A waste fiber-based three-dimensional flexible functional carbon felt and a preparation method thereof

Abstract

The application belongs to the technical field of carbon material preparation, and particularly relates to a waste fiber-based three-dimensional flexible functional carbon felt and a preparation method thereof. The carbon felt is made of waste textiles through steps of opening, mixing, three-dimensional needling, pre-oxidation, carbonization and surface modification. The application discloses that waste textiles are used as raw materials, a micron-level fiber network is constructed through three-dimensional needling technology, high-entropy alloy nanoparticles are synthesized on the surface of the carbonized fiber, and carbon nanotubes are grown, so that a unique multi-scale micro-nano interpenetrating network structure is formed. The structure not only improves the specific surface area and conductivity of the material, but also endows the material with excellent flexibility and mechanical properties. In addition, the preparation method realizes high-value utilization of the waste textiles, and has significant environmental and economic benefits. The material has wide application prospects in the fields of flexible electrodes, energy storage, electrochemical sensing and the like.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a waste fiber-based three-dimensional flexible functional carbon felt and its preparation method. Background Technology

[0002] In my country, up to 20 million tons of waste textiles are generated annually, a staggering figure that hides serious environmental problems. Currently, most waste textiles are disposed of through landfill or incineration. Landfilling not only occupies vast amounts of land resources, but waste textiles also fail to degrade quickly in the natural environment, leading to long-term pollution of soil and groundwater. Incineration, on the other hand, produces large amounts of harmful gases, such as dioxins, posing a serious threat to air quality and human health. Therefore, how to achieve efficient recycling of waste textiles and reduce their negative environmental impact has become a crucial issue that urgently needs to be addressed. At the same time, waste textiles are not worthless garbage but contain enormous resource potential. Through reasonable recycling technologies, not only can environmental pollution be reduced, but new economic value can also be created, achieving resource recycling and sustainable development.

[0003] In the field of waste textile recycling, the traditional dissolution and respinning method has been widely used. However, this method faces many challenges in practical application. Waste textiles come from a wide variety of sources and are diverse in type, with significant differences in chemical structure and physical properties among different types of fibers. Traditional dissolution and respinning methods often struggle to effectively process mixtures of different types of fibers, resulting in low recycling efficiency, unstable product quality, and difficulty in meeting the needs of large-scale industrial production.

[0004] To overcome the limitations of traditional methods, needle punching and carbonization, two key process steps, have gradually gained attention. Needle punching technology can effectively combine various waste fibers to form fiber mats with certain strength and flexibility. This not only improves the utilization rate of waste fibers but also provides a good foundation for subsequent carbonization. Through carbonization, various organic fibers can be transformed into carbon materials with excellent properties. However, traditional methods of directly carbonizing fiber fabrics suffer from low carbonization yield, high brittleness and poor flexibility of the carbonized material, and small specific surface area of ​​the carbonization products, affecting their application in flexible electronics, adsorption, energy storage, and other fields. These problems severely restrict the application scope and large-scale production of carbonized waste textile materials.

[0005] In conclusion, although needle punching and carbonization technologies have certain advantages in the recycling of waste fibers, there are still many problems that need to be solved. Summary of the Invention

[0006] To achieve large-scale, high-efficiency utilization of waste fibers, developing a novel method that effectively combines needle punching, carbonization, and surface post-treatment technologies to prepare waste fiber-based three-dimensional flexible functional carbon felts with superior performance is of significant scientific and practical value. The purpose of this invention is to provide a method for preparing waste fiber-based three-dimensional flexible functional carbon felts. This method not only improves the recycling rate of waste fibers and reduces production costs but also expands the application fields of carbonized materials, promoting the sustainable development of the waste textile recycling industry. This method can significantly improve the utilization rate of waste fibers, enhance the carbonization efficiency and flexibility of fiber felts, while simultaneously achieving a larger specific surface area.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, a method for preparing a waste fiber-based three-dimensional flexible functional carbon felt is provided, the method comprising the following steps:

[0009] S1. Opening and mixing of waste textiles: Different types of waste textiles are classified, impurities are removed, the fabric is opened, and then mixed in proportion.

[0010] S2, Three-dimensional needle punching: Multi-component fiber felt is prepared by using three-dimensional needle punching technology to mix waste fibers;

[0011] S3. Pre-oxidation treatment: The multi-component fiber felt is subjected to pre-oxidation treatment;

[0012] S4. Carbonization treatment: The pre-oxidized fiber felt is carbonized in an inert atmosphere;

[0013] S5. Surface modification: The carbonized carbon felt is subjected to thermal flash evaporation and chemical vapor deposition to synthesize high-entropy alloy nanoparticles and grown one-dimensional carbon nanotubes on the fiber surface of the carbon felt, thus obtaining the three-dimensional flexible carbon felt.

[0014] Furthermore, the waste textiles in S1 are waste cotton fiber, waste acrylic fiber and chopped carbon fiber, and the mass ratio is waste cotton fiber: waste acrylic fiber: chopped carbon fiber = (3-4): (3-5): (2-3).

[0015] Furthermore, the three-dimensional needle punching technical parameters in S2 include a needle punching density of 100-150 needles / cm²; a needle punching frequency of 600-900 times / min; a needle punching depth of 70%-80% of the fiber felt thickness; the needle punching process is repeated 3-5 times, and the fiber felt is rotated 36°-90° after each needle punch.

[0016] Further, the pre-oxidation process in S3 includes: pre-oxidizing the fiber felt at 200-230℃ for 2-3.5 hours; heating rate of 0.8-1.2℃ / min; turning the fiber felt over every 30-50 minutes; and cooling to room temperature at a rate of 0.8-1.2℃ / min after pre-oxidation.

[0017] Furthermore, in S4, the carbonization temperature is 600-1200℃, the heating rate is 1-10℃ / min, and the holding time is 1-4 hours. During the heating process, the temperature is held at 300℃ and 500℃ for 30 minutes each. After carbonization, the temperature is naturally cooled to room temperature under an inert atmosphere.

[0018] Furthermore, the carbonization process in S4 is carried out in a tube furnace or a box furnace, with a slight positive pressure maintained inside the furnace and a gas flow rate of 50-200 mL / min / g fiber.

[0019] Furthermore, in S5, the thermal flash temperature is 1000-3500K, the chemical vapor deposition temperature is 600-900℃, the carbon source is one or more of acetylene, methane, carbon monoxide or ethylene, and the processing time is 15-60 minutes.

[0020] Furthermore, the high-entropy alloy nanoparticles in S5 contain at least three transition metal elements: Pt, Ni, Fe, Pd, Co, Cu, and Au, which are used to catalyze the growth of carbon nanotubes.

[0021] Furthermore, during the S5 chemical vapor deposition process, the carbon source gas is decomposed on the surface of the high-entropy alloy nanoparticles, and carbon nanotubes are grown in situ to form a three-dimensional micro-nano interpenetrating network.

[0022] Secondly, the present invention also provides a waste fiber-based three-dimensional flexible functional carbon felt, which is prepared according to the preparation method described above.

[0023] Technical effect

[0024] Compared with existing technologies, the method for preparing a waste fiber-based three-dimensional flexible functional carbon felt provided by the present invention has the following technical advantages:

[0025] (1) This invention efficiently recycles waste textiles: through opening, mixing and three-dimensional needle punching technology, a variety of waste textiles such as waste cotton, acrylic fiber and carbon fiber are transformed into high-value-added carbon materials, which significantly improves resource utilization and reduces environmental pollution.

[0026] (2) The method provided by this invention uses a three-dimensional needle punching process with 100-150 needles / cm², multi-angle rotation to enhance fiber interweaving, thereby improving the mechanical strength and flexibility of the carbon felt, with a minimum bending radius of 3.8-4.5 mm. Gradient pre-oxidation and carbonization reduce fiber pyrolysis defects, and the carbonization yield reaches 21%-27%, which is superior to the traditional direct carbonization method. Functionalized surface modification: High-entropy alloy nanoparticles (multi-component Pt / Ni / Fe, etc.) efficiently catalyze the cracking of carbon sources, and in-situ grow carbon nanotubes (diameter 4-16 nm) to form a three-dimensional conductive network. The specific surface area is significantly improved, with a specific surface area of ​​210-370 cm² / g, making it suitable for flexible electronics, energy storage, and other fields.

[0027] (3) The method and process provided by the present invention have strong universality and can be adapted to various waste fibers such as cotton, polyester, and wool. The parameters are flexible and controllable, making it suitable for large-scale production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the waste fiber-based three-dimensional needle punching preparation method of the present invention.

[0029] Figure 2 Scanning electron microscope image of the surface of the waste fiber-based three-dimensional flexible functional carbon felt prepared in Example 1 after carbonization treatment.

[0030] Figure 3 Scanning electron microscope image of the cross section of the fiber felt in the thickness direction after carbonization treatment of the waste fiber-based three-dimensional flexible functional carbon felt prepared in Example 1.

[0031] Figure 4 The Raman spectrum of the waste fiber-based three-dimensional flexible functional carbon felt prepared in Example 1.

[0032] Figure 5 Nitrogen adsorption / desorption curves of the waste fiber-based three-dimensional flexible functional carbon felt prepared in Example 1.

[0033] Figure 6 Scanning electron microscope image of the surface morphology of the waste fiber-based three-dimensional flexible functional carbon felt carbon fiber prepared in Example 1.

[0034] Reference numerals: 1. Waste mixed fibers; 2. Pressure roller system; 3. Needle device. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0037] like Figure 1 The diagram shown is a schematic representation of the waste fiber-based three-dimensional needle-punching preparation method of the present invention. 1 represents waste mixed fiber, 2 represents the pressure roller system, and 3 represents the needle-punching device.

[0038] Waste mixed fiber 1 is the core raw material of the entire preparation process. Waste textiles can be one or more of the following: waste cotton fabrics, waste acrylic fabrics, waste polyester fabrics, waste wool fabrics, waste lyocell fiber fabrics, waste carbon fiber fabrics, and other waste fiber fabrics. These waste textiles can come from various sources, such as scraps from garment factories, recycled old clothes, and waste industrial textiles.

[0039] In one embodiment, the waste blended fiber 1 is composed of waste wool fiber, waste lyocell fiber, and chopped carbon fiber mixed in a precise mass ratio of 3:4:3. This multi-component fiber design fully utilizes the advantages of each fiber: wool fiber provides good flexibility and elasticity, lyocell fiber contributes excellent mechanical strength, and chopped carbon fiber provides the foundation for the electrical conductivity of the final product. In the process flow, the blended fiber is first thoroughly opened by an opening machine to eliminate entanglement and agglomeration between fibers, resulting in a fluffy and uniform state. The opening process employs mechanical opening methods, such as carding machines and dispersing machines. Specifically, a carding machine can be used for initial opening, followed by an airflow dispersing machine for further fiber separation. The mixing ratio is adjusted according to the performance requirements of the final product; for example, the mixing ratio of various fibers can be determined based on the required conductivity, adsorption, flexibility, and other properties. Subsequently, a vibratory web-laying machine forms a continuous and uniform fiber web layer, creating ideal initial conditions for subsequent three-dimensional needle punching. This pretreatment ensures that the fibers can move and rearrange freely during needle punching, ultimately forming a three-dimensional interwoven network structure.

[0040] The pressure roller system 2 plays a crucial auxiliary support role in the three-dimensional needle punching process, adjusting the thickness and density of the fiber web through precise pressure control. This system not only provides stable reaction force support for the vertical piercing of the needles, but more importantly, it prevents unnecessary displacement and deformation of the fiber web during needle punching by applying appropriate pressure. The working mechanism of the pressure roller is based on precise control of mechanical pressure, which can compact the loose mixed fiber web to a preset thickness range. This compression provides a benchmark reference for accurate control of the needle depth, ensuring that each needle punch achieves the design requirement of 80% of the fiber felt thickness. Simultaneously, the stability of the pressure roller system directly affects the consistency of needle punching quality, laying the foundation for forming a uniform three-dimensional fiber structure.

[0041] The needle device 3 is the core component for realizing the three-dimensional needle punching process. It uses a specially designed needle with a barbed structure to effectively grasp and drag fibers to achieve three-dimensional interweaving. The essence of this device's design lies in reorganizing the originally planar fibers into a three-dimensional network structure through high-frequency, high-density mechanical puncture actions, thereby significantly improving the overall performance of the fiber mat.

[0042] It should be noted that two units of measurement can be used to describe gas flow rate:

[0043] (1) Unit of measurement for “mL / min / g fiber”:

[0044] This is a composite unit representing the gas volumetric flow rate per gram of fiber, commonly used to express the relative flow rate relationship between gas and solid materials. In materials preparation processes, this expression accurately describes the ratio of gas flow rate to sample mass, ensuring process reproducibility and scalability.

[0045] (2) "sccm" unit of measurement:

[0046] sccm stands for "standard cubic centimeters per minute" (cm) 3 / min (mL / min) is a fully compliant unit for gas flow rate. Because the amount of gas used is related to the sample mass, the entire text uses "mL / min / g fiber" as the unit of measurement.

[0047] The growth of carbon nanotubes refers to a chemical vapor deposition process in which, under certain temperature conditions (e.g., 500-1500°C), a catalyst is used as the active center, and carbon source gas (such as acetylene, methane, etc.) is catalytically cracked and carbon atoms are rearranged in an orderly manner to form a one-dimensional carbon nanotube structure with a specific diameter and length in situ on the substrate surface.

[0048] Example 1

[0049] This embodiment involves mixing waste cotton fiber, waste acrylic fiber, and chopped carbon fiber in a mass ratio of 4:4:2 to prepare a carbon fiber-based three-dimensional flexible functional carbon felt. The specific preparation steps of the waste fiber-based three-dimensional needle-punched fabrication method provided by this invention are as follows:

[0050] Step 1: Mix waste cotton fiber, waste acrylic fiber, and chopped carbon fiber in a mass ratio of 4:4:2, and prepare multi-component fiber mat using a three-dimensional needle punching process with a needle punching density of 100 needles / cm. 2In practice, waste cotton and acrylic fibers are first fully opened using a carding machine, and then fed into an airflow mixer along with chopped carbon fibers for uniform mixing. The mixed fibers are then evenly laid out using a web-laying machine to form an initial fiber web. A reciprocating needle punch is used for needle punching at a frequency of 600 times / min and a depth of 70% of the fiber felt thickness. The needle punching process is repeated three times, with the fiber felt rotated 90 degrees after each punch to ensure thorough interweaving and uniform distribution of the fibers.

[0051] Step 2: Pre-oxidize the fiber felt at 220℃ for 2 hours. Pre-oxidation is carried out in an oven with a forced ventilation system, with a heating rate controlled at 1℃ / min. During pre-oxidation, the fiber felt is turned over every 30 minutes to ensure uniform oxidation. After pre-oxidation, it is cooled to room temperature at a rate of 1℃ / min.

[0052] Step 3: The pre-oxidized fiber felt is heated to 800℃ at a rate of 5℃ / min under a nitrogen atmosphere and held at this temperature for 2 hours for carbonization. The carbonization process is carried out in a tube furnace with a nitrogen flow rate of 100 mL / min / g fiber. During the heating process, the temperature is held at 300℃ and 500℃ for 30 minutes respectively to fully remove volatiles. After carbonization, the fiber felt is allowed to cool naturally to room temperature under a nitrogen atmosphere.

[0053] Step 4: Prepare a mixed solution containing PtCl4, NiCl2, and FeCl3, with a total metal ion concentration of 0.05 mol / L and a molar ratio of 1:1:1 for each metal ion. Spray the solution evenly onto the carbonized carbon felt and vacuum dry at 65°C for 4 hours. Under an argon atmosphere, subject the carbon felt with the supported precursor to rapid thermal shock treatment at approximately 1800 K for 50 ms, with a heating / cooling rate of approximately 10⁻⁶. 5 K / s. Subsequently, acetylene gas (flow rate 50 mL / min / g fiber) and hydrogen gas (flow rate 100 mL / min / g fiber) were introduced at 800℃ to grow carbon nanotubes for 30 minutes. The resulting waste fiber-based three-dimensional flexible functional carbon felt was marked as No. 1 waste fiber-based three-dimensional flexible functional carbon felt.

[0054] The scanning electron microscope (SEM) results of waste fiber-based three-dimensional flexible functional carbon felt #1 are as follows: Figure 2 As shown, from Figure 2 Surface SEM images reveal that the carbonized fiber felt exhibits a typical interwoven fiber network structure. The fiber diameter is relatively uniform, ranging from approximately 10 to 20 micrometers, consistent with the characteristics of a mixture of waste cotton fibers, waste acrylic fibers, and chopped carbon fibers. The relatively smooth fiber surface indicates that the gradient pre-oxidation and carbonization processes effectively avoided surface defects caused by rapid pyrolysis. Figure 4The fibers are well interwoven, exhibiting a three-dimensional network structure. This is due to the synergistic effect of the high-density needle punching process of 100 needles / cm² and multi-angle rotating needle punching (90° rotation each time, repeated 3 times), which ensures the full interweaving and uniform distribution of the fibers.

[0055] SEM cross-sectional analysis of waste fiber-based three-dimensional flexible functional carbon felt #1 Figure 3 As shown, Figure 3 The cross-sectional SEM images clearly show the thickness-direction structure of the carbon felt. A good distribution of fibers in the thickness direction is observed, with no obvious delamination. Abundant pore structures are formed between the fiber bundles, providing excellent mass transfer channels for subsequent surface modification and carbon nanotube growth. The cross-section shows that the fiber orientation in the thickness direction is relatively random, which is beneficial for maintaining good mechanical properties and flexibility in all directions. This preparation process successfully achieves the high-value utilization of waste fibers, producing a carbon felt with a complete structure and abundant pores, creating ideal matrix conditions for subsequent functional modifications (high-entropy alloy catalyst loading and carbon nanotube growth).

[0056] Micro Raman spectroscopy test results are as follows Figure 4 As shown.

[0057] The nitrogen adsorption / desorption curve of waste fiber-based three-dimensional flexible functional carbon felt No. 1 was tested using a specific surface area analyzer, as shown in the figure below. Figure 5 As shown, the surface morphology of the #1 waste fiber-based three-dimensional flexible functional carbon felt fiber is as follows: Figure 6 As shown. Based on Figure 5 The nitrogen adsorption-desorption isotherms show typical type IV isotherm characteristics, indicating a mesoporous structure. A distinct hysteresis loop appears in both the adsorption and desorption curves within the relative pressure range of 0.4-0.9, a typical characteristic of mesoporous materials, indicating a rich mesoporous channel structure within the material. The shape of the hysteresis loop is close to type H3, suggesting a slit-like pore structure, consistent with the three-dimensional network structure formed by the in-situ growth of carbon nanotubes on a carbon felt matrix. A sharp increase in adsorption capacity in the high relative pressure region (P / P0>0.9) indicates the presence of a macroporous structure, possibly originating from the voids between fiber bundles. Test results show that the specific surface area of ​​this material is 237 cm² / g. The high-entropy alloy nanoparticles (Pt / Ni / Fe, etc.) in the functionalized surface modification act as catalysts, effectively promoting the decomposition of the carbon source and the in-situ growth of carbon nanotubes. Figure 6 The resulting three-dimensional conductive network not only significantly increases the specific surface area but also maintains the material's flexibility, laying the foundation for flexible electronics and energy storage applications. This fabrication process successfully achieves synergistic optimization of structure and performance, significantly increasing the specific surface area while maintaining the flexibility of the carbon felt, providing an excellent material solution for related application fields.

[0058] Example 2

[0059] This embodiment involves mixing waste cotton fiber, waste acrylic fiber, and chopped carbon fiber in a mass ratio of 3:5:2 to prepare a three-dimensional flexible functional carbon felt based on waste fiber. The specific preparation steps are as follows:

[0060] Step 1: Waste cotton fiber, waste polyester fiber, and chopped carbon fiber are mixed in a mass ratio of 3:5:2, and a multi-component fiber mat is prepared using a three-dimensional needle punching process with a needle punching density of 120 needles / cm. 2 First, waste cotton and polyester fibers are opened using a multi-channel carding machine, and then fed together with chopped carbon fibers into a two-roll mixer for mixing. The mixed fibers are then passed through a cross-laying machine to form a uniform fiber web. A rotary needle punch is used for needle punching at a frequency of 800 times / min, with a needle punching depth of 75% of the fiber mat thickness. The needle punching process is repeated four times, with the fiber mat rotated 45 degrees after each punch.

[0061] Step 2: Pre-oxidize the fiber felt at 200℃ for 3 hours. Pre-oxidation is carried out in a pre-oxidation furnace, with a heating rate controlled at 0.8℃ / min. During pre-oxidation, the fiber felt is turned over every 45 minutes. After pre-oxidation, it is cooled to room temperature at a rate of 0.8℃ / min.

[0062] Step 3: The pre-oxidized fiber felt is heated to 750℃ at a rate of 3℃ / min under an argon atmosphere and held at this temperature for 3 hours for carbonization. The carbonization process is carried out in a box furnace with an argon flow rate of 150 mL / min / g fiber. During the heating process, the temperature is held at 350℃ and 550℃ for 45 minutes respectively. After carbonization, it is cooled to room temperature under an argon atmosphere at a rate of 2℃ / min.

[0063] Step 4: Prepare a mixed solution containing PdCl2, CoC2, NiCl2, and CuCl2, with a total metal ion concentration of 0.08 mol / L and a molar ratio of 1:1:1:1 for each metal ion. Spray the solution evenly onto the carbonized carbon felt and vacuum dry at 68°C for 4.5 hours. Then, perform rapid thermal shock treatment under argon atmosphere, reaching a temperature of approximately 1900 K for 52 ms, with a heating / cooling rate of approximately 10⁻⁶. 5 K / s. Subsequently, methane gas (flow rate 80 mL / min / g fiber) and hydrogen gas (flow rate 150 mL / min / g fiber) were introduced at 750℃ to grow carbon nanotubes for 45 minutes. The resulting waste fiber-based three-dimensional flexible functional carbon felt was labeled as No. 2 waste fiber-based three-dimensional flexible functional carbon felt.

[0064] Example 3

[0065] This embodiment involves mixing waste cotton fiber, waste acrylic fiber, and chopped carbon fiber in a mass ratio of 3:4:3 to prepare a three-dimensional flexible functional carbon felt based on waste fiber. The specific preparation steps are as follows:

[0066] Step 1: Waste wool fiber, waste lyocell fiber, and chopped carbon fiber are mixed in a mass ratio of 3:4:3, and a multi-component fiber mat is prepared using a three-dimensional needle punching process with a needle punching density of 150 needles / cm. 2 First, waste wool and waste lyocell fibers are thoroughly opened using an opening machine, and then fed together with chopped carbon fibers into a three-dimensional mixer for uniform mixing. The mixed fibers are then passed through a vibratory web-laying machine to form a uniform fiber web. A composite needle punching machine is used for needle punching at a frequency of 900 times / min, with a needle punching depth of 80% of the fiber felt thickness. The needle punching process is repeated 5 times, and after each needle punch, the fiber felt is rotated 36 degrees to ensure sufficient interweaving and uniform distribution of the fibers.

[0067] Step 2: Pre-oxidize the fiber felt at 230℃ for 2.5 hours. Pre-oxidation is carried out in a pre-oxidation furnace with a temperature gradient, and the heating rate is controlled at 1.2℃ / min. During the pre-oxidation process, the fiber felt is turned over every 40 minutes to ensure uniform oxidation. After pre-oxidation, the temperature is reduced to room temperature at a rate of 1℃ / min.

[0068] Step 3: The pre-oxidized fiber felt is heated to 850℃ at a rate of 4℃ / min under a helium atmosphere and held at this temperature for 2.5 hours for carbonization. The carbonization process is carried out in a vertical furnace with a helium flow rate of 120 mL / min / g fiber. During the heating process, the temperature is held at 400℃ and 600℃ for 40 minutes respectively to fully remove volatiles. After carbonization, it is cooled to room temperature under a helium atmosphere at a rate of 3℃ / min.

[0069] Step 4, Surface Modification: Prepare a mixed solution containing PtCl4, PdCl2, CoCl2, NiCl2, FeCl3, and CuCl2, with a total metal ion concentration of 0.1 mol / L and a molar ratio of 1:1:1:1:1:1. Spray the solution uniformly onto the carbonized carbon felt and vacuum dry at 70°C for 5 hours. Then, perform rapid thermal shock treatment under argon atmosphere, reaching approximately 2000K for 55 ms, with a heating / cooling rate of approximately 10⁻⁶. 5 K / s. Subsequently, ethylene gas (flow rate 60 mL / min / g fiber) and hydrogen gas (flow rate 120 mL / min / g fiber) were introduced at 850℃ to grow carbon nanotubes for 45 minutes. The resulting waste fiber-based three-dimensional flexible functional carbon felt was labeled as No. 3 waste fiber-based three-dimensional flexible functional carbon felt.

[0070] Example 4

[0071] This embodiment involves mixing waste cotton fiber, waste acrylic fiber, and chopped carbon fiber in a mass ratio of 4:3:3 to prepare a three-dimensional flexible functional carbon felt based on waste fiber. The specific preparation steps are as follows:

[0072] Step 1: Waste polyester fiber, waste acrylic fiber, and chopped carbon fiber are mixed in a mass ratio of 4:3:3, and a multi-component fiber mat is prepared using a three-dimensional needle punching process with a needle punching density of 130 needles / cm. 2 First, waste polyester and acrylic fibers are opened using an airflow opening machine, and then fed together with chopped carbon fibers into a high-speed mixer for thorough mixing. The mixed fibers are then carded to form a uniform fiber web. A reciprocating needle punch is used for needle punching at a frequency of 750 times / min, with a needle punching depth of 72% of the fiber mat thickness. The needle punching process is repeated four times, with the fiber mat rotated 45 degrees after each punch.

[0073] Step 2: Pre-oxidize the fiber felt at 210℃ for 3.5 hours. Pre-oxidation is carried out in a pre-oxidation furnace equipped with a humidity control system, with a heating rate controlled at 0.9℃ / min and a relative humidity maintained at 60%. During the pre-oxidation process, the fiber felt is turned over every 50 minutes. After pre-oxidation, it is cooled to room temperature at a rate of 0.9℃ / min.

[0074] Step 3: The pre-oxidized fiber felt is heated to 900℃ at a heating rate of 3.5℃ / min under a mixed atmosphere of nitrogen and argon (volume ratio 7:3) and held at this temperature for 3 hours for carbonization. The carbonization process is carried out in a multi-zone tube furnace, with the total flow rate of the mixed gas set at 180 mL / min / g fiber. During the heating process, the temperature is held at 450℃ and 650℃ for 35 minutes respectively. After carbonization, the fiber felt is cooled to room temperature at a rate of 2.5℃ / min under the mixed atmosphere.

[0075] Step 4, Surface Modification: Prepare a mixed solution containing PtCl4, PdCl2, CoCl2, NiCl2, FeCl3, CuCl2, and AuCl3, with a total metal ion concentration of 0.12 mol / L and a molar ratio of 1:1:1:1:1:1:1. Spray the solution evenly onto the carbonized carbon felt and vacuum dry at 72°C for 5.5 hours. Then, perform rapid thermal shock treatment under argon atmosphere, reaching approximately 2100 K for 58 ms, with a heating / cooling rate of approximately 10⁻⁶. 5K / s. Subsequently, acetylene (40 mL / min / g fiber) and methane (40 mL / min / g fiber) gases were alternately introduced at 900℃, with a switching cycle of 5 minutes, while hydrogen (130 mL / min / g fiber) was introduced simultaneously, for a total growth time of 50 minutes. The resulting waste fiber-based three-dimensional flexible functional carbon felt was then obtained, labeled as #4 waste fiber-based three-dimensional flexible functional carbon felt.

[0076] Test Example 1

[0077] Using the waste fiber-based three-dimensional flexible functional carbon felts (referred to as 1#-4# carbon felts) prepared in Examples 1-4 as test objects, the carbonization rate of each test group was calculated. The specific surface area was calculated using the nitrogen adsorption-desorption test (BET method). The minimum bending radius of each test group while maintaining structural integrity was measured using a mechanical bending tester. Tensile tests were performed using a universal testing machine, and stress-strain curves were recorded to calculate the modulus and strength. The graphitization degree of the carbon materials was analyzed using micro Raman spectroscopy (532nm laser), and the intensity ratio of the D peak (defect carbon) to the G peak (graphite carbon) was calculated. The lattice structure and distribution of high-entropy alloy nanoparticles were observed using transmission electron microscopy (TEM), and the morphology of carbon nanotubes and fiber surface morphology were observed using scanning electron microscopy (SEM). The test results for each test group are shown in Table 1.

[0078]

[0079] Table 1 shows that the carbonization yield increases with the increase of the types of high-entropy alloying elements. The No. 4 waste fiber-based three-dimensional flexible functional carbon felt exhibits the best performance due to its catalytic carbon source cracking and high carbon fiber ratio. The No. 4 waste fiber-based three-dimensional flexible functional carbon felt also has the highest specific surface area, at 370 cm². 2 / g, thanks to alternating CVD carbon sources, high carbon nanotube density, and large-diameter alloy particles; in terms of mechanical properties, the No. 4 waste fiber-based three-dimensional flexible functional carbon felt exhibits the best flexibility and strength, attributed to needle-punching density, carbon nanotube network, and high-entropy alloy-reinforced interface; the Raman IG / ID ratio indicates that the No. 4 waste fiber-based three-dimensional flexible functional carbon felt has the highest degree of graphitization; the microstructure shows increased high-entropy alloy particle size and uniform distribution, with carbon nanotubes forming a three-dimensional conductive network. In summary, the No. 4 waste fiber-based three-dimensional flexible functional carbon felt exhibits the best performance and is suitable for demanding applications, while the No. 3 carbon felt balances cost and performance and is suitable for cost-sensitive applications.

[0080] The operating parameters of the needle device 3 of this invention have been carefully optimized: a needle-piercing frequency of 900 times / min ensures processing efficiency, and 150 needles / cm 2The needle-punching density ensures sufficient interweaving between fibers, while the 80% needle-punching depth guarantees the interweaving effect while avoiding structural damage caused by excessive puncture. Of particular note is the multi-angle processing strategy of rotating the fiber mat 36° after each needle-punching and repeating it 5 times, which achieves all-round fiber entanglement and ultimately forms a three-dimensional flexible structure with excellent mechanical properties.

[0081] This invention successfully utilizes waste textiles as raw materials to prepare flexible carbon felt with a three-dimensional structure, solving the dual problems of recycling waste textiles and preparing high-performance flexible carbon materials. Compared with two-dimensional planar carbon cloth obtained by traditional fabric carbonization, the carbon felt prepared by the three-dimensional needle-punching technology of this invention has significant structural advantages. The three-dimensional needle-punched felt forms a network structure of interwoven fibers. This three-dimensional structure not only increases the specific surface area of ​​the material but also enhances the connection between fibers, thereby improving the mechanical properties and conductivity of the material. At the same time, the three-dimensional structure is also conducive to electrolyte permeation and ion transport, which is particularly important for electrochemical applications. Furthermore, the three-dimensional needle-punching technology of this invention gives the final carbon felt better flexibility and compressibility, making the material promising for applications in flexible electronics, wearable devices, and other fields.

[0082] The results from Examples 1-4 show that:

[0083] The carbon felt prepared by this method has a high specific surface area (210-370 cm²). 2 With its good flexibility (minimum bending radius 4.0-4.8 mm) and moderate mechanical properties (Young's modulus 11-14.5 MPa, tensile strength 5.2-6.5 kPa), it is suitable for use as a flexible electrode material.

[0084] The properties of the final carbon felt can be effectively controlled by adjusting the type and proportion of waste fibers, needle punching density, pre-oxidation and carbonization conditions, and carbon nanotube growth parameters. In particular, the heat treatment and special atmosphere conditions used in Examples 3 and 4 significantly improved the properties of the carbon felt.

[0085] The Raman spectral IG / ID ratios (0.9–1.6) indicate that the carbon nanotubes grown on the surface of the carbon felt prepared by this method exhibit a high degree of graphitization and structural integrity, which is of great significance for improving the conductivity and stability of the material.

[0086] The three-dimensional carbon felt prepared by this invention possesses a unique multi-scale micro-nano interpenetrating network structure, significantly different from the two-dimensional planar structure obtained by direct carbonization of waste textiles and the two-dimensional fiber membrane structure obtained by electrospinning and re-carbonization. This structure integrates a micron-scale three-dimensional needle-punched fiber network and a nano-scale high-entropy alloy particle and carbon nanotube network, forming a unique three-dimensional micro-nano interpenetrating network. This multi-scale structure not only ensures the overall mechanical properties of the material but also provides abundant active sites and transport channels, which is conducive to the rapid transport of ions and electrons, endowing the material with excellent comprehensive properties, including high specific surface area, good mechanical strength, excellent flexibility, high electrical conductivity, and outstanding electrochemical performance.

[0087] This invention is not limited to the specific embodiments described above. Those skilled in the art can make many changes and modifications based on the technical solutions of this invention. As long as they do not depart from the spirit of this invention, they should all be covered within the protection scope of this invention. For example, the type and proportion of waste fibers can be adjusted as needed, the needle punching density can be changed, the process parameters for pre-oxidation and carbonization can be adjusted, or other types of high-entropy alloys and carbon nanomaterials can be selected for surface modification, etc.

[0088] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The substitutions may be replacements of some structures, devices, or method steps, or they may be complete technical solutions. Equivalent substitutions or modifications made to the technical solutions and inventive concepts of the present invention should all be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a waste fiber-based three-dimensional flexible functional carbon felt, characterized in that... The preparation method includes the following steps: S1. Opening and mixing of waste textiles: Different types of waste textiles are classified, impurities are removed, the fabric is opened, and then mixed in proportion. S2, Three-dimensional needle punching: Multi-component fiber felt is prepared by using three-dimensional needle punching technology to mix waste fibers; S3. Pre-oxidation treatment: The multi-component fiber felt is subjected to pre-oxidation treatment; S4. Carbonization treatment: The pre-oxidized fiber felt is carbonized in an inert atmosphere; S5. Surface Finishing: The mixed solution is uniformly sprayed onto the carbonized carbon felt. The carbonized carbon felt is then subjected to thermal flash evaporation and chemical vapor deposition treatment. The thermal flash evaporation temperature is 1000-3500K, the duration is 50ms, 52ms, 55ms or 58ms, and the heating / cooling rate is 10. 5 K / s, forming high-entropy alloy nanoparticles; then, under conditions of 500-1500°C, using one or more of acetylene, methane, carbon monoxide or ethylene as carbon source gases, through catalytic cracking and ordered rearrangement of carbon atoms, a one-dimensional carbon nanotube structure is grown in situ on the substrate surface, forming a three-dimensional micro-nano interpenetrating network of needle-punched fiber felt-carbon nanotubes, thus obtaining the three-dimensional flexible carbon felt.

2. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The waste textiles in S1 are waste cotton fiber, waste acrylic fiber and chopped carbon fiber, and the mass ratio is waste cotton fiber: waste acrylic fiber: chopped carbon fiber = (3-4): (3-5): (2-3).

3. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The three-dimensional needle punching technical parameters in S2 include a needle punching density of 100-150 needles / cm²; a needle punching frequency of 600-900 times / min; a needle punching depth of 70%-80% of the fiber felt thickness; and the needle punching process is repeated 3-5 times, with the fiber felt rotated 36°-90° after each needle punch.

4. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The pre-oxidation process in S3 includes: pre-oxidizing the fiber felt at 200-230℃ for 2-3.5 hours; heating rate of 0.8-1.2℃ / min; turning the fiber felt over every 30-50 minutes; and cooling to room temperature at a rate of 0.8-1.2℃ / min after pre-oxidation.

5. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The carbonization temperature in S4 is 600-1200℃, the heating rate is 1-10℃ / min, and the holding time is 1-4 hours. During the heating process, the temperature is held at 300℃ and 500℃ for 30 minutes each. After carbonization, the temperature is naturally cooled to room temperature under an inert atmosphere.

6. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The carbonization process in S4 is carried out in a tube furnace or box furnace, with a slight positive pressure maintained inside the furnace and a gas flow rate of 50-200 mL / min / g fiber.

7. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The chemical vapor deposition process in S5 is carried out at a temperature of 600-900℃ for 15-60 minutes.

8. The method for preparing a waste fiber-based three-dimensional flexible functional carbon felt according to claim 1, characterized in that, The high-entropy alloy nanoparticles in S5 contain at least three transition metal elements: Pt, Ni, Fe, Pd, Co, Cu, and Au, which are used to catalyze the growth of carbon nanotubes.

9. A waste fiber-based three-dimensional flexible functional carbon felt, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

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