阅读说明：本技术 用溶胶凝胶烧结法在碳碳复合材料表面制备氮化硼纤维缠绕涂层的方法 (Method for preparing boron nitride fiber winding coating on surface of carbon-carbon composite material by sol-gel sintering method ) 是由 吕铁铮 于 2021-07-30 设计创作，主要内容包括：用溶胶凝胶烧结法在碳碳复合材料表面制备氮化硼纤维缠绕涂层的方法,它涉及晶体硅生产过程中热场碳碳材料抗腐蚀涂层的制备方法。它是要解决现有的碳碳复合材料抗腐蚀涂层容易脱落失效的技术问题。本发明的方法：一、制备氮化硼前驱体溶胶；二、氮化硼前驱体在碳碳复合材料表面凝胶化；三、高温氮化烧结制备薄膜。本发明在碳碳复合材料表面制备的氮化硼纤维膜密实、不会被腐蚀性硅蒸汽,也不会被氧化硅蒸汽腐蚀,氮化硼涂层碳碳坩埚的更换周期由70炉提升到90炉；具有氮化硼涂层的碳碳导流筒的使用寿命从200炉/换提升至250炉/换。可用于抗腐蚀领域。(A method for preparing a boron nitride fiber winding coating on the surface of a carbon-carbon composite material by using a sol-gel sintering method relates to a method for preparing a thermal field carbon-carbon material anti-corrosion coating in the production process of crystalline silicon. The technical problem that an existing carbon-carbon composite material corrosion-resistant coating is prone to falling off and losing efficacy is solved. The method comprises the following steps: firstly, preparing boron nitride precursor sol; secondly, gelling the boron nitride precursor on the surface of the carbon-carbon composite material; thirdly, preparing the film by high-temperature nitridation sintering. The boron nitride fiber film prepared on the surface of the carbon-carbon composite material is compact, cannot be corroded by silicon vapor and cannot be corroded by silicon vapor, and the replacement cycle of the boron nitride coating carbon-carbon crucible is promoted from 70 furnaces to 90 furnaces; the service life of the carbon guide cylinder with the boron nitride coating is prolonged from 200 furnaces/replacement to 250 furnaces/replacement. Can be used in the field of corrosion resistance.)

1. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by using the sol-gel sintering method is characterized by comprising the following steps of:

firstly, preparing boron nitride precursor sol:

adding boric acid into deionized water, and stirring and dissolving at 60-90 ℃ to obtain a boric acid solution;

adding melamine into deionized water, performing ultrasonic separation by using a 400W ultrasonic cleaning machine, and stirring by using magnetic stirring equipment to form melamine suspension;

adding the melamine suspension into a boric acid solution at the temperature of 90-100 ℃, and continuously stirring until the solution becomes transparent to obtain precursor sol;

secondly, gelling the boron nitride precursor on the surface of the carbon-carbon composite material:

maintaining the temperature of the precursor sol at 80-95 ℃, impregnating or coating the surface of the carbon-carbon composite material, and then cooling to room temperature to gelatinize the precursor on the surface of the carbon-carbon composite material;

thirdly, preparing a film by high-temperature nitridation sintering:

sintering the carbon-carbon composite material with the surface precursor gelled in a protective gas at a high temperature of 600-1400 ℃ for 2-10 hours;

fourthly, repeating the operation of the second step and the operation of the third step to obtain the boron nitride fiber winding coating on the surface of the carbon-carbon composite material.

2. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to claim 1, wherein the molar ratio of the boric acid to the melamine in the precursor sol in the step one is 1:

(2～4)。

3. the method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to claim 1 or 2, wherein the concentration of the boric acid solution in the first step is 0.075-0.15 g/ml.

4. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to claim 1 or 2, wherein the concentration of the melamine suspension in the step one is 0.063-0.126 g/ml.

5. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to claim 1 or 2, wherein the amount of the precursor sol impregnated or coated on the surface of the carbon-carbon composite material in the step two is 0.1ml/cm²。

6. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to the claim 1 or 2, wherein the protective gas in the third step is nitrogen or argon.

7. The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by the sol-gel sintering method according to claim 1 or 2, wherein the carbon-carbon composite material in the third step is a carbon-carbon crucible, a carbon-carbon guide cylinder or a carbon-carbon bushing.

Technical Field

The invention relates to a preparation method of a thermal field carbon material anti-corrosion coating in a crystalline silicon production process.

Background

Photovoltaic power generation is a typical new energy source and has the characteristics of convenient application and no pollution. With the rapid development of global economy, the demand of various industries on energy is increasing day by day, the traditional fossil energy such as coal and petroleum causes serious pollution to the atmosphere on which human beings live, the awareness of human beings for protecting the green environment is strengthened, the aim of carbon neutralization is provided, and the development of new energy with zero pollution becomes the main direction for the adjustment of energy industries of various countries. At present, the photovoltaic cells are developed in various types, including crystalline silicon cells and thin film solar cells (such as cadmium telluride solar cells, perovskite solar cells and copper indium gallium selenide solar cells), wherein the crystalline silicon technology is developed most mature, the cost is reduced rapidly, the crystalline silicon technology occupies more than 90% of the current photovoltaic power generation market, and the crystalline silicon solar cells are the mainstream photovoltaic technology in the future 10-15 years. The industrial chain of the crystalline silicon photovoltaic product comprises various links of an upstream and a downstream, such as a polycrystalline silicon raw material- > a silicon wafer- > a battery piece- > component, wherein the silicon wafer production is an intermediate process of silicon crystal growth and re-cutting.

The growth of silicon crystals needs to use a high-temperature electric furnace, according to industry statistical data, the productivity of the 2021 year crystal silicon photovoltaic component reaches about 200GW, and the corresponding silicon wafer production link has tens of thousands of single crystal pulling furnaces, wherein in the single crystal pulling furnaces, a large amount of carbon felts are needed as heat-insulating thermal field materials, and a large amount of carbon-carbon composite materials are used as structural members in high-temperature equipment such as thermal field crucibles, bushings, guide cylinders and the like due to the unique characteristics of high temperature resistance, high strength and the like. However, the carbon-carbon composite material has no good corrosion resistance, and is easily corroded and pulverized by high-temperature silicon vapor from raw materials and silicon oxide vapor from a quartz crucible in the growth process of crystalline silicon, so that the crystalline silicon becomes brittle and loose, the structural strength is greatly reduced, the service life is shortened, and the carbon-carbon composite material is frequently replaced as a consumable material of a crystal growth furnace, so that the corrosion resistance of the carbon-carbon composite material is improved, the service life of a carbon thermal field in the crystal furnace can be further prolonged, the production cost of a silicon wafer is reduced, and the cost of photovoltaic power generation is further reduced.

A common corrosion-resistant method for carbon-carbon composite materials is to uniformly mix corrosion-resistant materials, such as silicon carbide, boron nitride and the like, with an organic binder, such as phenolic resin and the like, and a solvent, then brush and solidify the mixture on the surface of the carbon-carbon material, and then carry out heat treatment to form an interface coating of the pyrolytic carbon bonded corrosion-resistant material, but the pyrolytic carbon is also a carbon component, and oxidation weight loss can be generated at a lower temperature (about 450 ℃) to cause interface failure, and under the high-temperature application condition of a single crystal silicon furnace, the pyrolytic carbon serving as the binder can be corroded by silicon vapor and the like to lose binding force, and the corrosion-resistant materials, such as silicon carbide, boron nitride and the like, can be pulverized and fall off. Therefore, in order to prepare a surface coating which has both the mechanical property and the anti-silicification property of the composite material, the scheme that pyrolytic carbon is used as a binder cannot be used, and the selection of a proper interface material for corrosion resistance of the carbon-carbon composite material is the direction of the efforts in the carbon-carbon industry.

Disclosure of Invention

The invention provides a method for preparing a boron nitride fiber winding coating on the surface of a carbon-carbon composite material by a sol-gel sintering method, aiming at solving the technical problem that the existing carbon-carbon composite material corrosion-resistant coating is easy to fall off and lose efficacy.

The method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by using the sol-gel sintering method comprises the following steps of:

firstly, preparing boron nitride precursor sol:

adding boric acid into deionized water, and stirring and dissolving at 60-90 ℃ to obtain a boric acid solution;

adding melamine into deionized water, performing ultrasonic separation by using a 400W ultrasonic cleaning machine, and stirring by using magnetic stirring equipment to form melamine suspension;

adding the melamine suspension into a boric acid solution at the temperature of 90-100 ℃, and continuously stirring until the solution becomes transparent to obtain precursor sol;

secondly, gelling the boron nitride precursor on the surface of the carbon-carbon composite material:

maintaining the temperature of the precursor sol at 80-95 ℃, impregnating or coating the surface of the carbon-carbon composite material, and then cooling to room temperature to gelatinize the precursor on the surface of the carbon-carbon composite material;

thirdly, preparing a film by high-temperature nitridation sintering:

sintering the carbon-carbon composite material with the surface precursor gelled in a protective gas at a high temperature of 600-1400 ℃ for 2-10 hours;

fourthly, repeating the operation of the second step and the operation of the third step to obtain the boron nitride fiber winding coating on the surface of the carbon-carbon composite material.

Further, the molar ratio of boric acid to melamine in the precursor sol in the first step is 1: (2-4).

Furthermore, the concentration of the boric acid solution in the first step is 0.075-0.15 g/ml.

Furthermore, the concentration of the melamine suspension in the step one is 0.063-0.126 g/ml.

Furthermore, the amount of the precursor sol for impregnating or coating the surface of the carbon-carbon composite material in the step two is 0.1ml/cm²。

Further, the protective gas in step three is nitrogen or argon.

Furthermore, the carbon-carbon composite material in the third step is a carbon-carbon crucible, a carbon-carbon guide cylinder or a carbon-carbon lining.

According to the invention, a boron nitride precursor sol is adopted and covered and combined on the surface of the carbon-carbon composite material, gel is formed on the surface of the carbon-carbon composite material through cooling, the gel is solidified and then sintered at high temperature to prepare the boron nitride fiber film, the formed boron nitride coating has a fibrous microscopic appearance, can be mutually wound with carbon fibers on the surface of the carbon-carbon composite material and is firmly bonded on the surface of the carbon-carbon composite material, and the coating is not easy to fall off in the actual production process; and meanwhile, the steps of sol-gel and nitridation sintering are repeated, so that the boron nitride fiber film on the surface of the carbon-carbon composite material becomes dense and becomes a relatively dense protective film, and the corrosion resistance of the carbon-carbon composite material is improved. The thermal field component with the boron nitride fiber winding coating, such as a carbon-carbon crucible, a carbon-carbon guide cylinder or a carbon-carbon lining, cannot be corroded by silicon vapor and silicon oxide vapor, so that the service life of the carbon-carbon composite material thermal field component is remarkably prolonged, wherein the replacement cycle of the carbon-carbon crucible with the boron nitride coating is promoted from 70 furnaces to 90 furnaces; the service life of the carbon guide cylinder with the boron nitride coating is prolonged from 200 furnaces/replacement to 250 furnaces/replacement.

The boron nitride anti-corrosion coating is prepared by a sol-gel method, and has the characteristics of uniform distribution, low cost and easy operation.

Drawings

FIG. 1 is a schematic diagram of a process for preparing a boron nitride winding coating according to the present invention;

FIG. 2 is an optical microscope photograph of a carbon-carbon crucible of example 1 before a boron nitride coating is grown on the surface thereof;

FIG. 3 is an optical microscope photograph of the surface of the carbon-carbon crucible of example 1 after growing a boron nitride coating thereon;

FIG. 4 is a scanning electron micrograph of a boron nitride coating grown on the surface of the carbon-carbon crucible in example 1.

Detailed Description

The following examples are used to demonstrate the beneficial effects of the present invention.

Example 1: the method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by using the sol-gel sintering method comprises the following steps:

firstly, preparing boron nitride precursor sol:

adding 372g of boric acid into 4L of distilled water, and stirring and dissolving at 60 ℃ to obtain a boric acid solution;

adding 252g of melamine into 4L of distilled water, then carrying out ultrasonic separation by using a 400W ultrasonic cleaning machine, and then stirring by using electric stirring equipment to form uniform and stable milky melamine suspension;

adding the melamine suspension into a boric acid solution at the temperature of 90 ℃, and continuously stirring until the solution becomes transparent to obtain precursor sol;

secondly, gelling the boron nitride precursor on the surface of the carbon-carbon composite material:

keeping the temperature of the precursor sol at 80-90 ℃ to keep the precursor sol in a flowing state, fully infiltrating the surface of the carbon-carbon composite material and entering gaps of the carbon-carbon material to form full contact, coating the prepared 8L precursor sol on the inner surface of a carbon-carbon crucible of a 32-inch single crystal silicon furnace, and then cooling to 25 ℃ to gelatinize the precursor on the surface of the carbon-carbon crucible; the white gel formed is C₃N₆H₆·2H₃BO₃Abbreviated as M.2B;

thirdly, preparing a film by high-temperature nitridation sintering:

drying the carbon-carbon crucible with the precursor gelled on the surface in a drying oven at 110 ℃ for 12 hours, removing water, then placing in nitrogen for high-temperature sintering at 1000 ℃ for 4 hours, wherein the gel undergoes a chemical polycondensation reaction during sintering to form crystalline boron nitride fibers and a film;

fourthly, repeating the operation of the second step and the operation of the third step once again to obtain the boron nitride fiber winding coating on the surface of the carbon-carbon crucible.

An optical microscope image before the boron nitride coating grows on the surface of the carbon-carbon crucible of the embodiment is shown in fig. 2, and it can be seen from the image that the surface of the carbon-carbon crucible is smooth, and the black matrix carbon fiber is clearly visible;

an optical microscope image of the carbon-carbon crucible surface after growing the boron nitride coating is shown in fig. 3, and it can be seen from the image that the carbon-carbon crucible surface has a layer of white flocculent material coating, covering the carbon-carbon crucible surface;

the scanning electron microscope photograph of the carbon-carbon crucible surface with the boron nitride coating grown thereon in this embodiment is shown in fig. 4, and it can be seen from fig. 4 that the microscopic morphology of the boron nitride coating formed on the carbon-carbon crucible surface is fibrous, and the boron nitride coating is intertwined with the carbon fibers on the carbon-carbon composite material surface and is firmly bonded to the carbon-carbon composite material surface.

The corrosion resistance of the carbon crucible with the boron nitride coating is greatly improved, and the service life of the carbon crucible with the boron nitride fiber winding coating prepared in the example 1 is prolonged from 70 furnaces/replacement to 90 furnaces/replacement.

Example 2: the method for preparing the boron nitride fiber winding coating on the surface of the carbon-carbon composite material by using the sol-gel sintering method comprises the following steps:

firstly, preparing boron nitride precursor sol:

adding 465g of boric acid into 5L of distilled water, and stirring and dissolving at 60 ℃ to obtain a boric acid solution;

adding 315g of melamine into 5L of distilled water, then carrying out ultrasonic separation by using a 400W ultrasonic cleaning machine, and then stirring by using electric stirring equipment to form uniform and stable milky melamine suspension;

adding the melamine suspension into a boric acid solution at the temperature of 90 ℃, and continuously stirring until the solution becomes transparent to obtain precursor sol;

secondly, gelling the boron nitride precursor on the surface of the carbon-carbon composite material:

keeping the temperature of the precursor sol at 80-85 ℃ to keep the precursor sol in a flowing state, coating 5L of the precursor sol on the inner surface of a carbon guide cylinder of a 32-inch single crystal silicon furnace, and then cooling to 25 ℃ to gelatinize the precursor on the surface of the carbon guide cylinder; the white gel formed is C₃N₆H₆·2H₃BO₃，M·2B；

Thirdly, preparing a film by high-temperature nitridation sintering:

drying the carbon guide cylinder with the precursor gelled on the surface in a drying oven at 110 ℃ for 12 hours, removing water, then placing in nitrogen for high-temperature sintering at 1400 ℃ for 2 hours, wherein the gel undergoes a chemical polycondensation reaction during sintering to form a crystalline boron nitride fiber and a film;

fourthly, repeating the operation of the second step and the operation of the third step once again to obtain the boron nitride fiber winding coating on the surface of the carbon-carbon guide cylinder.

The carbon-carbon guide cylinder with the boron nitride coating prepared by the embodiment has the advantages that the corrosion resistance is greatly improved, and the service life is prolonged from 200 furnaces/replacement to 250 furnaces/replacement.