Green and environment-friendly low-cost sugar-based high-strength carbon fiber and preparation method thereof

Abstract

The application discloses a kind of green environmental protection low-cost sugar-based high-strength carbon fibers and preparation method thereof, belong to carbon fiber preparation technical field.The application uses renewable water-soluble saccharide as carbon source, uses water as solvent, prepares carbon fiber original wire by wet spinning, and is treated after pre-carbonization and carbonization, realizes the efficient synthesis of carbon fiber.The preparation method provided by the application is simple in process, short in period, green, cheap in raw material, low in production cost, and does not emit toxic and harmful substances.The obtained carbon fiber is uniform and dense in structure, has excellent mechanical properties, and has grooves on the surface, which is well combined with other materials when compounded.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber preparation technology, specifically relating to a green, environmentally friendly, low-cost sugar-based high-strength carbon fiber and its preparation method. Background Technology

[0002] Carbon fiber, with its superior properties such as high strength, high modulus, lightweight, high temperature resistance, and corrosion resistance, is widely used in automobile manufacturing, wind turbine blades, sporting goods, and aerospace. Thanks to its high specific strength and high specific modulus, carbon fiber performs exceptionally well as a reinforcing agent in composite materials, and is commonly used in carbon fiber reinforced resins and ceramic composites. Furthermore, its high-temperature resistance in extreme environments gives it unique application advantages, demonstrating broad development prospects.

[0003] Currently, traditional carbon fibers are mainly classified into polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers. Their precursor fiber preparation processes are complex and costly, often involving the use of toxic and hazardous substances. The precursor fibers require lengthy pre-oxidation and high-temperature carbonization processes, resulting in enormous energy consumption. This is particularly true in the preparation of PAN and pitch-based carbon fibers, where the high-temperature, multi-step processing severely limits further reductions in yield and cost. Furthermore, these traditional methods rely on non-renewable fossil resources, and the emission of toxic and hazardous gases during production has adverse environmental impacts. Although viscose-based carbon fibers are derived from natural cellulose, their alkalization and sulfurization processes are complex, still generating hazardous waste. Moreover, despite decades of effort, strength improvements have been limited, reaching a maximum of 1 GPa. Traditional carbon fiber production suffers from high costs, long preparation cycles, complex processes, high energy consumption, severe pollution, and a strong dependence on non-renewable fossil resources. To achieve green and sustainable development in carbon fiber production, a more environmentally friendly and low-cost alternative is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a green, environmentally friendly, low-cost sugar-based high-strength carbon fiber and its preparation method. Using renewable water-soluble sugars as the carbon source and water as the solvent, carbon fiber precursors are prepared through wet spinning, followed by pre-carbonization and carbonization treatments to achieve efficient carbon fiber synthesis. This method significantly reduces raw material and production costs, is simple and has a short cycle time, avoids the emission of toxic and harmful substances, and produces carbon fibers with a uniform and dense structure, excellent mechanical properties, and a rich groove structure on the surface that effectively enhances the bonding force with the composite matrix. The prepared carbon fiber is not only environmentally friendly but also has excellent market application prospects, and is expected to be widely used in the automotive and sporting goods industries.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention is to provide a green, environmentally friendly, low-cost method for preparing sugar-based high-strength carbon fibers, comprising the following steps:

[0007] A solution A is prepared by dissolving a gel monomer, a water-soluble sugar, and a crosslinking agent in water; a spinning aid, an initiator, and a catalyst are added to solution A to prepare a spinning solution.

[0008] Prepare a solution identical to solution A, and add an ion gelation aid as a coagulation bath;

[0009] A solution omitting the gel monomer, crosslinking agent, and spinning aid in the spinning solution is used as the water bath solution;

[0010] Carbon fiber precursor is obtained by wet spinning using the spinning solution, the coagulation bath, and the water bath solution.

[0011] The carbon fiber precursor is first pre-carbonized to obtain pre-carbonized fiber; then the pre-carbonized fiber is carbonized to obtain the green, environmentally friendly, low-cost sugar-based high-strength carbon fiber.

[0012] This invention uses water-soluble sugar as a carbon source to prepare carbon fiber precursor through a wet spinning process. The coagulation bath and water bath solution prepared in the wet spinning process can be recycled multiple times. Then, pre-carbonization is used to remove volatiles and moisture, promote the caramel reaction, reduce internal stress, avoid cracking and breakage, and complete the stabilization treatment to ensure fiber uniformity and strength. Finally, high-strength carbon fibers are obtained through carbonization.

[0013] Optionally, the gel monomer includes one or more of acrylic acid, methacrylic acid, acrylamide, and N-isopropylacrylamide.

[0014] Optionally, the water-soluble sugar includes one or more of glucose, fructose, galactose, maltose, sucrose, lactose, and fructooligosaccharides.

[0015] Optionally, the crosslinking agent includes one or more of ethylene glycol diacrylate, sodium acrylate, N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, diacrylamide ethylenediamine, and N,N'-ethylenebisacrylamide.

[0016] Preferably, the mass ratio of gel monomer, water-soluble sugar, crosslinking agent and water in solution A is 1-30:10-80:0.05-2:100.

[0017] Optionally, the spinning aid includes one or more of sodium alginate, sodium polyacrylate, and sodium carboxymethyl cellulose.

[0018] Optionally, the initiator includes one or more of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and hydrogen peroxide.

[0019] Optionally, the catalyst includes one or more of sodium sulfite, triethanolamine, and tetramethylethylenediamine.

[0020] Preferably, in the spinning solution, the spinning aid, initiator and catalyst are added in the form of aqueous solutions, wherein the concentration of the aqueous solution of the spinning aid is 1-10 wt.%, the concentration of the aqueous solution of the initiator is 0.5-20 wt.%, and the concentration of the aqueous solution of the catalyst is 0.5-20 wt.%.

[0021] Preferably, in the spinning solution, the mass ratio of the spinning aid to the water in solution A is 0.5 to 10:100.

[0022] In the spinning solution, the amount of initiator and catalyst added depends on the amount of gel monomer used, and can be added according to the conventional amounts used in the art.

[0023] Optionally, the ionogel additive includes calcium chloride and / or calcium acetate.

[0024] Preferably, the ion gelation aid accounts for 1 to 20% of the mass of the coagulation bath.

[0025] Preferably, during the wet spinning process, the temperature of the water bath solution is 25–90°C.

[0026] Preferably, the process parameters during the wet spinning process are: spinning needle inner diameter 30-200 μm, spinning speed 50-2000 μL / min, drawing machine speed 1-20 m / min, drying temperature 50-300℃, and drying time 1-30 min.

[0027] Preferably, the pre-carbonization is carried out by gradient heating, with the maximum temperature not exceeding 350°C.

[0028] More specific operating steps are as follows: the carbon fiber precursor is gradually heated in a continuous pre-carbonization furnace and passed through each temperature zone in a uniform traction manner to achieve stable pre-carbonization and obtain pre-carbonized fibers with uniform quality; the preferred fiber feeding speed is 0.02 to 1 m / min to ensure that the fiber gradually adapts to the heating process, avoids damage to the internal structure, and allows the precursor to have sufficient residence time in each temperature zone to react and form an ideal micro-nano structure.

[0029] Preferably, the carbonization is carried out under oxygen-free conditions, with direct or gradient heating to 800–2000°C at a heating rate of 1–20°C / min, and the holding time for each gradient is 0.5–6 h.

[0030] The second technical solution of the present invention provides a green, environmentally friendly, low-cost sugar-based high-strength carbon fiber prepared according to the above-mentioned green, environmentally friendly, low-cost sugar-based high-strength carbon fiber preparation method.

[0031] The third technical solution of the present invention provides a graphite fiber, which is obtained by graphitizing pre-carbonized fiber or green, environmentally friendly, low-cost sugar-based high-strength carbon fiber prepared according to the above preparation method.

[0032] Preferably, the graphitization temperature is 2000–3000℃, the heating rate is 0.5–20℃ / min, and the holding time is 0.5–6h.

[0033] The beneficial technical effects of the present invention are as follows:

[0034] This invention addresses the problems of high cost, long cycle, complex process, high energy consumption, serious pollution, and strong dependence on non-renewable fossil resources in traditional carbon fiber production. It innovatively proposes a green and low-cost method for preparing sugar-based high-strength carbon fibers. This method uses inexpensive, green, and renewable water-soluble sugars as the carbon source and water as the solvent, significantly reducing raw material and production costs while avoiding the emission of toxic and harmful substances. The preparation process is simple and short, yielding carbon fibers with a uniform and dense structure, excellent mechanical properties, and grooved surfaces, resulting in good bonding with other materials. Due to the low raw material cost and environmentally friendly manufacturing process, the carbon fibers provided by this invention have broad market application prospects and are expected to be widely used in the automotive and sporting goods industries. Attached Figure Description

[0035] Figure 1 The carbon fiber precursor preparation and collection process in Example 1 is shown below. Figure 1 Among them, (a) is a continuous collection production line for wet spinning, (b) is the running state of gel filament in hot drawing dryer, (c) is the collection roller of dried carbon fiber filament, and (d) is the collection state of dried carbon fiber filament at the hundred-meter level.

[0036] Figure 2 This is a temperature zone setting diagram for the continuous pre-carbonization furnace in Example 1.

[0037] Figure 3 This is a temperature zone setting diagram for the continuous pre-carbonization furnace in Examples 2-3.

[0038] Figure 4 The image shows the continuous pre-carbonization process of carbon fiber precursor in Example 1. (a) is a picture of the continuous pre-carbonization furnace, (b) to (e) are diagrams showing the state changes of the carbon fiber precursor as it gradually transitions from the low-temperature furnace chamber to the high-temperature furnace chamber, (f) shows the pre-carbonized fiber passing through the fiber pressure roller, (g) to (i) show the continuous collection of pre-carbonized fiber, and (j) is a picture of the collected 100-meter-long pre-carbonized fiber.

[0039] Figure 5 Images of the carbonization furnace used in Example 1 and the 100-meter-long carbon fiber prepared therefrom, wherein (a) is an image of the carbonization furnace and (b) is an image of the 100-meter-long carbon fiber.

[0040] Figure 6 The images shown are scanning electron microscope (SEM) images of the carbon fibers prepared in Example 1, where (a) is a surface morphology image and (b) is a cross-sectional morphology image.

[0041] Figure 7 The images shown are transmission electron microscope (TEM) images of the carbon fibers prepared in Example 1, where (a) is a high-resolution transmission electron microscope (HRTEM) image, (b) is a selected area electron diffraction (SAED) image, and (c) is a magnified view of (a).

[0042] Figure 8 The tensile strength diagram is for the carbon fiber prepared in Example 1.

[0043] Figure 9 The images shown are scanning electron microscope (SEM) images of the carbon fibers prepared in Example 2, where (a) is a surface morphology image and (b) is a cross-sectional morphology image.

[0044] Figure 10 The images shown are scanning electron microscope (SEM) images of the graphite fibers prepared in Example 3, where (a) is a surface morphology image and (b) is a cross-sectional morphology image. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0046] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0048] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0049] Example 1

[0050] (1) Preparation of spinning solution: First, take 42g of acrylic acid, 140g of glucose and 2.3g of ethylene glycol diacrylate and dissolve them in 385mL of deionized water, stirring to form a uniform and transparent solution. Then add 175mL of 4% sodium alginate aqueous solution, 14mL of 10% ammonium persulfate aqueous solution and 14mL of 10% tetramethylethylenediamine aqueous solution, sonicate and stir to form a uniform solution, remove the air bubbles in the spinning solution by a defoamer, and obtain the spinning solution for later use.

[0051] (2) Preparation of the coagulation bath: Dissolve 1800g of acrylic acid, 6000g of glucose, 150g of ethylene glycol diacrylate, and 1800g of calcium chloride in 16500mL of deionized water. Stir the solution in the coagulation bath to form a uniform and transparent solution. During the spinning process, turn on the circulation pump of the coagulation bath to circulate the coagulation bath in a specific direction. Furthermore, the coagulation bath can be reused multiple times after preparation.

[0052] (3) Preparation of water bath solution: 6000g of glucose, 600mL of 10% ammonium persulfate aqueous solution, and 600mL of 10% tetramethylethylenediamine aqueous solution are mixed and dissolved in 16500mL of deionized water. The mixture is stirred in a constant temperature water bath to form a uniform and transparent solution. During the spinning process, the heating device of the constant temperature water bath is turned on to stabilize the temperature of the water bath at 70℃. In addition, the water bath solution can be recycled multiple times after preparation.

[0053] (4) Preparation of carbon fiber precursor: The prepared spinning solution was drawn into a syringe and connected to a spinning needle with an inner diameter of 80 μm. Then, a high-precision injection pump was used to inject the spinning solution into the coagulation bath through the spinning needle at a rate of 500 μL / min to generate gel precursor fibers. The gel precursor fibers were then subjected to a 70℃ constant temperature water washing bath under the traction of a drawing machine at a speed of 8 m / min, and then dried in a 120℃ forced-air dryer. Finally, they were collected into bundles by a take-up roller to obtain carbon fiber precursor fibers. The preparation and collection process of carbon fiber precursor fibers is described in [link to documentation]. Figure 1 Among them, (a) is a continuous collection production line for wet spinning, (b) is the running state of gel filament in hot drawing dryer, (c) is the collection roller of dried carbon fiber filament, and (d) is the collection state of dried carbon fiber filament at the hundred-meter level.

[0054] (5) Pre-carbonization: Carbon fiber precursors are fed through a continuous pre-carbonization furnace at a speed of 0.05 m / min using a feeding machine and a traction machine. The precursors are uniformly drawn through each temperature zone to achieve stable pre-carbonization and obtain pre-carbonized fibers of uniform quality. The pre-carbonization production line adopts a 5-section furnace design, with 5 temperature zones in each section, for a total of 25 temperature zones, gradually increasing from 25℃ to 220℃. The temperature zones are distributed from low temperature, medium temperature to high temperature, gradually removing volatiles and moisture, promoting the caramel reaction, and completing the final stabilization treatment to ensure fiber uniformity and strength. See [link to continuous pre-carbonization furnace temperature zone settings] for details. Figure 2 The continuous pre-carbonization process of carbon fiber precursor is shown in [link to documentation]. Figure 4 Among them, (a) is a picture of a continuous pre-carbonization furnace, (b) to (e) are diagrams of the state changes of carbon fiber precursors as they gradually transition from a low-temperature furnace chamber to a high-temperature furnace chamber, (f) is a picture of the pre-carbonized fiber passing through a fiber pressure roller, (g) to (i) are pictures of the continuous collection of pre-carbonized fibers, and (j) is a picture of a hundred-meter-long pre-carbonized fiber that has been collected.

[0055] (6) Carbonization: The pre-carbonized fibers were carbonized in a carbonization furnace under vacuum conditions. The temperature was increased to 360℃, 920℃, 1050℃, and 1400℃ at a heating rate of 4℃ / min, and held for 2 hours at each temperature. The furnace was then cooled to room temperature to obtain carbon fibers. Images of the carbonization furnace used and the prepared 100-meter-long carbon fibers are shown below. Figure 5 Among them, (a) is a picture of a carbonization furnace, and (b) is a picture of 100-meter-long carbon fiber.

[0056] (7) Graphitization: The pre-carbonized fiber or carbon fiber is graphitized in a graphitization furnace. Under vacuum conditions, the temperature is raised to 1800℃ at a heating rate of 4℃ / min, and then raised to 2800℃ at a heating rate of 2℃ / min. The temperature is held for 2 hours and then the furnace is cooled to room temperature to obtain graphite fiber.

[0057] The scanning electron microscope (SEM) image of the carbon fiber prepared in Example 1 is shown below. Figure 6 In this diagram, (a) is a surface topography image and (b) is a cross-sectional topography image.

[0058] from Figure 6As can be seen from Figure (a), which shows a scanning electron microscope image of the carbon fiber surface, the groove structure distributed along the fiber axis can be clearly observed. This surface roughness helps the carbon fiber form a stronger mechanical interlock with the matrix in the composite material, thereby significantly improving the interfacial bonding strength. Figure (b) is a scanning electron microscope image of the carbon fiber cross-section. The cross-section is a regular circle and dense internally, with no obvious defects such as cracks or pores found, indicating that the carbon fiber has high structural integrity and excellent mechanical properties. Combining the characteristics of the two images, it can be inferred that the groove structure and dense cross-section of the carbon fiber work together to improve the overall mechanical properties of the composite material, making it have great application potential in reinforcing phase materials.

[0059] Transmission electron microscopy (TEM) images of the carbon fibers prepared in Example 1 are shown below. Figure 7 In the image, (a) is a high-resolution transmission electron microscope (HRTEM) image, (b) is a selected area electron diffraction (SAED) image, and (c) is a magnified view of (a).

[0060] from Figure 7 As can be seen from the TEM images of carbonized carbon fibers treated at 1400℃, the mixed structure of amorphous carbon and microcrystalline graphite is revealed. In the high-resolution transmission electron microscopy (HRTEM) image in Figure (a), the amorphous carbon regions are uniformly and disordered, without clear lattice fringes, while the microcrystalline graphite regions show a lattice structure with bright and dark fringes, and the lattice exhibits a certain degree of distortion at the microcrystalline scale. The image indicates that microcrystalline graphite is embedded in the amorphous carbon matrix, forming a composite microstructure. The selected area electron diffraction (SAED) pattern in Figure (b) shows bright rings, indicating a certain degree of crystallinity in the sample. The discrete bright spots on the rings correspond to the microcrystalline graphite regions, while the continuous rings reflect the presence of amorphous carbon. The inverse Fourier transform (IFFT) pattern in Figure (c) further highlights the bright and dark fringes of the lattice structure, allowing for a clearer identification of the shape and distribution of microcrystalline graphite. Based on performance, this mixed structure of carbon fibers is expected to possess excellent mechanical properties.

[0061] The tensile strength diagram of the carbon fiber prepared in Example 1 is shown below. Figure 8 Among them, 1#, 2#, and 3# represent the tensile strengths of different segments of the carbon fiber prepared in Example 1.

[0062] Example 2

[0063] (1) Preparation of spinning solution: First, take 36g of methacrylic acid, 120g of sucrose and 3g of N,N'-methylenebisacrylamide and dissolve them in 330mL of deionized water, stirring to form a uniform and transparent solution. Then add 120mL of 5% sodium alginate aqueous solution, 12mL of 10% azobisisobutyronitrile aqueous solution and 12mL of 10% sodium sulfite aqueous solution, sonicate and stir to form a uniform solution, remove the air bubbles in the spinning solution by a defoamer, and obtain the spinning solution for later use.

[0064] (2) Preparation of the coagulation bath: Dissolve 1800g of methacrylic acid, 6000g of sucrose, 150g of N,N'-methylenebisacrylamide, and 1800g of calcium chloride in 16500mL of deionized water. Stir the solution in the coagulation bath to form a uniform and transparent solution. During the spinning process, turn on the circulation pump of the coagulation bath to circulate the coagulation bath in a specific direction. Furthermore, the coagulation bath can be reused multiple times after preparation.

[0065] (3) Preparation of water bath solution: 6000g sucrose, 600mL of 10% azobisisobutyronitrile aqueous solution, and 600mL of 10% sodium sulfite aqueous solution are mixed and dissolved in 16500mL of deionized water. The solution is stirred in a constant temperature water bath to form a uniform and transparent solution. During the spinning process, the heating device of the constant temperature water bath is turned on to stabilize the temperature of the water bath at 60℃. In addition, the water bath solution can be recycled multiple times after preparation.

[0066] (4) Preparation of carbon fiber precursor: The prepared spinning solution was drawn into a syringe and connected to a spinning needle with an inner diameter of 60 μm. Then, a high-precision injection pump was used to inject the spinning solution into the coagulation bath through the spinning needle at a rate of 400 μL / min to generate gel precursor. The gel precursor was then subjected to a 60℃ constant temperature water washing tank under the traction of a drawing machine at a speed of 8 m / min, and then dried in a 90℃ forced-air dryer. Finally, it was collected into bundles by a take-up roller to obtain carbon fiber precursor.

[0067] (5) Pre-carbonization: Carbon fiber precursors are fed through a continuous pre-carbonization furnace at a speed of 0.1 m / min using a feeding machine and a traction machine. The precursors are uniformly drawn through each temperature zone to achieve stable pre-carbonization and obtain pre-carbonized fibers of uniform quality. The pre-carbonization production line adopts a 5-section furnace design, with 5 temperature zones in each section, for a total of 25 temperature zones, gradually increasing from 25℃ to 220℃. The temperature zones are distributed from low temperature, medium temperature to high temperature, gradually removing volatiles and moisture, promoting the caramel reaction, and completing the final stabilization treatment to ensure fiber uniformity and strength. See [link to continuous pre-carbonization furnace temperature zone settings] for details. Figure 3 .

[0068] (6) Carbonization: The pre-carbonized fiber is carbonized in a carbonization furnace. Under argon conditions, the temperature is increased to 1100℃ at a heating rate of 2℃ / min, held for 2 hours, and then cooled to room temperature to obtain carbon fiber.

[0069] (7) Graphitization: The pre-carbonized fiber or carbon fiber is graphitized in a graphitization furnace. Under argon conditions, the temperature is increased to 1800℃ at a heating rate of 8℃ / min, and then increased to 2600℃ at a heating rate of 4℃ / min. The temperature is held for 3 hours and then the furnace is cooled to room temperature to obtain graphite fiber.

[0070] The scanning electron microscope (SEM) image of the carbon fibers prepared in Example 2 is shown below. Figure 9 In this diagram, (a) is a surface topography image and (b) is a cross-sectional topography image.

[0071] from Figure 9 As shown in Figure (a), a scanning electron microscope (SEM) image of the carbon fiber surface, a distinct groove structure distributed along the fiber axis is revealed. This groove not only increases the surface roughness of the fiber but also provides a larger specific surface area, significantly enhancing the mechanical interlocking between the carbon fiber and the composite matrix, thereby improving the interfacial bonding strength. Figure (b) is an SEM image of the carbon fiber cross-section, which is a regular circle with a dense interior. No significant defects such as cracks or pores were observed, indicating that the fiber has good structural integrity during preparation. The presence of this surface groove structure effectively improves the interfacial properties of the composite material, while the dense cross-section indicates that the fiber itself possesses high mechanical properties, such as high strength and modulus. This type of carbon fiber has significant application potential in reinforced composite materials, especially suitable for fields with high mechanical performance requirements.

[0072] Example 3

[0073] (1) Preparation of spinning solution: First, take 42g of acrylamide, 140g of maltose and 2.3g of polyethylene glycol diacrylate and dissolve them in 385mL of deionized water, stirring to form a uniform and transparent solution. Then add 175mL of 6% sodium alginate aqueous solution, 14mL of 10% hydrogen peroxide aqueous solution and 14mL of 10% sodium sulfite solution, sonicate and stir to form a uniform solution, remove air bubbles from the spinning solution using a defoamer, and obtain the spinning solution for later use.

[0074] (2) Preparation of the coagulation bath: Dissolve 1800g of acrylamide, 6000g of maltose, 150g of ethylene glycol diacrylate, and 1800g of calcium chloride in 16500mL of deionized water. Stir the solution in the coagulation bath to form a uniform and transparent solution. During the spinning process, turn on the circulation pump of the coagulation bath to circulate the coagulation bath in a specific direction. Furthermore, the coagulation bath can be reused multiple times after preparation.

[0075] (3) Preparation of water bath solution: 6000g of maltose, 600mL of 10% hydrogen peroxide aqueous solution, and 600mL of 10% sodium sulfite solution are mixed and dissolved in 16500ml of deionized water. The mixture is stirred in a constant temperature water bath to form a uniform and transparent solution. During the spinning process, the heating device of the constant temperature water bath is turned on to stabilize the temperature of the water bath at 60℃. In addition, the water bath solution can be recycled multiple times after preparation.

[0076] (4) Preparation of carbon fiber precursor: The prepared spinning solution was drawn into a syringe and connected to a spinning needle with an inner diameter of 80 μm. Then, a high-precision injection pump was used to inject the spinning solution into the coagulation bath through the spinning needle at a rate of 600 μL / min to generate gel precursor. The gel precursor was then subjected to a 60℃ constant temperature water washing tank under the traction of a drawing machine at a speed of 9 m / min, and then dried in a 140℃ forced-air dryer. Finally, it was collected into bundles by a take-up roller to obtain carbon fiber precursor.

[0077] (5) Pre-carbonization: Carbon fiber precursors are fed through a continuous pre-carbonization furnace at a speed of 0.2 m / min using a feeding machine and a traction machine. The precursors are uniformly drawn through each temperature zone to achieve stable pre-carbonization and obtain pre-carbonized fibers of uniform quality. The pre-carbonization production line adopts a 5-section furnace design, with 5 temperature zones in each section, for a total of 25 temperature zones, gradually increasing from 25℃ to 220℃. The temperature zones are distributed from low temperature, medium temperature to high temperature, gradually removing volatiles and moisture, promoting the caramel reaction, and completing the final stabilization treatment to ensure fiber uniformity and strength. See [link to continuous pre-carbonization furnace temperature zone settings] for details. Figure 3 .

[0078] (6) Carbonization: The pre-carbonized fiber is carbonized in a carbonization furnace. Under vacuum conditions, the temperature is raised to 1500℃ at a heating rate of 5℃ / min and held for 3 hours. Then the furnace is cooled to room temperature to obtain carbon fiber.

[0079] (7) Graphitization: The pre-carbonized fiber or carbon fiber is graphitized in a graphitization furnace. Under vacuum conditions, the temperature is raised to 2800℃ at a heating rate of 2℃ / min, held for 1 hour, and then cooled to room temperature to obtain graphite fiber.

[0080] The scanning electron microscope (SEM) image of the graphite fibers prepared in Example 3 is shown below. Figure 10In this diagram, (a) is a surface topography image and (b) is a cross-sectional topography image.

[0081] from Figure 10 As shown in Figure (a), a scanning electron microscope (SEM) image of the graphite fiber surface, groove structures distributed along the fiber axis can be observed. These grooves provide surface roughness, which helps to improve the mechanical interlocking between the fiber and the composite matrix, thereby significantly enhancing the interfacial bonding strength. Figure (b) is an SEM image of the cross-section of the graphite fiber. The cross-section is a regular circle with a dense internal structure, and no obvious defects such as cracks or pores were observed, indicating that the fiber has high structural integrity and excellent mechanical properties. Combining the characteristics of these two images, it can be inferred that graphite fiber, due to its surface grooves and dense cross-sectional structure, can exhibit superior performance in composite materials. The surface grooves not only improve the interfacial bonding strength but also enhance the shear resistance of the material, while the dense cross-section ensures the high strength and high modulus of the fiber itself. This type of graphite fiber has broad application potential in high-performance composite materials, and is particularly suitable for use in fields requiring high strength and high reliability.

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber, characterized in that, Includes the following steps: Dissolve the gel monomer, water-soluble sugar, and cross-linking agent in water to obtain solution A; Add spinning aid, initiator and catalyst to solution A to prepare spinning solution; Prepare a solution identical to solution A, and add an ion gelation aid as a coagulation bath; A solution omitting the gel monomer, crosslinking agent, and spinning aid in the spinning solution is used as the water bath solution; Carbon fiber precursor is obtained by wet spinning using the spinning solution, the coagulation bath, and the water bath solution. The carbon fiber precursor is first pre-carbonized to obtain pre-carbonized fiber; then the pre-carbonized fiber is carbonized to obtain the green, environmentally friendly, low-cost sugar-based high-strength carbon fiber. The gel monomer includes one or more of acrylic acid, methacrylic acid, acrylamide, and N-isopropylacrylamide; The water-soluble sugars include one or more of glucose, fructose, galactose, maltose, sucrose, lactose, and fructooligosaccharides. The crosslinking agent includes one or more of ethylene glycol diacrylate, sodium acrylate, N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, diacrylamide ethylenediamine, and N,N'-ethylenebisacrylamide; The spinning aids include one or more of sodium alginate, sodium polyacrylate and sodium carboxymethyl cellulose; The initiator includes one or more of azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and hydrogen peroxide; The catalyst includes one or more of sodium sulfite, triethanolamine, and tetramethylethylenediamine; The ion gel additives include calcium chloride and / or calcium acetate.

2. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, The mass ratio of gel monomer, water-soluble sugar, cross-linking agent and water in solution A is 1~30:10~80:0.05~2:

100.

3. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, In the spinning solution, the spinning aid, initiator and catalyst are added in the form of aqueous solutions, wherein the concentration of the aqueous solution of the spinning aid is 1~10 wt.%, the concentration of the aqueous solution of the initiator is 0.5~20 wt.%, and the concentration of the aqueous solution of the catalyst is 0.5~20 wt.%.

4. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, In the spinning solution, the mass ratio of the spinning aid to water in solution A is 0.5~10:

100.

5. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, The ion gelation aid accounts for 1-20% of the mass of the coagulation bath.

6. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, During the wet spinning process, the process parameters are as follows: inner diameter of spinning needle 30~200μm, spinning speed 50~2000μL / min, drawing machine speed 1~20m / min, drying temperature 50~300℃, and drying time 1~30min.

7. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, The pre-carbonization is carried out by gradient heating, with the maximum temperature not exceeding 350°C.

8. The method for preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to claim 1, characterized in that, The carbonization is carried out under oxygen-free conditions, with direct or gradient heating to 800~2000℃ at a heating rate of 1~20℃ / min, and the holding time for each gradient is 0.5~6h.

9. A green, environmentally friendly, low-cost sugar-based high-strength carbon fiber prepared by the method of preparing green, environmentally friendly, low-cost sugar-based high-strength carbon fiber according to any one of claims 1 to 8.

10. A graphite fiber, characterized in that, The pre-carbonized fiber or green, low-cost sugar-based high-strength carbon fiber prepared by the preparation method according to any one of claims 1 to 8 is obtained by graphitization.

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