A method for manufacturing a carbon ceramic heater and a carbon ceramic heater manufactured thereby

Abstract

The application relates to the field of carbon ceramic composite materials, and particularly discloses a preparation method of a carbon ceramic heater and the carbon ceramic heater prepared by the method. The preparation method comprises the following steps: S1, mixing and stirring short-cut carbon fibers, a dispersing agent, a binder, ceramic powder and liquid phenolic resin to prepare a raw slurry mixture; S2, molding and heating and curing the raw slurry mixture to prepare a preformed body; S3, performing carbonization treatment on the preformed body in the step S2 to obtain a preform; S4, performing densification treatment and graphitization treatment on the preform obtained in the step S3 in sequence, and then performing machining to obtain the carbon ceramic heater. The application also discloses the carbon ceramic heater prepared by the above method. The application has the characteristics of improving the resistance stability of the heater prepared by the carbon ceramic composite material.

Description

Technical Field

[0001] This application relates to the field of carbon-ceramic composite materials, and more specifically, it relates to a method for preparing a carbon-ceramic heater and the resulting carbon-ceramic heater. Background Technology

[0002] The thermal field of a Czochralski silicon single crystal furnace refers to the entire temperature field system used to melt silicon material and maintain it at a certain temperature for single crystal growth. Based on the function of each part, it can be roughly divided into a heating system, a heat transfer and support system, a flow guiding system, and a heat preservation system. The heater in the single crystal furnace is the heat source of the furnace, and the raw material is mainly isostatically pressed graphite.

[0003] Currently, with the continuous upgrading and expansion of hot zone size, the preparation of raw materials for large-size isostatic pressing graphite heaters is limited by isostatic pressing equipment, and the molding and calcination processes are quite difficult, resulting in large-size graphite heaters being difficult to mold and expensive. Therefore, some manufacturers use a 2- or 4-segment splicing scheme to manufacture graphite heaters. However, although heaters made with this scheme reduce manufacturing costs, problems such as easy corrosion and sparking at the splicing gaps remain unresolved, generally resulting in a very short service life.

[0004] Currently, some literature indicates the use of C / C-SiC carbon-ceramic composites to prepare heaters. Carbon / ceramic composites are a general term for composite materials that use carbon fibers, ceramic fibers, and other materials as reinforcing phases, and ceramics such as quartz, feldspar, and silicon carbide as the matrix phase. Generally, a C / C preform with a certain porosity is first prepared using relatively mature processes such as chemical vapor deposition (CVD) or resin impregnation / pyrolysis, and then a SiC matrix is ​​introduced to replace part of the C matrix using other methods.

[0005] However, when carbon-ceramic composite materials are directly used in heaters for monocrystalline silicon furnaces, it is found that the resulting heaters have poor resistance stability and excessive current fluctuations during heating, which can easily cause local heat accumulation and affect the production quality and efficiency of monocrystalline silicon. Therefore, it is of great significance to develop heaters with better resistance stability for the use of carbon-ceramic composite materials in monocrystalline silicon production. Summary of the Invention

[0006] To improve the resistance stability of heaters made from carbon-ceramic composite materials, this application provides a method for preparing a carbon-ceramic heater and the resulting carbon-ceramic heater.

[0007] In a first aspect, this application provides a method for preparing a carbon ceramic heater, which adopts the following technical solution:

[0008] A method for preparing a carbon ceramic heater includes the following steps:

[0009] S1. Short-cut carbon fibers, dispersant, binder, ceramic powder and liquid phenolic resin are mixed and stirred to prepare the original slurry mixture;

[0010] S2. The original slurry mixture is molded, heated and cured to obtain a preform;

[0011] S3. Carbonize the preform from step S2 to obtain a preform blank.

[0012] S4. The preform obtained in step S3 is subjected to densification treatment and graphitization treatment in sequence, and then machined to obtain a carbon ceramic heater.

[0013] By adopting the above technical solution, when preparing carbon ceramic heaters using traditional carbon-carbon composite preforms, the preforms are basically made by alternating layers of mesh and carbon cloth and needle punching. After the carbon-carbon composite preforms are prepared into finished heaters, the texture, density, and porosity of the fibers on each grooved heating strip are different. The carbon fiber characteristics on each heating strip are different, and the resistance value is different, resulting in poor resistance stability and excessive current fluctuations during the heating process.

[0014] Therefore, in this application, short-cut carbon fibers and ceramic powder are used as raw materials to make a carbon-ceramic heater. With the help of a dispersant, the short-cut carbon fibers and ceramic powder are evenly distributed and dispersed in liquid phenolic resin. After molding and heating to cure, the carbon fibers in the resulting molded body are evenly dispersed in the form of short fibers. The carbon fibers are evenly distributed in the heater and have no obvious directionality. This makes the resistivity of the heater highly stable during the heating process and less likely to cause local heat accumulation, thus significantly improving the resistance stability of the carbon-ceramic heater.

[0015] Optionally, the dispersant is selected from one or more of sodium dodecylbenzenesulfonate, polyacrylamide, Tween 80, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and Triton.

[0016] By adopting the above technical solution, when the above-mentioned dispersant is selected in this application, the liquid-solid interfacial tension of the carbon fiber and ceramic powder dispersion system can be improved, the dispersibility between carbon fiber and ceramic powder can be enhanced, and the carbon fiber and ceramic powder can be evenly distributed in the phenolic resin to prevent their aggregation. This prevents the mutual attraction and agglomeration between carbon fibers, ceramic powders, and carbon fibers and ceramic powders, thereby achieving a uniform particle distribution of carbon fibers and ceramic powders in the phenolic resin, which helps to improve the resistivity stability of the final carbon ceramic heater.

[0017] Optionally, the dispersant may be a mixture of hydroxyethyl cellulose and Triton.

[0018] By adopting the above technical solution, the dispersion system in this application not only needs to consider the dispersibility of carbon fiber in liquid phenolic resin, but also the uniform dispersion of ceramic powder in the short carbon fiber-liquid phenolic resin system. When the above dispersant mixture system is selected, the overall dispersion effect of short carbon fiber and ceramic powder in liquid phenolic resin system is better, and the resistivity stability of the carbon ceramic heater is better.

[0019] Optionally, the liquid phenolic resin may be a water-soluble liquid phenolic resin or an alcohol-soluble phenolic resin, and more preferably a water-soluble phenolic resin.

[0020] By adopting the above technical solution, water-soluble phenolic resin is selected as the liquid phenolic resin, which is easier to mix with chopped carbon fibers, ceramic powder and other solids to form a uniform dispersion system. This helps to obtain uniform preforms and preforms in subsequent steps. Moreover, water-soluble liquid phenolic resin has excellent bonding properties, which can firmly bond chopped carbon fibers, ceramic powder and other solid particles together to form a dense composite material structure. Finally, the carbon-ceramic heater has a uniform distribution of carbon fibers and higher resistivity stability. In addition, the overall porosity of the heater is low and uniform, and silicon vapor is not easy to enter the pores and cause corrosion and resistance changes during use.

[0021] Optionally, in step S1, the short-cut carbon fibers and ceramic powder are premixed before being added to water-soluble liquid phenolic resin for mixing and stirring.

[0022] By adopting the above technical solution, either by adding ceramic powder to liquid phenolic resin first and then adding short-cut carbon fibers, or by adding short-cut carbon fibers to liquid phenolic resin first and then adding ceramic powder, the later-added substances will be affected by the substances already dispersed in the resin, resulting in poor dispersibility. It was found that when the short-cut carbon fibers and ceramic powder are premixed before being added to liquid phenolic resin, the final system dispersion effect is better, and the resistivity stability of the carbon ceramic heater is better.

[0023] Optionally, the short-cut carbon fibers and ceramic powder are premixed to obtain a premix, which is then modified and added to a water-soluble liquid phenolic resin. The modification process includes the following steps:

[0024] The premix is ​​first treated with acid and then soaked in a water-soluble weakly polar solvent to obtain a modified premix. The modified premix is ​​then added to a water-soluble liquid phenolic resin.

[0025] Among them, the water-soluble weakly polar solvents include benzyl alcohol and phenol in a mass ratio of 1:(0.8-1.2).

[0026] Optionally, the specific operations for premix modification treatment are as follows:

[0027] The premix was acidified and stirred in a 3-5% sulfuric acid solution for 20-30 minutes, filtered, washed and dried, then soaked in a weakly polar solvent and treated at 50-60℃ for 40-60 minutes, filtered and dried to obtain the modified premix.

[0028] By adopting the above technical solution, the premix obtained by mixing chopped carbon fibers and ceramic powder is first acid-treated to increase its surface polarity, thereby improving the wettability of chopped carbon fibers and ceramic powder in water-soluble liquid phenolic resin. Better wettability helps reduce particle agglomeration and improves dispersion in water-soluble liquid phenolic resin. Then, it is immersed in a water-soluble weakly polar solvent of benzyl alcohol and phenol to further improve the dispersion uniformity of chopped carbon fibers and ceramic powder in water-soluble liquid phenolic resin. Moreover, when it coats the surface of chopped carbon fibers and ceramic powder, benzene ring groups and hydroxyl groups are introduced on the surface. These groups form hydrogen bonds and π-π conjugation with the functional groups in hydroxyethyl cellulose and Triton (polyoxyethylene-8-octylphenyl ether), further improving the dispersion effect and the heat resistance of the dispersion system. This allows the slurry mixture to play an excellent dispersion role during molding and heating curing, and ultimately further improves the resistivity stability of the carbon ceramic heater.

[0029] Optionally, in step S1, the mass ratio of chopped carbon fiber, dispersant, binder, ceramic powder and liquid phenolic resin is 1:(0.01-0.05):(0.01-0.03):(1-3):(5-15).

[0030] Optionally, the adhesive may be selected from one or more of polyacrylamide, soluble starch, and polyvinyl alcohol.

[0031] Optionally, the ceramic powder may be selected from one or more of silicon carbide, silicon nitride, and silicon powder.

[0032] By adopting the above technical solution, the ceramic powder is made of the silicon-containing material and combined with carbon fiber to obtain a carbon ceramic heater. Moreover, the overall porosity of the heater blank is low and uniform. During the crystal pulling process, silicon vapor does not easily enter the pores and cause corrosion, resulting in changes in resistance.

[0033] Optionally, in step S2, the heating and curing temperature is 150-200℃, the curing time is 5-12h, and the molding pressure is 3-10MPa;

[0034] In step S3, the carbonization process is carried out in a nitrogen atmosphere, with a carbonization temperature of 900-1200℃ and a carbonization time of 2-5 hours.

[0035] In step S4, the graphitization temperature is 2000-2400℃.

[0036] Optionally, in step S4, the densification process is achieved by vapor deposition under a pressure of 2000-4000 Pa. The gas used for vapor deposition is one or more carbon source gases selected from methane, propane, or propylene. The vapor deposition temperature is 900-1200℃ and the deposition time is 100-500h.

[0037] Or / and, the densification treatment is obtained by impregnation and curing in acetal resin or furan resin followed by carbonization treatment, with an impregnation temperature of 40-60℃, an impregnation pressure of 1-3MPa, a curing temperature of 150-200℃, and a carbonization temperature of 900-1200℃.

[0038] By adopting the above technical solutions, when densifying the preform, vapor deposition or resin impregnation carbonization can be directly used, or vapor deposition can be performed first and then resin impregnation carbonization can be performed. Through the molding and densification process, carbon / ceramic (C / C-SiC) composite materials are formed, thereby making the carbon-ceramic composite material more dense and improving its performance.

[0039] Optionally, in step S4, after machining the preform, a silicon carbide coating is deposited on the surface of the preform by chemical vapor deposition. The gas source for chemical vapor deposition of the coating is trichloromethylsilane, hydrogen is used as a carrier, and nitrogen or argon is used as a dilution gas. The deposition is carried out at a furnace pressure of 2000-4000 Pa for 100-300 h, and the deposition temperature is 1000-1200℃.

[0040] By adopting the above technical solution, the preform in this application forms a carbon-ceramic composite material during the molding and densification process. After machining, the surface of the preform is then subjected to vapor deposition using trichloromethylsilane as the gas source to form a silicon carbide coating. This coating has a thermal expansion coefficient that is closer to that of the carbon-ceramic preform, resulting in superior performance in terms of thermal shock resistance and surface densification. This effectively solves the problem of corrosion resistance to silicon vapor in the crystal pulling hot zone and improves the service life of the carbon-ceramic heater.

[0041] Secondly, this application provides a carbon ceramic heater, which adopts the following technical solution:

[0042] A carbon ceramic heater is prepared by the method described above.

[0043] By adopting the above technical solution, the carbon-ceramic heater prepared by the method of this application solves the problem of poor resistance uniformity and stability of heaters prepared by C / C-SiC carbon-ceramic composite materials. While obtaining a carbon-ceramic heater with better resistance stability, the overall porosity of the heater is lower and more uniform. During use, silicon vapor is less likely to enter the pores and cause corrosion, resulting in resistance changes. Moreover, the silicon carbide coating on the surface of the final blank has a thermal expansion coefficient that is closer to that of the carbon-ceramic blank, which is superior in terms of thermal shock resistance and product surface densification, and effectively solves the corrosion problem in the thermal field.

[0044] In summary, this application has the following beneficial effects:

[0045] 1. In this application, a carbon-ceramic heater is made using chopped carbon fibers and ceramic powder as raw materials. With the help of a dispersant, the chopped carbon fibers and ceramic powder are evenly distributed and dispersed in liquid phenolic resin. After molding and heating to cure, the carbon fibers in the resulting molded body are evenly dispersed in the form of short fibers. The carbon fibers are evenly distributed in the heater and have no obvious directionality. This makes the resistivity of the heater highly stable during the heating process and less likely to cause local heat accumulation. Ultimately, this significantly improves the resistance stability of the carbon-ceramic heater.

[0046] 2. The carbon-ceramic heater prepared by the method of this application solves the problem of poor resistance uniformity and stability of heaters prepared by C / C-SiC carbon-ceramic composite materials. While obtaining a carbon-ceramic heater with better resistance stability, the overall porosity of the heater is lower and more uniform. During use, silicon vapor is less likely to enter the pores and cause corrosion, resulting in resistance changes. Moreover, the silicon carbide coating on the surface of the final blank has a thermal expansion coefficient that is closer to that of the carbon-ceramic blank, which is superior in terms of thermal shock resistance and product surface densification, and effectively solves the corrosion problem in the thermal field. Detailed Implementation

[0047] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0048] The water-soluble liquid phenolic resin used in the following preparation examples and embodiments is the liquid phenolic resin (water-soluble) from Jinan Dahui Chemical Technology Co., Ltd., CAS No. 9003-35-4;

[0049] The acetophenol-formaldehyde resin model is CYPF9300;

[0050] The short-cut carbon fiber is T700 or K12 short-cut carbon fiber with a fiber length of 10-30mm;

[0051] Example 1

[0052] A method for preparing a carbon ceramic heater includes the following steps:

[0053] S1. T700 short-cut carbon fiber, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin are used as raw materials and are thoroughly mixed and stirred in a mass ratio of 1:0.03:0.02:2:10 to obtain the original slurry mixture;

[0054] The dispersant is a mixture of hydroxyethyl cellulose and Triton X-100 in a mass ratio of 1:1, the binder is polyvinyl alcohol, and the ceramic powder is silicon nitride.

[0055] S2. Pour the raw slurry mixture into a mold, filter, press, heat and cure to obtain a preform. The heating and curing temperature is 180℃, the curing time is 8h, and the molding pressure is 5MPa.

[0056] S3. The preform from step S2 is carbonized in a nitrogen atmosphere at a carbonization temperature of 1000℃ for 3 hours to obtain a preform.

[0057] S4. The preform obtained in step S3 is subjected to densification treatment and graphitization treatment in sequence, and then machined to obtain a carbon ceramic heater.

[0058] The specific operation of the densification treatment in step S4 is as follows: the preform obtained in step S3 is first subjected to vapor phase deposition with methane as the carbon source gas and a pressure of 3000 Pa. The deposition temperature is 1100℃ and the deposition time is 300h. Then, the preform after vapor phase deposition densification is impregnated and cured in furan resin at a temperature of 50℃, an impregnation pressure of 2MPa, and an impregnation time of 4h. Then, it is heated and cured at 180℃ for 3h. Finally, it is carbonized at a carbonization temperature of 1100℃ and a carbonization time of 8h to obtain the densified preform.

[0059] The densified preform was then graphitized at 2200℃ for 3 hours to obtain a carbon ceramic preform. This preform was then machined according to resistance requirements to obtain a primary carbon ceramic heater with a density of 1.9 g / cm³. 3 The porosity is 5% and the resistivity is 20 μΩ·m;

[0060] Then, the primary carbon ceramic heater is placed in a silicon carbide deposition furnace. Hydrogen is used as a carrier gas to bring trichloromethylsilane into the deposition furnace, and nitrogen is used as a dilution gas to stabilize the furnace pressure at 3000 Pa. Deposition is carried out under this furnace pressure for 200 hours at a deposition temperature of 1100℃. A silicon carbide coating is chemically deposited on the surface of the primary carbon ceramic heater, and the finished carbon ceramic heater is obtained.

[0061] Example 2

[0062] A method for preparing a carbon ceramic heater includes the following steps:

[0063] S1. T700 short-cut carbon fiber, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin are used as raw materials and are thoroughly mixed and stirred in a mass ratio of 1:0.01:0.01:1:5 to obtain the original slurry mixture;

[0064] The dispersant is a mixture of hydroxyethyl cellulose and Triton X-100 in a mass ratio of 1:0.8, the binder is polyacrylamide, and the ceramic powder is silicon carbide.

[0065] S2. Pour the raw slurry mixture into a mold, filter, press, heat and cure to obtain a preform. The heating and curing temperature is 150℃, the curing time is 12h, and the molding pressure is 3MPa.

[0066] S3. The preform from step S2 is carbonized in a nitrogen atmosphere at a carbonization temperature of 900℃ for 5 hours to obtain a preform.

[0067] S4. The preform obtained in step S3 is subjected to densification treatment and graphitization treatment in sequence, and then machined to obtain a carbon ceramic heater.

[0068] The densification process in step S4 is specifically performed as follows: the preform obtained in step S3 is impregnated and cured in acetal resin at an impregnation temperature of 40°C, an impregnation pressure of 1 MPa, and an impregnation time of 3 hours. Then, it is heated and cured at 150°C for 4 hours, and then carbonized at a carbonization temperature of 900°C and a carbonization time of 10 hours to obtain the densified preform.

[0069] The densified preform was then graphitized at 2000℃ for 5 hours to obtain a carbon ceramic preform. This preform was then machined according to resistance requirements to obtain a primary carbon ceramic heater with a density of 2.3 g / cm³. 3 The porosity is 2% and the resistivity is 15 μΩ·m;

[0070] Then, the primary carbon ceramic heater is placed in a silicon carbide deposition furnace. Hydrogen is used as a carrier gas to bring trichloromethylsilane into the deposition furnace, and nitrogen is used as a dilution gas to stabilize the furnace pressure at 2000 Pa. Deposition is carried out under this furnace pressure for 300 hours at a deposition temperature of 1000℃. A silicon carbide coating is chemically deposited on the surface of the primary carbon ceramic heater, and the finished carbon ceramic heater is obtained.

[0071] Example 3

[0072] A method for preparing a carbon ceramic heater includes the following steps:

[0073] S1. T700 short-cut carbon fiber, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin are used as raw materials and are thoroughly mixed and stirred in a mass ratio of 1:0.05:0.03:3:15 to obtain the original slurry mixture;

[0074] The dispersant is a mixture of hydroxyethyl cellulose and Triton X-100 in a mass ratio of 1:1.2, the binder is polyvinyl alcohol, and the ceramic powder is silica powder.

[0075] S2. Pour the raw slurry mixture into a mold, filter, press, heat and cure to obtain a preform. The heating and curing temperature is 200℃, the curing time is 5h, and the molding pressure is 10MPa.

[0076] S3. The preform from step S2 is carbonized in a nitrogen atmosphere at a carbonization temperature of 1200℃ for 2 hours to obtain a preform.

[0077] S4. The preform obtained in step S3 is subjected to densification treatment and graphitization treatment in sequence, and then machined to obtain a carbon ceramic heater.

[0078] The densification process in step S4 is specifically performed as follows: the preform obtained in step S3 is first subjected to vapor deposition at a pressure of 4000 Pa using propylene as the carbon source gas, at a deposition temperature of 1200℃ and a deposition time of 100 h. Then, the preform after vapor deposition densification is heated and cured at 200℃ for 2 h, and then carbonized at a carbonization temperature of 1200℃ and a carbonization time of 6 h to obtain the densified preform.

[0079] The densified preform was then graphitized at 2400℃ for 2 hours to obtain a carbon ceramic preform. This preform was then machined according to resistance requirements to obtain a primary carbon ceramic heater with a density of 2.3 g / cm³. 3 The porosity is 8% and the resistivity is 25 μΩ·m;

[0080] Then, the primary carbon ceramic heater is placed in a silicon carbide deposition furnace. Hydrogen is used as a carrier gas to bring trichloromethylsilane into the deposition furnace, and nitrogen is used as a dilution gas to stabilize the furnace pressure at 4000 Pa. Deposition is carried out under this furnace pressure for 100 hours at a deposition temperature of 1200℃. A silicon carbide coating is chemically deposited on the surface of the primary carbon ceramic heater, and the finished carbon ceramic heater is obtained.

[0081] Example 4

[0082] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that silicon powder is used as the ceramic powder.

[0083] Example 5

[0084] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that silicon carbide is used as the ceramic powder.

[0085] Example 6

[0086] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that in step S1, the short-cut carbon fibers and ceramic powder are premixed and then added to water-soluble liquid phenolic resin and mixed with dispersant and binder.

[0087] Example 7

[0088] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that hydroxyethyl cellulose is used as the dispersant in step S1.

[0089] Example 8

[0090] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that the dispersant in step S1 is Triton X-100.

[0091] Example 9

[0092] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that sodium dodecylbenzenesulfonate is used as the dispersant in step S1.

[0093] Example 10

[0094] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that the dispersant in step S1 is a mixture of carboxymethyl cellulose and Triton X-100 in a mass ratio of 1:1.

[0095] Example 11

[0096] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that the dispersant in step S1 is a mixture of Tween 80 and hydroxyethyl cellulose in a mass ratio of 1:1.

[0097] Example 12

[0098] A method for preparing a carbon-ceramic heater is carried out according to the method in Example 6, except that short-cut carbon fibers and ceramic powder are premixed to obtain a premix, which is then modified and added to water-soluble liquid phenolic resin and mixed with a dispersant and binder. The modification process includes the following steps:

[0099] The premix was first acidified and stirred in a 4% sulfuric acid solution for 30 minutes, filtered, washed and dried, then soaked in a weakly polar solvent and treated at 55°C for 50 minutes, filtered and dried to obtain the modified premix; the liquid level of the weakly polar solvent and sulfuric acid solution should be above the premix.

[0100] Among them, the water-soluble weakly polar solvents include benzyl alcohol and phenol in a mass ratio of 1:1.

[0101] Example 13

[0102] A method for preparing a carbon-ceramic heater is carried out according to the method in Example 6, except that short-cut carbon fibers and ceramic powder are premixed to obtain a premix, which is then modified and added to water-soluble liquid phenolic resin and mixed with a dispersant and binder. The modification process includes the following steps:

[0103] The premix was first acidified and stirred in a 3% sulfuric acid solution for 30 minutes, filtered, washed and dried, then soaked in a weakly polar solvent and treated at 50°C for 60 minutes, filtered and dried to obtain the modified premix; the liquid level of the weakly polar solvent and sulfuric acid solution should cover the premix.

[0104] Among them, the water-soluble weakly polar solvents include benzyl alcohol and phenol in a mass ratio of 1:0.8.

[0105] Example 14

[0106] A method for preparing a carbon-ceramic heater is carried out according to the method in Example 6, except that short-cut carbon fibers and ceramic powder are premixed to obtain a premix, which is then modified and added to water-soluble liquid phenolic resin and mixed with a dispersant and binder. The modification process includes the following steps:

[0107] The premix was first acidified and stirred in a 4% sulfuric acid solution for 20 minutes, filtered, washed and dried, then soaked in a weakly polar solvent and treated at 60°C for 40 minutes, filtered and dried to obtain the modified premix; the liquid level of the weakly polar solvent and sulfuric acid solution should cover the premix.

[0108] Among them, the water-soluble weakly polar solvents include benzyl alcohol and phenol in a mass ratio of 1:1.2.

[0109] Comparative Example 1

[0110] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that in step S1, T700 carbon fiber unidirectional cloth and carbon fiber mesh are alternately laminated and needle-punched to obtain a carbon / carbon composite material. Then, a slurry is prepared by thoroughly mixing and stirring a dispersant, a binder, ceramic powder and water-soluble liquid phenolic resin. The mass ratio of the carbon / carbon composite material, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin is 1:0.03:0.02:2:10.

[0111] In step S2, the carbon / carbon composite material is placed in a mold, and then the slurry from step S1 is poured into the mold. The carbon / carbon composite material is immersed in the slurry. After immersion for 2 hours, it is filtered, molded, and heated to cure in the manner described in Example 1 to obtain a preform.

[0112] Comparative Example 2

[0113] A method for preparing a carbon ceramic heater is carried out according to the method in Example 1, except that no dispersant is added to the raw materials.

[0114] Performance testing

[0115] The carbon ceramic heaters prepared in the above embodiments and comparative examples were heated and stabilized at 1500℃. Six samples were selected from different parts of the carbon ceramic heaters, and the resistivity of the six samples was measured. The test results are shown in Table 1 below.

[0116] Table 1:

[0117]

[0118] Referring to the test results in Table 1 above, the carbon-ceramic heater prepared in this embodiment has small resistivity fluctuations and high resistivity stability. Combining the test results of Example 1 and Comparative Example 1, the carbon-ceramic heater prepared by alternating stacking and needle punching of carbon / carbon composite materials using commonly used carbon fiber cloth and carbon fiber mesh, followed by subsequent processing, exhibits uneven resistivity and poor stability. Combining the test results of Comparative Example 2, the resistivity stability in Comparative Example 2 without the addition of dispersant is improved compared to Comparative Example 1, but is still worse than that of Example 1.

[0119] Referring to the test results of Examples 1 and 4-5, it can be seen that silicon nitride was used as the ceramic powder in Example 1, silicon powder was used in Example 4, and silicon carbide was used in Example 5. It can be seen that the resistivity stability was better when silicon powder was used in Example 4, and slightly improved in Example 1 compared to Example 5. Referring to the test results of Example 6, the resistivity stability was better when the short-cut carbon fibers and ceramic powder were premixed before addition, compared to the direct mixing of raw materials in Example 1.

[0120] Referring to the test results of Examples 1 and 7-11, it can be seen that when the dispersant in Example 1 is used, the resistivity stability of the final carbon-ceramic heater is better. Referring to the test results of Examples 12-14, the resistivity stability of the final carbon-ceramic heater is better when the short-cut carbon fibers and ceramic powder are treated with acid and then treated with a weakly polar solvent.

[0121] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a carbon ceramic heater, characterized in that, Includes the following steps: S1. Short-cut carbon fibers, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin are mixed and stirred to prepare the original slurry mixture; S2. The original slurry mixture is molded, heated and cured to obtain a preform; S3. Carbonize the preform from step S2 to obtain a preform blank. S4. The preform obtained in step S3 is subjected to densification treatment and graphitization treatment in sequence, and then machined to obtain a carbon ceramic heater. The dispersant is a mixture of hydroxyethyl cellulose and Triton; In step S1, the chopped carbon fibers and ceramic powder are premixed before being added to water-soluble liquid phenolic resin for further mixing. Specifically, the chopped carbon fibers and ceramic powder are premixed to obtain a premix, which is then modified before being added to the water-soluble liquid phenolic resin. The modification process includes the following steps: The premix was first treated with acid and then soaked in a water-soluble weakly polar solvent to obtain a modified premix; wherein the water-soluble weakly polar solvent included benzyl alcohol and phenol in a mass ratio of 1:(0.8-1.2).

2. The method for preparing a carbon ceramic heater according to claim 1, characterized in that: In step S1, the mass ratio of chopped carbon fibers, dispersant, binder, ceramic powder and water-soluble liquid phenolic resin is 1: (0.01-0.05): (0.01-0.03): (1-3): (5-15).

3. The method for preparing a carbon ceramic heater according to claim 1, characterized in that: The adhesive is selected from poly One or more of acrylamide, soluble starch, and polyvinyl alcohol; and / or, the ceramic powder is selected from one or more of silicon carbide, silicon nitride, and silicon powder.

4. The method for preparing a carbon ceramic heater according to claim 1, characterized in that: In step S2, the heating and curing temperature is 150-200℃, the curing time is 5-12h, and the molding pressure is 3-10MPa; In step S3, the carbonization process is carried out in a nitrogen atmosphere, with a carbonization temperature of 900-1200℃ and a carbonization time of 2-5 hours. In step S4, the graphitization temperature is 2000-2400℃.

5. The method for preparing a carbon ceramic heater according to claim 1, characterized in that: In step S4, the densification process is achieved by vapor deposition under a pressure of 2000-4000 Pa. The gas used for vapor deposition is one or more carbon source gases selected from methane, propane or propylene. The vapor deposition temperature is 900-1200℃ and the deposition time is 100-500h. Or / and, the densification treatment is obtained by impregnation and curing in acetal resin or furan resin followed by carbonization, with the impregnation temperature being... The temperature range is 40-60℃, the impregnation pressure is 1-3MPa, the curing temperature is 150-200℃, and the carbonization temperature is 900-1200℃.

6. The method for preparing a carbon ceramic heater according to claim 5, characterized in that: In step S4, after machining the preform, a silicon carbide coating is deposited on the surface of the preform by chemical vapor deposition. The gas source for phase deposition is trichloromethylsilane, with hydrogen as the carrier and nitrogen or argon as the dilution gas. Deposition is carried out at a furnace pressure of 2000-4000 Pa for 100-300 h at a deposition temperature of 1000-1200℃.

7. A carbon ceramic heater prepared by any one of the preparation methods described in claims 1-6.

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