Graphite-based composite material with high strength and excellent conductivity and preparation method thereof

Abstract

The invention relates to a graphite-based composite material with high strength and excellent conductivity. Specifically, the invention discloses a graphite-based composite material with high strength and excellent conductivity and a preparation method thereof, petroleum coke, asphalt or graphite powder and the like are used as a matrix, a small amount of fullerene powder is added as a sintering aid, and the raw materials are put into a planetary ball mill to be mixed to prepare precursor mixed powder; and pre-treating the precursor powder, then applying pressure in a protective atmosphere or a vacuum atmosphere, and performing high-temperature sintering to obtain the graphite-based composite material. The breaking strength of the obtained graphite-based composite material is not lower than 50 MPa, the compression strength is not lower than 100 MPa, and the conductivity is not lower than 5 * 10 < 4 > S / m.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic materials, in particular to the field of carbon material preparation technology. BACKGROUND

[0002] Graphite is an indispensable material in advanced applications such as nuclear reactor components and electrodes due to its excellent thermal and electrical conductivity, extremely high temperature resistance, and low thermal expansion coefficient. However, graphite still faces many challenges in terms of performance and processing. In terms of performance, the mechanical properties of graphite are prone to cleavage due to the weak interlayer van der Waals force. In terms of processing, graphite powder is difficult to directly sinter into a dense block, and its inherent structural anisotropy is the main limiting factor. This anisotropy leads to a mismatch in the thermal expansion coefficients between different crystal directions, which easily produces internal stress and induces microcracks at the grain boundaries during cooling, thereby destroying the bonding and densification sintering between particles, limiting the application of conventional sintering methods in the preparation of bulk graphite.

[0003] Currently, the traditional preparation process of commercial graphite includes two steps: first, carbonization at 800-1200℃ to convert raw materials such as petroleum coke or pitch into a carbon matrix; then graphitization at a high temperature of, for example, above 2500℃ to induce crystal ordering, resulting in an ISO-88 commercial graphite material with a density of up to 1.9 g / cm 3 and a bending strength of more than 90 MPa. However, this method usually requires multiple rounds of baking and impregnation processes, with a production cycle of more than 30 days, and needs to be graphitized at extremely high temperatures above 2500℃, resulting in huge energy consumption.

[0004] So far, there has been no graphite material with excellent performance obtained by single sintering. SUMMARY

[0005] One of the technical problems to be solved by the present application is to provide a graphite-based composite material with high strength and excellent electrical conductivity.

[0006] Another technical problem to be solved by the present application is to provide a method for producing a high-performance graphite-based composite material with higher production efficiency and lower energy consumption.

[0007] To solve the above technical problems, the technical solution of the first aspect of the present application is: a graphite-based composite material, the structure of the graphite-based composite material comprising a graphite phase and an amorphous carbon phase; wherein the graphite phase and the amorphous carbon phase are alternately distributed in phases, and the width of the graphite phase is not more than 200 nm, and the width of the amorphous carbon phase is not more than 50 nm. It has been found that the graphite-based composite material has high strength and excellent electrical conductivity, with high compressive strength (>100 MPa), high bending strength (>50 MPa), and high electrical conductivity (>5×10 4 S / m).

[0008] Secondly, this invention discloses a method for preparing a graphite-based composite material, which includes the following steps:

[0009] A) Using petroleum coke, pitch, graphite or a mixture thereof as the matrix raw material, and fullerene as the sintering aid, the two are ground and uniformly mixed to obtain a precursor powder, wherein the mass ratio of the sintering aid to the matrix raw material is 0.005:1 to 0.6:1.

[0010] B) Disperse the precursor powder in an organic solvent, and then treat the resulting precursor powder dispersion in an inert atmosphere at a temperature above 100°C and a pressure above 4MPa for at least 12 hours.

[0011] C) After removing the solvent from the precursor powder dispersion in step B), the dried powder is loaded into a mold, pre-pressed, and the pre-pressed green body is placed into a sintering mold.

[0012] D) Place the pre-pressed billet from step C) together with the sintering mold into a spark plasma sintering equipment or a hot pressing sintering equipment, and then sinter it in a vacuum or inert gas environment.

[0013] E) After cooling, remove the mold and demold to obtain the graphite-based composite material.

[0014] The graphite-based composite material prepared by the above method comprises a graphite phase and an amorphous carbon phase in its structural composition; wherein the graphite phase and the amorphous carbon phase are alternately distributed, and the width of the graphite phase does not exceed 200 nm, and the width of the amorphous carbon phase does not exceed 50 nm. This graphite-based composite material possesses both high strength and excellent electrical conductivity, exhibiting high compressive strength (>100 MPa), high flexural strength (>50 MPa), and high electrical conductivity (>5 × 10⁻⁶ MPa) at room temperature. 4 S / m).

[0015] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0016] 1) High compressive strength (>100MPa), high flexural strength (>50MPa), and excellent electrical conductivity (>5×10⁻⁶) were obtained. 4 The new material (S / m) can be used in many special application environments with stringent material requirements.

[0017] 2) The preparation method of the present invention is highly efficient, has a short production cycle, and requires only one sintering cycle with lower energy consumption. Attached Figure Description

[0018] Figure 1 This is a physical image of the graphite-based composite material with both high strength and excellent electrical conductivity prepared in Example 1 of the present invention;

[0019] Figure 2 This is a transmission electron microscope (TEM) image of a typical region of the graphite-based composite material of Example 1 of the present invention;

[0020] Figure 3 (a) is a compressive stress-strain curve of the graphite-based composite material of Example 1 of the present invention. Figure 3 (b) is the electrical conductivity test data of the graphite-based composite material of Example 1 of the present invention;

[0021] Figure 4 (a) is a compressive stress-strain curve of the graphite-based composite material of Example 2 of the present invention. Figure 4 (b) shows the electrical conductivity test data of the graphite-based composite material in Example 2 of the present invention;

[0022] Figure 5 (a) is a compressive stress-strain curve of the graphite-based composite material of Example 3 of the present invention. Figure 5 (b) shows the electrical conductivity test data of the graphite-based composite material in Example 3 of the present invention;

[0023] Figure 6 (a) is a compressive stress-strain curve of the graphite-based composite material in Example 4 of the present invention. Figure 6 (b) shows the electrical conductivity test data of the graphite-based composite material in Example 4 of the present invention. Detailed Implementation

[0024] Where numerical ranges are disclosed herein, these ranges are continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Additionally, where the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Furthermore, where multiple ranges are provided to describe a feature or characteristic, these ranges may be combined. That is, unless otherwise specified, all ranges disclosed herein should be understood to encompass any and all subranges contained herein. For example, the specified range of “1–10” should be considered to include any and all subranges between the minimum value of 1 and the maximum value of 10. Furthermore, the dosage ranges for each component of the invention include any combination of any lower and upper limits mentioned in the specification, all of which are covered within the scope of the invention.

[0025] When used herein, as will be understood by those skilled in the art, “about” means, in the specific scientific context of the term, that the number, parameter, or characteristic it defines is permissible with a range of positive or negative percentage errors (e.g., ±5%). Furthermore, because all numbers, values, and expressions relating to quantities used herein are subject to various measurement errors, unless otherwise indicated, all specific numerical values ​​recorded may be understood to be implicitly modified by the term “about.”

[0026] This invention provides a graphite-based composite material, the structure of which comprises alternating graphite and amorphous carbon phases; the graphite phase is obtained by carbonization of precursors such as pitch, petroleum coke, and graphite powder; the amorphous carbon phase is obtained by fullerene phase transformation. This is a graphite-based composite material exhibiting both high strength and excellent electrical conductivity: compressive strength not less than 100 MPa, flexural strength not less than 50 MPa, and electrical conductivity not less than 5 × 10⁻⁶ MPa. 4 S / m (both measured at room temperature).

[0027] In the context of this invention, "graphite-based composite material" refers to a material that, from a chemical composition perspective, is primarily composed of pure carbon elements, and from a microstructure perspective, is predominantly composed of a graphite structure. The graphite-based composite material of this invention, from a microstructural perspective (e.g., as observed by transmission electron microscopy), possesses a unique structure composed of alternating graphite and amorphous carbon phases.

[0028] However, those skilled in the art will understand that "graphite-based composite material" does not exclude unavoidable traces of impurity elements present in the raw materials themselves or unintentionally introduced during processing. For the purposes of this invention, "consisting essentially of pure carbon" means that the mass of carbon accounts for at least 97% of the total mass of the material, preferably at least 98%, more preferably at least 99%, and most preferably at least 99.9% or close to 100%.

[0029] The graphite-based composite material of this application, from a microstructural perspective, comprises alternating graphite and amorphous carbon phases, wherein the amorphous carbon phase is mainly composed of disordered sp... 2 The material is composed of carbon (e.g., graphene fragments). Preferably, the graphite phase and amorphous carbon phase constitute at least 85% of the total mass of the material, more preferably at least 90%, and even more preferably at least 95%. Most preferably, the graphite-based composite material of this application consists essentially of only two phases: a graphite phase and an amorphous carbon phase. "Essentially consisting of only two phases: a graphite phase and an amorphous carbon phase" can be understood as the graphite phase and amorphous carbon phase constituting at least 97% of the total mass of the material, preferably at least 98%, more preferably at least 99%, and for example, close to 100%.

[0030] Preferably, from a microstructural perspective, the graphite phase and amorphous carbon phase in the graphite-based composite material of this application are alternately distributed, with the graphite phase width not exceeding 200 nm and the amorphous carbon phase width not exceeding 50 nm. Those skilled in the art will understand that, since the microstructure of a material cannot be completely and precisely controlled, in the context of this application, the phrase "the graphite phase and amorphous carbon phase are alternately distributed, with the graphite phase width not exceeding 200 nm and the amorphous carbon phase width not exceeding 50 nm" is understood to mean that the structural characteristics of more than 85%, preferably more than 90%, of the material are consistent with this description (this can be determined, for example, by randomly sampling 20 or 50 regions within the material and observing their microstructure).

[0031] Those skilled in the art will understand that various techniques exist for obtaining information about the microstructure of materials. For example, direct observation can be performed using instruments such as transmission electron microscopes. For accurate characterization, it is preferable to analyze samples from within the material. Furthermore, to avoid interference from trace amounts of contaminants that may be present in the material, multiple random samplings (e.g., more than 10, 20, 30, 40, 50, or even more) can be taken for analysis.

[0032] In this document, "high strength" refers to a material's flexural strength of not less than 50 MPa, such as not less than 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, etc., preferably not less than about 80 MPa; and / or a material's compressive strength of not less than 100 MPa, such as not less than 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 1800 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 270 MPa, 300 MPa, etc., preferably not less than about 120 MPa. The flexural strength is preferably measured using the three-point bending method. Specific test conditions for flexural strength and compressive strength can be found in the examples provided.

[0033] When used in this article, "excellent electrical conductivity" refers to a material with an electrical conductivity of not less than 5 × 10⁻⁶. 4 S / m, for example, not less than 5.2×10 4 S / m, 5.4×10 4 S / m, 5.6×10 4 S / m, 5.8×10 4 S / m, 6.0×10 4 S / m, 6.2×10 4 S / m, 6.4×10 4 S / m, 6.6×10 4S / m, 6.8×10 4 S / m, 7.0×10 4 S / m, 7.2×10 4 S / m, 7.4×10 4 S / m, etc., preferably not less than about 7×10 4 S / m. The conductivity is preferably measured using the four-wire method, and specific test conditions can be found in the examples described.

[0034] In the graphite-based composite material of this application, the mass ratio of graphite phase to amorphous carbon phase can be selected and adjusted as needed, and can vary within a wide range, thereby allowing technicians to design and prepare graphite-based composite materials with various properties. However, the amount of amorphous carbon phase is usually less than the amount of graphite phase. The mass ratio of amorphous carbon to graphite phase is typically greater than 0.005:1 and typically less than 0.6:1, for example, it can be 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, or any ratio within the range of any two of the above ratios. The mass ratio of amorphous carbon phase to graphite phase is preferably 0.01:1 to 0.5:1 or 0.02:1 to 0.5:1, more preferably 0.03:1 to 0.45:1. The mass ratio of amorphous carbon phase to graphite phase in graphite-based composite materials can be determined by those skilled in the art using conventional techniques. For example, multiple regions of the material can be observed using microscopic imaging techniques (such as TEM), and the mass ratio can be estimated based on the area ratio of the two phases in the microscopic images of the material in each region. The average value of multiple regions can then be calculated to determine the mass ratio of the two phases. Alternatively, the ratio of the two phases can be estimated based on the amount of starting materials used in the preparation reaction of the graphite-based composite material.

[0035] The graphite-based composite material of the present invention, which combines high strength and excellent electrical conductivity, can be obtained by the following preparation method, which mainly includes the following steps:

[0036] A) Using petroleum coke, pitch, graphite or a mixture thereof as the matrix raw material, and fullerene as the sintering aid, the two are ground and uniformly mixed to obtain a precursor powder, wherein the mass ratio of the sintering aid to the matrix raw material is 0.005:1 to 0.6:1.

[0037] B) Disperse the precursor powder in an organic solvent, and then treat the resulting precursor powder dispersion in an inert atmosphere at a temperature above 100°C and a pressure above 4MPa for at least 12 hours.

[0038] C) After removing the solvent from the precursor powder dispersion in step B), the dried powder is loaded into a mold, pre-pressed, and the pre-pressed green body is placed into a sintering mold.

[0039] D) Place the pre-pressed billet from step C) together with the sintering mold into a spark plasma sintering equipment or a hot pressing sintering equipment, and then sinter it in a vacuum or inert gas environment.

[0040] E) After cooling, remove the mold and demold to obtain the graphite-based composite material.

[0041] In the context of this invention, "fullerene" refers to a class of cage-like molecules composed entirely of carbon atoms, whose structure consists of five-membered and six-membered rings, including C... 60 C 70 C 84 C 90 C 96 C 120 C 540 Various carbon atom clusters, etc. In this application, preferred fullerenes include C... 60 C 70 C 84 and C 120 And their mixtures.

[0042] It has been found that materials such as petroleum coke, asphalt, and graphite undergo carbonization transformation at high temperatures to become graphite as the matrix phase, while fullerene powder can transform into amorphous carbon at high temperatures, exhibiting excellent strength and acting as a toughening agent. Therefore, this invention uses materials such as petroleum coke, asphalt, and graphite as matrix raw materials to form the graphite phase, and uses fullerene powder as a sintering aid to form the amorphous carbon phase.

[0043] In some preferred embodiments of the present invention, step A) is achieved by grinding and mixing asphalt, petroleum coke, graphite, or mixtures thereof with fullerene, and then loading the mixture into a planetary ball mill for ball milling (an organic solvent may be optionally added to assist mixing). Through repeated impact and shearing between the balls, the fullerene powder is fully and uniformly dispersed among the graphite phase powder, thereby enhancing the contact and uniformity between the two. The uniform mixing of the two raw materials plays a crucial role in densification and microstructure uniformity during the subsequent sintering process.

[0044] For example, as an example of the preparation method of the present invention, step A) is performed as follows: a certain mass of petroleum coke powder, asphalt or graphite powder and a small amount of fullerene powder are weighed according to a predetermined mass ratio, the raw materials are loaded into a planetary ball mill for mixing, the ball milling time is 2 to 12 hours, the mixed powder is taken out and then placed in an oven to dry, and the obtained powder is sieved through a stainless steel standard sieve to obtain the precursor powder of graphite-based composite material.

[0045] In another embodiment, liquid-phase mixing can also be used to achieve uniform mixing of the two raw materials. For example, the powders of the two raw materials are dispersed in an organic solvent and then ultrasonically treated to make them uniformly mixed.

[0046] This invention does not have special requirements for the particle size of the driving powder. Micron-sized powder is usually used, that is, the average particle size of the powder can be between 1 and 20 microns.

[0047] In step A), the raw materials used, such as petroleum coke, asphalt, graphite, and fullerene, are preferably high-purity raw materials. In this application, "high purity" is understood to mean a purity of at least, for example, 97%, preferably at least 98%, more preferably at least 99%, and most preferably at least 99.9% or close to 100%. To obtain the aforementioned "high-purity" raw materials, the raw materials can be purified or refined. The purification process can include, for example, acid washing, heating, and filtration.

[0048] The mass ratio of petroleum coke, pitch, graphite, and fullerene materials used in step A) can be selected and adjusted as needed, and can vary within a wide range, allowing technicians to design and prepare graphite-based composite materials with various properties. Typically, the amount of amorphous carbon phase material is less than that of graphite phase material. The mass ratio of sintering aids (fullerene materials) to matrix raw materials (petroleum coke, pitch, graphite, etc.) is usually greater than 0.005:1 and usually less than 0.6:1, for example, 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0. The ratios are 2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, or any ratio within the range of ratios formed by any two of the above ratios as endpoints; the mass ratio of the amorphous carbon phase to the graphite phase is preferably 0.01:1 to 0.5:1 or 0.02:1 to 0.5:1, more preferably 0.03:1 to 0.45:1.

[0049] After obtaining the precursor powder in step A), in step B), the precursor powder is dispersed in an organic solvent, and then the resulting precursor powder dispersion is treated in an inert atmosphere at a temperature of 100°C or higher and a pressure of 4 MPa or higher for at least 12 hours.

[0050] The organic solvent used in step B) can be any organic solvent commonly used in the art, such as aromatic solvents (e.g., benzene, toluene, etc.) and alcohol solvents (e.g., methanol, ethanol, etc.). For uniform dispersion, the resulting precursor powder dispersion can preferably be treated with ultrasound.

[0051] Those skilled in the art will understand that if a liquid dispersion of the precursor powder is obtained by mixing in step A) using a liquid phase mixing method, then the liquid dispersion can be used directly in step B) without first removing the solvent from the dispersion and then redispersing the obtained powder.

[0052] The resulting precursor powder dispersion was then subjected to high-pressure heating under an inert atmosphere. Due to the unique structure and size of fullerene molecules, under high temperature and pressure, fullerene molecules diffuse into the interlayer structure of materials such as petroleum coke, asphalt, and graphite, resulting in a uniform distribution of fullerenes between each graphite layer. This leads to an alternating distribution of graphite and amorphous carbon phases in the final graphite-based composite material, providing high strength and excellent electrical conductivity.

[0053] There are no particular upper limits to the temperature and pressure in step B), but for economic and practical reasons, the temperature is generally not higher than 300°C and the pressure is generally not higher than 40 MPa. The temperature can be, for example, 100°C, 150°C, 200°C, 250°C, 300°C, or any temperature in between, and the pressure can be 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 15 MPa, 20 MPa, 30 MPa, 40 MPa, or any pressure in between. The treatment time can vary with temperature and pressure, but is typically at least 12 hours, preferably more than 24 hours, and more preferably more than 48 hours.

[0054] Step B) can be carried out in a conventional high-pressure reactor, wherein an inert atmosphere (e.g., He, Ne, Ar, Kr, Xe, etc.) is maintained. Stirring may be optionally employed during the process.

[0055] For example, as an example of the preparation method of the present invention, step B) is performed as follows: the mixed powder is added to toluene and ultrasonically treated for 30 minutes. The solution is then placed in a high-pressure reactor, purged with argon gas to a pressure above 4 MPa, and heated to a temperature above 100°C. The temperature is maintained at this level for at least 48 hours, followed by a slow cooling and depressurization.

[0056] Next, in step C), the solvent is removed from the precursor powder dispersion in step B) to obtain a dry powder, which is then loaded into a mold and pre-pressed. The pre-pressed preform is then placed into a sintering mold.

[0057] Solvent removal can be carried out using conventional methods in the field, such as vacuum evaporation.

[0058] The mold used in step C) is preferably a graphite mold. Preferably, the graphite mold is wrapped with carbon felt, which surrounds the gap in the middle of the graphite mold, thereby reducing heat dissipation in the graphite mold and reducing the temperature gradient inside the graphite mold, thus avoiding inhomogeneity in the microstructure and mechanical properties of the sintered body.

[0059] In step C), the pre-pressed billet can be of any shape, such as a cylinder, block, or sphere, preferably cylindrical. Pre-pressing can be performed on a conventional pressing machine or hydraulic press, usually at room temperature, but can be done in air or an inert atmosphere if necessary. The pre-pressing pressure in step two of this invention is not particularly limited, as long as the billet is compacted. However, for better results, in some preferred embodiments of this invention: in step C), pre-pressing involves applying pressure bidirectionally, with a pressure of 2–5 MPa and a holding time of 1–5 minutes.

[0060] Then, in step D), the pre-pressed blank from step C) together with the sintering mold is placed into a spark plasma sintering device or a hot pressing sintering device, and then high-temperature sintering is performed in a vacuum or inert gas environment.

[0061] In step D), a vacuum or inert gas environment is used to prevent the carbon material from being oxidized at high temperatures. The sintering pressure in step D) is typically 5–100 MPa, and the sintering temperature is typically 1500–2000 °C.

[0062] Preferably, the sintering pressure is set to 50-80 MPa. Within this pressure range, it is possible to obtain a high-strength sintered body at a lower temperature, while applying less pressure, reducing industrial costs and facilitating mass production. At the same time, this pressure range can control the phase transformation rate of the fullerene powder and prevent excessively rapid grain growth.

[0063] The sintering temperature can be, for example, 1500℃, 1600℃, 1700℃, 1800℃, 1900℃, 2000℃, etc., or any temperature within the temperature range defined by any two of the above temperature values. Preferably, the sintering temperature is 1500~1700℃, which is beneficial for controlling the phase transformation rate of the fullerene powder and preventing excessively rapid grain growth. The sintering temperature of this invention is significantly lower than that used in traditional graphite preparation methods, and multiple sintering processes are not required, thus resulting in lower energy consumption and energy-saving and environmentally friendly effects.

[0064] The holding time during sintering is not critical and can be determined as needed, typically set to 5–60 minutes. The heating rate can also be adjusted as needed, typically set to 1–100°C / min.

[0065] In some preferred embodiments of the present invention, the sintering step in step D) is performed by evacuating to a vacuum level higher than 1×10⁻⁶. -1 After Pa, the pressure is increased to the sintering pressure. Once the sintering pressure stabilizes, the temperature is increased to the sintering temperature. After high-temperature sintering, the heating program is turned off and the pressure is released.

[0066] In some other preferred embodiments of the present invention, the sintering step in step D) is carried out in an inert gas environment, such as He, Ne, Ar, Kr, Xe, etc.

[0067] Finally, in step E), after the equipment has cooled down, the mold is removed, and the graphite-based composite material is obtained after demolding.

[0068] This invention yields a material that possesses high compressive strength (>100MPa), high flexural strength (>50MPa), and high electrical conductivity (>5×10⁻⁶ MPa). 4 This novel carbon material (S / m) can meet the stringent requirements of many special application environments, such as the aerospace industry, and has broad application prospects. Moreover, its preparation method has advantages such as high efficiency, low energy consumption, and low cost.

[0069] Example

[0070] The present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described below are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate specific embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without departing from the principles of the invention or making inventive effort are within the scope of protection of the present invention.

[0071] For the sake of simplicity, some materials, equipment, and methods commonly used in the art are not described in the examples. All processes and analytical testing procedures (and related parameters) not specifically described in the examples are performed in accordance with those commonly used by those skilled in the art; materials and equipment not specifically sourced are all conventional laboratory materials and equipment.

[0072] Raw materials, equipment and material analysis testing methods

[0073] The manufacturer information for the main raw materials and equipment used in each embodiment is as follows:

[0074] Petroleum coke: Daqing Tongwei Chemical Co., Ltd.

[0075] Asphalt: Inokai Technology Co., Ltd.

[0076] Graphite: Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0077] Fullerenes: Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences

[0078] Spark plasma sintering equipment: Sumitomo Coal Mining Co., Ltd.'s SPS-3.20MK-IV

[0079] Hot pressing sintering equipment: HIGH-MULTI-5000 from Fuji Denpa Kogyo Co., Ltd., Japan

[0080] The main analytical and detection methods and instruments used in each embodiment are as follows:

[0081] TEM: TEM samples (5×10×0.06μm) were prepared using focused ion beam (FIB) and tested using a JEM-ARM300F2 from Nippon Electronics with an accelerating voltage of 300KV.

[0082] Compressive strength measurement method: The sample was machined into a cylinder with a diameter of 3 mm and a height of 4.5 mm. The compressive strength was tested at room temperature using a mechanical property testing system (WDW-20S, TE Forcespeed, China). The indenter loading rate was set to 0.1 mm / min. -1 .

[0083] Flexural strength measurement method: The three-point bending method was used to measure the flexural strength. The flexural strength test was conducted at room temperature using a mechanical property testing system (MTII / Fullman SEMtester 2000). The specimen was machined into a cuboid of 1 mm × 2 mm × 14 mm. The span length was 11 mm, and the indenter loading rate was set to 0.1 mm·min. -1 .

[0084] Conductivity measurement method: The conductivity test was performed using the standard four-probe method under a helium atmosphere using a ZEM-3 (Ulvac-Riko, Japan) instrument. The test sample was cut into rectangular blocks of approximately 2mm × 3mm × 8mm, and the test temperature range was from room temperature to 500℃.

[0085] Example 1

[0086] A graphite-based composite material was prepared according to the following steps:

[0087] A) Mixing: Weigh 1.3g of petroleum coke and 0.1g of C. 70 The powder is ground and mixed, then added to a planetary ball mill and milled for 3 hours. The milled powder is then placed in an oven for drying. The resulting powder is sieved through a stainless steel standard sieve to obtain the precursor powder for graphite-based composite materials.

[0088] B) Pretreatment: Add the mixed powder to a toluene solution and sonicate for 30 minutes; then place the solution in a high-pressure reactor, purge with argon to 5 MPa, heat to 200°C, maintain the temperature for 48 hours, and then slowly cool and depressurize.

[0089] C) Loading: Place the precursor powder in a mold with an inner diameter of 15mm, apply pressure in both directions for pre-compression molding, the pressure is 2MPa, the holding time is 5min, and then place the pre-compressed blank into a graphite mold for sintering, with graphite paper separating the pre-compressed blank from the graphite mold.

[0090] D) Sintering: The pre-pressed billet from step B), together with the sintering mold, is placed into a spark plasma sintering apparatus for sintering. The sintering method is spark plasma sintering, and the vacuum level is evacuated to a level higher than 1×10⁻⁶. -1 After Pa, a sintering pressure of 80 MPa is applied. After the sintering pressure stabilizes, the temperature is raised to the sintering temperature at a rate of 10 °C / min. The sintering temperature is 1500 °C and the holding time is 10 min. After high-temperature sintering, the heating program is turned off and the pressure is released.

[0091] The spark plasma sintering equipment used in this embodiment is the Sumitomo Coal Mining Co., Ltd. SPS-3.20MK-IV;

[0092] E) Discharge: After the temperature inside the equipment has cooled down, remove the mold and demold to obtain a graphite-based composite material with both high strength and excellent electrical conductivity.

[0093] After preparation, various performance tests, including compressive strength and flexural strength, were performed on the test samples of the prepared product at room temperature. The test sample for compressive strength was a cylinder with a diameter of 3 mm and a height of 4.5 mm. The test sample for flexural strength was a cuboid with dimensions of 2 × 2 × 14 mm.

[0094] The graphite-based composite material prepared in this embodiment is an opaque black block, as shown in the figure below. Figure 1 As shown, the polished sample exhibits a mirror-like finish. Transmission electron microscopy (TEM) images are shown below. Figure 2 As shown in the figure, it is clear that the bulk material consists of two phases: graphite and amorphous carbon, and the graphite and amorphous carbon phases are distributed alternately.

[0095] The compressive stress-strain curve of the graphite-based composite material prepared in this embodiment is shown in the figure. Figure 3 (a) The conductivity test data curve is shown in [reference]. Figure 3 (b)

[0096] The specific performance data of the graphite-based composite material prepared in this embodiment are summarized in Table 2. The data show that the graphite-based composite material prepared in this embodiment has both high strength and excellent electrical conductivity.

[0097] Example 2

[0098] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 1. The specific process parameters that differ from those in Example 1 are shown in the Example 2 column of Table 1.

[0099] like Figure 4 (a) shows the compressive stress-strain curve of the product prepared in Example 2. Figure 4 (b) shows the conductivity data of the product prepared in Example 2. The curve exhibits obvious semiconductor characteristics, and the compressive strength is 140 MPa. The room temperature conductivity is tested to be 9.5 × 10⁻⁶. 4 S / m. Other performance data are shown in Table 2.

[0100] Example 3

[0101] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 1. The specific process parameters that differ from those in Example 1 are shown in the Example 3 column of Table 1.

[0102] like Figure 5 (a) shows the compressive stress-strain curve of the product prepared in Example 3. Figure 5 (b) shows the conductivity data of the product prepared in Example 3. The curve exhibits obvious semiconductor characteristics, and the compressive strength is 150 MPa. The room temperature conductivity is tested to be 8.5 × 10⁻⁶. 4 S / m. Other performance data are shown in Table 2.

[0103] Example 4

[0104] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 1. The specific process parameters that differ from those in Example 1 are shown in Column 4 of Table 1.

[0105] like Figure 6 (a) shows the compressive stress-strain curve of the product prepared in Example 4. Figure 6 (b) The conductivity data of the product prepared in Example 4 shown in the figure have obvious semiconductor characteristics, and the compressive strength is 220 MPa; the room temperature conductivity is 11 × 10⁻⁶. 4 S / m. Other performance data are shown in Table 2.

[0106] Example 5

[0107] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 1. The specific process parameters that differ from those in Example 1 are shown in column 5 of Table 1. Material performance data are shown in Table 2.

[0108] Comparative Example 1

[0109] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 5, but without the addition of a toughening agent. Specific process parameters differing from those in Example 5 are shown in Comparative Example 1 of Table 1. Material performance data are shown in Table 2.

[0110] Comparative Example 2

[0111] The preparation method of the graphite-based composite material in this embodiment is similar to that in Example 5, but pretreatment step B is omitted. Specific process parameters differing from those in Example 5 are shown in column 2 of Comparative Example 1 in Table 1. Material performance data are shown in Table 2.

[0112]

[0113]

[0114] As shown in Table 2, Comparative Example 1, lacking the toughening agent fullerene, exhibits significantly lower mechanical properties such as compressive strength and flexural strength compared to the other examples. While Comparative Example 2 incorporated fullerene but omitted pretreatment step B), the resulting material, though slightly better than Comparative Example 1, still falls far short of the other examples in terms of compressive strength and flexural strength. The inventors believe this is due to the absence of pretreatment step B), which prevents fullerene molecules from fully penetrating between the graphite layers of the matrix material, thus hindering the achievement of the unique alternating structure of graphite and amorphous carbon phases. In contrast, the materials obtained in each example possess high compressive strength, high flexural strength, and excellent electrical conductivity.

[0115] 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. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0116] The specification of this invention lists various optional materials for the components; however, those skilled in the art should understand that the list of components is neither limiting nor exhaustive. All components can be replaced with equivalent materials not mentioned in this specification, and the objectives of this invention can still be achieved. The specific examples mentioned in the specification are merely illustrative and not intended to limit the scope of this invention.

[0117] The combination of the matrix and sintering aid in this invention can include pairwise combinations or multiple combinations.

[0118] Furthermore, the dosage range of each component in this invention includes any combination of any lower and upper limits mentioned in the specification, as well as any range formed by combining the specific content of the component as an upper or lower limit in each specific embodiment; all these ranges are covered within the scope of this invention, but for the sake of brevity, these combined ranges are not listed one by one in the specification. Each feature of this invention listed in the specification can be combined with any other feature of this invention, and such combinations are also within the scope of disclosure of this invention; for the sake of brevity, these combined ranges are not listed one by one in the specification.

Claims

1. A graphite-based composite material, characterized in that: The structure of the graphite-based composite material includes a graphite phase and an amorphous carbon phase; wherein the graphite phase and the amorphous carbon phase are alternately distributed, and the width of the graphite phase does not exceed 200 nm, and the width of the amorphous carbon phase does not exceed 50 nm.

2. The graphite-based composite material as described in claim 1, characterized in that: Its flexural strength is not less than 50 MPa, its compressive strength is not less than 100 MPa, and its electrical conductivity is not less than 5 × 10⁻⁶ MPa. 4 S / m.

3. The graphite-based composite material as described in claim 1, characterized in that... The graphite-based composite material is prepared by a method comprising the following steps: using petroleum coke, pitch, graphite or a mixture thereof as matrix raw materials, adding fullerene powder or the like as sintering aids, grinding and uniformly mixing to obtain precursor powder, wherein the mass ratio of sintering aid to matrix raw materials is 0.005:1 to 0.6:1; and sintering the precursor powder under pressure and high temperature in a protective atmosphere or vacuum to obtain the graphite-based composite material.

4. A method for preparing a graphite-based composite material, characterized in that... Includes the following steps: A) Using petroleum coke, pitch, graphite or a mixture thereof as the matrix raw material, and fullerene as the sintering aid, the two are ground and uniformly mixed to obtain a precursor powder, wherein the mass ratio of the sintering aid to the matrix raw material is 0.005:1 to 0.6:

1. B) Disperse the precursor powder in an organic solvent, and then treat the resulting precursor powder dispersion in an inert atmosphere at a temperature above 100°C and a pressure above 4MPa for at least 12 hours. C) After removing the solvent from the precursor powder dispersion in step B), the dried powder is loaded into a mold, pre-pressed, and the pre-pressed green body is placed into a sintering mold. D) Place the pre-pressed billet from step C) together with the sintering mold into a spark plasma sintering equipment or a hot pressing sintering equipment, and then sinter it in a vacuum or inert gas environment. E) After cooling, remove the mold and demold to obtain the graphite-based composite material.

5. The method for preparing the amorphous carbon-based composite material according to claim 4, characterized in that: In step A), the petroleum coke, pitch, graphite, or mixtures thereof undergo a carbonization transformation at high temperatures to become graphite; the fullerenes in step A) include C 60 C 70 C 84 C 120 And their mixtures, which transform into amorphous carbon at high temperatures.

6. The method for preparing the graphite-based composite material according to claim 4, characterized in that, Step A) is achieved by grinding and mixing petroleum coke, asphalt, graphite or a mixture thereof with fullerene, loading the mixture into a planetary ball mill for mixing, and then sieving the resulting powder to obtain the precursor powder.

7. The method for preparing the graphite-based composite material according to any one of claims 4 to 6, characterized in that: In step C), the pre-compression molding is performed by applying pressure in both directions. The preferred pressure is 2 to 5 MPa, and the preferred holding time is 0.1 to 10 min.

8. The method for preparing the graphite-based composite material according to any one of claims 4 to 6, characterized in that: In step D), the sintering pressure applied is 5–100 MPa, and the sintering temperature is 1500–2000 °C; preferably, the sintering pressure is 50–80 MPa, the sintering temperature is 1500–1700 °C, the heating rate is 1–100 °C / min, and the holding time is 5–60 min.

9. The method for preparing the graphite-based composite material according to any one of claims 4 to 6, characterized in that: In step D), the sintering step involves first applying initial pressure and then evacuating to a vacuum level higher than 1×10⁻⁶. -1 After Pa, sintering pressure is applied, and after the sintering pressure stabilizes, the temperature is raised to the sintering temperature. After high-temperature sintering, the heating program is turned off, and the temperature is rapidly cooled and the pressure is released.

10. The method for preparing the graphite-based composite material according to any one of claims 4 to 6, characterized in that: The mass ratio of sintering aid to matrix raw material in step A) is 0.02:1 to 0.5:1, preferably 0.03:1 to 0.45:1.

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