Carbon nanofibrous material and method for producing the same

Abstract

The application provides a carbon nanofiber material and a preparation method thereof. The preparation method of the carbon nanofiber material comprises the following steps: placing a carbonized material to be carbonized at the bottom of a crucible; placing the crucible in a carbonization device for carbonization treatment, so that the carbonized material to be carbonized is carbonized and carbon source gas is discharged, so that the carbon source gas reacts to generate the carbon nanofiber material under the action of high temperature and a catalyst; and the catalyst is arranged on the surface, the inside of the carbonized material to be carbonized, or the inner wall of the crucible, or a carrier located above the carbonized material to be carbonized. The application can reduce environmental protection cost and has economic and environmental benefits.

Description

Technical Field

[0001] This application relates to the field of carbon nanofiber materials technology, and more specifically, to a carbon nanofiber material and a method for preparing the same. Background Technology

[0002] Carbonization is a common process in the preparation of carbon materials, graphite products, and novel carbon-based functional materials. Carbonization typically involves heat-treating a carbon-containing precursor (the material to be carbonized) at high temperatures, causing non-carbon elements such as hydrogen, oxygen, and nitrogen in the organic components to escape as water, hydrogen gas, ammonia, or other volatile small molecules, thereby removing volatile components from the material.

[0003] The carbonization process typically generates a large amount of organic waste gas containing hydrocarbons, tar vapors, benzene compounds, etc. This organic waste gas usually needs to be treated by environmental protection equipment (such as incinerators) before being discharged, thus requiring expensive environmental protection equipment and resulting in high environmental protection costs. Summary of the Invention

[0004] This application addresses the shortcomings of existing methods by proposing a carbon nanofiber material and its preparation method, thereby solving the technical problem of high environmental costs required for the carbonization process in related technologies.

[0005] In a first aspect, embodiments of this application provide a method for preparing carbon nanofiber-like materials, comprising:

[0006] Place the material to be carbonized at the bottom of the crucible; The crucible is placed in a carbonization device for carbonization treatment, so that the material to be carbonized is carbonized and carbon source gas is discharged, and the carbon source gas reacts under high temperature and the action of a catalyst to generate carbon nanofiber material; the catalyst is disposed on the surface or inside of the material to be carbonized, or on the inner wall of the crucible, or on a carrier located above the material to be carbonized.

[0007] Optionally, the crucible is placed in a carbonization device for carbonization treatment, including: After placing the crucible in the carbonization equipment, heat it to a temperature of 550 degrees Celsius to 1400 degrees Celsius and hold it at that temperature for 1 hour to 96 hours.

[0008] Optionally, before placing the material to be carbonized at the bottom of the crucible, the method further includes: A catalyst precursor is disposed on the inner wall of the crucible or on the support; the catalyst precursor is used to be reduced to elemental metal nanoparticles during the carbonization process to obtain the catalyst; The catalyst precursor includes transition metal compounds.

[0009] Optionally, the preparation method of carbon nanofiber-like materials includes at least one of the following: The transition metal in the catalyst precursor includes at least one of iron, cobalt, nickel, and their alloys; The catalyst precursor includes at least one of the following: transition metal nitrate, transition metal chloride, transition metal sulfate, transition metal acetate, transition metal carbonate, transition metal hydroxide, transition metal phosphate, transition metal oxalate, transition metal citrate, transition metal lactate, ferrous gluconate, ferrous fumarate, ferrous succinate, potassium ferricyanide, potassium ferrocyanide, and their hydrates.

[0010] Optionally, the transition metal in the catalyst precursor may also include molybdenum.

[0011] Optionally, the catalyst precursor is in the form of nanoparticles, and the particle size range of the catalyst precursor is 1 nanometer to 500 nanometers.

[0012] Optionally, the provision of the catalyst precursor on the inner wall of the crucible or on the support includes: The mixture of the catalyst precursor and the volatile solvent is coated onto the inner wall of the crucible or the support. The mixture coated on the inner wall of the crucible or the support is dried to obtain a dried catalyst precursor.

[0013] Optionally, the provision of the catalyst precursor on the inner wall of the crucible or on the support includes: Prepare a mixture of the catalyst precursor and a volatile solvent; The carrier nanoparticles are added to the mixture and coated onto the inner wall of the crucible or the carrier. The mixture coated on the inner wall of the crucible or the support is dried to obtain a catalyst precursor located on the surface of the nanoparticles of the support.

[0014] Optionally, the volatile solvent includes acetone, ethanol, n-propanol, isopropanol, N-methylpyrrolidone, N,N-dimethylformamide, or water.

[0015] Optionally, the carrier is a porous carrier.

[0016] Optionally, the porous carrier may be carbon paper, carbon cloth, carbon foam, copper wire mesh, iron wire mesh, nickel wire mesh, porous glass fiber, molecular sieve, porous ceramic, cellulose-based flexible substrate, or wood-based flexible substrate.

[0017] Optionally, the material to be carbonized includes at least one of petroleum coke powder, needle coke powder, asphalt, asphalt tar, biomass, and organic polymer resin.

[0018] Optionally, the carbonization process may further include: the atmosphere inside the carbonization equipment is a nitrogen atmosphere, an air atmosphere, or an oxygen atmosphere.

[0019] Optionally, the carbonization equipment includes at least one of a tunnel kiln, roller kiln, pusher kiln, fluidized bed, rotary kiln, and Atchison graphitization furnace.

[0020] Secondly, embodiments of this application provide a carbon nanofiber-like material, prepared based on the preparation method described above; The surface of the carbon nanofiber material has a scaly morphology.

[0021] Optionally, the carbon nanofiber material also includes at least one of the following: The length of the carbon nanofiber-like material ranges from 50 nanometers to 5 millimeters; The diameter of the carbon nanofiber material ranges from 0.6 nanometers to 1000 nanometers; The specific surface area of ​​the carbon nanofiber material ranges from 100 square meters per gram to 2000 square meters per gram.

[0022] Optionally, the carbon nanofiber-like material includes at least one of carbon nanotubes and carbon nanofibers.

[0023] The beneficial technical effects of the technical solutions provided in this application include: By placing a catalyst on the surface or inside of the material to be carbonized, on the inner wall of a crucible, or on a carrier above the material, the carbon source gas emitted during carbonization can be catalyzed to decompose and produce carbon nanofiber materials. Furthermore, the carbon nanofiber materials grow on the inner wall of the crucible or on the carrier, preventing them from mixing with the intermediate phase carbides formed by the carbonization of the material at the bottom of the crucible, thus facilitating the collection of the carbon nanofiber materials. In other words, the waste gas (corresponding to the carbon source gas) generated during the carbonization process, which would otherwise require incineration, is converted into a raw material for producing carbon nanofiber materials. This achieves an organic combination of waste gas treatment during carbonization and carbon nanofiber material preparation, utilizing waste gas generated during carbonization that cannot be utilized by other technologies. This not only reduces environmental costs but also produces carbon nanofiber materials, resulting in significant economic and environmental benefits. Moreover, existing carbonization production lines can be easily modified to produce carbon nanofiber materials as a byproduct, eliminating the need for new production lines and reducing equipment costs.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of this application. Attached Figure Description

[0025] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 A schematic flowchart illustrating a method for preparing carbon nanofiber-like materials provided in this application embodiment; Figure 2 A schematic flowchart illustrating another method for preparing carbon nanofiber-like materials provided in this application embodiment; Figure 3 and Figure 4 This is a scanning electron microscope image of the carbon nanofiber material with a scaly morphology obtained in Example 2; Figure 5 The image shows a scanning electron microscope (SEM) image of the amorphous carbon or carbon black obtained in Comparative Example 2. Figure 6 Raman spectra of the carbon nanofiber material obtained in Example 1 and the amorphous carbon or carbon black obtained in Comparative Example 2; Figures 7 to 9 This is a scanning electron microscope image of the carbon nanofiber material obtained in Example 6.

[0026] Figures 10 to 13 This is a scanning electron microscope image of the carbon nanofiber material obtained in Example 7. Detailed Implementation

[0027] The embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the embodiments described below with reference to the accompanying drawings are exemplary descriptions for explaining the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions of the embodiments of this application.

[0028] Those skilled in the art will understand that, unless specifically stated otherwise, the terms "described" and "the" as used herein may also include plural forms. It should be further understood that the term "comprising" as used in the specification of this application means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude other features, information, data, steps, operations, elements, components, and / or combinations thereof supported by the art. The term "and / or" as used herein refers to at least one of the items defined by the term; for example, "A and / or B" can be implemented as "A," or as "B," or as "A and B."

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0030] Carbonization is a common process in the preparation of carbon materials, graphite products, and novel carbon-based functional materials. Carbonization typically involves heat-treating a carbon-containing precursor (the material to be carbonized) at high temperatures, causing non-carbon elements such as hydrogen, oxygen, and nitrogen in the organic components to escape as water, hydrogen gas, ammonia, or other volatile small molecules, thereby removing volatile components from the material. After carbonization, the carbon content of the material is significantly increased, forming a carbon-based framework structure, providing a foundation for subsequent graphitization. The carbonization process not only improves the thermal stability, electrical properties, and chemical stability of the material but also effectively enhances its mechanical strength and density, making it a crucial step in the preparation of carbon materials, graphite products, and novel carbon-based functional materials.

[0031] Carbonization processes typically generate large amounts of organic waste gases containing hydrocarbons, tar vapors, benzene compounds, etc. These organic waste gases usually need to be treated by environmental protection equipment (such as incinerators) before being discharged. Not only do they fail to generate added value, but they also require expensive environmental protection equipment, increasing the company's operating costs.

[0032] The technical solution of this application and how it solves the above-mentioned technical problems are described in detail below with specific embodiments. It should be noted that the following embodiments can be referenced, learned from, or combined with each other, and the same terms, similar features, and similar implementation steps in different embodiments will not be described again.

[0033] This application provides a method for preparing carbon nanofiber-like materials, such as... Figure 1 As shown, the preparation method includes steps S101 to S102.

[0034] S101: Place the material to be carbonized at the bottom of the crucible.

[0035] S102: The crucible is placed in the carbonization equipment for carbonization treatment, so that the material to be carbonized is carbonized and the carbon source gas is discharged. The carbon source gas reacts under high temperature and the action of catalyst to generate carbon nanofiber material. The catalyst is set on the surface or inside of the material to be carbonized, or on the inner wall of the crucible, or on the carrier above the material to be carbonized.

[0036] By placing the catalyst on the surface or inside of the material to be carbonized, on the inner wall of the crucible, or on a carrier above the material to be carbonized, the carbon source gas emitted during the carbonization process can be catalyzed to decompose and produce carbon nanofiber materials. Furthermore, the carbon nanofiber materials grow on the inner wall of the crucible or on the carrier and will not mix with the intermediate phase carbides formed by the carbonization of the material to be carbonized at the bottom of the crucible, making it easy to collect the carbon nanofiber materials.

[0037] In other words, the waste gas (corresponding to the carbon source gas) generated during the carbonization process, which would normally require incineration, is converted into raw material for producing carbon nanofiber materials. This achieves an organic combination of waste gas treatment during the carbonization process and the preparation of carbon nanofiber materials. It utilizes waste gas from the carbonization process that is otherwise unusable by other technologies, not only reducing environmental costs but also producing carbon nanofiber materials, resulting in significant economic and environmental benefits. Furthermore, existing carbonization production lines can be easily modified to produce carbon nanofiber materials as a byproduct, eliminating the need for new production lines and reducing equipment costs.

[0038] In some embodiments, the carbon nanofiber-like material includes at least one of carbon nanotubes and carbon nanofibers.

[0039] In some embodiments, the material to be carbonized is carbonized into an intermediate phase carbide, which includes a carbon-based framework structure.

[0040] In some embodiments, carbon nanofiber materials can be generated when the volatile organic matter content of the material to be carbonized is above 0.5%. In this embodiment, the volatile organic matter content of the material to be carbonized is greater than or equal to 10%, which results in a higher yield of carbon nanofiber materials. For example, waste pitch tar is used as the carbon source, with a volatile matter content of about 50% and an organic volatile matter content of about 50%.

[0041] In some embodiments, the material to be carbonized includes at least one of petroleum coke powder, needle coke powder, pitch, pitch tar, biomass, and organic polymer resin. For example, waste pitch tar can be used as the material to be carbonized, with an organic volatile content of more than 50%.

[0042] Optionally, heteroatom-doped carbon nanofibers can be prepared by using materials containing heteroatoms such as N, S, and P. The introduction of heteroatoms can regulate the electronic structure and surface chemical properties of carbon nanofibers, further enhancing their performance in fields such as electrocatalysis and energy storage.

[0043] In some embodiments, placing the crucible in a carbonization device for carbonization treatment may include: placing the crucible in the carbonization device and heating it to a temperature of 550 degrees Celsius to 1400 degrees Celsius, and holding it at that temperature for 1 hour to 96 hours.

[0044] It should be noted that all numerical ranges in this embodiment include both upper and lower limits. For example, during carbonization, the heating temperature can be 550 degrees Celsius, 850 degrees Celsius, 900 degrees Celsius, 1400 degrees Celsius, etc., and the holding time can be 1 hour, 2 hours, 3 hours, 50 hours, 96 hours, etc.

[0045] In some embodiments, the conditions for the carbonization process may further include: the atmosphere within the carbonization equipment is a nitrogen atmosphere, an air atmosphere, or an oxygen atmosphere.

[0046] In some embodiments, the carbonization equipment includes at least one of a tunnel kiln, roller kiln, pusher kiln, fluidized bed, rotary kiln, and Atchison graphitization furnace.

[0047] In some embodiments, the crucible may be cylindrical, square, etc., and the material of the crucible includes, but is not limited to, silicon carbide, boron nitride, mullite, graphite, steel, etc.

[0048] Optionally, in one embodiment of this application, a method for preparing carbon nanofiber-like materials is provided, the process flow diagram of which is shown below. Figure 2 As shown, it includes the following steps: S201: A catalyst precursor is placed on the inner wall of the crucible or on a support; the catalyst precursor is used to be reduced to metal elemental nanoparticles during the carbonization process to obtain a catalyst; the catalyst precursor includes transition metal compounds.

[0049] In the subsequent carbonization process, the catalyst precursor is reduced to elemental metal nanoparticles by the organic volatiles of the material to be carbonized under high temperature conditions. In other words, the catalyst consists of discrete elemental metal nanoparticles supported on a substrate (i.e., the inner wall of the crucible or the support).

[0050] Optionally, in some embodiments, the transition metal in the catalyst precursor may include at least one of iron, cobalt, and nickel. In other words, the elemental metal nanoparticles may include at least one of iron nanoparticles, cobalt nanoparticles, nickel nanoparticles, and their alloy nanoparticles. The alloy nanoparticles contain at least two of iron, cobalt, and nickel, for example, iron-cobalt alloy nanoparticles, iron-nickel alloy nanoparticles, and cobalt-nickel alloy nanoparticles.

[0051] Optionally, the transition metal in the catalyst precursor may also include molybdenum. That is, the elemental metal nanoparticles may also include at least one of iron-molybdenum alloy nanoparticles, cobalt-molybdenum alloy nanoparticles, and nickel-molybdenum alloy nanoparticles.

[0052] Alloy nanoparticles composed of different transition metals, with alloy phases (e.g., iron-cobalt alloy nanoparticles), can not only improve the solubility and diffusivity of carbon atoms, thereby increasing the growth rate and overall yield of carbon nanofiber materials; but also, by precisely controlling the ratio of the two metals (e.g., iron and cobalt, or iron and nickel) in the alloy nanoparticles, the size distribution of catalyst particles (i.e., elemental metal nanoparticles) can be more finely controlled. Uniform catalyst particle size leads to a narrower diameter distribution in carbon nanofiber materials, thus achieving better structural control of carbon nanofiber materials (e.g., better control over the diameter and wall number of carbon nanofiber materials). Iron-cobalt alloy nanoparticles... The catalyst exhibits particular advantages in the selective growth of single-walled carbon nanofibers (SWCNTs). It can also effectively inhibit the agglomeration and sintering of catalyst particles under high-temperature conditions, thereby enhancing catalyst stability and lifespan. It can maintain high-efficiency growth of carbon nanofibers for a long time, which is beneficial for large-scale continuous production. In particular, molybdenum can stabilize other metal particles and prevent agglomeration. Furthermore, different metal combinations can change the electronic structure of the catalyst surface, thereby adjusting its adsorption and desorption balance of carbon source molecules. This helps to promote the effective decomposition of carbon sources and reduce the generation of impurities such as amorphous carbon, thus improving the purity of carbon nanofibers.

[0053] In some embodiments, the catalyst precursor may include, but is not limited to, at least one of the following: transition metal oxides, transition metal nitrates, transition metal chlorides, transition metal sulfates, transition metal acetates, transition metal carbonates, transition metal hydroxides, transition metal phosphates, transition metal oxalates, transition metal citrates, transition metal lactates, ferrous gluconate, ferrous fumarate, ferrous succinate, potassium ferricyanide, potassium ferrocyanide, and their hydrates.

[0054] For example, the catalyst precursor includes 100-nanometer ferric oxide particles; or, the catalyst precursor includes 200-nanometer particles of cobalt tetroxide and nickel oxide mixed in a 1:1 ratio; or, the catalyst precursor includes nanoparticles of molybdenum oxide and cobalt tetroxide mixed in a 1:2 ratio.

[0055] For example, catalyst precursors include ferric chloride nanoparticles.

[0056] Optionally, in some feasible embodiments, the elemental metal nanoparticles can be loaded onto support nanoparticles. The elemental metal nanoparticles serve as the catalytic active centers, while the support nanoparticles act as a carrier for loading the elemental metal nanoparticles and modulate the catalytic activity, thereby improving the thermal stability of the catalyst and inhibiting metal particle aggregation. For example, the support nanoparticles can be alumina or silica. Examples include nickel nanoparticles supported on alumina and cobalt nanoparticles coated with silica.

[0057] In some embodiments, the catalyst precursor is in the form of nanoparticles with a diameter ranging from 1 nanometer to 500 nanometers. The diameter of the carbon nanofiber material is directly determined by the size of the metallic nanoparticles; specifically, the outer diameter of the carbon nanofiber material is approximately equal to the diameter of the metallic nanoparticles, and the inner diameter of the carbon nanofiber material is approximately half the diameter of the metallic nanoparticles.

[0058] Specifically, the wall thickness / number of carbon nanofibers is also positively correlated with the size of the metal nanoparticles in the catalyst. The smaller the size of the metal nanoparticles, the more favorable it is to generate single-walled carbon nanofibers; while larger metal nanoparticles tend to generate multi-walled structures.

[0059] Furthermore, the morphology, crystal orientation, and surface energy of the metallic nanoparticles in the catalyst also affect the helix angle and chirality of the carbon nanofiber material, thus determining whether its electrical conductivity is metallic or semiconducting. By precisely controlling the composition, dispersion, and heat treatment conditions of the catalyst, highly directional growth of the carbon nanofiber material structure can be achieved, improving the consistency and application performance of the product.

[0060] In some embodiments, step S201 may include: coating a mixture of catalyst precursor and volatile solvent onto the inner wall of a crucible or a support; and drying the mixture coated onto the inner wall of the crucible or the support to obtain a dried catalyst precursor.

[0061] In some embodiments, the mixture may be a salt solution or a particulate dispersion.

[0062] By coating a mixture of catalyst precursor and volatile solvent onto the inner wall of a crucible or support, and then removing the volatile solvent through drying, leaving only the catalyst precursor on the inner wall of the crucible or support, the catalyst precursor can be uniformly disposed on the inner wall of the crucible or support. This facilitates the formation of a uniformly attached catalyst on the inner wall of the crucible or support through a reduction reaction, providing sufficient active sites for the subsequent adsorption and cracking of carbon source gas, thereby improving the efficiency of the catalyst and, consequently, the yield of carbon nanofiber materials.

[0063] Optionally, in some other feasible embodiments, step S201 may include: preparing a mixture of catalyst precursor and volatile solvent; adding carrier nanoparticles to the mixture and coating them on the inner wall of a crucible or the carrier; and drying the mixture coated on the inner wall of the crucible or the carrier to obtain a catalyst precursor located on the surface of the carrier nanoparticles.

[0064] By adding carrier nanoparticles to the mixture, the mixture of catalyst precursor and volatile solvent fully wets the nanopores of the carrier nanoparticles; through drying treatment, the catalyst precursor (i.e., transition metal salt) crystallizes out and remains on the inner and outer surfaces of the carrier nanoparticles; then during the carbonization process, the catalyst precursor is reduced by the organic volatiles of the material to be carbonized into elemental metal nanoparticles, which are then loaded onto the carrier nanoparticles.

[0065] Metal elemental nanoparticles serve as catalytic active centers, while carrier nanoparticles act as supports for loading metal elemental nanoparticles and regulate catalytic activity, thereby improving the thermal stability of the catalyst and inhibiting the aggregation of metal particles.

[0066] In some embodiments, the volatile solvent may include acetone, ethanol, n-propanol, isopropanol, N-methylpyrrolidone, N,N-dimethylformamide, or water. It is understood that the volatile solvent may also be other organic or inorganic solvents, which will not be listed here.

[0067] In some embodiments, the drying process can be carried out by oven drying or air drying. Optionally, the drying temperature is 30°C to 80°C, and the drying time is 1 hour to 12 hours. The oven drying or air drying process can be carried out in a ventilated environment to accelerate solvent evaporation and avoid uneven distribution of catalyst precursors.

[0068] Optionally, during the carbonization process, the catalyst catalyzes the decomposition of the carbon source gas upon contact, promoting the orderly deposition and growth of carbon atoms into carbon nanofiber materials. By controlling the type, particle size, and distribution density of the catalyst, the diameter, wall number, and crystallinity of the resulting carbon nanofiber materials can be effectively controlled, thereby optimizing their electrical and mechanical properties.

[0069] In this embodiment, the support can be a porous support. A porous support can increase the gas-solid reaction area, thereby increasing the yield of carbon nanofiber materials.

[0070] For example, porous supports can be carbon paper, carbon cloth, carbon foam, copper wire mesh, iron wire mesh, nickel wire mesh, porous glass fiber, molecular sieve, porous ceramics, cellulose-based flexible substrates, or wood-based flexible substrates. Through porous supports with high specific surface area, more and more dispersed active sites can be loaded, effectively promoting the adsorption and decomposition of carbon source gases, thereby improving the growth density and quality of carbon nanofiber materials.

[0071] Carbon paper, also known as carbon fiber paper, is mainly made of carbon fibers (chopped or powdered) and binders through a papermaking process.

[0072] Carbon cloth, also known as carbon fiber cloth, is woven from carbon fiber filaments. Optionally, carbon cloth can be activated carbon fiber cloth, which is obtained by activating carbon cloth, creating a large number of nanoscale micropores on the basis of the original carbon cloth.

[0073] Cellulose-based flexible substrates are flexible substrates made from purified materials that are essentially free of lignin and hemicellulose. Examples include cotton towels, filter paper, or cellulose sponges.

[0074] Wood-based flexible substrates are flexible substrates prepared from wood derivatives that retain or partially retain lignin and hemicellulose. Examples include paper napkins.

[0075] By using cellulose-based flexible substrates or wood-based flexible substrates as carriers, a large amount of mixture of catalyst precursor and volatile solvent can be absorbed, and the mixture can be dried rapidly.

[0076] It should be noted that since cellulose-based flexible substrates or wood-based flexible substrates will carbonize at around 900 degrees Celsius, the actual carrier is a carbonized cellulose substrate or a carbonized wood-based flexible substrate (i.e., carbon cloth or carbon paper).

[0077] S202: Place the material to be carbonized at the bottom of the crucible.

[0078] S203: After placing the crucible in the carbonization equipment, heat it to a temperature of 550 degrees Celsius to 1400 degrees Celsius and keep it at that temperature for 1 hour to 96 hours. This carbonizes the material to be carbonized and releases the carbon source gas, allowing the carbon source gas to react under high temperature and the action of a catalyst to generate carbon nanofiber materials.

[0079] For example, the heating temperature can be 550 degrees Celsius, 750 degrees Celsius, 780 degrees Celsius, 850 degrees Celsius, 900 degrees Celsius, 1050 degrees Celsius, 1400 degrees Celsius, etc.

[0080] It should be noted that all numerical ranges in the embodiments of this application include both upper and lower limits.

[0081] The heating temperature primarily depends on the combination of the catalyst and the material to be carbonized. Within the temperature range of 550°C to 1400°C, the catalyst exhibits high activity in the cracking of the carbon source gas while avoiding structural collapse caused by excessive ablation. Different catalysts, such as iron, cobalt, nickel, and their oxides, exhibit varying catalytic efficiencies at specific temperatures. Combining these with a porous support can further enhance thermal stability and reaction uniformity. By precisely controlling the heating rate and holding time, the directional growth of carbon nanofiber materials can be achieved, suppressing the formation of amorphous carbon and thus obtaining high-purity, high-performance carbon material products.

[0082] During the carbonization process, the concentration and composition of the waste gas (volatile matter) change dynamically with carbonization time. The amount of volatile organic compounds is relatively high in the early stages of carbonization and relatively low in the later stages. In this embodiment, by controlling the holding time and / or setting an excess of catalyst, the uniformity of carbon nanofiber growth can be ensured, achieving adaptability to a wide range of carbon source concentrations, thereby ensuring the stable generation of carbon nanofiber materials throughout the longer carbonization process.

[0083] Optionally, in some embodiments, the heating temperature range can be from 550 degrees Celsius to 850 degrees Celsius. Within this temperature range, the catalyst exhibits good selectivity for the pyrolysis reaction of hydrocarbons, which is beneficial for the dissolution and diffusion of carbon atoms on the surface of elemental metal nanoparticles, thereby promoting the nucleation and growth of single-walled or multi-walled carbon nanofiber materials.

[0084] This application provides a method for preparing carbon nanofiber materials. Using chemical vapor deposition (CVD), a mixture of catalyst and volatile solvent is uniformly coated onto the inner wall of a crucible or a support. After drying, uniformly distributed catalytic active sites are formed. The material to be carbonized is decomposed at high temperature to generate carbon source gas. The carbon source gas reacts at 550 to 1400 degrees Celsius for 1 to 96 hours under the action of a catalyst, efficiently generating carbon nanofiber materials. Combined with the large specific surface area advantage of the porous support, the yield and quality of the carbon nanofiber materials are further improved.

[0085] The preparation method of the carbon nanofiber material of this application and the material of the carbon nanofiber material manufactured therefrom will be further described below with reference to specific embodiments and comparative examples, as shown in Table 1.

[0086] Table 1

[0087] As an example, Example 1 may include: placing petroleum coke powder (volatile matter approximately 10%) in a crucible, placing a copper wire mesh coated with a catalyst on top of the petroleum coke powder, the catalyst being coated by immersing the copper wire mesh in a 0.1 mol / L FeCl3 (ferric chloride) acetone solution, removing it and allowing it to air dry naturally. The crucible is then placed in a tunnel kiln and carbonized at 900 degrees Celsius for 24 hours. After the crucible cools, the copper wire mesh is removed, and the carbon nanofiber-like material grown within the mesh is mechanically scraped out and sieved to remove various impurities, yielding the finished carbon nanofiber-like material; the carbonized material at the bottom of the crucible is subsequently collected.

[0088] As an example, the only difference between the experimental conditions of Example 2 and Example 1 is the coating method of the catalyst and the catalyst support. In Example 2, the catalyst was coated by immersing a copper wire mesh in a 2% ethanol dispersion of a 1:1 mixture of cobalt tetroxide and nickel oxide. In Example 2, the catalyst support was the inner wall of a crucible.

[0089] The only difference between Comparative Example 2 and Example 1 is that no catalyst was used; all other conditions were exactly the same. The product obtained was amorphous carbon or carbon black, indicating that the catalyst plays a decisive role in the formation of carbon nanofiber materials. Comparative Example 3 was a blank control experiment, without both catalyst support and catalyst. No carbon material product was obtained after the reaction, indicating that without a catalytic system, petroleum coke powder cannot effectively generate the target carbon nanofiber materials.

[0090] The only difference between the experimental conditions of Example 6 and Example 1 is the change in catalyst support. The only difference between the experimental conditions of Example 7 and Example 6 is the change in catalyst. The products obtained in Examples 6 and 7 are carbon nanofiber materials with extremely high aspect ratios. It can be seen that carbon cloth as a catalyst support can improve the aspect ratio of the obtained carbon nanofiber materials.

[0091] It is understood that the experimental conditions for other embodiments and comparative examples are shown in Table 1 above, and will not be repeated here.

[0092] See Figure 3 and Figure 4 , Figure 3 and Figure 4 The image shown is a scanning electron microscope image of the carbon nanofiber material with a scaly morphology obtained in Example 2 (i.e., sample B). It shows the morphology of carbon nanofiber material with a diameter of about 200 nm, but the surface exhibits a graphene-like two-dimensional sheet structure.

[0093] Figure 5 The image shows a scanning electron microscope (SEM) image of the amorphous carbon or carbon black obtained in Comparative Example 2 (i.e., sample C).

[0094] Figure 6 The images show the Raman spectra of sample A (the carbon nanofiber material obtained in Example 1) and sample C. The horizontal axis represents the Raman shift, in cm. - ¹; The vertical axis represents the intensity of Raman scattered light.

[0095] Figure 5 The amorphous carbon or carbon black (i.e., sample C) appears as aggregates of small carbon particles with a diameter of approximately 200 nm to 500 nm, exhibiting an overall carbon black morphology. This result is consistent with Raman spectroscopy analysis, and its ID / IG value is significantly higher than that of Examples 1 and 2, indicating a higher defect density and lower degree of graphitization in the carbon structure.

[0096] Combination Figure 6 The Raman spectrum shown indicates that sample A has a wavelength of 1350 cm⁻¹. - ¹ and 1580 cm - ¹ Distinct D and G peaks appear at points ¹, with the G peak (approximately 1580 cm⁻¹) being the most prominent. - ¹) Sharp peaks, a weak D peak, and a prominent 2D peak are characteristic of carbon nanotubes with good crystallinity. Sample C, on the other hand, exhibits very broad and connected D and G peaks, further confirming that its main component is amorphous carbon or carbon black. The Raman characteristics described above are in high agreement with electron microscopy observations, further demonstrating that precise design of the catalyst system can effectively control the crystal quality and microstructure of the carbon products.

[0097] Figure 6 In the figure, the horizontal axis represents Raman displacement, and the unit is wavenumber (cm). - ¹); The vertical axis represents relative intensity, in au (arbitrary units).

[0098] The specific surface area, TGA oxidation onset temperature, and TGA weight loss peak temperature of samples A, B, and C are shown in Table 2.

[0099] Table 2

[0100] As shown in Table 2, the specific surface area of ​​sample A and sample B is significantly lower than that of sample C, but their TGA oxidation onset temperature and weight loss peak temperature are significantly higher than those of sample C, indicating that their carbon structure has higher thermal stability and crystallinity.

[0101] Further analysis of Examples 3 and 4 reveals that the type of catalyst and reaction temperature significantly regulate the morphology and diameter distribution of the carbon nanofiber materials. Example 3 used iron oxide (Fe3O4) supported on alumina particles, obtaining carbon nanofiber materials with diameters of 5–50 nm at 850 °C, exhibiting high growth activity and size uniformity. In Example 4, the mixed catalyst of molybdenum oxide and cobalt tetroxide induced the formation of carbon nanofiber materials at 780 °C, expanding the diameter range to 10–100 nm, indicating that the composite catalyst can lower the reaction energy barrier and influence the diameter evolution.

[0102] As can be seen from Comparative Example 1 and Example 1, nickel metal foil, as a catalyst and self-supporting carrier, can induce the formation of graphene layers, while copper wire mesh tends to guide the vertical growth of carbon nanofiber materials, indicating that the orientation of metal crystal planes has a guiding effect on carbon structure.

[0103] Combined with Example 5, it was found that waste pitch tar can still be used as a carbon source to obtain carbon nanofiber materials with a diameter of 80–200 nm, confirming that different carbon sources are feasible under suitable catalytic systems.

[0104] Figures 7 to 9 This is a scanning electron microscope image of the carbon nanofiber material obtained in Example 6.

[0105] Figures 10 to 13 This is a scanning electron microscope image of the carbon nanofiber material obtained in Example 7.

[0106] See Figures 7 to 13 The products obtained in Examples 6 and 7 are both carbon nanofiber materials with extremely high aspect ratios. Therefore, combining Comparative Example 1 with Examples 6 and 7, it can be seen that carbon cloth as a catalyst support can improve the aspect ratio of the obtained carbon nanofiber materials.

[0107] In summary, as shown in Table 1, different catalysts and their supports, as well as temperature conditions, have a significant impact on the formation of carbon nanofiber materials. Without a catalyst or support, it is difficult to form effective products; however, suitable metal oxide catalysts combined with appropriate particle size and reaction temperature can promote the directional growth of carbon nanofiber materials. The type, ratio, and dispersion state of the catalyst directly affect the morphology and purity of the carbon products, indicating the crucial role of the catalytic system in the carbonization process. Furthermore, the physical structure of the support also affects the mass transfer efficiency and thermal stability of the reaction interface; network supports, due to their large specific surface area and favorable gas flow permeability, significantly improve the yield and uniformity of carbon nanofiber materials.

[0108] The beneficial technical effects of the technical solutions provided in this application include: By placing a catalyst on the surface or inside of the material to be carbonized, on the inner wall of a crucible, or on a support above the material, the carbon source gas emitted during carbonization can be catalyzed to decompose and produce carbon nanofiber materials. Furthermore, the carbon nanofiber materials grow on the inner wall of the crucible or on the support, preventing them from mixing with the intermediate phase carbides formed by the carbonization of the material at the bottom of the crucible, thus facilitating the collection of the carbon nanofiber materials. In other words, the waste gas generated during the carbonization process, which would otherwise require incineration, is converted into a raw material for producing carbon nanofiber materials. This achieves an organic combination of waste gas treatment during carbonization and the preparation of carbon nanofiber materials, utilizing waste gas from the carbonization process that is otherwise unusable by other technologies. This not only reduces environmental costs but also produces carbon nanofiber materials, resulting in significant economic and environmental benefits.

[0109] Meanwhile, the heat released by the carbonization reaction can maintain the reaction temperature required for the carbon source gas to be converted into carbon nanofiber materials, without the need for additional energy input, further reducing energy consumption.

[0110] Furthermore, this method avoids using flammable and explosive gases such as methane and acetylene as carbon source gases, thereby eliminating the safety hazards associated with using high-pressure flammable gases and improving safety.

[0111] Furthermore, this method allows for the simple modification of existing carbonization production lines to produce carbon nanofiber materials as a byproduct, eliminating the need for new production lines and reducing equipment costs. The method is compatible with existing conventional carbonization equipment such as tunnel kilns and pusher kilns, is easy to implement, and is suitable for large-scale production.

[0112] Furthermore, by adjusting the type of catalyst, the structure of the support, and the reaction temperature, the morphology and quality of carbon nanofiber materials can be precisely controlled. For example, the carbon nanofiber materials prepared by this method exhibit controllability in terms of tube diameter, length, specific surface area, and wall number, thus demonstrating excellent electrical and structural properties.

[0113] Based on the same inventive concept, this application provides a carbon nanofiber material prepared by the preparation method described above; The surface of the carbon nanofiber material has a scaly morphology.

[0114] Optionally, the carbon nanofiber material may also include at least one of the following: The length of the carbon nanofiber-like material ranges from 50 nanometers to 5 millimeters; The diameter of carbon nanofiber-like materials ranges from 0.6 nanometers to 1000 nanometers; The specific surface area of ​​carbon nanofiber materials ranges from 100 square meters per gram to 2000 square meters per gram.

[0115] Optionally, the morphology and quality of carbon nanofiber materials can be precisely controlled by adjusting the type of catalyst, the structure of the support, and the reaction temperature. For example, the carbon nanofiber materials prepared by this method have controllable diameter, length, specific surface area, and wall number, thus exhibiting excellent electrical and structural properties.

[0116] Optionally, by adjusting the ratio and size of elemental metal nanoparticles to oxide nanoparticles, the diameter, wall number, and crystallinity of carbon nanofiber materials can be precisely controlled, thereby optimizing their electrical and mechanical properties to meet the needs of different applications. For example, when using silica-supported iron-nickel alloy nanoparticles as a catalyst, the growth direction and density of carbon nanofiber materials can be effectively controlled by adjusting the pore size of silica and the loading of iron-nickel alloy nanoparticles, thus enhancing their reinforcing effect in composite materials.

[0117] In some embodiments, the carbon nanofiber material can have a single-walled, double-walled, or multi-walled structure. This carbon nanofiber material has high purity and few defects, making it suitable for applications such as lithium-ion battery anode materials, conductive additives, and composite reinforcing materials.

[0118] The beneficial technical effects of the technical solutions provided in this application include: By converting the waste gas generated during the carbonization process, which originally required incineration, into carbon nanofiber materials, the waste gas treatment of the carbonization process and the preparation of carbon nanofiber materials are effectively coupled. This not only reduces environmental protection costs but also produces carbon nanofiber materials, resulting in significant economic and environmental benefits. Furthermore, the production of carbon nanofiber materials as a byproduct can be achieved by simply modifying existing carbonization production lines, eliminating the need for new production lines and reducing equipment costs.

[0119] Those skilled in the art will understand that the steps, measures, and solutions in the various operations, methods, and processes discussed in this application can be alternated, modified, combined, or deleted. Furthermore, other steps, measures, and solutions in the various operations, methods, and processes discussed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted. Furthermore, steps, measures, and solutions in related technologies that are similar to those disclosed in this application can also be alternated, modified, rearranged, decomposed, combined, or deleted.

[0120] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0121] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0122] The above description is only a partial implementation of this application. It should be noted that for those skilled in the art, other similar implementation methods based on the technical concept of this application, without departing from the technical concept of this application, also fall within the protection scope of the embodiments of this application.

Claims

1. A method for preparing carbon nanofiber-like materials, characterized in that, include: Place the material to be carbonized at the bottom of the crucible; The crucible is placed in a carbonization device for carbonization treatment, so that the material to be carbonized is carbonized and carbon source gas is discharged, and the carbon source gas reacts under high temperature and the action of a catalyst to generate carbon nanofiber material; the catalyst is disposed on the surface or inside of the material to be carbonized, or on the inner wall of the crucible, or on a carrier located above the material to be carbonized.

2. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, The crucible is placed in a carbonization device for carbonization treatment, including: After placing the crucible in the carbonization equipment, heat it to a temperature of 550 degrees Celsius to 1400 degrees Celsius and hold it at that temperature for 1 hour to 96 hours.

3. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, Before placing the material to be carbonized at the bottom of the crucible, the process also includes: A catalyst precursor is disposed on the inner wall of the crucible or on the support; the catalyst precursor is used to be reduced to elemental metal nanoparticles during the carbonization process to obtain the catalyst; The catalyst precursor includes transition metal compounds.

4. The method for preparing carbon nanofiber-like materials according to claim 3, characterized in that, Includes at least one of the following: The transition metal in the catalyst precursor includes at least one of iron, cobalt, and nickel; The catalyst precursor includes at least one of the following: oxides of transition metals, nitrates of transition metals, chlorides of transition metals, sulfates of transition metals, acetates of transition metals, carbonates of transition metals, hydroxides of transition metals, phosphates of transition metals, oxalates of transition metals, citrates of transition metals, lactates of transition metals, ferrous gluconate, ferrous fumarate, ferrous succinate, potassium ferrocyanide, potassium ferrocyanide, and their hydrates.

5. The method for preparing carbon nanofiber-like materials according to claim 4, characterized in that, The transition metal in the catalyst precursor also includes molybdenum.

6. The method for preparing carbon nanofiber-like materials according to claim 3, characterized in that, The catalyst precursor is in the form of nanoparticles, and the particle size range of the catalyst precursor is 1 nanometer to 500 nanometers.

7. The method for preparing carbon nanofiber-like materials according to claim 3, characterized in that, The provision of a catalyst precursor on the inner wall of the crucible or on the support includes: The mixture of the catalyst precursor and the volatile solvent is coated onto the inner wall of the crucible or the support. The mixture coated on the inner wall of the crucible or the support is dried to obtain a dried catalyst precursor.

8. The method for preparing carbon nanofiber-like materials according to claim 3, characterized in that, The provision of a catalyst precursor on the inner wall of the crucible or on the support includes: Prepare a mixture of the catalyst precursor and a volatile solvent; The carrier nanoparticles are added to the mixture and coated onto the inner wall of the crucible or the carrier. The mixture coated on the inner wall of the crucible or the support is dried to obtain a catalyst precursor located on the surface of the nanoparticles of the support.

9. The method for preparing carbon nanofiber-like materials according to claim 7 or 8, characterized in that, The volatile solvents include acetone, ethanol, n-propanol, isopropanol, N-methylpyrrolidone, N,N-dimethylformamide, or water.

10. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, The carrier is a porous carrier.

11. The method for preparing carbon nanofiber-like materials according to claim 10, characterized in that, The porous carrier is carbon paper, carbon cloth, carbon foam, copper wire mesh, iron wire mesh, nickel wire mesh, porous glass fiber, molecular sieve, porous ceramic, cellulose-based flexible substrate, or wood-based flexible substrate.

12. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, The material to be carbonized includes at least one of petroleum coke powder, needle coke powder, asphalt, asphalt tar, biomass, and organic polymer resin.

13. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, The conditions for the carbonization process also include that the atmosphere inside the carbonization equipment is a nitrogen atmosphere, an air atmosphere, or an oxygen atmosphere.

14. The method for preparing carbon nanofiber-like materials according to claim 1, characterized in that, The carbonization equipment includes at least one of the following: tunnel kiln, roller kiln, pusher kiln, fluidized bed, rotary kiln, and Atchison graphitization furnace.

15. A carbon nanofiber-like material, characterized in that, Prepared using the preparation method according to any one of claims 1-14; The surface of the carbon nanofiber material has a scaly morphology.

16. The carbon nanofiber-like material according to claim 15, characterized in that, It also includes at least one of the following: The length of the carbon nanofiber-like material ranges from 50 nanometers to 5 millimeters; The diameter of the carbon nanofiber material ranges from 0.6 nanometers to 1000 nanometers; The specific surface area of ​​the carbon nanofiber material ranges from 100 square meters per gram to 2000 square meters per gram.

17. The carbon nanofiber material according to claim 15, wherein the carbon nanofiber material comprises at least one of carbon nanotubes and carbon nanofibers.

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