Single crystal furnace carbon-carbon energy-saving electrode and preparation method thereof

Abstract

This invention discloses a method for preparing a carbon-carbon energy-saving electrode for a single-crystal furnace, belonging to the technical field of composite material preparation. The method includes the following steps: preparing an electrode preform using a layup needle-punching method; spraying resin onto the electrode preform using a high-pressure atomization spraying method, impregnating it with resin and then curing it; depositing carbon on the electrode preform using a heating element-type vapor deposition method to densify it and form a carbon-carbon composite material; placing the carbon-carbon composite material in an iron box, filling the inside of the iron box with asphalt, placing asphalt and resin 0.5-1m above the carbon / carbon composite material, evacuating and sealing the box, placing it in an impregnation tank for high-pressure impregnation, and then placing it in a carbonization furnace; then performing high-temperature heat treatment on the carbon / carbon composite material, and finally machining to obtain the carbon-carbon energy-saving electrode. The prepared carbon-carbon electrode has low resistivity and thermal conductivity, which helps reduce furnace heating costs, thus possessing advantages such as energy saving, high temperature resistance, and high strength.

Description

Technical Field

[0001] This invention belongs to the technical field of composite material preparation, specifically a single-crystal furnace carbon-carbon energy-saving electrode and its preparation method. Background Technology

[0002] A single crystal furnace is a device used to produce high-purity silicon or other metal alloys. Its principle involves using electrodes to generate a high-temperature, high-pressure electric arc within the furnace. This arc heats, dissolves, and crystallizes the raw material, resulting in single-crystal materials. The electrodes of a single crystal furnace are a crucial factor affecting its efficiency and quality, as their performance directly determines the stability of the electric arc, heating costs, and heat loss.

[0003] Currently, commonly used electrode materials for single crystal furnaces include graphite, metals, and carbon / carbon composites. Among them, graphite electrodes were the earliest used electrode material. Their preparation method is relatively simple, mainly involving mixing natural clay and tar through extrusion and calcination processes, followed by mechanical processing into cylindrical electrode blanks. However, graphite electrodes also have some drawbacks, such as high resistivity, high thermal conductivity, low strength, and poor high-temperature resistance. These drawbacks lead to higher energy consumption and heat loss in single crystal furnaces, and the electrodes are prone to deformation, breakage, and corrosion.

[0004] To overcome the shortcomings of graphite electrodes, some single-crystal furnaces have adopted metal electrodes, such as tungsten and molybdenum. The fabrication methods for metal electrodes mainly involve casting and machining to form cylindrical electrode blanks. Compared to graphite electrodes, metal electrodes have lower resistivity and thermal conductivity, thus reducing the heating cost and heat loss of the single-crystal furnace. However, metal electrodes also have some drawbacks, such as lower strength and poor high-temperature resistance. These shortcomings make them prone to deformation, fracture, and corrosion within the single-crystal furnace.

[0005] To further improve the efficiency and quality of single crystal furnaces, some furnaces have adopted carbon / carbon composite materials as electrode materials. Carbon / carbon composite materials are composite materials composed of carbon fibers and a carbon matrix, which have advantages such as low density, high strength, good high temperature resistance, and corrosion resistance.

[0006] Carbon / carbon composites offer significant technological and economic advantages over graphite and metal electrodes; however, their preparation methods also present challenges, such as complex processes, high costs, and inconsistent quality. Therefore, improving the preparation methods of carbon / carbon composites to enhance their quality and performance while reducing costs and energy consumption is a crucial issue in the field of single-crystal furnace electrodes.

[0007] The purpose of this invention is to address the above-mentioned problems by providing a single-crystal furnace carbon / carbon energy-saving electrode and its preparation method. This method employs multiple processes to form a uniform, dense, and tough carbon / carbon composite material from carbon fiber felt, which has low resistivity and thermal conductivity. This provides an energy-saving, high-temperature resistant, and high-strength single-crystal furnace carbon / carbon electrode and its preparation method. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention aims to provide a carbon-carbon energy-saving electrode for a single-crystal furnace and its preparation method. The prepared carbon-carbon electrode has low resistivity and thermal conductivity, which helps to reduce the heating cost of the furnace, thus having the advantages of energy saving, high temperature resistance, and high strength.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a carbon-carbon energy-saving electrode for a single-crystal furnace, the method comprising the following steps:

[0011] (a) Electrode blanks are prepared by layer-laying needle punching method, with the electrode axis parallel to the needle punching direction of the blank;

[0012] (b) The resin is sprayed onto the electrode blank using a high-pressure atomization spraying method, so that it is impregnated with resin and cured.

[0013] (c) Carbon is deposited on the electrode preform using a heating element vapor deposition method to densify it and form a carbon / carbon composite material;

[0014] (d) Place the carbon / carbon composite material in an iron box, put asphalt inside the iron box, put asphalt and resin 0.5-1m above the carbon / carbon composite material, vacuum and seal the box, put it in an impregnation tank, perform high-pressure impregnation, and then put it in a carbonization furnace.

[0015] (e) After multiple impregnation and carbonization processes, the density is reduced to 1.6-1.8 g / cm³. 3 Then, the carbon / carbon composite material is subjected to high-temperature heat treatment, and finally, carbon-carbon energy-saving electrode is obtained by machining.

[0016] Electrode blanks with uniform density and porosity are prepared by layer-by-layer needle punching, and the needle punching structure along the axial direction is made to improve their strength and stability. This structure can reduce the Z-direction thermal conductivity.

[0017] Resin is sprayed onto the electrode blank using a high-pressure atomization spraying method, and then impregnated with resin and cured, thereby increasing its density and strength and protecting its internal structure from damage.

[0018] Carbon is deposited on the electrode blank by heating element vapor deposition, which densifies the blank and forms a carbon / carbon composite material, thereby increasing its carbon content and degree of carbonization and forming a three-dimensional network structure.

[0019] Carbon / carbon composite materials are repeatedly impregnated and carbonized in an iron box using a high-pressure impregnation method, which further densifies and increases their strength, thereby improving their high-temperature resistance and corrosion resistance.

[0020] Carbon / carbon composite materials are subjected to high-temperature heat treatment to achieve lower resistivity and thermal conductivity, thereby reducing their heat generation costs and heat loss.

[0021] The carbon / carbon composite material is machined into a cylindrical electrode blank and connected to a copper electrode and a heating element to form a carbon / carbon energy-saving electrode for a single crystal furnace, thereby improving the efficiency and quality of the single crystal furnace.

[0022] In step (a), the electrode blank itself is cylindrical with a density of 0.35-0.55 g / cm³. 3 Under optimal implementation conditions, this technical solution ensures suitable strength and permeability.

[0023] In step (b), the resin is sprayed using an upward-spraying, downward-spiraling airflow method, with a spraying time of 10-30 minutes, and the electrode blank density is 0.6-0.9 g / cm³. 3 In a preferred embodiment, this technical solution employs an upward-spraying, downward-spiraling airflow method, which allows the resin to be evenly distributed on the surface and inside of the electrode blank in the form of tiny droplets, thereby increasing its density and strength and protecting its internal structure from damage.

[0024] In step (c), the temperature is 1000-1500℃, the time is 10-200h, and the density of the carbon / carbon composite material is 0.7-1.2g / cm³. 3 .

[0025] In step (d), the impregnation pressure is 0.2-100 MPa. In a preferred embodiment, this technical solution allows the impregnation liquid to fully penetrate the interior of the carbon / carbon composite material and to carry out rapid carbonization under high pressure.

[0026] In step (e), the high temperature is 2200-2800℃. In a preferred embodiment, this technical solution employs a high-temperature heat treatment method to heat-treat the carbon / carbon composite material at a certain temperature, causing changes in its internal structure, such as increased grain size, reduced grain boundaries, and elimination of defects, thereby lowering its resistivity and thermal conductivity. This reduces the energy consumption and heat loss of the single-crystal furnace.

[0027] The resin is selected from one of furfuryl ketone resin and epoxy resin. In a preferred embodiment, this technical solution selects one of phenolic resin, furfuryl ketone resin, and epoxy resin as the resin material because these resins have high carbon content, low oxygen content, good high temperature resistance and pyrolysis performance, and can form chemical or physical bonds with the green body, thereby improving the resin impregnation and carbonization effects.

[0028] A carbon-carbon energy-saving electrode for a single-crystal furnace is disclosed, prepared by the aforementioned method. This electrode solves the technical problems of high thermal conductivity, high resistance, and high heating cost of traditional graphite electrodes, providing an energy-saving, high-temperature resistant, and high-strength carbon / carbon electrode for single-crystal furnaces. The electrode works by connecting to a copper electrode and a heating element, serving as the electrode of the single-crystal furnace, transmitting current and generating heat to heat the raw materials inside the furnace, causing them to melt and crystallize into single crystals. Because the carbon / carbon electrode has low resistivity and thermal conductivity, it can reduce energy consumption and heat loss.

[0029] An application of a carbon-carbon energy-saving electrode for a single-crystal furnace is disclosed, which is connected to a copper electrode and a heating element as the electrode of the single-crystal furnace. In a preferred embodiment, this technical solution forms a complete heating system by using the carbon-carbon energy-saving electrode as the electrode of the single-crystal furnace and connecting it to the copper electrode and the heating element, thereby performing processes such as heating, dissolving, and crystallizing the raw materials within the single-crystal furnace. Because the carbon / carbon energy-saving electrode has low resistivity and thermal conductivity, it can reduce the power consumption and heat loss of the single-crystal furnace.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The carbon / carbon electrode prepared by the present invention can save 3-5 kWh of electricity, reduce the operating cost of the single crystal furnace, and thus improve the economic benefits of the single crystal furnace;

[0032] (2) The carbon / carbon electrode prepared by the present invention can improve the efficiency and quality of the single crystal furnace because the carbon / carbon electrode has low resistivity and thermal conductivity, thereby reducing the power consumption and heat loss of the single crystal furnace, so that the raw materials in the single crystal furnace can be heated, dissolved and crystallized uniformly, and high-quality single crystal materials can be produced.

[0033] (3) Using carbon / carbon electrodes can improve the stability and safety of the single crystal furnace because carbon / carbon electrodes have high strength and high temperature resistance, thus they can withstand the high temperature and high pressure environment inside the single crystal furnace and are not prone to deformation, breakage, corrosion, etc., ensuring the normal operation of the single crystal furnace.

[0034] (4) Using carbon / carbon electrodes can improve the environmental friendliness of single crystal furnaces because carbon / carbon electrodes are made from renewable resources and do not produce harmful substances or waste gas during use, thereby reducing pollution to the environment. Attached Figure Description

[0035] Figure 1 This is a process flow diagram for Example 1. Detailed Implementation

[0036] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Example 1:

[0038] A single-crystal furnace carbon-carbon energy-saving electrode and its preparation method, the method comprising the following steps:

[0039] (a) An electrode preform is prepared using a layer-by-layer needle punching method, with the electrode axis parallel to the needle punching direction of the preform. First, carbon fiber cloth is laid on a needle punching machine according to a certain number of layers and direction. Then, the machine is needle punched to create a hook-and-loop structure between the carbon fiber cloths, resulting in a needle punched structure along the axial direction of the preform. In this embodiment, the carbon fiber cloth used is type T300, with 8 pieces laid per layer, each piece measuring 1m × 1m, and laid in a 0° / 90° intersecting direction. The parameters of the needle punching machine are: 100 needle punches / cm. 2 The needle penetration depth was 10 mm, and the penetration angle was 30°. After needle penetration, an electrode embryo was obtained with a density of 0.5 g / cm³. 3 The porosity is 80%.

[0040] (b) Resin is sprayed onto the electrode blank using a high-pressure atomization spraying method to impregnate and cure it. First, epoxy resin is pressurized and delivered to the spray gun using a high-pressure plunger pump. Then, a nozzle is installed on both the upper and lower surfaces of the electrode blank, aligned with the center line of the electrode blank. Next, the sprayer is turned on, and the resin is sprayed onto the electrode blank in the form of tiny droplets using high-pressure atomization. In this embodiment, the spraying method is an upward spraying and downward spiral airflow, that is, the upper nozzle sprays perpendicular to the surface of the electrode blank, and the lower nozzle sprays in a spiral motion along the surface of the electrode blank. The spraying time is 20 minutes, and the spraying pressure is 10 MPa. After spraying, the electrode blank is placed in an oven and heated to 200°C to cure it. After curing, a resin-impregnated electrode blank with a density of 0.8 g / cm³ is obtained. 3 ;

[0041] (c) Carbon is deposited on an electrode preform using a heating element-type vapor deposition method to densify it and form a carbon / carbon composite material. First, a resin-impregnated electrode preform is used as the heating element and connected to form a three-phase linear heating element structure. Then, the heating element structure is installed in a vapor deposition reactor, and a vacuum is applied to 0.01 MPa. Next, a carbon-containing gas, such as methane or acetylene, is introduced, and electricity is applied to heat the heating element structure. In this embodiment, methane is used as the carbon-containing gas, with a flow rate of 0.5 L / min. The temperature of the heating element structure is 1200 °C, and the time is 50 h. During the heating process, methane is cracked in the gas phase, and the cracking products are deposited on the electrode preform to form a carbon / carbon composite material. After deposition, a carbon / carbon composite material with a density of 1.0 g / cm³ is obtained. 3 ;

[0042] (d) The carbon / carbon composite material is placed in an iron box, with asphalt inside. Asphalt and resin are placed 0.5m above the carbon / carbon composite material to increase the pressure of the impregnation solution. Next, the box is vacuum-sealed and placed in an impregnation tank for high-pressure impregnation. After impregnation, it is placed in a carbonization furnace. In this embodiment, the impregnation pressure is 50 MPa. After impregnation, the box is removed and placed in a carbonization furnace for carbonization at a certain temperature. In this embodiment, the carbonization temperature is 1500℃ and the time is 100 hours. After multiple impregnation and carbonization cycles, a density of 1.7 g / cm³ is obtained. 3 Carbon / carbon composite materials;

[0043] (e) A high-temperature heat treatment method was used to treat the carbon / carbon composite material, followed by machining to obtain a carbon / carbon energy-saving electrode. First, the carbon / carbon composite material was placed in a high-temperature furnace and heat-treated at a certain temperature to change its internal structure, such as increasing grain size, reducing grain boundaries, and eliminating defects, thereby reducing its resistivity and thermal conductivity. In this embodiment, the high-temperature treatment temperature was 2500℃, and the treatment time was 10 hours. Then, the carbon / carbon composite material was machined into a cylindrical electrode blank and connected to a copper electrode and a heating element to form a single-crystal furnace carbon / carbon energy-saving electrode. After high-temperature treatment, a density of 1.8 g / cm³ was obtained. 3 A carbon / carbon energy-saving electrode with a resistivity of 8 Ω·m, an XY thermal conductivity of 102 W / (m·K), a Z-direction thermal conductivity of 20 (W / (m·K)), a strength of 200 MPa, and a high temperature resistance of 2800℃.

[0044] Example 2:

[0045] The specific steps in this embodiment are the same as in Embodiment 1, except for some parameters. For example, in step (b), the spraying time is 10 minutes and the electrode blank density is 0.6 g / cm³. 3 In step (c), the heating temperature is 1000℃, the time is 200h, and the density is 1.2g / cm³. 3 In step (d), the impregnation pressure is 100 MPa, resulting in a density of 1.6 g / cm³. 3 The carbon / carbon composite material was prepared at a high temperature of 2800℃ in step (e). After preparation, a density of 1.8 g / cm³ was obtained. 3 A carbon / carbon energy-saving electrode with a resistivity of 7.5 Ω·m, an XY thermal conductivity of 95 W / (m·K), a Z thermal conductivity of 18 (W / (m·K)), a strength of 210 MPa, and a high temperature resistance of 2900℃.

[0046] Example 3:

[0047] The specific steps in this embodiment are the same as in Embodiment 1, except for some parameters. For example, in step (b), the spraying time is 30 minutes and the electrode blank density is 0.9 g / cm³. 3 In step (c), the heating temperature is 1500℃, the time is 100h, and the density is 1.1g / cm³. 3 In step (d), the impregnation pressure is 10 MPa, resulting in a density of 1.8 g / cm³. 3 The carbon / carbon composite material was prepared at a high temperature of 2200℃ in step (e). After preparation, a density of 1.9 g / cm³ was obtained. 3 A carbon / carbon energy-saving electrode with a resistivity of 8.5 Ω·m, an XY thermal conductivity of 105 W / (m·K), a Z-direction thermal conductivity of 23 (W / (m·K)), a strength of 230 MPa, and a high temperature resistance of 3100℃.

[0048] Comparative Example 1:

[0049] The traditional method for preparing single-crystal furnace graphite electrodes involves the following steps:

[0050] (a) Electrode preforms were prepared by extrusion. First, natural clay and tar were mixed evenly, and water was added to adjust the viscosity. Then, the mixture was extruded on an extruder to obtain cylindrical electrode preforms.

[0051] (b) The electrode blanks were calcined. First, the electrode blanks were installed in a calcining kiln, and a vacuum of 0.01 MPa was applied. Then, calcination was carried out at a certain temperature, causing a chemical reaction between the natural clay and tar to form a graphite structure. In this comparative example, the calcination temperature was 1000℃, and the time was 10 hours. After calcination, a density of 1.5 g / cm³ was obtained. 3 Graphite electrode blank;

[0052] (c) The graphite electrode blank is machined into a cylindrical electrode blank and connected to a copper electrode and a heating element to form a single crystal furnace graphite electrode.

[0053] By comparing Embodiment 1 of the present invention with Comparative Example 1, the following conclusions can be drawn:

[0054] Example 1 of the present invention uses a carbon / carbon energy-saving electrode with a resistivity of 8 Ω·m, an XY thermal conductivity of 102 W / (m·K), and a Z-axis thermal conductivity of 20 (W / (m·K)); Comparative Example 1 uses a graphite electrode with a resistivity of 5.4 x 10⁻⁶. 2 The resistivity and thermal conductivity are 152 W / (m·K) in the XY direction and 59 W / (m·K) in the Z direction. Therefore, Embodiment 1 of the present invention has low resistivity and thermal conductivity, thereby reducing the power consumption and heat loss of the single crystal furnace.

[0055] Example 1 of the present invention uses a carbon / carbon energy-saving electrode with a strength of 200 MPa and a high temperature resistance of 2800℃; Comparative Example 1 uses a graphite electrode with a strength of 100 MPa and a high temperature resistance of 2000℃. Therefore, Example 1 of the present invention has high strength and high temperature resistance, thus it can withstand the high temperature and high pressure environment inside a single crystal furnace and is not prone to deformation, breakage, corrosion, etc.

[0056] In summary, Embodiment 1 of the present invention has significant technical advantages and economic benefits compared to Comparative Example 1.

[0057] Comparative Example 2:

[0058] The traditional method for preparing single-crystal furnace metal electrodes involves the following steps:

[0059] (a) Electrode blanks are prepared by casting. First, a metallic material, such as tungsten or molybdenum, is heated to a molten state and poured into a mold. Then, it is cooled at a certain temperature to solidify the metallic material and obtain a cylindrical electrode blank.

[0060] (b) The metal electrode blank is machined into a cylindrical electrode blank and connected to the copper electrode and the heating element to form a single crystal furnace metal electrode.

[0061] By comparing Embodiment 1 and Comparative Example 2 of the present invention, the following conclusions can be drawn:

[0062] Example 1 of the present invention uses a carbon / carbon energy-saving electrode with a resistivity of 8 Ω·m, an XY thermal conductivity of 102 W / (m·K), and a Z-axis thermal conductivity of 20 (W / (m·K)); Comparative Example 2 uses a metal electrode with a resistivity of 1.3 x 10⁻⁶. 2The resistivity and thermal conductivity in the XY direction are 114 W / (m·K), and the thermal conductivity in the Z direction is 35 (W / (m·K)). Therefore, Example 1 of the present invention has lower resistivity and thermal conductivity, thereby reducing the power consumption and heat loss of the single crystal furnace; Comparative Example 2 has higher resistivity and thermal conductivity, resulting in greater power consumption and heat loss of the single crystal furnace.

[0063] Example 1 of this invention uses a carbon / carbon energy-saving electrode with a strength of 200 MPa and a high-temperature resistance of 2800℃; Comparative Example 2 uses a metal electrode with a strength of 50 MPa and a high-temperature resistance of 1500℃. It is evident that Example 1 of this invention possesses higher strength and high-temperature resistance, thus able to withstand the high-temperature and high-pressure environment within a single crystal furnace, and is less prone to deformation, breakage, corrosion, etc.; Comparative Example 2 has lower strength and high-temperature resistance, thus easily experiencing deformation, breakage, corrosion, etc., within the single crystal furnace.

[0064] In summary, Embodiment 1 of the present invention has significant technical advantages and economic benefits compared to Comparative Example 2.

[0065] The electrode performance obtained from the above embodiments and comparative examples is presented in tabular form as follows.

[0066] Table 1

[0067]

[0068] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-carbon energy-saving electrode in a single-crystal furnace, characterized in that, The method includes the following steps: (a) Electrode blanks were prepared using a layer-layout needle punching method, with the electrode axis parallel to the needle punching direction of the blank. The layup direction was a 0° / 90° intersection. The parameters of the needle punching machine were: 100 needle punches / cm. 2 The needle insertion depth is 10mm and the needle insertion angle is 30°. (b) Resin is sprayed onto the electrode blank using a high-pressure atomization spraying method, impregnating it with resin and then curing it. The resin spraying adopts an upward spraying and downward spiral airflow pattern, with a spraying time of 10-30 minutes. The density of the electrode blank is 0.6-0.9 g / cm³. 3 ; (c) Carbon is deposited on the electrode blank using a heating element vapor deposition method to densify it and form a carbon / carbon composite material; (d) Place the carbon / carbon composite material in an iron box, put asphalt inside the iron box, put asphalt and resin 0.5-1m above the carbon / carbon composite material, vacuum and seal the box, put it in an impregnation tank, perform high-pressure impregnation, and then put it in a carbonization furnace. (e) After multiple impregnation and carbonization processes, the density is reduced to 1.6-1.8 g / cm³. 3 Then, the carbon / carbon composite material is subjected to high-temperature heat treatment, and finally, carbon-carbon energy-saving electrode is obtained by machining.

2. The method for preparing a single-crystal furnace carbon-carbon energy-saving electrode according to claim 1, characterized in that, In step (a), the electrode blank itself is cylindrical with a density of 0.35-0.55 g / cm³. 3 .

3. The method for preparing a single-crystal furnace carbon-carbon energy-saving electrode according to claim 1, characterized in that, In step (c), the temperature is 1000-1500℃, the time is 10-200h, and the density of the carbon / carbon composite material is 0.7-1.2g / cm³. 3 .

4. The method for preparing a single-crystal furnace carbon-carbon energy-saving electrode according to claim 1, characterized in that, The impregnation pressure in step (d) is 0.2-100 MPa.

5. The method for preparing a single-crystal furnace carbon-carbon energy-saving electrode according to claim 1, characterized in that, The high temperature in step (e) is 2200-2800℃.

6. The method for preparing a single-crystal furnace carbon-carbon energy-saving electrode according to claim 1, characterized in that, The resin is selected from either furfuryl ketone resin or epoxy resin.

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