Preparation method of low-cost graphene oxide for high-performance heat-conducting film
By using low-concentration sulfuric acid intercalation and a medium-temperature reaction system, combined with low-cost graphite raw materials, the problem of high cost in the Hummers method for preparing graphene oxide has been solved. This has enabled low-cost and safe preparation of graphene oxide and high thermal conductivity of graphene thermal conductive films, making them suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-04-03
AI Technical Summary
The existing Hummers method for preparing graphene oxide is costly, hazardous, and difficult to treat waste liquid, resulting in high production costs for graphene thermal conductive films.
By employing a low-concentration sulfuric acid intercalation and medium-temperature reaction system, combined with low- and medium-temperature reactions, and using low-cost graphite raw materials such as graphite waste, the consumption of sulfuric acid and oxidant is reduced, thereby lowering the output of waste liquid by controlling reaction conditions and the amount of oxidant.
The preparation of graphene oxide with low cost and high safety has been achieved, which reduces production costs and waste liquid output. The thermal conductivity of the graphene thermal conductive film is less affected by the graphite raw material, making it suitable for large-scale production.
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Figure CN121778720A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of graphene technology, and more specifically to a method for preparing low-cost graphene oxide for high-performance thermal conductive films. Background Technology
[0002] With the miniaturization and increasing power density of electronic products, heat dissipation performance has become a key factor restricting the further development of electronic products. Graphene thermal conductive film, with its extremely high in-plane thermal conductivity, is regarded as the ideal next-generation heat dissipation material.
[0003] Graphene oxide is a key precursor for preparing graphene thermal conductive films. Currently, the industrial production of graphene oxide mainly employs the Hummers method and its modifications. However, the Hummers method and its modifications suffer from drawbacks such as high raw material costs, hazardous processes (violent reactions), and difficulties in wastewater treatment, which increase the overall cost of producing graphene thermal conductive films. Some manufacturers reduce energy consumption and recycling costs by collecting and distilling the waste acid generated during the graphene oxide preparation process in stages through distillation concentration and crystallization.
[0004] There is still a need to develop new Hummers improvement methods to reduce the raw material costs of graphene oxide production, improve production safety, and reduce waste liquid output. Summary of the Invention
[0005] The purpose of this invention is to overcome the defects in the prior art and provide a method for preparing low-cost graphene oxide for high-performance thermal conductive films with low production costs.
[0006] To address the aforementioned technical problems, this invention provides a method for preparing low-cost graphene oxide for high-performance thermally conductive films, comprising the following steps: S1: After mixing graphite raw materials and acid solution at a temperature below 5°C, the reaction system temperature is controlled at a temperature below 10°C. After adding oxidant, the reaction is carried out for 0.5~1.5 hours, and the solid and liquid are separated to obtain filter cake. S2: Add the filter cake to concentrated sulfuric acid, control the reaction system temperature below 15℃, slowly add the oxidant and react for 1.5~2.5h, then raise the temperature to 30~45℃ and react for 0.5~2h to obtain the reaction solution; S3: Dilute the reaction solution and terminate the reaction to obtain a graphene oxide dispersion; S4: The graphene oxide dispersion is separated into solid and liquid phases to obtain a solid, which is low-cost graphene oxide used in the production of high-performance thermal conductive films.
[0007] The acid solution includes sulfuric acid, and the concentration of sulfuric acid in the acid solution is 30% to 65%.
[0008] Furthermore, the reaction time after adding the oxidant to S1 can be selected as 0.5, 0.8, 1, 1.2, 1.5 h points or the above two points as the range of maximum and minimum values; After slowly adding the oxidant to S2, the reaction time can be selected from points of 1.5, 1.7, 1.9, 2.2, and 2.5 h, or the range between the two points mentioned above as the maximum and minimum values. Then, the temperature to which the temperature is raised can be selected from points of 30, 35, 40, and 45 °C, or the range between the two points mentioned above as the maximum and minimum values. After raising the temperature, the reaction time can be selected from points of 0.5, 1, 1.5, and 2 h, or the range between the two points mentioned above as the maximum and minimum values. The concentration of sulfuric acid in the acid solution can be selected as 30%, 40%, 45%, 50%, 60%, or 65% of the point values, or as a range of the above two point values as the maximum and minimum values.
[0009] A preferred technical solution is that the mass ratio of the graphite raw material to the oxidant in S1 is 1:(0.15~0.4).
[0010] Furthermore, the mass ratio of the graphite raw material to the oxidant in S1 is 1:0.15, 1:0.2, 1:0.3, 1:0.4, or the above two values are used as the range of maximum and minimum values.
[0011] A preferred technical solution is that the mass ratio of the graphite raw material to the oxidant in S2 is 1:(1.4~1.9).
[0012] Furthermore, the mass ratio of the graphite raw material to the oxidant in S2 is 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, or 1:1.9, or two of the above values are used as the range of maximum and minimum values.
[0013] A preferred technical solution is that the average particle size of the graphite raw material is less than 100 μm.
[0014] A preferred technical solution is that the graphite raw material includes at least one of microcrystalline graphite, recycled graphite materials, and graphite waste.
[0015] The preferred technical solution is that the mass ratio of the graphite raw material to the acid solution is 5:(80~189), and the mass ratio of the graphite raw material to concentrated sulfuric acid is 5:(144~225).
[0016] Furthermore, the mass ratio of the graphite raw material to the acid solution is 5:80, 5:100, 5:120, 5:140, 5:160, 5:180, or 5:189, or a range of two of the above values as the maximum and minimum values. The mass ratio of the graphite raw material to concentrated sulfuric acid is 5:144, 5:165, 5:174, 5:187, 5:199, 5:213, or 5:225, or a range of two of the above values as the maximum and minimum values.
[0017] The preferred technical solution is that S3 includes: diluting the reaction solution with pure water below 10°C, controlling the system temperature below 80°C during dilution, keeping the diluted reaction solution at 10°C for 20-40 minutes, and adding hydrogen peroxide solution after the temperature drops below 40°C until the system turns bright yellow, to obtain a graphene oxide dispersion.
[0018] Furthermore, the incubation time of the diluted reaction solution below 10°C can be selected as 20, 25, 30, 35, or 40 min, or as a range of the above two values as the maximum and minimum values.
[0019] The preferred technical solution is that the mass ratio of the graphite raw material to pure water is 1:(20~40).
[0020] Furthermore, the mass ratio of the graphite raw material to pure water is 1:20, 1:25, 1:30, 1:35, or 1:40, or two of the above values are used as the range of maximum and minimum values.
[0021] The preferred technical solution is that the acid solution used in S1 is the recovered acid solution obtained by solid-liquid separation of the graphene oxide dispersion.
[0022] A preferred technical solution is that the concentration of sulfuric acid in the acid solution is 40% to 55%.
[0023] Furthermore, the concentration of sulfuric acid in the acid solution can be selected as a point value of 40%, 45%, 50%, or 55%, or a range of the above two point values as the maximum and minimum values.
[0024] The advantages and beneficial effects of this invention are as follows: The present invention provides a low-cost method for preparing high-performance thermal conductive films using graphene oxide, which is simple, mild, and easy to mass-produce. The preparation method first uses low-concentration sulfuric acid intercalation, then uses concentrated sulfuric acid intercalation, and combines it with a low- and medium-temperature reaction system, which improves the safety of the process, reduces the consumption of sulfuric acid and oxidant, and reduces the amount of waste liquid produced. Furthermore, the thermal conductivity of the thermally conductive film made from graphene oxide prepared using this system is less affected by whether the graphite raw material contains graphite waste.
[0025] Furthermore, using low-cost graphite waste as graphite raw material, the thermal conductivity of the thermally conductive film made from graphene oxide prepared by the system of this invention is superior. Attached Figure Description
[0026] Figure 1 This is an atomic force microscope (AFM) image of the graphene oxide prepared in Example 1. Detailed Implementation
[0027] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.
[0028] raw material: Flake graphite: 200 mesh; Microcrystalline graphite: 200 mesh; Artificial graphite waste: 200 mesh; Spherical graphite processing waste: 200 mesh; 1. Examples and Comparative Examples Example 1
[0029] The preparation process of low-cost graphene oxide for the high-performance thermally conductive film in Example 1 is as follows: S1: 5 kg of flake graphite was introduced into 100 L of 45% sulfuric acid and stirred at 5 °C for 30 min. A cold water bath was used to keep the system temperature below 10 °C and 1 kg of potassium permanganate was slowly added in batches over 45 min. The reaction was continued at 10 °C for 1 h. The mixture was then separated by pressure filtration to obtain the filter cake. S2: Add the filter cake to 100L of 98% concentrated sulfuric acid, use a cold water bath to keep the system temperature below 10℃, slowly add 7.5kg of potassium permanganate in batches over 45min, and continue the reaction for 2h at a temperature below 10℃. S3: Transfer the reaction solution to a constant temperature oil bath at 35°C and react for 1 hour. During this time, the system is stirred mechanically at a speed of 80 rpm. S4: Keep the system temperature below 60℃ and slowly add the reaction solution to 150L of pure water at 5℃ within 30min. Then place the system in a 10℃ ice-water bath and continue stirring for 30min. After the system temperature drops below 40℃, add 2L of 30% hydrogen peroxide solution until the reaction solution turns bright yellow, and terminate the reaction. S5: Pressure filtration separation. The obtained filter cake is dispersed by stirring with dilute sulfuric acid and then filtered by pressure. The filtrate is retained. After 5 dispersion-pressure filtration cycles, the filter cake is washed with pure water until it is neutral.
[0030] Example 2
[0031] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 2 is based on Example 1, except that the graphite raw material used in S1 is microcrystalline graphite.
[0032] Example 3
[0033] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 3 is based on Example 1, except that the graphite raw material used in S1 is artificial graphite waste.
[0034] Example 4
[0035] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 4 is based on Example 1, except that the graphite raw material used in S1 is spherical graphite processing waste.
[0036] Example 5
[0037] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 5 is based on Example 1, except that: S1: 5 kg of flake graphite is introduced into 100 L of the filtrate obtained in S5 of Example, stirred at 5 °C for 30 min, a cold water bath is used to keep the system temperature below 10 °C, and 1 kg of potassium permanganate is slowly added in batches over 45 min, and the reaction continues at below 10 °C for 1 h, followed by pressure filtration to obtain filter cake.
[0038] Example 6
[0039] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 6 is based on Example 1, except that: S1: 5 kg of flake graphite is introduced into 100 L of 45% sulfuric acid, stirred at 5 °C for 30 min, a cold water bath is used to keep the system temperature below 10 °C, and 2.1 kg of potassium permanganate is slowly added in batches over 45 min, and the reaction is continued at below 10 °C for 1 h. The mixture is then separated by pressure filtration to obtain a filter cake.
[0040] Example 7
[0041] The preparation process of low-cost graphene oxide for high-performance thermal conductive film in Example 7 is based on Example 1, except that, in S2: the filter cake is added to 100L of 98% concentrated sulfuric acid, a cold water bath is used to keep the system temperature below 10°C, 10kg of potassium permanganate is slowly added in batches over 45min, and the system continues to react for 2h at a temperature below 10°C.
[0042] Comparative Example S1: Mix 5 kg of flake graphite with 150 L of 98% concentrated sulfuric acid, stir at 5 °C for 30 min, use an ice-water bath to keep the system temperature below 5 °C, and slowly add 18 kg of potassium permanganate in batches over 45 min, and continue to react at 5 °C for 1 h. S2: Transfer the reaction solution to a constant temperature oil bath at 50°C and react for 6 hours. During this time, the system is stirred mechanically at a speed of 80 rpm. S3: Slowly add 250 L of deionized water to the reaction solution, then add 50 L of 30% hydrogen peroxide until the solution turns bright yellow, and terminate the reaction. S4: Pressure filtration separation. The obtained filter cake is dispersed by stirring with dilute sulfuric acid and then pressure filtered. After 5 dispersion-pressure filtration cycles, the filter cake is washed with pure water until it is neutral.
[0043] 2. Detection methods for the examples and comparative samples The process for preparing graphene membranes from the graphene oxide filter cakes of the examples and comparative examples is as follows: S01: The filter cakes obtained in the examples and comparative examples are ground and dispersed in pure water to obtain a graphene oxide dispersion; S02: Ammonia water is slowly introduced into the graphene oxide dispersion until the pH of the graphene oxide dispersion drops to 6. After homogenization three times under 800 bar pressure, defoaming treatment is performed to obtain 1% graphene oxide slurry. S03: Graphene oxide slurry is coated onto a substrate using a coating machine, dried at 120 degrees Celsius, and then subjected to a thermal reduction process at 1200 degrees Celsius and complete graphitization at a high temperature of 2850 degrees Celsius to obtain a 35-micron-thick graphene thermal conductive film.
[0044] 2.1. The morphology of graphene oxide was observed using an atomic force microscope; 2.2. The thermal conductivity of the graphene thermal conductive film was tested using a Netzsch LFA467 thermal diffusivity testing device; 3. Performance test results of the examples and comparative samples
[0045] 4. Analysis of test results from examples and comparative examples Examples 1, 2, 3, 4, and the comparative examples demonstrate that the thermal conductivity of the thermally conductive film made from graphene oxide prepared using the system of the present invention is minimally affected by whether the graphite raw material contains graphite waste. The system of the present invention uses low-cost graphite waste as the graphite raw material, and the thermal conductivity of the thermally conductive film made from graphene oxide prepared using this system is superior, approaching that of the thermally conductive film prepared using the Hummers method with high-purity flake graphite.
[0046] Examples 1 and 5 show that the system of the present invention uses the filtrate, which is originally waste liquid, for intercalation, which reduces the amount of sulfuric acid consumed and the amount of waste liquid produced, and has basically no impact on the thermal conductivity of the thermally conductive film made of graphene oxide prepared by the system.
[0047] Examples 1, 6, and 7 show that, to a certain extent, reducing the use of oxidant has virtually no impact on the thermal conductivity of the thermally conductive film made from graphene oxide prepared using this system.
[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing low-cost graphene oxide for high-performance thermally conductive films, characterized in that, Includes the following steps: S1: After mixing graphite raw materials and acid solution at a temperature below 5°C, the reaction system temperature is controlled at a temperature below 10°C. After adding oxidant, the reaction is carried out for 0.5~1.5 hours, and the solid and liquid are separated to obtain filter cake. S2: Add the filter cake to concentrated sulfuric acid, control the reaction system temperature below 15℃, slowly add the oxidant and react for 1.5~2.5h, then raise the temperature to 30~45℃ and react for 0.5~2h to obtain the reaction solution; S3: Dilute the reaction solution and terminate the reaction to obtain a graphene oxide dispersion; S4: The graphene oxide dispersion is separated into solid and liquid phases to obtain a solid, which is low-cost graphene oxide used in the production of high-performance thermal conductive films. The acid solution includes sulfuric acid, and the concentration of sulfuric acid in the acid solution is 30% to 65%.
2. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, The mass ratio of the graphite raw material to the oxidant in S1 is 1:(0.15~0.4).
3. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, The mass ratio of the graphite raw material to the oxidant in S2 is 1:(1.4~1.9).
4. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, The average particle size of the graphite raw material is less than 100 μm.
5. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 4, characterized in that, The graphite raw materials include at least one of microcrystalline graphite, recycled graphite materials, and graphite waste.
6. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, The mass ratio of the graphite raw material to the acid solution is 5:(80~189), and the mass ratio of the graphite raw material to concentrated sulfuric acid is 5:(144~225).
7. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, S3 includes: The reaction solution was diluted with pure water at a temperature below 10°C. During dilution, the system temperature was controlled to be below 80°C. The diluted reaction solution was kept at a temperature below 10°C for 20-40 minutes. After the temperature dropped to below 40°C, hydrogen peroxide solution was added until the system turned bright yellow, thus obtaining a graphene oxide dispersion.
8. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 7, characterized in that, The mass ratio of the graphite raw material to pure water is 1:(20~40).
9. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 8, characterized in that, The acid solution used in S1 is the recovered acid solution obtained by solid-liquid separation of the graphene oxide dispersion.
10. The method for preparing low-cost graphene oxide for high-performance thermally conductive films according to claim 1, characterized in that, The concentration of sulfuric acid in the acid solution is 40% to 55%.