Silicified graphite containing a three-dimensional network of silicon carbide skeletons and a method of making

Abstract

The application provides siliconized graphite containing a three-dimensional network silicon carbide skeleton and a preparation method, and comprises the following steps: preparing a graphite matrix containing a three-dimensional network macroscopic through hole, performing high-temperature graphitization treatment to open micro pores of the graphite, adding silicon powder to perform liquid silicon infiltration treatment, and infiltrating silicon liquid into the macroscopic through hole and the micro pores to form a structure in which a macroscopic network silicon carbide skeleton is connected with fine silicon carbide branches, so as to obtain the siliconized graphite. In the application, the macroscopic through hole provides a channel for the liquid silicon to infiltrate into the micro pores of the graphite, increases the infiltration depth of the liquid silicon in the graphite matrix, regulates the mechanical properties of the siliconized graphite through the three-dimensional network silicon carbide skeleton, and improves the service performance of the siliconized graphite.

Description

Technical Field

[0001] The present invention relates to the technical field of silicified graphite preparation, and in particular to silicified graphite containing a three-dimensional network silicon carbide skeleton and a preparation method thereof. Background Art

[0002] Graphite, with its excellent self-lubricating properties, high thermal conductivity, and low thermal expansion, is widely used in sliding bearings and mechanical seals in the chemical, nuclear, and marine industries. However, its load-bearing capacity and wear resistance are insufficient to meet the requirements of friction pairs under heavy loads. Therefore, graphite modification is necessary to improve its mechanical properties. Graphite typically contains tiny pores, and impregnation of microporous graphite can be used to produce graphite products with various composite materials, such as resin-impregnated graphite, silver-impregnated graphite, and silicified graphite.

[0003] Silicified graphite is a composite material composed of graphite, silicon carbide, and silicon, resulting from a siliconization process on a graphite matrix. Silicon carbide, as a load-bearing phase, significantly increases the material's strength and hardness, while graphite, as a self-lubricating phase, reduces the interfacial friction coefficient. Silicified graphite boasts high strength, high thermal conductivity, wear resistance, and excellent lubricity, making it suitable for the manufacture of heavy-loaded sliding bearings.

[0004] Liquid-phase siliconization is a low-cost method for preparing silicified graphite. The process involves melting silicon powder in a vacuum and high-temperature environment. Liquid silicon penetrates the graphite pores and reacts with the graphite at temperatures between 1550°C and 1700°C, producing silicon carbide. However, because graphite pores are both open and closed, and lack extensive connectivity between them, the liquid silicon can penetrate only a few millimeters, making it difficult to produce thick silicified graphite.

[0005] To increase the reaction depth of silicified graphite, researchers have manipulated the pore structure and porosity of graphite, attempting to connect the pores by increasing the temperature, but significant results have yet to be achieved. Furthermore, the mechanical properties of silicified graphite are closely related to the ratio and distribution of the graphite matrix, silicon carbide phase, and silicon phase. The distribution of "graphite-silicon carbide-silicon" is controlled by the size and structure of the graphite micropores. Therefore, it is necessary to design a new type of porous graphite, develop a process for preparing thick silicified graphite, and manipulate the mechanical properties of silicified graphite.

[0006] Therefore, it is necessary to propose a new technical solution. Summary of the Invention

[0007] In view of the defects in the prior art, the purpose of the present invention is to provide a silicified graphite containing a three-dimensional network silicon carbide skeleton and a preparation method.

[0008] According to the present invention, a method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton is provided, the method comprising the following steps:

[0009] Step S1: preparing a graphite body having three-dimensional macroscopic through-pores as a silicified graphite matrix;

[0010] Step S2: calcining the graphite matrix to form micropores in the graphite matrix, which are connected to the three-dimensional macro-network through holes;

[0011] Step S3: injecting silicon powder into the three-dimensional macro-network through-pores of the graphite matrix;

[0012] Step S4: placing the graphite substrate and silicon powder into a graphite mold, adding silicon powder and covering the upper surface of the graphite substrate;

[0013] Step S5: placing the graphite mold containing the graphite matrix and silicon powder into a furnace chamber of a vacuum sintering furnace;

[0014] Step S6: starting the vacuum sintering furnace, evacuating the furnace chamber, and heating it to increase the temperature;

[0015] Step S7: The silicon powder on the upper surface of the graphite substrate and in the three-dimensional macro-network through-holes melts, fills the internal through-holes of the graphite and penetrates into the tiny pores of the graphite substrate. The silicon powder reacts with the graphite substrate to form silicon carbide.

[0016] Step S8: The silicon remaining in the three-dimensional macroscopic through-pores and micropores of the graphite matrix is ​​tightly combined with the graphite matrix and silicon carbide to form silicified graphite;

[0017] Step S9: After the silicification reaction is completed, the temperature is lowered to obtain the prepared silicified graphite.

[0018] Preferably, after the silicidation reaction, a coarse network of silicon carbide skeletons is formed at the network-like macroscopic through-pores of the graphite matrix, and fine silicon carbide branch structures are formed at the microscopic pores of the graphite matrix; the coarse silicon carbide skeletons are connected to the fine silicon carbide branch structures.

[0019] Preferably, the three-dimensional network silicon carbide skeleton changes the mechanical properties of the silicified graphite, and the three-dimensional macro-network through holes in the graphite matrix are designed according to the mechanical property requirements of the silicified graphite.

[0020] Preferably, the three-dimensional network of macroscopic through holes in the graphite matrix provides a channel for liquid silicon to penetrate into the microscopic pores of graphite, thereby increasing the penetration depth of liquid silicon in the graphite matrix; when the spacing between the upper and lower macroscopic through holes is less than the penetration depth of liquid silicon in the microscopic pores of the graphite matrix, the liquid silicon penetrates downward through the network of macroscopic through holes to prepare a silicified graphite body with a large thickness.

[0021] Preferably, a macroscopic array of through holes is drilled on the graphite substrate using a drill bit, and the macroscopic through holes are of a three-dimensional vertical cross type or a vertical array type.

[0022] Preferably, the method for preparing macroscopic through-holes in a graphite matrix comprises:

[0023] A three-dimensional mesh metal skeleton is prepared using an additive manufacturing process, and the graphite particles and the binder-filled metal skeleton are pressed into shape;

[0024] Graphite is used as an anode for electrolytic treatment, and graphite containing three-dimensional network macroscopic through-pores is obtained after removing the metal skeleton.

[0025] Preferably, the macroscopic through holes in the graphite substrate are of a three-dimensional vertical cross type, a vertical array through hole type, a three-dimensional ring type or a three-dimensional spiral type.

[0026] Preferably, the macroscopic through-pore diameter of the graphite substrate is 0.1-2 mm.

[0027] Preferably, the silicidation reaction temperature of the graphite substrate and liquid silicon is controlled at 1550°C-1700°C.

[0028] The present invention also provides a silicified graphite, wherein the graphite is prepared using the above-mentioned method for preparing the silicified graphite containing a three-dimensional network silicon carbide skeleton.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention uses a graphite matrix containing a three-dimensional network of macroscopic through-holes. The macroscopic through-holes provide channels for liquid silicon to penetrate into the graphite micropores, thereby increasing the penetration depth of liquid silicon in the graphite matrix. When the spacing between the upper and lower macroscopic through-holes is lower than the penetration depth of liquid silicon in the micropores of the graphite matrix, the liquid silicon can penetrate downward through the network of macroscopic through-holes, thereby preparing a thick silicified graphite body.

[0031] 2. The present invention prepares silicified graphite with a three-dimensional network silicon carbide skeleton. The three-dimensional network silicon carbide skeleton changes the mechanical properties of the silicified graphite. According to the correlation between the silicon carbide skeleton and the mechanical properties of the silicified graphite, the three-dimensional macro-network through holes in the graphite matrix are designed, thereby effectively regulating the mechanical properties of the silicified graphite to meet the service requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0033] Figure 1 Schematic diagram of a graphite matrix containing three-dimensional macroscopic through-holes;

[0034] Figure 2Schematic diagram of a three-dimensional network silicon carbide skeleton;

[0035] Figure 3 This is a scanning electron microscope image of silicified graphite;

[0036] Figure 4 It is a schematic diagram of the process of the present invention.

[0037] in:

[0038] Reticular silicon carbide skeleton 1 Graphite matrix 3

[0039] Silicon carbide branching structure 2 Silicon 4

[0040] Silicon carbide 5 DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0042] Example 1:

[0043] Reference Figure 4 According to the present invention, a method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton is provided, the method comprising the following steps:

[0044] Step S1: preparing a graphite body having three-dimensional macroscopic through-pores as a silicified graphite matrix;

[0045] Step S2: calcining the graphite matrix to form micropores in the graphite matrix, which are connected to the three-dimensional macro-network through holes;

[0046] Step S3: injecting silicon powder into the three-dimensional macro-network through-pores of the graphite matrix;

[0047] Step S4: placing the graphite substrate and silicon powder into a graphite mold, adding silicon powder and covering the upper surface of the graphite substrate;

[0048] Step S5: placing the graphite mold containing the graphite matrix and silicon powder into a furnace chamber of a vacuum sintering furnace;

[0049] Step S6: starting the vacuum sintering furnace, evacuating the furnace chamber, and heating it to increase the temperature;

[0050] Step S7: The silicon powder on the upper surface of the graphite substrate and in the three-dimensional macro-network through-holes melts, fills the internal through-holes of the graphite and penetrates into the tiny pores of the graphite substrate. The silicon powder reacts with the graphite substrate to form silicon carbide.

[0051] Step S8: The silicon remaining in the three-dimensional macroscopic through-pores and micropores of the graphite matrix is ​​tightly combined with the graphite matrix and silicon carbide to form silicified graphite;

[0052] Step S9: After the silicification reaction is completed, the temperature is lowered to obtain the prepared silicified graphite.

[0053] After the silicidation reaction, a coarse network of silicon carbide skeletons is formed at the network of macroscopic through-holes in the graphite matrix, and a fine silicon carbide branch structure is formed at the microscopic pores in the graphite matrix; the coarse silicon carbide skeleton is connected to the fine silicon carbide branch structure; the three-dimensional network of silicon carbide skeletons changes the mechanical properties of the silicified graphite, and the three-dimensional macroscopic network of through-holes in the graphite matrix is ​​designed according to the mechanical property requirements of the silicified graphite; the three-dimensional network of macroscopic through-holes in the graphite matrix provides a channel for liquid silicon to penetrate into the microscopic pores of the graphite, thereby increasing the penetration depth of liquid silicon in the graphite matrix; when the distance between the upper and lower macroscopic through-holes is less than the penetration depth of liquid silicon in the microscopic pores of the graphite matrix, the liquid silicon penetrates downward through the network of macroscopic through-holes to prepare a silicified graphite body with a large thickness.

[0054] The method for preparing macroscopic through-holes in a graphite matrix comprises:

[0055] A three-dimensional mesh metal skeleton is prepared using an additive manufacturing process, and the graphite particles and the binder-filled metal skeleton are pressed into shape;

[0056] Graphite is used as an anode for electrolytic treatment, and graphite containing three-dimensional network macroscopic through-pores is obtained after removing the metal skeleton.

[0057] The macroscopic through holes in the graphite matrix are three-dimensional vertical cross type, vertical array through hole type, three-dimensional ring type or three-dimensional spiral type; the diameter of the macroscopic through holes in the graphite matrix is ​​0.1-2mm; the silicification reaction temperature of the graphite matrix and liquid silicon is controlled at 1550℃-1700℃.

[0058] The present invention also provides a silicified graphite, wherein the graphite is prepared using the above-mentioned method for preparing the silicified graphite containing a three-dimensional network silicon carbide skeleton.

[0059] Example 2:

[0060] The present invention provides a method for preparing silicified graphite containing a three-dimensional network of macroscopic through-pores, comprising: preparing a graphite substrate 3 containing a three-dimensional network of macroscopic through-pores; performing a high-temperature graphitization treatment to open the graphite's micropores; and adding silicon powder for liquid-phase siliconization. The silicon liquid penetrates the macroscopic through-pores and micropores, forming a structure in which a macroscopic network of silicon carbide skeleton is connected to fine silicon carbide branches, thereby obtaining the silicified graphite. The macroscopic through-pores provide channels for liquid silicon to penetrate the graphite's micropores, thereby increasing the penetration depth of the liquid silicon into the graphite substrate 3. The three-dimensional network of silicon carbide skeletons modulates the mechanical properties of the silicified graphite, thereby improving the working performance of the silicified graphite.

[0061] According to the present invention, a method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton is provided, comprising:

[0062] preparing a graphite body with three-dimensional macroscopic through-pores as a matrix of silicified graphite;

[0063] The graphite substrate 3 is calcined to form micropores in the graphite substrate 3, which are connected to the macro network through-pores.

[0064] Injecting silicon powder into the macroscopic through-holes of the graphite substrate 3;

[0065] Put the graphite substrate 3 and silicon powder into a graphite mold, add silicon powder and cover the upper surface of the graphite substrate 3;

[0066] The graphite mold containing the graphite substrate 3 and silicon powder is placed in the furnace chamber of a vacuum sintering furnace;

[0067] Start the vacuum sintering furnace, evacuate the furnace chamber, and slowly heat it up;

[0068] The silicon powder on the upper surface of the graphite matrix 3 and in the macroscopic through-holes melts at high temperature, fills the internal through-holes of the graphite and penetrates into the micro-pores of the graphite matrix 3. At high temperature, the silicon powder reacts with the graphite matrix 3 to form silicon carbide 5.

[0069] The silicon 4 remaining in the macroscopic through-pores and microscopic pores of the graphite matrix 3 is tightly bonded to the graphite matrix 3 and the silicon carbide 5 to form silicified graphite. After the silicification reaction is completed, the temperature is slowly lowered.

[0070] After the silicidation reaction, a coarse network of silicon carbide skeletons 1 is formed at the network macroscopic through holes of the graphite matrix 3, and fine silicon carbide branch structures 2 are formed at the microscopic pores of the graphite matrix 3; the coarse network of silicon carbide skeletons 1 are connected to the fine silicon carbide branch structures 2.

[0071] Preferably, the temperature of the silicification reaction between the liquid silicon and the graphite is controlled at 1550°C-1700°C.

[0072] Preferably, a macroscopic array of through holes is drilled on the graphite substrate 3 using a drill bit, and the macroscopic through holes are three-dimensional vertical cross-type or vertical array through hole type.

[0073] Preferably, the method for preparing the macroscopic through holes in the graphite matrix 3 includes: using an additive manufacturing process to prepare a three-dimensional mesh metal skeleton, pressing the graphite particles and the binder-filled metal skeleton into shape; using the graphite as an anode for electrolysis, and removing the metal skeleton to obtain graphite containing three-dimensional mesh macroscopic through holes; the macroscopic through holes in the graphite matrix 3 are three-dimensional vertical cross type, vertical array through hole type, three-dimensional ring type or three-dimensional spiral type.

[0074] Preferably, the macroscopic through-hole diameter of the graphite substrate 3 is 0.1-2 mm.

[0075] According to the present invention, a method for preparing silicified graphite having a silicon carbide network skeleton is provided, comprising:

[0076] A three-dimensional vertically crossed metal wire skeleton was prepared using an additive manufacturing process. The metal wire was made of 316L stainless steel with a diameter of 0.3mm and a wire spacing of 3mm. The metal skeleton was filled with graphite particles and a binder and pressed into shape. The graphite was used as an anode for electrolysis. After removing the metal skeleton, a three-dimensional network of macroscopic through-hole graphite raw products was obtained, such as Figure 1 shown.

[0077] The graphite raw product is subjected to calcination and graphitization treatment, the calcination temperature is not higher than 1200°C, and the graphitization temperature is 2400°C. After calcination, the binder asphalt is gradually coked to form tiny pores, which are connected to the macro-network through-pores.

[0078] Inject silicon powder into the macroscopic through-holes of the graphite substrate 3, place the graphite substrate 3 and the silicon powder into a graphite mold, add silicon powder and cover the upper surface of the graphite substrate 3;

[0079] The graphite mold containing the graphite substrate 3 and silicon powder is placed in a furnace chamber of a vacuum sintering furnace; the vacuum sintering furnace is started, the furnace chamber is evacuated, and the temperature is slowly increased.

[0080] The silicon powder on the upper surface of the graphite substrate 3 and in the macroscopic through-pores melts at high temperature, fills the internal through-pores of the graphite and penetrates into the microscopic pores of the graphite substrate 3. The temperature of the vacuum sintering chamber is controlled at 1600°C. The liquid silicon reacts with the graphite substrate 3 to form silicon carbide 5. The silicon 4 remaining in the macroscopic through-pores and microscopic pores of the graphite substrate 3 is tightly combined with the graphite substrate 3 and the silicon carbide 5 to form siliconized graphite. Figure 3 shown.

[0081] After the silicidation reaction, a coarse network of silicon carbide skeleton 1 is formed in the network macro-channel of the graphite matrix 3, and a fine silicon carbide branch structure 2 is formed in the micro-pores of the graphite matrix 3; the coarse network of silicon carbide skeleton 1 is connected with the fine silicon carbide branch structure 2, such as Figure 2 shown.

[0082] After the silicification reaction is completed, the temperature is slowly lowered.

[0083] According to the present invention, a method for preparing silicified graphite having a silicon carbide network skeleton is provided, comprising:

[0084] A porous graphite body that has been calcined and graphitized is selected, and a drill with a diameter of 0.3 mm is used to drill three-dimensional vertical cross holes on the graphite body. The hole spacing is 3 mm. Figure 1 shown.

[0085] Inject silicon powder into the macroscopic through-holes of the graphite substrate 3, place the graphite substrate 3 and the silicon powder into a graphite mold, add silicon powder and cover the upper surface of the graphite substrate 3;

[0086] The graphite mold containing the graphite substrate 3 and silicon powder is placed in a furnace chamber of a vacuum sintering furnace; the vacuum sintering furnace is started, the furnace chamber is evacuated, and the temperature is slowly increased.

[0087] The silicon powder on the upper surface of the graphite substrate 3 and in the macroscopic through-pores melts at high temperature, fills the internal through-pores of the graphite and penetrates into the microscopic pores of the graphite substrate 3. The temperature of the vacuum sintering chamber is controlled at 1600°C. The liquid silicon reacts with the graphite substrate 3 to form silicon carbide 5. The silicon 4 remaining in the macroscopic through-pores and microscopic pores of the graphite substrate 3 is tightly combined with the graphite substrate 3 and the silicon carbide 5 to form siliconized graphite. Figure 3 shown.

[0088] After the silicidation reaction, a coarse network of silicon carbide skeleton 1 is formed in the network macro-channel of the graphite matrix 3, and a fine silicon carbide branch structure 2 is formed in the micro-pores of the graphite matrix 3; the coarse network of silicon carbide skeleton 1 is connected with the fine silicon carbide branch structure 2, such as Figure 2 shown.

[0089] After the silicification reaction is completed, the temperature is slowly lowered.

[0090] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0091] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0092] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton, characterized in that: The method comprises the following steps: Step S1: preparing a graphite matrix having three-dimensional macroscopic through-pores as a silicified graphite matrix; Step S2: calcining the graphite matrix to form micropores in the graphite matrix, which are connected to the three-dimensional macro-network through holes; Step S3: injecting silicon powder into the three-dimensional macro-network through-pores of the graphite matrix; Step S4: placing the graphite substrate and silicon powder into a graphite mold, adding silicon powder and covering the upper surface of the graphite substrate; Step S5: placing the graphite mold containing the graphite matrix and silicon powder into a furnace chamber of a vacuum sintering furnace; Step S6: starting the vacuum sintering furnace, evacuating the furnace chamber, and heating it to increase the temperature; Step S7: The silicon powder on the upper surface of the graphite substrate and in the three-dimensional macro-network through-holes melts, fills the internal through-holes of the graphite and penetrates into the tiny pores of the graphite substrate. The silicon powder reacts with the graphite substrate to form silicon carbide. Step S8: The silicon remaining in the three-dimensional macroscopic through-pores and micropores of the graphite matrix is ​​tightly combined with the graphite matrix and silicon carbide to form silicified graphite; Step S9: After the silicification reaction is completed, the temperature is lowered to obtain the prepared silicified graphite; The diameter of the macroscopic through holes of the graphite matrix is ​​0.1-2 mm, and the distance between the upper and lower macroscopic through holes is smaller than the penetration depth of the liquid silicon in the microscopic pores of the graphite matrix.

2. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 1, characterized in that: After the silicidation reaction, a coarse network of silicon carbide skeletons is formed at the network-like macroscopic through-pores of the graphite matrix, and fine silicon carbide branch structures are formed at the microscopic pores of the graphite matrix; the coarse silicon carbide skeletons are connected to the fine silicon carbide branch structures.

3. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 1, characterized in that: The three-dimensional network silicon carbide skeleton changes the mechanical properties of the silicified graphite. According to the mechanical property requirements of the silicified graphite, the three-dimensional macro-network through holes in the graphite matrix are designed.

4. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 1, characterized in that: A macroscopic array of through holes is drilled on a graphite substrate using a drill bit. The macroscopic through holes are in a three-dimensional vertical cross type or a vertical array type.

5. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 1, characterized in that: The method for preparing macroscopic through-holes in a graphite matrix comprises: A three-dimensional mesh metal skeleton is prepared using an additive manufacturing process, and the graphite particles and the binder-filled metal skeleton are pressed into shape; Graphite is used as an anode for electrolytic treatment, and graphite containing three-dimensional network macroscopic through-pores is obtained after removing the metal skeleton.

6. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 5, characterized in that: The macroscopic through holes in the graphite matrix are of three-dimensional vertical cross type, vertical array through hole type, three-dimensional ring type or three-dimensional spiral type.

7. The method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton according to claim 1, characterized in that: The silicidation reaction temperature of the graphite substrate and liquid silicon is controlled at 1550°C-1700°C.

8. A silicified graphite, characterized in that The graphite is prepared by the method for preparing silicified graphite containing a three-dimensional network silicon carbide skeleton as described in any one of claims 1 to 7.

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