CN109734076B - Preparation method of large-area high-strength super-elastic graphene foam material - Google Patents
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Abstract
The invention relates to a preparation method of a large-area high-strength super-elasticity graphene foam material, and belongs to the technical field of preparation of three-dimensional graphene materials. Reducing a foamed graphene oxide solution to generate a graphene hydrogel block, freezing, melting, paving a layer of the graphene hydrogel block in a wet state, transversely and longitudinally compressing to obtain a layer of large-area graphene hydrogel, repeatedly paving the graphene hydrogel block on the large-area graphene hydrogel, compressing to obtain a multilayer composite large-area graphene hydrogel, and naturally air-drying to obtain the large-area high-strength super-elasticity graphene foam material. The method is simple and easy to operate, the expandability is strong, and the area of the prepared graphene foam material can reach 1m2Above, density of 30mg/cm3～90mg/cm3The ultimate compression rebound strain reaches more than 95 percent, and the ultimate compression strength reaches more than 20 MPa.
Description
Technical Field
The invention relates to a preparation method of a hyperelastic graphene foam material, and belongs to the technical field of preparation of three-dimensional graphene materials.
Background
The graphene foam is a macroscopic light material with a three-dimensional porous structure, which is assembled by two-dimensional graphene nano materials with high electric conductivity, high heat conductivity and high flexibility, and has a huge application prospect in the fields of energy storage and conversion, environmental management, energy conservation and emission reduction, mechanical sensing, electromagnetic shielding, light flame retardance and the like. The existing super-elastic graphene foam material (the ultimate compression rebound strain is more than 90 percent) has the defect thatThe density of the material is extremely low (less than 10 mg/cm)3) And a lower ultimate compressive strength (less than 2 MPa). This is because when the large-area super-elastic graphene foam material is prepared by the prior art, the structure is very uneven and the compression elasticity is deteriorated due to the disordered liquid crystal phase and uneven heat transfer of graphene oxide, such as chinese patent nos. CN 104925787B and CN 106006615B. In addition, the freeze drying technology is generally used in the preparation process, and compared with the normal pressure drying method, the method is time-consuming and energy-consuming and is not suitable for large-scale preparation, such as the invention patent CN 106809822B.
Disclosure of Invention
Aiming at the problem that the super-elastic graphene foam material with large area, high density and high strength cannot be prepared at present, the invention provides a preparation method of the large-area high-strength super-elastic graphene foam material, and the area of the graphene foam material prepared by the method can reach 1m2Above, density of 30mg/cm3～90mg/cm3The ultimate compression rebound strain reaches more than 95 percent, and the ultimate compression strength reaches more than 20 MPa.
The purpose of the invention is realized by the following technical scheme.
A preparation method of a large-area high-strength superelasticity graphene foam material comprises the following steps:
(1) adding a reducing agent and a surfactant into a graphene oxide aqueous solution with the concentration of 6mg/m L-20 mg/m L, then stirring to foam the mixed solution, wherein the volume multiple of the foamed mixed solution is 1.5-2.5 (namely the volume of the mixed solution after foaming is 1.5-2.5 times of the volume of the mixed solution before foaming), pouring the foamed mixed solution into a mold, and carrying out reduction reaction at the temperature of below 80 ℃ to obtain a graphene hydrogel block;
(2) completely freezing and freezing the graphene hydrogel block at-20 to-10 ℃, and then thawing and completely thawing at the temperature of below 70 ℃ to obtain an ice crystal recast graphene hydrogel block;
(3) tightly paving more than two graphene hydrogel blocks recast by ice crystals in a wet state, transversely compressing the graphene hydrogel blocks in a small proportion in the length direction or/and the width direction to enable adjacent graphene hydrogel blocks to be tightly contacted, longitudinally compressing the graphene hydrogel blocks in a large proportion in the thickness direction, and regulating and controlling the internal three-dimensional structure of the graphene hydrogel blocks to obtain large-area graphene hydrogel;
wherein, the transverse compression ratio (the ratio of the compression amount of the length or the width to the length or the width before compression) is 5 to 20 percent, and the longitudinal compression ratio (the ratio of the compression amount of the thickness to the thickness before compression) is 80 to 90 percent; determining the size of the tiled area of the ice crystal recast graphene hydrogel in a wet state according to the size of the area of the prepared super-elastic graphene foam material;
(4) and (4) naturally air-drying the large-area graphene hydrogel prepared in the step (3) to obtain a large-area high-strength super-elasticity graphene foam material.
Further, tightly paving two or more pieces of ice crystal recast graphene hydrogel on the large-area graphene hydrogel prepared in the step (3) in a wet state by one layer, and then respectively performing transverse compression and longitudinal compression according to the operation of the step (3) to obtain two layers of composite large-area graphene hydrogel; by analogy, preparing the multilayer composite large-area graphene hydrogel, and naturally air-drying the multilayer composite large-area graphene hydrogel to obtain the large-area high-strength super-elasticity graphene foam material. The number of layers of large-area graphene hydrogel composite is determined according to the thickness of the prepared super-elastic graphene foam material.
Further, in the step (1), the reduction reaction is preferably carried out at 60 to 80 ℃ for 8 to 24 hours.
Further, in the step (1), the reducing agent is vitamin C, hydrazine hydrate, hydroiodic acid, ethylenediamine or sodium borohydride, and the addition amount of the reducing agent is 10-250% of the mass of the graphene oxide; the surfactant is more than one of anionic surfactant, zwitterionic surfactant and nonionic surfactant, preferably sodium dodecyl sulfate, alkyl glycoside or cocamidopropyl betaine, and the addition amount of the surfactant is 50-150% of the mass of the graphene oxide.
Further, in the step (1), the shape of the graphene hydrogel bulk is preferably a rectangular parallelepiped or a cube.
Further, the longitudinal compression ratio is preferably 85% to 90%.
Has the advantages that:
the structure and the density of the graphene foam material can be changed in a wet state compression mode, the ultimate compression strength and the conductivity of the graphene foam material are obviously improved, the graphene foam material can be subjected to three-dimensional macroscopic assembly, and large-area preparation on the appearance size is realized. The graphene foam material prepared by the method has a directionally arranged multi-arch structure in the interior, the spacing between the multi-arches is 5-30 mu m, and the density reaches 30mg/cm3～90mg/cm3Area can reach 1m2And above, the ultimate compression rebound strain reaches above 95%, the ultimate compression strength reaches above 20MPa, and the electrical conductivity reaches above 100S/m. The method is simple and easy to operate, has strong expandability, and can be used for in-situ large-area preparation in atmospheric atmosphere.
Drawings
Fig. 1 is a scanning electron microscope image of a cross section of the superelastic graphene foam material prepared in example 1 at low magnification.
Fig. 2 is a scanning electron microscope image of a cross section of the superelastic graphene foam material prepared in example 1 at high magnification.
Fig. 3 is a compression test stress-strain curve of the superelastic graphene foam material prepared in example 1.
Detailed Description
The invention is further illustrated by the following figures and detailed description, wherein the process is conventional unless otherwise specified, and the starting materials are commercially available from a public disclosure without further specification.
In the following examples:
the size of the inner cavity of the stainless steel die is 12cm × 8cm × 6cm (length × width × height);
calculation of the density: measuring the specific size of the prepared super-elastic graphene foam material by using a ruler, calculating the volume (V), weighing to obtain the mass (M), and finally calculating the density (rho-M/V);
calculating the electrical conductivity, namely measuring the resistance (R) of the prepared super-elastic graphene foam material by using an electrochemical workstation, and finally calculating the electrical conductivity (sigma-L/R S) according to the sectional area (S) and the length (L);
and (4) SEM characterization: a JSM-7500F model cold field emission scanning electron microscope is adopted.
Compressive stress-strain curve test was carried out using an AGS-X model electronic universal tester manufactured by Shimadzu corporation, in which the compression rate was 10mm/min and the size of the test specimen was 5mm × 6mm × 6mm (length × width × height).
Example 1
(1) A beaker with the thickness of 500m L is filled with 100m L concentration of graphene oxide aqueous solution with the concentration of 12mg/m L, 2.4g of vitamin C is firstly added, the vitamin C is completely dissolved by stirring, then 2.4m L mass percent of alkyl glycoside solution with the mass fraction of 50 percent is added, then the mechanical stirring is rapidly carried out for 5min at the rotating speed of 2500r/min, the foaming volume multiple of the mixed solution is about 2.0, the mixed solution is poured into a stainless steel mould, and the reduction reaction is carried out for 12h at the temperature of 70 ℃, so as to obtain a graphene hydrogel block;
(2) freezing the graphene hydrogel at-10 ℃ for 12h, and then thawing and completely thawing at 20 ℃ to obtain an ice crystal recast graphene hydrogel block;
(3) the graphene hydrogel block is tightly and flatly laid on a substrate in a floor tile mode in a wet state, and the flat area is about 0.5m2(ii) a Then, respectively carrying out small-proportion transverse compression on the length direction and the width direction of the graphene hydrogel block by using a flat plate to ensure that the adjacent graphene hydrogel blocks are in close contact, wherein the transverse compression proportion is about 10%, and then carrying out longitudinal large-proportion compression on the thickness (or height) direction of the graphene hydrogel block, wherein the longitudinal compression proportion is about 90%, so as to obtain a layer of large-area graphene hydrogel;
(4) repeating the step (3) by taking the large-area graphene hydrogel prepared in the step (3) as a substrate to obtain two-layer composite large-area graphene hydrogel; and (4) repeating the step (3) by taking the two layers of large-area composite graphene hydrogel as a substrate to obtain three layers of large-area composite graphene hydrogel;
(5) and (4) naturally air-drying the three-layer composite large-area graphene hydrogel prepared in the step (4) to obtain a large-area high-strength super-elasticity graphene foam material.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 60mg/cm3The conductivity can reach 378S/m; the internal microstructure of the graphene material is in a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 μm (the multi-arch spacing refers to the maximum distance between upper and lower layers of graphene forming a multi-arch), as shown in fig. 1 and 2; the ultimate compression rebound strain reaches 97 percent, and the ultimate compression strength reaches 47MPa, as shown in figure 3.
Example 2
(1) Filling 80m of graphene oxide aqueous solution with L concentration of 16mg/m L in a beaker of 500m L, firstly adding 2.6g of vitamin C, stirring to completely dissolve the vitamin C, then adding 2.6m of L mass percent of alkyl glycoside solution, then rapidly and mechanically stirring for 5min at the rotating speed of 2500r/min to ensure that the foaming volume multiple of the mixed solution is about 2.5, pouring the mixed solution into a stainless steel mold, and carrying out reduction reaction for 12h at 70 ℃ to obtain a graphene hydrogel block;
the graphene hydrogel bulk prepared in this example was processed according to the steps (2) to (5) in example 1, and accordingly, a large-area high-strength superelastic graphene foam material was obtained.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 64mg/cm3The electric conductivity is up to 391S/m, the ultimate compression rebound strain is up to 97%, the ultimate compression strength is up to 51MPa, the internal microstructure presents a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 μm.
Example 3
(1) A beaker with the thickness of 500m L is filled with a graphene oxide aqueous solution with the concentration of 120m L of 8mg/m L, 2.9g of vitamin C is firstly added, the vitamin C is completely dissolved by stirring, then an alkyl glycoside solution with the mass fraction of 2m L of 50 percent is added, then the mechanical stirring is rapidly carried out for 5min at the rotating speed of 2500r/min, the foaming volume multiple of the mixed solution is about 1.5, the mixed solution is poured into a stainless steel mold, and the reduction reaction is carried out for 12h at the temperature of 70 ℃, so as to obtain a graphene hydrogel block;
the graphene hydrogel prepared in this example is processed according to the steps (2) to (5) in example 1, and accordingly, a large-area high-strength superelastic graphene foam material is obtained.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 57mg/cm3The conductivity can reach 334S/m, the ultimate compression rebound strain reaches 97%, the ultimate compression strength can reach 40MPa, the internal microstructure presents a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 μm.
Example 4
On the basis of the example 1, the freezing at-10 ℃ for 12h in the step (2) of the example 1 is replaced by the freezing at-15 ℃ for 10h, and other steps and conditions are the same as those of the example 1, so that the large-area high-strength superelasticity graphene foam material is obtained correspondingly.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 60mg/cm3The electric conductivity can reach 358S/m, the ultimate compression rebound strain reaches 97%, the ultimate compression strength reaches 54MPa, the internal microstructure presents a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 μm.
Example 5
On the basis of example 1, the area of the graphene hydrogel block laid in step (3) of example 1 is from 0.5m2Replacement to 1.5m2Meanwhile, the transverse compression ratio is replaced by 15% from 10%, and the longitudinal compression ratio is replaced by 85% from 90%, and other steps and conditions are the same as those of example 1, so that the large-area high-strength super-elastic graphene foam material is obtained.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 42mg/cm3The electric conductivity can reach 215S/m, the ultimate compressive strain reaches 97%, the ultimate compressive strength reaches 33MPa, the internal microstructure presents a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 mu m.
Example 6
On the basis of the embodiment 1, the three-layer composite large-area graphene hydrogel prepared in the step (4) of the embodiment 1 is replaced by the five-layer composite large-area graphene hydrogel, and other steps and conditions are the same as those of the embodiment 1, so that the large-area high-strength superelasticity graphene foam material is obtained correspondingly.
Tests prove that the density of the super-elastic graphene foam material prepared by the embodiment is about 60mg/cm3The conductivity can reach 368S/m, the ultimate compression rebound strain can reach 97%, the ultimate compression strength can reach 45MPa, the internal microstructure presents a directionally arranged multi-arch structure, and the multi-arch spacing is 5-30 mu m.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A preparation method of a large-area high-strength superelasticity graphene foam material is characterized by comprising the following steps: the method comprises the following steps:
(1) adding a reducing agent and a surfactant into a graphene oxide aqueous solution with the concentration of 6mg/m L-20 mg/m L, then stirring to foam the mixed solution, wherein the foaming volume multiple is 1.5-2.5, pouring the foamed mixed solution into a mold, and carrying out reduction reaction at the temperature of below 80 ℃ to obtain a graphene hydrogel block;
(2) completely freezing and freezing the graphene hydrogel block at-20 to-10 ℃, and then thawing and completely thawing at the temperature of below 70 ℃ to obtain an ice crystal recast graphene hydrogel block;
(3) tightly paving more than two ice crystal recast graphene hydrogel blocks in a wet state to form a layer, transversely compressing the graphene hydrogel blocks in a small proportion in the length direction or/and the width direction, wherein the transverse compression proportion is 5% -20%, longitudinally compressing the graphene hydrogel blocks in a large proportion in the thickness direction, and the longitudinal compression proportion is 80% -90%, so as to obtain large-area graphene hydrogel;
(4) naturally air-drying the large-area graphene hydrogel prepared in the step (3) to obtain a large-area high-strength super-elasticity graphene foam material;
the surfactant is sodium dodecyl sulfate, alkyl glycoside or cocamidopropyl betaine, and the addition amount of the surfactant is 50-150% of the mass of the graphene oxide.
2. The preparation method of the large-area high-strength superelastic graphene foam material according to claim 1, wherein the preparation method comprises the following steps: the method further comprises the steps of:
tightly paving two or more than two pieces of ice crystal recast graphene hydrogel on the large-area graphene hydrogel prepared in the step (3) in a wet state by one layer, and respectively performing transverse compression and longitudinal compression according to the operation of the step (3) to obtain two layers of composite large-area graphene hydrogel; by analogy, preparing the multilayer composite large-area graphene hydrogel, and naturally air-drying the multilayer composite large-area graphene hydrogel to obtain the large-area high-strength super-elasticity graphene foam material.
3. The preparation method of large-area high-strength superelastic graphene foam material according to claim 1 or 2, wherein: in the step (1), the reduction reaction is carried out for 8 to 24 hours at a temperature of between 60 and 80 ℃.
4. The preparation method of large-area high-strength superelastic graphene foam material according to claim 1 or 2, wherein: in the step (1), the reducing agent is vitamin C, hydrazine hydrate, hydroiodic acid, ethylenediamine or sodium borohydride, and the addition amount of the reducing agent is 10-250% of the mass of the graphene oxide.
5. The preparation method of large-area high-strength superelastic graphene foam material according to claim 1 or 2, wherein: in the step (1), the graphene hydrogel block is cuboid.
6. The preparation method of large-area high-strength superelastic graphene foam material according to claim 1 or 2, wherein: in the step (3), the longitudinal compression ratio is 85-90%.
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| CN103224229A (en) * | 2013-04-15 | 2013-07-31 | 中国科学院宁波材料技术与工程研究所 | Method for rapid preparation of graphene powder by freezing filtration |
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