Preparation method of glassy carbon graphite electrode

Abstract

This invention provides a method for preparing a glassy carbon graphite electrode, comprising: S1, preparing a graphite electrode; S2, preparing a glassy carbon graphite electrode: step S2 specifically includes: S21, coating the surface of the graphite electrode prepared in step S1 with phenolic resin; S22, curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature to obtain a graphite electrode coated with a glassy carbon precursor; S23, carbonizing the graphite electrode coated with the glassy carbon precursor obtained in step S22 in an oxygen-free environment at a high temperature of 1000℃ to obtain a primary glassy carbon graphite electrode product; S24, heat-treating the primary glassy carbon graphite electrode product obtained in step S23 at a high temperature of 2000℃~3000℃ to obtain a high-purity glassy carbon graphite electrode. This invention, by coating the surface of the graphite electrode with a glassy carbon layer, can form a protective layer on the surface of the graphite electrode, preventing graphite in the graphite electrode from escaping at high temperatures, thereby reducing the carbon content in the polycrystalline silicon rod.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of graphite electrode, in particular to a preparation method of glassy carbon graphite electrode BACKGROUND

[0002] Polysilicon production uses reduction furnace, the electrode in the reduction furnace passes through the reduction furnace bottom plate, and the silicon core is fixed on the electrode through the graphite sleeve and the insulating ceramic ring sleeve. Then, the silicon core is heated by connecting the current through the electrode, so as to reach the temperature required for reduction and deposition.

[0003] During the polysilicon reduction furnace production process, the carbon elements on the surface of the high-purity graphite electrode will partially volatilize and precipitate in the polysilicon rod with the production of the silicon rod, increasing the carbon content of the polysilicon rod, which causes the product quality to fail to meet the demand of the domestic high-end market. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of glassy carbon graphite electrode, which is used for polysilicon production using reduction furnace to produce polysilicon, reduces the volatilization of carbon elements of the graphite electrode, and thus reduces the carbon element content in the polysilicon rod. The present application is realized through the following technical solutions.

[0005] A preparation method of glassy carbon graphite electrode, characterized in that it comprises:

[0006] S1, preparing a graphite electrode; S2, preparing a glassy carbon graphite electrode:

[0007] The step S2 specifically comprises:

[0008] S21, coating phenolic resin on the surface of the graphite electrode prepared in step S1;

[0009] S22, obtaining the graphite electrode coated with glassy carbon precursor after curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature;

[0010] S23, carbonizing the graphite electrode coated with glassy carbon precursor obtained in step S22 at 1000 DEG C high temperature in an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0011] S24, obtaining a high-purity glassy carbon graphite electrode after heat treatment of the glassy carbon graphite electrode primary product obtained in step S23 at 2000-3000 DEG C high temperature.

[0012] The present application coats a glassy carbon layer on the surface of the graphite electrode. The glassy carbon has the properties of air impermeability, chemical inertness, high oxidation resistance, friction resistance, high temperature resistance, etc. It can form a protective layer on the surface of the graphite electrode, prevent the graphite in the graphite electrode from overflowing outward at high temperature, and reduce the carbon element content in the polysilicon rod.

[0013] In the process of coating the phenolic resin coating on the glass carbon, the phenolic resin coating is first cured at room temperature, and then slowly heated, so as to avoid the generation of pores in the green body.

[0014] Further, in order to form a dense layer on the outer side of the graphite electrode, after the graphite electrode is prepared in the step S1, an HfC layer is prepared on the surface of the graphite electrode, and the specific method is as follows:

[0015] S11, preparing a graphite electrode;

[0016] S12, uniformly mixing Hf, HfO2 and NH4Cl powders in a molar ratio of Hf:HfO2:NH4Cl=4:5:3, placing the mixed powders in a gas deposition furnace, suspending the graphite electrode above the powders, continuously introducing hydrogen into the gas deposition furnace, keeping the oxygen-free pressure in the furnace at 1.8kPa, and slowly heating the gas deposition furnace to 1500℃, so that the gas generated by the powders interacts with the graphite electrode and generates an HfC coating on the surface of the graphite electrode.

[0017] The technical scheme selects Hf, HfO2 and NH4Cl as raw materials to prepare an HfC gradient coating on the surface of the graphite electrode by gas infiltration.

[0018] Coating phenolic resin on the surface of the HfC coating can make the bonding force between the glass carbon covering the surface of the graphite electrode and the graphite electrode better.

[0019] Further, in order to make the glass carbon smooth and uniform on the surface of the graphite electrode, in the step S21, the thickness of the phenolic resin coating on the surface of the graphite electrode is 1-3mm.

[0020] In the step S24, the glass carbon graphite electrode primary product obtained in the step S23 is heat treated at a high temperature of 2000-3000℃ for 1-2h.

[0021] In the step S12 of preparing the HfC coating, the slow heating process of the gas deposition furnace is 400℃ for 40min, 800-1000℃ for 60min, and 1200-1500℃ for 4h. The temperature rising time is 40min from 400-800℃, and 40min from 1000-1200℃.

[0022] Due to the heating process of the HfC coating prepared from Hf, NH4Cl, different substances are generated at different temperature stages, especially at the normal temperature-400℃ stage, the reactant heating can generate H2, which can reduce the use amount of hydrogen in the reaction process. At this stage, the reactant heating generates HCl, HfC, H2, etc.; at the 800℃-1000℃ stage, HfC is decomposed into Hf and HfCl4; and at the 1200℃-1500℃ stage, HfC is directly generated. In the process, Hf and HfCl4 gas react to generate HfCl3 gas, which reacts with C on the surface layer of the graphite electrode under the action of hydrogen to generate HfC and HCl gas, and HfC directly penetrates into the surface layer of the graphite electrode.

[0023] Therefore, the present application adopts the slow heating in stages, which is beneficial to promote the generation of the direct reactant for preparing HfC.

[0024] On the other hand, the present application also provides a glass carbon graphite electrode, which comprises: a graphite electrode, an HfC coating located on the outer surface of the graphite electrode, and a glass carbon layer coated outside the HfC coating.

[0025] The thickness of the HfC coating is >150μm, and the thickness of the glass carbon layer is 0.5-2mm.

[0026] The present application has the following beneficial effects:

[0027] 1. The present application coats a glass carbon layer on the surface of the graphite electrode, and the glass carbon has the properties of gas impermeability, chemical inertness, high oxidation resistance, friction resistance, high temperature resistance, etc., which can form a protective layer on the surface of the graphite electrode to prevent the graphite in the graphite electrode from overflowing outward at high temperature, thereby reducing the carbon element content in the polysilicon rod. In the process of coating the phenolic resin coating on the glass carbon, the present application first cures the phenolic resin coating at normal temperature, and then slowly heats, so as to avoid the generation of pores in the green body.

[0028] 2. In order to further improve the bonding force between the glass carbon layer and the graphite electrode, Hf, HfO2, and NH4Cl are selected as raw materials to prepare an HfC gradient coating on the surface layer of the graphite electrode by the gas infiltration method. The phenolic resin is coated on the surface of the HfC coating, so that the bonding force between the glass carbon coated on the surface of the graphite electrode and the graphite electrode is better.

[0029] 3. Due to the heating process of the preparation of HfC coating layer from Hf, NH4Cl, the substances generated at different temperature stages are different, especially at room temperature-400℃ stage, the heating of reactants can generate H2, which can reduce the use amount of hydrogen in the reaction process. At this stage, the heating of reactants generates HCl, HfC, H2, etc. At 800℃-1000℃ stage, HfC decomposes into Hf and HfCl4, and at 1200℃-1500℃ stage, it is a direct step to generate HfC. In the process, Hf and HfCl4 gas react to generate HfCl3 gas, which reacts with C on the surface layer of the graphite electrode under the action of hydrogen to generate HfC and HCl gas, and HfC directly penetrates into the surface layer of the graphite electrode. The present application adopts slow heating in stages, which is conducive to promoting the generation of direct reactants for preparing HfC. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be described below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "include" and "have" and any variations thereof, as used in the specification and claims of this application, are intended to cover the case where the stated elements are present, but not to exclude the presence of additional elements.

[0032] The "range" disclosed in the present application is limited in the form of lower limit and upper limit, a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include or not include the end value, and can be arbitrarily combined, i.e. any lower limit can be combined with any upper limit to form a range. In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand notation for any real combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been listed herein, and "0-5" is a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] At present, in the production process of polycrystalline silicon reduction furnace, the carbon elements on the surface of high-purity graphite electrode will partially volatilize and precipitate in the polycrystalline silicon rod with the production of silicon rod, increasing the carbon content of the polycrystalline silicon rod

[0034] The present application inventors, in order to solve this problem, propose the glassy carbon graphite electrode preparation method of the present application, the process is:

[0035] S1, preparing a graphite electrode;

[0036] S2, preparing a glassy carbon graphite electrode:

[0037] In the following examples, the method for preparing a graphite electrode is:

[0038] 1. 30 parts of stone tar, 40 parts of needle coke, 25 parts of anthracite, and 5 parts of coal pitch are used as raw materials, and calcination is carried out under air isolation conditions, with a calcination temperature of 1300°C.

[0039] 2. The calcined raw materials are crushed to obtain carbonaceous particle breakage of different sizes, and the breakage with a particle size range of 0.3-1.0 mm and 1.0-1.5 mm is mixed in a ratio of 1:3.

[0040] 3. The above mixture is dry mixed at 170°C for 30 minutes to obtain a paste.

[0041] 4. The paste is cooled to 110°C, and after holding for 20 minutes, it is placed in an extruder for pre-pressing for 5 minutes at a pressure of 30Mpa. Then, the green product is pressed into a rod shape, and the pressed green product is baked in a heating furnace under air isolation conditions to obtain a graphite electrode.

[0042] In order to more clearly illustrate the technical solutions of the present application, the following specific embodiments of the present application are given.

[0043] Example 1

[0044] The preparation method of the glassy carbon graphite electrode, the specific process is:

[0045] S1, preparing a graphite electrode;

[0046] S2, preparing a glassy carbon graphite electrode:

[0047] S21, coating 3mm of phenolic resin on the surface of the graphite electrode prepared in step S1 by immersion;

[0048] S22, curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature to obtain a graphite electrode coated with a glassy carbon precursor;

[0049] S23, placing the graphite electrode coated with a glassy carbon precursor obtained in step S22 in an argon-filled high-temperature furnace, and performing carbonization treatment at 1000°C under an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0050] S24, the glassy carbon graphite electrode primary product obtained in step S23 is heated to 3000 DEG C in an argon-filled high-temperature furnace for heat treatment for 1 h, and a high-purity glassy carbon graphite electrode is obtained. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5 mm.

[0051] The prepared glassy carbon graphite electrode is subjected to mechanical property testing and electrical breakdown testing, and the results are shown in Table 1.

[0052] Example 2

[0053] The preparation method of the glassy carbon graphite electrode is as follows:

[0054] S1, preparing a graphite electrode;

[0055] S2, preparing a glassy carbon graphite electrode:

[0056] S21, coating 2 mm of phenolic resin on the surface of the graphite electrode prepared in step S1 by immersion;

[0057] S22, curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature to obtain a graphite electrode coated with a glassy carbon precursor;

[0058] S23, placing the graphite electrode coated with a glassy carbon precursor obtained in step S22 in an argon-filled high-temperature furnace for carbonization treatment at 1000 DEG C in an oxygen-free environment, to obtain a glassy carbon graphite electrode primary product;

[0059] S24, continuing to heat the glassy carbon graphite electrode primary product obtained in step S23 to 2000 DEG C in an argon-filled high-temperature furnace for heat treatment for 2 h, and obtaining a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1 mm.

[0060] The prepared glassy carbon graphite electrode is subjected to mechanical property testing and electrical breakdown testing, and the results are shown in Table 1.

[0061] Example 3

[0062] The preparation method of the glassy carbon graphite electrode is as follows:

[0063] S1, preparing a graphite electrode;

[0064] S2, preparing a glassy carbon graphite electrode:

[0065] S21, coating 1 mm of phenolic resin on the surface of the graphite electrode prepared in step S1 by immersion;

[0066] S22, curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature to obtain a graphite electrode coated with a glassy carbon precursor;

[0067] S23, placing the graphite electrode with the glassy carbon precursor obtained in step S22 in an argon-filled high-temperature furnace, and performing carbonization treatment at a high temperature of 1000 DEG C in an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0068] S24, continuing to heat the glassy carbon graphite electrode primary product obtained in step S23 in the argon-filled high-temperature furnace to a high temperature of 2500 DEG C, and performing heat treatment for 1.5 h to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 0.5 mm.

[0069] The glassy carbon graphite electrode obtained is subjected to mechanical property testing and electrical breakdown testing, and the results are shown in Table 1.

[0070] Example 4

[0071] The method for preparing the glassy carbon graphite electrode includes the following specific process:

[0072] S1, preparing a graphite electrode:

[0073] S11, preparing a graphite electrode;

[0074] S12, uniformly mixing Hf:HfO2:NH4Cl powder materials in a molar ratio of Hf:HfO2:NH4Cl = 4:5:3, placing the mixture in a vapor deposition furnace, suspending the graphite electrode above the powder in the vapor deposition furnace, continuously introducing hydrogen into the vapor deposition furnace, maintaining the oxygen-free pressure in the furnace at 1.8 kPa, and slowly heating the vapor deposition furnace to 1500 DEG C to make the gas generated by the powder interact with the graphite electrode and generate an HfC coating layer on the surface of the graphite electrode,

[0075] The heating process of the vapor deposition furnace is as follows: heating at 400 DEG C for 40 min; heating at a temperature rising from 400 DEG C to 800 DEG C for 40 min; heating at 800 DEG C for 90 min; heating at a temperature rising from 900 DEG C to 1350 DEG C for 40 min; and heating at 1350 DEG C for 4.5 h.

[0076] S2, preparing a glassy carbon graphite electrode:

[0077] S21, coating the graphite electrode prepared in step S1 with a 3 mm phenolic resin by immersion;

[0078] S22, obtaining a graphite electrode with a glassy carbon precursor by curing the graphite electrode coated with the phenolic resin obtained in step S21 at room temperature;

[0079] S23, placing the graphite electrode with glassy carbon precursor obtained in step S22 in a high-temperature furnace filled with argon, and performing carbonization treatment at 1000 DEG C under an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0080] S24, continuing to heat the glassy carbon graphite electrode primary product obtained in step S23 in a high-temperature furnace filled with argon to 2000 DEG C, and performing heat treatment for 2 hours to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5 mm

[0081] The mechanical property test and electric breakdown test were performed on the prepared glassy carbon graphite electrode, and the results are shown in Table 1.

[0082] Example 5

[0083] The preparation method of the glassy carbon graphite electrode includes the following specific process:

[0084] S1, preparing a graphite electrode:

[0085] S11, preparing a graphite electrode;

[0086] S12, uniformly mixing Hf:HfO2:NH4Cl powder materials in a molar ratio of Hf:HfO2:NH4Cl = 4:5:3, placing the mixture in a vapor deposition furnace, suspending the graphite electrode above the powder in the vapor deposition furnace, continuously introducing hydrogen into the vapor deposition furnace, maintaining the oxygen-free pressure in the furnace at 1.8 kPa, slowly heating the vapor deposition furnace to 1500 DEG C, and allowing the gas generated by the powder to interact with the graphite electrode to form an HfC coating on the surface of the graphite electrode,

[0087] The heating process of the vapor deposition furnace is as follows: heating at 350 DEG C for 50 min; the temperature rising time from 350 DEG C to 900 DEG C is 40 min; heating at 900 DEG C for 70 min; the temperature rising time from 900 DEG C to 1200 DEG C is 40 min; and heating at 1200 DEG C for 5 h.

[0088] S2, preparing a glassy carbon graphite electrode:

[0089] S21, coating the graphite electrode prepared in step S1 with 3 mm of phenolic resin by immersion;

[0090] S22, obtaining a graphite electrode with glassy carbon precursor after curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature;

[0091] S23, placing the graphite electrode with glassy carbon precursor obtained in step S22 in a high-temperature furnace filled with argon, and performing carbonization treatment at 1000 DEG C under an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0092] S24, the glassy carbon graphite electrode primary product obtained in step S23 is heated to 2000 DEG C in an argon-filled high-temperature furnace for heat treatment for 2 hours, to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5 mm.

[0093] The prepared glassy carbon graphite electrode is subjected to mechanical property testing and electrical breakdown testing, and the results are shown in Table 1.

[0094] Example 6

[0095] The preparation method of the glassy carbon graphite electrode includes the following specific process:

[0096] S1, preparing a graphite electrode:

[0097] S11, preparing a graphite electrode;

[0098] S12, Hf:HfO2:NH4Cl powder materials are uniformly mixed in a molar ratio of Hf:HfO2:NH4Cl = 4:5:3, and then placed in a vapor deposition furnace. The graphite electrode is hung above the powder, and hydrogen gas is continuously introduced into the vapor deposition furnace to maintain an oxygen-free pressure of 1.8 kPa in the furnace. The vapor deposition furnace is slowly heated to 1500 DEG C, so that the gas generated by the powder interacts with the graphite electrode and generates an HfC coating on the surface of the graphite electrode,

[0099] The heating process of the vapor deposition furnace is as follows: 400 DEG C for 40 min; the temperature rising time from 400 DEG C to 1000 DEG C is 40 min; 1000 DEG C for 60 min; the temperature rising time from 1000 DEG C to 1500 DEG C is 40 min; and 1500 DEG C for 4 h.

[0100] S2, preparing a glassy carbon graphite electrode:

[0101] S21, a 3 mm phenolic resin is coated on the surface of the graphite electrode prepared in step S1 by immersion;

[0102] S22, the graphite electrode coated with phenolic resin obtained in step S21 is cured at room temperature to obtain a graphite electrode coated with a glassy carbon precursor;

[0103] S23, the graphite electrode coated with a glassy carbon precursor obtained in step S22 is placed in an argon-filled high-temperature furnace for carbonization treatment at 1000 DEG C in an oxygen-free environment, to obtain a glassy carbon graphite electrode primary product;

[0104] S24, the glassy carbon graphite electrode primary product obtained in step S23 is heated to 2000 DEG C in an argon-filled high-temperature furnace for heat treatment for 2 hours, to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5 mm.

[0105] The mechanical property test and electric breakdown test were performed on the prepared glassy carbon graphite electrode, and the results are shown in Table 1.

[0106] Comparative Example 1

[0107] Preparation of graphite electrode

[0108] 1. 30 parts of stone tar, 40 parts of needle coke, 25 parts of anthracite, and 5 parts of coal pitch were used as raw materials, and calcination was performed under air isolation conditions, with a calcination temperature of 1300°C.

[0109] 2. The calcined raw materials were crushed to obtain carbonaceous particle crushing products of different sizes, and the crushing products with particle sizes of 0.3-1.0 mm and 1.0-1.5 mm were mixed in a ratio of 1:3.

[0110] 3. The above mixture was dry mixed at 170°C for 30 minutes to obtain a paste.

[0111] 4. The paste was cooled to 110°C, and after 20 minutes of incubation, it was placed in an extruder for pre-pressing for 5 minutes at a pressure of 30 MPa. Then, the green product was pressed into a rod shape, and the pressed green product was calcined in a heating furnace under air isolation conditions to obtain a graphite electrode.

[0112] The mechanical property test and electric breakdown test were performed on the prepared glassy carbon graphite electrode, and the results are shown in Table 1.

[0113] Comparative Example 2

[0114] The preparation method of the glassy carbon graphite electrode is as follows:

[0115] S1, preparation of graphite electrode:

[0116] S11, preparation of graphite electrode;

[0117] S12, Hf, HfO2, and NH4Cl powder materials were uniformly mixed in a molar ratio of Hf:HfO2:NH4Cl = 4:5:3, and then placed in a gas deposition furnace with a temperature of 1500°C. The graphite electrode was suspended above the powder, and hydrogen gas was continuously introduced into the gas deposition furnace to maintain an oxygen-free pressure of 1.8 kPa in the furnace. The powder was heated for 7 hours to allow the gas generated by the powder to interact with the graphite electrode and form a HfC coating on the surface of the graphite electrode.

[0118] S2, preparation of glassy carbon graphite electrode:

[0119] S21, 3 mm of phenolic resin was coated on the surface of the graphite electrode prepared in step S1 by immersion;

[0120] S22, curing the phenolic resin coated graphite electrode obtained in step S21 at room temperature to obtain a glassy carbon precursor coated graphite electrode;

[0121] S23, placing the glassy carbon precursor coated graphite electrode obtained in step S22 in an argon filled high temperature furnace, and performing carbonization treatment at 1000 DEG C under an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0122] S24, continuing to heat the glassy carbon graphite electrode primary product obtained in step S23 in the argon filled high temperature furnace to 2000 DEG C, and performing heat treatment for 2 hours to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5 mm.

[0123] The mechanical property test and electric breakdown test were performed on the prepared glassy carbon graphite electrode, and the results are shown in Table 1.

[0124] Comparative Example 3

[0125] The preparation method of the glassy carbon graphite electrode includes the following specific process:

[0126] S1, preparing a graphite electrode:

[0127] S11, preparing a graphite electrode;

[0128] S12, uniformly mixing Hf, HfO2 and NH4Cl powder materials in a molar ratio of Hf:HfO2:NH4Cl = 4:5:3, placing the mixture in a gas deposition furnace, suspending the graphite electrode above the powder, continuously introducing hydrogen into the gas deposition furnace, maintaining the oxygen-free pressure in the furnace at 1.8 kPa, slowly heating the gas deposition furnace to 1500 DEG C, and allowing the gas generated by the powder to interact with the graphite electrode to form an HfC coating on the surface of the graphite electrode,

[0129] The heating process of the gas deposition furnace is: room temperature to 1500 DEG C for 80 min; 1500 DEG C for 5 h.

[0130] S2, preparing a glassy carbon graphite electrode:

[0131] S21, coating 3 mm of phenolic resin on the surface of the graphite electrode prepared in step S1 by immersion;

[0132] S22, curing the phenolic resin coated graphite electrode obtained in step S21 at room temperature to obtain a glassy carbon precursor coated graphite electrode;

[0133] S23, placing the glassy carbon precursor coated graphite electrode obtained in step S22 in an argon filled high temperature furnace, and performing carbonization treatment at 1000 DEG C under an oxygen-free environment to obtain a glassy carbon graphite electrode primary product;

[0134] S24, the glassy carbon graphite electrode primary product obtained in step S23 is heated to 3000℃ in an argon-filled high-temperature furnace for heat treatment for 1h, to obtain a high-purity glassy carbon graphite electrode. The glassy carbon coating layer of the high-purity glassy carbon graphite electrode has an average thickness of 1.5mm.

[0135] The prepared glassy carbon graphite electrode is subjected to mechanical property testing and electrical breakdown testing, and the results are shown in Table 1. The electrical breakdown testing observes the number of surface scratches and appearance of the electrode, and defines the surface scratches as the number of scratches with a diameter greater than 1mm per unit area.

[0136]

[0137]

[0138] Through comparison of Examples 1-3 and Examples 4-6, it can be seen that the formation of the HfC coating layer on the surface of the graphite electrode can improve the bonding force between the glassy carbon layer and the graphite electrode, and is conducive to improving the overall performance of the glassy electrode.

[0139] Through comparison of Example 4 and Comparative Examples 2-3, it can be considered that the step-by-step heating of Example 4, especially in the normal temperature-400℃ stage, the heating of the reactants can generate H2, which can reduce the amount of hydrogen used in the reaction process. In this stage, the reactants generate HCl, HfC, H2, etc., in the 800℃-1000℃ stage, HfC decomposes into Hf and HfCl4, and in the 1200℃-1500℃ stage, HfC is directly generated. In the process, Hf and HfCl4 gas reacts to generate HfCl3 gas, which reacts with C on the surface layer of the graphite electrode under the action of hydrogen to generate HfC and HCl gas, and HfC directly penetrates the surface layer of the graphite electrode. The present application adopts step-by-step slow heating, which is conducive to promoting the generation of direct reactants for preparing HfC.

[0140] The heating method of Comparative Examples 2-3 will cause insufficient production of part of the intermediate products, which will eventually result in a relatively thin HfC layer.

[0141] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method of producing a glassy carbon graphite electrode, characterized by, Comprising: S1, preparing a graphite electrode; S2, preparing a glassy carbon graphite electrode: The step S2 specifically comprises: S21, coating phenolic resin on the surface of the graphite electrode prepared in step S1; S22, obtaining a glassy carbon precursor coated graphite electrode after curing the graphite electrode coated with phenolic resin obtained in step S21 at room temperature; S23, obtaining a glassy carbon graphite electrode primary product by carbonizing the glassy carbon precursor coated graphite electrode obtained in step S22 at 1000 DEG C high temperature in an oxygen-free environment; S24, obtaining a high-purity glassy carbon graphite electrode after heat treatment of the glassy carbon graphite electrode primary product obtained in step S23 at 2000 DEG C~3000 DEG C high temperature; The step S1 prepares a graphite electrode, and a HfC coating layer is prepared on the surface of the graphite electrode, and the specific method is: S11, preparing a graphite electrode; S12, uniformly mixing Hf:HfO2: NH4Cl powder materials in a molar ratio of Hf:HfO2: NH4Cl of 4:5:3, placing them in a vapor deposition furnace, suspending the graphite electrode above the powder, continuously introducing hydrogen into the vapor deposition furnace, maintaining the oxygen-free pressure in the furnace at 1.8kPa, slowly heating the vapor deposition furnace to 1500 DEG C, and making the gas generated by the powder interact with the graphite electrode and generate a HfC coating layer on the surface of the graphite electrode.

2. The method of producing a glassy carbon graphite electrode according to claim 1, wherein In the step S21, the thickness of the phenolic resin coated on the surface of the graphite electrode is 1~3mm.

3. The method of producing a glassy carbon graphite electrode according to claim 1, wherein In the step S24, the glassy carbon graphite electrode primary product obtained in step S23 is heat treated at 2000~3000 DEG C high temperature for 1~2h.

4. The method of making a glassy carbon graphite electrode according to claim 1, wherein The slow heating process of the vapor deposition furnace is 400 DEG C for 40min; 800 DEG C~1000 DEG C for 60min~90min, 1200 DEG C~1500 DEG C for 4h~5h, the temperature rising time of 400 DEG C~800 DEG C is 40min, and the temperature rising time of 1000 DEG C~1200 DEG C is 40min.

5. A glassy carbon graphite electrode, characterized by, Comprising: A graphite electrode, a HfC coating layer on the outer surface of the graphite electrode, and a glassy carbon layer coated outside the HfC coating layer.

6. The glassy carbon graphite electrode of claim 5, wherein The thickness of the glassy carbon layer is 0.5mm~2mm.

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