Crucible and method for preparing the same

Abstract

A crucible and a preparation method thereof, relating to the field of photovoltaic technology. The preparation method of the crucible comprises: providing a silicon-based crucible substrate, and performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a region to be bonded with a preset roughness; providing a coating raw material, the coating raw material comprising: silicon material and a pore-forming agent; using a melt spraying process to melt the coating raw material and apply it to the region to be bonded, and causing the pore-forming agent to be decomposed to obtain an initial coating with a preset porosity; the initial coating is metallurgically bonded to the region to be bonded; performing an oxidation process on the initial coating to convert the initial coating into a target coating. The preparation method of the crucible can not only reduce the dependence on high-purity quartz sand and alleviate the current situation of quartz sand being in short supply, but also effectively improve the fit between the quartz coating and the silicon nitride crucible substrate.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a crucible and a preparation method thereof. Background Art

[0002] At present, the photovoltaic industry mostly uses the Czochralski method to prepare single crystal silicon. During the crystal pulling process, a crucible is required to hold molten high-temperature silicon liquid. The crucible has become one of the key equipment to ensure the quality of crystal pulling. The crucible is required to be resistant to high temperatures, non-polluting to silicon materials, and have a long service life.

[0003] In the related art, in order to ensure the quality of crystal pulling, quartz crucibles are usually used as consumables and need to be replaced frequently to prevent the quartz crucible from being transformed into silicon dioxide (i.e., "crystallization") after continuous high-temperature operation, which further reduces the quality of silicon rods. However, frequent replacement of quartz crucibles not only seriously reduces production efficiency, but also is not conducive to reducing preparation costs.

[0004] Therefore, how to improve the crucible and its preparation method to ensure the quality of crystal pulling, improve production efficiency and reduce preparation costs has become one of the research directions in this field. Summary of the invention

[0005] The object of the present invention is to provide a crucible and a method for preparing the same, which can not only ensure and improve the quality of crystal pulling, but also reduce the preparation cost of the crucible and improve production efficiency.

[0006] The embodiment of the present invention is achieved as follows:

[0007] One aspect of the present invention provides a method for preparing a crucible, the method comprising: providing a silicon-based crucible substrate, and performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a region to be bonded with a preset roughness; providing a coating raw material, the coating raw material comprising: silicon material and a pore-forming agent; using a melt spraying process to melt the coating raw material and apply it to the region to be bonded, and causing the pore-forming agent to be decomposed to obtain an initial coating with a preset porosity; the initial coating is metallurgically bonded to the region to be bonded; performing an oxidation process on the initial coating to convert the initial coating into a target coating. The method for preparing a crucible can not only reduce the dependence on high-purity quartz sand and alleviate the current situation of insufficient supply of quartz sand, but also effectively improve the fit between the quartz coating and the silicon nitride crucible substrate.

[0008] Optionally, the step of performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain an area to be bonded with a preset roughness includes: performing ultrasonic cleaning on the inner wall surface of the silicon-based crucible substrate; performing drying treatment on the silicon-based crucible substrate after ultrasonic cleaning; performing sandblasting treatment on the inner wall surface of the silicon-based crucible substrate after drying treatment, including: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the silicon-based crucible substrate at a spray pressure of 0.3MPa to 0.6MPa to obtain an area to be bonded with a preset roughness; removing the sandblasting particles remaining in the area to be bonded; wherein the temperature of the drying treatment includes: 60℃~100℃; the duration of the drying treatment includes: 1h~2h; the preset roughness includes: 40μm~80μm.

[0009] Optionally, the step of providing the coating raw material includes: providing granular silicon material and powdered pore-forming agent; placing the granular silicon material and the powdered pore-forming agent in a mixer for mixing to obtain a fully mixed coating raw material.

[0010] Optionally, in the coating raw material, the mass percentage ratio range of the silicon material to the pore-forming agent includes: (50wt%~75wt%): (25wt%~50wt%); the average particle size of the silicon material includes: 50μm~100μm; the thermal decomposition temperature range of the pore-forming agent includes: 550℃~600℃.

[0011] Optionally, the pore-forming agent includes at least one of polyphenylene ester powder, polystyrene powder, and polymethyl methacrylate powder.

[0012] Optionally, the step of melting the coating raw material by a melt spraying process, applying it to the area to be bonded, and decomposing the pore-forming agent to obtain an initial coating with a preset porosity comprises: melting the coating raw material by an atmospheric plasma spraying process, and directly spraying and fully penetrating the molten coating raw material into the area to be bonded of the silicon-based crucible substrate; heat-insulating the silicon-based crucible substrate after the spraying treatment at a preset temperature for a preset time, so that the pore-forming agent in the coating raw material is fully decomposed, and obtaining an initial coating with a preset porosity. An initial coating with a preset porosity; wherein, in the atmospheric plasma spraying process, the spraying power includes: 28kW~40kW; the feed rate includes: 15%~25%; the flow ratio of argon to hydrogen includes: 1:1~8:1; the front cooling gas flow includes: 2bar~7bar; the spraying distance includes: 75mm~100mm; the spraying time includes: 3h~7h; in the insulation treatment, the preset temperature includes: 550℃~650℃; the preset time includes: 2h~3h; the preset porosity includes: 25%~40%.

[0013] Optionally, the step of performing an oxidation process on the initial coating to convert the initial coating into a target coating includes: performing a wet oxidation treatment on the initial coating using a gas containing water vapor and oxygen at an ambient temperature of 850°C to 950°C, so that the initial coating is oxidized into a quartz coating; the quartz coating constitutes the target coating; wherein the flow ratio of the water vapor and the oxygen includes: 2:3 to 6:1; the duration of the wet oxidation treatment includes: 5h to 10h; the thickness of the target coating includes: 1mm to 5mm.

[0014] Optionally, before forming the initial coating, the method further comprises: preheating the silicon-based crucible substrate, wherein the preheating temperature comprises: 250°C to 350°C.

[0015] Another aspect of the present invention provides a crucible obtained by the crucible preparation method as described above, the crucible comprising: a silicon-based crucible substrate, the surface roughness of the inner wall of the silicon-based crucible substrate comprising: 40μm to 80μm; a target coating, which is arranged on the inner wall of the silicon-based crucible substrate and forms a metallurgical bonding structure with the silicon-based crucible substrate; wherein the material of the target coating comprises: quartz.

[0016] Optionally, the target coating has a thickness ranging from 1 mm to 5 mm.

[0017] The beneficial effects of the present invention include:

[0018] The preparation method of the crucible provided in the present application can increase the mechanical bonding force between the coating raw material and the silicon-based crucible substrate in the subsequent steps by performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate, so that the molten coating raw material is tightly bonded to the area to be bonded with a preset roughness. At the same time, by setting the coating raw material components, the initial coating formed has a preset porosity. Based on this, the composition and structure of the initial coating can be fully changed by performing an oxidation process on the initial coating, thereby converting the initial coating into a target coating that meets the requirements for the use of the crucible.

[0019] Furthermore, the raw materials used in preparing the crucible of the present application are silicon powder and pore-forming agent, instead of directly using high-purity quartz sand, thus being able to reduce the preparation cost of the crucible, further contributing to reducing the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 One of the schematic flow diagrams of the method for preparing a crucible provided in an embodiment of the present invention;

[0022] Figure 2 A second schematic flow chart of a method for preparing a crucible provided in an embodiment of the present invention;

[0023] Figure 3 A third schematic flow chart of a method for preparing a crucible provided in an embodiment of the present invention;

[0024] Figure 4 A fourth schematic flow chart of a method for preparing a crucible provided in an embodiment of the present invention;

[0025] Figure 5 The fifth schematic diagram of the process of preparing a crucible provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0030] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Please refer to Figure 1 This embodiment provides a method for preparing a crucible, and the method for preparing a crucible includes:

[0033] S100, providing a silicon-based crucible substrate, and performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a to-be-bonded area with a preset roughness;

[0034] In this step, first, a crucible base is provided as the basic part for preparing the crucible. Considering that silicon-based materials have good high temperature resistance, chemical stability and other characteristics, silicon-based materials are selected as the material of the crucible base. Then, the inner wall surface of the silicon-based crucible base is surface pretreated to change the microstructure of the inner wall surface through surface pretreatment so that it has a preset roughness, thereby increasing the mechanical bonding force between the coating raw material and the silicon-based crucible base in the subsequent steps, thereby creating the prerequisite for achieving good metallurgical bonding.

[0035] S200, providing coating raw materials, the coating raw materials including: silicon material and pore-forming agent;

[0036] In this step, a coating raw material is then provided. Specifically, the coating raw material includes: silicon material and pore-forming agent, wherein the silicon material as the main component of the coating raw material can make the inner wall surface of the prepared crucible have the required properties such as corrosion resistance and high temperature resistance; and the role of the pore-forming agent is to create pores in the formation process of the initial coating in the subsequent steps, thereby changing the structure and properties of the prepared initial coating so that it can have a preset porosity.

[0037] S400, using a melt spraying process to melt the coating raw material, apply it to the area to be bonded, and decompose the pore-forming agent to obtain an initial coating with a preset porosity; the initial coating and the area to be bonded are in a metallurgical bonding state;

[0038] In this step, first, the coating raw material is heated to a molten state, and then the molten coating raw material is sprayed onto the area to be bonded of the silicon-based crucible substrate (i.e., the inner wall surface of the silicon-based crucible substrate after surface pretreatment in step S100) through a spray gun or other equipment. In this process, the molten coating raw material can be in close contact with the area to be bonded having a preset roughness. In addition, during the melt spraying process, due to the effects of temperature and other conditions, the pore-forming agent decomposes, thereby leaving pores in the coating, forming an initial coating with a preset porosity.

[0039] The above-mentioned metallurgical bonding state refers to the formation of a tight bond between the initial coating and the silicon-based crucible substrate through metallurgical processes such as atomic diffusion. This bonding method is stronger than simple physical adhesion and can ensure that the initial coating is not easy to peel off during use. This is because during the metallurgical bonding process, atoms will diffuse mutually at the interface between the initial coating and the silicon-based crucible substrate to form a transition zone with a gradual change in composition, just like welding the two together.

[0040] For example, the silicon material can be high-purity silicon, and the silicon-based crucible substrate can be made of materials such as silicon nitride. The atomic diffusion between the above-mentioned initial coating and the silicon-based crucible substrate is that the silicon atoms in the initial coating diffuse toward the inside of the silicon-based crucible substrate, and at the same time, the nitrogen atoms in the silicon-based crucible substrate diffuse toward the inside of the initial coating, so that at the interface between the initial coating and the silicon-based crucible substrate, the silicon atoms and the nitrogen atoms are mixed with each other to form a metallurgical bonding state.

[0041] S500 , performing an oxidation process on the initial coating to transform the initial coating into a target coating.

[0042] In this step, finally, the oxidation process can form an oxide layer on the surface of the initial coating, further improving the stability, corrosion resistance and other properties of the coating. The composition and structure of the initial coating can be changed through the oxidation process, thereby converting the initial coating into a target coating that meets the requirements for the use of the crucible. The target coating can isolate and protect the silicon-based crucible substrate.

[0043] Optionally, please refer to Figure 2 S100, the step of performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a to-be-bonded area with a preset roughness comprises:

[0044] S110, performing ultrasonic cleaning on the inner wall surface of the silicon-based crucible substrate;

[0045] In this step, the inner wall surface of the silicon-based crucible substrate is ultrasonically cleaned to remove impurities that affect the bonding of the coating raw material and the silicon-based crucible substrate in the subsequent steps, ensuring that the bonding between the coating raw material and the silicon-based crucible substrate is based on the surface properties of the silicon-based crucible substrate itself without interference from impurities. For example, if there is oil, dust, etc. on the inner wall surface of the silicon-based crucible substrate, the adhesion between the coating raw material and the silicon-based crucible substrate will be reduced.

[0046] S120, performing a drying process on the silicon-based crucible substrate after ultrasonic cleaning;

[0047] In this step, the silicon-based crucible substrate is dried after ultrasonic cleaning. The inner wall surface of the dried silicon-based crucible substrate can provide a dry environment for subsequent sandblasting. If there is moisture on the inner wall surface, the sandblasting particles may adhere unevenly, and the moisture may chemically react with the sandblasting particles, affecting the effect of surface pretreatment.

[0048] The drying temperature is 60°C to 100°C and the drying time is 1h to 2h to effectively remove the residual moisture on the inner wall of the silicon-based crucible substrate after ultrasonic cleaning. It should be noted that too high a drying temperature or too long a drying time may have adverse effects on the silicon-based crucible substrate, such as causing thermal stress and cracks in the substrate; while too low a drying temperature or too short a drying time may not completely dry the silicon-based crucible substrate.

[0049] S130, performing sandblasting on the inner wall surface of the silicon-based crucible substrate after the drying process, including: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the silicon-based crucible substrate at a spraying pressure of 0.3 MPa to 0.6 MPa, so as to obtain a to-be-bonded area with a preset roughness; wherein the preset roughness includes: 40 μm to 80 μm;

[0050] In this step, the particle size of the sandblasting particles and the pressure of the blasting treatment will affect the impact effect of the sandblasting particles on the inner wall surface of the silicon-based crucible substrate. Sandblasting particles with a suitable particle size range can effectively hit the inner wall surface under a suitable blasting pressure, causing tiny pits and protrusions on the surface, thereby forming a preset roughness, while not causing excessive damage to the silicon-based crucible substrate, such as destroying the overall structural integrity of the silicon-based crucible substrate.

[0051] S140, removing the sandblasting particles remaining in the area to be bonded;

[0052] In this step, after the sandblasting, some sandblasting particles will inevitably remain on the inner wall surface of the silicon-based crucible substrate. If these residual particles are not removed, they will affect the bonding quality between the coating raw material and the silicon-based crucible substrate. For example, during the coating process of the coating raw material, the residual particles may cause local defects in the initial coating formed, such as bubbles, unevenness, etc.

[0053] Optionally, please refer to Figure 3 , S200, the step of providing coating raw materials comprises:

[0054] S210, providing granular silicon material and powdered pore-forming agent;

[0055] S220, placing the granular silicon material and the powdered pore-forming agent in a mixer for mixing to obtain a fully mixed coating raw material.

[0056] In this step, the granular silicon material has a certain particle size distribution and its physical properties are relatively stable, while the powdered pore-forming agent has a large specific surface area. The granular silicon material and the powdered pore-forming agent are placed in a mixer, and the mixer uses mechanical actions such as stirring and tumbling to make the two raw materials fully contact. In this way, the powdered pore-forming agent can be more evenly dispersed among the granular silicon materials during the mixing process, so that in the subsequent melt spraying and pore-forming agent decomposition process, the porosity of each part of the coating can be kept consistent.

[0057] Optionally, in the coating raw material, the mass percentage ratio of silicon material to pore-forming agent includes: (50wt%~75wt%): (25wt%~50wt%), for example, the mass percentage ratio of silicon material to pore-forming agent can be 50wt%:50wt%, 60wt%:40wt%, 70wt%:30wt% or 75wt%:25wt%; the average particle size of silicon material includes: 50μm~100μm, for example, the average particle size of silicon material can be 50μm, 60μm, 70μm, 80μm, 90μm or 100μm; the thermal decomposition temperature range of the pore-forming agent includes: 550℃~600℃, for example, the thermal decomposition temperature of the pore-forming agent is 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃.

[0058] Optionally, the pore-forming agent includes at least one of polyphenylene ester powder, polystyrene powder, and polymethyl methacrylate powder. Since the above materials can decompose or volatilize in a predictable manner at high temperature, the porosity of the initial coating can be accurately adjusted by controlling the content of the pore-forming agent and the temperature of melt spraying, and its decomposition temperature can also match the stability of melt spraying; in addition, since the above materials are all organic polymer materials, they can be fully mixed with silicon materials during the coating raw material mixing stage, and the interaction with silicon materials during the melt spraying process is also relatively stable, which helps the coating maintain structural integrity.

[0059] Optionally, please refer to Figure 4 S400, the step of melting the coating raw material by a melt spraying process, applying the coating raw material to the area to be bonded, and decomposing the pore forming agent to obtain an initial coating with a preset porosity includes:

[0060] S410, using an atmospheric plasma spraying process to melt the coating raw material, and directly spraying the molten coating raw material and fully penetrating it into the to-be-bonded area of ​​the silicon-based crucible substrate; wherein, in the atmospheric plasma spraying process, the spraying power includes: 28kW to 40kW; the feed rate includes: 15% to 25%; the flow ratio of argon gas to hydrogen includes: 1:1 to 8:1; the front cooling gas flow includes: 2bar to 7bar; the spraying distance includes: 75mm to 100mm; the spraying time includes: 3h to 7h;

[0061] In this step, the atmospheric plasma spraying process is a commonly used thermal spraying technology, which uses the high temperature generated by plasma to melt the coating raw materials. Specifically, inside the spray gun, the working gas (such as argon and hydrogen, etc.) is ionized by arc discharge to form a high-temperature plasma jet, the temperature of which can be as high as tens of thousands of degrees Celsius, which can quickly heat the coating raw materials fed into it to a molten state; then, the high speed and high temperature characteristics of the plasma jet make the molten coating raw materials have sufficient kinetic energy to impact the surface of the area to be bonded, and fill the microscopic pores and bumps on the surface at the moment of impact, achieving full penetration, laying the foundation for the subsequent metallurgical bonding with the silicon-based crucible substrate and ensuring the uniformity of the initial coating.

[0062] By precisely controlling the various parameters of the atmospheric plasma spraying process, it is possible to ensure that the coating raw materials are fully melted and evenly and fully penetrate into the area to be bonded, forming a good metallurgical bond with the silicon-based crucible substrate, so that the initial coating is firmly attached to the silicon-based crucible substrate and is not easy to peel off during subsequent use, effectively improving the overall structural stability of the crucible.

[0063] S420, subjecting the sprayed silicon-based crucible substrate to a heat preservation treatment at a preset temperature and for a preset time, so that the pore-forming agent in the coating raw material is fully decomposed to obtain an initial coating with a preset porosity; wherein, in the heat preservation treatment, the preset temperature includes: 550°C ~ 650°C; the preset time includes: 2h ~ 3h; the preset porosity includes: 25% ~ 40%.

[0064] In this step, the silicon-based crucible substrate after spraying is subjected to a heat preservation treatment at a preset temperature for a preset time, mainly to allow the pore-forming agent in the coating raw material to fully decompose. In this temperature range, the pore-forming agent previously mixed into the coating raw material will undergo a decomposition reaction according to its own thermal decomposition characteristics, resulting in gas escape, thereby leaving pores in the coating and forming an initial coating with a preset porosity. Among them, if the heat preservation time is too short, the pore-forming agent may not be completely decomposed and the preset porosity cannot be achieved; and if the heat preservation time is too long, it may have an adverse effect on other properties of the coating and the substrate, such as making the coating structure too loose.

[0065] Optionally, S500, the step of performing an oxidation process on the initial coating to convert the initial coating into a target coating includes:

[0066] S510, performing wet oxidation treatment on the initial coating using a gas containing water vapor and oxygen at an ambient temperature of 850° C. to 950° C., so that the initial coating is oxidized into a quartz coating; the quartz coating constitutes a target coating;

[0067] The flow ratio of water vapor and oxygen includes: 2:3 to 6:1; the duration of wet oxidation treatment includes: 5h to 10h; and the thickness of the target coating includes: 1mm to 5mm.

[0068] In this step, the microstructure and performance of the quartz coating can be precisely adjusted by controlling the flow ratio of water vapor and oxygen and the duration of the wet oxidation treatment. Those skilled in the art should be able to select a suitable flow ratio and duration according to the preferred range provided in this application, so that the generated quartz coating has a uniform structure and good compactness, thereby improving the mechanical properties and barrier properties of the target coating, for example, better preventing substances such as oxygen and water vapor from contacting the silicon-based crucible substrate. In addition, the thickness of the target coating can be between 1 mm and 5 mm, which can not only ensure the protective effect of the target coating, but also avoid the degradation of the coating quality caused by thickness problems. For example, in a high temperature environment, a coating of suitable thickness can effectively prevent heat from being conducted to the crucible substrate too quickly, reducing the risk of damage to the crucible substrate due to thermal stress.

[0069] Optionally, please refer to Figure 5 , S400, before forming the initial coating, the method for preparing the crucible further comprises:

[0070] S300, preheating the silicon-based crucible substrate, wherein the preheating temperature includes: 250°C to 350°C.

[0071] In this step, before the coating raw material is coated on the silicon-based crucible substrate by the melt spraying process, the substrate is preheated. The preheated substrate can provide a more favorable temperature environment for the formation of the initial coating. When the preheated substrate contacts the melt-sprayed coating raw material, the coating raw material can maintain good fluidity at the moment of contact due to the high substrate temperature, which helps the coating raw material to better penetrate into the area to be bonded of the substrate (the rough inner wall surface after surface pretreatment), fill microscopic pores and pits, thereby enhancing the mechanical bite between the coating and the substrate and improving the bonding strength between the coating and the substrate.

[0072] This embodiment also provides a crucible, which is obtained by the above-mentioned crucible preparation method, and the crucible includes: a silicon-based crucible substrate, the surface roughness of the inner wall of the silicon-based crucible substrate includes: 40μm to 80μm; a target coating, which is arranged on the inner wall of the silicon-based crucible substrate and forms a metallurgical bonding structure with the silicon-based crucible substrate; wherein the material of the target coating includes: quartz. Optionally, the thickness of the target coating includes: 1mm to 5mm.

[0073] In this step, where the specific structure of the crucible provided in this embodiment is the same as that of the preparation method of the crucible in the previous text, a person skilled in the art can infer the specific structure of the crucible based on the description of the preparation method of the crucible in the previous text, and this application will not repeat the description. Since the crucible provided in this embodiment is prepared by the preparation method of the crucible described above, the crucible has the same beneficial effects as the preparation method of the crucible described above, and will not be described in detail here.

[0074] Embodiment 1:

[0075] 1) The substrate is a 28-inch silicon nitride crucible substrate.

[0076] 2) The silicon nitride crucible substrate was ultrasonically cleaned 3 times with deionized water and anhydrous ethanol respectively, and dried at 80°C for 1 hour. The purpose is to remove the surface dirt of the silicon nitride crucible substrate, reduce the contamination of the interface between the silicon nitride crucible substrate and the initial coating formed subsequently, and reduce the effect of surface dirt on the bonding strength between the silicon nitride crucible substrate and the initial coating.

[0077] 3) The inner wall surface of the dried silicon nitride crucible substrate is sandblasted to improve the roughness of the bonding surface between the silicon nitride crucible substrate and the initial coating, enhance the mechanical bite between the initial coating and the silicon nitride crucible substrate, and increase the bonding strength. Silicon carbide, corundum and quartz sand can be used for sandblasting, preferably 22-mesh quartz sand. During sandblasting, the injection pressure is 0.3MPa. After sandblasting, an air gun is used to remove the residual sandblasting particles in the area to be bonded.

[0078] 4) Place the purchased 75μm silicon powder in a mixer (such as a blender), add 25wt% of polyphenyl ester powder, and mix in the blender. The mixer speed is 100r / min, and the time is 3h. The purpose is to fully mix the silicon powder and polyphenyl ester powder, which is conducive to the formation of multiple pores in the initial coating with a preset porosity. The pores can provide diffusion channels for water vapor in the subsequent wet oxidation treatment, and can also be used to relieve the stress caused by the volume expansion of the initial coating when it is oxidized into a quartz coating.

[0079] 5) The initial coating was deposited using the MultiCoat automatic thermal spraying system produced by Oerlikon Metco of Switzerland. The spraying distance was 75 mm, the spraying power of the atmospheric plasma spraying equipment was 28 kW, the feed rate was 15%, the flow ratio of argon to hydrogen was 3:1, the front cooling gas flow was 3 bar, and the preheating temperature of the silicon nitride crucible substrate was 250 ° C. This method can be used to prepare an initial coating with a porous structure with a thickness of 3 mm, and the preparation time is 4 hours.

[0080] 6) The sprayed silicon nitride crucible substrate is placed in a muffle furnace and kept at 550° C. for 2 h, in order to decompose the polyphenylene ester remaining in the initial coating of the porous structure, thereby increasing the porosity of the coating.

[0081] 7) The crucible after the above treatment is subjected to wet oxidation treatment at 850°C using a gas containing water vapor and oxygen, with a flow ratio of water vapor to oxygen of 2:1 for 6 hours, so that water vapor can penetrate into the interior from the pores in the initial coating and the initial coating is oxidized into a quartz coating, thereby achieving the purpose of preparing a quartz coating on the surface of the silicon nitride crucible substrate.

[0082] Embodiment 2:

[0083] 1) The substrate is a 36-inch silicon nitride crucible substrate.

[0084] 2) The silicon nitride crucible substrate was ultrasonically cleaned 3 times with deionized water and anhydrous ethanol respectively, and dried at 100°C for 2 hours. The purpose is to remove the surface dirt of the silicon nitride crucible substrate, reduce the contamination of the interface between the silicon nitride crucible substrate and the initial coating formed subsequently, and reduce the effect of surface dirt on the bonding strength between the silicon nitride crucible substrate and the initial coating.

[0085] 3) The inner wall surface of the dried silicon nitride crucible substrate is sandblasted to improve the roughness of the bonding surface between the silicon nitride crucible substrate and the initial coating, enhance the mechanical bite between the initial coating and the silicon nitride crucible substrate, and increase the bonding strength. Silicon carbide, corundum and quartz sand can be used for sandblasting, preferably 40 mesh quartz sand. During sandblasting, the injection pressure is 0.6MPa. After sandblasting, an air gun is used to remove the residual sandblasting particles in the area to be bonded.

[0086] 4) Place the purchased 100μm silicon powder in a mixer (such as a blender), add 50wt% polyphenyl ester powder by mass, and mix in the blender. The mixer speed is 150r / min, and the time is 6h. The purpose is to fully mix the silicon powder and polyphenyl ester powder, which is conducive to the formation of multiple pores in the initial coating with a preset porosity. The pores can provide diffusion channels for water vapor in the subsequent wet oxidation treatment, and can also be used to relieve the stress caused by the volume expansion of the initial coating when it is oxidized into a quartz coating.

[0087] 5) The initial coating was deposited by a MultiCoat automatic thermal spraying system produced by Oerlikon Metco of Switzerland. The spraying distance was 100 mm, the spraying power of the atmospheric plasma spraying equipment was 40 kW, the feed rate was 25%, the flow ratio of argon to hydrogen was 8:3, the front cooling gas flow was 7 bar, and the preheating temperature of the silicon nitride crucible substrate was 350 ° C. This method can be used to prepare an initial coating with a porous structure with a thickness of 5 mm, and the preparation time is 6 hours.

[0088] 6) The sprayed silicon nitride crucible substrate is placed in a muffle furnace and kept at 650° C. for 3 h, in order to decompose the polyphenylene ester remaining in the initial coating of the porous structure, thereby increasing the porosity of the coating.

[0089] 7) The crucible after the above treatment is subjected to wet oxidation treatment at 950°C using a gas containing water vapor and oxygen, with a flow ratio of water vapor to oxygen of 5:2 for 10 hours, so that water vapor can penetrate into the interior from the pores in the initial coating and the initial coating is oxidized into a quartz coating, thereby achieving the purpose of preparing a quartz coating on the surface of the silicon nitride crucible substrate.

[0090] The above description is only an optional embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0091] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a crucible, characterized in that: include: Providing a silicon-based crucible substrate, and performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a to-be-bonded area with a preset roughness; Providing a coating material, wherein the coating material comprises: a silicon material and a pore-forming agent; The coating raw material is melted and coated on the area to be bonded by a melt spraying process, and the pore-forming agent is decomposed to obtain an initial coating with a preset porosity; the initial coating is in a metallurgical bonding state with the area to be bonded; An oxidation process is performed on the initial coating to convert the initial coating into a target coating.

2. The method for preparing a crucible according to claim 1, characterized in that: The step of performing surface pretreatment on the inner wall surface of the silicon-based crucible substrate to obtain a to-be-bonded area with a preset roughness comprises: Performing ultrasonic cleaning on the inner wall surface of the silicon-based crucible substrate; performing a drying process on the silicon-based crucible substrate after ultrasonic cleaning; The inner wall surface of the silicon-based crucible substrate after the drying treatment is subjected to sandblasting treatment, comprising: using sandblasting particles with an average particle size of 22 mesh to 40 mesh, and spraying them onto the inner wall surface of the silicon-based crucible substrate at a spraying pressure of 0.3 MPa to 0.6 MPa, so as to obtain a to-be-bonded area with a preset roughness; Remove any remaining sandblasting particles from the area to be bonded; in, The temperature of the drying process includes: 60°C to 100°C; The duration of the drying process includes: 1h to 2h; The preset roughness includes: 40μm~80μm.

3. The method for preparing a crucible according to claim 1, characterized in that: The steps of providing the coating raw material include: Provide granular silicon materials and powdered pore formers; The granular silicon material and the powdered pore former are placed in a mixer for mixing to obtain a fully mixed coating material.

4. The method for preparing a crucible according to claim 1, characterized in that: In the coating raw material, the mass percentage ratio of the silicon material to the pore-forming agent includes: (50wt% to 75wt%): (25wt% to 50wt%); The average particle size of the silicon material includes: 50 μm to 100 μm; The thermal decomposition temperature range of the pore-forming agent includes: 550°C to 600°C.

5. The method for preparing a crucible according to claim 1, characterized in that: The pore-forming agent includes at least one of polyphenylene ester powder, polystyrene powder, and polymethyl methacrylate powder.

6. The method for preparing a crucible according to claim 1, characterized in that: The steps of melting the coating raw material by a melt spraying process, coating the coating raw material on the area to be bonded, and decomposing the pore forming agent to obtain an initial coating with a preset porosity include: The coating raw material is melted by an atmospheric plasma spraying process, and the molten coating raw material is directly sprayed and fully penetrated into the to-be-bonded area of ​​the silicon-based crucible substrate; The silicon-based crucible substrate after the spraying treatment is subjected to a heat preservation treatment at a preset temperature and for a preset time, so that the pore-forming agent in the coating raw material is fully decomposed to obtain an initial coating with a preset porosity; Among them, in the atmospheric plasma spraying process, the spraying power includes: 28kW~40kW; the feed rate includes: 15%~25%; the flow ratio of argon and hydrogen includes: 1:1~8:1; the front cooling gas flow includes: 2bar~7bar; the spraying distance includes: 75mm~100mm; the spraying time includes: 3h~7h; During the heat preservation treatment, the preset temperature includes: 550℃~650℃; the preset duration includes: 2h~3h; The preset porosity includes: 25% to 40%.

7. The method for preparing a crucible according to claim 1, characterized in that: The step of performing an oxidation process on the initial coating to convert the initial coating into a target coating comprises: At an ambient temperature of 850° C. to 950° C., the initial coating is subjected to a wet oxidation treatment using a gas containing water vapor and oxygen, so that the initial coating is oxidized into a quartz coating; the quartz coating constitutes the target coating; wherein, The flow ratio of the water vapor to the oxygen includes: 2:3 to 6:1; The duration of wet oxidation treatment includes: 5h to 10h; The target coating has a thickness ranging from 1 mm to 5 mm.

8. The method for preparing a crucible according to any one of claims 1 to 7, characterized in that: Before forming the initial coating, the method further comprises: preheating the silicon-based crucible substrate, wherein the preheating temperature comprises: 250°C to 350°C.

9. A crucible obtained by the method for preparing a crucible according to any one of claims 1 to 8, characterized in that: The crucible comprises: A silicon-based crucible substrate, wherein the surface roughness of the inner wall of the silicon-based crucible substrate is 40 μm to 80 μm; The target coating is disposed on the inner wall surface of the silicon-based crucible substrate and forms a metallurgical bonding structure with the silicon-based crucible substrate; Wherein, the material of the target coating includes: quartz.

10. The crucible according to claim 9, characterized in that The target coating has a thickness ranging from 1 mm to 5 mm.

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