A method for producing sub-micron and micron-sized graphene oxide from coal and products

Abstract

The application discloses a method for preparing submicron and micron alkylated graphene oxide by using coal, and comprises the following steps: 1, graphitizing coal powder to rearrange carbon atoms and grow submicron crystal regions; 2, oxidizing and peeling the graphitized coal under the action of sulfuric acid, phosphoric acid and potassium permanganate; 3, adding hydrogen peroxide to react with potassium permanganate and high-valence manganese salt in the solution until the solution turns yellow; 4, screening the solution to remove unreacted black impurities; 5, centrifuging the solution to reserve the precipitate, and then washing and centrifuging the precipitate with dilute hydrochloric acid and ethanol; 6, dispersing the precipitate with diethyl ether, and then obtaining graphene oxide powder through suction filtration. The prepared graphene oxide has an average size of 800 nm, an average layer number of 1-2 layers, and a yield of 107%. The method has simple steps, low cost and high yield, and is easy to realize industrial production, and has a very broad prospect in the present situation of urgently realizing high-value utilization of coal.

Description

Technical Field

[0001] This invention relates to the field of carbon nanomaterials technology, specifically to a method and product for preparing submicron and micron-sized graphene oxide using coal. Background Technology

[0002] Since its discovery, graphene has been favored by researchers for its excellent mechanical, thermal, and electrical properties. Graphene oxide, as a derivative of graphene, has great potential in fields such as fibers, thermal conductivity, energy storage, liquid crystal optics, and biomedicine. Its large-scale production capability and hydrophilic properties give it unparalleled advantages. The most famous method for preparing graphene oxide is the Hummers process, a chemical method that uses a mixture of sulfuric acid, sodium nitrate, and potassium permanganate to treat graphite. Over time, many researchers have adjusted the reaction conditions, the amount of potassium permanganate, and the proportions of reactants in the Hummers process, resulting in many improved versions. Besides chemical methods, electrochemical, ultrasonic, microwave, and ball milling methods can also be used to prepare graphene oxide. These methods mostly use high-purity graphite as raw material, so the size of the prepared graphene oxide is mostly in the tens or even hundreds of micrometers. The preparation of large-size graphene oxide has become a research hotspot.

[0003] Typically, submicron and micron-sized graphene oxides, compared to large-size graphene oxides, lack substantial lateral dimensions, which is considered detrimental to the electrical and mechanical properties of composite films and fibers, significantly limiting their applications. However, reports indicate that submicron and micron-sized graphene oxides can be used in the fabrication of nanofiltration membranes for organic solvents. Their higher density of oxygen-containing functional groups allows for the formation of unique, strong coordination bonds with crosslinking agents, enabling size-dependent ultrafast selective molecular transport. Furthermore, in antibacterial applications, larger graphene oxide sheets primarily adsorb and encapsulate cells, isolating them from the environment, while submicron and micron-sized graphene oxides, with their higher defect density-related oxidation mechanisms, can directly act on cell membranes. Additionally, intercalating submicron and micron-sized graphene oxides into highly oriented large-sheet graphene oxide fibers can increase their density.

[0004] However, the methods for preparing submicron and micron-sized graphene oxide on an industrial scale are limited. Most methods use graphite powder as a raw material, and size control focuses on altering the oxidation pathway and mechanical energy input, such as controlling the amount and ratio of acid, increasing reaction time to ensure complete oxidation, and ultrasonic exfoliation of large sheets in a water bath. This random, top-down size reduction method is unlikely to result in a uniform size distribution, thus leading to low yields of submicron and micron-sized graphene oxide. In practical applications, further size separation is needed to screen submicron and micron-sized graphene oxide (e.g., density gradient separation, multi-stage centrifugation, etching film screening, field flow classification, etc.). This screening process increases the cost and time required for industrial preparation, further limiting the yield. Summary of the Invention

[0005] The purpose of this invention is to provide a method and product for preparing submicron and micron-sized graphene oxide using coal. This method uses inexpensive raw materials, has a simple process, high yield, and produces submicron and micron-sized graphene oxide with uniform particle size.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing submicron and micron-sized graphene oxide using coal includes the following steps:

[0008] Step 1: Graphitize coal or its derivative powder to obtain graphitized coal.

[0009] Step 2: Mix sulfuric acid and phosphoric acid at a volume ratio of 3:1 to 10:1 to form an acid mixture solution. Add the graphitized coal obtained in Step 1 to the acid mixture solution to a concentration of 0.005 to 0.05 g / mL. Heat the acid mixture solution to 40 to 60°C. Then, while stirring, add potassium permanganate in portions. The mass ratio of potassium permanganate to graphitized coal is 1:1 to 1:3. Stop heating after 10 to 24 hours to obtain reaction solution A.

[0010] Step 3: Add hydrogen peroxide dropwise to reaction solution A until the solution turns into yellow solution B;

[0011] Step 4: Pass the yellow solution B through a 2000-mesh sieve to obtain solution C;

[0012] Step 5: Centrifuge solution C and retain precipitate D;

[0013] Step 6: Disperse precipitate D in diethyl ether and filter it using a 0.45 μm filter membrane while stirring to obtain dry submicron and micron-sized graphene oxide powder.

[0014] Further, the coal or its derivatives in step one include one or more of anthracite, bituminous coal, sub-bituminous coal, metamorphic modified bituminous coal, coal gangue, peat, lignite, steam coal, weathered coal, coke, activated carbon, coal tar pitch, coal-based asphaltene, and coal-based humic acid.

[0015] Furthermore, the graphitization process in step one includes graphitization furnace treatment, Joule heat flash treatment, microwave treatment, electric heating wire heating, furnace tube heating, electric arc discharge induction, coil heating, laser ablation, and combinations thereof.

[0016] Furthermore, the graphitization furnace process involves maintaining the temperature at 1800–3000°C for 1–5 hours using a protective gas.

[0017] Furthermore, the protective gas comprises one or a combination of argon and nitrogen.

[0018] Furthermore, the Joule heat flash treatment is performed at a voltage of 40–480V for 100 ms to 5 s.

[0019] Furthermore, in step two, potassium permanganate is added in six separate additions, with each addition spaced 20 minutes apart.

[0020] Furthermore, in step five, the precipitate D is washed with hydrochloric acid solution and ethanol respectively, followed by centrifugation.

[0021] Furthermore, in step five, the centrifugation speed is 2000–10000 rpm, and the time is 10–20 min.

[0022] A submicron and micron-sized graphene oxide prepared according to the above-described method for preparing submicron and micron-sized graphene oxide using coal, wherein the graphene oxide contains alkyl groups, has an average particle size of 800 nm, and has an average of 1 to 2 sheets.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The preparation method of the present invention uses coal and its derivatives as raw materials. Compared with the traditional Hummers method, coal and its derivatives are cheap and readily available, pointing out a new path for the high-value utilization of coal. The yield of this preparation method is as high as 107%, which has industrial production value.

[0025] (2) The preparation method of the present invention uses coal and its derivatives as raw materials to prepare submicron and micron-sized graphene oxide. The obtained submicron and micron-sized graphene oxide contains alkyl chains and is also coal-based graphene oxide. The alkane chains contained in coal are retained during the graphitization and oxidation process. Alkyl groups are a significant feature that distinguishes coal-based graphene oxide from graphite-based graphene oxide, which is more conducive to the application of graphene in some solvent dispersion and advanced fields.

[0026] (3) The submicron and micron-sized graphene oxide prepared by this invention is coal-based graphene oxide. This coal-based graphene oxide can enhance the mechanical properties of graphene oxide films. On the one hand, the alkyl chains of coal-based graphene oxide repair the internal defects of graphene oxide through hydrogen bond pinning, inhibiting premature fracture of defects under stress. On the other hand, the alkane chains of coal-based graphene oxide pin the grain boundaries of graphene oxide through hydrogen bond pinning, reducing the mechanical failure behavior caused by grain boundary slip of graphene oxide, and ultimately greatly improving its tensile strength.

[0027] (4) The submicron and micron-sized graphene oxide prepared by the present invention can enhance the gas resistance performance of graphite-based graphene oxide film. The alkane chains contained in the submicron and micron-sized graphene oxide are pinned to the internal defects and grain boundaries of the graphite-based graphene oxide through hydrogen bonding, thereby inhibiting gas permeation by repairing defects and grain boundaries.

[0028] (5) The submicron and micron-sized graphene oxide prepared by the present invention can enhance the mechanical properties of polyacrylonitrile fibers. The submicron and micron-sized graphene oxide can be effectively and uniformly mixed with polyacrylonitrile under solution conditions and distributed inside the fiber under electrospinning and wet spinning process conditions, reducing defects and voids inside the composite fiber and improving the isotropic disadvantage of polyacrylonitrile-based fibers. Attached Figure Description

[0029] Figure 1 (a) XRD patterns of anthracite before and after graphitization in Example 1 of the present invention;

[0030] Figure 1 (b) Raman spectra of anthracite before and after graphitization in Example 1 of the present invention;

[0031] Figure 2 (a) is the XRD pattern of coal-based graphene oxide prepared in Example 1 of the present invention;

[0032] Figure 2 (b) is the Raman spectrum of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0033] Figure 3 (a) is the infrared spectrum of coal-based graphene oxide prepared in Example 1 of the present invention;

[0034] Figure 3 (b) is a thermogravimetric analysis image of coal-based graphene oxide prepared in Example 1 of the present invention;

[0035] Figure 3 (c) is the nuclear magnetic resonance spectrum of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0036] Figure 4 (a) is the XPS full spectrum of coal-based graphene oxide prepared in Example 1 of the present invention;

[0037] Figure 4 (b) is the C1s spectrum of XPS of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0038] Figure 4 (c) is the O1s spectrum of XPS of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0039] Figure 5 (a) is a SEM image of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0040] Figure 5 (b) is a TEM image of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0041] Figure 5 (c) is an HRTEM image of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0042] Figure 6 (a) is an AFM image of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0043] Figure 6 (b) is Figure 6 (a) The height curve of the line connecting AB;

[0044] Figure 6 (c) is a height statistics diagram of the coal-based graphene oxide prepared in Example 1 of the present invention;

[0045] Figure 7 (a) XRD patterns of anthracite before and after flash Joule heat treatment in Example 2 of the present invention;

[0046] Figure 7 (b) Raman spectra of anthracite coal before and after flash Joule heat treatment in Example 2 of the present invention;

[0047] Figure 8 (a) and (b) are SEM images of the coal-based graphene oxide prepared in Example 2 of the present invention;

[0048] Figure 9 (a) is a digital photograph of bituminous coal used in Embodiment 3 of the present invention;

[0049] Figure 9 (b) Photographs showing the dispersibility of coal-based graphene oxide prepared in Example 3 of the present invention in three solutions: water, DMSO, and DMF.

[0050] Figure 10(a) and (b) are SEM images of the coal-based graphene oxide prepared in Example 3 of the present invention;

[0051] Figure 11 (a) is a digital photograph of lignite used in Embodiment 4 of the present invention;

[0052] Figure 11 (b) Photographs showing the dispersibility of coal-based graphene oxide prepared in Example 4 of the present invention in three solutions: water, DMSO, and DMF.

[0053] Figure 12 (a) and (b) are SEM images of the coal-based graphene oxide prepared in Example 4 of the present invention;

[0054] Figure 13 (a) and (b) are SEM images of the coal-based graphene oxide prepared in Example 5 of the present invention;

[0055] Figure 14 (a) and (b) are SEM images of submicron and micron-sized graphene oxide obtained by size separation in Example 1 of the present invention;

[0056] Figure 15 (a) is a liquid crystal image of graphene oxide prepared using the coal-based graphene oxide of Example 1 of the present invention;

[0057] Figure 15 (b) SEM image of coal-based graphene oxide reinforced polyacrylonitrile fiber prepared using Example 1 of the present invention;

[0058] Figure 16 (a) is a bending diagram of the coal-based graphene oxide reinforced graphene oxide film prepared in Example 10 of the present invention;

[0059] Figure 16 (b) is a cross-sectional SEM image of the coal-based graphene oxide-reinforced graphene oxide film prepared in Example 10 of the present invention.

[0060] Figure 16 (c) Comparison of mechanical properties between conventional graphene oxide film and the coal-based graphene oxide-reinforced graphene oxide film prepared in Example 1.

[0061] Figure 17 (a) is a photograph of the graphene oxide aerogel prepared in Example 12 of the present invention;

[0062] Figure 17 (b) is a SEM image of the graphene oxide aerogel prepared in Example 12 of the present invention;

[0063] Figure 18 (a) SEM image of polyacrylonitrile fibers without the addition of alkyl graphene oxide prepared in this invention.

[0064] Figure 18 (b) SEM image of polyacrylonitrile fibers with 0.5% alkyl graphene oxide added, prepared in Example 1 of this invention;

[0065] Figure 18 (c) SEM image of polyacrylonitrile fibers with 1% alkyl graphene oxide added, prepared in Example 1 of this invention;

[0066] Figure 18 (d) is a SEM image of polyacrylonitrile fibers with 10% alkyl graphene oxide added, prepared in Example 1 of this invention. Detailed Implementation

[0067] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0068] This invention utilizes coal and its derivatives to prepare submicron and micron-sized graphene oxide. The preparation method includes the following steps:

[0069] Step 1: Graphitize coal and its derivative powders to obtain graphitized coal. Graphitization rearranges the short-range ordered and long-range disordered carbon atoms in the coal, causing sp... 2 Growth of hybrid carbon crystal regions;

[0070] Step 2: Mix sulfuric acid and phosphoric acid in a volume ratio of 3:1 to 10:1 to form an acid mixture solution. Add the graphitized coal obtained in Step 1 to the acid mixture solution to a concentration of 0.005 to 0.05 g / mL. Heat the acid mixture solution to 40 to 60°C. Then, while stirring, add potassium permanganate in portions. The mass ratio of potassium permanganate to graphitized coal is 1:1 to 1:3. Add the potassium permanganate in 6 portions, with an interval of 20 minutes between each addition. Stop heating after 10 to 24 hours to obtain reaction solution A.

[0071] Step 3: Add hydrogen peroxide dropwise to reaction solution A to react with potassium permanganate and high-valent manganese salt in the solution until the solution turns into yellow solution B;

[0072] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities in the solution, and obtain solution C. The sieve can be a polytetrafluoroethylene sieve or a stainless steel sieve.

[0073] Step 5: Centrifuge solution C at 2000-10000 rpm for 10-20 min, retain the precipitate, and then wash the precipitate with hydrochloric acid solution and ethanol respectively by centrifugation to obtain precipitate D;

[0074] Step 6: Disperse precipitate D in diethyl ether and filter it using a 0.45 μm filter membrane. The filter membrane is a polytetrafluoroethylene (PTFE) membrane. Stir while filtering to obtain dry submicron and micron-sized coal-based graphene oxide powder.

[0075] Example 1:

[0076] Step one: After grinding the anthracite into powder, place it in an ultra-high temperature graphitization furnace and perform high-temperature graphitization treatment at 2800℃ under an argon atmosphere for 3 hours. This process causes the short-range ordered and long-range disordered carbon atoms in the anthracite to rearrange, resulting in sp... 2 The growth of hybrid carbon crystal regions yields graphitized anthracite;

[0077] Step 2: Take 3g of graphitized anthracite and put it into a mixed solution of 360mL sulfuric acid and 40mL phosphoric acid. Heat the solution to 50℃ and add 3g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. After heating for 13h, stop to obtain reaction solution A.

[0078] Step 3: After the reaction solution A has cooled, transfer it to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0079] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0080] Step 5: Centrifuge solution C at 8000 rpm for 10 min, retain the precipitate, and then wash the precipitate with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0081] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0082] The coal-based graphene oxide powder prepared above was analyzed as follows:

[0083] 1. Phase structure of graphitized anthracite

[0084] Figure 1(a) shows the XRD patterns of raw anthracite and anthracite after heat treatment at 2800℃. The (002) diffraction peak represents the orientation degree of the aromatic carbon layers. The clearer the (002) diffraction peak, the higher the order of the aromatic carbon layers. It can be seen from the figure that the raw anthracite does not show any obvious peaks. At this time, the carbon atoms may be arranged in a short-range ordered and long-range disordered form. When the treatment temperature is increased to 2800℃, the diffraction angle corresponding to (002) is 26.46°. It is calculated that d002 = 0.3365nm, which gradually approaches the interlayer spacing of ideal graphite of 0.3354nm. Figure 1 (b) Raman spectra of raw anthracite and anthracite after heat treatment at 2800℃ are shown. The D peak and G peak reflect the defects and ordered sp atoms in the atomic crystals of the sample, respectively. 2 Carbon plane, intensity ratio of D band to G band (I) D / I G As a recognized indicator of the degree of order and graphitization in carbon materials, a higher D-value indicates more defects in the atomic crystal. Both raw anthracite and graphitized anthracite exhibit a significant D-peak (1350 cm⁻¹). -1 ) and G peak (1380cm) -1 The sample I after heat treatment at 2800℃ D / I G The value is 0.07, indicating a significant increase in the degree of orderliness in the carbon layer arrangement. 2D peak (2688 cm⁻¹) -1 The I peak, being an overtone of the D peak, indicates the number of graphite layers. After graphitization at 2800℃, the sample's I... 2D / I G It is 0.48, which is less than the I of monolayer graphite. 2D / I G =2, therefore the product obtained after high-temperature heat treatment still consists of multiple carbon layers.

[0085] 2. Phase structure of coal-based graphene oxide

[0086] Figure 2 (a) shows the XRD pattern of coal-based graphene oxide. It can be observed that the characteristic diffraction peak of graphene oxide appears at 9.5°, and its interplanar spacing increases from 0.3365 nm to 0.9302 nm. This is due to the introduction of oxygen-containing groups such as carboxyl and hydroxyl groups, which causes the adjacent aromatic carbon layers to be peeled apart, resulting in an increase in the interplanar spacing. Figure 2 (b) shows the Raman spectrum of coal-based graphene oxide. Due to the introduction of oxygen-containing groups into the graphene oxide itself, causing lattice distortion and twisting, the corresponding D peak intensity is relatively high, reflecting the increased internal defects of the graphene oxide.

[0087] Figure 3 (a) shows the infrared spectrum of coal-based graphene oxide. The spectrum is in the range of 3200–3400 cm⁻¹.-1 The broad and strong absorption peak at 1730 cm⁻¹ is due to the stretching vibration of the phenolic hydroxyl group (-OH). -1 The absorption peak at 1622 cm⁻¹ is caused by the stretching vibration of C=O, indicating the presence of carboxylic acids, esters, etc. -1 The absorption peak at that point is due to sp 2 The hybridization of C=C is the cause, at 1413 cm⁻¹ -1 1226cm -1 And 1042cm -1 The absorption peak at that point is caused by the stretching vibration of CO. Figure 3 (b) shows the thermogravimetric analysis (TGA) images of coal-based graphene oxide. The mass of graphene oxide decreases sharply between 100 and 300 °C, mainly due to the decomposition of some unstable oxygen-containing groups, producing CO, CO2, and steam. When the temperature continues to rise from 300 °C to 1000 °C, the rate of mass loss of graphene oxide becomes more gradual; this process is primarily attributed to the removal of some more stable oxygen-containing functional groups. Figure 3 (c) shows the NMR spectrum of coal-based graphene oxide, which corroborates the types of functional groups in the infrared spectrum, including peaks similar to those in graphite-based graphene oxide. In particular, coal-based graphene oxide... 13 The C NMR spectrum showed two additional peaks at 15 ppm and 34 ppm, corresponding to the -CH3 and -CH2 groups, respectively. These peaks are attributed to the alkyl chain bridging bonds present in coal, which are partially retained during graphitization and oxidation. This is a significant feature that distinguishes coal-based graphene oxide from graphite-based graphene oxide.

[0088] Figure 4 (a), (b), and (c) are the XPS full spectrum, C1s spectrum, and O1s spectrum of coal-based graphene oxide, respectively. In the XPS full spectrum, there are two very obvious peaks at 284 eV and 533 eV, corresponding to the C1s and O1s spectra, respectively. The C1s peak can be divided into four peaks: C=C (284.8 eV), CO (285.7 eV), C=O (288.0 eV), and OC=O (289.4 eV). The O1s peak can be divided into three peaks: C=O (531.5 eV), CO (532.5 eV), and OC=O (533.1 eV).

[0089] 3. Morphological characterization of coal-based graphene oxide

[0090] Figure 5 The SEM image in (a) shows clear graphene oxide sheets, mostly in the submicron scale, with a few sheets reaching 3–4 μm in size. Figure 5 (b) The TEM image shows the wrinkles in the graphene oxide, which is a typical feature of monolayer graphene oxide. Figure 5(c) The HRTEM image shows obvious lattice fringes and incomplete lattice regions, which are manifestations of defects in graphene oxide.

[0091] Figure 6 (a) shows AFM images of coal-based graphene oxide. Figure 6 The layers in (a) were analyzed for height, and their average thickness was approximately 1.45 nm. Figure 6 As shown in (b). Figure 6 (c) is a high-level statistical analysis of coal-based graphene oxide, and most of the prepared coal-based graphene oxide is monolayer.

[0092] Example 2:

[0093] Step 1: Grind the anthracite into powder and place it in a flash joule heating device. Add a certain amount of carbon black to make its resistance 2-10Ω. Treat it at a voltage of 40-480V for 100ms-5s to obtain the anthracite after flash joule heat treatment.

[0094] Step 2: Take 1.5g of anthracite after flash joule heat treatment and put it into a mixed solution of 180mL sulfuric acid and 20mL phosphoric acid. Heat the solution to 50℃ and add 1.5g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 15h to obtain reaction solution A.

[0095] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice cubes. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0096] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0097] Step 5: Centrifuge solution C at 10,000 rpm for 10 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0098] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0099] The coal-based graphene oxide powder prepared above was analyzed as follows:

[0100] 1. Phase structure of anthracite before and after Joule flash evaporation

[0101] Figure 7(a) XRD patterns of Taixi anthracite after Joule flash graphitization treatment and original Taixi anthracite are shown respectively. After Joule flash treatment, the intensity of the diffraction peak corresponding to the (002) crystal plane of the anthracite is greatly improved and the half-peak width is reduced, proving that the lattice structure of the anthracite tends to be ordered after flash treatment. Figure 7 (b) Raman spectra of anthracite after Joule heat flash evaporation and graphitization treatment and that of raw anthracite are shown. Compared to raw anthracite, the flash-treated anthracite exhibits a shorter D peak and a sharper G peak, while its I peak is lower. D / I G The lower value indicates that the anthracite treated with flash evaporation has fewer defects. On the other hand, compared with Example 1, its improvement effect is not as significant as that of high-temperature graphitization treatment. This may be because the treatment time is shorter, thereby reducing the effect of sp during the heat preservation process. 2 Rearrangement and growth of carbon domains.

[0102] 2. Morphological characterization of coal-based graphene oxide

[0103] Figure 8 Images (a) and (b) show SEM images of coal-based graphene oxide prepared by Joule heating flash evaporation of anthracite. The images demonstrate that monolayer graphene oxide can be obtained through Joule heating graphitization, a method that significantly reduces time costs while consuming relatively little energy.

[0104] Example 3:

[0105] Step one: After grinding bituminous coal into powder, it is placed in an ultra-high temperature graphitization furnace and subjected to high-temperature graphitization treatment at 3000℃ under an argon atmosphere for 2 hours. This process causes the short-range ordered and long-range disordered carbon atoms in the bituminous coal to rearrange, thus achieving the desired graphitization effect. 2 The growth of hybrid carbon crystal regions yields graphitized bituminous coal;

[0106] Step 2: Take 6g of graphitized bituminous coal and put it into a mixed solution of 720mL sulfuric acid and 80mL phosphoric acid. Heat the solution to 55℃ and add 6g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 12h to obtain reaction solution A.

[0107] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice cubes. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0108] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0109] Step 5: Centrifuge solution C at 7000 rpm for 10 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0110] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0111] The coal-based graphene oxide powder prepared above was analyzed as follows:

[0112] Figure 9 (a) is a digital photograph of bituminous coal. Figure 9 (b) The dispersibility of coal-based graphene oxide prepared from bituminous coal in water, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). As can be seen from the figure, the graphene oxide has good dispersibility in all three solutions.

[0113] Figure 10 Images (a) and (b) show SEM images of coal-based graphene oxide prepared from bituminous coal. The images show that the graphene oxide prepared from bituminous coal is relatively small, with most falling within the submicron scale, confirming the feasibility of preparing graphene oxide from bituminous coal and opening up new avenues for the high-value utilization of bituminous coal.

[0114] Example 4:

[0115] Step one: After grinding lignite into powder, it is placed in an ultra-high temperature graphitization furnace and subjected to high-temperature graphitization treatment at 2500℃ under an argon atmosphere for 3 hours. This process causes the short-range ordered and long-range disordered carbon atoms in the lignite to rearrange, thus achieving the desired graphitization effect. 2 The growth of hybrid carbon crystal regions yields graphitized lignite;

[0116] Step 2: Take 3g of graphitized lignite and put it into a mixed solution of 360mL sulfuric acid and 40mL phosphoric acid. Heat the solution to 50℃ and add 3g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 13h to obtain reaction solution A.

[0117] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0118] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0119] Step 5: Centrifuge solution C at 8000 rpm for 10 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge twice at the same speed to obtain precipitate D;

[0120] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0121] The coal-based graphene oxide powder prepared above was analyzed as follows:

[0122] Figure 11 (a) is a digital photograph of lignite. Figure 11 (b) The dispersibility of coal-based graphene oxide prepared from lignite in water, dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). As can be seen from the figure, the graphene oxide has good dispersibility in all three solutions.

[0123] Figure 12 Images (a) and (b) show SEM images of coal-based graphene oxide prepared from lignite. The images reveal monolayer lignite-based graphene oxide, indicating that this method for preparing graphene oxide is applicable to various coal types.

[0124] Example 5:

[0125] Step one involves grinding anthracite into powder and placing it in an ultra-high temperature graphitization furnace. Under an argon atmosphere, the powder is graphitized at 2500℃ for 3 hours. This process rearranges the short-range ordered and long-range disordered carbon atoms in the anthracite, allowing the sp... 2 The growth of hybrid carbon crystal regions yields graphitized anthracite;

[0126] Step 2: Take 3g of graphitized anthracite and put it into a mixed solution of 252mL sulfuric acid and 28mL phosphoric acid. Heat the solution to 50℃ and add 3g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 13h to obtain reaction solution A.

[0127] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0128] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0129] Step 5: Centrifuge solution C at 8000 rpm for 15 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0130] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0131] The coal-based graphene oxide powder prepared above was analyzed as follows:

[0132] Figure 13 (a) and (b) show SEM images of coal-based graphene oxide prepared from anthracite. Compared to Example 1, the amount of acid used in the preparation process of Example 5 was reduced by 30%. As can be seen from the images, by reducing the amount of acid, larger graphene oxide (>10 μm) can be prepared, which means that the cost can be further reduced and the size of graphene oxide can be increased.

[0133] Example 6

[0134] Step one: After grinding coal tar pitch into powder, place it in an ultra-high temperature graphitization furnace and perform high-temperature graphitization treatment at 2600℃ under an argon atmosphere for 2 hours. This process causes the short-range ordered and long-range disordered carbon atoms in the coal tar pitch to rearrange, thus achieving the desired graphitization effect. 2 The growth of hybrid carbon crystal regions yields graphitized coal tar pitch.

[0135] Step 2: Take 3g of graphitized coal tar pitch and put it into a mixed solution of 400mL sulfuric acid and 40mL phosphoric acid. Heat the solution to 60℃ and add 2g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 15h.

[0136] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0137] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0138] Step 5: Centrifuge solution C at 6000 rpm for 15 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge twice at the same speed to obtain precipitate D;

[0139] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0140] Example 7:

[0141] Step one: After grinding coal gangue into powder, place it in an ultra-high temperature graphitization furnace and perform high-temperature graphitization treatment at 2900℃ under an argon atmosphere for 5 hours. This process rearranges the short-range ordered and long-range disordered carbon atoms in the coal gangue, allowing the sp... 2 The growth of hybrid carbon crystal regions yields graphitized coal gangue;

[0142] Step 2: Take 3g of graphitized coal gangue and put it into a mixed solution of 300mL sulfuric acid and 100mL phosphoric acid. Heat the solution to 45℃ and add 2.5g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 17h.

[0143] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0144] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0145] Step 5: Centrifuge solution C at 7000 rpm for 15 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0146] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0147] Example 8:

[0148] Step one: Place the sub-bituminous coal and metamorphic modified bituminous coal powder in an ultra-high temperature graphitization furnace and perform high-temperature graphitization treatment at 1800℃ under a nitrogen atmosphere for 4 hours. This process causes the short-range ordered and long-range disordered carbon atoms in the sub-bituminous coal and metamorphic modified bituminous coal to rearrange, thus achieving the desired effect. 2 The growth of hybrid carbon crystal regions yields graphitized coal;

[0149] Step 2: Take 3g of graphitized coal and put it into a mixed solution of 200mL sulfuric acid and 50mL phosphoric acid. Heat the solution to 40℃ and add 2g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 24h.

[0150] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0151] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0152] Step 5: Centrifuge solution C at 2000 rpm for 20 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge at the same speed to obtain precipitate D;

[0153] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0154] Example 9:

[0155] Step one: Peat, steam coal, and weathered coal powder are placed in an ultra-high temperature graphitization furnace and subjected to high-temperature graphitization treatment at 2000℃ under a nitrogen and argon atmosphere for 1 hour. This process causes the short-range ordered and long-range disordered carbon atoms in the peat, steam coal, and weathered coal to rearrange, thus achieving the desired graphitization effect. 2 The growth of hybrid carbon crystal regions yields graphitized coal;

[0156] Step 2: Take 3g of graphitized coal and put it into a mixed solution of 250mL sulfuric acid and 50mL phosphoric acid. Heat the solution to 60℃ and add 1.5g of potassium permanganate in portions while stirring, with an interval of 20min between each addition. Stop heating after 10h.

[0157] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0158] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0159] Step 5: Centrifuge solution C at 5000 rpm for 15 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively. Centrifuge twice at the same speed to obtain precipitate D.

[0160] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0161] Example 10:

[0162] Step 1: Place coke, activated carbon, and coal-based pitch powder in a microwave oven and microwave them under a nitrogen atmosphere at 2500℃ for 2 hours. This causes the short-range ordered and long-range disordered carbon atoms in the coke, activated carbon, and coal-based pitch to rearrange, thus achieving the desired effect. 2The growth of hybrid carbon crystal regions yields graphitized coal;

[0163] Step 2: Take 3g of graphitized coal and put it into a mixed solution of 300mL sulfuric acid and 50mL phosphoric acid. Heat the solution to 50℃ and add 1.2g of potassium permanganate in 6 portions while stirring, with an interval of 20min between each addition. Stop heating after 20h.

[0164] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0165] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0166] Step 5: Centrifuge solution C at 4000 rpm for 20 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively, and centrifuge twice at the same speed to obtain precipitate D;

[0167] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0168] Example 11:

[0169] Step one: Place coal-based humic acid powder in a furnace tube and perform high-temperature graphitization treatment at 2900℃ under an argon atmosphere for 5 hours. This process rearranges the short-range ordered and long-range disordered carbon atoms in the coal-based humic acid, allowing the sp... 2 The growth of hybrid carbon crystal regions yields graphitized coal;

[0170] Step 2: Take 3g of graphitized coal and put it into a mixed solution of 350mL sulfuric acid and 50mL phosphoric acid. Heat the solution to 55℃ and add 1g of potassium permanganate in portions while stirring, with an interval of 20min between each addition. Stop heating after 10h.

[0171] Step 3: After the reaction solution A cools down, transfer the reaction solution A to a beaker containing an appropriate amount of ice. While transferring, add ice cubes and add hydrogen peroxide dropwise to the reaction solution A until the solution turns yellow, thus obtaining yellow solution B.

[0172] Step 4: Pass the yellow solution B through a 2000-mesh sieve to remove unreacted black impurities from the solution, and obtain solution C;

[0173] Step 5: Centrifuge solution C at 3000 rpm for 15 min, retain the precipitate, and then wash it with 10% dilute hydrochloric acid solution and ethanol respectively. Centrifuge twice at the same speed to obtain precipitate D.

[0174] Step 6: Disperse precipitate D in diethyl ether and filter under reduced pressure using a 0.45 μm polytetrafluoroethylene filter membrane while stirring to obtain dry coal-based graphene oxide powder.

[0175] This invention also provides a method for separating the coal-based graphene oxide prepared above, comprising the following steps:

[0176] Step 1: The pH of the 0.8 mg / mL coal-based graphene oxide solution prepared using the product prepared in Example 1 was adjusted to 4 using hydrochloric acid.

[0177] Step 2: Let the solution stand for 1 hour, take the precipitate and readjust the pH to neutral. The precipitate is micron-sized graphene oxide, and the supernatant is submicron-sized graphene oxide.

[0178] like Figure 14 (a) and (b) show the SEM images of the separated submicron and micron-sized graphene oxide. Figure 14 (a) shows that most of the graphene oxide sheets are larger than 1 μm and belong to micron-scale graphene oxide. Figure 14 (b) shows that most of the graphene oxide sheets are less than 1 μm in size, ranging from tens of nanometers to hundreds of nanometers, and belong to the submicron level of graphene oxide.

[0179] This invention provides a method for enhancing the mechanical properties of electrospun polyacrylonitrile fibers using coal-based graphene oxide, comprising the following steps:

[0180] Step 1: Weigh 500 mg of polyacrylonitrile and 5-50 mg of coal-based graphene oxide prepared in Example 1;

[0181] Step 2: After thoroughly mixing the two powders, disperse them in 10 mL of dimethyl sulfoxide and stir with a magnetic stirrer for at least 24 hours.

[0182] Step 3: Place the stirred solution into a 10cc syringe and apply a voltage of 14kV for electrospinning;

[0183] Step four: Use an electric roller to collect the ejected fibers, and transfer them to an oven for drying after spinning is complete.

[0184] Figure 15 (a) 5% coal-based graphene oxide dispersed in N,N-dimethylformamide solution showed a continuous polarizing crystalline region, proving the formation of a continuous liquid crystal phase; Figure 15(b) is a SEM image of polyacrylonitrile fiber with 1% coal-based graphene oxide added. It can be seen that the fiber is fully stretched under the action of electrostatic force, and there is no uneven agglomeration or wrinkles on the surface. It is relatively smooth, indicating that submicron and micron-sized coal-based graphene oxide can be well coated in polyacrylonitrile fiber and play a role in enhancing mechanical properties.

[0185] This invention provides a method for enhancing the mechanical properties of wet-spun polyacrylonitrile fibers using coal-based graphene oxide, comprising the following steps:

[0186] Step 1: Weigh 500 mg of polyacrylonitrile and 5-50 mg of coal-based graphene oxide prepared in Example 1;

[0187] Step 2: After thoroughly mixing the two powders, disperse them in 20 mL of N,N-dimethylformamide solution and stir with a magnetic stirrer for at least 5 hours;

[0188] Step 3: Fibers were prepared by wet spinning in hot water at 25-45 degrees Celsius using a dispensing machine. The dispensing needle diameter was 0.06 mm and the traction speed was 1-2 cm / s.

[0189] The mechanical properties of the obtained fibers were tested using a dynamic thermomechanical analyzer. Figure 18 (a) to (d) are SEM images of polyacrylonitrile fibers with 0%, 0.5%, 1%, and 10% graphene oxide addition, respectively. It can be seen that the addition of graphene oxide can effectively reduce defects and voids within the composite fibers. With increasing addition, the fiber structure becomes more compact, and the fiber orientation increases, thus potentially improving mechanical properties.

[0190] This invention provides a method for enhancing the mechanical properties of graphite-based graphene oxide films using coal-based graphene oxide, comprising the following steps:

[0191] Step 1: Weigh 58.2 mg of graphite-based graphene oxide and 1.8 mg of coal-based graphene oxide prepared in Example 1;

[0192] Step 2: Mix the two types of graphene oxide and disperse them in 20 mL of water, then stir with a magnetic stirrer for at least 2 hours.

[0193] Step 3: Filter the well-dispersed graphene oxide solution under reduced pressure in a filter cup with a diameter of 5 cm until the graphene oxide film formed on the filter membrane is completely dry.

[0194] The graphene oxide membrane was gently peeled off the filter membrane, and its mechanical properties were tested using a dynamic thermomechanical analyzer. Figure 16 (a) The prepared coal-based graphene oxide reinforced graphene oxide film was found to have good plasticity and toughness by bending it. Figure 16(b) is a SEM image of the graphene oxide film, which clearly shows that the interior of the film is composed of many stacked graphene oxide sheets, exhibiting a very obvious layered structure. Figure 16 (c) The mechanical properties of the prepared graphite-based graphene oxide film and the graphene oxide film doped with 3% coal-based graphene oxide are compared. The tensile strength of the graphite-based graphene oxide film is 5.12 MPa, while the tensile strength of the film doped with 3% coal-based graphene oxide increases to 11.23 MPa, which is 119% higher than the original. The elongation at break also increases by 23% from 0.99% to 1.22%. It can be seen that the submicron and micron-sized coal-based graphene oxide prepared by this invention has certain advantages in enhancing mechanical properties.

[0195] This invention provides a method for preparing graphene oxide aerogel, comprising the following steps:

[0196] Step 1: Weigh 400 mg of the coal-based graphene oxide prepared in Example 1 and place it in a glass bottle with a diameter of 1 cm;

[0197] Step 2: Add 2 mL of water and stir with a magnetic stirrer for 2 hours until the graphene oxide becomes a gel.

[0198] Step 3: Freeze-dry the graphene oxide hydrogel using a freeze dryer to obtain graphene oxide aerogel.

[0199] Figure 17 (a) is the prepared graphene oxide aerogel, which has the appearance of yellow graphene oxide and features low density and porous structure. Figure 17 (b) is a SEM image of graphene oxide aerogel. The image shows many pores of about 2 to 3 μm, which exhibits the porous characteristics of aerogel materials.

[0200] In summary, the preparation method of this invention achieves a yield of up to 107%, which is higher than the yield of small-sized graphene oxide prepared from graphite. The prepared graphene oxide has an average size of 800 nm and an average number of 1 to 2 layers. Because coal is used as the raw material, the alkyl groups contained in the coal are retained during the graphitization and oxidation process. Therefore, the prepared graphene oxide contains alkyl groups, which enable it to be dispersed in more solvents, further expanding its application range. The alkyl graphene oxides obtained through sieve and filter membrane filtration are all submicron and micron-sized. These submicron and micron-sized alkyl graphene oxides can enhance the mechanical properties and gas barrier properties of graphite-based graphene oxide films, while also enhancing the mechanical properties of polyacrylonitrile fibers and improving the isotropy of polyacrylonitrile-based fibers.

Claims

1. A method for producing sub-micron and micron-sized graphene oxide using coal, characterized by, Includes the following steps: Step 1: Graphitize coal or its derivative powder to obtain graphitized coal. Step 2: Mix sulfuric acid and phosphoric acid at a volume ratio of 3:1 to 10:1 to form an acid mixture solution. Add the graphitized coal obtained in Step 1 to the acid mixture solution to a concentration of 0.005 to 0.05 g / mL. Heat the acid mixture solution to 40 to 60°C. Then, while stirring, add potassium permanganate in 6 portions, with each addition 20 min apart. The mass ratio of potassium permanganate to graphitized coal is 1:1 to 1:

3. Stop heating after 10 to 24 h to obtain reaction solution A. Step 3: Add hydrogen peroxide dropwise to reaction solution A until the solution turns into yellow solution B; Step 4: Pass the yellow solution B through a 2000-mesh sieve to obtain solution C; Step 5: Centrifuge solution C, retain precipitate D, and then wash precipitate D with hydrochloric acid solution and ethanol respectively, followed by centrifugation at 2000-10000 rpm for 10-20 min. Step 6: Disperse precipitate D in diethyl ether and filter it using a 0.45 μm filter membrane while stirring to obtain dry submicron and micron-sized graphene oxide powder. The graphene oxide contains alkyl groups, has an average particle size of 800 nm, an average thickness of 1.45 nm, and an average of 1 to 2 sheets.

2. The method of claim 1, wherein the coal is used to produce sub-micron and micron-sized graphene oxide. The coal or its derivatives in step one include one or more of the following: anthracite, bituminous coal, sub-bituminous coal, metamorphic modified bituminous coal, coal gangue, peat, lignite, steam coal, weathered coal, coke, activated carbon, coal tar pitch, coal-based asphaltene, and coal-based humic acid.

3. The method of claim 1, wherein the coal is used to produce sub-micron and micron-sized graphene oxide. The graphitization process in step one includes graphitization furnace treatment, Joule heat flash treatment, microwave treatment, electric heating wire heating, furnace tube heating, electric arc discharge, induction coil heating, laser ablation, and combinations thereof. Specifically, the graphitization furnace treatment uses a protective gas to maintain the temperature at 1800–3000 °C for 1–5 h, and the protective gas includes argon, nitrogen, or a combination thereof. The Joule heat flash treatment is performed at a voltage of 40–480 V for 100 ms–5 s.

4. Sub-micron and micron-sized graphene oxide prepared by the method of any one of claims 1 to 3, characterized in that, (002) crystal plane spacing is 0.3365 nm, I D / I G 0.

07.

5. Sub-micron and micron-sized graphene oxide prepared by the method of any one of claims 1 to 3, wherein, Graphene oxide contains alkyl groups, has an average particle size of 800 nm, an average thickness of 1.45 nm, and an average of 1 to 2 sheets.

6. A sub-micron and micron-sized graphene oxide dispersion prepared according to the method of any one of claims 1-3, wherein, Graphene oxide contains alkyl groups, and the peaks shown in the NMR spectrum at 15 ppm and 34 ppm correspond to the two alkyl groups -CH3 and -CH2, respectively.

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