 120 to generate a rotating gas flow and to escape from the gas outlet opening 116 at the top 1222 of the outer liner 110. The centrifugal force generated by the rotation of the rotating awl 120 can generate a slight horizontal component to the rotating airflow, but the horizontal component is not obvious and can be almost ignored compared to the upward force of the airflow escaping from the air outlet opening 116.

In particular, the spiral threads 124 are formed on the outer surface of the rotating body 122, so that when the gas enters the chamber 112 from the gas inlet opening 114 and is driven by the rotating awl 120 to form a rotating gas flow, the centrifugal force plus the guidance of the threads 124 makes the horizontal component of the rotating gas flow obvious.

Further, although the rotating awl 120 conforms to the outer bushing 110, the slit spacing 108 between the rotating body 122 and the inner wall of the cavity 112 varies, e.g., decreases, from the bottom surface 1221a of the bottom 1221 of the rotating body 122 to the top surface 1222b of the top 1222. This design is based on the gas flux equation, so that the gas entering the gas flow generating device 100 is compressed when flowing upward and the gas flow is accelerated from bottom to top. Since the chamber 112 provides a wide space S above the top surface of the top 1222 of the rotating body 122, the air flow leaving the rotating awl 120 expands after entering the wide space S and then escapes from the air outlet 116.

In short, the gas flow introduced from the gas inlet opening 114 has a slow, fast and slow flow rate change from the bottom 1221 to the top 1222 of the rotating awl 120, wherein the gas volume has a continuous and fast expansion change due to the gas flow leaving the slit distance 108 between the rotating awl 120 and the inner wall of the chamber 112 and then being released into a relatively large space S.

The gas flow generating device 100 can generate horizontal component of the gas flow by the cooperation of the screw threads 124 and the slit spaces 108, and can obtain continuous and rapid gas volume change of the gas flow in the unit space S after the gas flow leaves the screw threads 124, so that the device is suitable for producing graphene powder requiring intercalation process.

< graphene powder >

The graphene powder with the characteristic of low oxygen content can be prepared by the airflow generating device. Fig. 4 is a schematic flow chart of a method for manufacturing graphene powder. Hereinafter, a method for producing graphene powder flocs according to an embodiment of the present invention will be described in detail with reference to fig. 4.

Referring to fig. 4, step S110 is performed to perform a continuous high-speed forward rolling process on a graphite raw material to obtain a graphite precursor, where the graphite precursor has a slip structure. In this implementationIn one example, the spacing between the layers in the graphite stock is, for example, as

The spacing between layers in the graphite precursor is, for example

To

The average particle diameter is, for example, 10 μm to 100 μm, preferably, 15 μm to 35 μm; the average thickness is, for example, 0.05 μm to 1 μm, preferably, for example, 0.3 μm to 0.8 μm; the surface oxygen content is, for example, less than 5%, preferably, for example, less than 1%. The graphite precursor has a dislocation slip structure, so that the intercalation reaction is favorably carried out in the subsequent process. More specifically, a graphite precursor plate with a dislocation slip structure can be formed by continuously applying a high-speed stress to the tangential direction of the plane of the calendaring process, and then a graphite precursor powder is formed by a dry high-speed grinding process.

Next, referring to fig. 4, step S120 is performed to perform an intercalation reaction on the graphite precursor by using the compressed gas flow in the horizontal direction, so as to form a graphene and gas interlayer compound. In the present embodiment, the wind speed of the compressed airflow in the horizontal direction is, for example, mach 0.3 to mach 1, and preferably, mach 0.5 to mach 0.8; the air volume is, for example, 186CMM to 619CMM, preferably 310CMM to 495 CMM. More specifically, the horizontal direction compressed air flow may be a subcritical fluid, and since the wind speed is, for example, 0.3 mach or more, the horizontal direction compressed air flow may also be referred to as a subsonic compressible flow.

Then, with reference to fig. 4, step S130 is performed to perform an expansion exfoliation reaction between the graphene and the gaseous intercalation compound by releasing the pressure of the interlayer gas flow, so as to form a graphene aggregate. Then, as shown in fig. 4, step S140 is performed to make the graphene aggregates float and collide with each other in the gas flow, so as to generate graphene powder.

In this embodiment, the graphene powder has the advantages of fixed number of layers and consistent sheet diameter characteristics. Furthermore, the utility modelSpecifically, the number of layers of the graphene powder is, for example, 5 to 10 layers; the thickness is, for example, 2.5nm to 4.5 nm; the surface oxygen content is, for example, less than 0.1 wt%; the bulk density is, for example, 0.001g/cm³To 2.24g/cm³Preferably, it is, for example, 0.01g/cm³To 0.5g/cm³. The average sheet diameter of the graphene powder is, for example, 3 μm to 15 μm, more specifically, 3 μm to 5 μm, 5 μm to 10 μm, or 10 μm to 15 μm, and preferably, 3 μm to 5 μm.

< graphene Dispersion >

The graphene dispersion liquid of the present invention is prepared from the graphene powder and a processing solvent, wherein the amount of the graphene powder added is, for example, 0.001 wt% to 30 wt% based on the total weight of the graphene dispersion liquid. Because the graphene dispersion liquid is prepared by using the few-layer low-oxygen graphene powder with the specific layer number and the specific shape, the graphene powder is easy to homogenize under low energy and does not cause structural damage due to oxidation and the like on the basis of the characteristics of fixed layer number and uniform sheet diameter, so that the prepared graphene dispersion liquid has the advantages of high yield, high solid content, adjustability of solid content measuring tools and the like.

More specifically, the preparation method of the graphene dispersion liquid of the present invention includes the following steps. Firstly, a graphene powder and a treatment solvent are subjected to a homogenization process to form a graphene paste. And then, carrying out a thin-layer process on the graphene paste to form a uniform graphene dispersion liquid. The following will explain details of the graphene dispersion liquid preparation method of the present invention.

Treatment solvent

In this embodiment, the treatment solvent may include a hydrocarbon solvent, a halogenated hydrocarbon solvent, an alcohol solvent, a phenol solvent, a ketone solvent, an ether and an acetal solvent, an acid and an acid anhydride solvent, a nitrogen-containing compound solvent, a sulfur-containing compound solvent, a polyfunctional group solvent, or an inorganic solvent. More specifically, the treating solvent is, for example, toluene, xylene (Xyl), ethanol, Isopropanol (IPA), butanol, acetone, ethyl acetate, Butyl Acetate (BAC), N-Dimethylformamide (DMF), N-methylpyrrolidone (NMP), N-dimethylacetamide (DMAc), or water.

However, the treating solvent to which the present invention is applied is not limited to the specific examples listed above, and other solvents having the following properties may be used as the treating solvent: the interfacial tension ranges, for example, from 15 to 50mN/m, preferably, for example, from 20 to 40 mN/m; the Hansen solubility parameter is, for example, 5.0MPa^0.5To 15MPa^0.5(ii) a The polar force parameter is, for example, 0.5MPa^0.5To 5.5MPa^0.5(ii) a The dispersion parameter is, for example, 7.0MPa^0.5To 9.0MPa^0.5(ii) a And the hydrogen bonding force parameter is, for example, 2.0MPa^0.5To 7.0MPa^0.5. More specifically, the processing solvent is added in an amount of, for example, 70 wt% to 99.99 wt% based on the total weight of the graphene dispersion.

Homogenization process

In the method for preparing the graphene dispersion liquid of the present invention, a homogenization process is performed to form a graphene paste as a byproduct of an intermediate process. The homogenization process is to adjust and change the average sheet diameter range of the graphene powder by generating normal direction stress on the graphene structure on the premise of not changing the thickness of the graphene so as to achieve the purpose of sheet diameter homogenization. Therefore, the suspension property of the graphene in the liquid can be effectively improved, the longest suspension time can reach more than 150 days, and the content of the dispersing agent can be reduced.

In this embodiment, the homogenization process may include two steps of mixing and re-dispersing, and the homogenization process may be performed by a device such as a dc mechanical mixer, a planetary mixer, an internal mixer, a ball mill, a three-roller mixer, a single -shaft mixer or a double -shaft mixer, so that the present invention can solve the problems of low graphene content, and the conductivity degradation caused by the oxidation damage of the structure, compared to the prior art in which graphite is used as a raw material and the graphene dispersion liquid is obtained through the processes of dispersing, oxidizing, peeling and centrifuging.

Graphene paste

In this example, the characteristics of the graphene paste include: the average sheet diameter of the graphene is, for example, 0.1 μm to 1.5 μm, preferably, 0.3 μm to 0.8 μm; the thickness of the graphene is, for example, 2.5nm to 4.5 nm; the surface oxygen content is, for example, less than 0.5%, and the solids content is, for example, from 5% to 50%, and most preferably from 15% to 30%.

Thin layer process

In the preparation method of the graphene dispersion liquid, the graphene paste is subjected to a thin-layer process to form a uniform graphene dispersion liquid. The thin layer process is to change the average thickness range of the graphene powder by generating stress in the plane direction on the graphene structure on the premise of not changing the sheet diameter of the graphene so as to achieve the purpose of uniform suspension. Thus, the suspension time and the allowable proportion of the solid content can be improved.

In this embodiment, the thin layer process may include two different processes, a mixing process and a high energy dispersion process. More specifically, the mixing process may be performed by a five-axis mixing method, a ball-milling mixing method, a shear mixing method, or the like, and the high-energy shear process may be performed by re-dispersing by a high-speed homogenizing method, a high-pressure crushing method, or the like, to form a uniform graphene dispersion.

By the preparation method of the graphene dispersion liquid, the high-concentration graphene dispersion liquid with specific concentration change can be prepared, and no dispersing agent is required to be added, so that the graphene structure in the graphene dispersion production is not interfered by excessive dispersing auxiliary agents, and good material physical properties are kept. More specifically, in the graphene dispersion liquid of the present invention, the graphene purity is about 100%, and the average sheet diameter of the graphene in the graphene dispersion liquid is, for example, 0.5 μm to 1 μm; the number of layers is, for example, 3 to 5 layers; the solids content is, for example, 5% to 50%; the surface oxygen content is for example less than 1 wt%; the thickness is, for example, 0.8nm to 4.5nm, preferably, 1.0nm to 2.0 nm.

In addition, the graphene dispersion may have a distribution concentration after standing for 12 hours, which is gradually increased from the upper layer to the bottom layer, such as a viscosity of 5000cps to 8000cps, and a graphene concentration of 20 wt%, for example, wherein the difference in concentration (C%) between the upper layer and the bottom layer is 0.1 wt% to 20 wt%, preferably 5 wt% to 15 wt%, for example, and the maximum suspension time may be more than 150 days.

Hereinafter, the graphene dispersion liquid proposed by the present invention will be described in detail by way of experimental examples. However, the following experimental examples are not intended to limit the present invention.

Examples of the experiments

In order to prove that the graphene dispersion liquid of the present invention has a high solid content and suspension property, the experimental example is specifically made below.

It should be noted that, since the preparation method of the graphene dispersion liquid has been described above in detail, the following description of the preparation of the graphene dispersion liquid is omitted for convenience of description.

Preparation of graphene dispersion

According to the above preparation method of the graphene dispersion of the present invention, the graphene dispersions of examples 1 to 21 were prepared under the respective composition conditions and process conditions listed in table 1 below. In table 1, the mixing ratio (G/S) represents the ratio of Graphene/Solvent (Graphene/Solvent).

TABLE 1

Evaluation 1: evaluation of characteristics of graphene dispersion liquid

For the graphene dispersions prepared in examples 1 to 21, the average sheet diameter, the number of layers, and the concentration difference (C%) between the upper layer and the bottom layer after standing for 12 hours of the graphene were measured, and the evaluation results are listed in table 2 below.

The difference in concentration of the dispersion was measured by analyzing the solids content of the dispersion at 1/3 and 2/3 elevations from the horizontal every 24 hours, and determining the concentration C at 2/3_2/3% and concentration C at 1/3_1/3% is subtracted to obtain the difference in C% concentration, where the solid content is the concentration obtained after evaporating the liquid to dryness. If the concentration difference is greater than 20% (i.e., (C)_1/3％–C_2/3％)>20%), the dispersibility is poor.

TABLE 2

As can be seen from table 2 above, the average sheet diameter distribution of the graphene of examples 1 to 21 prepared by the preparation method of the present invention is uniform, and thus, the problem of non-uniform sheet diameter distribution of the product in the existing physical methods such as mechanical peeling, ultrasonic vibration or ball milling can be improved. In addition, the graphene dispersions of examples 1 to 21 exhibited a state in which the distribution concentration was gradually increased from the upper layer to the lower layer after standing for 12 hours.

Evaluation 2: comparison of characteristics between the graphene dispersion liquid of the present invention and commercially available products

The solid content and the maximum suspension time of graphene in the graphene dispersions prepared in examples 1 to 21 and the commercial products of comparative examples 1 to 6 were measured, and the evaluation results are listed in table 3 below.

The solid content is the concentration obtained after evaporating the liquid to dryness. The suspension time 150 days is defined as the time of at least 150 days if the concentration difference is < 20%, measured at 150 days after the preparation of the dispersion. The method for measuring the concentration difference is described above, and therefore, the description thereof is omitted.

The commercial products of comparative examples 1 to 6 were prepared by the conventional oxidation process and delamination process without using the homogenization process and the thinning process proposed in the present invention, wherein the raw material of comparative examples 1 to 3 was graphite, and the raw material of comparative examples 4 to 6 was graphene.

TABLE 3

As can be seen from table 3, examples 1 to 21 prepared by the preparation method of the present invention have significantly higher graphene solid content than comparative examples 1 to 6 prepared by the conventional oxidation process and delamination process, and thus the preparation method of the present invention can solve the problem of low graphene solid content of commercially available products, and further improve processability, thereby facilitating application in the field of coating materials. In addition, as shown in table 3, compared with the commercial products of comparative examples 1 to 6, the preparation method of the graphene dispersion liquid of the present invention can effectively increase the suspension property of graphene in liquid, so that the maximum suspension time can reach 150 days.

In summary, the present invention mainly uses the airflow generating device to produce the low-oxygen graphene powder with a specific number of layers, and then the graphene powder with the specific number of layers and type is made into the graphene dispersion liquid with high solid content, so that the problems of low solid content, low solvent selectivity, and the like of the graphene dispersion liquid sold in the market can be solved, and further the processability and the adaptability of different coating processes can be improved, which is beneficial to the application in the field of coating materials. In addition, the preparation method of the graphene dispersion liquid does not need to use other oxidation methods, surface modification methods or add a large amount of dispersing aids (> 5%), so that the graphene structure is not damaged, the structure can be kept complete, and the graphene structure is not interfered by excessive dispersing aids, so that the good material physical properties of the graphene can be kept, the problems of waste water pollution and toxic waste exhaust caused by acid-base and heavy metal waste liquid and the like in the prior art can be solved, and the environmental protection requirement can be better met. Therefore, the method can effectively solve most technical problems existing in the graphene dispersion liquid manufacturing process so as to increase the yield, homogenize the product specification and increase the suspension property of the graphene in the graphene dispersion liquid.

Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. An airflow generating device for preparing graphene powder comprises:

an outer liner having a cavity, an inlet opening and an outlet opening, the inlet opening communicating below the cavity and the outlet opening communicating above the cavity, wherein the cavity has a necked-down portion; and

the rotating awl is arranged in the cavity, the rotating awl is matched with the cavity, and a slit space is arranged between the rotating awl and the inner wall of the cavity, wherein the rotating awl comprises a rotating body and a plurality of threads, the threads are spirally distributed on the outer surface of the rotating body from the bottom of the rotating body to the top of the rotating body,

when the rotating awl rotates in the chamber, a cyclone is generated having a component in an upward and horizontal direction by the threads and the slit interval.

2. The airflow-generating apparatus of claim 1, wherein a top surface of the rotating awl is flush with a top surface of the necked portion.

3. The airflow-generating device according to claim 1, wherein said rotating body includes said bottom portion, said top portion, and a middle portion between said bottom portion and said top portion, wherein a diameter of said rotating body decreases in order from said bottom portion to said top portion.

4. The airflow-generating apparatus of claim 3, wherein a diameter of a bottom surface of the bottom portion is larger than a diameter of a top surface of the bottom portion.

5. The airflow generating apparatus according to claim 4, wherein a diameter of a bottom surface of the middle portion is larger than a diameter of a top surface of the middle portion, and the diameter of the bottom surface of the middle portion is equal to the diameter of the top surface of the bottom portion.

6. The airflow generating apparatus of claim 5, wherein a diameter of a bottom surface of the top portion is larger than a diameter of a top surface of the top portion, and the diameter of the bottom surface of the top portion is equal to the diameter of the top surface of the middle portion.

7. The airflow-generating apparatus of claim 1, wherein the cross-section of said rotating awl is star-shaped and awn-shaped.

8. The airflow-generating apparatus of claim 1, wherein the rotating awl has a rotating speed ranging from 3000rpm to 7000 rpm.

9. The airflow generating device according to claim 1, wherein the number of threads is between 8 and 32.

10. The airflow generating device of claim 9, wherein the number of threads is between 12 and 18.

11. The airflow generating apparatus according to claim 1, wherein the slit pitch ranges from 0.05 mm to 10 mm.

12. The airflow generating device according to claim 11, wherein the slit pitch ranges from 0.1 mm to 1 mm.

13. A preparation method of a graphene dispersion liquid comprises the following steps:

carrying out a homogenization process on the graphene powder and the treatment solvent to form a graphene paste; and

carrying out a thin-layer process on the graphene paste to form a graphene dispersion liquid,

wherein the graphene powder is manufactured using the airflow generation apparatus according to claims 1 to 12.

14. The method of preparing a graphene dispersion according to claim 13, wherein the method of preparing a graphene powder comprises:

carrying out continuous high-speed forward calendaring process on a graphite raw material to prepare a graphite precursor, wherein the graphite precursor has a dislocation sliding structure;

carrying out intercalation reaction on the graphite precursor by compressing airflow in the horizontal direction to form a graphene and gas interlayer compound;

carrying out an expansion stripping reaction on the graphene and a gas interlayer compound through interlayer gas flow pressure release to form a graphene aggregate; and

and enabling the graphene aggregates to float and drift in the air flow and collide with each other to generate graphene powder.

15. The method of claim 14, wherein the spacing between layers in the graphite precursor is

To

16. The method of preparing a graphene dispersion according to claim 14, wherein the air velocity of the horizontally-oriented compressed air flow is from mach 0.3 to mach 1.

17. The method for producing a graphene dispersion liquid according to claim 14, wherein an air volume of the horizontal direction compressed air flow is 186CMM to 619 CMM.

18. A graphene dispersion liquid prepared from a graphene powder and a processing solvent using the method according to claims 13 to 17, wherein the graphene dispersion liquid has an average sheet diameter of 0.5 to 1 μm, a number of layers of 3 to 5, a solid content of 5 to 50%, and a surface oxygen content of less than 1 wt%, and the graphene dispersion liquid is allowed to stand for 12 hours with a distribution concentration gradually increasing from an upper layer to a bottom layer, a viscosity of 5000 to 8000cps, and a graphene concentration of 20 wt%.

19. The graphene dispersion according to claim 18, wherein the difference in concentration between the upper layer and the bottom layer in the graphene dispersion is 0.1 wt% to 20 wt%.

20. The graphene dispersion liquid according to claim 18, wherein the number of layers of the graphene powder is 5 to 10.

21. The graphene dispersion liquid according to claim 18, wherein the average platelet diameter of the graphene powder is 3 μm to 15 μm.

22. The graphene dispersion liquid according to claim 18, wherein the surface oxygen content of the graphene powder is less than 0.1 wt%.

23. The graphene dispersion liquid according to claim 18, wherein the treatment solvent includes a hydrocarbon solvent, a halogenated hydrocarbon solvent, an alcohol solvent, a phenol solvent, a ketone solvent, an ether and an acetal solvent, an acid and an acid anhydride solvent, a nitrogen-containing compound solvent, a sulfur-containing compound solvent, a multi-functional group solvent, or an inorganic solvent.

24. The graphene dispersion according to claim 18, wherein the treatment solvent has an interfacial tension in a range of 15mN/m to 50mN/m and a hansen solubility parameter of 5.0MPa^0.5To 15MPa^0.5。

25. The graphene dispersion liquid according to claim 18, wherein the graphene powder is added in an amount of 0.001 wt% to 30 wt% based on the total weight of the graphene dispersion liquid.

26. The graphene dispersion of claim 18, wherein the polar force parameter of the processing solvent is 0.5MPa^0.5To 5.5MPa^0.5The dispersion parameter is 7.0MPa^0.5To 9.0MPa^0.5And hydrogen bonding force parameter is 2.0MPa^0.5To 7.0MPa^0.5。