A method for preparing high-purity carbon material

Abstract

The invention discloses a method for preparing a high-purity carbon material. A vacuum induction furnace device is used to perform high-temperature chemical purification on the carbon material. The process sequence of high-temperature purification first and high-temperature chemical purification later is adopted. After the early high-temperature purification, most impurities can be removed, and the material can reach a high purity of 5N level, which can greatly reduce the amount of purified gas used in the subsequent high-temperature chemical purification process. In the high-temperature chemical purification process, multiple vacuum-normal pressure oscillations are used, which is beneficial to improving the purification effect, improving the utilization rate of purified gas, reducing the amount of purified gas used, and reducing the emission of harmful gases; multiple vacuum-micro-positive pressure cycles are used, which is beneficial to removing chlorine and fluorine impurities in the purified gas.

Description

Technical Field

[0001] The present invention relates to the field of carbon material preparation, and more specifically, to a method for preparing a high-purity carbon material. Background Art

[0002] Carbon materials have many excellent properties such as corrosion resistance, radiation protection, thermal conductivity, electrical conductivity, high temperature resistance, self-lubrication, etc., and are widely used in many fields. Carbon materials can be used to prepare carbon materials, and carbon materials will drive technological revolutions in new energy, new materials and other fields. The purity of carbon materials determines its use value. The higher the purity, the greater its use value.

[0003] High-purity carbon materials refer to carbon materials with a carbon content of >99.99%. High-purity carbon material products have the characteristics of high strength, high density, high purity, high chemical stability, dense and uniform structure, high temperature resistance, high conductivity, good wear resistance, self-lubrication, etc. High-purity lightweight carbon materials have the characteristics of good thermal insulation performance, high temperature resistance, and corrosion resistance. Both can be widely used in the field of thermal field materials in thermal equipment such as semiconductor single crystal furnaces and epitaxial furnaces. At present, the high-purity carbon materials purified by existing purification technologies cannot fully meet the needs of semiconductor furnace thermal field materials in terms of purity and stability.

[0004] The Chinese invention patent with the announcement number CN105347337B discloses a method for purifying natural graphite at high temperature with Freon, comprising the following steps: loading natural graphite powder into a high temperature graphite purification furnace; evacuating the high temperature graphite purification furnace to a pressure of 100Pa or less; filling the high temperature graphite purification furnace with a protective gas to a pressure of 100 to 1000Pa higher than the atmospheric pressure; heating the high temperature graphite purification furnace at a heating rate of 4 to 20°C / min to a temperature of 1600 to 3000°C; introducing Freon gas for a holding time of 20 to 120min; after the holding time, stopping the introduction of Freon gas, cooling the high temperature graphite purification furnace at a cooling rate of 4 to 20°C / min to a temperature of room temperature, and obtaining purified graphite powder. The above technical solution can only obtain high purity graphite powder with a purity of 90.0 to 99.99% by purifying natural graphite at high temperature with Freon, which is difficult to meet the high-end needs of existing industrial production. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing high-purity carbon materials in view of the deficiencies in the prior art. The purification effect is improved by high-temperature purification, and the purity of the carbon material can be increased to 6N level, effectively solving the problem of purifying high-purity carbon materials.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing high-purity carbon material, using vacuum induction furnace equipment to perform high-temperature chemical purification on the carbon material, the steps are as follows:

[0008] S1, placing the carbon material in a vacuum induction furnace, closing the furnace cover, and after vacuum treatment, inputting inert gas into the furnace to increase the pressure in the furnace and maintain it at 600-900 Torr;

[0009] S2. Turn on the heating power supply, raise the temperature of the working area of ​​the induction furnace to 2200-3200°C, maintain the pressure in the furnace at 760-900 Torr and keep it warm, and perform high-temperature purification and graphitization treatment on the material;

[0010] S3, when the holding time is up, turn off the heating power supply, lower the furnace temperature to 2800-2200°C, turn off the inert gas, evacuate again and keep the vacuum for 5-30 minutes, then add the working gas to increase the pressure in the furnace and keep it at 600-900 Torr;

[0011] S4, turn on the heating power supply, raise the furnace temperature to 2200-3000℃ and keep it warm, and perform high-temperature chemical purification on the material;

[0012] S5. Turn off the heating power supply to reduce the furnace temperature to 2800-2000°C, turn off the working gas, evacuate the furnace body and maintain the vacuum degree, then add inert gas to increase the pressure in the furnace and maintain it at 600-900 Torr, detect the content of impurity elements in the exhaust gas of the vacuum induction furnace, if the content of impurity elements exceeds the standard, turn on the vacuum pump again and turn off the inert gas, increase the vacuum degree in the furnace to 0.01-10 Torr and maintain the vacuum degree, add inert gas again, increase the pressure in the furnace and maintain it at 600-900 Torr, detect the content of impurity elements in the gas in the furnace again, repeat the above steps until the content of impurity elements in the gas in the furnace is less than the process value, maintain the vacuum degree, wait for the furnace temperature to drop, when the furnace temperature drops to 100°C, add protective gas to increase the pressure in the furnace to 760 Torr atmosphere, open the furnace cover and take out the material to obtain high-purity carbon material.

[0013] Furthermore, the carbon material includes graphite and graphite products, carbon and carbon products, powdered graphite, graphene, carbon nanotubes, carbon nanosheets, carbon fiber and carbon fiber products, and carbon-carbon composite materials.

[0014] Furthermore, the working gas is a purified gas or a mixed gas of a purified gas and an inert gas. The purified gas is a chlorine-containing gas or / and a fluorine-containing gas, including chlorine, Freon, carbon tetrachloride and a combination thereof.

[0015] Furthermore, the inert gas includes argon or helium.

[0016] Furthermore, the protective gas includes argon or nitrogen.

[0017] Furthermore, the vacuum induction furnace includes a vertical vacuum induction furnace and a horizontal vacuum induction furnace.

[0018] Preferably, the vacuum induction furnace is a vertical vacuum induction furnace.

[0019] Furthermore, steps S3 and S4 may be cycled several times.

[0020] Furthermore, during the circulation process, the furnace temperature, the holding time and the vacuum degree can be adjusted respectively.

[0021] Furthermore, the vacuum degree of the vacuum induction furnace after vacuum treatment is 0.01 to 10 Torr.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The vertical vacuum induction furnace is used to obtain a high temperature of more than 3000°C, which is beneficial to improve the purification effect.

[0024] 2. The process sequence of high-temperature purification first and then high-temperature chemical purification is adopted. After the initial high-temperature purification, most impurities can be removed and the material can reach 5N high purity, which can greatly reduce the amount of purified gas used in the subsequent high-temperature chemical purification process.

[0025] 3. In the high-temperature chemical purification process, multiple vacuum-normal pressure oscillations are used to improve the purification effect, improve the utilization rate of purified gas, reduce the amount of purified gas used, and reduce the emission of harmful gases.

[0026] 4. After the purified gas is passed, multiple vacuum-micro-positive pressure cycles are used in a high-temperature environment, which is beneficial to remove chlorine and fluorine impurities in the purified gas, and can increase the purity of the carbon material to 6N level, effectively solving the problem of purifying high-purity carbon materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the material rack in Example 1;

[0028] Figure 2 It is a schematic diagram of the structure of the crucible in Example 2;

[0029] Figure 3 It is a schematic diagram of the structure of the graphite felt in Example 3;

[0030] Among them, 11 is a tray, 21 is a crucible, 22 is powdered graphite, 31 is a graphite sleeve, and 32 is graphite felt. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, this embodiment provides a method for preparing a semiconductor wafer epitaxial wafer graphite tray, wherein the material is isostatically pressed graphite, and the specific steps are as follows:

[0034] S1: Place the tray 11 on a rack evenly arranged up and down, place the rack and tray together in a vacuum induction furnace, close the furnace cover, turn on the vacuum pump, raise the vacuum degree in the furnace to 0.02 Torr, turn off the vacuum pump, input argon gas into the furnace, raise the pressure in the furnace to and maintain it at 750-800 Torr;

[0035] S2. Turn on the heating power supply to make the temperature of the working area of ​​the induction furnace reach 3200°C, maintain the pressure in the furnace at 750-800 Torr, and keep the temperature for 60 minutes to perform high-temperature purification and graphitization treatment on the tray;

[0036] S3. When the holding time is up, turn off the heating power supply, lower the furnace temperature to 2600°C, turn off the inert gas, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain the vacuum degree for 30 minutes, turn off the vacuum pump, add a mixed gas of Freon 22 and argon, the volume mixing ratio of Freon 22 and argon is 1:1, raise the pressure in the furnace and maintain it at 780 Torr;

[0037] S4, turning on the heating power supply to keep the furnace temperature at 3000°C for 60 minutes, and subjecting the material to high-temperature chemical purification;

[0038] S5, repeat S3 and S4 steps twice, repeating twice can make the purity higher;

[0039] S6, turn off the heating power supply to reduce the furnace temperature to 2500°C, turn off the working gas in step S4, turn on the vacuum pump, raise the vacuum degree in the furnace to 0.01 Torr and maintain it for 10 minutes, turn off the vacuum pump, add argon, raise the pressure in the furnace to 780 Torr, detect the content of chlorine and fluorine elements in the exhaust gas of the vacuum induction furnace, if the content of the elements is ≧1ppm, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain it, add inert gas again, raise the pressure in the furnace to 780 Torr, and then turn on the vacuum pump again to increase the vacuum degree in the furnace to 0.01 Torr and maintain it. The pressure is raised and maintained at 800 Torr, and the chlorine and fluorine content in the gas in the furnace is detected again. By repeatedly vacuuming-adding argon-detecting the chlorine and fluorine content in the gas in the furnace, the chlorine and fluorine content in the gas in the furnace is less than 1ppm, and the vacuum is maintained at 0.01 Torr, and the furnace temperature is waited to drop. When the furnace temperature drops to 100°C, nitrogen gas is added to raise the pressure in the furnace to 760 Torr atmospheric pressure, and the furnace cover is opened to take out the material, and a high-purity graphite tray with a carbon content greater than 99.9999% is obtained. Since absolute vacuum is difficult to achieve, this embodiment repeatedly fills in argon gas and vacuumizes, so that the argon gas produces a "flushing" effect, displacing the fluorine and chlorine-containing gases in the furnace, and finally achieving high-purity materials.

[0040] The presence of sensitive impurities such as phosphorus, boron, and aluminum in the tray will affect the performance of the semiconductor. This embodiment uses high-temperature purification above 3200°C to gasify most of the impurities. For a small amount of stubborn impurities, chemical purification is performed at 3000°C to make the impurities react chemically with chlorine and fluorine. Since the high temperature above 3000°C makes the impurities more active and reacts more fully with chemical gases, a higher purity can be achieved. This embodiment can make phosphorus, boron, and aluminum less than 0.1ppm, and even boron and aluminum less than 0.01ppm under laboratory conditions.

[0041] Example 2

[0042] like Figure 2 As shown, this embodiment provides a method for preparing high-purity carbon graphite powder, wherein the raw material is natural graphite powder or artificial graphite powder, and the specific steps are as follows:

[0043] S1: Powdered graphite 22 is placed in a crucible 21, and the crucible 21 is placed up and down in a vacuum induction furnace. The furnace cover is closed, and a vacuum pump is turned on to raise the vacuum degree in the furnace to 0.1 Torr. The vacuum pump is turned off, and argon gas is introduced into the furnace to raise the pressure in the furnace to and maintain at 760 Torr.

[0044] S2. Turn on the heating power supply to make the temperature of the working area of ​​the induction furnace reach 3100°C, maintain the pressure in the furnace at 750-800 Torr, and keep the temperature for 90 minutes to perform high-temperature purification and graphitization treatment on the powdered graphite;

[0045] S3. When the holding time is up, turn off the heating power supply, lower the furnace temperature to 2600°C, turn off the inert gas, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain the vacuum degree for 30 minutes, turn off the vacuum pump, add a mixed gas of chlorine, Freon 22, and argon in a volume ratio of 1:1:1, raise the pressure in the furnace and maintain it at 780 Torr;

[0046] S4, turning on the heating power supply to keep the furnace temperature at 3000°C for 60 minutes, and subjecting the material to high-temperature chemical purification;

[0047] S5, repeat steps S3 and S4 once;

[0048] S6, turn off the heating power supply to reduce the furnace temperature to 2500°C, turn off the working gas in step S4, turn on the vacuum pump, raise the vacuum degree in the furnace to 0.01 Torr and maintain it for 30 minutes, turn off the vacuum pump, add argon, raise the pressure in the furnace to 780 Torr, detect the content of chlorine and fluorine in the exhaust gas of the vacuum induction furnace, if the content of the elements is ≧0.5ppm, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain it, add inert gas again, raise the pressure in the furnace to 780 Torr, and detect the content of chlorine and fluorine in the exhaust gas of the vacuum induction furnace. If the content of the elements is ≧0.5ppm, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain it, add inert gas again, raise the pressure in the furnace to 780 Torr, and maintain it. Maintain the pressure at 800 Torr, detect the content of chlorine and fluorine in the gas in the furnace again, and repeat vacuuming-adding argon-detecting the content of chlorine and fluorine in the gas in the furnace until the content of chlorine and fluorine in the gas in the furnace is less than 0.5ppm. Maintain the vacuum degree at 0.01 Torr, wait for the furnace temperature to drop, and when the furnace temperature drops to 100°C, add protective gas nitrogen to raise the pressure in the furnace to 760 Torr atmosphere, open the furnace cover and take out the material crucible 21 to obtain high-purity powdered graphite with a carbon content greater than 99.9999%.

[0049] Example 3

[0050] like Figure 3 As shown, this embodiment provides a method for preparing viscose-based graphite felt, and the specific steps are as follows:

[0051] S1: Winding the viscose-based graphite felt 32 on the graphite sleeve 31, and then placing the sleeve wound with the graphite felt in a vacuum induction furnace, closing the furnace cover, turning on the vacuum pump, raising the vacuum degree in the furnace to 0.01 Torr, turning off the vacuum pump, and inputting argon gas into the furnace to raise the pressure in the furnace to and maintain it at 760 Torr;

[0052] S2. Turn on the heating power supply to make the temperature of the working area of ​​the induction furnace reach 2800°C, maintain the pressure in the furnace at 750-800 Torr, and keep the temperature for 90 minutes to perform high-temperature purification and graphitization treatment on the viscose-based graphite felt;

[0053] S3. When the holding time is up, turn off the heating power supply, lower the furnace temperature to 2550°C, turn off the inert gas, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain the vacuum degree for 30 minutes, turn off the vacuum pump, add a mixed gas of chlorine, Freon 22, and argon in a volume ratio of 1:1:1, raise the pressure in the furnace and maintain it at 780 Torr;

[0054] S4, turning on the heating power supply to keep the furnace temperature at 2800° C. for 60 minutes, and performing high-temperature chemical purification on the viscose-based graphite felt;

[0055] S5, repeat steps S3 and S4 twice;

[0056] S6, turn off the heating power supply, lower the furnace temperature to 2500°C, turn off the working gas in step S4, turn on the vacuum pump, raise the vacuum degree in the furnace to 0.01 Torr and maintain it for 30 minutes, turn off the vacuum pump, add argon, raise the pressure in the furnace to 780 Torr, detect the content of chlorine and fluorine in the exhaust gas of the vacuum induction furnace, if the content of the elements is ≧0.5ppm, turn on the vacuum pump again, raise the vacuum degree in the furnace to 0.01 Torr and maintain it, add inert gas again, raise the pressure in the furnace And maintain it at 800 Torr, detect the content of chlorine and fluorine in the gas in the furnace again, through repeated vacuuming-adding argon-detecting the content of chlorine and fluorine in the gas in the furnace, until the content of chlorine and fluorine in the gas in the furnace is less than 0.5ppm, maintain the vacuum degree at 0.01 Torr, wait for the furnace temperature to drop, when the furnace temperature drops to 100℃, add protective gas nitrogen to raise the pressure in the furnace to 760 Torr atmosphere, open the furnace cover and take out the material, to obtain high-purity viscose-based graphite felt with a carbon content greater than 99.9995%.

[0057] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0058] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A method for preparing a high-purity carbon material, characterized in that: The vacuum induction furnace equipment is used to carry out high temperature chemical purification of carbon materials. The steps are as follows: S1, placing the carbon material in a vacuum induction furnace, closing the furnace cover, and after vacuum treatment, inputting inert gas into the furnace to increase the pressure in the furnace and maintain it at 600-900 Torr; S2. Turn on the heating power supply, raise the temperature of the working area of ​​the induction furnace to 3100°C, maintain the pressure in the furnace at 760-900 Torr and keep it warm for 60-90 minutes, and perform high-temperature purification and graphitization treatment on the material; S3, when the holding time is up, turn off the heating power supply, lower the furnace temperature to 2600°C, turn off the inert gas, evacuate again and keep the vacuum for 5-30 minutes, then add a mixture of chlorine, freon and argon in a ratio of 1:1:1 to increase the pressure in the furnace and keep it at 600-900 Torr; S4, turn on the heating power supply, raise the furnace temperature to 3000°C and keep it warm, and perform high-temperature chemical purification on the material; S5, repeat S3 and S4 once; S6. Turn off the heating power supply to reduce the furnace temperature to 2800-2000°C, turn off the working gas, evacuate the furnace body and maintain the vacuum degree, then add inert gas to increase the pressure in the furnace and maintain it at 600-900 Torr, detect the content of impurity elements in the exhaust gas of the vacuum induction furnace, if the content of impurity elements exceeds the standard, turn on the vacuum pump again and turn off the inert gas, increase the vacuum degree in the furnace to 0.01-10 Torr and maintain the vacuum degree, add inert gas again, increase the pressure in the furnace and maintain it at 600-900 Torr, detect the content of impurity elements in the gas in the furnace again, repeat the above steps until the content of impurity elements in the gas in the furnace is less than the process value, maintain the vacuum degree, wait for the furnace temperature to drop, when the furnace temperature drops to 100°C, add protective gas to increase the pressure in the furnace to 760 Torr atmospheric pressure, open the furnace cover and take out the material to obtain high-purity carbon material.

2. A method for preparing a high-purity carbon material according to claim 1, characterized in that: The carbon materials include graphite and graphite products, carbon and carbon products, graphene, carbon nanotubes, carbon nanosheets, carbon fibers and carbon fiber products, and carbon-carbon composite materials.

3. The method for preparing a high-purity carbon material according to claim 1, characterized in that: The protective gas includes argon or nitrogen.

4. The method for preparing a high-purity carbon material according to claim 1, characterized in that: The vacuum induction furnace includes a vertical vacuum induction furnace and a horizontal vacuum induction furnace.

5. A method for preparing a high-purity carbon material according to claim 4, characterized in that: The vacuum induction furnace is a vertical vacuum induction furnace.

6. The method for preparing a high-purity carbon material according to claim 1, characterized in that: The vacuum degree of the vacuum induction furnace after vacuum treatment is 0.01 to 10 Torr.

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