CN112225204B - Control method and equipment for graphene orientation in graphene sponge - Google Patents
Control method and equipment for graphene orientation in graphene sponge Download PDFInfo
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- CN112225204B CN112225204B CN202011132558.7A CN202011132558A CN112225204B CN 112225204 B CN112225204 B CN 112225204B CN 202011132558 A CN202011132558 A CN 202011132558A CN 112225204 B CN112225204 B CN 112225204B
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Abstract
The invention discloses a control method for graphene orientation in graphene sponge, which comprises the following steps: (1) Preparing graphene oxide dispersion liquid, and performing heat balance at an experimental temperature; (2) The experiment ordered assembly equipment is built, and the regulation and control of the temperature field can be realized by changing the side wall materials; (3) Orderly assembling graphene oxide, injecting the dispersion liquid into a freezing mold after the temperature of the cold plate is stable, and waiting for the solution to be completely frozen; (4) freeze-drying to obtain graphene oxide sponge; (5) steam chemical reduction of hydrazine hydrate. The graphene sponge prepared by the method has a special orientation structure, graphene sponges with different orientation structures can be obtained by regulating and controlling the side wall plates of the freezing cavity, the orientation range is large, and the prepared graphene sponge has high anisotropy and can fully exert the excellent performance of graphene in the plane direction, so that the graphene sponge can be widely applied to the fields of electric conduction, heat conduction and mechanics.
Description
Technical Field
The invention belongs to the technical field of material preparation, relates to a control method and equipment for graphene orientation in graphene sponge, and particularly relates to a method for preparing graphene sponge with different orientation structures by designing a temperature gradient.
Background
Graphene is a kind of material having sp between carbon atoms 2 The hybridized form depends on the combination of sigma bonds and pi bonds to form a novel two-dimensional material of honeycomb-shaped bonds. The graphene has a unique hexagonal crystal structure, and carbon atoms form a huge conjugated large pi bond through pi-pi interaction, and the special bonding structure and the two-dimensional special form endow the graphene with excellent thermal, electric, optical, mechanical and other properties. With the attention of people to light high-performance materials, particularly the requirements of the fields of aerospace, 5G communication, wearable equipment and the like on multifunctional materials, further demands are made for realizing controllable microstructure of the light sponge. The graphene is taken as a two-dimensional material, has natural advantages for constructing a macroscopic body, and becomes the focus of scientists on how to utilize the excellent performance of the graphene, wherein one strategy is to assemble the graphene into the macroscopic bodyThe material fully exerts multiple performances of the nano-scale of the graphene, realizes the spanning from the nano-scale to the macro-scale, and the special structure of the oriented graphene is the only means for maximally realizing the excellent performance of the graphene sheet. The special graphene macroscopic body morphology can optimize macroscopic body performance to different degrees, so that the graphene sponge has special performance.
The current preparation method of the graphene sponge comprises CVD growth synthesis, a porous polymer template method, a chemical reduction method, a hydrothermal reduction self-assembly method, a high-temperature high-pressure self-assembly method, an ice template and other external force induction methods and the like. The directional arrangement of graphene sheets can be promoted by external force induction, and the existing researches can realize the regulation and control of two dimensions on the microstructure of the graphene sponge to realize vertical or horizontal orientation, but few researches on preparing the graphene sponge with a special structure exist at present. Based on flat freezing, the graphene sponge with an oriented structure is prepared by using different heat conductivity materials as the side wall of the freezing cavity and designing and regulating the temperature field of the liquid.
Disclosure of Invention
In order to realize the orientation problem of graphene sheets, materials with different heat conductivity coefficients are used as the side wall of a freezing cavity to regulate and control the temperature field around liquid on the basis of flat freezing, and the invention provides a method for preparing the oriented structure graphene sponge. According to the preparation method, the self-built refrigeration equipment is utilized to prepare the graphene oxide sponge with different directional structures, and the reduced graphene oxide sponge with different directional structures is prepared after the reduction of the graphene oxide sponge.
The invention aims at realizing the following technical scheme:
a control method and equipment for the orientation of graphene in a graphene sponge are provided, and the oriented graphene sponge is prepared by using flat freezing and materials with different heat conductivities as container walls to regulate and control the temperature field of liquid.
A control method for graphene orientation in graphene sponge comprises the following specific steps:
(1) Preparing a stable graphene oxide dispersion liquid:
dispersing graphene oxide with the size of 5-10 micrometers and the concentration of 15-20mg/ml in deionized water, preparing a graphene oxide solution with the concentration of 5-15mg/ml, performing ultrasonic treatment on the solution for 30-60 min at the frequency of 10 KHz-100 KHz to obtain graphene oxide dispersion liquid, and placing the dispersion liquid in a preparation environment at 1-10 ℃ for heat balance;
(2) And (3) building ordered assembly equipment:
the double-layer semiconductor refrigerating sheet is selected as a cold source, an aluminum plate is covered on the surface of the double-layer semiconductor refrigerating sheet and used as a uniform cooling layer, a PT100 patch thermocouple is clamped in the aluminum plate and used for collecting temperature data, meanwhile, the aluminum plate is used as the bottom of a refrigerating container, the aluminum plate is used as a heat sink relative to the outer side of the refrigerating container in a water cooling mode, a main frame of the refrigerating mold is two acrylic plates pulled by four columns, grooves are formed in the inner walls of the two acrylic plates, the two grooves are parallel and are symmetrical along the center, and plates with the same or different heat conductivities are inserted into the grooves to regulate and control a temperature field;
(3) Ordered assembly of graphene oxide:
regulating the temperature of a cold plate in an environment with the constant temperature of 10 ℃, sealing the cold plate and the bottom of a die by utilizing frozen distilled water to form a pentahedron container, injecting graphene oxide aqueous dispersion liquid into the container when the temperature of the whole frame is balanced, and waiting for the dispersion liquid to be completely frozen to obtain a frozen mixture of graphene oxide and ice;
(4) And (3) freeze drying: placing the frozen mixture of graphene oxide and ice into a freeze dryer, freeze-drying at-108 ℃, and obtaining graphene oxide sponge after complete drying;
(5) Chemical vapor reduction: graphene oxide the freeze-dried graphene oxide is placed into a density container filled with hydrazine hydrate, heated for 24 hours at 90 ℃, oxygen-containing functional groups of the graphene oxide are removed, and then the graphene oxide is dried for 12 hours at 100 ℃ to obtain the reduced graphene oxide sponge.
In the invention, the graphene oxide solution in the step (1) is prepared by adopting a chemical method, and the specific preparation steps are as follows: weighing 4g of flake graphite, placing the flake graphite into a beaker, pouring 400-500 ml of concentrated sulfuric acid and 40-50 ml of phosphoric acid into the beaker to prepare a mixed solution, and stirring the mixed solution for 30-60 min at room temperature; placing the beaker into a water bath for water bath heating, adding 16-20 g of potassium permanganate into the solution for 8 times respectively, heating the solution at a constant temperature of 60-70 ℃, taking out the solution after 10-20 h, and cooling at room temperature; after cooling to room temperature, slowly pouring the mixed solution into 600-700 ml of hydrogen peroxide mixed ice water with mass fraction of 30% of 6-7 ml, standing for 20-30 h, filtering out supernatant, and taking the lower solution for centrifugal washing; finally dispersing the washed graphene oxide in deionized water for standby, and controlling the ratio of the graphene oxide to the deionized water to be (5-15) mg:1mL.
Optionally, in the step (2), the temperature field of the solution is regulated by using the total temperature gradient formed by the temperature gradient of the flat cold source vertically upwards and the horizontal temperature gradient formed by the side wall of the freezing cavity (materials with different heat conductivities are used as the side wall of the freezing cavity), so as to regulate the orientation direction of the sheet layer, and prepare the graphene sponge with an orientation structure.
According to the self-built ordered assembly equipment, the total temperature gradient direction can be regulated and controlled by replacing the side wall plate material.
In the invention, a refrigerating system in the built ordered assembling equipment is formed by utilizing a semiconductor refrigerating plate, an aluminum sheet is covered on the surface of the refrigerating plate, a refrigerating cavity is a frame formed by acrylic plates, plates with different heat conductivities can be replaced on two sides of the frame, and the plates can be made of metal materials such as copper and copper alloy, aluminum and aluminum alloy and the like; any material such as plastic material and carbon material may be used as the side wall.
Preferably, plates with the same or different thermal conductivities are inserted into the grooves to regulate the temperature field, wherein the plates of the 1 st groove and the 2 nd groove are selected from aluminum plates, copper plates or stainless steel plates.
In the invention, the built equipment is frozen by distilled water to realize the sealing of the freezing cavity and the bottom cold source, so as to avoid outflow of liquid.
According to the invention, the orientation structure can be adjusted by adjusting the initial temperature of the cold plate, the cooling rate of the cold plate, the concentration of graphene oxide dispersion liquid, the material of the side wall plate of the freezing cavity and the like.
Optionally, the ordered assembly method in the step (3) is applicable to ordered assembly of any other two-dimensional nanomaterial.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the graphene sponge with the directional structure is developed through self-built equipment, an upward temperature field is provided by utilizing a bottom cold source, a horizontal temperature field is provided by the side wall, and the two temperature fields jointly act to form a temperature field with a certain inclination angle, as shown in fig. 2, so that the growth direction of ice crystals is controlled, and the graphene sheet is directionally regulated and controlled to obtain the graphene sponge with the directional structure, so that the graphene sponge has excellent performance.
2. The control method for the graphene orientation can be used for orderly assembling any two-dimensional material, and has a wide application range.
3. According to the graphene sponge structure prepared by the method, the structure of the graphene sponge is changed along with different thermal conductivities of the side wall materials, and the regulation and control of the directional structure can be realized.
4. The size of the directional sponge prepared by the invention can be regulated by regulating the size of the freezing cavity, so that the large-size high-directional graphene sponge can be prepared.
Drawings
FIG. 1 is a schematic diagram of an apparatus for implementing graphene orientation control preparation in accordance with the present invention;
FIG. 2 is a simulated view of the temperature field distribution of the freezing chamber of the present invention;
FIG. 3 is a side physical view of the preparation of the oriented graphene sponge according to the present invention;
FIG. 4 is a SEM image of a graphene sponge prepared in examples 1-3, a1-a 3) a SEM image of a graphene sponge prepared in example 1 using 304 stainless steel, b1-b 3) a SEM image of a graphene sponge prepared in example 2 using Al plates, c1-c 3) a SEM image of a graphene sponge prepared in example 3 using Cu plates;
in the figure, 1: refrigeration plate (cold source), 2: sheet metal-base, 3: acrylic plate, 4: metal plate-sidewall.
Detailed Description
The technical scheme of the present invention is further described below with reference to examples and drawings, but is not limited thereto.
Example 1:
as shown in fig. 1, the present example prepares a directional graphene sponge according to the following steps:
(1) Preparing graphene oxide solution:
preparing graphene oxide by a chemical method: 4g of flake graphite is weighed and placed in a beaker, 450ml of concentrated sulfuric acid and 50ml of phosphoric acid are poured into the beaker to prepare a mixed solution, and the mixed solution is stirred for 40 minutes at room temperature. The beaker was placed in a water bath for water bath heating, 18g of potassium permanganate was added to the solution in 8 portions, respectively, and the solution was heated at a constant temperature of 70℃for 16 hours, taken out and cooled at room temperature. After cooling to room temperature, the mixed solution was slowly poured into 700ml of hydrogen peroxide mixed ice water containing 6ml of 30% by mass fraction, and after standing for 24 hours, the supernatant was filtered off, and the lower layer solution was taken out for centrifugal washing. Finally dispersing the washed graphene oxide in deionized water for standby, and controlling the ratio of the graphene oxide to the deionized water to be 5mg:1mL.
(2) And (3) building ordered assembly equipment:
the metal plate refrigeration equipment selects a 6 cm-6 cm double-layer semiconductor refrigeration sheet with the model number of 135 as a cold source, 2 refrigeration sheets form a 12 cm-6 cm cold source surface, an aluminum plate is covered on the surface to serve as a uniform cooling layer (2 mm thick), a PT100 patch thermocouple is clamped in the aluminum plate and used for collecting temperature data, meanwhile, the aluminum plate serves as the bottom of a refrigeration container, and the aluminum plate serves as a heat sink relative to the outer side of the refrigeration container in a water cooling mode. The main frame of the freezing mould is formed by four acrylic plates (the height is 120mm, the width is 80mm, and the thickness is 3 mm), grooves are formed in the inner walls of the two acrylic plates (the groove depth is 1mm, the groove width is 1 mm), the two grooves are parallel, the distance is 21mm, the two grooves are symmetrical along the center, 304 stainless steel plates with the dimensions of 120mm x 1mm are inserted into the 1 st groove, 304 stainless steel plates with the dimensions of 120mm x 1mm are inserted into the 2 nd groove, and a horizontal temperature field is provided through the side walls;
(3) Ordered assembly and freeze drying of graphene oxide:
(1) The GO aqueous dispersion was diluted to 5mg/ml with distilled water and dispersed with a stirrer for 1 hour. (2) In a refrigeration house with the constant temperature of 10 ℃, a cold source power supply is firstly turned off, a layer of distilled water with the thickness of about 1mm is sprayed on an aluminum plate of the cold source, an acrylic frame with a metal plate is placed on the cold plate, the cold source power supply is turned on, and the bottom of a container is closed by chilled distilled water to form a 5-surface container. (3) The cold plate temperature was adjusted to about-30 ℃, the cold plate was operated, and the apparatus was temperature equilibrated (about 5 min). (4) After the temperature of the equipment is balanced, injecting graphene oxide aqueous dispersion liquid with the height of about 115mm into a container, starting to freeze, and enabling ice crystals to stably grow until the dispersion liquid is completely frozen, so as to obtain a frozen mixture of graphene oxide and ice. (5) Placing the obtained frozen mixture of graphene oxide and ice into a freeze dryer, drying for more than 144 hours at the temperature of minus 108 ℃, and obtaining the graphene oxide sponge after the mixture is completely dried;
(4) Chemical vapor reduction:
and (3) placing the obtained graphene oxide sponge into a closed container filled with hydrazine hydrate, heating for 24 hours at 90 ℃, removing oxygen-containing functional groups of the graphene oxide, and drying for 12 hours at 100 ℃ to obtain the reduced graphene oxide sponge.
According to the embodiment, the graphene oxide sheets are in a radial shape which is symmetrical in center and inclined upwards by observing the side surface of the sample, and as can be seen from the physical image and the scanning image in fig. 1 and 3, the graphene nano sheets are arranged in an oriented manner according to a certain direction included angle under the regulation of 304 stainless steel.
The samples were tested for mechanical compression and thermal conductivity. The compressive strength was 1.4KPa,0.9KPa and 1.0KPa at 10% deformation, 2.3KPa,1.4KPa and 1.4KPa at 30% deformation, 3.2KPa,2.2KPa and 2.1KPa at 50% deformation, and the thermal conductivity was 0.0181W m in three directions X, Y and Z, respectively - 1 K -1 ，0.0158W m -1 K -1 And 0.0155, 0.0155W m -1 K -1 The anisotropy of the oriented graphene sponge is reflected.
Example 2:
as shown in fig. 1, the present example prepares a directional graphene sponge according to the following steps:
(1) Preparing graphene oxide solution:
preparing graphene oxide by a chemical method: 4g of flake graphite is weighed and placed in a beaker, 450ml of concentrated sulfuric acid and 50ml of phosphoric acid are poured into the beaker to prepare a mixed solution, and the mixed solution is stirred for 40 minutes at room temperature. The beaker was placed in a water bath for water bath heating, 18g of potassium permanganate was added to the solution in 8 portions, respectively, and the solution was heated at a constant temperature of 70℃for 16 hours, taken out and cooled at room temperature. After cooling to room temperature, the mixed solution was slowly poured into 700ml of hydrogen peroxide mixed ice water containing 6ml of 30% by mass fraction, and after standing for 24 hours, the supernatant was filtered off, and the lower layer solution was taken out for centrifugal washing. Finally dispersing the washed graphene oxide in deionized water for standby, and controlling the ratio of the graphene oxide to the deionized water to be 5mg:1mL.
(2) And (3) building ordered assembly equipment:
the metal plate refrigeration equipment selects a 6 cm-6 cm double-layer semiconductor refrigeration sheet with the model number of 135 as a cold source, 2 refrigeration sheets form a 12 cm-6 cm cold source surface, an aluminum plate is covered on the surface to serve as a uniform cooling layer (2 mm thick), a PT100 patch thermocouple is clamped in the aluminum plate and used for collecting temperature data, meanwhile, the aluminum plate serves as the bottom of a refrigeration container, and the aluminum plate serves as a heat sink relative to the outer side of the refrigeration container in a water cooling mode. The main frame of the freezing mould is formed by four acrylic plates (the height is 120mm, the width is 80mm, and the thickness is 3 mm) which are pulled by four columns, grooves are formed in the inner walls of the two acrylic plates (the groove depth is 1mm, the groove width is 1 mm), the two grooves are parallel, the distance is 21mm, the two grooves are symmetrical along the center, aluminum plates with the dimensions of 120mm x 1mm are inserted into the 1 st groove, aluminum plates with the dimensions of 120mm x 1mm are inserted into the 2 nd groove, and a horizontal temperature field is provided through the side walls;
(3) Ordered assembly and freeze drying of graphene oxide:
(1) The GO aqueous dispersion was diluted to 5mg/ml with distilled water and dispersed with a stirrer for 1 hour. (2) In a refrigeration house with the constant temperature of 10 ℃, a cold source power supply is firstly turned off, a layer of distilled water with the thickness of about 1mm is sprayed on an aluminum plate of the cold source, an acrylic frame with a metal plate is placed on the cold plate, the cold source power supply is turned on, and the bottom of a container is closed by chilled distilled water to form a 5-surface container. (3) The cold plate temperature was adjusted to about-30 ℃, the cold plate was operated, and the apparatus was temperature equilibrated (about 5 min). (4) After the temperature of the equipment is balanced, injecting graphene oxide aqueous dispersion liquid with the height of about 115mm into a container, starting to freeze, and enabling ice crystals to stably grow until the dispersion liquid is completely frozen, so as to obtain a frozen mixture of graphene oxide and ice. (5) Placing the obtained frozen mixture of graphene oxide and ice into a freeze dryer, drying for more than 144 hours at the temperature of minus 108 ℃, and obtaining the graphene oxide sponge after the mixture is completely dried;
(4) Chemical vapor reduction:
and (3) placing the obtained graphene oxide sponge into a closed container filled with hydrazine hydrate, heating for 24 hours at 90 ℃, removing oxygen-containing functional groups of the graphene oxide, and drying for 12 hours at 100 ℃ to obtain the reduced graphene oxide sponge.
According to the embodiment, the graphene oxide sheets are in a radial shape which is symmetrical in center and inclined upwards by observing the side surface of the sample, and as can be seen from the physical image and the scanning image in fig. 1 and 3, the graphene nano sheets are arranged in an oriented mode according to a certain direction included angle under the regulation and control of the aluminum plate, and compared with 304 stainless steel, the included angle between the graphene sheets and the axis is increased.
The samples were tested for mechanical compression and thermal conductivity. The compressive strength was 1.6KPa,1.7KPa and 1.1KPa respectively at 10% deformation and 2.3KPa,2.2KPa and 1.6KPa respectively at 30% deformation, and the thermal conductivity was 0.0164W m at 3.2KPa,2.8KPa and 2.5KPa respectively at 50% deformation in the directions X, Y and Z - 1 K -1 ，0.0176W m -1 K -1 And 0.0171/0.0171W m -1 K -1 The anisotropy of the graphene sponge is reflected, and compared with the example 1, after the side wall is replaced by the aluminum plate with higher heat conductivity, the anisotropy of the graphene sponge in three directions under the deformation of 30% -50% is more obvious.
Example 3
As shown in fig. 1, the present example prepares a directional graphene sponge according to the following steps:
(1) Preparing graphene oxide solution:
preparing graphene oxide by a chemical method: 4g of flake graphite is weighed and placed in a beaker, 450ml of concentrated sulfuric acid and 50ml of phosphoric acid are poured into the beaker to prepare a mixed solution, and the mixed solution is stirred for 40 minutes at room temperature. The beaker was placed in a water bath for water bath heating, 18g of potassium permanganate was added to the solution in 8 portions, respectively, and the solution was heated at a constant temperature of 70℃for 16 hours, taken out and cooled at room temperature. After cooling to room temperature, the mixed solution was slowly poured into 700ml of hydrogen peroxide mixed ice water containing 6ml of 30% by mass fraction, and after standing for 24 hours, the supernatant was filtered off, and the lower layer solution was taken out for centrifugal washing. Finally dispersing the washed graphene oxide in deionized water for standby, and controlling the ratio of the graphene oxide to the deionized water to be 5mg:1mL.
(2) And (3) building ordered assembly equipment:
the metal plate refrigeration equipment selects a 6 cm-6 cm double-layer semiconductor refrigeration sheet with the model number of 135 as a cold source, 2 refrigeration sheets form a 12 cm-6 cm cold source surface, an aluminum plate is covered on the surface to serve as a uniform cooling layer (2 mm thick), a PT100 patch thermocouple is clamped in the aluminum plate and used for collecting temperature data, meanwhile, the aluminum plate serves as the bottom of a refrigeration container, and the aluminum plate serves as a heat sink relative to the outer side of the refrigeration container in a water cooling mode. The main frame of the freezing mould is formed by four acrylic plates (the height is 120mm, the width is 80mm, and the thickness is 3 mm) which are pulled by four columns, grooves are formed in the inner walls of the two acrylic plates (the groove depth is 1mm, the groove width is 1 mm), the two grooves are parallel, the distance is 21mm, the two grooves are symmetrical along the center, 1 st groove is inserted with 1 st copper plate 1 of 120mm 1mm, 2 nd groove is inserted with 2 nd copper plate of 120mm 1mm, and a horizontal temperature field is provided through the side wall;
(3) Ordered assembly and freeze drying of graphene oxide:
(1) The GO aqueous dispersion was diluted to 5mg/ml with distilled water and dispersed with a stirrer for 1 hour. (2) In a refrigeration house with the constant temperature of 10 ℃, a cold source power supply is firstly turned off, a layer of distilled water with the thickness of about 1mm is sprayed on an aluminum plate of the cold source, an acrylic frame with a metal plate is placed on the cold plate, the cold source power supply is turned on, and the bottom of a container is closed by chilled distilled water to form a 5-surface container. (3) The cold plate temperature was adjusted to about-30 ℃, the cold plate was operated, and the apparatus was temperature equilibrated (about 5 min). (4) After the temperature of the equipment is balanced, injecting graphene oxide aqueous dispersion liquid with the height of about 115mm into a container, starting to freeze, and enabling ice crystals to stably grow until the dispersion liquid is completely frozen, so as to obtain a frozen mixture of graphene oxide and ice. (5) Placing the obtained frozen mixture of graphene oxide and ice into a freeze dryer, drying for more than 144 hours at the temperature of minus 108 ℃, and obtaining the graphene oxide sponge after the mixture is completely dried;
(4) Chemical vapor reduction:
and (3) placing the obtained graphene oxide sponge into a closed container filled with hydrazine hydrate, heating for 24 hours at 90 ℃, removing oxygen-containing functional groups of the graphene oxide, and drying for 12 hours at 100 ℃ to obtain the reduced graphene oxide sponge.
According to the embodiment, the graphene oxide sheets are seen to be in a radial shape which is symmetrical in center and is inclined upwards by observing the side surface of a sample, as can be seen from the physical image and the scanning image in fig. 1 and 3, the graphene nano sheets are directionally arranged according to a certain direction included angle under the regulation and control of the copper plate, when the copper plate is used as a material, the thermal conductivity is higher, compared with aluminum and stainless steel, the temperature at the same position is lower, the vertical temperature gradient is smaller, the horizontal temperature gradient is formed from the heat transmissibility of the solution to the middle, when the thermal conductivity of the two sides is higher, the vertical temperature gradient is smaller, the horizontal temperature gradient is larger, the layers are horizontally arranged, and the included angle in the symmetrical structure is larger.
The samples were tested for mechanical compression and thermal conductivity. The compressive strength was 0.5KPa,1.7KPa and 1.5KPa at 10% deformation and 1.1KPa,2.6KPa and 2.1KPa at 30% deformation, and the thermal conductivity was 0.0108W m at 1.9KPa,3.4KPa and 2.9KPa at 50% deformation in the three directions X, Y and Z - 1 K -1 ，0.0190W m -1 K -1 And 0.0222W m -1 K -1 The anisotropy of the graphene sponge is reflected, and compared with examples 1 and 2, after the side wall is replaced by a copper plate with higher heat conductivity, the anisotropy of the graphene sponge in three directions under the deformation of 10% -50% is more obvious.
The foregoing embodiments are preferred embodiments of the present invention, but the present invention is not limited thereto, and modifications and equivalents of the technical solution of the present invention are all intended to be included in the scope of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (7)
1. The method for controlling the orientation of the graphene in the graphene sponge is characterized by comprising the following steps of:
(1) Preparing a stable graphene oxide dispersion liquid: dispersing graphene oxide with the size of 5-10 microns and the concentration of 15-20mg/ml in deionized water to prepare a graphene oxide solution, and regulating the concentration of the solution to 5-15mg/ml; carrying out ultrasonic treatment on the solution for 30-60 min, wherein the ultrasonic frequency is 10 KHz-100 KHz, so as to obtain graphene oxide dispersion liquid; placing the dispersion liquid in a preparation environment of 1-10 ℃ for heat balance;
(2) And (3) building ordered assembly equipment:
utilize the semiconductor refrigeration board to build the refrigerating system in the ordered equipment to cover the aluminium piece on refrigeration board surface, use the ya keli board to constitute the freezing cavity frame, the frame both sides are the copper, specifically:
the method comprises the steps of selecting a double-layer semiconductor refrigerating sheet as a cold source, coating an aluminum plate on the surface of the double-layer semiconductor refrigerating sheet as a uniform cooling layer, clamping PT100 patch thermocouples in the aluminum plate for collecting temperature data, simultaneously taking the aluminum plate as the bottom of a refrigerating container, taking the aluminum plate as a heat sink relative to the outer side of the refrigerating container in a water cooling mode, wherein a main frame of a refrigerating mold is two acrylic plates pulled by four columns, grooves are formed in the inner walls of the two acrylic plates, the two grooves are parallel and are symmetrical along the center, and inserting copper plates with the same heat conductivity into the grooves for regulating and controlling a temperature field;
(3) Ordered assembly of graphene oxide: regulating the temperature of a cold plate in an environment with the constant temperature of 10 ℃, sealing the cold plate and the bottom of a die by utilizing frozen distilled water to form a pentahedron container, injecting graphene oxide dispersion liquid into the container when the temperature of the whole frame is balanced, and waiting for the dispersion liquid to be completely frozen to obtain a frozen mixture of graphene oxide and ice;
(4) And (3) freeze drying: placing the frozen mixture of graphene oxide and ice into a freeze dryer, freeze-drying at-108 ℃, and obtaining graphene oxide sponge after complete drying;
(5) Chemical vapor reduction: and (3) placing the freeze-dried graphene oxide into a density container filled with hydrazine hydrate, heating for 24 hours at 90 ℃, removing oxygen-containing functional groups of the graphene oxide, and drying for 12 hours at 100 ℃ to obtain the graphene sponge with the directional structure.
2. The method for controlling the orientation of graphene in the graphene sponge according to claim 1, wherein the temperature field of the solution is regulated and controlled by utilizing a total temperature gradient formed by a temperature gradient of a flat cold source vertically upwards and a horizontal temperature gradient formed by the side wall of the freezing cavity, and materials with different heat conductivities are used as the side wall of the freezing cavity, so that the orientation direction of a sheet layer is regulated, and the graphene sponge with an orientation structure is prepared.
3. The method for controlling the orientation of graphene in a graphene sponge according to claim 1, wherein the specific preparation steps of the graphene oxide solution in the step (1) are as follows: weighing 4g of flake graphite, placing the flake graphite into a beaker, pouring 400-500 ml of concentrated sulfuric acid and 40-50 ml of phosphoric acid into the beaker to prepare a mixed solution, and stirring the mixed solution for 30-60 min at room temperature; placing the beaker into a water bath for water bath heating, adding 16-20 g of potassium permanganate into the solution for 8 times respectively, heating the solution at a constant temperature of 60-70 ℃, taking out the solution after 10-20 h, and cooling at room temperature; after cooling to room temperature, slowly pouring the mixed solution into 600-700 ml of hydrogen peroxide mixed ice water with mass fraction of 30% of 6-7 ml, standing for 20-30 h, filtering out supernatant, and taking the lower solution for centrifugal washing; and finally dispersing the washed graphene oxide in deionized water for standby.
4. The method for controlling the orientation of graphene in the graphene sponge according to claim 1, wherein plates with the same or different thermal conductivities are inserted into the grooves to regulate and control a temperature field, and the plates of the 1 st groove and the 2 nd groove are selected from aluminum plates, copper plates or stainless steel plates.
5. The control method of the graphene orientation in the graphene sponge according to any one of claims 1 to 4, wherein the self-built ordered assembly equipment realizes regulation and control of the total temperature gradient direction by replacing the side wall plate material.
6. The control method for the orientation of graphene in a graphene sponge according to any one of claims 1 to 4, wherein the sealing of the freezing cavity and the bottom cold source is achieved by using distilled water in the built equipment, and outflow of liquid is avoided.
7. The method for controlling the orientation of graphene in the graphene sponge according to any one of claims 1 to 4, wherein the graphene sponge with the orientation structure is prepared by adjusting the initial temperature of a cold plate, the cooling rate of the cold plate, the concentration of graphene oxide dispersion liquid and the material of a side wall plate of a freezing cavity.
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| CN202011132558.7A CN112225204B (en) | 2020-10-21 | 2020-10-21 | Control method and equipment for graphene orientation in graphene sponge |
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| CN202011132558.7A CN112225204B (en) | 2020-10-21 | 2020-10-21 | Control method and equipment for graphene orientation in graphene sponge |
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| CN113044835A (en) * | 2021-04-09 | 2021-06-29 | 浙江大学 | Preparation method of two-dimensional sheet material vertical orientation assembly |
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