KR20220139662A - Eco-friendly mass manufacturing method of high purity graphene flakes - Google Patents

Abstract

The present invention relates to an eco-friendly mass production manufacturing method of high-purity graphene flakes, and more specifically, to an eco-friendly mass production manufacturing method of high-purity graphene flakes, which can significantly reduce production costs by mass-producing high-purity and high-quality graphene, and which comprises: a material preparation step; a mixture generation step; a hydrogen peroxide mixing step; an electrolytic peeling step; and a solid powder liquid separation and washing step.

Description

Eco-friendly mass manufacturing method of high purity graphene flakes

The present invention relates to an eco-friendly mass-production method of high-purity graphene flakes, and more specifically, it is possible to mass-produce high-purity and high-quality graphene, so that production costs can be significantly reduced, and strong acid generated in the mass production process However, it is possible to minimize the occurrence of environmental pollution caused by the discharge of strong basic waste liquid, and to mass-produce hydrogen-functionalized graphene to facilitate the development of new materials using high-purity graphene flakes. will be.

In general, materials for aircraft and automobiles are increasingly required to be lightweight and high-strength for the purpose of improving fuel efficiency and reducing energy consumption. is widely used as structural members of aircraft and automobiles due to its advantages such as light weight, high strength, and excellent formability.

Conventional graphene-metal composites are manufactured through a powder metallurgy process of mixing metal powder and graphene powder, performing a dry exfoliation process, and then sintering. In the case of powder metallurgy, graphene powder is Due to the van der Waals force between the fins, graphene is strongly agglomerated, so it is difficult to distribute it uniformly in the metal matrix. The uniform distribution within the metal matrix is lowered, and the agglomerated graphene interferes with the sintering of the composite powder to reduce the density, reduce the properties of the composite material, and mix the graphene with metal powders such as aluminum and titanium for sintering There was a problem in that it was difficult to manufacture a graphene-metal composite material because carbides such as aluminum carbide and titanium carbide were formed on the bottom surface, so that the reinforcement effect by the original graphene could not be expected.

On the other hand, the functionalization of hydrogen refers to a form in which hydrogen or a functional group from which hydrogen can be generated is bonded or adsorbed to a base, and hydrogen bonds between hydrogen or a functional group from which hydrogen can be generated, such as a C-H or C-OH bond, and a base; Hydrogen or a functional group from which hydrogen can be generated by the structure of the adsorption matrix through a chemical bond such as a covalent bond or a non-covalent cross-linking bond or an electrostatic attraction such as a van der Waals bond is trapped in the matrix, and the like.

In the case of a hydrogen-functionalized graphene-metal composite, it is possible to minimize the aggregation of graphene by strengthening the bonding force between graphene and metal and improving the dispersion of graphene, and casting process using graphene and metal mixture There are various advantages such as suppressing the separation phenomenon caused by the density difference between graphene and metal, so that graphene-metal alloy can be easily manufactured through the casting process.

As such, hydrogen-functionalized graphene is known to exhibit more improved functions such as ease of manufacturing graphene-metal composites, hydrogen storage, and increased electrical and magnetic properties compared to conventional graphene, but hydrogen functionalized graphene Graphene generally has a problem in that it is difficult to mass-produce than graphene, and in the case of a conventional method for producing graphene flakes through chemical exfoliation, there is a problem in that a strong acid or strong basic waste solution is generated, and the strong acid or strong basic waste solution is used. There is a problem of environmental pollution, such as not being recycled and discharged to the outside as it is.

The present invention was derived to solve the above problems, it enables mass production of high-purity and high-quality graphene, thereby significantly reducing production costs, and for discharging strong acid or strong basic waste liquid generated in the mass production process. It is possible to minimize the occurrence of environmental pollution and to mass-produce hydrogen-functionalized graphene to facilitate the development of new materials using high-purity graphene flakes.

In one aspect of the present invention for solving the above-described problems, a material preparation step of preparing an aqueous solution containing at least one ion of a carbon-based material and a group 1 or 2 element having a layered structure; After the prepared carbon-based material and the aqueous solution are put into a homogenizer, the homogenizer is operated for a predetermined time at a predetermined temperature and a predetermined rotation speed to remove ions of one or more Group 1 or Group 2 elements contained in the aqueous solution. Creating a mixture inserted between the layers of the carbon-based material; After adding hydrogen peroxide to the mixture generated through the mixture generating step, the homogenizer is operated again for a predetermined time at a predetermined temperature and a predetermined rotation speed to remove the Group 1 or Group 2 element ions inserted between the layers of the carbon-based material. A hydrogen peroxide mixing step of oxidizing and discharging ions to widen the interlayer spacing of the carbon-based material through oxidative discharge; an electrolytic peeling step of exfoliating the carbon-based material in the hydrogen peroxide mixture with an increased interlayer spacing by passing a current of a predetermined current value to the hydrogen peroxide mixture generated through the hydrogen peroxide mixing step for a predetermined time; And, vacuum filtering the hydrogen peroxide mixture that has undergone the electrolytic stripping step to separate the solid powder and liquid, and repeat washing the separated solid powder using ultrapure water until the pH of the separated solid powder becomes 7 a solid powder liquid separation and washing step of removing impurities remaining in the separated solid powder; After removing a predetermined amount of water through fractional distillation and washing water separated through the solid powder liquid separation and washing step, an aqueous solution containing at least one ion of a group 1 or group 2 element is washed It provides an eco-friendly mass production method of high-purity graphene flakes, characterized in that quantitative mixing and reuse as the aqueous solution in the material preparation step.

In the eco-friendly mass production method of high-purity graphene flakes according to one aspect of the present invention, the solid powder separated from the hydrogen peroxide mixture and washed after the solid powder liquid separation and washing step is put into a dry peeling device, a dry peeling step of increasing the degree of peeling of the solid powder by operating the dry peeling device in an inert gas atmosphere at a predetermined temperature and for a predetermined time; It can be formed to further include,

Preferably, the solid powder that has undergone the dry peeling step is put into a hydrogen-functionalized device having an internal temperature formed at a predetermined temperature, and an inert gas and hydrogen gas are mixed in a predetermined volume ratio into the hydrogen-functionalized device into which the solid powder is introduced. a hydrogen functionalization step of rapidly cooling the solid powder injected into the hydrogen functionalization device after flowing the mixed gas for a predetermined time; It may be formed to further include.

The eco-friendly mass-production method of high-purity graphene flakes according to the present invention enables mass production of high-purity and high-quality graphene, thereby significantly reducing production costs, and according to the discharge of strong acid or strong basic waste liquid generated in the mass production process Environmental pollution can be minimized, and hydrogen-functionalized graphene can be mass-produced to facilitate the development of new materials using high-purity graphene flakes.

1 is a process block diagram showing step-by-step an environmentally friendly mass production method of high-purity graphene flakes according to the present invention;
2 is an SEM and TEM image showing the high-purity graphene flakes manufactured through the dry peeling step in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;
3 is an SEM and TEM image of high-purity graphene flakes functionalized with hydrogen in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;
4 is a TEM image and an elemental mapping analysis image of a hydrogen-functionalized high-purity graphene flake in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;
5 is a CHNS analysis of high-purity graphene flakes functionalized with hydrogen in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;
6 is a dispersibility test image of high-purity graphene flakes functionalized with hydrogen in ultrapure water and a dispersibility test image in plastic in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;
7 is a test image of a change in mechanical properties when an aluminum casting material is used by compounding hydrogen-functionalized high-purity graphene flakes with aluminum in the environmentally friendly mass production method of high-purity graphene flakes according to the present invention; and,
8 is a schematic diagram briefly showing high-purity graphene flakes functionalized with hydrogen in the environmentally-friendly mass production method of high-purity graphene flakes according to the present invention;

Hereinafter, embodiments of the present invention in which the above object can be specifically realized will be described with reference to the accompanying drawings. In describing the present embodiments, the same names and reference numerals are used for the same components, and an additional description thereof will be omitted below.

1 is a process block diagram showing step-by-step an environmentally friendly mass production method of high-purity graphene flakes according to the present invention.

As shown in FIG. 1 , the mass production method of high-purity graphene flakes according to the present invention includes a material preparation step, a mixture generation step of mixing the prepared material in a predetermined ratio through a homogenizer, and the mixture generation step A hydrogen peroxide mixing step of homogeneously mixing after adding hydrogen peroxide to the mixture produced through and a solid powder liquid separation and washing step of washing the separated solid powder after separating the liquid, and in particular, discharging the liquid and washing water separated through the solid powder liquid separation and washing step to the outside as it is Rather, it is characterized in that it is reused as an aqueous solution in the material preparation step.

The material preparation step is a step of preparing an aqueous solution containing at least one ion of a carbon-based material and a Group 1 or Group 2 element used as a material for mass production of high-purity graphene flakes, wherein the carbon-based material is natural graphite , artificial graphite, expanded graphite, functional graphite, etc. may include all carbon-based materials having a layered structure while having conductivity, and at least one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, and functional graphite. A carbon-based material may be used. In addition, an aqueous solution containing at least one ion of a Group 1 or Group 2 element, such as an aqueous NaOH solution, an aqueous KOH solution, or an aqueous KCl solution, is prepared along with the carbon-based solution.

In the mixture generating step, the prepared aqueous solution containing the carbon-based material and at least one ion of a Group 1 or Group 2 element is put into the homogenizer, and then the homogenizer is operated for a predetermined time at a predetermined temperature and a predetermined rotation speed. Through mixing and homogenization of the carbon-based material and the aqueous solution, ions of one or more Group 1 or Group 2 elements included in the aqueous solution are bonded and inserted between the layers of the carbon-based material.

Preferably, the internal temperature of the homogenizer may be maintained at a temperature of 80 to 200° C., the rotational speed of the homogenizer may be operated at 100 to 1000 rpm, and the operating time of the homogenizer may be 1 hour to 1 hour It can run for 30 minutes. When the internal temperature of the homogenizer is lower than 80 ° C., diffusion of ions is slow, and when higher than 200 ° C., the manufacturing cost may increase, and when the rotation speed is lower than 100 rpm, homogenization is slow, and when higher than 1000 rpm The smooth diffusion of ions can be performed, and when the operating time is shorter than 1 hour, homogenization is not completely achieved, and when it is longer than 1 hour and 30 minutes, the manufacturing cost may increase.

In the hydrogen peroxide mixing step, after adding hydrogen peroxide to the mixture generated through the mixture generating step, the homogenizer is operated again for a predetermined time at a predetermined temperature and a predetermined rotation speed, and 1 inserted between the layers of the carbon-based material The group or group 2 element ions are oxidized and discharged, and the interlayer spacing of the carbon-based material is widened through the oxidative discharge of the group 1 or group 2 element ions that have been bonded and inserted between the layers of the carbon-based material.

Preferably, 10 to 70 parts by weight of hydrogen peroxide are mixed with respect to 100 parts by weight of the mixture, the internal temperature of the homogenizer is maintained at 80 to 200° C., and the rotational speed of the homogenizer can be operated at 100 to 1000 rpm. And, the operation time of the homogenizer is operated for 1 hour to 1 hour and 30 minutes to promote the oxidation of the Group 1 or Group 2 element ions that have been bonded and inserted between the layers of the carbon-based material, and the inserted ions generated at this time The interlayer spacing of the carbon-based material is increased through the elution of ions. If the amount of hydrogen peroxide input is less than 10 parts by weight, the oxidative emission of ions is small, the efficiency of electrolytic peeling performed in the next step is reduced, and when it is more than 70 parts by weight, the oxidation degree of graphene may be increased, When the internal temperature of the homogenizer is lower than 80 ° C., diffusion of ions is slow, and when higher than 200 ° C., the manufacturing cost may increase, and when the rotation speed is lower than 100 rpm, homogenization is slow, and when higher than 1000 rpm The smooth diffusion of ions may be disturbed, and if the operation time is shorter than 1 hour, homogenization is not completely achieved, and if it is longer than 1 hour and 30 minutes, the manufacturing cost may increase.

In the electrolytic peeling step, a current of a predetermined current value is passed to the hydrogen peroxide mixing fire generated through the hydrogen peroxide mixing step for a predetermined time, and the carbon-based material in the hydrogen peroxide mixture whose interlayer spacing is widened through the acid discharge of ions is peeled off will make it

The electrolytic peeling method in the electrolytic peeling step can carry out a conventional electrolytic peeling method in addition to targeting the hydrogen peroxide mixture, so the description of the conventionally conventionally performed electrolytic peeling method is omitted, preferably is, the hydrogen peroxide mixture can be energized with a current value of 0.01 to 1 A for 10 to 30 minutes to proceed with electrolytic peeling, and when the current value is lower than 0.01 A, the efficiency of electrolytic peeling is lowered, and when higher than 1 A There is a problem that the risk of explosion and the quality is lowered.

In the solid powder liquid separation and washing step, the hydrogen peroxide mixture that has undergone the electrolytic separation step is vacuum filtered to separate the carbon-based solid powder and liquid, and the separated carbon-based solid powder is the separated carbon using ultrapure water. The washing is repeated until the pH of the solid-based solid powder becomes '7', that is, until it becomes neutral, to remove impurities and ions remaining in the separated carbon-based solid powder. In particular, in the eco-friendly mass production method of high-purity graphene flakes according to the present invention, the liquid and washing water generated in the solid powder liquid separation and washing step are not discharged to the outside as they are, but the separated liquid and washing water are used together. After removing a predetermined amount of water through fractional distillation, a predetermined amount of an aqueous solution containing at least one ion of a Group 1 or Group 2 element is mixed and reused as the aqueous solution in the material preparation step, in the case of conventional chemical peeling For example, the strong acid or strong basic solution used for exfoliation cannot be reused, and the problem of causing environmental pollution can be solved by discharging it to the outside as it is, and the high-cost solution can be recycled, which can significantly reduce the production cost of high-purity graphene flakes. there will be

Preferably, the carbon-based solid powder separated from the hydrogen peroxide mixture and washed through the solid powder liquid separation and washing step is put into a dry peeling device, and then dry peeled at a predetermined temperature and for a predetermined time in an inert gas atmosphere. By further performing a dry peeling step of separating each layer through an interlayer gap that is widened according to the discharge of impurities and ions while drying the carbon-based solid powder through the process, the degree of peeling of the solid powder is increased. By creating an Ar atmosphere inside the dry peeling device, oxidation of the carbon-based solid powder is prevented, the internal temperature is maintained at 80 degrees to facilitate drying, and the carbon-based solid powder is dried and uniform while operating for 24 hours. can be peeled off. In the process of increasing the degree of peeling through the dry peeling step, a peeling method using mechanical energy such as an attrition mill, a ball mill, or a jed mill can be used.

In addition, after performing the dry peeling step, the carbon-based solid powder that has undergone the dry peeling step is put into a hydrogen functionalization device in which an internal temperature is formed at a predetermined temperature, and the hydrogen functionalized device into which the carbon-based solid powder is added After flowing the mixed gas in which the inert gas and hydrogen gas are mixed in a predetermined volume ratio into the furnace for a predetermined time, a hydrogen functionalization step of rapidly cooling the carbon-based solid powder injected into the hydrogen functionalization device may be performed.

The hydrogen functionalization refers to a form in which hydrogen or a functional group from which hydrogen can be generated is bonded or adsorbed to a base, and a chemical bond such as hydrogen bonding or covalent bonding between hydrogen or a functional group from which hydrogen can be generated and a base, or half Hydrogen or a functional group in which hydrogen can be generated by the structure of the adsorption matrix through electrostatic attraction such as Der Waals bond is included in the matrix, and the like, remaining in the carbon-based solid powder through the hydrogen functionalization step impurities are removed, and hydrogen helps reduce the carbon-based solid powder, that is, graphene to form high-purity graphene, and at the same time, some hydrogen enters the reduced site to form a covalent bond between graphene and hydrogen, Some hydrogen is trapped by the Wal der Waals force between the layers of graphene, and then contains hydrogen at a level of several wt% by rapid cooling.

Preferably, while maintaining the temperature inside the hydrogen functionalization device at 300 ~ 500 ℃, a mixed gas of a volume ratio of argon gas and hydrogen gas of 5:5 ~ 9:1 flows into the hydrogen functionalization device at a constant flow rate You can keep it for 5 to 6 hours while sending it, and then quench it. When the temperature inside the hydrogen functionalization device is lower than 300° C., the removal of impurities due to hydrogen reduction is not made homogeneously. When the temperature is higher than 500° C., the cost efficiency is lowered. If this is low and high, there is a risk of explosion, and the mixed gas must be flowed at a flow rate sufficient to achieve hydrogen reduction, and too strong flow can cause dust, so it can flow at 100 sccm.

In addition, the carbon-based solid powder, that is, the graphene powder that has undergone the hydrogen functionalization step, can be exposed to a high temperature maintenance device of 1000° C. or higher for several seconds to several minutes, and at this time, the interlayer space of the graphene powder heated to a high temperature instantaneously is It expands to increase the degree of exfoliation of the graphene flakes, and at the same time, as some hydrogen escapes from the surface of the graphene flakes heated at a high temperature instantaneously, the remaining impurities can be almost completely removed, and hydrogen-functionalized high-purity graphene Flakes can be mass-produced.

Hereinafter, an embodiment according to the present invention will be described.

In the eco-friendly mass production method of high-purity graphene flakes according to the present invention, 100 parts by weight of impression graphite and 900 parts by weight of a 0.6M KOH aqueous solution are prepared as the material preparation step, and the internal temperature is maintained at 80 ° C. After the impression graphite and KOH aqueous solution were added, the mixture was formed by inserting ions between the layers of graphite by operating at a rotation speed of 120 rpm for 8 hours.

After adding 20 parts by weight of hydrogen peroxide to 100 parts by weight of the mixture generated through the mixture generation step into the homogenizer, it was operated for 1 hour at a rotation speed of 120 rpm while maintaining at 80 ° C. Inserted between the layers of the carbon-based material The hydrogen peroxide mixing step was performed to widen the interlayer gap through ion elution.

The electrolytic peeling step was carried out by energizing the hydrogen peroxide mixture that had undergone the hydrogen peroxide mixing step at a current value of 0.1A for 12 hours. The separated carbon-based solid powder was washed repeatedly until the pH reached '7' by adding ultrapure water to perform the liquid separation and washing steps of the solid powder.

After putting the carbon-based solid powder separated through the solid powder liquid separation and washing steps into the ball mill device, the dry peeling step was performed by operating the ball mill device for 24 hours while maintaining the temperature at 80° C. in an argon atmosphere. .

After the carbon-based solid powder, that is, the graphene flakes that have undergone the dry peeling step, was put into a hydrogen functionalization device maintaining an internal temperature of 300° C., a mixed gas in which argon gas and hydrogen gas were mixed in a volume ratio of 8:2 After maintaining for 5 hours while flowing at a flow rate of 100 sccm, it was rapidly cooled to room temperature to carry out the hydrogen functionalization step,

After carrying out the hydrogen functionalization step, the hydrogen-functionalized graphene flakes were additionally put into a high-temperature maintaining device heated to 1200° C., and then maintained for 1 minute.

2 is an SEM and TEM image showing the high-purity graphene flakes manufactured through the dry peeling step in the eco-friendly mass production method of high-purity graphene flakes according to the present invention.

3 is an SEM and TEM image of the hydrogen-functionalized high-purity graphene flake prepared in the above-described embodiment in the eco-friendly mass production method of high-purity graphene flakes according to the present invention. You can confirm that it is a pin,

4 is a TEM image and elemental mapping analysis of the hydrogen-functionalized high-purity graphene flakes prepared in the above-described embodiment in the eco-friendly mass production method of high-purity graphene flakes according to the present invention. It can be seen that the flakes were hardly oxidized, and at the same time, no impurities were present.

5 is a CHNS analysis of the hydrogen-functionalized high-purity graphene flakes prepared in the above-described embodiment in the eco-friendly mass production method of high-purity graphene flakes according to the present invention, in which hydrogen at a level of 2 At% is functionalized It can be confirmed that there is

6 is a comparison test photograph of dispersibility in ultrapure water of high-purity graphene flakes functionalized with hydrogen prepared in the above-described embodiment in the environmentally friendly mass production method of high-purity graphene flakes according to the present invention, compared to MWCNTs. It can be seen that the dispersibility is very good, and it can be confirmed that the dispersibility test in plastic shows a high level of dispersibility even without additives.

In addition, in Figure 7, in the environmentally friendly mass production method of high-purity graphene flakes according to the present invention, hydrogen-functionalized high-purity graphene flakes prepared in the above-described embodiment are composited with aluminum when an aluminum casting material is used. In the mechanical property change test of the conventional carbon-based material, it was difficult to use as a casting material, but in the case of the hydrogen-functionalized high-purity graphene flake according to the present invention, it was confirmed that casting was possible, and the material properties of the cast alloy were improved. can confirm.

Although several embodiments have been described above by way of example, it is apparent to those skilled in the art that the present invention may be embodied in various forms without departing from the spirit and scope thereof.

Accordingly, the above-described embodiments are to be regarded as illustrative and not restrictive, and all embodiments within the scope of the appended claims and their equivalents are included within the scope of the present invention.

Claims (3)

A material preparation step of preparing an aqueous solution containing a carbon-based material having a layered structure and at least one ion of a Group 1 or Group 2 element;
After the prepared carbon-based material and the aqueous solution are put into a homogenizer, the homogenizer is operated for a predetermined time at a predetermined temperature and a predetermined rotation speed to remove ions of one or more Group 1 or Group 2 elements contained in the aqueous solution. Creating a mixture inserted between the layers of the carbon-based material;
After adding hydrogen peroxide to the mixture generated through the mixture generating step, the homogenizer is operated again for a predetermined time at a predetermined temperature and a predetermined rotation speed to remove the Group 1 or Group 2 element ions inserted between the layers of the carbon-based material. A hydrogen peroxide mixing step of oxidizing and discharging ions to widen the interlayer spacing of the carbon-based material through oxidative discharge;
an electrolytic peeling step of exfoliating the carbon-based material in the hydrogen peroxide mixture with an increased interlayer spacing by passing a current of a predetermined current value to the hydrogen peroxide mixture generated through the hydrogen peroxide mixing step for a predetermined time; and,
The hydrogen peroxide mixture that has undergone the electrolytic stripping step is vacuum filtered to separate a solid powder and a liquid, and the separated solid powder is washed with ultrapure water until the pH of the separated solid powder becomes 7 by repeating the separated a solid powder liquid separation and washing step of removing impurities remaining in the solid powder; is formed including
The liquid and washing water separated through the solid powder liquid separation and washing step are obtained by removing a predetermined amount of water through fractional distillation, and then mixing a predetermined amount of an aqueous solution containing at least one ion of a Group 1 or Group 2 element to the material. An eco-friendly mass production method of high-purity graphene flakes, characterized in that it is reused as the aqueous solution in the preparation step.
The method of claim 1,
After the solid powder separated from the hydrogen peroxide mixture and washed through the liquid separation and washing steps is put into a dry peeling device, the dry peeling device is operated at a predetermined temperature and for a predetermined time in an inert gas atmosphere. a dry peeling step of increasing the degree of peeling for solid powder; Eco-friendly mass production method of high-purity graphene flakes, characterized in that it further comprises.
3. The method of claim 2,
The solid powder that has undergone the dry peeling step is put into a hydrogen-functionalized device having an internal temperature at a predetermined temperature, and a mixed gas in which an inert gas and a hydrogen gas are mixed in a predetermined volume ratio into the hydrogen-functionalized device into which the solid powder is introduced. After flowing for a predetermined time, a hydrogen functionalization step of rapidly cooling the solid powder put into the hydrogen functionalization device; Eco-friendly mass production method of high-purity graphene flakes, characterized in that it further comprises.

Images