Purification process of isostatically pressed graphite parts for electronic-grade polysilicon

Abstract

The present invention discloses a purification process for isostatically pressed graphite parts for electronic-grade polysilicon, specifically relating to the technical field of isostatically pressed graphite part purification, and includes the following specific steps: S1, antioxidant treatment, placing the isostatically pressed graphite parts in a heating furnace for heating; S2, soaking treatment; S3, cleaning treatment; S4, preparation of purification materials; S5, coating the graphite parts, placing the graphite parts in a clean and dry environment; S6, high-temperature purification treatment. The present invention forms an antioxidant soaking mixture by mixing a carbon black-filled polymer with a titanate coupling agent, a silane coupling agent, an aluminate coupling agent, and carbon black powder. This mixture can form an anti-corrosion and anti-oxidation layer on the outer wall of the isostatically pressed graphite parts for electronic-grade polysilicon, maintain the excellent electrical conductivity of the isostatically pressed graphite parts for electronic-grade polysilicon, and effectively improve the durability of the isostatically pressed graphite parts for electronic-grade polysilicon.

Description

Technical Field

[0001] The present invention relates to the technical field of isostatically pressed graphite piece purification, and more particularly to a purification process of isostatically pressed graphite pieces for electronic-grade polysilicon. Background Art

[0002] Isostatically pressed graphite parts for electronic-grade polysilicon are a type of special graphite mold used to manufacture electronic-grade polysilicon. They are made of high-purity graphite materials and are precision-machined and specially treated. Isostatically pressed graphite parts for electronic-grade polysilicon are one of the important materials for manufacturing electronic-grade polysilicon. In order to improve the quality of isostatically pressed graphite parts for electronic-grade polysilicon, they need to be purified.

[0003] The Chinese patent publication number CN101823707A discloses a process for producing isostatic graphite. The patent addresses the problem that the binder decomposes and volatilizes during the roasting process, resulting in a difference in volume shrinkage between the filler and the binder, which ultimately causes the graphite material to have high porosity, poor structural uniformity, obvious interfaces and other shortcomings, resulting in low mechanical strength of the final material. The patent uses processes such as sheeting, extrusion molding, rapid carbonization, crushing, screening, secondary kneading, sheeting, crushing, screening, preforming, isostatic pressing, roasting, impregnation, and graphitization to produce fine-grained isostatically pressed isotropic graphite material. Compared with traditional coarse-grained graphite materials, it has the characteristics of fine and dense structure, good uniformity, excellent mechanical properties, and isotropy. The process also has the following defects:

[0004] During the purification process of isostatic graphite parts for electronic-grade polysilicon, the purity of the isostatic graphite parts is improved through roasting and impregnation. However, it is difficult to oxidize and remove the external impurities of the isostatic graphite parts. In addition, the entire exterior of the isostatic graphite parts is exposed to the outside, which makes them very susceptible to oxidation and reduces their durability. Therefore, a purification process for isostatic graphite parts for electronic-grade polysilicon is provided. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a purification process for isostatically pressed graphite parts for electronic-grade polysilicon.

[0006] To achieve the above object, the present invention provides the following technical solution: a purification process for isostatically pressed graphite parts for electronic-grade polysilicon, comprising the following specific steps:

[0007] S1. Anti-oxidation treatment: Place the isostatically pressed graphite parts in a heating furnace and heat them. Fill the helium in the gas cylinder into the heating furnace. Maintain the pressure at 2-10 MPa for 5-10 minutes, then heat to 500-600°C for 5-10 minutes, and then heat to 800-900°C for 10-25 minutes.

[0008] S2. Soaking treatment: soak the treated graphite parts in an acidic solution, submerge the graphite parts in the acidic solution, heat the acidic solution to 40-60°C, soak for 10-25 minutes, take out and soak in an alkaline solution for 15-30 minutes and heat to 40-60°C for 5-10 minutes;

[0009] S3. Cleaning treatment: soak the graphite part in anhydrous ethanol, submerge the graphite part in anhydrous ethanol, gently scrub the surface of the graphite part with a soft brush, scrub the surface of the graphite part for 5-10 minutes, scrub 5-10 times, remove dirt and impurities on the surface, wipe the surface of the graphite part with a clean cloth, ensure that there is no water stain and ethanol residue on the surface, and place the graphite part in a cool and ventilated place to dry;

[0010] S4. Preparation of purified materials: 70-80 parts of barium titanate, 5-15 parts of aluminum oxide, 5-15 parts of nano-magnesium oxide, 20-35 parts of nano-ferric oxide, 5-20 parts of nano-calcium carbonate, 5-10 parts of boron nitride, and 1-5 parts of ceramic fiber are placed in a stirring tank. The stirring tank is stirred at 50-80° C. and 130-150 r / min for 5-10 minutes. Then, 1-5 parts of anhydrous ethanol is added dropwise. Then, 10-30 parts of polyimide resin and carbon black-filled polymer are added. The mixture is stirred at 150-180 r / min for 10-20 minutes to form an antioxidant soaking mixture.

[0011] S5. Graphite parts coating: The graphite parts are placed on the clean and dry workpiece surface and coated with the antioxidant soaking mixture. The mixture is applied 5-10 times with a thickness of 0.3-0.6 mm each time. After coating, the mixture is cured and placed for 5-10 minutes after cooling.

[0012] S6. High-temperature purification treatment: sprinkle silver powder on the outer surface of the solidified graphite part, use a stamping die to stamp the outer surface of the graphite part into shape, put the formed graphite part into a high-temperature furnace, fill it with helium, maintain the pressure in the high-temperature furnace at 5-10MPa, raise the temperature to 200-380℃, heat and keep warm for 30-40min, take it out and wait for it to cool to room temperature for 30-35min and then package it.

[0013] Preferably, before using the heating furnace, check whether all valves are in a tightened state, check whether the mixing switch and speed regulating heating switch of the controller are set to zero, turn on the power of the control box and its display switch, and after cleaning is completed and the kettle body is dry, cover the heating furnace, check whether the upper and lower interfaces of the heating furnace are aligned, gently turn the heating furnace cover, confirm that the kettle cover is flat and the sealing ring is in good contact, add a gasket, start tightening, first fill in the gas and check whether the pressure value on the pressure gauge changes, check 3-5 times, and before using the gas cylinder, check the bottle body for cracks and bottle valve damage, check the gas cylinder gas leakage through the pressure gauge, and then check whether the helium filling pressure is 2-10MPa. After confirmation, 2-5 people sign to confirm. If there is a problem with the gas cylinder, it needs to be replaced within 5-20 minutes. After replacement, sign to confirm that it is correct and upload the signed form.

[0014] Preferably, the acidic solution in S2 is one of manganese sulfate, hydrochloric acid, nitric acid, acetic acid, and carbonic acid. Manganese sulfate is mainly extracted from the purified manganese sulfate solution using a saponified organic phase with sulfuric acid, the manganese-rich organic phase is washed with water, and the purified manganese sulfate solution is extracted a second time using a manganese soap organic phase to obtain a high-purity manganese sulfate solution. The alkaline solution in S2 is one or two of sodium hydroxide, sodium carbonate, and sodium bicarbonate. During immersion, a grinder is used to perform rotary contact grinding on the surface of the graphite part for 5-10 minutes, and the surface is polished 5-10 times.

[0015] Preferably, the cloth in S3 needs to be soaked in antistatic liquid, and the antistatic liquid is formed by mixing 5-10 parts of acrylic acid oligomer, 10-20 parts of acrylic acid monomer, 1-5 parts of polyacrylic acid, and 2-5 parts of ionic liquid through a mixer at 50-60r / min and stirring for 5-15 minutes. After soaking, part of the antistatic liquid is precipitated using a twisted knob cloth.

[0016] Preferably, the ceramic fiber in S4 is prepared by screening and drying alumina, aluminum silicate, and magnesium oxide raw materials, and evenly mixing the processed raw materials in a ratio of 1:3:5 to form a raw material mixture. The raw material mixture is heated and melted, and the molten raw material is stretched into slender fibers by a high-speed rotating spinning disk. After spinning is completed, the fiber is transported to a curing chamber for curing treatment. The carbon black-filled polymer in S4 is 5-15 parts of a titanate coupling agent, 5-10 parts of a silane coupling agent, 10-30 parts of an aluminate coupling agent, and 5-10 parts of carbon black powder at 50-80 r / min, heated to 60-80°C, and then 5-10 parts of an epoxy resin are added and mixed for 30-40 minutes, taken out and cooled to 35-40°C for use.

[0017] Preferably, the surface drying time of the coating in S5 is 20-30 minutes, the coating surface is dried at 80°C for 10-30 minutes, and then the temperature is raised to 120-150°C and kept warm for 30-40 minutes. Each coating needs to be tested once with a temperature detector, and the specific temperature detection data is recorded. After recording, 3-5 staff members sign to confirm the temperature detection data.

[0018] Preferably, the graphite parts punched in S6 need to be placed in a stamping die so that their outer surface forms the desired shape and size, the stamped graphite parts are trimmed to remove sharp edges and corners, shaped, cleaned and dried, and the stamped graphite parts are subjected to quality inspection, including size, shape, and surface roughness.

[0019] Technical effects and advantages of the present invention:

[0020] 1. The present invention places barium titanate, aluminum oxide, nano-magnesium oxide, nano-ferric oxide, nano-calcium carbonate, boron nitride, and ceramic fiber in a stirred tank, sieves and dries the aluminum oxide, aluminum silicate, and magnesium oxide raw materials, and uniformly mixes the treated raw materials in a ratio of 1:3:5 to form a raw material mixture, adds a polyimide resin and a carbon black-filled polymer, and the carbon black-filled polymer is a mixture of a titanate coupling agent, a silane coupling agent, an aluminate coupling agent, and carbon black powder to form an antioxidant soaking mixture, which can form an anti-corrosion and anti-oxidation layer on the outer wall of the isostatically pressed graphite part for electronic-grade polycrystalline silicon, and maintains the excellent conductive properties of the isostatically pressed graphite part for electronic-grade polycrystalline silicon, and effectively improves the durability of the purified isostatically pressed graphite part for electronic-grade polycrystalline silicon;

[0021] 2. The present invention soaks the graphite piece in anhydrous ethanol, gently scrubs the surface of the graphite piece with a soft brush, scrubs the surface of the graphite piece at the position where it is attached to the surface of the graphite piece to remove surface dirt and impurities, wipes the surface of the graphite piece with a clean cloth, and soaks it in an antistatic liquid. The antistatic liquid is mixed by an acrylic acid oligomer, an acrylic acid monomer, polyacrylic acid, and an ionic liquid through a mixer. After soaking, part of the antistatic liquid is precipitated with a twisted knob cloth. After wiping, the problem of adsorbing impurities on the isostatic graphite piece for electronic-grade polycrystalline silicon is avoided, which causes contamination of the outer wall of the isostatic graphite piece for electronic-grade polycrystalline silicon. Fewer impurities are generated during the purification of the isostatic graphite piece for electronic-grade polycrystalline silicon, thereby effectively improving the purification effect of the isostatic graphite piece for electronic-grade polycrystalline silicon.

[0022] 3. The present invention mainly soaks the treated graphite parts in an acidic solution, which is manganese sulfate. The manganese sulfate is mainly extracted from the purified manganese sulfate solution by using sulfuric acid to saponify the organic phase, the manganese-rich organic phase is washed with water, and the purified manganese sulfate solution is extracted for the second time using a manganese soap organic phase to obtain a high-purity manganese sulfate solution. The acidic solution is heated and soaked, and then taken out and soaked in an alkaline solution. During the soaking, a grinder is used to rotate and contact grind the surface of the graphite parts, which can form an acid-alkali double-step treatment on the outside of the graphite parts, and the oxidation residue on the surface of the graphite parts is reacted and treated, thereby improving the purity of isostatically pressed graphite parts for electronic-grade polysilicon.

[0023] Through the mutual influence of the above-mentioned multiple effects, first, an acid-alkaline double-step treatment is formed on the outside of the graphite part, and the oxidation residue on the surface of the graphite part is reaction-treated. Then, an anti-corrosion and anti-oxidation layer is formed on the outer wall of the entire isostatically pressed graphite part for electronic-grade polycrystalline silicon, and the isostatically pressed graphite part for electronic-grade polycrystalline silicon is maintained to have excellent conductive properties. Finally, after wiping, the problem of adsorbed impurities on the isostatically pressed graphite part for electronic-grade polycrystalline silicon is avoided, which causes contamination of the outer wall of the isostatically pressed graphite part for electronic-grade polycrystalline silicon. In summary, the external impurities of the isostatically pressed graphite part can be oxidized and removed, and an anti-oxidation and anti-corrosion layer is formed on the outside of the isostatically pressed graphite part, which is not easy to oxidize in the later period and has better durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic diagram of the purification process flow of isostatically pressed graphite parts for electronic-grade polysilicon. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0026] As attached Figure 1 The purification process of isostatically pressed graphite parts for electronic grade polysilicon is shown in three sets of embodiments as follows:

[0027] Example 1:

[0028] A purification process for isostatically pressed graphite parts for electronic-grade polysilicon comprises the following specific steps:

[0029] S1. Anti-oxidation treatment. Place the isostatic graphite parts in the heating furnace for heating. Before using the heating furnace, check whether all valves are tightened, check whether the mixing switch and speed regulating heating switch of the controller are set to zero, turn on the power of the control box and its display switch, clean and dry the kettle body, cover the heating furnace, check whether the upper and lower interfaces of the heating furnace are aligned, gently turn the heating furnace cover, confirm that the kettle cover is flat, the sealing ring is in good contact, and add gaskets, start tightening, first fill in gas and check whether the pressure value of the pressure gauge is Changes occur, check 3 times, fill the helium in the gas cylinder into the heating furnace, check the cylinder for cracks and damage to the cylinder valve before use, check the gas cylinder for leakage through the pressure gauge, and then check whether the helium filling pressure is 2MPa. After confirmation, two people sign to confirm. If there is a problem with the gas cylinder, it needs to be replaced within 5 minutes. After replacement, sign to confirm that it is correct and upload the signed form. Under 2MPa pressure, maintain pressure for 5 minutes, heat to 500℃ and keep warm for 5 minutes, then increase the temperature to 800℃ and keep warm for 10 minutes;

[0030] S2, soaking treatment, soaking the treated graphite parts in an acidic solution, the acidic solution is manganese sulfate, and the manganese sulfate solution is purified by manganese soap organic phase for a second extraction to obtain a high-purity manganese sulfate solution, submerging the graphite parts in the acidic solution, heating the acidic solution to 40°C, soaking for 10 minutes, taking out and soaking in an alkaline solution for 15 minutes, the alkaline solution is sodium hydroxide, and the surface of the graphite parts is rotary contact polished by a grinder for 5 minutes, the surface is polished 5 times, and heated to 40°C for 5 minutes;

[0031] S3, cleaning treatment, soak the graphite part in anhydrous ethanol, anhydrous ethanol submerges the graphite part, gently scrub the surface of the graphite part with a soft brush, scrub the surface of the graphite part for 5 minutes, scrub 5 times, remove surface dirt and impurities, wipe the surface of the graphite part with a clean cloth, the cloth needs to be soaked in antistatic liquid, and the antistatic liquid is formed by mixing 5 parts of acrylic acid oligomer, 10 parts of acrylic acid monomer, 1 part of polyacrylic acid, and 2 parts of ionic liquid through a mixer at 50r / min, stirring for 5 minutes, and then a portion of the antistatic liquid is precipitated with a twisted knob cloth after soaking to ensure that there is no water stain and ethanol residue on the surface. The graphite part is placed in a cool and ventilated place to dry;

[0032] S4, preparation of purified materials, 70 parts of barium titanate, 5 parts of aluminum oxide, 5 parts of nano magnesium oxide, 20 parts of nano ferric oxide, 5 parts of nano calcium carbonate, 5 parts of boron nitride, and 1 part of ceramic fiber are placed in a stirring tank, the aluminum oxide, aluminum silicate, and magnesium oxide raw materials are sieved and dried, and the treated raw materials are evenly mixed in a ratio of 1:3:5 to form a raw material mixture, the raw material mixture is heated and melted, and the molten raw material is stretched into slender fibers by a high-speed rotating spinning disk. After the spinning is completed, the fiber is transported to a curing chamber for Curing treatment: After stirring the stirred tank at 50°C and 130r / min for 5 minutes, 1 part of anhydrous ethanol was added dropwise, and then 10 parts of polyimide resin and carbon black filled polymer were added. The carbon black filled polymer was 5 parts of titanate coupling agent, 5 parts of silane coupling agent, 10 parts of aluminate coupling agent, and 5 parts of carbon black powder. The mixture was heated to 60°C at 50r / min, and then 5 parts of epoxy resin was added and mixed for 30 minutes. The mixture was taken out and cooled to 35°C for use, and stirred at 150r / min for 10 minutes to form an antioxidant impregnation mixture.

[0033] S5. Graphite coating: The graphite parts are placed on the clean and dry workpiece surface and coated with the antioxidant soaking mixture. The coating is applied 5 times with a thickness of 0.3 mm each time. The surface drying time of each coating is 20 minutes. The coating surface is dried at 80°C for 10 minutes, and then heated to 120°C and kept warm for 30 minutes. Each coating needs to be tested once with a temperature detector, and the specific temperature detection data is recorded. After recording, the temperature detection data is signed by 3 staff members to confirm. After coating, it is cured and placed for 5 minutes after cooling;

[0034] S6. High-temperature purification treatment. Silver powder is sprinkled on the outer surface of the solidified graphite part. The outer surface of the graphite part is stamped into shape using a stamping die. The stamped graphite part needs to be placed in the stamping die so that its outer surface forms the required shape and size. The stamped graphite part is trimmed to remove edges and corners, shaped, cleaned and dried. The stamped graphite part is quality inspected, including size, shape, and surface roughness. After molding, the graphite part is placed in a high-temperature furnace, filled with helium, and the pressure in the high-temperature furnace is maintained at 5MPa. The temperature is raised to 200℃ and heated for 30 minutes. It is taken out and cooled to room temperature for 30 minutes and then packaged.

[0035] Example 2:

[0036] A purification process for isostatically pressed graphite parts for electronic-grade polysilicon comprises the following specific steps:

[0037] S1. Anti-oxidation treatment. Place the isostatic graphite parts in the heating furnace for heating. Before using the heating furnace, check whether all valves are tightened, check whether the mixing switch and speed regulating heating switch of the controller are set to zero, turn on the power of the control box and its display switch, clean and dry the kettle body, cover the heating furnace, check whether the upper and lower interfaces of the heating furnace are aligned, gently turn the heating furnace cover, confirm that the kettle cover is flat, the sealing ring is in good contact, and add gaskets, start tightening, first fill in gas and check whether the pressure value of the pressure gauge is Changes occur, check 4 times, fill the helium in the gas cylinder into the heating furnace, check the cylinder for cracks and damage to the cylinder valve before use, check the gas cylinder for leakage through the pressure gauge, and then check whether the helium filling pressure is 8MPa. After confirmation, 4 people sign to confirm. If there is a problem with the gas cylinder, it needs to be replaced within 10 minutes. After replacement, sign to confirm that it is correct and upload the signed form. Under 8MPa pressure, maintain pressure for 8 minutes, heat to 400℃ and keep warm for 8 minutes, then increase the temperature to 850℃ and keep warm for 15 minutes;

[0038] S2, soaking treatment, soaking the treated graphite parts in an acidic solution, the acidic solution is manganese sulfate, the manganese sulfate is mainly extracted by using sulfuric acid to saponify the organic phase to purify the manganese sulfate solution, the manganese-rich organic phase is washed with water, and the purified manganese sulfate solution is extracted a second time using a manganese soap organic phase, the acidic solution is heated to 50° C., soaked for 15 minutes, taken out and placed in an alkaline solution for 20 minutes, the alkaline solution is sodium bicarbonate, and the surface of the graphite parts is rotary contact polished by a grinder during soaking for 8 minutes, the surface is polished 8 times, and heated to 50° C. for 8 minutes;

[0039] S3, cleaning treatment, soak the graphite part in anhydrous ethanol, anhydrous ethanol submerges the graphite part, gently scrub the surface of the graphite part with a soft brush, scrub the surface of the graphite part for 8 minutes, scrub 8 times, remove surface dirt and impurities, wipe the surface of the graphite part with a clean cloth, the cloth needs to be soaked in antistatic liquid, and the antistatic liquid is formed by mixing 8 parts of acrylic acid oligomer, 15 parts of acrylic acid monomer, 4 parts of polyacrylic acid, and 4 parts of ionic liquid through a mixer at 55r / min, stirring for 10 minutes, and after soaking, part of the antistatic liquid is precipitated with a twisted knob cloth to ensure that there is no water stain and ethanol residue on the surface, and the graphite part is placed in a cool and ventilated place to dry;

[0040] S4. Preparation of purified materials: 75 parts of barium titanate, 10 parts of aluminum oxide, 10 parts of nano-magnesium oxide, 30 parts of nano-ferric oxide, 15 parts of nano-calcium carbonate, 8 parts of boron nitride, and 4 parts of ceramic fiber are placed in a stirring tank. The raw materials of aluminum oxide, aluminum silicate, and magnesium oxide are sieved and dried, and the treated raw materials are evenly mixed in a ratio of 1:3:5 to form a raw material mixture. The raw material mixture is heated and melted, and the molten raw material is stretched into slender fibers through a high-speed rotating spinning disk. After spinning is completed, the fibers are transported to a curing chamber. Curing treatment was carried out, the stirring kettle was stirred at 70°C at 140r / min for 8min, 3 parts of anhydrous ethanol was added dropwise, and then 20 parts of polyimide resin and carbon black filled polymer were added, the carbon black filled polymer was 10 parts of titanate coupling agent, 8 parts of silane coupling agent, 15 parts of aluminate coupling agent, and 8 parts of carbon black powder at 70 / min, heated to 70°C, and then 8 parts of epoxy resin was added and mixed for 35min, taken out and cooled to 40°C for use, and stirred at 160r / min for 15min to form an antioxidant impregnation mixture;

[0041] S5. Graphite parts coating: The graphite parts are placed on the clean and dry workpiece surface and coated with the antioxidant soaking mixture. The coating is applied 8 times with a thickness of 0.5 mm each time. The surface drying time of each coating is 25 minutes. The coating surface is dried at 80°C for 15 minutes, and then heated to 130°C and kept warm for 35 minutes. Each coating needs to be tested once with a temperature detector, and the specific temperature detection data is recorded. After recording, the temperature detection data is signed by 4 staff members. After coating, it is cured and placed for 8 minutes after cooling;

[0042] S6. High-temperature purification treatment. Silver powder is sprinkled on the outer surface of the solidified graphite part. The outer surface of the graphite part is stamped into shape using a stamping die. The stamped graphite part needs to be placed in the stamping die so that its outer surface forms the required shape and size. The stamped graphite part is trimmed to remove edges and corners, shaped, cleaned and dried. The stamped graphite part is quality inspected, including size, shape, and surface roughness. After molding, the graphite part is placed in a high-temperature furnace, filled with helium, and the pressure in the high-temperature furnace is maintained at 8MPa. The temperature is raised to 300℃ and heated for 35 minutes. It is taken out and cooled to room temperature for 35 minutes and then packaged.

[0043] Example 3:

[0044] A purification process for isostatically pressed graphite parts for electronic-grade polysilicon comprises the following specific steps:

[0045] S1. Anti-oxidation treatment: Place the isostatic graphite parts in the heating furnace for heating. Before using the heating furnace, check whether all valves are tightened, check whether the mixing switch and speed regulating heating switch of the controller are set to zero, turn on the power of the control box and its display switch, clean and dry the kettle body, cover the heating furnace, check whether the upper and lower interfaces of the heating furnace are aligned, gently turn the heating furnace cover, confirm that the kettle cover is flat and the sealing ring is in good contact, add gaskets, start tightening, first fill in gas and check whether the pressure value of the pressure gauge changes. After 5 inspections, the helium in the gas cylinder is filled into the heating furnace. Before using the gas cylinder, check the cylinder for cracks and damage to the valve. Use the pressure gauge to check whether the gas cylinder is leaking. Then check whether the helium filling pressure is 10MPa. After confirmation, 5 people sign to confirm. If there is a problem with the gas cylinder, it needs to be replaced within 20 minutes. After replacement, sign to confirm that it is correct and upload the signed form. Under 10MPa pressure, maintain the pressure for 10 minutes, heat to 600℃ and keep it for 10 minutes, then increase the temperature to 900℃ and keep it for 25 minutes.

[0046] S2, soaking treatment, soaking the treated graphite parts in an acidic solution, the acidic solution is manganese sulfate, the manganese sulfate is mainly extracted by using sulfuric acid to saponify the organic phase to purify the manganese sulfate solution, the manganese-rich organic phase is washed with water, and the purified manganese sulfate solution is extracted a second time using a manganese soap organic phase to obtain a high-purity manganese sulfate solution, the acidic solution is submerged in the graphite parts, the acidic solution is heated to 60° C., soaked for 25 minutes, taken out and soaked in an alkaline solution for 30 minutes, the alkaline solution is sodium carbonate, and the surface of the graphite parts is subjected to rotary contact grinding with a grinder during soaking, grinding for 10 minutes, the surface is polished 10 times, and heated to 60° C. for 10 minutes;

[0047] S3, cleaning treatment, soak the graphite part in anhydrous ethanol, anhydrous ethanol submerges the graphite part, gently scrub the surface of the graphite part with a soft brush, scrub the surface of the graphite part for 10 minutes, scrub 10 times, remove surface dirt and impurities, wipe the surface of the graphite part with a clean cloth, the cloth needs to be soaked in antistatic liquid, and the antistatic liquid is formed by mixing 10 parts of acrylic acid oligomer, 20 parts of acrylic acid monomer, 5 parts of polyacrylic acid, and 5 parts of ionic liquid through a mixer at 60r / min, stirring for 15 minutes, and after soaking, part of the antistatic liquid is precipitated with a twisted knob cloth to ensure that there is no water stain and ethanol residue on the surface, and the graphite part is placed in a cool and ventilated place to dry;

[0048] S4, preparation of purified materials, 80 parts of barium titanate, 15 parts of aluminum oxide, 15 parts of nano magnesium oxide, 35 parts of nano ferric oxide, 20 parts of nano calcium carbonate, 10 parts of boron nitride, and 5 parts of ceramic fiber are placed in a stirring tank, the aluminum oxide, aluminum silicate, and magnesium oxide raw materials are sieved and dried, and the treated raw materials are evenly mixed in a ratio of 1:3:5 to form a raw material mixture, the raw material mixture is heated and melted, and the molten raw material is stretched into slender fibers by a high-speed rotating spinning disk. After the spinning is completed, the fiber is transported to a curing chamber for Curing treatment: After stirring the stirred kettle at 80°C and 150r / min for 10 minutes, 5 parts of anhydrous ethanol were added dropwise, and then 30 parts of polyimide resin and carbon black filled polymer were added. The carbon black filled polymer was 15 parts of titanate coupling agent, 10 parts of silane coupling agent, 30 parts of aluminate coupling agent, and 10 parts of carbon black powder. The mixture was heated to 80°C at 80r / min, and then 10 parts of epoxy resin was added and mixed for 40 minutes. The mixture was taken out and cooled to 40°C for use, and stirred at 180r / min for 20 minutes to form an antioxidant impregnation mixture.

[0049] S5. Graphite coating: The graphite parts are placed on the clean and dry workpiece surface and coated with the antioxidant soaking mixture. The coating is applied 10 times with a thickness of 0.6 mm each time. The surface drying time of each coating is 30 minutes. The coating surface is dried at 80°C for 30 minutes, and then heated to 150°C and kept warm for 40 minutes. Each coating needs to be tested once with a temperature detector, and the specific temperature detection data is recorded. After recording, the temperature detection data is signed by 5 staff members to confirm. After coating, it is cured and placed for 10 minutes after cooling;

[0050] S6. High-temperature purification treatment. Silver powder is sprinkled on the outer surface of the solidified graphite part. The outer surface of the graphite part is stamped into shape using a stamping die. The graphite part needs to be placed in the stamping die to form the outer surface into the required shape and size. The stamped graphite part is trimmed to remove edges and corners, shaped, cleaned and dried. The stamped graphite part is quality inspected, including size, shape, and surface roughness. After molding, the graphite part is placed in a high-temperature furnace, filled with helium, and the pressure in the high-temperature furnace is maintained at 10MPa. The temperature is raised to 380℃ and heated for 40 minutes. It is taken out and cooled to room temperature for 35 minutes and packaged.

[0051] During the testing process of the above three groups of examples, the purified electronic-grade polysilicon in the three groups of examples was tested with isostatically pressed graphite parts for thermal conductivity, thermal expansion coefficient, resistivity, flexural strength, and compressive strength, and the following results were obtained:

[0052]

[0053] Based on the above table, the thermal conductivity of Example 2 is significantly better than that of Example 1 and Example 3, and the thermal expansion coefficient of Example 2 is significantly better than that of Example 1 and Example 3, while the resistivity of Example 2 is the smallest. The electrical conductivity of Example 2 is significantly better than that of Example 1 and Example 3, and the bending strength and compressive strength of Example 2 are significantly better than those of Example 1 and Example 3. Therefore, the outside of the graphite part is treated with an acid double-step alkali step, and the oxidation residue on the surface of the graphite part is reacted. Then, a layer of corrosion-resistant and oxidation-resistant layer is formed on the outer wall of the isostatically pressed graphite part for electronic-grade polycrystalline silicon, and the isostatically pressed graphite part for electronic-grade polycrystalline silicon has excellent electrical conductivity. Finally, after wiping, the problem of adsorbing impurities on the isostatically pressed graphite part for electronic-grade polycrystalline silicon is avoided, which causes contamination of the outer wall of the isostatically pressed graphite part for electronic-grade polycrystalline silicon. The impurities on the outside of the isostatically pressed graphite part can be oxidized and removed, and an oxidation-resistant and corrosion-resistant layer is formed on the outside of the isostatically pressed graphite part, which is not easily oxidized in the later stage and has better durability.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A purification process for isostatically pressed graphite parts for electronic-grade polysilicon, characterized by: The specific steps are as follows: S1. Anti-oxidation treatment: Place the isostatically pressed graphite parts in a heating furnace and heat them. Fill the helium in the gas cylinder into the heating furnace. Maintain the pressure at 2-10 MPa for 5-10 minutes, then heat to 500-600°C for 5-10 minutes, and then heat to 800-900°C for 10-25 minutes. S2. Soaking treatment: soak the treated graphite parts in an acidic solution, submerge the graphite parts in the acidic solution, heat the acidic solution to 40-60°C, soak for 10-25 minutes, take out and soak in an alkaline solution for 15-30 minutes and heat to 40-60°C for 5-10 minutes; S3. Cleaning treatment: soak the graphite part in anhydrous ethanol, submerge the graphite part in anhydrous ethanol, gently scrub the surface of the graphite part with a soft brush, scrub the surface of the graphite part for 5-10 minutes, scrub 5-10 times, remove dirt and impurities on the surface, wipe the surface of the graphite part with a clean cloth, ensure that there is no water stain and ethanol residue on the surface, and place the graphite part in a cool and ventilated place to dry; S4, preparation of purified materials, 70-80 parts of barium titanate, 5-15 parts of aluminum oxide, 5-15 parts of nano magnesium oxide, 20-35 parts of nano ferric oxide, 5-20 parts of nano calcium carbonate, 5-10 parts of boron nitride, 1-5 parts of ceramic fiber are placed in a stirring tank, the stirring tank is stirred at 50-80 ° C, according to 130-150 r / min, after 5-10 minutes, 1-5 parts of anhydrous ethanol are added dropwise, and then 10-30 parts of polyimide resin and A carbon black-filled polymer, wherein the carbon black-filled polymer comprises 5-15 parts of a titanate coupling agent, 5-10 parts of a silane coupling agent, 10-30 parts of an aluminate coupling agent, and 5-10 parts of carbon black powder, heated to 60-80° C. at 50-80 r / min, and then 5-10 parts of an epoxy resin is added and mixed for 30-40 minutes. The mixture is then taken out and cooled to 35-40° C. for later use, and stirred at 150-180 r / min for 10-20 minutes to form an antioxidant impregnation mixture; S5. Graphite parts coating: The graphite parts are placed on the clean and dry workpiece surface and coated with the antioxidant soaking mixture. The mixture is applied 5-10 times with a thickness of 0.3-0.6 mm each time. After coating, the mixture is cured and placed for 5-10 minutes after cooling. S6. High-temperature purification treatment: sprinkle silver powder on the outer surface of the solidified graphite part, use a stamping die to stamp the outer surface of the graphite part into shape, put the formed graphite part into a high-temperature furnace, fill it with helium, maintain the pressure in the high-temperature furnace at 5-10MPa, raise the temperature to 200-380℃, heat and keep warm for 30-40min, take it out and wait for it to cool to room temperature for 30-35min and then package it.

2. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: Before using the heating furnace, check whether all valves are tightened, check whether the mixing switch and speed regulation heating switch of the controller are set to zero, turn on the power of the control box and its display switch, and after cleaning and the kettle body is dry, cover the heating furnace and check whether the upper and lower interfaces of the heating furnace are aligned. Gently turn the heating furnace cover to confirm that the kettle cover is flat and the sealing ring is in good contact, add gaskets, and start tightening. First fill in gas and check whether the pressure value on the pressure gauge changes. Check 3-5 times.

3. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: Before using the gas cylinder, check the cylinder body for cracks and valve damage, use a pressure gauge to check whether the cylinder gas is leaking, and then check whether the helium filling pressure is 2-10MPa. After confirmation, 2-5 people will sign to confirm. If there is a problem with the cylinder, it needs to be replaced within 5-20 minutes. After replacement, sign to confirm that it is correct and upload the signed form.

4. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: The acidic solution in S2 is one of manganese sulfate, hydrochloric acid, nitric acid, acetic acid, and carbonic acid. Manganese sulfate is mainly extracted from the purified manganese sulfate solution by using sulfuric acid to saponify the organic phase, the manganese-rich organic phase is washed with water, and the purified manganese sulfate solution is extracted for the second time using a manganese soap organic phase to obtain a high-purity manganese sulfate solution.

5. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: The alkaline solution in S2 is one or two of sodium hydroxide, sodium carbonate, and sodium bicarbonate. During the soaking, a grinder is used to rotate and contact grind the surface of the graphite part for 5-10 minutes and 5-10 times.

6. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: The cloth in S3 needs to be soaked in antistatic liquid, and the antistatic liquid is formed by mixing 5-10 parts of acrylic acid oligomer, 10-20 parts of acrylic acid monomer, 1-5 parts of polyacrylic acid, and 2-5 parts of ionic liquid through a mixer at 50-60r / min and stirring for 5-15 minutes. After soaking, part of the antistatic liquid is precipitated using a twisted knob cloth.

7. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: In the ceramic fiber S4, the raw materials of alumina, aluminum silicate and magnesium oxide are screened and dried, and the processed raw materials are evenly mixed in a ratio of 1:3:5 to form a raw material mixture. The raw material mixture is heated and melted, and the molten raw material is stretched into slender fibers through a high-speed rotating spinning disk. After spinning is completed, the fibers are transported to a curing chamber for curing treatment.

8. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: The surface drying time of the coating in S5 is 20-30 minutes. The coating surface is dried at 80°C for 10-30 minutes, and then the temperature is raised to 120-150°C and kept warm for 30-40 minutes. Each time the coating is applied, a temperature detector is used to detect the surface, and the specific temperature detection data is recorded. After recording, 3-5 staff members sign to confirm the temperature detection data.

9. The purification process of isostatically pressed graphite parts for electronic-grade polysilicon according to claim 1, characterized in that: The stamped graphite parts in S6 need to be placed in a stamping die so that their outer surface forms the required shape and size. The stamped graphite parts are trimmed to remove sharp edges and corners, shaped, cleaned and dried, and the stamped graphite parts are inspected for quality, including size, shape, and surface roughness.

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