Graphite electrode protection material and preparation method and application thereof

Abstract

The invention provides a graphite electrode protection material and a preparation method and application thereof, and relates to the technical field of graphite electrodes. Specifically, the protective material comprises the following components in parts by mass: 25-50 parts of silicon carbide, 15-25 parts of aluminum oxide, 5-10 parts of yttrium oxide, 15-25 parts of boron carbide, 10-20 parts of titanium dioxide, 10-20 parts of zirconium oxide and 5-10 parts of cerium oxide. Meanwhile, the invention also provides a method for preparing the protective layer containing the protective material on the surface of the graphite electrode. According to the integrated graphite electrode and the protective layer thereof provided by the invention, the oxidation resistance, the high temperature resistance and the bonding strength with the graphite electrode of the electrode are synchronously improved through the design of the protective material, the stability of the internal structure of the protective layer is enhanced, and the service life of the graphite electrode is effectively prolonged; good application prospects are realized in the photovoltaic field.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite electrodes, and in particular to a graphite electrode protective material and a preparation method and application thereof. Background Art

[0002] Graphite electrodes are a high-temperature resistant graphite conductive material made from petroleum coke and pitch coke as aggregates and coal tar as a binder. The materials are calcined, crushed, ground, batched, kneaded, formed, roasted, impregnated, graphitized, and then machined. Graphite electrodes are categorized into standard power, high power, and ultra-high power grades based on their quality indicators. Graphite electrodes possess excellent electrical conductivity, thermal stability, and chemical stability, allowing them to withstand high temperatures and arc shock. They are widely used in high-temperature industrial applications such as steelmaking, yellow phosphorus smelting, and industrial silicon smelting. Graphite electrodes are also indispensable in high-temperature industries such as photovoltaics and graphite products. In the photovoltaic industry, graphite electrodes are primarily used in the manufacture of solar photovoltaic panels. Their excellent electrical conductivity and stability ensure stable current transmission within panels, thereby improving panel efficiency. They also maintain stable performance in a variety of harsh environments, providing reliable support for photovoltaic equipment and significantly improving its efficiency and stability.

[0003] Although graphite electrodes already have good chemical properties, in actual industrial scenarios, a protective layer is still prepared on the surface of the graphite electrode to further improve its high-temperature oxidation resistance or stability, thereby preventing the graphite electrode from being corroded when operating in a high-temperature environment for a long time, affecting its service life and production costs. Currently, the protective materials used to prepare graphite electrode protective layers have defects in high-temperature stability, oxidation resistance, and bonding strength with the electrode, making it difficult to meet actual production needs. Therefore, the development of high-performance protective materials is imminent.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a graphite electrode protection material that simultaneously meets the high-level performance requirements of the graphite electrode protection layer in terms of high-temperature stability, oxidation resistance and bonding strength with the electrode.

[0006] The second purpose of the present invention is to provide a graphite electrode protective layer that can prevent oxidation corrosion during long-term high-temperature operation, prevent or significantly delay the decomposition or deterioration of the graphite electrode, extend the service life of the graphite electrode, and at the same time have good compatibility and bonding with the surface of the graphite electrode.

[0007] The third object of the present invention is to provide a method for preparing a graphite electrode protective layer, which has a simple and convenient process, low cost, and can meet the needs of mass production.

[0008] The fourth object of the present invention is to provide an application of the graphite electrode protection layer in photovoltaics.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0010] A graphite electrode protective material comprising the following components in parts by mass:

[0011] 25-50 parts of silicon carbide, 15-25 parts of aluminum oxide, 5-10 parts of yttrium oxide, 15-25 parts of boron carbide, 10-20 parts of titanium dioxide, 10-20 parts of zirconium oxide and 5-10 parts of cerium oxide.

[0012] A graphite electrode protective layer comprises the graphite electrode protective material.

[0013] A method for preparing the graphite electrode protective layer comprises the following steps:

[0014] Wet-mixing and grinding silicon carbide, aluminum oxide, yttrium oxide, boron carbide, titanium dioxide, zirconium oxide, and cerium oxide to obtain a first mixed material;

[0015] Fully mixing the first mixed material, binder, silica sol and silane coupling agent to obtain a second mixed material;

[0016] The second mixture is coated on the surface of the graphite electrode, and then subjected to heat treatment to obtain a protective layer supported on the graphite electrode.

[0017] And the use of the graphite electrode protection layer in photovoltaics.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention achieves a comprehensive improvement in antioxidant performance, high-temperature resistance, and bonding strength with the graphite electrode by mixing various inorganic raw materials as protective materials for the graphite electrode protective layer, thereby more effectively blocking oxygen, reducing the oxidation rate, and extending the service life of the graphite electrode. In addition, compared to the existing layered preparation method, the protective layer preparation process of the present invention combines the raw materials for integrated preparation, reducing the number of steps, improving production efficiency, and reducing production costs. At the same time, the integrated preparation method of the present invention makes the internal structure of the material more compact, and the synergistic effect between the various components is better, making the graphite electrode more stable in high-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 Provided is a structural schematic diagram of a graphite electrode and its protective layer in the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments, but those skilled in the art will understand that the embodiments described below are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially. In addition, the terms "first", "second" and "third" are only used for descriptive purposes and are not to be understood as indicating or implying relative importance.

[0023] A first aspect of the present invention is to provide a graphite electrode protection material.

[0024] The graphite electrode protection material comprises the following components by mass: 25-50 parts of silicon carbide, 15-25 parts of aluminum oxide, 5-10 parts of yttrium oxide, 15-25 parts of boron carbide, 10-20 parts of titanium dioxide, 10-20 parts of zirconium oxide and 5-10 parts of cerium oxide.

[0025] As an optional embodiment, the mass fractions of the components of the graphite electrode protection material include but are not limited to: silicon carbide 25, 26, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50; aluminum oxide 15, 18, 20, 22, 25; yttrium oxide 5, 6, 8, 10; boron carbide 15, 18, 20, 22, 25; titanium dioxide 10, 12, 15, 18, 20; zirconium oxide 10, 12, 15, 18, 20; cerium oxide 5, 6, 8, 10; it is worth noting that the mass fraction of each component can adopt any point value listed above, or can adopt the numerical range formed by any two point values.

[0026] As a preferred embodiment, the graphite electrode protection material includes the following components by mass percentage: 25% to 50% silicon carbide, 15% to 25% aluminum oxide, 5% to 10% yttrium oxide, 15% to 25% boron carbide, 10% to 20% titanium dioxide, 10% to 20% zirconium oxide and 5% to 10% cerium oxide.

[0027] In this invention, by compounding a variety of different types of inorganic solid particles as the primary protective material for the protective layer, the graphite electrode protective material, through multi-component collaborative design and innovative preparation processes, creates a high-performance protective layer that is resistant to high-temperature oxidation, slag erosion, and exhibits excellent thermomechanical compatibility. Silicon carbide and boron carbide form a high-hardness three-dimensional framework, which, combined with the phase transformation toughening of zirconium oxide and the grain boundary modification and oxygen buffering effect of rare earth oxides, significantly improves the coating's hardness and fracture toughness. Wet grinding achieves nanoscale particle dispersion and enhances interfacial activity with a silane coupling agent. The silica sol and binder form a nano-SiO glass phase and chemically bonded interface, which, after heat treatment, forms a closed-cell structure with a density of ≥95%, effectively blocking oxygen and slag penetration.

[0028] The protective coating of this invention achieves a weight gain of ≤1.5% after oxidation at 600°C for 50 hours, an erosion depth of ≤50 μm / 100 hours in cryolite slag at 950°C, and a thermal expansion coefficient matching error of ≤15% with the graphite substrate, achieving both high thermal conductivity and thermal shock resistance. By leveraging a multi-scale approach to composition, structure, and performance, this invention addresses the challenges of high-temperature oxidation, mechanical wear, and thermal shock failure associated with traditional graphite electrodes. This coating offers significant advantages in long-life protection and engineering applications in fields such as metallurgical arc furnaces and lithium battery anodes.

[0029] In the present invention, there are the following restrictions on the particle size of various inorganic components; it is worth noting that the general use of micron-sized or nano-sized solid particles in the present invention helps to obtain a dense and uniform protective layer on the surface of the graphite electrode, and at the same time can effectively improve the dispersibility of the protective material in the subsequent preparation process, thereby forming a uniform and highly adhesive protective layer.

[0030] As a preferred embodiment, the particle size of the silicon carbide (SiC) is 5 μm to 10 μm.

[0031] As a preferred embodiment, the particle size of the aluminum oxide (Al2O3) is 3 μm to 5 μm.

[0032] As a preferred embodiment, the particle size of the yttrium oxide (Y2O3) is 1 μm to 3 μm.

[0033] As a preferred embodiment, the particle size of the boron carbide (B4C) is 2 μm to 4 μm.

[0034] As a preferred embodiment, the particle size of the titanium dioxide (TiO2) is 50nm to 100nm.

[0035] As a preferred embodiment, the particle size of the zirconium oxide (ZrO2) is 30nm to 80nm.

[0036] A second aspect of the present invention provides a graphite electrode protective layer comprising the graphite electrode protective material described in the first aspect. It is understood that the present invention does not impose any strict restrictions on the composition of the graphite electrode protective layer; in addition to comprising the graphite electrode protective material, the graphite electrode protective layer may also comprise other binding components, pigments, or functional components. Any graphite electrode protective layer comprising the graphite electrode protective material constitutes an embodiment of the present invention.

[0037] The third aspect of the present invention is to provide a method for preparing the graphite electrode protective layer as described in the second aspect, which mainly includes the following steps: grinding, preparing slurry, coating and heat treatment.

[0038] (1) Silicon carbide, aluminum oxide, yttrium oxide, boron carbide, titanium dioxide, zirconium oxide and cerium oxide are wet-mixed and ground to obtain a first mixed material.

[0039] As a preferred embodiment, the wet mixed grinding adopts ball milling, and the ball milling time is 8 hours to 10 hours.

[0040] As a preferred embodiment, the dispersant for wet mixing and grinding includes at least one of ethanol, methanol, propanol and polyethylene glycol.

[0041] (2) The first mixed material, the binder, the silica sol and the silane coupling agent are fully mixed to obtain a second mixed material.

[0042] As a preferred embodiment, the binder comprises phenolic resin, sodium carboxymethyl cellulose and styrene-butadiene rubber. In some more preferred embodiments, the binder comprises, by mass percentage, 40% to 60% phenolic resin, 15% to 25% sodium carboxymethyl cellulose and 25% to 35% styrene-butadiene rubber.

[0043] As a preferred embodiment, the silica sol is a sol-state dispersion component of nano-scale silicon dioxide particles in a medium; in the present invention, the dispersion medium of the silica sol is ethanol; the colloidal particles in the silica sol have a particle size distribution of 100 μm to 150 μm.

[0044] As a preferred embodiment, the silane coupling agent can be a conventional commercially available type, and the present invention does not strictly limit its composition; in some more preferred embodiments, the amount of the silane coupling agent is 1 to 2 times that of the silica sol by mass.

[0045] As a preferred embodiment, this step (2) specifically includes the following operating steps: first, the binder is heated to soften, and then the first mixture, the silica sol and the silane coupling agent are added, mixed and the second mixture is obtained; it can be understood that the heating temperature is based on the type and melting point of the binder. Taking the binder as phenolic resin as an example, the heating temperature can be carried out at a reference temperature of 60°C to 80°C.

[0046] As a preferred embodiment, the sufficient mixing can be assisted by oscillation, stirring, shaking, centrifugation, ultrasound, etc., which helps to accelerate dispersion and obtain a relatively uniform dispersion system; it should be noted that the method of sufficient mixing is not specifically limited, and manual stirring or mechanical stirring can be used, and specific adaptability can be adjusted according to production scale and equipment.

[0047] (3) coating the second mixture on the surface of the graphite electrode, and then performing heat treatment to obtain a protective layer supported on the graphite electrode. Figure 1 The figure shows the structure of the protective layer-graphite electrode obtained after heat treatment of the present invention. Figure 1 It can be seen that the protective layer of the present invention is usually supported on the curved side surface of the rod-shaped electrode. When the electrode is not a rod-shaped structure, those skilled in the art can adaptively perform coating and heat treatment on the corresponding side surface.

[0048] As a preferred embodiment, the heat treatment includes the following steps: first drying at 80℃~100℃ for 1h~2h, then curing at 120℃~150℃ for 2h~3h, and then sintering at 1800℃~2000℃ for 3h~5h.

[0049] As a preferred embodiment, the coating is performed by either dipping or spraying; after the coating and before the heat treatment, the thickness of the coating layer is 1 mm to 3 mm.

[0050] As a preferred embodiment, the following steps are further included before the coating: polishing and cleaning the graphite electrode, including but not limited to surface polishing with a tool or a grinding wheel, as well as brushing, descaling, and water washing.

[0051] A fourth aspect of the present invention provides photovoltaic applications of the graphite electrode protective layer described in the second aspect. Specifically, such applications include, but are not limited to, graphite electrodes containing the graphite electrode protective layer, photovoltaic cells or photovoltaic energy products obtained therefrom, and processes such as methods for preparing and using such products. The present invention does not impose any restrictions on the specific types of such applications; any product or process in the art that contains the graphite electrode protective layer is considered an embodiment of this aspect.

[0052] Example 1

[0053] (1) Prepare the following raw materials: 35 parts by weight of silicon carbide (5-10 μm), 20 parts by weight of aluminum oxide (3-5 μm), 7.5 parts by weight of yttrium oxide (1-3 μm), 20 parts by weight of boron carbide (2-4 μm), 15 parts by weight of titanium dioxide (50-100 nm), 15 parts by weight of zirconium oxide (30-80 nm), and 7.5 parts by weight of cerium oxide.

[0054] (2) The raw materials prepared in step (1) above were mixed with 100 parts by weight of anhydrous ethanol, added to a ball mill, set the ball milling power to 1.5 kW, the speed to 200 r / min, and continued ball milling for 10 h to fully mix the inorganic components and obtain ball mill material.

[0055] (3) preparing 50 wt.% of phenolic resin, 20 wt.% of sodium carboxymethyl cellulose and 30 wt.% of styrene-butadiene rubber, and fully mixing them to prepare a binder; taking 15 parts by weight of the binder, heating it to 70°C to soften it, adding the ball mill material of step (2), 5.5 parts by weight of silica sol and 8.25 parts by weight of silane coupling agent thereto, and continuously stirring the mixture at 2000 r / min for 3 hours in a high-speed stirrer to form a uniform composite slurry.

[0056] (4) Prepare a clean graphite electrode and evenly spray the composite slurry of step (3) on the surface of the graphite electrode to a thickness of 2 mm.

[0057] (5) The sprayed graphite electrode is first dried at 90°C for 1.5 hours to initially remove the solvent; then placed in a high-temperature furnace and cured at 140°C for 2.5 hours to allow the phenolic resin to exert its bonding effect; finally, it is sintered at a high temperature of 1900°C for 4 hours and cooled in the furnace to form an integrated graphite electrode-protective material layer.

[0058] Example 2

[0059] It is basically the same as Example 1, except that the weight ratio of the raw materials in step (1) is: 30 parts by weight of silicon carbide, 15 parts by weight of aluminum oxide, 5 parts by weight of yttrium oxide, 15 parts by weight of boron carbide, 10 parts by weight of titanium dioxide, 10 parts by weight of zirconium oxide, and 5 parts by weight of cerium oxide.

[0060] Example 3

[0061] It is basically the same as Example 1, except that the weight ratio of the raw materials in step (1) is: 40 parts by weight of silicon carbide, 25 parts by weight of aluminum oxide, 10 parts by weight of yttrium oxide, 25 parts by weight of boron carbide, 20 parts by weight of titanium dioxide, 20 parts by weight of zirconium oxide, and 10 parts by weight of cerium oxide.

[0062] Comparative Example 1

[0063] Prepare the same mixture as step (1) of Example 1, prepare 100 parts by weight of anhydrous ethanol and 33 parts by weight of a silane coupling agent, mix and stir the above raw materials at 500 r / min for 30 minutes to obtain a mixed slurry; then follow steps (4) to (5) of Example 1 to obtain the graphite electrode-protective material layer of this comparative example.

[0064] Comparative Example 2

[0065] Prepare the same mixture as step (1) of Example 2, prepare 100 parts by weight of anhydrous ethanol and 33 parts by weight of a silane coupling agent, mix and stir the above raw materials at 500 r / min for 30 minutes to obtain a mixed slurry; then follow steps (4) to (5) of Example 2 to obtain the graphite electrode-protective material layer of this comparative example.

[0066] Comparative Example 3

[0067] Prepare the same mixture as step (1) of Example 3, prepare 100 parts by weight of anhydrous ethanol and 33 parts by weight of a silane coupling agent, mix and stir the above raw materials at 500 r / min for 30 minutes to obtain a mixed slurry; then follow steps (4) to (5) of Example 3 to obtain the graphite electrode-protective material layer of this comparative example.

[0068] Test example

[0069] The graphite electrodes prepared in each example and comparative example and loaded with protective material layers were tested for surface corrosion rate and pulverization rate of the protective material layer after 550 hours of etching in a single crystal furnace. The resistivity of each graphite electrode and the lifespan of the protective material layer were also measured, and the cost of the protective material layer per electrode was calculated. The test results are shown in Table 1 below.

[0070] Table 1

[0071]

[0072] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A graphite electrode protective material, characterized in that: It includes the following components in parts by mass: 25-50 parts of silicon carbide, 15-25 parts of aluminum oxide, 5-10 parts of yttrium oxide, 15-25 parts of boron carbide, 10-20 parts of titanium dioxide, 10-20 parts of zirconium oxide and 5-10 parts of cerium oxide.

2. The graphite electrode protective material according to claim 1, characterized in that The graphite electrode protection material includes at least one of the following features (a) to (f): (a) the particle size of the silicon carbide is 5 μm to 10 μm; (b) the particle size of the aluminum oxide is 3 μm to 5 μm; (c) the particle size of the yttrium oxide is 1 μm to 3 μm; (d) the particle size of the boron carbide is 2 μm to 4 μm; (e) the particle size of the titanium dioxide is 50 nm to 100 nm; (f) The particle size of the zirconium oxide is 30 nm to 80 nm.

3. A graphite electrode protective layer, characterized in that: Comprising the graphite electrode protection material as described in claim 1 or 2.

4. The method for preparing a graphite electrode protective layer according to claim 3, wherein: The steps include: Wet-mixing and grinding silicon carbide, aluminum oxide, yttrium oxide, boron carbide, titanium dioxide, zirconium oxide, and cerium oxide to obtain a first mixed material; Fully mixing the first mixed material, binder, silica sol and silane coupling agent to obtain a second mixed material; The second mixture is coated on the surface of the graphite electrode, and then subjected to heat treatment to obtain a protective layer supported on the graphite electrode.

5. The preparation method according to claim 4, characterized in that The binder includes the following materials in percentage by mass: Phenolic resin 40%-60%, sodium carboxymethyl cellulose 15%-25% and styrene-butadiene rubber 25%-35%.

6. The preparation method according to claim 4, characterized in that The added amount of the silica sol accounts for 20 wt.% to 40 wt.% of the first mixed material.

7. The preparation method according to claim 4, characterized in that The coating thickness is 1 mm to 3 mm.

8. The preparation method according to claim 4, characterized in that The heat treatment comprises: First, dry it at 80℃~100℃ for 1h~2h, then cure it at 120℃~150℃ for 2h~3h, and then sinter it at 1800℃~2000℃ for 3h~5h.

9. Use of the graphite electrode protection layer as claimed in claim 3 in photovoltaics.

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