An expanded graphite coated with a surface load of manganese dioxide and a method for its preparation

Abstract

The application discloses expanded graphite coated with a surface manganese dioxide coating and a preparation method thereof, and belongs to the technical field of magnetic materials. The expanded graphite is immersed in a blended solution of glycerol and ethanol, and is fully stirred under ultrasonic waves. Subsequently, vacuum impregnation, filtration, drying, cleaning, re-drying, and powder 1 are sequentially performed. Then, the powder 1 is immersed in a potassium permanganate aqueous solution, deionized water is added, and after being fully stirred, suction filtration is performed. The filter residue is collected after repeated cleaning, and is dried and calcined to obtain manganese dioxide modified expanded graphite. The modified expanded graphite prepared by the application has the advantages of simple process, small pollution, and the like. The application is an effective method for preparing a manganese dioxide coating on the surface of expanded graphite. The prepared manganese dioxide coating can be used as a seed layer for the growth of other oxides, and can be used for adjusting the impedance matching of the expanded graphite and enhancing the interface polarization loss, thereby laying a foundation for further improving the electromagnetic wave absorption performance of the expanded graphite, and having a wide application prospect in the field of electromagnetic protection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and particularly relates to expanded graphite with a surface-loaded manganese dioxide coating and a preparation method thereof. BACKGROUND

[0002] Expanded graphite is a kind of material with strong pressure resistance, plasticity and self-lubricity, good environmental adaptability, excellent high-temperature resistance, low-temperature resistance, corrosion resistance, radiation resistance and excellent shock resistance. In addition, the loose three-dimensional porous structure of expanded graphite endows it with a unique surface structure, making it suitable for many fields, including the electromagnetic wave absorption field. However, similar to other carbonaceous wave-absorbing materials, the high electrical conductivity and large dielectric constant of expanded graphite often affect its impedance matching characteristics, limiting its development in the wave-absorbing field. In order to solve this problem, incorporating a magnetic component into the expanded graphite matrix and constructing multiple heterogeneous interfaces is a relatively effective means.

[0003] Manganese dioxide is a common transition metal oxide, which is widely used in various fields due to its low cost and non-toxicity. At the same time, the variable crystal structure and good dielectric properties of manganese dioxide make it have great potential in the wave-absorbing field. Currently, the research on manganese dioxide / expanded graphite composite materials mainly focuses on using potassium permanganate as the manganese source and using hydrothermal / solvothermal method to grow manganese dioxide nanomaterials with flower-like or rod-like morphology on the surface of expanded graphite, so as to realize the improvement of wave-absorbing performance. However, due to the limitation of experimental conditions, it is difficult to realize the uniform and dense growth of manganese dioxide on the surface of expanded graphite material, and it also does not meet the needs of large-scale production.

[0004] In view of the technical problems that the existing methods for growing manganese dioxide on the surface of expanded graphite cannot uniformly and densely grow manganese dioxide on the surface of expanded graphite material, and cannot meet the needs of large-scale production, therefore, it is urgent to find a simple, low-cost and easy-to-industrialize method to prepare a manganese dioxide coating on the surface of expanded graphite through a simple and efficient preparation process, which has very important research and application value. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide expanded graphite with a surface-loaded manganese dioxide coating and a preparation method thereof, so as to solve the technical problems that the existing methods for growing manganese dioxide on the surface of expanded graphite cannot uniformly and densely grow manganese dioxide on the surface of expanded graphite material, and cannot meet the needs of large-scale production.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The application discloses a preparation method of expanded graphite with a surface loaded manganese dioxide coating.

[0008] The expanded graphite is immersed into a blended solution of glycerol and ethanol, and is fully stirred under ultrasonic waves, and then vacuum impregnation, filtration, drying, cleaning, and re-drying are sequentially performed to obtain powder 1; then the powder 1 is immersed into a potassium permanganate aqueous solution, deionized water is added, and after fully stirring, suction filtration is performed, multiple repeated cleaning is performed, filter residues are collected, and after drying and calcination, the modified expanded graphite with manganese dioxide is obtained.

[0009] Preferably, the expanded graphite: organic solvent is used in a ratio of (0.5-1) g:(30-70) mL.

[0010] Preferably, the calcination temperature is 300-500 DEG C, and the calcination time is 0.5-3 h.

[0011] Preferably, in the blended solution of glycerol and ethanol, the volume percentage concentration of glycerol is greater than or equal to 60%.

[0012] Preferably, the concentration of the potassium permanganate aqueous solution is 0.0025-0.1 mol / L; 5-50 mL of the potassium permanganate aqueous solution is added to 0.1 g of the expanded graphite, and 200-500 mL of deionized water is added.

[0013] Preferably, the vacuum impregnation time is 3-12 h.

[0014] Preferably, the drying condition is 60-80 DEG C for 1-3 h.

[0015] Preferably, the cleaning solution is acetone or diethyl ether; 100-600 mL of the acetone or diethyl ether is used for cleaning 0.1 g of the expanded graphite.

[0016] Preferably, when the powder 1 is immersed into the potassium permanganate aqueous solution, the powder 1 is placed in an impregnation spoon with 500-2000 mesh holes, and the impregnation spoon is immersed into the potassium permanganate aqueous solution for 1-10 min.

[0017] The application further discloses the expanded graphite with the surface loaded manganese dioxide coating prepared by the preparation method.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The application discloses a preparation method of expanded graphite with a surface-loaded manganese dioxide coating, and the manganese dioxide coating can be well combined with the expanded graphite, the interface polarization effect between the coating and the graphite matrix is enhanced, and the wave absorbing performance is improved. The difference in solubility of glycerol in different solvents is utilized to remove excess adsorbed glycerol, and then the manganese dioxide coating is prepared on the surface of the expanded graphite. Meanwhile, the dense manganese dioxide coating can also be used as a seed layer for growth of other oxides, and provides a possibility for further modification of the composite material. The manganese dioxide coating is prepared by utilizing the adsorption characteristics of the expanded graphite, and has the characteristics of simple method, small pollution and industrial application. Compared with the traditional manganese dioxide modified expanded graphite, the method has the advantages of simple process, small environmental pollution, low requirement on equipment and suitability for large-scale application. The prepared manganese dioxide coating can be used for adjusting the impedance matching of the expanded graphite, enhancing the interface polarization loss, and also can be used as a seed layer for growth of other oxides, and lays a foundation for further improving the electromagnetic wave absorbing performance of the expanded graphite.

[0020] Further, by accurately controlling the proportion of raw materials, controlling the concentration of the reaction solution, regulating the content of the adsorbed organic solvent of the expanded graphite, and optimizing the process parameters, the thickness of the manganese dioxide coating can be effectively controlled.

[0021] Further, the volume percentage concentration of glycerol in the blended solution of glycerol and ethanol is greater than 60%, which can promote the reaction to proceed fully.

[0022] Further, the concentration of the potassium permanganate aqueous solution is 0.0025-0.1 mol / L; 5-50 mL of the potassium permanganate aqueous solution is added to every 0.1 g of the expanded graphite, and 200-500 mL of deionized water is added; and thus the thickness, continuity and integrity of the manganese dioxide coating can be effectively controlled.

[0023] Further, the solution used for cleaning is acetone or diethyl ether; 100-600 mL of acetone or diethyl ether is used to clean every 0.1 g of the expanded graphite; and the unreacted raw materials are removed fully.

[0024] Further, when the powder 1 is immersed in the potassium permanganate aqueous solution, the powder 1 is placed in an impregnation spoon with 500-2000 mesh holes, and the impregnation spoon is immersed in the potassium permanganate aqueous solution for 1-10 min; and the powder 1 is fully reacted with the potassium permanganate.

[0025] The application further discloses the expanded graphite with the surface-loaded manganese dioxide coating prepared by the preparation method, the expanded graphite with the surface-loaded manganese dioxide coating has more surface chemical active sites, the impedance matching characteristics of the material are improved significantly, the active layer can be provided for further regulating the physical and chemical properties of the expanded graphite, the synthesis process is simple, and the batch preparation is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 This is a SEM image of the expanded graphite with a surface-loaded manganese dioxide coating obtained in Example 1 of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] This invention discloses a method for preparing expanded graphite with a surface-loaded manganese dioxide coating, comprising the following steps:

[0031] Step 1: Immerse expanded graphite in solution 1, stir solution 1 thoroughly under ultrasonic conditions, then transfer it to a vacuum oven for vacuum impregnation for 3-12 hours. After completion, filter it and dry the black filter residue in the oven at 60-80℃ for 1-3 hours. Then wash it with solution 2, and dry it to obtain powder 1.

[0032] Step 2: Prepare a potassium permanganate aqueous solution and stir it thoroughly to form a homogeneous solution 3. Then weigh out powder 1 and place it in an impregnation spoon. Immerse the impregnation spoon in solution 3 for 1-10 minutes to obtain a brownish-black slurry.

[0033] Step 3: Add 200-500mL of deionized water to the brownish-black slurry, stir thoroughly, and then filter. After repeated washing until the filter paper turns from brownish-black to white, collect the filter residue, dry it, and obtain powder 2. Place powder 2 in an atmosphere furnace and calcine it at 300-500℃ for 0.5-3h. After the furnace temperature cools naturally, manganese dioxide modified expanded graphite is obtained.

[0034] In step one, solution 1 is a mixture of glycerol and ethanol, wherein the volume percentage concentration of glycerol is greater than or equal to 60%.

[0035] Solution 2 is acetone or diethyl ether.

[0036] The ratio of expanded graphite to solution 1 is (0.5-1)g:(30-70)mL.

[0037] The volume of solution 2 used is 100-600 mL.

[0038] In step two, the concentration of potassium permanganate aqueous solution is 0.0025-0.1 mol / L, and 5-50 mL of potassium permanganate aqueous solution is added for every 0.1 g of expanded graphite.

[0039] The dipping spoon has 500-2000 mesh holes.

[0040] Example 1

[0041] A method for preparing expanded graphite with a surface-loaded manganese dioxide coating includes the following steps:

[0042] 0.5 g of expanded graphite was immersed in a 30 mL mixture of glycerol and ethanol, where the glycerol volume percentage was 60%. After thorough stirring, the mixture was transferred to a vacuum oven for vacuum impregnation for 3 hours. The mixture was then filtered, and the black filter residue was dried in the oven at 60°C for 1 hour. The residue was then washed with 100 mL of diethyl ether and dried to obtain the treated expanded graphite. A 25 mL solution of 0.0025 mol / L potassium permanganate was prepared and thoroughly stirred to form a homogeneous solution. The treated expanded graphite was then weighed and placed in an impregnation spoon with 500 mesh openings. The spoon was immersed in the potassium permanganate solution for 10 minutes to obtain a brownish-black slurry. 200 mL of deionized water was added to the brownish-black slurry, and after thorough stirring, the mixture was filtered to obtain brownish-black filter paper. The brownish-black filter paper was then rinsed again with 200 mL of deionized water, and the rinsing liquid was collected and filtered. This process was repeated until the filtered filter paper showed a white base color. At this point, the filter residue is collected, dried, and powder 2 is obtained. Powder 2 is placed in an atmosphere furnace and calcined at 300°C for 3 hours. After the furnace temperature is naturally cooled, expanded graphite with a manganese dioxide coating on its surface is obtained.

[0043] See Figure 1This is a SEM image of the expanded graphite with a surface-loaded manganese dioxide coating prepared in Example 1 of the present invention; as can be seen from the image, surface morphology analysis (SEM) tests were performed on it (see...). Figure 1 It can be observed that the expanded graphite surface has a relatively uniformly distributed manganese dioxide coating.

[0044] Example 2

[0045] A method for preparing expanded graphite with a surface-loaded manganese dioxide coating includes the following steps:

[0046] 1g of expanded graphite was immersed in a 70mL mixture of glycerol and ethanol, where the glycerol volume percentage was 80%. After thorough stirring, the mixture was transferred to a vacuum oven for 12 hours of vacuum impregnation. The resulting solution was then filtered, and the black filter residue was dried in the oven at 80℃ for 3 hours. The residue was then washed with 350mL of diethyl ether and dried to obtain the treated expanded graphite. A 500mL solution of 0.01mol / L potassium permanganate was prepared and thoroughly stirred to form a homogeneous solution. The treated expanded graphite was then weighed and placed in an impregnation spoon with 2000 mesh openings. The spoon was immersed in the potassium permanganate solution for 5 minutes to obtain a brownish-black slurry. 300mL of deionized water was added to the brownish-black slurry, and after thorough stirring, the mixture was filtered to obtain brownish-black filter paper. The filter paper was then rinsed again with 300mL of deionized water, and the rinsing liquid was collected and filtered. This process was repeated until the filtered filter paper had a white base color. At this point, the filter residue is collected, dried, and powder 2 is obtained. Powder 2 is placed in an atmosphere furnace and calcined at 500°C for 0.5 hours. After the furnace temperature is naturally cooled, expanded graphite with a manganese dioxide coating on its surface is obtained.

[0047] Example 3

[0048] A method for preparing expanded graphite with a surface-loaded manganese dioxide coating includes the following steps:

[0049] 0.7 g of expanded graphite was immersed in 50 mL of glycerol solution (60% by volume). After thorough stirring, the solution was transferred to a vacuum oven for 12 h of vacuum impregnation. The mixture was then filtered, and the black filter residue was dried in the oven at 60 °C for 3 h. The residue was then washed with 600 mL of ether and dried to obtain the treated expanded graphite. A 70 mL solution of 0.1 mol / L potassium permanganate was prepared and stirred thoroughly to form a homogeneous solution. The treated expanded graphite was then weighed and placed in an impregnation spoon with 1500 mesh openings. The spoon was immersed in the potassium permanganate solution for 1 min to obtain a brownish-black slurry. 500 mL of deionized water was added to the brownish-black slurry, and the mixture was stirred thoroughly and then filtered to obtain brownish-black filter paper. The filter paper was then rinsed again with 500 mL of deionized water, and the rinsing liquid was collected and filtered. This process was repeated until the filtered filter paper had a white base color. At this point, the filter residue is collected, dried, and powder 2 is obtained. Powder 2 is placed in an atmosphere furnace and calcined at 400°C for 2 hours. After the furnace temperature is naturally cooled, expanded graphite with a manganese dioxide coating on its surface is obtained.

[0050] Example 4

[0051] A method for preparing expanded graphite with a surface-loaded manganese dioxide coating includes the following steps:

[0052] 0.8 g of expanded graphite was immersed in a 55 mL mixture of glycerol and ethanol (glycerol volume percentage 70%). After thorough stirring, the mixture was transferred to a vacuum oven for 5 h of vacuum impregnation. The resulting solution was then filtered, and the black filter residue was dried in the oven at 70 °C for 1.5 h. The residue was then washed with 200 mL of acetone and dried to obtain the treated expanded graphite. A 160 mL solution of 0.05 mol / L potassium permanganate was prepared and thoroughly stirred to form a homogeneous solution. A portion of the treated expanded graphite was weighed and placed in an impregnation spoon with 500 mesh openings. The spoon was then immersed in the potassium permanganate solution for 6 min to obtain a brownish-black slurry. 350 mL of deionized water was added to the brownish-black slurry, and the mixture was thoroughly stirred and then filtered to obtain brownish-black filter paper. The filter paper was then rinsed again with 350 mL of deionized water, and the rinsing liquid was collected and filtered. This process was repeated until the filtered filter paper had a white base color. At this point, the filter residue is collected, dried, and powder 2 is obtained. Powder 2 is placed in an atmosphere furnace and calcined at 450°C for 1 hour. After the furnace temperature is naturally cooled, expanded graphite with a manganese dioxide coating on its surface is obtained.

[0053] Example 5

[0054] A method for preparing expanded graphite with a surface-loaded manganese dioxide coating includes the following steps:

[0055] 0.6 g of expanded graphite was immersed in a 60 mL mixture of glycerol and ethanol, where the glycerol volume percentage was 90%. After thorough stirring, the mixture was transferred to a vacuum oven for vacuum impregnation for 10 h. The mixture was then filtered, and the black filter residue was dried in the oven at 60 °C for 2.5 h. The residue was then washed with 500 mL of acetone and dried to obtain the treated expanded graphite. A 180 mL solution of 0.005 mol / L potassium permanganate was prepared and thoroughly stirred to form a homogeneous solution. The treated expanded graphite was then weighed and placed in an impregnation spoon with 2000 mesh openings. The spoon was immersed in the potassium permanganate solution for 8 min to obtain a brownish-black slurry. 400 mL of deionized water was added to the brownish-black slurry, and after thorough stirring, the mixture was filtered to obtain brownish-black filter paper. The brownish-black filter paper was then rinsed again with 400 mL of deionized water, and the rinsing liquid was collected and filtered. This process was repeated until the filtered filter paper had a white base color. At this point, the filter residue is collected, dried, and powder 2 is obtained. Powder 2 is placed in an atmosphere furnace and calcined at 500°C for 0.5 hours. After the furnace temperature is naturally cooled, expanded graphite with a manganese dioxide coating on its surface is obtained.

[0056] This invention utilizes the adsorption properties of expanded graphite to control the glycerol adsorption content by adjusting the concentration of the reaction solution. Optimized process parameters allow for effective control of the manganese dioxide coating thickness. By leveraging the difference in glycerol solubility in different solvents, excess adsorbed glycerol is removed, thus achieving the preparation of a manganese dioxide coating on the surface of expanded graphite. Compared with traditional manganese dioxide-modified expanded graphite, this invention offers advantages such as simpler process, less environmental pollution, lower equipment requirements, and suitability for large-scale applications. The prepared manganese dioxide coating not only adjusts the impedance matching of expanded graphite and enhances interfacial polarization loss, but can also serve as a seed layer for the growth of other oxides, laying the foundation for further improving the electromagnetic wave absorption performance of expanded graphite.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing expanded graphite with a surface-loaded manganese dioxide coating, characterized in that, include: Expanded graphite was immersed in a mixed solution of glycerol and ethanol, stirred thoroughly under ultrasound, and then vacuum impregnated, filtered, dried, washed, and dried again to obtain powder 1. Powder 1 was then immersed in potassium permanganate aqueous solution, deionized water was added, stirred thoroughly, filtered, washed repeatedly, the filter residue was collected, dried, and calcined to obtain manganese dioxide modified expanded graphite. In the blended solution of glycerol and ethanol, the volume percentage concentration of glycerol is greater than or equal to 60%. The concentration of the potassium permanganate aqueous solution is 0.0025-0.1 mol / L; for every 0.1 g of expanded graphite, add 5-50 mL of potassium permanganate aqueous solution and 200-500 mL of deionized water; The cleaning solution used is acetone or ether; 100-600 mL of acetone or ether is used to clean each 0.1 g of expanded graphite. When immersing powder 1 into a potassium permanganate aqueous solution, powder 1 is placed in an immersion spoon with 500-2000 mesh holes, and the immersion spoon is immersed in the potassium permanganate aqueous solution for 1-10 minutes.

2. The method for preparing expanded graphite with a surface-loaded manganese dioxide coating according to claim 1, characterized in that, The ratio of expanded graphite to organic solvent is (0.5-1) g: (30-70) mL.

3. The method for preparing expanded graphite with a surface-loaded manganese dioxide coating according to claim 1, characterized in that, The calcination temperature is 300-500℃, and the calcination time is 0.5-3h.

4. The method for preparing expanded graphite with a surface-loaded manganese dioxide coating according to claim 1, characterized in that, The vacuum impregnation time is 3-12 hours.

5. The method for preparing expanded graphite with a surface-loaded manganese dioxide coating according to claim 1, characterized in that, The drying conditions are 60~80℃ for 1-3 hours.

6. Expanded graphite with a surface-loaded manganese dioxide coating prepared by the preparation method according to any one of claims 1-5.

Images