Alumina coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of corrosion protection, and discloses an aluminum oxide coating as well as a preparation method and application thereof. The preparation method comprises the following steps: adding anhydrous aluminum salt into ethanol to prepare an aluminate precursor emulsion; then adding an adhesive to prepare a coating solution; coating a substrate with the film coating liquid, and drying to obtain an aluminum oxide precursor gel layer; and finally, carrying out plasma treatment on the aluminum oxide precursor gel layer to decompose the aluminum oxide precursor gel layer to form alpha-aluminum oxide so as to prepare the aluminum oxide coating. Wherein in the plasma treatment process, air serves as working gas, the flow is 50-200 mL / min, and the temperature of the surface of the aluminum oxide precursor gel layer is 120-200 DEG C. The aluminum oxide coating prepared by the method mainly comprises alpha-Al2O3, is high in compactness and not easy to peel off, and can effectively prolong the service life of the quartz crucible and improve the stability of the quartz crucible.

Description

Technical Field

[0001] The present invention belongs to the technical field of corrosion protection, and in particular relates to an aluminum oxide coating and a preparation method and application thereof. Background Art

[0002] Quartz crucibles are important consumables in the production of single crystal silicon. Extending the life of quartz crucibles means reducing the frequency of crucible replacement and the number of equipment restarts required to replace crucibles, thereby reducing equipment energy consumption and crucible procurement costs.

[0003] In the early stages of a quartz crucible's life, its reaction with molten silicon, heat transfer, and other properties are relatively stable. However, over time, the crucible's walls may become thinner due to reactions, cracking, releasing impurities or microcrystalline particles, and thus deteriorating performance, seriously affecting the quality of single crystal silicon production. Therefore, improving the lifespan and stability of quartz crucibles can reduce production interruptions caused by crucible damage or performance degradation, ensuring continuous production. This is crucial to meeting the continued market demand for single crystal silicon products and completing production tasks on schedule.

[0004] Current research on improving the service life and stability of quartz crucibles focuses on exploring quartz sand purification processes, optimizing quartz crucible preparation processes, coating technologies, and developing composites with other materials. Applying specialized coatings to the surface of quartz crucibles, such as anti-oxidation and anti-corrosion coatings, can improve the crucible's service life and stability. These coatings effectively prevent the quartz crucible from reacting with the silicon melt at high temperatures, reducing impurity generation and crucible wear. Alumina coatings offer advantages such as high hardness, high rigidity, a high melting point, and chemical stability. Current methods for preparing alumina coatings include electrochemical deposition, vapor deposition, sol-gel deposition, high-energy beam surface technology, and thermal spraying. Thermal spraying is an advanced surface engineering technology that plays a crucial role in modern industrial production and maintenance. This technology uses a heat source such as flame, arc, plasma, or compressed gas to heat and accelerate a linear or powdered material, creating a high-speed particle stream. This particle stream cools and solidifies upon impact with the substrate, forming a durable coating on the substrate. Plasma spraying is currently a common thermal spraying method for preparing aluminum oxide coatings. The basic principle of plasma spraying is to use a rigid, non-transferred plasma arc to excite a working gas (nitrogen, helium, or argon, with a small amount of hydrogen) between a cathode (high-melting-point tungsten or graphite material) and an anode (nozzle), thereby generating a high-temperature plasma. This high-temperature flame flows from the spray gun cavity through the nozzle, rapidly melting the sprayed powder after merging with it and condensing and depositing it on the substrate surface. Plasma spraying has developed a variety of plasma spraying methods, including atmospheric (APS), low-pressure or vacuum (LPPS), and suspension or solution precursor (SPS / SPPS).

[0005] Alumina coatings produced by plasma spraying are not without flaws; they also present a number of shortcomings that warrant attention. Plasma-sprayed alumina ceramic coatings exhibit a lamellar structure. While this structure enhances the material's surface strength to a certain extent, it also introduces porosity and microcracks. These microscopic defects not only affect the coating's density but can also lead to flaking or cracking during use. Furthermore, the plasma spraying process reduces the α-Al2O3 content, leaving it primarily in the metastable γ-Al2O3 phase, further weakening the coating's overall performance. Alumina is inherently brittle, sensitive to stress concentration and cracking, and exhibits poor thermal shock resistance. This means the coating is susceptible to damage from drastic temperature fluctuations or impact. Conventional alumina coatings are particularly susceptible to cracking and even flaking in environments with high temperature gradients. Therefore, developing alumina coatings primarily composed of α-Al2O3, with high density and resistance to flaking, is crucial for improving the service life and stability of quartz crucibles. Summary of the Invention

[0006] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides an alumina coating, its preparation method, and its application. The alumina coating prepared by the present invention, primarily composed of α-Al₂O₃, is highly dense and resistant to flaking, effectively extending the service life and stability of quartz crucibles.

[0007] The invention provides a method for preparing an aluminum oxide coating.

[0008] Specifically, a method for preparing an aluminum oxide coating comprises the following steps: Anhydrous aluminum salt is added to ethanol to prepare an aluminate precursor emulsion; a binder is then added to prepare a coating solution; the coating solution is then coated on a substrate and dried to prepare an aluminum oxide precursor gel layer; and finally, the aluminum oxide precursor gel layer is plasma treated to decompose the aluminum oxide precursor gel layer to form α-aluminum oxide, thereby preparing an aluminum oxide coating. The plasma treatment process uses air as the working gas with a flow rate of 50-200 mL / min, and the surface temperature of the alumina precursor gel layer is 120-200°C.

[0009] In some embodiments of the present invention, the anhydrous aluminum salt is anhydrous aluminum chloride.

[0010] In some embodiments of the present invention, the mass ratio of the ethanol to the anhydrous aluminum chloride is (5-10): 1. Preferably, the mass ratio of the ethanol to the anhydrous aluminum chloride is (6-8): 1.

[0011] In some embodiments of the present invention, the adhesive comprises polyvinyl pyrrolidone and / or epoxy resin.

[0012] In some embodiments of the present invention, the binder accounts for 1%-5% of the total mass of the anhydrous aluminum salt and the ethanol; preferably, the binder accounts for 1.5%-3% of the total mass of the anhydrous aluminum salt and the ethanol.

[0013] In some embodiments of the present invention, the coating method includes at least one of dipping, spin coating, and spray coating.

[0014] In some embodiments of the present invention, the substrate is a quartz crucible, especially the inner surface of a quartz crucible.

[0015] In some embodiments of the present invention, the drying temperature is 60-100° C., and the drying time is 12-36 hours.

[0016] In some embodiments of the present invention, the plasma treatment lasts for 10-30 minutes.

[0017] In some embodiments of the present invention, during the plasma treatment, air is used as the working gas at a flow rate of 80-150 mL / min, and the surface temperature of the alumina precursor gel layer is 120-180° C. Preferably, during the plasma treatment, air is used as the working gas at a flow rate of 80-120 mL / min, and the surface temperature of the alumina precursor gel layer is 130-160° C.

[0018] The invention also provides an aluminum oxide coating.

[0019] Specifically, an aluminum oxide coating is prepared by the above preparation method, wherein the main phase of the aluminum oxide coating is α-Al2O3.

[0020] The present invention also provides applications of the aluminum oxide coating.

[0021] Specifically, the alumina coating is used in preparing or repairing a quartz crucible.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) In the preparation method provided by the present invention, the sol-gel method can achieve precise construction of materials from the molecular level to the nanoscale and even the macroscale through the route of chemical solutions, providing a new perspective and method for the development of dense coatings, which has the advantages of high purity, mild reaction conditions, and controllable structure. By combining the sol-gel method with plasma treatment technology, a dense, crack-free α-alumina coating can be generated under low temperature conditions (below 1000°C). The alumina coating can isolate the silicon liquid from direct contact with the inner surface of the quartz crucible, thereby improving the corrosion resistance and stability of the quartz crucible and further increasing the service life of the quartz crucible.

[0023] (2) The present invention utilizes a sol-gel method combined with spraying technology, which allows the thickness of the alumina precursor gel layer to be controlled by the spraying time. Plasma treatment technology is used instead of the traditional calcination process, which has the advantages of short reaction time and low treatment temperature. The combination of the sol-gel method and plasma treatment technology can produce a dense layer of α-alumina on the quartz surface, which is highly dense and not easy to peel off.

[0024] (3) The method provided by the present invention can form an alumina coating on substrates of different sizes and shapes, and can adapt to quartz crucibles of different sizes and shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The macroscopic morphology of the aluminum oxide coating A in Example 1 and the aluminum oxide coating C in Comparative Example 1 is compared; Figure 2 is the XRD pattern of the aluminum oxide coating A in Example 1; Figure 3Elemental analysis diagram of aluminum oxide coating A in Example 1; Figure 4 This is the elemental analysis diagram of the aluminum oxide coating B in Example 2. DETAILED DESCRIPTION

[0026] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0027] Unless otherwise specified, the raw materials, reagents, or devices used in the following experimental examples and embodiments can be obtained from conventional commercial sources or by existing known methods. Example 1

[0028] A method for preparing an aluminum oxide coating comprises the following steps: Weigh 110mL of ethanol and pour it into a beaker. Stir magnetically. Weigh 12.14g of anhydrous aluminum chloride and slowly add it to the beaker in a ventilated place to obtain a white transparent emulsion. Then weigh 2g of polyvinyl pyrrolidone and slowly add it to the beaker. Mix well to obtain coating liquid A. Use a lithium-ion spray gun to spray coating liquid A on the inner surface of the quartz crucible, and then dry it at 80℃ for 24h. After drying, use air with a flow rate of 100mL / min as the working gas, control the substrate surface to 150℃, and perform plasma treatment for 30min to obtain aluminum oxide coating A. The macroscopic morphology of aluminum oxide coating A is as follows: Figure 1 As shown in b, the surface is smooth and there is no peeling phenomenon. The XRD data of aluminum oxide coating A is as follows Figure 2 As shown; the element analysis of alumina coating A is as follows Figure 3 As shown by Figure 2-3 It can be seen that the main elements on the surface are Al and O, and the main phase on the surface is α-Al2O3, which has high density and is not easy to fall off. Example 2

[0029] A method for preparing an aluminum oxide coating comprises the following steps: Weigh 110mL of ethanol and pour it into a beaker. Stir magnetically. Weigh 12.14g of anhydrous aluminum chloride and slowly add it to the beaker in a ventilated place to obtain a white transparent emulsion. Then weigh 2g of E-20 epoxy resin and slowly add it to the beaker. Mix well to obtain coating liquid B. Use a lithium-ion spray gun to spray coating liquid B on the inner surface of the quartz crucible, then dry it at 80℃ for 24h. After drying, use air with a flow rate of 100mL / min as the working gas, control the substrate surface at 150℃, and perform plasma treatment for 30min to obtain aluminum oxide coating B. The elemental analysis of the obtained aluminum oxide coating B is shown as follows: Figure 4 As shown by Figure 4It can be seen that the main elements on its surface are Al and O, and the main phase on the surface is α-Al2O3, which is similar to sample A.

[0030] Comparative Example 1 A method for preparing an aluminum oxide coating comprises the following steps: Weigh 110 mL of ethanol and pour it into a beaker. Stir magnetically. Weigh 12.14 g of anhydrous aluminum chloride and slowly add it to the beaker in a ventilated place to obtain coating solution C. Use a lithium-ion spray gun to spray coating solution C on the inner surface of the quartz crucible, then dry it at 80°C for 24 hours. After drying, use air with a flow rate of 100 mL / min as the working gas, control the substrate surface at 150°C, and perform plasma treatment for 30 minutes to obtain aluminum oxide coating C. The macroscopic morphology of the obtained aluminum oxide coating C is shown in the figure. Figure 1 As shown in a. Figure 1 It can be seen that in the absence of a binder, the surface of the aluminum oxide coating prepared is rough and easily falls off.

[0031] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an aluminum oxide coating, characterized in that: The following steps are involved: Anhydrous aluminum salt is added to ethanol to prepare an aluminate precursor emulsion; Then, a binder is added to prepare a coating solution; The coating liquid is then coated on a substrate and dried to obtain an aluminum oxide precursor gel layer. Finally, the aluminum oxide precursor gel layer is subjected to plasma treatment to decompose the aluminum oxide precursor gel layer to form α-aluminum oxide, thereby obtaining an aluminum oxide coating. The plasma treatment process uses air as the working gas with a flow rate of 50-200 mL / min, and the temperature of the surface of the aluminum oxide precursor gel layer is 120-200°C.

2. The preparation method according to claim 1, characterized in that The anhydrous aluminum salt is anhydrous aluminum chloride.

3. The preparation method according to claim 2, characterized in that The mass ratio of the ethanol to the anhydrous aluminum chloride is (5-10):

1.

4. The preparation method according to claim 1, characterized in that The adhesive includes polyvinyl pyrrolidone and / or epoxy resin.

5. The preparation method according to claim 4, characterized in that The binder accounts for 1%-5% of the total mass of the anhydrous aluminum salt and the ethanol.

6. The preparation method according to claim 1, characterized in that The coating method includes at least one of dipping, spin coating, and spray coating.

7. The preparation method according to claim 1, characterized in that The substrate is a quartz crucible.

8. The preparation method according to claim 6 or 7, characterized in that The plasma treatment process uses air as the working gas with a flow rate of 80-150 mL / min, the surface temperature of the aluminum oxide precursor gel layer is 120-180° C., and the treatment time is 10-30 min.

9. An aluminum oxide coating, characterized in that The aluminum oxide coating is prepared by the preparation method according to any one of claims 1 to 8, wherein the main phase of the aluminum oxide coating is α-Al2O3.

10. Use of the alumina coating according to claim 9 in preparing or repairing a quartz crucible.

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