A method for preparing porous graphite products with complex structures

Abstract

This invention provides a method for preparing porous graphite products with complex structures, relating to the field of porous graphite products. The method includes the following steps: preparing a binder, bonding treatment, and sintering treatment. This method for preparing porous graphite products with complex structures can effectively prepare porous graphite products with different complex structures using existing production equipment and processes; it also improves the compatibility between porous graphite materials and binders, effectively increasing the shear strength of the prepared porous graphite products with complex structures; and further improves the poor stability of porous graphite products under high-temperature environments, enabling them to maintain good shear strength and corrosion resistance for a long time in high-temperature environments.

Description

Technical Field

[0001] This invention relates to the field of porous graphite products, and in particular to a method for preparing porous graphite products with complex structures. Background Technology

[0002] Graphite materials possess numerous excellent properties, including electrical and thermal conductivity, high temperature resistance, high plasticity, and chemical stability, leading to a wide range of applications. Initially, graphite's electrical conductivity and high-temperature resistance were primarily utilized in the metallurgical industry. However, with the deepening of research into graphite materials, porous graphite products prepared from calcined coke have found significant applications in aerospace, military, automotive, electronics, nuclear energy, and metallurgy due to their superior corrosion resistance, radiation resistance, self-lubrication, high and low temperature resistance, ease of processing, and lightweight properties.

[0003] However, with the continuous expansion of applications of porous graphite materials, the problem of the limited application of porous graphite products due to their simple structure has also become apparent. Under existing technological conditions, due to limitations such as molding dies and production processes, it is difficult to prepare porous graphite products with complex structures that meet predetermined requirements. How to effectively prepare porous graphite products with different complex structures using existing production equipment and processes is an important technical problem that urgently needs to be solved.

[0004] In the process of developing complex-structured porous graphite products using existing production equipment and processes, the inventors discovered that due to the unique high-porosity microporous structure of porous graphite, its compatibility with binders is poor, resulting in unsatisfactory shear strength in the prepared porous graphite products, making effective optimization impossible. Furthermore, this also leads to poor stability of the prepared porous graphite products under high-temperature environments, failing to maintain good shear strength and corrosion resistance over long periods at high temperatures, thus hindering the further expansion of the applications of porous graphite products. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for preparing porous graphite products with complex structures. This method can effectively prepare porous graphite products with different complex structures using existing production equipment and processes. Simultaneously, it improves the compatibility between porous graphite materials and binders, effectively increasing the shear strength of the prepared porous graphite products with complex structures. Furthermore, it improves the poor stability of porous graphite products under high-temperature environments, enabling them to maintain good shear strength and corrosion resistance for extended periods in high-temperature environments.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing porous graphite products with complex structures includes the following steps: preparing a binder, bonding treatment, and sintering treatment;

[0008] The method for preparing the adhesive is as follows: Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate are mixed evenly to obtain a premix; the premix is ​​spray-dried and heat-treated to obtain a heat-treated material; the heat-treated material is added to an ethanol-water solution containing γ-aminopropyltriethoxysilane, and after stirring and modification, a modified material is obtained; the modified material is mixed evenly with phenolic resin, furan resin, and anhydrous ethanol to obtain the adhesive.

[0009] The bonding process involves mixing phenolic resin and epoxy resin and coating the mixture onto the bonding surface of the porous graphite block. After heat treatment, adhesive is applied to the bonding surface of the porous graphite block. After bonding the bonding surfaces of two or more porous graphite blocks together, pressure is applied to fix the mixture and a fixed body is obtained.

[0010] The fixed body is sintered to obtain a porous graphite product with a complex structure.

[0011] Preferably, in the preparation of the premix, the weight ratio of carbon powder to boron carbide is 3-7:3-7;

[0012] The weight of anhydrous ethanol is 30-50% of the total weight of carbon powder and boron carbide;

[0013] The weight of polyethylene glycol is 0.1-5% of the total weight of carbon powder and boron carbide;

[0014] The weight of stearic acid is 0.1-3% of the total weight of carbon powder and boron carbide;

[0015] The weight of polyvinylpyrrolidone is 0.1-2% of the total weight of carbon powder and boron carbide;

[0016] The weight of sodium dodecyl sulfate is 0.1-2% of the total weight of carbon powder and boron carbide.

[0017] Preferably, in the preparation of the adhesive, the inlet temperature of the spray drying is controlled to be 150-180℃, the outlet temperature to be 80-100℃, the spray pressure to be 0.1-1 MPa, and the feed rate to be 70-100 L / h.

[0018] Preferably, in the preparation of the adhesive, the heat treatment temperature is 100-400℃ and the heat treatment time is 10-20h.

[0019] Preferably, in the preparation of the adhesive, the weight of γ-aminopropyltriethoxysilane is 0.5-3% of the weight of the heat-treated material;

[0020] The weight of the ethanol-water solution is 1.6-1.9 times the weight of the heat-treated material;

[0021] The volume concentration of the aqueous ethanol solution is 90-95%.

[0022] Preferably, in the preparation of the adhesive, the solid content of the phenolic resin is 40-60 wt%, and the solid content of the furan resin is 40-60 wt%.

[0023] The weight ratio of phenolic resin to furan resin is 1-3:1-3;

[0024] The weight of the modified material is 10-50% of the total weight of phenolic resin and furan resin;

[0025] The weight of anhydrous ethanol is 2-10 times the total weight of phenolic resin and furan resin.

[0026] Furthermore, in the bonding process, before coating the porous graphite block with a mixture of phenolic resin and epoxy resin, the porous graphite block is first ultrasonically cleaned with deionized water.

[0027] The ultrasonic cleaning frequency is 40-60 kHz, and the ultrasonic cleaning temperature is 40-70℃.

[0028] Preferably, in the bonding process, the solid content of the phenolic resin is 40-60 wt%, and the solid content of the epoxy resin is 50-60 wt%.

[0029] The weight ratio of phenolic resin to epoxy resin is 5-7:3-5;

[0030] The resin coating thickness on the bonding surface of the porous graphite block is 0.5-1mm;

[0031] The adhesive coating thickness on the bonding surface of the porous graphite block is 0.5-2 mm.

[0032] Preferably, in the bonding process, the heat treatment temperature is 300-700℃ and the heat treatment time is 5-100h;

[0033] The applied pressure is fixed at 5-10 MPa.

[0034] Furthermore, the sintering process is as follows: the fixture is heated from room temperature to 200℃ at a heating rate of 1-5℃ / min in an environment with a vacuum degree of 5-100 Pa, and then sintered at that temperature for 30-200 min; the temperature is then further increased from 200℃ to 500℃ and sintered at that temperature for 30-300 min; the temperature is then further increased from 500℃ to 800-1200℃ and sintered at that temperature for 60-300 min, thus completing the sintering process.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The method for preparing complex-structured porous graphite products of the present invention firstly mixes carbon powder, boron carbide with polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate to prepare a premix, and then spray-dries and heat-treats the premix to obtain a heat-treated material; the heat-treated material is modified with γ-aminopropyltriethoxysilane to obtain a modified material; the modified material is mixed evenly with phenolic resin, furan resin, and anhydrous ethanol to obtain an adhesive; then, a mixture of phenolic resin and epoxy resin and the adhesive are sequentially coated onto the bonding surface of the porous graphite block, and then sintered to obtain a porous graphite product with a complex structure; the aforementioned technical means cooperate with each other and work synergistically, which can effectively prepare porous graphite products with different complex structures using existing production equipment and processes; and at the same time improve the compatibility between porous graphite materials and adhesives, effectively improve the shear strength of the prepared complex-structured porous graphite products; and further improve the poor stability of porous graphite products in high-temperature environments, so that they can maintain good shear strength and corrosion resistance in high-temperature environments for a long time.

[0037] (2) The method of preparing complex porous graphite products according to the present invention can achieve a shear strength of up to 30 MPa at the bonding joint of the prepared porous graphite products; at the same time, after the porous graphite products are left to stand in a temperature environment of 1000℃ for 1000h, the shear strength at the bonding joint of the porous graphite products can still be maintained at 15 MPa.

[0038] (3) The method for preparing complex porous graphite products of the present invention has readily available raw materials, simple process, safe and controllable operation, and is suitable for large-scale industrial production. Detailed Implementation

[0039] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] To address the aforementioned technical problems of this invention, embodiments of this invention provide a method for preparing porous graphite products with complex structures, comprising the following steps: preparing a binder, bonding treatment, and sintering treatment;

[0042] The method for preparing the adhesive is as follows: Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate are mixed evenly to obtain a premix; the premix is ​​spray-dried and heat-treated to obtain a heat-treated material; the heat-treated material is added to an ethanol-water solution containing γ-aminopropyltriethoxysilane, and after stirring and modification, a modified material is obtained; the modified material is mixed evenly with phenolic resin, furan resin, and anhydrous ethanol to obtain the adhesive.

[0043] The bonding process involves mixing phenolic resin and epoxy resin and coating the mixture onto the bonding surface of the porous graphite block. After heat treatment, adhesive is applied to the bonding surface of the porous graphite block. After bonding the bonding surfaces of two or more porous graphite blocks together, pressure is applied to fix the mixture and a fixed body is obtained.

[0044] The fixed body is sintered to obtain a porous graphite product with a complex structure.

[0045] This invention first mixes carbon powder, boron carbide, polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate to prepare a premix, which is then spray-dried and heat-treated to obtain a heat-treated material. The heat-treated material is then modified with γ-aminopropyltriethoxysilane to obtain a modified material. This modified material is then uniformly mixed with phenolic resin, furan resin, and anhydrous ethanol to obtain an adhesive. Subsequently, a mixture of phenolic resin and epoxy resin, along with the adhesive, is sequentially applied to the bonding surfaces of porous graphite blocks. After sintering, a porous graphite product with a complex structure is obtained. All the aforementioned processing methods (such as spray drying, heat treatment, coating, and sintering) can be implemented using existing production equipment and processes. By dividing the complex porous graphite product into multiple bondable porous graphite blocks, and then bonding them together in a modular fashion using specific adhesives and processes, the final complex structure can be formed. This effectively overcomes the limitations of traditional mold forming and its processes. It also allows for the flexible preparation of porous graphite products with various complex structures according to requirements.

[0046] Meanwhile, to improve the compatibility between porous graphite materials and adhesives, carbon powder and boron carbide, which are highly compatible with the porous graphite matrix, are selected in combination with phenolic resin and furan resin to reduce the internal stress at the bonding interface of porous graphite and improve compatibility. Furthermore, by modifying the heat-treated materials with γ-aminopropyltriethoxysilane, the interfacial bonding between the modified materials and phenolic resin and furan resin is improved, ensuring that they are transformed into a high-strength glassy carbon phase / reinforced particle composite during subsequent sintering, thereby significantly improving the shear strength at the bonding interface of the porous graphite blocks.

[0047] Furthermore, during the bonding process, phenolic resin and epoxy resin are used as a base coat to fully impregnate and penetrate into the micropores on the surface of porous graphite. After heat treatment and curing, a transition layer with good bonding with the porous graphite matrix is ​​formed, increasing the effective bonding surface area. Then, an adhesive is applied to ensure that the adhesive bonds efficiently with the porous graphite surface. Finally, the fixing body is sintered, and the material at the bonding surface is completely carbonized to form a glassy carbon network with carbon powder and boron carbide reinforcing components, which further improves the interfacial bonding, improves the shear strength of the material, and effectively overcomes the poor stability of porous graphite products in high-temperature environments, improving their long-term stability in high-temperature environments.

[0048] To better promote the synergistic effect of carbon powder, boron carbide, and other technical means, in this embodiment of the invention, the weight ratio of carbon powder to boron carbide is 3-7:3-7; the weight of anhydrous ethanol is 30-50% of the total weight of carbon powder and boron carbide; the weight of polyethylene glycol is 0.1-5% of the total weight of carbon powder and boron carbide; the weight of stearic acid is 0.1-3% of the total weight of carbon powder and boron carbide; the weight of polyvinylpyrrolidone is 0.1-2% of the total weight of carbon powder and boron carbide; and the weight of sodium dodecyl sulfate is 0.1-2% of the total weight of carbon powder and boron carbide.

[0049] In this embodiment of the invention, considering the characteristics of the premixed material, the inlet temperature of the spray drying is controlled at 150-180℃, the outlet temperature at 80-100℃, the spray pressure at 0.1-1 MPa, and the feed rate at 70-100 L / h; the heat treatment temperature is 100-400℃, and the heat treatment time is 10-20 h.

[0050] To better improve the modification effect of γ-aminopropyltriethoxysilane on heat-treated materials, in the embodiments of the present invention, the weight of γ-aminopropyltriethoxysilane is 0.5-3% of the weight of the heat-treated material; the weight of the ethanol aqueous solution is 1.6-1.9 times the weight of the heat-treated material; and the volume concentration of the ethanol aqueous solution is 90-95%.

[0051] To better improve the compatibility of the raw materials, in this embodiment of the invention, the solid content of phenolic resin is 40-60 wt%, and the solid content of furan resin is 40-60 wt%; the weight ratio of phenolic resin to furan resin is 1-3:1-3; the weight of the modified material is 10-50% of the total weight of phenolic resin and furan resin; and the weight of anhydrous ethanol is 2-10 times the total weight of phenolic resin and furan resin.

[0052] To facilitate the application of phenolic resin and adhesive during the bonding process, ensure the coating effect, and avoid interference from impurities, in this embodiment of the invention, before applying the mixture of phenolic resin and epoxy resin to the bonding surface of the porous graphite block, the porous graphite block is first ultrasonically cleaned with deionized water; the ultrasonic cleaning frequency is 40-60 kHz, and the ultrasonic cleaning temperature is 40-70°C.

[0053] To improve the coordination between the transition layer and the adhesive layer at the bonding surface of porous graphite, in this embodiment of the invention, the solid content of phenolic resin is 40-60 wt%, and the solid content of epoxy resin is 50-60 wt%; the weight ratio of phenolic resin to epoxy resin is 5-7:3-5; the coating thickness of resin on the bonding surface of porous graphite blocks is 0.5-1 mm; and the coating thickness of adhesive on the bonding surface of porous graphite blocks is 0.5-2 mm.

[0054] To achieve better bonding, in this embodiment of the invention, the heat treatment temperature is 300-700℃, the heat treatment time is 5-100h, and the applied pressure is fixed at 5-10MPa.

[0055] Furthermore, in this embodiment of the invention, the composite of various raw materials at the bonding surface is further promoted by the curved temperature rise sintering, which further enhances the interfacial bonding and improves the shear strength of the material. The sintering method is as follows: the fixed body is heated from room temperature to 200℃ at a heating rate of 1-5℃ / min in an environment with a vacuum degree of 5-100 Pa, and then held for sintering for 30-200 min; the temperature is then raised from 200℃ to 500℃ and held for sintering for 30-300 min; the temperature is then raised from 500℃ to 800-1200℃ and held for sintering for 60-300 min to complete the sintering process.

[0056] Specifically, this invention provides a method for preparing porous graphite products with complex structures, comprising the following steps: preparing an adhesive, bonding treatment, and sintering treatment.

[0057] The preparation of the adhesive includes the following steps: raw material preparation, raw material mixing, spray drying, heat treatment, modification treatment, and formulation.

[0058] The method for preparing the raw materials is as follows: prepare the following raw materials according to subsequent production needs: phenolic resin (solid content 40-60wt%), furan resin (solid content 40-60wt%), epoxy resin (solid content 50-60wt%), carbon powder (particle size 200-500 mesh), boron carbide (particle size 200-800 mesh), anhydrous ethanol, polyethylene glycol (PEG1000-1500), stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS), for later use.

[0059] The method for mixing the raw materials is as follows: carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) are mixed evenly according to a predetermined weight ratio to obtain a premix. The specific mixing sequence is as follows: carbon powder and boron carbide are weighed and mixed evenly at a weight ratio of 3-7:3-7 to obtain a composite powder. Then, the composite auxiliary material is mixed with anhydrous ethanol, polyethylene glycol, stearic acid, PVP, and SDS, and then the mixture is subjected to ultrasonic dispersion and mechanical stirring. The ultrasonic frequency is controlled at 20-60 kHz, the stirring speed is 1000-3000 rpm, and the mixing process is carried out for 30-60 minutes to obtain the premix.

[0060] In this embodiment of the invention, preferably, the weight ratio of carbon powder to boron carbide is 4-6:4-6.

[0061] In this embodiment of the invention, preferably, the amount of anhydrous ethanol added is 30-50% of the weight of the composite powder; more preferably, it is 40-45%.

[0062] In this embodiment of the invention, preferably, the amount of polyethylene glycol added is 0.1-5% of the weight of the composite powder; more preferably, it is 3.3-3.9%.

[0063] In this embodiment of the invention, preferably, the amount of stearic acid added is 0.1-3% of the weight of the composite powder; more preferably, it is 1.8-2.5%.

[0064] In this embodiment of the invention, preferably, the amount of polyvinylpyrrolidone (PVP) added is 0.1-2% of the weight of the composite powder; more preferably, it is 0.9-1.3%.

[0065] In this embodiment of the invention, preferably, the amount of sodium dodecyl sulfate (SDS) added is 0.1-2% of the weight of the composite powder; more preferably, it is 0.9-1.3%.

[0066] The spray drying method involves controlling the inlet temperature of the spray dryer to be 150-180℃, the outlet temperature to be 80-100℃, the spray pressure to be 0.1-1 MPa, and the feed rate to be 70-100 L / h, thereby spray drying the premixed material to obtain the spray-dried material.

[0067] In this embodiment of the invention, preferably, the inlet temperature of the spray dryer is controlled at 160-180℃, the outlet temperature at 80-100℃, the spray pressure at 0.4-0.8 MPa, and the feed rate at 80-95 L / h, so as to spray dry the premixed material to obtain the spray-dried material.

[0068] The heat treatment method involves placing the spray-dried material in a heat treatment device, heating it to 100-400℃, holding it at that temperature for 10-20 hours, and then cooling it to obtain the heat-treated material.

[0069] In a preferred embodiment of the present invention, the spray-dried material is placed in a heat treatment device, heated to 240-300°C, heat-treated for 12-16 hours, and then cooled to obtain the heat-treated material.

[0070] The modification process involves adding γ-aminopropyltriethoxysilane to an ethanol aqueous solution with a volume concentration of 90-95%, stirring for 0.5-2 hours, then adding heat-treated materials and stirring for 1-4 hours to obtain the modified material.

[0071] In this embodiment of the invention, preferably, the weight of γ-aminopropyltriethoxysilane added is 0.5-3% of the weight of the heat-treated material; more preferably, it is 2.5-3%.

[0072] In this embodiment of the invention, preferably, the weight of the ethanol aqueous solution is 1.6-1.9 times the weight of the heat-treated material.

[0073] The preparation method is as follows: phenolic resin and furan resin are added to anhydrous ethanol and stirred evenly, controlling the weight ratio of phenolic resin and furan resin to be 1-3:1-3, and the weight of anhydrous ethanol is 2-10 times the total weight of phenolic resin and furan resin; then, the modified material is added and stirred for 1-5 hours to obtain the adhesive.

[0074] In this embodiment of the invention, preferably, the weight of anhydrous ethanol is 4-6 times the total weight of phenolic resin and furan resin; the stirring and mixing time after adding the modified materials is 2-3 hours.

[0075] In this embodiment of the invention, preferably, the weight of the modified material is 10-50% of the total weight of the phenolic resin and furan resin; more preferably, it is 35-42%.

[0076] The bonding process consists of the following steps: pretreatment and coating fixation.

[0077] The pretreatment method involves cutting porous graphite into porous graphite blocks of predetermined size according to the structural requirements of porous graphite products. The porous graphite blocks can be spliced ​​together to form porous graphite products with complex structures. Then, the porous graphite blocks are ultrasonically cleaned with deionized water, with the ultrasonic frequency controlled at 40-60 kHz, the ultrasonic cleaning temperature at 40-70°C, and the ultrasonic cleaning time at 5-20 min.

[0078] The coating and fixing method is as follows: after ultrasonic cleaning, phenolic resin and epoxy resin are mixed and uniformly coated onto the bonding surface of the porous graphite block, with the coating thickness controlled at 0.5-1 mm. After coating, the mixture is heat-treated at 300-700℃ for 5-10 hours. Then, adhesive is uniformly coated onto the bonding surface of the porous graphite block, with the coating thickness controlled at 0.5-2 mm. After coating, the porous graphite blocks are spliced ​​together according to the structural requirements of the porous graphite product (i.e., the bonding surfaces of two porous graphite blocks are joined together), and a pressure of 5-10 MPa is applied for fixing to obtain the fixed body.

[0079] In this embodiment of the invention, preferably, the solid content of the phenolic resin is 40-60 wt%, and the solid content of the epoxy resin is 50-60 wt%.

[0080] In this embodiment of the invention, preferably, the weight ratio of phenolic resin to epoxy resin is 5-7:3-5.

[0081] In this embodiment of the invention, preferably, the heat treatment temperature after the resin coating is completed is 400-550℃, and the heat treatment time is 6-8h.

[0082] In this embodiment of the invention, preferably, the applied pressure is 5-8 MPa.

[0083] The sintering process involves placing the fixture in a vacuum sintering furnace, controlling the vacuum level at 5-100 Pa, heating from room temperature to 200°C at a rate of 1-5°C / min, and holding at 200°C for 30-200 min; heating from 200°C to 500°C at a rate of 1-5°C / min, and holding at 500°C for 30-300 min; heating from 500°C to 800-1200°C at a rate of 1-5°C / min, and holding at 500°C for 60-300 min, followed by cooling to obtain a porous graphite product with a complex structure.

[0084] In a preferred embodiment of the invention, the fixation body is placed in a vacuum sintering furnace, the vacuum degree is controlled at 50-100 Pa, and the temperature is increased from room temperature to 200°C at a heating rate of 2-4°C / min, and then sintered at 200°C for 90-130 min; the temperature is increased from 200°C to 500°C at a heating rate of 2-4°C / min, and then sintered at 500°C for 180-240 min; the temperature is increased from 500°C to 950-1150°C at a heating rate of 2-4°C / min, and then sintered at 500°C for 120-200 min, and then cooled to obtain a porous graphite product with a complex structure.

[0085] The present invention will be further described below with reference to some specific embodiments.

[0086] Example 1

[0087] This embodiment provides a method for preparing porous graphite products with complex structures, the specific steps of which are as follows:

[0088] 1. Preparation of adhesive

[0089] 1) Raw material preparation

[0090] Prepare the following raw materials according to subsequent production needs: phenolic resin (50wt% solid content), furan resin (50wt% solid content), epoxy resin (60wt% solid content), carbon powder (350 mesh particle size), boron carbide (500 mesh particle size), anhydrous ethanol, polyethylene glycol (PEG-1000), stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS), for later use.

[0091] 2) Raw material mixing

[0092] Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) were mixed evenly according to a predetermined weight ratio to obtain a premix. The specific mixing sequence was as follows: carbon powder and boron carbide were weighed and mixed evenly at a weight ratio of 4:6 to obtain a composite powder. Then, the composite additives were mixed with anhydrous ethanol, polyethylene glycol, stearic acid, PVP, and SDS, and the mixture was then subjected to ultrasonic dispersion and mechanical stirring. The ultrasonic frequency was controlled at 30 kHz, the stirring speed at 2500 rpm, and the mixing process was carried out for 30 minutes to obtain the premix.

[0093] The amount of anhydrous ethanol added is 40% of the weight of the composite powder.

[0094] The amount of polyethylene glycol added is 3.3% of the weight of the composite powder.

[0095] The amount of stearic acid added is 1.8% of the weight of the composite powder.

[0096] The amount of polyvinylpyrrolidone (PVP) added is 0.9% of the weight of the composite powder.

[0097] The amount of sodium dodecyl sulfate (SDS) added is 0.9% of the weight of the composite powder.

[0098] 3) Spray drying

[0099] The inlet temperature of the spray dryer is controlled at 160℃, the outlet temperature at 80℃, the spray pressure at 0.4 MPa, and the feed rate at 80 L / h. The premixed material is spray dried to obtain the spray-dried material.

[0100] 4) Heat treatment

[0101] The spray-dried material is placed in a heat treatment device, heated to 240°C, and heat-treated for 16 hours before being cooled to obtain the heat-treated material.

[0102] 5) Modification treatment

[0103] γ-aminopropyltriethoxysilane was added to a 95% (v / v) aqueous ethanol solution and stirred for 1.2 h. Then, heat-treated materials were added and stirred for 2 h to obtain the modified material.

[0104] The weight of γ-aminopropyltriethoxysilane added is 2.5% of the weight of the heat-treated material.

[0105] The weight of the ethanol-water solution is 1.9 times the weight of the heat-treated material.

[0106] 6) Formulation

[0107] Phenolic resin and furan resin were added to anhydrous ethanol and stirred until homogeneous. The weight ratio of phenolic resin to furan resin was controlled at 1:3, and the weight of anhydrous ethanol was 4 times the total weight of phenolic resin and furan resin. Then, the modified material was added and stirred for 2 hours to obtain the adhesive.

[0108] The modified material accounts for 35% of the total weight of phenolic resin and furan resin.

[0109] 2. Adhesive treatment

[0110] 1) Preprocessing

[0111] According to the structural requirements of porous graphite products, porous graphite is cut into porous graphite blocks of predetermined size, and the porous graphite blocks can be spliced ​​together to form a porous graphite product with a complex structure; then, the porous graphite blocks are ultrasonically cleaned with deionized water, with the ultrasonic frequency controlled at 40 kHz, the ultrasonic cleaning temperature at 50°C, and the ultrasonic cleaning time at 20 min.

[0112] 2) Coating and fixing

[0113] After ultrasonic cleaning, phenolic resin and epoxy resin are mixed and uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 0.8 mm. After coating, the blocks are heat-treated at 400℃ for 6 hours. Then, adhesive is uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 1.3 mm. After coating, the porous graphite blocks are spliced ​​together according to the structural requirements of the porous graphite product (i.e., the bonding surfaces of adjacent porous graphite blocks are joined together), and a pressure of 5 MPa is applied for fixation to obtain a fixed body.

[0114] The weight ratio of phenolic resin to epoxy resin is 6:4.

[0115] 3. Sintering treatment

[0116] The fixed body was placed in a vacuum sintering furnace, and the vacuum degree was controlled at 50 Pa. The temperature was increased from room temperature to 200℃ at a heating rate of 2℃ / min, and then sintered at 200℃ for 90 min. The temperature was increased from 200℃ to 500℃ at a heating rate of 2℃ / min, and then sintered at 500℃ for 180 min. The temperature was increased from 500℃ to 950℃ at a heating rate of 2℃ / min, and then sintered at 500℃ for 120 min. After cooling, a porous graphite product with a complex structure was obtained.

[0117] Example 2

[0118] This embodiment provides a method for preparing porous graphite products with complex structures, the specific steps of which are as follows:

[0119] 1. Preparation of adhesive

[0120] 1) Raw material preparation

[0121] Prepare the following raw materials according to subsequent production needs: phenolic resin (50wt% solid content), furan resin (50wt% solid content), epoxy resin (60wt% solid content), carbon powder (350 mesh particle size), boron carbide (500 mesh particle size), anhydrous ethanol, polyethylene glycol (PEG-1000), stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS), for later use.

[0122] 2) Raw material mixing

[0123] Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) were mixed evenly according to a predetermined weight ratio to obtain a premix. The specific mixing sequence was as follows: carbon powder and boron carbide were weighed and mixed evenly at a weight ratio of 5:5 to obtain a composite powder. Then, the composite additives were mixed with anhydrous ethanol, polyethylene glycol, stearic acid, PVP, and SDS, and the mixture was then subjected to ultrasonic dispersion and mechanical stirring. The ultrasonic frequency was controlled at 34 kHz, the stirring speed at 2000 rpm, and the mixing process was carried out for 45 minutes to obtain the premix.

[0124] The amount of anhydrous ethanol added is 43% of the weight of the composite powder.

[0125] The amount of polyethylene glycol added is 3.7% of the weight of the composite powder.

[0126] The amount of stearic acid added is 2.2% of the weight of the composite powder.

[0127] The amount of polyvinylpyrrolidone (PVP) added is 1.1% of the weight of the composite powder.

[0128] The amount of sodium dodecyl sulfate (SDS) added is 1.1% of the weight of the composite powder.

[0129] 3) Spray drying

[0130] The inlet temperature of the spray dryer is controlled at 170℃, the outlet temperature at 90℃, the spray pressure at 0.6 MPa, and the feed rate at 88 L / h. The premixed material is spray dried to obtain the spray-dried material.

[0131] 4) Heat treatment

[0132] The spray-dried material is placed in a heat treatment device, heated to 280°C, and heat-treated for 14 hours before being cooled to obtain the heat-treated material.

[0133] 5) Modification treatment

[0134] γ-aminopropyltriethoxysilane was added to a 95% (v / v) aqueous ethanol solution and stirred for 1.75 h. Then, heat-treated materials were added and stirred for another 2.5 h to obtain the modified material.

[0135] The weight of γ-aminopropyltriethoxysilane added is 2.8% of the weight of the heat-treated material.

[0136] The weight of the ethanol-water solution is 1.7 times the weight of the heat-treated material.

[0137] 6) Formulation

[0138] Phenolic resin and furan resin were added to anhydrous ethanol and stirred until homogeneous. The weight ratio of phenolic resin to furan resin was controlled at 2:2, and the weight of anhydrous ethanol was 5 times the total weight of phenolic resin and furan resin. Then, the modified material was added and stirred for 2.5 hours to obtain the adhesive.

[0139] The modified material accounts for 39% of the total weight of phenolic resin and furan resin.

[0140] 2. Adhesive treatment

[0141] 1) Preprocessing

[0142] According to the structural requirements of porous graphite products, porous graphite is cut into porous graphite blocks of predetermined size, and the porous graphite blocks can be spliced ​​together to form a porous graphite product with a complex structure; then, the porous graphite blocks are ultrasonically cleaned with deionized water, with the ultrasonic frequency controlled at 50 kHz, the ultrasonic cleaning temperature at 60 ℃, and the ultrasonic cleaning time at 15 min.

[0143] 2) Coating and fixing

[0144] After ultrasonic cleaning, phenolic resin and epoxy resin are mixed and uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 0.8 mm. After coating, the blocks are heat-treated at 500℃ for 7 hours. Then, adhesive is uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 1.3 mm. After coating, the porous graphite blocks are spliced ​​together according to the structural requirements of the porous graphite product (i.e., the bonding surfaces of adjacent porous graphite blocks are joined together), and a pressure of 6.5 MPa is applied for fixation to obtain a fixed body.

[0145] The weight ratio of phenolic resin to epoxy resin is 6:4.

[0146] 3. Sintering treatment

[0147] The fixed body was placed in a vacuum sintering furnace, and the vacuum degree was controlled at 70 Pa. The temperature was increased from room temperature to 200℃ at a heating rate of 3℃ / min, and then sintered at 200℃ for 110 min. The temperature was increased from 200℃ to 500℃ at a heating rate of 3℃ / min, and then sintered at 500℃ for 200 min. The temperature was increased from 500℃ to 1050℃ at a heating rate of 3℃ / min, and then sintered at 160 min. After cooling, a porous graphite product with a complex structure was obtained.

[0148] Example 3

[0149] This embodiment provides a method for preparing porous graphite products with complex structures, the specific steps of which are as follows:

[0150] 1. Preparation of adhesive

[0151] 1) Raw material preparation

[0152] Prepare the following raw materials according to subsequent production needs: phenolic resin (50wt% solid content), furan resin (50wt% solid content), epoxy resin (60wt% solid content), carbon powder (350 mesh particle size), boron carbide (500 mesh particle size), anhydrous ethanol, polyethylene glycol (PEG-1000), stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS), for later use.

[0153] 2) Raw material mixing

[0154] Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) were mixed evenly according to a predetermined weight ratio to obtain a premix. The specific mixing sequence was as follows: carbon powder and boron carbide were weighed and mixed evenly at a weight ratio of 6:4 to obtain a composite powder. Then, the composite additives were mixed with anhydrous ethanol, polyethylene glycol, stearic acid, PVP, and SDS, and the mixture was then subjected to ultrasonic dispersion and mechanical stirring. The ultrasonic frequency was controlled at 50 kHz, the stirring speed at 2500 rpm, and the mixing process was carried out for 30 minutes to obtain the premix.

[0155] The amount of anhydrous ethanol added is 45% of the weight of the composite powder.

[0156] The amount of polyethylene glycol added is 3.9% of the weight of the composite powder.

[0157] The amount of stearic acid added is 2.5% of the weight of the composite powder.

[0158] The amount of polyvinylpyrrolidone (PVP) added is 1.3% of the weight of the composite powder.

[0159] The amount of sodium dodecyl sulfate (SDS) added is 1.3% of the weight of the composite powder.

[0160] 3) Spray drying

[0161] The inlet temperature of the spray dryer is controlled at 180℃, the outlet temperature at 100℃, the spray pressure at 0.8 MPa, and the feed rate at 95 L / h. The premixed material is spray dried to obtain the spray-dried material.

[0162] 4) Heat treatment

[0163] The spray-dried material is placed in a heat treatment device, heated to 30°C, and heat-treated for 12 hours before being cooled to obtain the heat-treated material.

[0164] 5) Modification treatment

[0165] γ-aminopropyltriethoxysilane was added to a 95% (v / v) aqueous ethanol solution and stirred for 2 hours. Then, heat-treated materials were added and stirred for 3 hours to obtain the modified material.

[0166] The weight of γ-aminopropyltriethoxysilane added is 3% of the weight of the heat-treated material.

[0167] The weight of the ethanol-water solution is 1.9 times the weight of the heat-treated material.

[0168] 6) Formulation

[0169] Phenolic resin and furan resin were added to anhydrous ethanol and stirred until homogeneous. The weight ratio of phenolic resin to furan resin was controlled at 3:1, and the weight of anhydrous ethanol was 6 times the total weight of phenolic resin and furan resin. Then, the modified material was added and stirred for 3 hours to obtain the adhesive.

[0170] The modified material accounts for 42% of the total weight of phenolic resin and furan resin.

[0171] 2. Adhesive treatment

[0172] 1) Preprocessing

[0173] According to the structural requirements of porous graphite products, porous graphite is cut into porous graphite blocks of predetermined size, and the porous graphite blocks can be spliced ​​together to form a porous graphite product with a complex structure; then, the porous graphite blocks are ultrasonically cleaned with deionized water, with the ultrasonic frequency controlled at 55 kHz, the ultrasonic cleaning temperature at 65°C, and the ultrasonic cleaning time at 10 min.

[0174] 2) Coating and fixing

[0175] After ultrasonic cleaning, phenolic resin and epoxy resin are mixed and uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 0.8 mm. After coating, the blocks are heat-treated at 550℃ for 8 hours. Then, adhesive is uniformly coated onto the bonding surface of the porous graphite blocks, with a coating thickness of 1.3 mm. After coating, the porous graphite blocks are spliced ​​together according to the structural requirements of the porous graphite product (i.e., the bonding surfaces of adjacent porous graphite blocks are joined together), and 8 MPa pressure is applied for fixation to obtain a fixed body.

[0176] The weight ratio of phenolic resin to epoxy resin is 6:4.

[0177] 3. Sintering treatment

[0178] The fixed body was placed in a vacuum sintering furnace, and the vacuum degree was controlled at 100 Pa. The temperature was increased from room temperature to 200℃ at a heating rate of 4℃ / min, and then sintered at 200℃ for 130 min. The temperature was increased from 200℃ to 500℃ at a heating rate of 4℃ / min, and then sintered at 500℃ for 240 min. The temperature was increased from 500℃ to 1150℃ at a heating rate of 4℃ / min, and then sintered at 500℃ for 200 min. After cooling, a porous graphite product with a complex structure was obtained.

[0179] Comparative Example 1

[0180] The method for preparing complex-structured porous graphite products in Comparative Example 1 adopts the technical solution of Example 2, except that: in the preparation of the adhesive, the raw material mixing, spray drying, heat treatment and modification treatment are omitted, and carbon powder and boron carbide with a weight ratio of 1:1 are directly used to replace the modifying materials in the formulation, and the adhesive is prepared by uniformly mixing with phenolic resin and furan resin.

[0181] The total weight of carbon powder and boron carbide is 15% of the total weight of phenolic resin and furan resin.

[0182] Comparative Example 2

[0183] The method for preparing complex-structured porous graphite products in Comparative Example 2 adopts the technical solution of Example 2, except that: 1) in the preparation of the adhesive, the addition of γ-aminopropyltriethoxysilane is omitted during the modification process; 2) in the bonding process, the coating of phenolic resin and epoxy resin is omitted during the coating and fixing process, and the adhesive is directly coated onto the bonding surface of the porous graphite block and then fixed.

[0184] Comparative Example 3

[0185] The method for preparing complex-structured porous graphite products in Comparative Example 3 adopts the technical solution of Example 2, except that: in the sintering process, the temperature is directly raised to 1100°C at a heating rate of 3°C / min, and then sintered at 1100°C for 300 min, and then cooled to obtain porous graphite products with complex structures.

[0186] The shear strength of the bonding joints of porous graphite products prepared using the methods of Examples 1-3 and Comparative Examples 1-3 was tested. Simultaneously, each porous graphite product was placed in an aerobic environment at 1000℃ for 1000 hours (simulating a long-term high-temperature aerobic corrosion environment), and the shear strength of the bonding joints of each porous graphite product was then tested. The specific results are shown in the table below:

[0187]

[0188] As can be seen, the method for preparing complex-structured porous graphite products of the present invention first involves mixing carbon powder, boron carbide, polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate to prepare a premix, followed by spray drying and heat treatment to obtain a heat-treated material; the heat-treated material is then modified with γ-aminopropyltriethoxysilane to obtain a modified material; the modified material is then uniformly mixed with phenolic resin, furan resin, and anhydrous ethanol to obtain an adhesive; subsequently, a mixture of phenolic resin and epoxy resin, and the adhesive are sequentially applied to the bonding surface of the porous graphite block, followed by sintering. This process yields porous graphite products with complex structures. The aforementioned processing methods (such as spray drying, heat treatment, coating, and sintering) can all be implemented using existing production equipment and processes. By dividing the complex porous graphite product into multiple bondable porous graphite blocks, these blocks can be assembled using a modular approach with specific adhesives and processes to form the final complex structure. This effectively overcomes the limitations of traditional mold forming and its processes, and allows for the flexible preparation of porous graphite products with various complex structures according to requirements.

[0189] Meanwhile, to improve the compatibility between porous graphite materials and adhesives, carbon powder and boron carbide, which are highly compatible with the porous graphite matrix, are selected in combination with phenolic resin and furan resin to reduce the internal stress at the bonding interface of porous graphite and improve compatibility. Furthermore, by modifying the heat-treated materials with γ-aminopropyltriethoxysilane, the interfacial bonding between the modified materials and phenolic resin and furan resin is improved, ensuring that they are transformed into a high-strength glassy carbon phase / reinforced particle composite during subsequent sintering, thereby significantly improving the shear strength at the bonding interface of the porous graphite blocks.

[0190] Furthermore, during the bonding process, phenolic resin and epoxy resin are used as a base coat to fully impregnate and penetrate into the micropores on the surface of porous graphite. After heat treatment and curing, a transition layer with good bonding with the porous graphite matrix is ​​formed, increasing the effective bonding surface area. Then, an adhesive is applied to ensure that the adhesive bonds efficiently with the porous graphite surface. Finally, the fixing body is sintered, and the material at the bonding surface is completely carbonized to form a glassy carbon network with carbon powder and boron carbide reinforcing components, which further improves the interfacial bonding, improves the shear strength of the material, and effectively improves the long-term stability and corrosion resistance of porous graphite products in high-temperature and oxygen-containing environments.

[0191] Unless otherwise stated, all percentages used in this invention are weight percentages.

[0192] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing porous graphite products with complex structures, characterized in that, The process includes the following steps: preparation of adhesive, bonding treatment, and sintering treatment; The method for preparing the adhesive is as follows: Carbon powder, boron carbide, anhydrous ethanol, polyethylene glycol, stearic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate are mixed evenly to obtain a premix; the premix is ​​spray-dried and heat-treated to obtain a heat-treated material; the heat-treated material is added to an ethanol-water solution containing γ-aminopropyltriethoxysilane, and after stirring and modification, a modified material is obtained; the modified material is mixed evenly with phenolic resin, furan resin, and anhydrous ethanol to obtain the adhesive. The bonding process involves mixing phenolic resin and epoxy resin and coating the mixture onto the bonding surface of the porous graphite block. After heat treatment, adhesive is applied to the bonding surface of the porous graphite block. After bonding the bonding surfaces of multiple porous graphite blocks together, pressure is applied to fix them and a fixed body is obtained. The sintering process is as follows: the stationary body is heated from room temperature to 200℃ at a heating rate of 1-5℃ / min in an environment with a vacuum degree of 5-100 Pa, and then sintered at that temperature for 30-200 min; the temperature is then further increased from 200℃ to 500℃ and sintered at that temperature for 30-300 min; the temperature is then further increased from 500℃ to 800-1200℃ and sintered at that temperature for 60-300 min, thus completing the sintering process and obtaining a porous graphite product with a complex structure.

2. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the preparation of the premix, the weight ratio of carbon powder to boron carbide is 3-7:3-7; The weight of anhydrous ethanol is 30-50% of the total weight of carbon powder and boron carbide; The weight of polyethylene glycol is 0.1-5% of the total weight of carbon powder and boron carbide; The weight of stearic acid is 0.1-3% of the total weight of carbon powder and boron carbide; The weight of polyvinylpyrrolidone is 0.1-2% of the total weight of carbon powder and boron carbide; The weight of sodium dodecyl sulfate is 0.1-2% of the total weight of carbon powder and boron carbide.

3. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the preparation of the adhesive, the inlet temperature of the spray drying is controlled at 150-180℃, the outlet temperature at 80-100℃, the spray pressure at 0.1-1 MPa, and the feed rate at 70-100 L / h.

4. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the preparation of the adhesive, the heat treatment temperature is 100-400℃ and the heat treatment time is 10-20h.

5. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the preparation of the adhesive, the weight of γ-aminopropyltriethoxysilane is 0.5-3% of the weight of the heat-treated material; The weight of the ethanol-water solution is 1.6-1.9 times the weight of the heat-treated material; The volume concentration of the aqueous ethanol solution is 90-95%.

6. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the preparation of the adhesive, the solid content of phenolic resin is 40-60 wt%, and the solid content of furan resin is 40-60 wt%. The weight ratio of phenolic resin to furan resin is 1-3:1-3; The weight of the modified material is 10-50% of the total weight of phenolic resin and furan resin; The weight of anhydrous ethanol is 2-10 times the total weight of phenolic resin and furan resin.

7. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the bonding process, before coating the porous graphite block with a mixture of phenolic resin and epoxy resin, the porous graphite block is first ultrasonically cleaned with deionized water. The ultrasonic cleaning frequency is 40-60KHz, and the ultrasonic cleaning temperature is 40-70℃.

8. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the bonding process, the solid content of phenolic resin is 40-60 wt%, and the solid content of epoxy resin is 50-60 wt%. The weight ratio of phenolic resin to epoxy resin is 5-7:3-5; The resin coating thickness on the bonding surface of the porous graphite block is 0.5-1mm; The adhesive coating thickness on the bonding surface of the porous graphite block is 0.5-2 mm.

9. The method for preparing complex-structured porous graphite products according to claim 1, characterized in that, In the bonding process, the heat treatment temperature is 300-700℃ and the heat treatment time is 5-100h; The applied pressure is fixed at 5-10 MPa.

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