A composite graphene oxide liquid crystal slurry, a preparation method and application thereof

Abstract

The application provides a composite graphene oxide liquid crystal slurry as well as a preparation method and application thereof. The application selects graphene oxide with a carbon-oxygen ratio of 1.5-2.5 and a sheet size of 10-80 mu m, and prepares the graphene oxide into a concentration of 5-20 mg / mL, so that the liquid crystal structure has high resistance to interference of inorganic powder, uniform loading of the inorganic powder is realized under the premise of maintaining the liquid crystal ordered structure and interlayer force, and the dense composite film is converted into a three-dimensional porous aerogel through chemical foaming treatment, the prepared three-dimensional porous aerogel has a three-dimensional porous network, the pore wall is smooth and dense, and the inorganic powder is uniformly distributed in the pore wall.

Description

Technical Field

[0001] This invention belongs to the field of aerogel composite material technology, specifically relating to a composite graphene oxide liquid crystal slurry, its preparation method, and its application. Background Technology

[0002] Aerogels are novel nanomaterials with a three-dimensional porous network structure, low density, high specific surface area, and low thermal conductivity, and have broad application prospects in adsorption separation, thermal insulation, catalytic support, and environmental remediation. Graphene oxide (GO) is an ideal precursor for aerogel preparation due to its excellent mechanical properties, abundant functional groups, and good self-assembly characteristics.

[0003] Existing methods for preparing GO aerogels mainly include hydrothermal methods, freeze-drying methods, and template methods. However, pure GO aerogels suffer from problems such as limited functionality, insufficient mechanical strength, and high cost. To address these issues, researchers have attempted to introduce functional inorganic powder fillers into the GO matrix. Among these, mineral powders offer advantages such as wide availability, low cost, environmental friendliness, and diverse functions, making them ideal fillers for achieving low-cost functionalization.

[0004] However, in the prior art, the method of combining inorganic powder with graphene oxide usually has the following problems: (1) The addition of inorganic powder will destroy the ordered liquid crystal structure of graphene oxide, resulting in a significant decrease in the mechanical properties of subsequent films and aerogels; (2) It is difficult to achieve uniform dispersion of inorganic powder between graphene oxide layers, and agglomeration and interface defects are likely to occur; (3) Aerogels prepared by traditional methods are prone to pore structure collapse during the drying process, and the introduction of inorganic powder may exacerbate this problem. Summary of the Invention

[0005] To address the problem in existing technologies where it is difficult to maintain the structure of graphene oxide aerogels after the addition of inorganic powders, leading to a decrease in the mechanical properties of aerogel materials, this invention provides a composite graphene oxide liquid crystal slurry, its preparation method, and its applications. This invention selects graphene oxide with a carbon-to-oxygen ratio of 1.5-2.5 and a sheet size of 10μm-80μm, and prepares it at a concentration of 5mg / mL-20mg / mL. This ensures that the liquid crystal structure has high tolerance to interference from inorganic powders, achieving uniform loading of inorganic powders while maintaining the ordered structure and interlayer forces of the liquid crystal. Then, through chemical foaming treatment, the dense composite film is transformed into a three-dimensional porous aerogel. The prepared three-dimensional porous aerogel has a three-dimensional porous network with smooth and dense pore walls, and the inorganic powder is uniformly distributed within the pore walls.

[0006] One of the technical solutions of the present invention is to provide a method for preparing a composite graphene oxide liquid crystal paste, characterized by comprising the following steps: (1) Prepare a graphene oxide liquid crystal solution; wherein the carbon-oxygen ratio of the graphene oxide is 1.5-2.5 and the sheet size is 10μm-80μm; the concentration of graphene oxide in the graphene oxide liquid crystal solution is 5 mg / mL-20 mg / mL; (2) Add the mineral powder material to the graphene oxide liquid crystal solution and mix evenly to obtain a composite graphene oxide liquid crystal slurry; the particle size of the mineral powder material is 10 nm - 30 μm.

[0007] Furthermore, the ore powder material is selected from at least one of talc powder, mica powder, kaolin powder, bentonite powder, wollastonite powder, barite powder, calcite powder, quartz powder, zeolite powder, feldspar powder, attapulgite powder, sepiolite powder, or vermiculite powder; the mass ratio of the ore powder material to graphene oxide is 1:20-10:1.

[0008] Furthermore, the mixing method in step (2) includes mechanical stirring, ultrasonic dispersion or magnetic stirring, and the mixing time is 20 min - 120 min.

[0009] The second technical solution of this invention is to provide a composite graphene oxide liquid crystal slurry prepared by the above method. The prepared composite graphene oxide liquid crystal slurry exhibits obvious birefringence under a polarizing microscope and has anisotropic liquid crystal characteristics.

[0010] The third technical solution of this invention lies in providing the application of the above-mentioned composite graphene oxide liquid crystal paste. In application, the following steps are generally included: (1) The composite graphene oxide liquid crystal paste is coated into a film and then dried to obtain a graphene oxide / mineral powder composite film. (2) The composite aerogel was obtained by foaming the graphene oxide / mineral powder composite film; (3) Heat treatment of the composite aerogel.

[0011] Furthermore, the coating method is at least one of scraping, dripping, and spin coating.

[0012] Furthermore, the temperature of the heat treatment is 200-1000℃.

[0013] Further, the foaming method involves using a chemical foaming agent; the composite membrane is immersed in a foaming agent solution, allowing the chemical foaming agent to penetrate into the interlayer of graphene oxide, and then the temperature is raised to decompose the chemical foaming agent and generate gas, forming bubbles in the interlayer of graphene oxide. After curing, washing, and drying, a composite aerogel is obtained. The chemical foaming agent is one or more of sodium borohydride, ammonium bicarbonate, ammonium carbonate, azodicarbonamide, citric acid, and sodium bicarbonate. The conditions for the penetration treatment are: temperature 20 ℃-80 ℃, time 1 h-24 h.

[0014] Furthermore, the concentration of the chemical foaming agent is 2 wt%-20 wt%.

[0015] The composite aerogel prepared by the above method has a three-dimensional porous network structure with a pore size of 500 nm - 80 μm and a density of 1 mg / cm³ ~ 300 mg / cm³.

[0016] The advantages of this invention are: This invention solves the long-standing technical problem that "directly adding powder will destroy the GO liquid crystal structure," and prepares a composite slurry with obvious birefringence. The highly ordered liquid crystal structure formed by graphene oxide during the film-forming stage can be completely inherited into the pore wall structure of the aerogel. This invention transforms the ordered stacked structure in the dense film into a three-dimensional porous structure through the foaming process, achieving a unity of order and porosity.

[0017] This invention provides a new, high-value-added utilization method for mineral powder: by combining it with graphene oxide and then foaming it to transform it into a high-performance aerogel material, the application value of mineral powder is significantly enhanced. By selecting different types of mineral powder, aerogels can be endowed with diverse functions. For example, combining it with expanded clay or zeolite mineral powder can give the aerogel adsorption properties, thus enabling its application in fields such as heavy metal adsorption and water treatment. Attached Figure Description

[0018] Figure 1 The images shown are polarized photographs of Example 1, where (a) is a pure graphene oxide liquid crystal solution and (b) is a composite slurry after the addition of mineral powder. Both exhibit bright birefringence, indicating that the liquid crystal phase has not been destroyed.

[0019] Figure 2 The image shows a scanning electron microscope (SEM) image of the composite aerogel, revealing a three-dimensional porous network structure with mineral powder uniformly distributed on the pore wall surface.

[0020] Figure 3 To illustrate the polarization phenomenon of the composite paste in Comparative Example 1, the birefringence phenomenon is weakened, and the liquid crystal structure is partially damaged. Detailed Implementation

[0021] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0022] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0023] The embodiments of the present invention will be further described below with reference to several examples.

[0024] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0026] Example 1 Graphene oxide with a C / O ratio of 2.0 and a sheet size of 20 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 15 mg / mL. 0.3 g of talc powder with a particle size of 500 nm (mass ratio of talc powder to graphene oxide 1:5) was directly added under stirring conditions, and the mixture was mechanically stirred for 30 min to obtain a composite slurry. The composite slurry was coated onto a PET substrate using a blade coating method and dried at 50 °C for 24 h to obtain a graphene oxide / talc composite film. The composite film was immersed in a 5 wt% ammonium bicarbonate aqueous solution at 40 °C for 4 h. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 300 °C in air for 1 h to obtain a graphene oxide / talc composite aerogel.

[0027] like Figure 1 Polarizing microscopy revealed that the composite slurry still exhibited significant birefringence, indicating that the liquid crystal structure of graphene oxide remained intact. The resulting composite aerogel had a density of 12 mg / cm³. SEM analysis showed that the aerogel possessed a three-dimensional porous network with an average pore size of 35 μm. The graphene oxide sheets displayed an ordered, layered stacked structure with smooth, dense pore walls and talc powder uniformly distributed within the pore walls.

[0028] Example 2 Graphene oxide with a C / O ratio of 2.0 and a sheet size of 30 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 5 mg / mL. 4.5 g of kaolin powder with a particle size of 200 nm (kaolin to graphene oxide mass ratio of 9:1) was directly added under stirring. The mixture was ultrasonically dispersed for 20 min to obtain a composite slurry. A film was formed by spin coating and vacuum dried at 40 °C for 24 h to obtain a graphene oxide / kaolin composite film. The composite film was immersed in a 2 wt% sodium borohydride aqueous solution at 30 °C for 2 h to allow sodium borohydride to penetrate into the GO interlayer. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 200 °C in air for 1 h to obtain a graphene oxide / kaolin composite aerogel.

[0029] Polarizing microscopy revealed that the composite slurry still exhibited significant birefringence, indicating that the liquid crystal structure of graphene oxide remained intact. The resulting composite aerogel had a density of 220 mg / cm³ and an average pore size of 8 μm. SEM analysis showed that the aerogel possessed a three-dimensional porous network with smooth and dense pore walls, and kaolin powder was uniformly distributed within the pore walls.

[0030] Example 3 Graphene oxide with a C / O ratio of 1.5 and a sheet size of 40 μm was dispersed in deionized water to prepare 100 mL of a 20 mg / mL graphene oxide liquid crystal solution. 2 g of mica powder with a particle size of 20 μm (mica powder to graphene oxide mass ratio of 1:1) was directly added under stirring. The mixture was mechanically stirred for 45 min to obtain a composite slurry. The composite slurry was coated onto a PET substrate using a blade coating method and dried at 25 °C for 48 h to obtain a graphene oxide / mica composite film. The composite film was immersed in a 5 wt% ammonium bicarbonate aqueous solution at 40 °C for 4 h to allow ammonium bicarbonate to penetrate into the GO interlayer. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 1000 °C for 2 h in an inert atmosphere to obtain a graphene / mica composite aerogel.

[0031] Polarizing microscopy revealed that the composite slurry still exhibited significant birefringence, indicating that the liquid crystal structure of graphene oxide remained intact. The resulting composite aerogel had a density of 55 mg / cm³ and an average pore size of 15 μm. SEM analysis showed that the aerogel possessed a three-dimensional porous network with smooth and dense pore walls, and mica powder was uniformly distributed within the pore walls.

[0032] Example 4 Graphene oxide with a C / O ratio of 2.1 and a sheet size of 10 μm was dispersed in deionized water to prepare 100 mL of a 10 mg / mL graphene oxide liquid crystal solution. 2 g of zeolite powder with a particle size of 50 nm (the mass ratio of zeolite to graphene oxide was 2:1) was directly added under stirring. The mixture was ultrasonically dispersed for 20 min to obtain a composite slurry. The composite slurry was drop-coated onto a smooth PTFE substrate and dried at 40 °C for 12 h to obtain a graphene oxide / zeolite composite film. The composite film was immersed in a 5 wt% ammonium carbonate aqueous solution at 60 °C for 1 h to allow ammonium carbonate to penetrate into the GO interlayer. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 1000 °C for 2 h in an inert atmosphere to obtain a graphene / zeolite composite aerogel.

[0033] Polarizing microscopy revealed that the composite slurry still exhibited significant birefringence, indicating that the liquid crystal structure of graphene oxide remained intact. The resulting composite aerogel had a density of 68 mg / cm³ and an average pore size of 18 μm. SEM analysis showed that the aerogel possessed a three-dimensional porous network with smooth and dense pore walls, and zeolite powder was uniformly distributed within the pore walls.

[0034] Example 5 Graphene oxide with a C / O ratio of 2.5 and a sheet size of 80 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 10 mg / mL. 0.05 g of zeolite powder with a particle size of 50 nm (the mass ratio of zeolite to graphene oxide was 1:20) was added directly under stirring. The mixture was ultrasonically dispersed for 20 min to obtain a composite slurry. The composite slurry was drop-coated onto a smooth PTFE substrate and dried at 40 °C for 12 h to obtain a graphene oxide / zeolite composite film. The composite film was immersed in a 5 wt% ammonium carbonate aqueous solution at 60 °C for 1 h to allow ammonium carbonate to penetrate into the GO interlayer. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 1000 °C for 2 h in an inert atmosphere to obtain a graphene / zeolite composite aerogel.

[0035] The resulting composite aerogel graphene oxide sheets exhibit an ordered, layered stacked structure with smooth and dense pore walls, and zeolite powder is uniformly distributed within the pore walls.

[0036] Comparative Example 1 Graphene oxide with a C / O ratio of 3.0 and a sheet size of 20 μm was used to prepare a composite film and foam it under the same conditions as in Example 1. The specific steps are as follows: Graphene oxide with a C / O ratio of 3.0 and a sheet size of 20 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 15 mg / mL. 0.3 g of talc powder with a particle size of 500 nm (the mass ratio of talc powder to graphene oxide was 1:5) was directly added under stirring conditions, and the mixture was mechanically stirred for 30 min to obtain a composite slurry. The composite slurry was coated onto a PET substrate using a blade coating method and dried at 50 °C for 24 h to obtain a graphene oxide / talc composite film. The composite film was immersed in a 5 wt% ammonium bicarbonate aqueous solution at 40 °C for 4 h. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 300 °C in air for 1 h to obtain a graphene oxide / talc composite aerogel.

[0037] Polarizing microscopy of the composite slurry revealed a significant reduction in birefringence and partial damage to the liquid crystal structure. The film showed obvious cracking after drying, and the aerogel structure after foaming was loose, with thin and discontinuous pore walls. This indicates that even with large sheet sizes, insufficient oxidation results in weak electrostatic repulsion between GO sheets, which cannot resist interference from inorganic powders, leading to the destruction of the liquid crystal structure.

[0038] Comparative Example 2 Graphene oxide with a C / O ratio of 2.0 and a sheet size of 5 μm was used to prepare a composite film and foam it under the same conditions as in Example 1. The specific steps are as follows: Graphene oxide with a C / O ratio of 2.0 and a sheet size of 5 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 15 mg / mL. 0.3 g of talc powder with a particle size of 500 nm (the mass ratio of talc powder to graphene oxide was 1:5) was directly added under stirring conditions, and the mixture was mechanically stirred for 30 min to obtain a composite slurry. The composite slurry was coated onto a PET substrate using a blade coating method and dried at 50 °C for 24 h to obtain a graphene oxide / talc composite film. The composite film was immersed in a 5 wt% ammonium bicarbonate aqueous solution at 40 °C for 4 h. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 300 °C for 1 h in air to obtain a graphene oxide / talc composite aerogel.

[0039] Polarizing microscopy of the composite slurry revealed a significantly reduced birefringence and poor liquid crystal order. The composite film powder was prominently displayed, and the foamed aerogel structure was loose with thin and discontinuous pore walls. This indicates that even if the oxidation degree and other requirements are met, if the sheet size is too small, the steric hindrance effect of the GO sheets is weak, resulting in poor long-range order and an inability to maintain the liquid crystal structure, leading to a significant decrease in aerogel performance.

[0040] Comparative Example 3 Using the same graphene oxide liquid crystal solution as in Example 2, 4.5 g of kaolin powder with a particle size of 300 μm was directly added, with all other conditions remaining the same. The specific steps are as follows: Graphene oxide with a C / O ratio of 2.0 and a sheet size of 30 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 5 mg / mL. Under stirring, 4.5 g of kaolin powder with a particle size of 300 μm (the mass ratio of kaolin to graphene oxide was 9:1) was directly added. The mixture was ultrasonically dispersed for 20 min to obtain a composite slurry. A film was formed using spin coating and vacuum dried at 40 °C for 24 h to obtain a graphene oxide / kaolin composite film. The composite film was immersed in a 2 wt% sodium borohydride aqueous solution at 30 °C for 2 h to allow sodium borohydride to penetrate into the GO interlayer. After removal, the material was vacuum dried at 60°C for 24 hours, followed by heat treatment at 300°C in air for 1 hour to obtain graphene oxide / kaolin composite aerogel.

[0041] In the composite slurry, the kaolin powder settles significantly, making it difficult to form a uniform dispersion. After film formation, the composite membrane surface is rough, the kaolin powder is unevenly distributed, the membrane structure is loose, and the mechanical properties are poor.

[0042] Comparative Example 4 Graphene oxide with a C / O ratio of 1.5 and a sheet size of 40 μm was dispersed in deionized water to prepare 100 mL of a graphene oxide liquid crystal solution with a concentration of 20 mg / mL.

[0043] 30 g of mica powder with a particle size of 20 μm (mica powder to graphene oxide mass ratio of 15:1) was directly added under stirring conditions. The mixture was mechanically stirred for 45 min to obtain a composite slurry. The composite slurry was coated onto a PET substrate using a blade coating method and dried at 25 °C for 48 h to obtain a graphene oxide / mica composite film. The composite film was immersed in a 5 wt% ammonium bicarbonate aqueous solution at 40 °C for 4 h to allow ammonium bicarbonate to penetrate into the GO interlayer. After removal, it was vacuum dried at 60 °C for 24 h, followed by heat treatment at 1000 °C for 2 h in an inert atmosphere to obtain a graphene / mica composite aerogel.

[0044] Polarizing microscopy revealed the disappearance of birefringence in the composite slurry, indicating the disruption of the liquid crystal structure of graphene oxide. The resulting composite film was brittle, prone to cracking, and exhibited significantly reduced mechanical properties.

[0045] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A method for preparing a composite graphene oxide liquid crystal paste, characterized in that, It includes the following steps: (1) Prepare a graphene oxide liquid crystal solution; wherein the carbon-oxygen ratio of the graphene oxide is 1.5-2.5 and the sheet size is 10μm-80μm; the concentration of graphene oxide in the graphene oxide liquid crystal solution is 5 mg / mL-20 mg / mL; (2) Add the mineral powder material to the graphene oxide liquid crystal solution and mix evenly to obtain a composite graphene oxide liquid crystal slurry; the particle size of the mineral powder material is 10 nm - 30 μm.

2. The method according to claim 1, characterized in that, The ore powder material is selected from at least one of talc powder, mica powder, kaolin powder, bentonite powder, wollastonite powder, barite powder, calcite powder, quartz powder, zeolite powder, feldspar powder, attapulgite powder, sepiolite powder, or vermiculite powder; the mass ratio of the ore powder material to graphene oxide is 1:20-10:

1.

3. The method according to claim 1, characterized in that, Step (2) The mixing method includes mechanical stirring, ultrasonic dispersion or magnetic stirring, and the mixing time is 20 min - 120 min.

4. A composite graphene oxide liquid crystal paste prepared by the method as described in claim 1.

5. An application of the composite graphene oxide liquid crystal paste as described in claim 4.

6. The application according to claim 5, characterized in that, It includes the following steps: (1) The composite graphene oxide liquid crystal paste is coated into a film and then dried to obtain a graphene oxide / mineral powder composite film. (2) The composite aerogel was obtained by foaming the graphene oxide / mineral powder composite film; (3) Heat treatment of the composite aerogel.

7. The application according to claim 6, characterized in that, The coating method is at least one of scraping, dripping, and spin coating.

8. The application according to claim 6, characterized in that, The heat treatment temperature is 200-1000℃.

9. The application according to claim 6, characterized in that, The foaming method is to use a chemical foaming agent; the chemical foaming agent is one or more of sodium borohydride, ammonium bicarbonate, ammonium carbonate, azodicarbonamide, citric acid, and sodium bicarbonate.

10. The application according to claim 9, characterized in that, The concentration of the chemical foaming agent is 2 wt%-20 wt%.

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