阅读说明：本技术 一种高性能的碳碳坩埚表面涂层及其制备方法 (High-performance carbon-carbon crucible surface coating and preparation method thereof ) 是由 李陵 于 2021-10-09 设计创作，主要内容包括：本发明公开一种高性能的碳碳坩埚表面涂层及其制备方法,涉及碳基复合材料技术领域。本发明公开的高性能的碳碳坩埚表面涂层,主要通过先在碳碳坩埚的基底上先后沉积一层SiC过渡层和一层LaB-(6)/Y-(3)Al-(5)O-(12)外涂层,所述SiC过渡层采用多次包埋法沉积,所述LaB-(6)/Y-(3)Al-(5)O-(12)外涂层采用料浆法涂覆而成,且SiC过渡层通过有机硅浸渍剂浸渍处理后再涂刷外涂层浆料而成,本发明还公开了碳碳坩埚表面涂层的制备方法。本发明提供的碳碳坩埚表面涂层具有优异的高温强度、高温韧性和高耐磨性,并且抗热震性好、化学稳定性好,同时与碳碳基体具有较高的热膨胀相容性,显著提高了碳碳坩埚的使用寿命和耐损程度,且使碳碳坩埚能在1750℃下长期抗氧化使用。(The invention discloses a high-performance carbon-carbon crucible surface coating and a preparation method thereof, and relates to the technical field of carbon-based composite materials. The invention discloses a high-performance carbon-carbon crucible surface coating, which is mainly characterized in that a SiC transition layer and a LaB layer are deposited on a substrate of a carbon-carbon crucible in sequence 6 /Y 3 Al 5 O 12 An outer coating, the SiC transition layer being deposited by a multiple embedding method, the LaB 6 /Y 3 Al 5 O 12 The outer coating is formed by coating by adopting a slurry method, and the SiC transition layer is formed by dipping the SiC transition layer by using an organic silicon dipping agent and then coating the outer coating slurry. Carbon provided by the inventionThe carbon crucible surface coating has excellent high-temperature strength, high-temperature toughness and high wear resistance, and is good in thermal shock resistance and chemical stability, and meanwhile, the carbon crucible surface coating has high thermal expansion compatibility with a carbon matrix, so that the service life and the damage resistance of the carbon crucible are remarkably improved, and the carbon crucible can be used for long-term oxidation resistance at 1750 ℃.)

1. The high-performance carbon-carbon crucible surface coating is characterized in that a SiC transition layer and a LaB layer are deposited on a substrate of a carbon-carbon crucible in sequence₆/Y₃Al ₅O₁₂An outer coating, the SiC transition layer being deposited by an embedding method, the LaB₆/Y₃Al ₅O₁₂The outer coating is formed by coating by adopting a slurry method.

2. The high-performance carbon-carbon crucible surface coating according to claim 1, wherein the thickness of the SiC transition layer is 120-200 μm, and the LaB₆/Y₃Al₅O₁₂The thickness of the outer coating is 150-180 μm.

3. A preparation method of a high-performance carbon-carbon crucible surface coating is characterized by comprising the following steps:

(1) matrix pretreatment: placing the carbon-carbon crucible into a container configured with ethanol, placing the container into an ultrasonic cleaner for cleaning, performing ultrasonic treatment for 10-20 min, and repeatedly cleaning for 3 times to remove stains on the surface of the carbon-carbon crucible;

(2) mixing Si powder, C powder and B powder₂O₃Placing the powder in a ball mill, and performing ball milling for 15-20 hours to obtain uniform powder A; mixing Si powder, C powder and Al₂O₃Placing the powder in a ball mill, and performing ball milling for 15-20 h to obtain uniform powder B;

(3) placing the powder A in a graphite reaction device, and then embedding the pretreated carbon-carbon crucible into the powder A for primary embedding treatment; in an argon environment, raising the temperature to 2100-2200 ℃, reacting for 2-3 hours, and cooling to room temperature; embedding the carbon-carbon crucible after the primary embedding into the powder B for multiple times of embedding treatment;

(4) dipping the carbon-carbon crucible subjected to multiple embedding treatments in an organic silicon impregnant, dipping for 3-4 h at 90-100 ℃, filtering and drying to obtain a carbon-carbon crucible to be treated;

(5) preparation of external coating slurry: mixing B powder and La₂O₃Powder, Y₃Al ₅O₁₂Uniformly mixing the powder and Al powder according to a proper proportion, placing the mixture in a ball mill, carrying out ball milling for 12-24 h, and sieving the mixture by a 300-mesh sieve; and then mixing the obtained mixed powder with a binder and water, stirring the mixture into slurry by magnetic force, uniformly brushing the slurry on the surface of the carbon-carbon crucible to be treated by a material brush, drying the carbon-carbon crucible, and then placing the carbon-carbon crucible in a high-temperature hot-pressing furnace for heat treatment to obtain the required carbon-carbon crucible surface coating.

4. The method for preparing the high-performance carbon-carbon crucible surface coating according to claim 3, wherein the Si powder, the C powder and the B powder of the A powder in the step (2)₂O₃The powder mass ratio is (3.5-4.5): 1: (0.6-0.8).

5. The method for preparing the high-performance carbon-carbon crucible surface coating according to claim 3, wherein Si powder, C powder and Al powder of the B powder in the step (2)₂O₃The powder mass ratio is (3.5-4.5): 1: 1.

6. the method for preparing the surface coating of the high-performance carbon-carbon crucible according to claim 3, wherein the primary embedding process in the step (3) comprises the following steps: burying the pretreated carbon-carbon crucible into the powder A, raising the temperature to 2100-2200 ℃ in an argon atmosphere, reacting for 2-3 h, and then cooling to room temperature at a speed of 10-15 ℃/min.

7. The method for preparing the high-performance carbon-carbon crucible surface coating according to claim 3, wherein the multiple embedding treatment in the step (3) is to embed the carbon-carbon crucible which is embedded once into the powder B for one or more embedding treatments so as to obtain the SiC transition layer with the required thickness, and the embedding treatment process comprises the steps of embedding the carbon-carbon crucible which is embedded once into the powder B, raising the temperature to 1900-2000 ℃ in an argon atmosphere, reacting for 2-3 h, and cooling to room temperature at a rate of 8-10 ℃/min.

8. The method for preparing the high-performance carbon-carbon crucible surface coating according to claim 3, wherein in the step (5), the B powder and the La powder₂O₃Powder, Y₃Al ₅O₁₂The mass ratio of the powder to the Al powder is (1-2): (3-4): 1: (0.2-0.3).

9. The preparation method of the high-performance carbon-carbon crucible surface coating according to claim 3, wherein in the step (5), the mass of the binder is 3-5% of the mass of the mixed powder; the mass of the water is 1.5-3 times of the mass of the mixed powder.

10. The method for preparing the surface coating of the high-performance carbon-carbon crucible according to the claim 3, wherein in the step (5), the heat treatment process comprises the following steps: setting the pressure in the high-temperature hot-pressing furnace to be 10-15 MPa, heating to 150-200 ℃ at the speed of 3-5 ℃/min, and preserving heat for 1.5-2 h; then heating to 500-700 ℃ at the speed of 5-10 ℃/min, and preserving heat for 2-3 h; and then heating to 1500-1700 ℃ at the speed of 3-5 ℃/min, preserving the heat for 6-8 h, and naturally cooling to the room temperature.

Technical Field

The invention belongs to the technical field of carbon-based composite materials, and particularly relates to a high-performance carbon-carbon crucible surface coating and a preparation method thereof.

Background

With the enhancement of consciousness and strength of resource and environmental protection of governments and people in various countries, the development of the green and environment-friendly industry of solar energy in China is rapidly advanced, the number of single crystal silicon furnaces is rapidly increased from about 800 in 2000 to about 8000 at present, so that the demand of indispensable crucibles of the single crystal silicon furnaces is rapidly increased, and the rapid development of carbon/carbon composite material crucibles in the field of use of the single crystal silicon furnaces is driven. The carbon/carbon composite material crucible is a high-technology product processed by a composite material consisting of high-strength fibers and a carbon matrix, saves energy and materials greatly compared with graphite products, has excellent performance, long service life, high specific strength, high temperature resistance, corrosion resistance, small thermal expansion coefficient, rapid cooling and heating resistance, deformation resistance, no cracking and other excellent performances, and is an ideal upgraded product for replacing a single crystal furnace graphite crucible.

However, since the carbon fibers in the carbon/carbon composite crucible were not siliconized, some small discrete pits were visible on the surface of the crucible. The carbon fiber exposed on the surface is ground flat as the crucible is used, so that the pyrolysis carbon on the inner layer is siliconized again, and the carbon/carbon composite material is gradually thinned repeatedly, wherein the thinning speed is mainly determined by the structure of the pyrolysis carbon and the friction generated when the furnace is removed for cleaning. In order to solve the above problems, coating treatment is usually performed on the surface of the carbon/carbon composite material at present, and a more mature coating scheme is to coat a thin layer of SiC on the surface of the carbon/carbon composite material. The SiC material has high hardness, high thermal conductivity, good thermal shock resistance and high chemical stability, can have better thermal expansion compatibility with a carbon matrix, is an excellent high-temperature coating, can effectively improve the high-temperature strength, high-temperature oxidation resistance and high-temperature impact resistance of the carbon-carbon composite material, and prolongs the service life and the damage resistance of the carbon-carbon crucible.

In order to enable the carbon/carbon composite material surface coating to be used under higher temperature and more severe conditions, research and development personnel in various countries research and develop composite coatings to treat carbon/carbon composite materials, and SiC-Al is generally adopted₂O₃-mullite, SiC/Ar-Al-Si coating, Si-Mo coating, SiC-WSi₂/MoSi₂And the like. However, the SiO2 protective film formed by the current composite coating under the high-temperature oxidation environment can effectively block the penetration of oxygen, but the high-temperature oxidation resistance of the outer coating studied at present is not ideal along with the increase of the oxidation temperature and the extension of the oxidation time (the best available oxidation resistance temperature of the current composite coating is that1650 ℃), and the SiO2 generated by the inner coating has low viscosity and serious volatilization, and the surface of the protective film generates defects such as holes or air holes, thereby leading the coating to lose the oxidation protection capability.

Disclosure of Invention

The invention aims to provide a high-performance carbon-carbon crucible surface coating which has excellent high-temperature strength, high-temperature toughness and high wear resistance, good thermal shock resistance and good chemical stability, has high thermal expansion compatibility with a carbon-carbon matrix, obviously prolongs the service life and the damage resistance of the carbon-carbon crucible, and enables the carbon-carbon crucible to be used for long-term oxidation resistance at 1750 ℃.

In order to achieve the aim of the invention, the invention provides a high-performance carbon-carbon crucible surface coating which is mainly formed by depositing a SiC transition layer and a LaB layer on a substrate of a carbon-carbon crucible in sequence₆/Y₃Al₅O₁₂An outer coating, the SiC transition layer being deposited by an embedding method, the LaB₆/Y₃Al₅O₁₂The outer coating is formed by coating by adopting a slurry method.

The invention takes SiC as an inner coating, has small difference with the thermal expansion coefficient of a carbon-carbon crucible, has excellent high-temperature oxidation resistance and corrosion resistance, can prevent oxygen from permeating by SiO2 generated in a high-temperature oxidation environment, and adopts LaB₆/Y₃Al₅O₁₂The composite layer is used as an outer coating, namely LaB is coated outside the SiC transition layer₆And Y₃Al₅O₁₂The composite layer can improve the strength and high temperature resistance of the surface coating and reduce the oxygen permeability, thereby obviously improving the high-temperature service temperature of the carbon-carbon crucible, leading the carbon-carbon crucible to be capable of resisting oxidation for a long time at 1750 ℃, prolonging the service life of the carbon-carbon crucible and simultaneously leading the carbon-carbon crucible to have better and excellent mechanical strength and corrosion resistance.

Further, the thickness of the SiC transition layer is 120-200 mu m, and the LaB₆/Y₃Al₅O₁₂The thickness of the outer coating is 150-180 μm.

If the thickness of the SiC transition layer is less than 120 mu m, the surface coating is reducedThe high-temperature oxidation resistance of the layer ensures that the oxidation weight loss rate of the layer is higher at 1750 ℃, and oxygen cannot be effectively isolated for a long time; if the thickness is more than 200 μm, the oxidation resistance is not improved as the thickness is increased, and the cost is increased. LaB of the invention₆/Y₃Al₅O₁₂If the thickness of the outer coating is less than 150 microns, the carbon-carbon crucible cannot be effectively ensured to have oxidation resistance for a long time at a high temperature, and the thickness is low, so that SiO2 is easy to volatilize at a high temperature for a long time, and the high-temperature oxidation resistance and the service life of the carbon-carbon crucible are influenced; if the thickness is higher than 180 μm, the oxidation resistance and the SiC transition layer are not improved and protected better with the increase of the thickness, but the cost is increased.

The invention also provides a preparation method of the high-performance carbon-carbon crucible surface coating, which comprises the following steps:

(1) matrix pretreatment: and (3) placing the carbon-carbon crucible into a container configured with ethanol, placing the container into an ultrasonic cleaner for cleaning, carrying out ultrasonic treatment for 10-20 min, and repeatedly cleaning for 3 times to remove stains on the surface of the carbon-carbon crucible.

(2) Mixing Si powder, C powder and B powder₂O₃Placing the powder in a ball mill, and performing ball milling for 15-20 hours to obtain uniform powder A; mixing Si powder, C powder and Al₂O₃And placing the powder in a ball mill, and performing ball milling for 15-20 h to obtain uniform powder B.

(3) Placing the powder A in a graphite reaction device, and then embedding the pretreated carbon-carbon crucible into the powder A for primary embedding treatment; in an argon environment, raising the temperature to 2100-2200 ℃, reacting for 2-3 hours, and cooling to room temperature; and embedding the carbon-carbon crucible after the primary embedding into the powder B for multiple times of embedding treatment.

The invention adopts Si powder, C powder and B powder₂O₃The powder is used as material A to carry out primary embedding on a carbon-carbon crucible, and material B₂O₃The powder plays a certain role of catalyst to catalyze the reaction of Si and C, but the main purpose is to promote the penetration of Si powder and make the Si powder penetrate into the carbon-carbon matrix, thereby increasing the compatibility between the SiC transition layer and the carbon-carbon matrix, leading the SiC transition layer to be tightly combined with the carbon-carbon crucible and reducing the possibility of the Si powder being tightly combined with the carbon-carbon crucibleGaps and holes in the carbon-carbon composite material crystal are formed, so that the SiC coating is more compact. The invention adopts Si powder, C powder and Al₂O₃The powder is used as material B to carry out secondary embedding or multiple embedding on the carbon-carbon crucible, and Al₂O₃The powder mainly plays a role of a catalyst, catalyzes Si and C to react, reacts at an interface, enhances the bonding strength of the coating and the carbon-carbon matrix, and is embedded in the B in the process of high-temperature sintering for the first time₂O₃The powder has low melting point and good fluidity, and can further bring the powder into the pores of the embedded coating, so that the SiC coating is more compact, and the oxygen permeation under the high-temperature condition of the invention is reduced, therefore, the embedding process also improves the strength and the high-temperature oxidation resistance of the coating on the surface of the carbon-carbon crucible.

(4) And (3) dipping the carbon-carbon crucible subjected to multiple embedding treatments in an organic silicon impregnant, dipping for 3-4 h at 90-100 ℃, filtering and drying to obtain the carbon-carbon crucible to be treated.

The SiC transition layer obtained by the embedding method is compact, but the uniformity is not good, therefore, the invention adopts the organic silicon impregnant for treatment, the silane micromolecule structure in the impregnant can uniformly act on the SiC transition layer, the silane micromolecule structure has good affinity with the SiC transition layer, the silane micromolecule structure can easily permeate into the carbon-carbon base layer, the poor uniformity of the transition layer can be solved through high-temperature impregnation, the caking property between the transition layer and the outer coating, and between the transition layer and the carbon-carbon base layer can be improved, and the service life of the surface coating can be further prolonged.

(5) Preparation of external coating slurry: mixing B powder and La₂O₃Powder, Y₃Al₅O₁₂Uniformly mixing the powder and Al powder according to a proper proportion, placing the mixture in a ball mill, carrying out ball milling for 12-24 h, and sieving the mixture by a 300-mesh sieve; and then mixing the obtained mixed powder with a binder and water, stirring the mixture into slurry by magnetic force, uniformly brushing the slurry on the surface of the carbon-carbon crucible to be treated by a material brush, drying the carbon-carbon crucible, and then placing the carbon-carbon crucible in a high-temperature hot-pressing furnace for heat treatment to obtain the required carbon-carbon crucible surface coating.

B powder and La of the invention₂O₃The powder is put in a high-temperature hot-pressing furnace, under the action of Al powder,reaction to form LaB₆And is combined with Y₃Al₅O₁₂The powder generates LaB under the action of a binder₆/Y₃Al₅O₁₂And (4) coating. Yttrium aluminum garnet (Y) used in the present invention₃Al₅O₁₂) Has high melting point (1950 deg.C), thermal expansion coefficient similar to that of SiC, and good bonding force with transition layer, and the yttrium aluminum garnet and LaB₆The coating generated by the crystal under the action of high temperature has excellent high-temperature oxidation resistance, prolongs the service life of the carbon-carbon crucible, and can be used for a long time at 1750 ℃.

Further, Si powder, C powder and B powder of the powder A in the step (2)₂O₃The powder mass ratio is (3.5-4.5): 1: (0.6-0.8).

Further, Si powder, C powder and Al powder of the B powder in the step (2)₂O₃The powder mass ratio is (3.5-4.5): 1: 1.

further, the process of the primary embedding treatment in the step (3) is as follows: burying the pretreated carbon-carbon crucible into the powder A, raising the temperature to 2100-2200 ℃ in an argon atmosphere, reacting for 2-3 h, and then cooling to room temperature at a speed of 10-15 ℃/min.

Further, the multiple embedding treatment in the step (3) is to embed the carbon-carbon crucible which is embedded for one time into the powder B for one or more embedding treatments so as to obtain the SiC transition layer with the required thickness, and the embedding treatment process comprises the steps of embedding the carbon-carbon crucible which is embedded for one time into the powder B, raising the temperature to 1900-2000 ℃ in an argon atmosphere, reacting for 2-3 h, and cooling to room temperature at the speed of 8-10 ℃/min.

Further, in the step (5), the B powder and the La powder₂O₃Powder, Y₃Al₅O₁₂The mass ratio of the powder to the Al powder is (1-2): (3-4): 1: (0.2-0.3).

Further, in the step (5), the mass of the binder is 3-5% of the mass of the mixed powder; the mass of the water is 1.5-3 times of the mass of the mixed powder.

Further, in the step (5), the heat treatment process is as follows: setting the pressure in the high-temperature hot-pressing furnace to be 10-15 MPa, heating to 150-200 ℃ at the speed of 3-5 ℃/min, and preserving heat for 1.5-2 h; then heating to 500-700 ℃ at the speed of 5-10 ℃/min, and preserving heat for 2-3 h; and then heating to 1500-1700 ℃ at the speed of 3-5 ℃/min, preserving the heat for 6-8 h, and naturally cooling to the room temperature.

The invention adopts multi-stage heat treatment, and has the functions of: when the temperature is low at 150-200 ℃, the organic silicon impregnant can act on the transition layer and the outer coating, has good bonding effect, can effectively act on the two coatings, volatilizes water and gas at the low temperature, reduces the increase of pores under a rapid heating condition, improves the compactness of the surface coating, and reduces the occurrence of uneven distribution; in the process of 500-700 ℃, organic components are carbonized, so that the density of the surface coating can be further improved; in the sintering process at 1500-1700 ℃, LaB is obtained₆And Y₃Al₅O₁₂The crystals interact and fuse with each other and mutually permeate the transition layer, so that the binding force between the outer coating and the transition layer is improved, the porosity inside the surface coating is reduced, and the permeation of oxygen is reduced, thereby prolonging the service life of the carbon-carbon crucible and improving the high-temperature oxidation resistance.

The invention achieves the following beneficial effects:

1. the invention adopts SiC as a transition layer and LaB₆/Y₃Al₅O₁₂The composite layer is used as an outer coating, so that the binding force between the surface coating and the carbon-carbon crucible is obviously improved, and the high-temperature strength, the high-temperature oxidation resistance, the wear resistance, the shock resistance and the toughness of the surface coating are improved. The SiC transition layer is prepared by adopting a multiple embedding method, the preparation method is simple, the density of the transition layer can be improved, the porosity of the transition layer is reduced, the oxygen permeability is reduced, and the high-temperature service life is further prolonged. LaB₆/Y₃Al₅O₁₂The composite layer adopts high temperature resistant LaB₆And Y₃Al₅O₁₂The high-hardness high-temperature oxidation-resistant carbon crucible is prepared and combined with the two to ensure that the high-hardness high-temperature oxidation-resistant carbon crucible has the functions of being used as an outer coating of a carbon-carbon crucible, and the high-temperature oxidation-resistant carbon crucible has excellent high-temperature oxidation resistance and high strengthThe high-temperature application range of the carbon-carbon crucible is enlarged.

2. The invention adopts the organic silicon impregnant to carry out impregnation treatment on the SiC transition layer, improves the nonuniformity of the transition layer prepared by an embedding method, improves the binding force between the transition layer and the outer coating as well as between the transition layer and the carbon-carbon matrix, further improves the strength and toughness of the invention, and also prolongs the service life of the invention.

3. The invention adopts a multi-stage heat treatment method, reduces the porosity inside the surface coating, reduces the penetration of oxygen, and improves the service life and the high-temperature oxidation resistance of the carbon-carbon crucible.

4. The surface coating is prepared by compounding an embedding method and a slurry method, the embedding method is used for preparing the transition layer, and then the slurry method is used for coating the outer coating slurry on the transition layer.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The organic silicon impregnant used in the invention is provided by Qingdao Zonengda architecture science and technology limited company.

The surface coating of the high performance carbon-carbon crucible of the present invention will be described with reference to the following examples.

Example 1

The surface coating of the carbon-carbon crucible provided in the embodiment is composed of a SiC transition layer and LaB₆/Y₃Al₅O₁₂An outer coating, which is to deposit a SiC transition layer on the surface of a carbon-carbon crucible by an embedding method and then coat LaB by a slurry method₆/Y₃Al₅O₁₂And (4) an outer coating. The preparation method of the carbon-carbon crucible surface coating comprises the following steps:

(1) matrix pretreatment: and (3) placing the carbon-carbon crucible into a container with ethanol, placing the container into an ultrasonic cleaner for cleaning, carrying out ultrasonic treatment for 15min, and repeatedly cleaning for 3 times to remove stains on the surface of the carbon-carbon crucible.

(2) Mixing Si powder, C powder and B powder₂O₃Placing the powder in a ball mill, ball-milling for 18 hours at a ball-milling speed of 600r/min by taking deionized water as a medium, and drying to obtain uniform powder A; mixing Si powder, C powder and Al₂O₃Putting the powder into a ball mill, wherein the ball milling speed is 600r/min, and ball milling is carried out for 18h by taking deionized water as a medium to obtain uniform powder B.

(3) Placing the powder A into a graphite reaction device, then embedding the pretreated carbon-carbon crucible into the powder A, raising the temperature to 2200 ℃ in the argon atmosphere, reacting for 3h, and then cooling to room temperature at the speed of 10 ℃/min. And embedding the carbon-carbon crucible after the primary embedding into the powder B, raising the temperature to 2000 ℃ in an argon atmosphere, reacting for 3h, and then cooling to room temperature at the speed of 10 ℃/min. And embedding the embedded carbon-carbon crucible into the powder B by the same method for embedding again.

(4) And (3) dipping the carbon-carbon crucible after the three times of embedding treatment in an organic silicon impregnant, dipping for 4 hours at 90 ℃, filtering and drying to obtain the carbon-carbon crucible to be treated.

(5) Preparation of external coating slurry: mixing B powder and La₂O₃Powder, Y₃Al₅O₁₂Uniformly mixing the powder and Al powder according to a proper proportion, placing the mixture in a ball mill, ball-milling for 24 hours at a ball-milling speed of 800r/min by taking deionized water as a medium, drying, and sieving by a 300-mesh sieve to obtain mixed powder; and then mixing the mixed powder with a binder and deionized water, stirring the mixture into slurry by magnetic force, uniformly coating the slurry on the surface of the carbon-carbon crucible to be treated by a material brush, drying the carbon-carbon crucible in a drying oven at 90 ℃ for 3 hours, and then placing the carbon-carbon crucible in a high-temperature hot pressing furnace for heat treatment to obtain the required carbon-carbon crucible surface coating.

In this example, Si powder, C powder and B powder of A powder₂O₃The powder mass ratio is 3.5: 1: 0.6.

in this example, Si powder, C powder and Al powder of B powder₂O₃The powder mass ratio is 3.5: 1: 1.

in this example, B powder and La powder₂O₃Powder, Y₃Al₅O₁₂The mass ratio of the powder to the Al powder is 1: 3: 1: 0.2.

in step (5) of this example, the binder used was polyvinyl butyral, the mass of the binder used was 3% of the mass of the mixed powder, and the mass of deionized water used was 1.5 times the mass of the mixed powder.

The heat treatment process of step (5) in this embodiment is: setting the pressure in the high-temperature hot-pressing furnace to 10MPa, heating to 200 ℃ at the speed of 3 ℃/min, and preserving heat for 1.5 h; then heating to 700 ℃ at the speed of 5 ℃/min, and preserving heat for 2 h; then heating to 1700 ℃ at the speed of 3 ℃/min, preserving the heat for 6h, and naturally cooling to the room temperature.

Example 2

The composition, formulation and preparation method of the carbon-carbon crucible surface coating provided in this example are the same as in example 1, except as follows:

in this example, Si powder, C powder and B powder of A powder₂O₃The powder mass ratio is 4.5: 1: 0.8.

in this example, Si powder, C powder and Al powder of B powder₂O₃The powder mass ratio is 4.5: 1: 1.

in this example, B powder and La powder₂O₃Powder, Y₃Al₅O₁₂The mass ratio of the powder to the Al powder is 2: 4: 1: 0.3.

in step (5) of this example, the binder used was polyvinyl butyral, the mass of the binder used was 5% of the mass of the mixed powder, and the mass of deionized water used was 3 times the mass of the mixed powder.

The heat treatment process of step (5) in this embodiment is: setting the pressure in the high-temperature hot-pressing furnace to be 15MPa, heating to 150 ℃ at the speed of 5 ℃/min, and preserving heat for 2 h; then heating to 500 ℃ at the speed of 10 ℃/min, and preserving heat for 3 h; then the temperature is raised to 1500 ℃ at the speed of 5 ℃/min, the temperature is kept for 8h, and the temperature is naturally cooled to the room temperature.

Example 3

The composition, formulation and preparation method of the carbon-carbon crucible surface coating provided in this example are the same as in example 1, except as follows:

in this example, Si powder, C powder and B powder of A powder₂O₃The powder mass ratio is 4: 1: 0.7.

in this example, Si powder, C powder and Al powder of B powder₂O₃The powder mass ratio is 4: 1: 1.

in this example, B powder and La powder₂O₃Powder, Y₃Al₅O₁₂The mass ratio of the powder to the Al powder is 1: 4: 1: 0.2.

in step (5) of this example, the binder used was polyvinyl butyral, the mass of the binder used was 4% of the mass of the mixed powder, and the mass of deionized water used was 2 times the mass of the mixed powder.

The heat treatment process of step (5) in this embodiment is: setting the pressure in the high-temperature hot-pressing furnace to be 12MPa, heating to 180 ℃ at the speed of 4 ℃/min, and preserving heat for 2 h; then heating to 600 ℃ at the speed of 8 ℃/min, and preserving heat for 3 h; then heating to 1600 ℃ at the speed of 4 ℃/min, preserving the heat for 7h, and naturally cooling to room temperature.

Example 3

The composition, formulation and preparation method of the carbon-carbon crucible surface coating provided in this example are the same as in example 1, except as follows:

in this example, Si powder, C powder and B powder of A powder₂O₃The powder mass ratio is 4.5: 1: 0.6.

in this example, Si powder, C powder and Al powder of B powder₂O₃The powder mass ratio is 4.2: 1: 1.

in this example, B powder and La powder₂O₃Powder, Y₃Al₅O₁₂The mass ratio of the powder to the Al powder is 1.5: 4: 1: 0.2.

in step (5) of this example, the binder used was polyvinyl butyral, the mass of the binder used was 5% of the mass of the mixed powder, and the mass of deionized water used was 2.5 times the mass of the mixed powder.

The heat treatment process of step (5) in this embodiment is: setting the pressure in the high-temperature hot-pressing furnace to be 15MPa, heating to 180 ℃ at the speed of 5 ℃/min, and preserving heat for 2 h; then heating to 700 ℃ at the speed of 5 ℃/min, and preserving heat for 3 h; then heating to 1700 ℃ at the speed of 3 ℃/min, preserving the heat for 6h, and naturally cooling to the room temperature.

Comparative example 1

A carbon-carbon crucible surface coating has the same composition, raw materials and preparation method as those of example 4, except that in this comparative example, the material A is not used for embedding the carbon-carbon crucible, and only the material B is used for embedding the carbon-carbon crucible three times, so that the thickness of the SiC transition layer is the same as that of the SiC transition layer in example 4.

Comparative example 2

A carbon-carbon crucible top coating was prepared in the same manner as in example 4 except that no impregnation treatment was performed on the carbon-carbon crucible with an organosilicon impregnant.

Comparative example 3

A carbon-carbon crucible surface coating was prepared in the same manner as in example 4 except that the surface coating in this comparative example was a SiC coating, i.e., no treatment with an organosilicon impregnant and no outer coating, and only the surface of the carbon-carbon crucible was subjected to a SiC embedding treatment.

Comparative example 4

A carbon-carbon crucible top coating was prepared in the same manner as in example 4 except that Y was not added to the top coating material in this comparative example₃Al₅O₁₂And (3) pulverizing.

Comparative example 5

A carbon-carbon crucible top coating having the same composition, raw materials and preparation method as in example 4, except that the heat treatment process of this comparative example was: setting the pressure in the high-temperature hot-pressing furnace to be 15MPa, heating to 1700 ℃ at the speed of 10 ℃/min, preserving the heat for 8h, and naturally cooling to the room temperature.

It is noted that, in the present invention, it is preferable that the thickness of the SiC transition layer is 120 to 200 μm, and LaB₆/Y₃Al₅O₁₂The thickness of the outer coating is 150-180 μm. In addition, the thickness of the outer coating in the inventive example and the comparative example is 170 + -2 μm, and the thickness of the SiC transition layer is 150 + -2 μm.

The surface coatings of the carbon-carbon crucibles prepared in the above examples 1 to 4 and comparative examples 1 to 5 were tested for compactness, bending strength, and fracture toughness, and the results are shown in table 1.

TABLE 1 results of mechanical property measurements of carbon-carbon crucible surface coatings

	Density (%)	Flexural Strength (MPa)	Fracture toughness (MPa. m)1/2)
				Example 1	96.3	709	5.2
Example 2	95.4	696	4.6
				Example 3	95.8	715	5.3
Example 4	96.5	728	5.1
				Comparative example 1	91.5	658	4.1
Comparative example 2	93.7	652	3.5
				Comparative example 3	89.8	478	2.9
Comparative example 4	93.2	603	3.8
				Comparative example 5	90.2	583	3.2

According to the comparative experiment results in table 1 of examples 1-4 and comparative examples 1-5, it can be seen that the compactness of the coating of the invention is high, the bending strength and fracture toughness are high, that is, the compactness and mechanical properties of the coating of the surface main are good, and the influence of the embedding method, the organosilicon impregnant, the components of the outer coating and the heat treatment mode on the compactness and mechanical properties is large.

The surface coatings of the carbon-carbon crucibles prepared in the above examples 1 to 4 and comparative examples 1 to 5 were tested for hardness, friction resistance, mechanical properties and high-temperature oxidation resistance, and the test results are shown in table 2.

Hardness: the surface hardness was measured by using a Vickers hardness tester model HV-1000 with a test force of 100gf, a square pyramid diamond indenter, and 6 points at different positions were randomly detected, and the average of the values from which a maximum value and a minimum value were removed was taken as the surface hardness.

And (3) friction resistance: and (3) detecting by a high-temperature friction and wear tester, wherein the load is 20N, and the counter friction ball is SiC under the dry grinding condition.

The high-temperature oxidation resistance test method comprises the following steps: the oxidation experiments of the coatings were carried out in static air in a high temperature tube furnace, the carbon-carbon crucible samples with the coatings being placed in a corundum crucible, which was then placed in the tube furnace which had reached the set temperature. And taking the crucible out at intervals, cooling, weighing the weight of the sample, putting the crucible back into the tubular furnace, and repeating the steps until the preset experimental time is reached. The weight loss ratio (weight of the original sample-weight of the sample after the high-temperature treatment)/weight of the original sample × 100%, wherein both the weight of the original sample and the weight of the sample refer to the weight of the surface coating.

TABLE 2 results of other Properties of the carbon-carbon crucible surface coating

From the results of the comparative experiments in Table 2 of examples 1 to 4 and comparative examples 1 to 5 above, it can be seen that the present invention has excellent high-temperature oxidation resistance and can be used at 1750 ℃ for a long period of time, and the embedding method, the silicone impregnant, the components of the outer coating layer, and the heat treatment manner have a large influence on the high-temperature oxidation resistance of the coating layer of the present invention.

The technical features of the embodiments described above can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.