Porous graphite material with adjustable pores and preparation method thereof

Abstract

The invention provides a pore-adjustable porous graphite material and a preparation method thereof, and belongs to the technical field of porous graphite materials. The preparation method comprises the steps of pore forming agent treatment, material mixing, forming, roasting, pore forming and graphitization. The pore-forming agent treatment step comprises the following steps: mixing metal powder and graphite powder, then putting the mixture into a ball mill, carrying out ball-milling treatment in an argon atmosphere, then vacuumizing, raising the temperature to 400-900 DEG C, treating for 0.5-5.0 hours, and carrying out vibration screening to remove redundant graphite powder so as to obtain pore-forming agent powder; the prepared porous graphite material is adjustable in porosity and pore size, high in strength and excellent in stability.

Description

Technical Field

[0001] The invention belongs to the technical field of porous graphite materials, and in particular relates to a porous graphite material with adjustable pores and a preparation method thereof. Background Art

[0002] In recent years, with the development of new energy, environmental protection and efficient energy storage technology, the demand for high-performance porous materials has increased. Due to their unique physical and chemical properties, porous materials have shown broad application prospects in catalysis, adsorption, energy storage, filtration and other fields.

[0003] Porous graphite material is a kind of porous material with carbon element as the skeleton and different pore sizes and porosities. Porous graphite material has excellent properties such as large specific surface area, high temperature stability and high corrosion resistance, and is widely used in important fields such as semiconductors, aerospace, new energy, and nuclear industry.

[0004] The large specific surface area of ​​porous graphite materials enables them to be used in sewage treatment to adsorb heavy metal ions, organic pollutants, etc. in water, providing strong support for environmental protection; its excellent high-temperature stability enables it to play an important role in electronic equipment and industrial fields, and it can effectively withstand high temperatures and better ensure the stable operation of equipment; its high corrosion resistance makes it irreplaceable in highly corrosive environments.

[0005] At present, porous graphite materials are prepared by the pore-forming agent method, and the production process mainly includes steps such as raw material mixing, molding, roasting, and graphitization. During the high-temperature roasting process, the pore-forming agent will decompose and volatilize, leaving pores inside the green body, thereby obtaining a porous graphite material. Porous graphite materials with different porosities, pore sizes, and pore size distributions can be prepared by adjusting parameters such as the type, particle size, and addition amount of the pore-forming agent, and have the advantages of low cost in terms of raw material composition and equipment.

[0006] The types of pore formers in the prior art include organic pore formers and inorganic pore formers; Organic pore formers mainly include starch, cellulose, polyvinyl alcohol, plastic particles, synthetic resins, etc. They are widely available and relatively cheap. However, organic pore formers will produce a large amount of gas during the decomposition process, which will lead to unstable pore structure, pore collapse, poor penetration, etc., thus affecting the strength performance of porous graphite materials. Inorganic pore formers mainly include various salts, metal oxides, etc. The properties of inorganic pore formers are relatively stable, which is conducive to uniform mixing with other components. However, some impurities will remain in the inorganic pore formers after calcination and are difficult to remove, which will eventually affect the strength and other properties of the porous graphite material.

[0007] From the above, we can see that, on the one hand, no matter what kind of pore-forming agent is used, the pores are generated during the roasting process, and their shape and size are difficult to control, the pore size distribution is wide, and the skeleton structure formed by the aggregate is easily destroyed by the pore-forming agent, resulting in low strength of the graphite material; on the other hand, a series of changes occur in the aggregate and binder components during the roasting process, which will also affect the pore shape and pore size distribution, making it difficult to customize the pore specifications.

[0008] CN117700254A discloses a method and system for preparing three-dimensional mesh through-hole graphite, specifically, first preparing a three-dimensional mesh metal skeleton template, then mixing and kneading aggregates and binders into the mesh metal skeleton for pressing and molding to obtain a graphite raw product; electrolyzing the graphite raw product to remove the pore template formed by the mesh metal skeleton, and then calcining and graphitizing to obtain a graphite product; This patent is mainly used to produce through-pored graphite with a three-dimensional network distribution. During the preparation process, the network metal skeleton is large in size and has a small contact area with aggregates and binders, thereby ensuring that it can fully contact with the electrolyte during the subsequent electrolysis process and effectively remove the three-dimensional network metal skeleton, so that the graphite products have better and larger-sized network through holes; but due to the ductility of the metal, the diameter of the produced metal skeleton is large, and the corresponding pore size of the prepared graphite products is limited; while the aggregates and binders fill the network metal skeleton, the shapes of other pores produced by the accumulation are random and cannot be finely controlled.

[0009] In order to regulate the pores, the researchers found that metal powder can be used as a pore-forming agent; however, when using metal powder as a pore-forming agent, the contact area with the aggregate and binder is large during the mixing process, and the contact area between the pore-forming agent and the electrolyte is small during electrolysis, making it difficult to ensure efficient removal of the pore-forming agent during the electrolysis process, thereby affecting the porosity and pore size. In addition, when using metal powder as a pore-forming agent, the strength of the graphite material produced is relatively low.

[0010] Therefore, developing a porous graphite material with adjustable pores and a preparation method thereof, using a pore-forming agent method to control a specific porosity and pore size, and making the prepared porous graphite material have the characteristics of high strength and high consistency are problems that need to be urgently solved in the prior art. Summary of the invention

[0011] In order to solve the existing technical problems, the present invention provides a porous graphite material with adjustable pores and a preparation method thereof. By adopting a metal pore-forming agent method, a specific porosity and pore size can be controlled. The porous graphite material prepared in this way has high strength and excellent stability.

[0012] In view of the above technical problems, the present invention adopts the following technical solutions: A method for preparing a porous graphite material with adjustable pores, comprising the steps of pore forming agent treatment, material mixing, molding, calcination, pore formation and graphitization, and the specific operations are as follows: 1. Pore forming agent treatment The metal powder and the graphite powder are mixed, and then put into a ball mill for ball milling in an argon atmosphere for 15-60 minutes. After the ball milling, the vacuum is evacuated to -0.10--0.20MPa, the temperature is increased to 400-900°C, and the heat treatment is carried out for 0.5-5.0 hours. After the heat treatment is completed, the excess graphite powder is removed by cooling and vibration screening to obtain a pore-forming agent powder. The volume ratio of the metal powder to the graphite powder is 1:1-3; The metal powder is one or more of iron powder, nickel powder, copper powder and aluminum powder, and the particle size of the metal powder is 10-100 μm; The particle size of the graphite powder is 1-100 μm.

[0013] 2. Mixing Put asphalt, aggregate and pore-forming agent powder into a kneading device, heat until the asphalt is melted, mix evenly, and obtain a mixture; The asphalt has a softening point of 70-100°C and a particle size of 10-100 μm; The volume ratio of the aggregate, asphalt and pore-forming agent powder is 10:2-5:2.0-4.5; The aggregate is one or more of artificial graphite, asphalt coke, carbon black and natural graphite, and the particle size of the aggregate is 10-100 μm.

[0014] 3. Molding The mixed material is subjected to dry pressing, hot pressing or isostatic pressing at a molding pressure of 20-200 MPa to obtain a green body.

[0015] 4. Roasting The green body is placed in a roasting furnace for roasting. The roasting atmosphere is argon gas. The roasting temperature is 600-1200°C. The heating rate is 6-12°C / min. The roasting time is 15-22h. After the roasting is completed, it is cooled to room temperature to obtain a roasted product.

[0016] 5. Hole making The calcined product is connected to the positive electrode of the power supply, and the carbon rod is connected to the negative electrode of the power supply. The positive electrode and the negative electrode are completely immersed in the mixed solution of the electrolyte and the additive. The DC power supply is powered on, and the voltage of the DC power supply is controlled to be 2.0-10.0V until the negative electrode no longer precipitates metal, and a pore-forming product is obtained; The mass ratio of the electrolyte to the additive is 100:0.5-3.0; The electrolyte is one of ferrous sulfate solution, sodium nitrate solution or metal salt solution of the metal used, and the mass concentration of the electrolyte is 10-65%; The additive is one of polyethylene glycol, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0017] 6. Graphitization The porous product is dried and placed in a graphitization furnace for graphitization treatment in an argon atmosphere at a graphitization temperature of 2400-2900° C. for 8-20 hours. The porous graphite material is obtained after naturally recovering to room temperature.

[0018] A porous graphite material with adjustable pores is prepared by the above-mentioned preparation method.

[0019] The present invention adopts asphalt coke, petroleum coke, artificial graphite powder and the like as aggregate, asphalt as binder, treated metal powder as pore-forming agent, and mixes them in a certain proportion to prepare porous graphite matrix raw materials, and obtains porous graphite products through mixing, molding, roasting, pore-forming and graphitization processes; the treated metal powder exists stably as pore-forming agent powder, and can be completely fixed and retained in the green body during the roasting process, and its volume, shape and particle size will not change; the pore-forming agent powder can have a good contact surface with the aggregate and the binder, thereby ensuring the formation of a good current path during subsequent electrolysis , improving the electrolysis efficiency; the pore size and shape of the pores formed after the pore-forming agent is removed are consistent with the pore-forming agent particle size, forming a pore structure with a specific porosity and pore size, and the size and shape of the pores of the final product can be controlled by adjusting the metal powder particle size, avoiding changes in the pore structure caused by drastic temperature changes in the roasting process; in the process of electrolytic pore formation, the additive improves the wettability of graphite and electrolyte, ensuring the efficient and complete removal of the pore-forming agent by subsequent electrolysis, and finally achieving the porosity and pore size of the porous graphite material while improving the strength performance of the porous graphite material.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing porous graphite material of the present invention has adjustable porosity and pore size, the volume ratio of pore-forming agent powder to aggregate is 20-45%, the particle size of metal powder is 10-100 μm, the porosity of the prepared product is 30-50%, the pore size is 10-100 μm, the flexural strength is 15-45 MPa, and the compressive strength is 31-110 MPa. DETAILED DESCRIPTION

[0021] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0022] Example 1 1. Pore forming agent treatment The metal powder and the graphite powder are mixed, and then put into a ball mill for ball milling in an argon atmosphere for 60 minutes. After the ball milling, the vacuum is evacuated to -0.15MPa, the temperature is increased to 900°C, and the heat treatment is carried out for 5.0 hours. After the heat treatment is completed, the excess graphite powder is removed by cooling and vibration screening to obtain a pore-forming agent powder. The volume ratio of the metal powder to the graphite powder is 1:1; The metal powder is a mixed powder of iron powder and nickel powder, and the mass ratio of the iron powder to the nickel powder is 1:1; The particle size of the metal powder is 10 μm; The graphite powder has a particle size of 50 μm.

[0023] 2. Mixing Put asphalt, aggregate and pore-forming agent powder into a kneading device, heat until the asphalt is melted, mix evenly, and obtain a mixture; The asphalt has a softening point of 75°C and a particle size of 50 μm; The volume ratio of the aggregate to asphalt and pore-forming agent powder is 10:3:2.0; The aggregate is artificial graphite powder with a particle size of 40 μm.

[0024] 3. Molding The mixed material is dry-pressed at a pressure of 20 MPa to obtain a green body.

[0025] 4. Roasting The green body is placed in a roasting furnace for roasting. The roasting atmosphere is argon, the roasting temperature is 1200°C, the heating rate is 10°C / min, the roasting time is 15h, and after the roasting is completed, it is cooled to room temperature to obtain a roasted product.

[0026] 5. Hole making The calcined product is connected to the positive electrode of the power supply, and the carbon rod is connected to the negative electrode of the power supply. The positive electrode and the negative electrode are completely immersed in the mixed solution of the electrolyte and polyethylene glycol 200. The DC power supply is powered on, and the voltage of the DC power supply is controlled to be 5.0V until the negative electrode no longer precipitates metal, thereby obtaining a pore-forming product; The mass ratio of the electrolyte to polyethylene glycol 200 is 100:3.0; The electrolyte is a 65wt% ferrous sulfate solution.

[0027] 6. Graphitization The porous product is dried and placed in a graphitization furnace for graphitization treatment in an argon atmosphere at a graphitization temperature of 2400° C. for 8 hours. After naturally returning to room temperature, a porous graphite material is obtained.

[0028] Example 2 1. Pore forming agent treatment The metal powder and the graphite powder are mixed, and then put into a ball mill for ball milling in an argon atmosphere for 15 minutes. After the ball milling, the vacuum is evacuated to -0.20MPa, the temperature is increased to 400°C, and the heat treatment is carried out for 3.0 hours. After the heat treatment is completed, the excess graphite powder is removed by cooling and vibration screening to obtain a pore-forming agent powder. The volume ratio of the metal powder to the graphite powder is 1:3; The metal powder is copper powder with a particle size of 100 μm; The graphite powder has a particle size of 1 μm.

[0029] 2. Mixing Put asphalt, aggregate and pore-forming agent powder into a kneading device, heat until the asphalt is melted, mix evenly, and obtain a mixture; The asphalt has a softening point of 70°C and a particle size of 10 μm; The volume ratio of the aggregate to asphalt and pore-forming agent powder is 10:2:3.5; The aggregate is a mixture of carbon black and asphalt coke, the mass ratio of the carbon black to the asphalt coke is 1:1, and the particle size of the aggregate is 10 μm.

[0030] 3. Molding The mixed material is hot-pressed at a molding pressure of 200 MPa to obtain a green body.

[0031] 4. Roasting The green body was placed in a baking furnace for baking. The baking atmosphere was argon. The baking temperature was 700°C. The heating rate was 6°C / min. The baking time was 22h. After the baking was completed, it was cooled to room temperature to obtain a baked product.

[0032] 5. Hole making The calcined product is connected to the positive electrode of the power supply, and the carbon rod is connected to the negative electrode of the power supply. The positive electrode and the negative electrode are completely immersed in the mixed solution of the electrolyte and sodium dodecyl sulfate. The DC power supply is powered on, and the voltage of the DC power supply is controlled to 2.0V until the negative electrode no longer precipitates metal, thereby obtaining a pore-forming product; The mass ratio of the electrolyte to sodium dodecyl sulfate is 100:1.0; The electrolyte is a 10wt% cupric chloride solution.

[0033] 6. Graphitization The porous product is dried and placed in a graphitization furnace for graphitization treatment in an argon atmosphere at a graphitization temperature of 2600° C. for 20 h. After naturally returning to room temperature, a porous graphite material is obtained.

[0034] Example 3 1. Pore forming agent treatment The metal powder and the graphite powder are mixed, and then put into a ball mill for ball milling in an argon atmosphere for 40 minutes. After the ball milling, the vacuum is evacuated to -0.10MPa, the temperature is increased to 400°C, and the heat treatment is carried out for 0.5h. After the heat treatment is completed, the excess graphite powder is removed by cooling and vibration screening to obtain a pore-forming agent powder. The volume ratio of the metal powder to the graphite powder is 1:2; The metal powder is aluminum powder with a particle size of 50 μm; The graphite powder has a particle size of 100 μm.

[0035] 2. Mixing Put asphalt, aggregate and pore-forming agent powder into a kneading device, heat until the asphalt is melted, mix evenly, and obtain a mixture; The asphalt has a softening point of 100°C and a particle size of 100 μm; The volume ratio of the aggregate to asphalt and pore-forming agent powder is 10:5:4.5; The aggregate is natural graphite, and the particle size of the aggregate is 100 μm.

[0036] 3. Molding The mixed material is isostatically pressed at a molding pressure of 130 MPa to obtain a green body.

[0037] 4. Roasting The green body is placed in a roasting furnace for roasting. The roasting atmosphere is argon, the roasting temperature is 600°C, the heating rate is 12°C / min, the roasting time is 20h, and after the roasting is completed, it is cooled to room temperature to obtain a roasted product.

[0038] 5. Hole making The calcined product is connected to the positive electrode of the power supply, and the carbon rod is connected to the negative electrode of the power supply. The positive electrode and the negative electrode are completely immersed in the mixed solution of the electrolyte and sodium dodecylbenzene sulfonate. The DC power supply is powered on, and the voltage of the DC power supply is controlled to be 10.0V until the negative electrode no longer precipitates metal, thereby obtaining a pore-forming product; The mass ratio of the electrolyte to sodium dodecylbenzene sulfonate is 100:0.5; The electrolyte is a 30wt% sodium nitrate solution.

[0039] 6. Graphitization The porous product was dried and placed in a graphitization furnace for graphitization treatment in an argon atmosphere at a graphitization temperature of 2900° C. for 9.0 h. After naturally returning to room temperature, a porous graphite material was obtained.

[0040] The porosity, pore size, and strength properties of the porous graphite materials obtained in Examples 1-3 were tested as follows:

[0041] Unless otherwise specified, all ratios and percentages described in the present invention are by mass ratios and percentages are by mass percentages.

[0042] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a porous graphite material with adjustable pores, characterized in that: It includes the steps of pore forming agent treatment, material mixing, molding, calcination, pore forming and graphitization; The pore-forming agent treatment step comprises mixing metal powder and graphite powder, then putting them into a ball mill, performing ball milling treatment under an argon atmosphere, then evacuating, raising the temperature to 400-900° C. for 0.5-5.0 h, and removing excess graphite powder by vibration screening to obtain pore-forming agent powder; The pore-forming agent powder is processed through the steps of mixing, molding and calcining to obtain a calcined product; The pore-forming step comprises: connecting the calcined product to the positive electrode of the power supply, connecting the carbon rod to the negative electrode of the power supply, completely immersing the positive electrode and the negative electrode in a mixed solution of the electrolyte and the additive, and turning on the DC power supply, controlling the voltage of the DC power supply to be 2.0-10.0V, until the negative electrode no longer precipitates metal, and obtaining the pore-forming product; The electrolyte is one of ferrous sulfate solution, sodium nitrate solution or metal salt solution of the metal used.

2. The method for preparing a porous graphite material with adjustable pores according to claim 1, characterized in that: The pore-forming agent treatment step comprises: mixing metal powder and graphite powder, and then putting them into a ball mill for ball milling in an argon atmosphere for 15-60 minutes. After the ball milling, evacuating to -0.10 to -0.20 MPa, raising the temperature to 400-900° C., and heat-insulating for 0.5-5.0 hours. After the heat-insulating, cooling, vibrating and screening to remove excess graphite powder, and obtaining pore-forming agent powder.

3. The method for preparing a porous graphite material with adjustable pores according to claim 2, characterized in that: The volume ratio of the metal powder to the graphite powder is 1:1-3; The metal powder is one or more of iron powder, nickel powder, copper powder and aluminum powder, and the particle size of the metal powder is 10-100 μm; The particle size of the graphite powder is 1-100 μm.

4. The method for preparing a porous graphite material with adjustable pores according to claim 1, characterized in that: The mixing step comprises putting asphalt, aggregate and pore-forming agent powder into a kneading device, heating until the asphalt is melted, and mixing evenly to obtain a mixture; The asphalt has a softening point of 70-100°C and a particle size of 10-100 μm; The volume ratio of the aggregate, asphalt and pore-forming agent powder is 10:2-5:2.0-4.5; The aggregate is one or more of artificial graphite, asphalt coke, carbon black and natural graphite, and the particle size of the aggregate is 10-100 μm.

5. The method for preparing a porous graphite material with adjustable pores according to claim 4, characterized in that: The molding step is to dry press, hot press or isostatic press the mixed material, with a molding pressure of 20-200 MPa to obtain a green body.

6. The method for preparing a porous graphite material with adjustable pores according to claim 5, characterized in that: The calcining step comprises placing the green body in a calcining furnace for calcining, wherein the calcining atmosphere is argon, the calcining temperature is 600-1200° C., the heating rate is 6-12° C. / min, the calcining time is 15-22 hours, and after the calcining is completed, the green body is cooled to room temperature to obtain a calcined product.

7. The method for preparing a porous graphite material with adjustable pores according to claim 1, characterized in that: In the pore-forming step, the mass ratio of the electrolyte to the additive is 100:0.5-3.0; The mass concentration of the electrolyte is 10-65%; The additive is one of polyethylene glycol, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

8. The method for preparing a porous graphite material with adjustable pores according to claim 1, characterized in that: The graphitization step is to put the pore-forming product into a graphitization furnace after drying, and perform graphitization treatment under an argon atmosphere, the graphitization temperature is 2400-2900° C., the graphitization time is 8-20 hours, and the porous graphite material is obtained after naturally recovering to room temperature.

9. A porous graphite material with adjustable pores obtained according to the preparation method according to any one of claims 1 to 8.

Images