Impregnation method of isostatic graphite

Abstract

The application discloses an impregnation method of isostatic pressing graphite, which is impregnated after two times of channel dredging, so that the impregnated product is obtained. In the first time of channel dredging, the dust and gas existing in the channel are flushed out by using pressurized deionized water, and the pressurized deionized water can flush out some thin obstacles in the channel to further dredge the channel. In the process of drying the deionized water, liquid water is changed into water vapor and blown out of the hole, so that the residual gas and dust in the channel are further cleaned. In the process of negative pressure extraction, nitrogen filling and negative pressure extraction in the second time of channel dredging, the channel is further dredged, and the residual water in the first time of channel dredging is removed. The deionized water is used as a cleaning agent, so that the cost is effectively reduced, the production product improves the channel dredging capacity, and is more suitable for application in actual production.

Description

Technical Field

[0001] This invention relates to the field of graphite technology, and in particular to an impregnation method for isostatically pressed graphite. Background Technology

[0002] With the rapid development of my country's semiconductor and photovoltaic industries, the demand for isostatically pressed graphite materials is growing rapidly. As an emerging graphite material, isostatically pressed graphite boasts high strength, high density, and high purity. Furthermore, because its production involves applying the same pressure in all directions, it exhibits excellent density uniformity and isotropy. Its outstanding high-temperature resistance, chemical corrosion resistance, and strong thermal and electrical conductivity also make it highly promising and widely applicable in high-tech fields, earning it the reputation as one of the most promising materials of the century. However, compared to foreign countries, my country's isostatic pressing production involves multiple firing and impregnation processes, and the final product's density is lower. This is mainly because the impregnation process fails to completely clear the pores in the material, preventing the impregnating solution from filling every single cavity.

[0003] Patent CN115259898A, entitled "An Impregnation Method for Isostatic Graphite Products and the Products Thereof," discloses a method where an isostatically pressed graphite calcined product is cleaned, placed in an impregnation tank, heated to a certain temperature, and then evacuated. After maintaining this temperature for a certain period, liquid medium-temperature coal tar pitch is introduced into the impregnation tank to immerse the product and heat it. Once the temperature is reached, nitrogen pressure is applied and maintained for a certain period. The pressure is then released while maintaining the temperature, and simultaneously, the medium-temperature coal tar pitch is returned. The impregnation tank is then evacuated to remove the medium-temperature coal tar pitch impregnated inside the product. After maintaining this vacuum for a period, liquid high-temperature coal tar pitch is introduced to immerse the product. The product is then heated to a certain temperature, pressurized, and maintained for a period. After cooling to a certain temperature, the pressure is released, and the product is returned to the asphalt and further cooled to room temperature. However, the cost of liquid medium-temperature coal tar pitch is high, making it difficult to control production costs at a reasonable level. Experiments have shown that this method is difficult to apply in actual production. Therefore, there is an urgent need for an improved method for the isostatically pressed graphite impregnation process to solve this problem. Summary of the Invention

[0004] In view of this, the present invention addresses the deficiencies of the prior art, and its main objective is to provide an impregnation method for isostatic graphite that has low impregnation cost, better pore unblocking effect, and improved impregnation effect.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An impregnation method for isostatically pressed graphite includes the following steps:

[0007] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 270-300℃ and the heating rate is 40-60℃ / h.

[0008] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 50-250Pa, maintain the pressure for 3-5h, then inject deionized water at 60-80℃, introduce inert gas to pressurize to 2-2.4MPa, soak for 2-3h, then drain the deionized water, dry at 240-300℃ for 6-8h;

[0009] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 300-900Pa, hold the pressure for 2-5 hours, then fill it with inert gas to pressurize it to 0.4-1.4MPa, hold the pressure for 3-6 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 50-200Pa, hold the pressure for 3-6 hours.

[0010] (4) Impregnation: Heat the liquid asphalt to 220-260℃ and pour it into the tank. Soak for 2-6 hours. Then, pressurize the tank with inert gas to 1.4-2.4 MPa and maintain the pressure for 2-4 hours. Then, pressurize the tank with inert gas again to 2.8-3.9 MPa and maintain the pressure for 3-9 hours.

[0011] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill in the inert gas and pressurize it to 3.9-5.0 MPa. After the temperature cools down to 65-75℃, release the pressure to obtain the impregnated product.

[0012] As a preferred embodiment, the inert gas is nitrogen.

[0013] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0014] During the first channel unblocking process, pressurized deionized water is used to flush out dust and gas from the channels. Simultaneously, the pressurized deionized water can break through thinner obstructions within the channels, further unblocking them. Furthermore, during the drying process of the deionized water, the liquid water turns into water vapor and is blown out of the holes, further cleaning any remaining gas and dust. Combined with the second channel unblocking process—a process of drawing negative pressure, filling with nitrogen, and then drawing negative pressure again—not only further unblocks the channels but also removes any residual moisture from the first unblocking. Using deionized water as a cleaning agent not only effectively reduces costs but also improves the unblocking ability of the finished product, making it more suitable for practical production applications.

[0015] To more clearly illustrate the effects of the present invention, the present invention will be described in detail below with reference to specific embodiments: Detailed Implementation

[0016] This invention discloses an impregnation method for isostatically pressed graphite, comprising the following steps:

[0017] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 270-300℃ and the heating rate is 40-60℃ / h.

[0018] (2) First pore clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 50-250Pa, maintain the pressure for 3-5h, then inject deionized water at 60-80℃, introduce inert gas to pressurize to 2-2.4MPa, soak for 2-3h, then drain the deionized water, dry at 240-300℃ for 6-8h.

[0019] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 300-900Pa, maintain the pressure for 2-5 hours, then fill with nitrogen to pressurize to 0.4-1.4MPa, maintain the pressure for 3-6 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 50-200Pa, maintain the pressure for 3-6 hours.

[0020] (4) Impregnation: Heat the liquid asphalt to 220-260℃ and pour it into the tank. Soak for 2-6 hours. Then pressurize the tank with nitrogen to 1.4-2.4MPa and maintain the pressure for 2-4 hours. Then pressurize the tank with nitrogen again to 2.8-3.9MPa and maintain the pressure for 3-9 hours.

[0021] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 3.9-5.0 MPa. After the temperature cools down to 65-75℃, release the pressure to obtain the impregnated product.

[0022] The following detailed description is based on specific embodiments.

[0023] Example 1

[0024] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 270℃ and the heating rate is 40℃ / h.

[0025] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 150Pa, maintain the pressure for 3h, then inject deionized water at 70℃, introduce inert gas to pressurize to 2.2MPa, soak for 3h, then drain the deionized water, dry at 280℃ for 7h.

[0026] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 600Pa, maintain the pressure for 5 hours, then fill it with nitrogen to pressurize it to 1MPa, maintain the pressure for 4.5 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 120Pa, maintain the pressure for 5 hours.

[0027] (4) Impregnation: Heat the liquid asphalt to 260°C and pour it into the tank. Soak for 2 hours, then pressurize the tank with nitrogen to 1.8 MPa and maintain the pressure for 3 hours. Then pressurize the tank with nitrogen to 3.9 MPa and maintain the pressure for 9 hours.

[0028] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 4.5 MPa. After the temperature cools down to 65°C, release the pressure to obtain the impregnated product.

[0029] Example 2

[0030] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 280℃ and the heating rate is 60℃ / h.

[0031] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 50Pa, maintain the pressure for 5h, then inject deionized water at 80℃, introduce inert gas to pressurize to 2.4MPa, soak for 3h, then drain the deionized water, dry at 260℃ for 6h.

[0032] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 800Pa, maintain the pressure for 2 hours, then fill it with nitrogen to pressurize it to 0.8MPa, maintain the pressure for 5 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 180Pa, maintain the pressure for 3 hours.

[0033] (4) Impregnation: Heat the liquid asphalt to 220°C and pour it into the tank. Soak for 6 hours, then pressurize the tank with nitrogen to 2.0 MPa and maintain the pressure for 2 hours. Then pressurize the tank with nitrogen to 3.0 MPa and maintain the pressure for 6 hours.

[0034] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 5MPa. After the temperature cools down to 70℃, release the pressure to obtain the impregnated product.

[0035] Example 3

[0036] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 300℃ and the heating rate is 55℃ / h.

[0037] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 250Pa, maintain the pressure for 3.5h, then inject deionized water at 75℃, introduce inert gas to pressurize to 2.2MPa, soak for 2h, then drain the deionized water, dry at 240℃ for 8h.

[0038] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 300Pa, maintain the pressure for 5 hours, then fill it with nitrogen to pressurize it to 0.4MPa, maintain the pressure for 5 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 150Pa, maintain the pressure for 6 hours.

[0039] (4) Impregnation: Heat the liquid asphalt to 240°C and pour it into the tank. Soak for 4 hours, then pressurize the tank with nitrogen to 2.2 MPa and maintain the pressure for 3 hours. Then pressurize the tank with nitrogen to 3.2 MPa and maintain the pressure for 6 hours.

[0040] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 3.9 MPa. After the temperature cools down to 75°C, release the pressure to obtain the impregnated product.

[0041] Example 4

[0042] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 280℃ and the heating rate is 45℃ / h.

[0043] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 180Pa, maintain the pressure for 3h, then inject deionized water at 60℃, introduce inert gas to pressurize to 2.2MPa, soak for 3h, then drain the deionized water, dry at 300℃ for 7h.

[0044] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 800Pa, maintain the pressure for 5 hours, then fill it with nitrogen to pressurize it to 1.4MPa, maintain the pressure for 3 hours, and vacuum the impregnation tank a second time to make the pressure inside the tank 150Pa, maintain the pressure for 5 hours.

[0045] (4) Impregnation: Heat the liquid asphalt to 260°C and pour it into the tank. Soak for 2 hours, then pressurize the tank with nitrogen to 1.6 MPa and maintain the pressure for 3 hours. Then pressurize the tank with nitrogen to 3.5 MPa and maintain the pressure for 9 hours.

[0046] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 4.8 MPa. After the temperature cools down to 65°C, release the pressure to obtain the impregnated product.

[0047] Example 5

[0048] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 290℃ and the heating rate is 60℃ / h.

[0049] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 50Pa, maintain the pressure for 5h, then inject deionized water at 60℃, introduce inert gas to pressurize to 2MPa, soak for 3h, then drain the deionized water, dry at 260℃ for 8h.

[0050] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 900Pa, maintain the pressure for 4 hours, then fill it with nitrogen to pressurize to 1MPa, maintain the pressure for 6 hours, vacuum the impregnation tank a second time to make the pressure inside the tank 200Pa, maintain the pressure for 5 hours.

[0051] (4) Impregnation: Heat the liquid asphalt to 220°C and pour it into the tank. Soak for 6 hours. Then pressurize the tank with nitrogen to 2.4 MPa and maintain the pressure for 2 hours. Then pressurize the tank with nitrogen to 3.2 MPa and maintain the pressure for 6 hours.

[0052] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 4.5 MPa. After the temperature cools down to 70°C, release the pressure to obtain the impregnated product.

[0053] Example 6

[0054] (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 280℃ and the heating rate is 55℃ / h.

[0055] (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 250Pa, maintain the pressure for 3.5h, then inject deionized water at 75℃, introduce inert gas to pressurize to 2.2MPa, soak for 2h, then drain the deionized water, dry at 250℃ for 8h.

[0056] (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 500Pa, maintain the pressure for 5h, then fill it with nitrogen to pressurize to 0.8MPa, maintain the pressure for 5h, and vacuum the impregnation tank a second time to make the pressure inside the tank 180Pa, maintain the pressure for 6h.

[0057] (4) Impregnation: Heat the liquid asphalt to 240°C and pour it into the tank. Soak for 4 hours, then pressurize the tank with nitrogen to 1.4 MPa and maintain the pressure for 4 hours. Then pressurize the tank with nitrogen to 2.8 MPa and maintain the pressure for 3 hours.

[0058] (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 3.9 MPa. After the temperature cools down to 70°C, release the pressure to obtain the impregnated product.

[0059] Comparative Example 1

[0060] Remove step (2), and the remaining conditions are the same as in Example 6.

[0061] Comparative Example 2

[0062] Replace the deionized water in step (2) with medium-temperature liquid coal tar pitch, and keep the other conditions the same as in Example 6.

[0063] The impregnated products obtained from the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0064]

[0065]

[0066] Table 1.

[0067] As can be clearly seen from Table 1, the impregnated product obtained by the impregnation method of the present invention has a significantly better weight gain and bulk density than Comparative Example 1 and Comparative Example 2. This shows that the impregnation method of the present invention can indeed improve the unblocking effect of the pores and ultimately effectively improve the impregnation effect of the product.

[0068] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for impregnating isostatically pressed graphite, characterized in that: It includes the following steps: (1) Preheating: The isostatically pressed graphite calcined product is placed in an impregnation tank for preheating. The preheating temperature is 280℃ and the heating rate is 55℃ / h. (2) First duct clearing: Vacuum the impregnation tank for the first time to make the pressure inside the impregnation tank 250Pa, maintain the pressure for 3.5h, then inject deionized water at 75℃, introduce inert gas to pressurize to 2.2MPa, soak for 2h, then drain the deionized water, dry at 250℃ for 8h. (3) Secondary channel clearing: Vacuum the impregnation tank a second time to make the pressure inside the impregnation tank 500Pa, maintain the pressure for 5h, then fill it with nitrogen to pressurize to 0.8MPa, maintain the pressure for 5h, and vacuum the impregnation tank a second time to make the pressure inside the tank 180Pa, maintain the pressure for 6h. (4) Impregnation: Heat the liquid asphalt to 240°C and pour it into the tank. Soak for 4 hours, then pressurize the tank with nitrogen to 1.4 MPa and maintain the pressure for 4 hours. Then pressurize the tank with nitrogen to 2.8 MPa and maintain the pressure for 3 hours. (5) Cooling: Turn off the heating, drain the asphalt liquid, and at the same time fill with nitrogen and pressurize to 3.9 MPa. After the temperature cools down to 70°C, release the pressure to obtain the impregnated product.

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