Pressureless sintered silicon carbide bearing part and preparation method thereof

Abstract

The invention relates to the technical field of refractory materials, in particular to a pressureless sintering silicon carbide bearing part and a preparation method thereof.The pressureless sintering silicon carbide bearing part is prepared from, by mass, 91.0-94.5 parts of superfine silicon carbide micro powder, 1.5-4.5 parts of a sintering aid, 2.5-3.5 parts of a binder, 0.3-1.0 part of a dispersing agent and 0.2-1.0 part of a grain shape adjusting agent; the raw materials are firstly subjected to ball milling, spray drying granulation and mixing extrusion to obtain a biscuit, and then the biscuit is subjected to pressureless sintering at the temperature of 2100-2200 DEG C in an argon protective atmosphere. According to the invention, adipic anhydride and glycidyl methacrylate dual-modified low-viscosity hydroxyethyl cellulose is selected as a grain shape regulator, so that the viscosity of the slurry can be remarkably reduced, the flowability and dispersion stability of the slurry are synchronously improved, and good process suitability is provided for subsequent spray drying granulation and mixing extrusion molding.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a pressureless sintered silicon carbide load-bearing component and its preparation method. Background Technology

[0002] Silicon carbide ceramics, with their combination of high strength, high temperature resistance, wear resistance, high thermal conductivity, and low expansion, have become ideal materials for refractory load-bearing components such as kiln supports and rollers. However, traditional silicon carbide ceramic preparation methods, such as reaction sintering, hot pressing, or gas pressure sintering, suffer from problems including complex processes, high costs, limited product dimensions, and unsatisfactory densification. While pressureless sintering offers advantages such as low cost, suitability for complex shapes, and mass production, achieving high density, high strength, and low porosity still presents challenges, particularly in areas such as ultrafine powder processing, improving green body strength, selecting sintering aids, and optimizing thermal regimes.

[0003] In existing technologies, combinations of common binders and dispersants are often used, which makes it difficult to achieve good rheological properties and green body strength in ultrafine powder systems. This results in high slurry viscosity, difficult molding, easy breakage of the green body, and high porosity of the sintered body. Consequently, the mechanical and thermal properties fail to meet the requirements of high-end load-bearing components. Therefore, developing a silicon carbide load-bearing component with excellent comprehensive performance suitable for pressureless sintering processes and its preparation method has significant industrial application value. Summary of the Invention

[0004] The purpose of this invention is to provide a pressureless sintered silicon carbide support component and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a pressureless sintered silicon carbide support component, wherein the density of the pressureless sintered silicon carbide support component is 3.03–3.14 g / cm³. 3 Apparent porosity ≤ 0.3%, compressive strength ≥ 3900 MPa, coefficient of thermal expansion 4.4 × 10⁻⁶ -6 ~4.5×10 -6 K -1 Its thermal conductivity is 160–180 W / (mk);

[0006] The pressureless sintered silicon carbide support component is made from the following raw materials by weight: 91.0-94.5 parts of ultrafine silicon carbide powder, 1.5-4.5 parts of sintering aid, 2.5-3.5 parts of binder, 0.3-1.0 parts of dispersant, and 0.2-1.0 parts of particle shape modifier;

[0007] The raw materials are first ball-milled, spray-dried and granulated, mixed and extruded to obtain a green body, and then sintered at 2100-2200℃ under an argon protective atmosphere.

[0008] The particle shape modifier is a low-viscosity hydroxyethyl cellulose that is dual-modified with adipic anhydride and glycidyl methacrylate, and the viscosity of the low-viscosity hydroxyethyl cellulose at 25°C and a 2% aqueous solution concentration is 200-300 mPa·s.

[0009] Optionally, the purity of the ultrafine silicon carbide powder is ≥99.8%, and its particle size D50 is 0.5~1.0μm.

[0010] Optionally, the sintering aid is a compound system of boron carbide and carbon powder, wherein the purity of the boron carbide is ≥99.5%, the purity of the carbon powder is ≥99.0%, and the mass ratio of boron carbide to carbon powder is 1:2 to 1:4.

[0011] Optionally, the adhesive is any one of polyvinyl alcohol, sodium carboxymethyl cellulose, and hydroxypropyl methyl cellulose.

[0012] Optionally, the dispersant is any one of tetramethylammonium hydroxide, ammonium polyacrylate, and triammonium citrate.

[0013] Optionally, the preparation method of the particle shape adjuster includes the following steps: (a) dispersing 100g of low-viscosity hydroxyethyl cellulose treated through an 80-mesh sieve in 680mL of isopropanol, adding 120mL of deionized water, and treating with ultrasound at a frequency of 20-30kHz until a uniform milky white suspension is formed; (b) slowly adding 25-30mL of a 20wt% sodium hydroxide aqueous solution to the suspension, heating to 28-32℃ and maintaining the temperature for 25-30min, then continuing to heat to 40-45℃ and reacting for another 35-40min to obtain an alkalized suspension; (c) heating the alkalized suspension to 80-84℃, adding 12-15g of adipic anhydride and 0.3-0.5g of... 4-Dimethylaminopyridine was added with 20wt% sodium hydroxide aqueous solution via an online pH monitor to maintain the pH value of the system at 9.5±0.5. The reaction was carried out at 300-600 r / min for 2-3 h to obtain an adipic anhydride-modified intermediate. (d) The adipic anhydride-modified intermediate was cooled to 70-78℃, and 2.0-2.5 g of tetrabutylammonium bromide was added. Under nitrogen protection, 18-22 g of glycidyl methacrylate was slowly added dropwise. The reaction was carried out at 300-600 r / min for 2-3 h to obtain a dual-modified intermediate. (e) The dual-modified intermediate was cooled to room temperature, and the pH value was adjusted to 7.0±0.2 with glacial acetic acid. The mixture was filtered under vacuum at 0.09 MPa, and the filter cake was washed three times with isopropanol. The filter cake was collected and vacuum dried at 50-60℃ for 1-2 h. The mixture was then pulverized through an 80-mesh sieve to obtain the particle shape adjuster.

[0014] On the other hand, the present invention also provides a method for preparing the above-mentioned pressureless sintered silicon carbide support component, comprising the following preparation steps:

[0015] S1. Ball milling: Mix the raw material with deionized water, control the solid content to be 55-65 wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to be 2:1-3:1, the rotation speed to be 200-300 r / min, and ball mill for 3-4 hours to obtain a slurry.

[0016] S2. Spray drying granulation: The slurry is added to a spray drying device, and the feed temperature is controlled at 25-40℃, the feed rate is 15-20mL / min, the atomizer speed is 20000-25000r / min, the inlet air temperature is 200-220℃, and the outlet air temperature is 85-95℃ to obtain granulated powder.

[0017] S3. Mixing and extrusion: The granulated powder is added to a vacuum mixer, the mixing temperature is controlled at 90-110℃, the mixing time is 40-50 min, the vacuum degree is -0.085--0.095 MPa, and then it is formed by extruder with an extrusion pressure of 8-12 MPa and an extrusion rate of 0.8-1.5 m / min to obtain a green preform.

[0018] S4. Pressureless sintering: The blank is placed in a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1300-1500℃ at 8-10℃ / min and held for 0.5-1h; then, the temperature is raised to 2100-2200℃ at 3-5℃ / min and held for 1.5-2h; and then the temperature is lowered to room temperature at 10-15℃ / min to obtain the pressureless sintered silicon carbide support component.

[0019] Optionally, in S1, the particle size D50 of the slurry is ≤0.8μm, and its viscosity is 800~1500mPa·s.

[0020] Optionally, in S2, the particle size D50 of the granulated powder is 90-110 μm, and its moisture content is ≤0.5 wt%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention uses low-viscosity hydroxyethyl cellulose, which is modified by adipic anhydride and glycidyl methacrylate, as a particle shape modifier. This can significantly reduce the viscosity of the slurry and simultaneously improve the fluidity and dispersion stability of the slurry, providing good process adaptability for subsequent spray drying granulation and compounding extrusion molding.

[0023] 2. This invention can significantly enhance the mechanical strength of the green blank through the particle shape adjustment agent, greatly reducing the risk of breakage of the green blank during the handling and pre-sintering treatment stages. At the same time, the two-step sintering process, through segmented heating and precise heat preservation control, avoids abnormal grain growth while promoting uniform grain refinement, laying a structural foundation for improving the overall performance of the material.

[0024] 3. This invention adopts a pressureless sintering process, which does not require complex special equipment and high-pressure environment, and is suitable for the needs of large-scale industrial production. It has excellent economic benefits and broad prospects for promotion. The pressureless sintered silicon carbide load-bearing components prepared can be applied to the refractory material load-bearing structure of shuttle kiln, tunnel kiln, roller kiln, bell kiln and other industrial furnace tops, as well as load-bearing components on kiln cars that support high-temperature sintered products. Attached Figure Description

[0025] Figure 1 This is a SEM image of the pressureless sintered silicon carbide support component prepared in Example 1 of this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] This invention provides a pressureless sintered silicon carbide support component, which is made from the following raw materials by weight: 92.5 parts of ultrafine silicon carbide powder, 3.5 parts of sintering aid, 3.0 to 3.5 parts of binder, 0.5 parts of dispersant, and 0.5 parts of particle shape modifier.

[0029] The sintering aid is a compound system of boron carbide and carbon powder, with a mass ratio of boron carbide to carbon powder of 1:3. The binder is polyvinyl alcohol. The dispersant is tetramethylammonium hydroxide. The particle shape modifier is low-viscosity hydroxyethyl cellulose dual-modified with adipic anhydride and glycidyl methacrylate. The preparation method of the particle shape modifier includes the following steps:

[0030] (a) 100g of low-viscosity hydroxyethyl cellulose treated by an 80-mesh sieve was dispersed in 680mL of isopropanol, 120mL of deionized water was added, and ultrasonic treatment was performed at a frequency of 25kHz until a uniform milky white suspension was formed.

[0031] (b) Slowly add 28 mL of 20 wt% sodium hydroxide aqueous solution to the suspension, heat to 30 °C and keep the temperature for 27 min, then continue to heat to 42 °C and react for another 38 min to obtain an alkalized suspension;

[0032] (c) The alkalized suspension was heated to 82°C, 13g of adipic anhydride and 0.4g of 4-dimethylaminopyridine were added, and 20wt% sodium hydroxide aqueous solution was added through a pH online monitor to maintain the pH value of the system at 9.5±0.5. The reaction was carried out at 450r / min for 2.5h to obtain the adipic anhydride modified intermediate.

[0033] (d) The adipic anhydride-modified intermediate was cooled to 74°C, 2.3 g of tetrabutylammonium bromide was added, and 20 g of glycidyl methacrylate was slowly added dropwise under nitrogen protection. The reaction was carried out at 450 r / min for 2.5 h with stirring to obtain the double-modified intermediate.

[0034] (e) Cool the dual-modified intermediate to room temperature, adjust the pH value to 7.0±0.2 with glacial acetic acid, filter under vacuum of 0.09MPa, wash the filter cake three times with isopropanol, collect the filter cake and vacuum dry it at 55℃ for 1.5h, and pulverize it through an 80-mesh sieve to obtain the particle shape modifier.

[0035] A method for fabricating pressureless sintered silicon carbide load-bearing components includes the following fabrication steps:

[0036] S1. Ball milling: Mix the raw material with deionized water, control the solid content to 60wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to 2.5:1, the rotation speed to 200-300 r / min, and ball mill for 3.5 hours to obtain a slurry.

[0037] S2. Spray drying granulation: Add the slurry to the spray drying equipment, control the feed temperature to 32℃, the feed rate to 18mL / min, the atomizer speed to 22500r / min, the inlet air temperature to 210℃, and the outlet air temperature to 90℃ to obtain granulated powder.

[0038] S3. Mixing and extrusion: Add the granulated powder to a vacuum mixer, control the mixing temperature at 100℃, the mixing time at 45min, and the vacuum degree at -0.090MPa. Then, it is formed by extruder with an extrusion pressure of 10MPa and an extrusion rate of 1.2m / min to obtain a green preform.

[0039] S4. Pressureless sintering: The blank is placed in a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1400℃ at 9℃ / min and held for 0.8h, then raised to 2150℃ at 4℃ / min and held for 1.7h, and then cooled to room temperature at 12℃ / min to obtain the pressureless sintered silicon carbide support component.

[0040] Example 2

[0041] The present invention provides a pressureless sintered silicon carbide support component, which is made of the following raw materials by weight: 91.0 parts of ultrafine silicon carbide powder, 4.5 parts of sintering aid, 2.5 parts of binder, 1.0 part of dispersant, and 1.0 part of particle shape modifier.

[0042] The sintering aid is a compound system of boron carbide and carbon powder, with a mass ratio of boron carbide to carbon powder of 1:2. The binder is sodium carboxymethyl cellulose. The dispersant is ammonium polyacrylate. The particle shape modifier is low-viscosity hydroxyethyl cellulose dual-modified with adipic anhydride and glycidyl methacrylate. The preparation method of the particle shape modifier includes the following steps:

[0043] (a) 100g of low-viscosity hydroxyethyl cellulose treated by an 80-mesh sieve was dispersed in 680mL of isopropanol, 120mL of deionized water was added, and ultrasonic treatment was performed at a frequency of 20kHz until a uniform milky white suspension was formed.

[0044] (b) Slowly add 25 mL of 20 wt% sodium hydroxide aqueous solution to the suspension, heat to 28 °C and keep the temperature for 30 min, then continue to heat to 40 °C and react for another 40 min to obtain an alkalized suspension.

[0045] (c) The alkalized suspension was heated to 80°C, 12g of adipic anhydride and 0.3g of 4-dimethylaminopyridine were added, and 20wt% sodium hydroxide aqueous solution was added through a pH online monitor to maintain the pH value of the system at 9.5±0.5. The reaction was carried out at 300r / min for 3h to obtain the adipic anhydride modified intermediate.

[0046] (d) Cool the adipic anhydride-modified intermediate to 70°C, add 2.0 g tetrabutylammonium bromide, and slowly add 18 g glycidyl methacrylate dropwise under nitrogen protection. Keep the reaction at 300 r / min for 3 h to obtain the double-modified intermediate.

[0047] (e) Cool the dual-modified intermediate to room temperature, adjust the pH value to 7.0±0.2 with glacial acetic acid, filter under vacuum of 0.09MPa, wash the filter cake three times with isopropanol, collect the filter cake and vacuum dry it at 50℃ for 2h, and pulverize it through an 80-mesh sieve to obtain the particle shape modifier.

[0048] A method for fabricating pressureless sintered silicon carbide load-bearing components includes the following fabrication steps:

[0049] S1. Ball milling: Mix the raw material with deionized water, control the solid content to 55wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to 2:1, the rotation speed to 200r / min, and ball mill for 4 hours to obtain a slurry.

[0050] S2. Spray drying granulation: Add the slurry to the spray drying equipment, control the feed temperature to 25℃, the feed rate to 20mL / min, the atomizer speed to 20000r / min, the inlet air temperature to 200℃, and the outlet air temperature to 85℃ to obtain granulated powder.

[0051] S3. Mixing and extrusion: Add the granulated powder to a vacuum mixer, control the mixing temperature at 90℃, the mixing time at 40min, and the vacuum degree at -0.085MPa. Then, it is formed by an extruder with an extrusion pressure of 8MPa and an extrusion rate of 0.8m / min to obtain a green preform.

[0052] S4. Pressureless sintering: The blank is placed in a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1300℃ at 8℃ / min and held for 0.5h, then raised to 2100℃ at 3℃ / min and held for 1.5h, and then cooled to room temperature at 10℃ / min to obtain the pressureless sintered silicon carbide support component.

[0053] Example 3

[0054] The present invention provides a pressureless sintered silicon carbide support component, which is made of the following raw materials by weight: 94.5 parts of ultrafine silicon carbide powder, 1.5 parts of sintering aid, 3.5 parts of binder, 0.3 parts of dispersant, and 0.2 parts of particle shape modifier.

[0055] The sintering aid is a compound system of boron carbide and carbon powder, with a mass ratio of boron carbide to carbon powder of 1:4. The binder is hydroxypropyl methylcellulose. The dispersant is triammonium citrate. The particle shape modifier is low-viscosity hydroxyethyl cellulose dual-modified with adipic anhydride and glycidyl methacrylate. The preparation method of the particle shape modifier includes the following steps:

[0056] (a) 100g of low-viscosity hydroxyethyl cellulose treated by an 80-mesh sieve was dispersed in 680mL of isopropanol, 120mL of deionized water was added, and ultrasonic treatment was performed at a frequency of 30kHz until a uniform milky white suspension was formed.

[0057] (b) Slowly add 30 mL of 20 wt% sodium hydroxide aqueous solution to the suspension, heat to 32 °C and keep the temperature for 25 min, then continue to heat to 45 °C and react for another 35 min to obtain an alkalized suspension.

[0058] (c) The alkalized suspension was heated to 84°C, 15g of adipic anhydride and 0.5g of 4-dimethylaminopyridine were added, and 20wt% sodium hydroxide aqueous solution was added through a pH online monitor to maintain the pH value of the system at 9.5±0.5. The reaction was carried out at 600r / min for 2h to obtain the adipic anhydride modified intermediate.

[0059] (d) Cool the adipic anhydride-modified intermediate to 78°C, add 2.5 g tetrabutylammonium bromide, and slowly add 22 g glycidyl methacrylate dropwise under nitrogen protection. Keep the reaction at 600 r / min for 2 h to obtain the double-modified intermediate.

[0060] (e) Cool the dual-modified intermediate to room temperature, adjust the pH value to 7.0±0.2 with glacial acetic acid, filter under vacuum of 0.09MPa, wash the filter cake three times with isopropanol, collect the filter cake and vacuum dry it at 60℃ for 1h, and pulverize it through an 80-mesh sieve to obtain the particle shape modifier.

[0061] A method for fabricating pressureless sintered silicon carbide load-bearing components includes the following fabrication steps:

[0062] S1. Ball milling: Mix the raw material with deionized water, control the solid content to 65wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to 3:1, the rotation speed to 300r / min, and ball mill for 3h to obtain a slurry.

[0063] S2. Spray drying granulation: Add the slurry to the spray drying equipment, control the feed temperature to 40℃, the feed rate to 15mL / min, the atomizer speed to 25000r / min, the inlet air temperature to 220℃, and the outlet air temperature to 95℃ to obtain granulated powder.

[0064] S3. Mixing and extrusion: Add the granulated powder to a vacuum mixer, control the mixing temperature at 110℃, the mixing time at 40min, and the vacuum degree at -0.095MPa. Then, it is formed by an extruder with an extrusion pressure of 12MPa and an extrusion rate of 1.5m / min to obtain a preform.

[0065] S4. Pressureless sintering: The blank is placed in a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1500℃ at 10℃ / min and held for 0.5h, then raised to 2200℃ at 5℃ / min and held for 1.5h, and then cooled to room temperature at 15℃ / min to obtain the pressureless sintered silicon carbide support component.

[0066] Example 4

[0067] The present invention provides a pressureless sintered silicon carbide support component, which is made of the following raw materials by weight: 93 parts of ultrafine silicon carbide powder, 3.0 parts of sintering aid, 3.0 parts of binder, 0.4 parts of dispersant, and 0.6 parts of particle shape modifier.

[0068] The sintering aid is a compound system of boron carbide and carbon powder, with a mass ratio of boron carbide to carbon powder of 1:3. The binder is polyvinyl alcohol. The dispersant is tetramethylammonium hydroxide. The particle shape modifier is low-viscosity hydroxyethyl cellulose dual-modified with adipic anhydride and glycidyl methacrylate. The preparation method of the particle shape modifier includes the following steps:

[0069] (a) 100g of low-viscosity hydroxyethyl cellulose treated by an 80-mesh sieve was dispersed in 680mL of isopropanol, 120mL of deionized water was added, and ultrasonic treatment was performed at a frequency of 25kHz until a uniform milky white suspension was formed.

[0070] (b) Slowly add 26 mL of 20 wt% sodium hydroxide aqueous solution to the suspension, heat to 29 °C and keep the temperature for 26 min, then continue to heat to 43 °C and react for another 38 min to obtain an alkalized suspension.

[0071] (c) The alkalized suspension was heated to 82°C, 14g of adipic anhydride and 0.4g of 4-dimethylaminopyridine were added, and 20wt% sodium hydroxide aqueous solution was added through a pH online monitor to maintain the pH value of the system at 9.5±0.5. The reaction was carried out at 420r / min for 2.75h ​​to obtain the adipic anhydride modified intermediate.

[0072] (d) The adipic anhydride-modified intermediate was cooled to 76°C, 2.4 g tetrabutylammonium bromide was added, and 21 g glycidyl methacrylate was slowly added dropwise under nitrogen protection. The reaction was carried out at 420 r / min for 2.5 h to obtain the double-modified intermediate.

[0073] (e) Cool the dual-modified intermediate to room temperature, adjust the pH value to 7.0±0.2 with glacial acetic acid, filter under vacuum of 0.09MPa, wash the filter cake three times with isopropanol, collect the filter cake and vacuum dry it at 55℃ for 1.5h, and pulverize it through an 80-mesh sieve to obtain the particle shape modifier.

[0074] A method for fabricating pressureless sintered silicon carbide load-bearing components includes the following fabrication steps:

[0075] S1. Ball milling: Mix the raw material with deionized water, control the solid content to 55wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to 2.5:1, the rotation speed to 240r / min, and ball mill for 3.5h to obtain a slurry.

[0076] S2. Spray drying granulation: Add the slurry to the spray drying equipment, control the feed temperature to 30℃, the feed rate to 16mL / min, the atomizer speed to 24000r / min, the inlet air temperature to 210℃, and the outlet air temperature to 92℃ to obtain granulated powder.

[0077] S3. Mixing and extrusion: Add the granulated powder to a vacuum mixer, control the mixing temperature at 100℃, the mixing time at 45min, and the vacuum degree at -0.095MPa. Then, it is formed by extruder with an extrusion pressure of 9MPa and an extrusion rate of 1.2m / min to obtain a green preform.

[0078] S4. Pressureless sintering: The blank is placed into a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1300℃ at 9℃ / min and held for 1 hour, then the temperature is raised to 2100℃ at 4℃ / min and held for 2 hours, and then the temperature is lowered to room temperature at 12℃ / min to obtain the pressureless sintered silicon carbide support component.

[0079] In Examples 1-4, the purity of the ultrafine silicon carbide powder is ≥99.8%, and its particle size D50 is 0.5-1.0 μm; the purity of boron carbide is ≥99.5%, and the purity of the carbon powder is ≥99.0%; the viscosity of low-viscosity hydroxyethyl cellulose at 25°C and a 2% aqueous solution concentration is 200-300 mPa·s; in S1, the particle size D50 of the slurry is ≤0.8 μm, and its viscosity is 800-1500 mPa·s; in S2, the particle size D50 of the granulated powder is 90-110 μm, and its moisture content is ≤0.5 wt%.

[0080] Comparative Example 1

[0081] It is basically the same as Example 1, except that low-viscosity hydroxyethyl cellulose is used instead of particle shape modifier.

[0082] Comparative Example 2

[0083] It is basically the same as Example 1, except that no particle shape modifier was used.

[0084] Experimental Example 1

[0085] 1. Test Samples:

[0086] The slurry, green body, and pressureless sintered silicon carbide support components prepared in Examples 1 to 4 were used as comparisons, and the slurry, green body, and pressureless sintered silicon carbide support components of Comparative Examples 1 and 2 were also prepared as comparisons.

[0087] 2. Test methods and standards:

[0088] Slurry viscosity: The apparent viscosity of the ball-milled slurry was measured at 25°C using a rotational viscometer.

[0089] Flexural strength of green blank: The three-point flexural strength of the dried green blank was measured using a strength testing machine to evaluate the strength of the green blank;

[0090] Density: The density of the pressureless sintered silicon carbide load-bearing component was measured using the Archimedes displacement method according to standard GB / T25995-2010.

[0091] Vickers hardness: The Vickers hardness of the pressureless sintered silicon carbide load-bearing components was measured using a Vickers hardness tester according to standard GB / T16534-2009. The test load was 5 kgf, the holding time was 15 s, and 5 points were tested for each sample. The average value was taken.

[0092] Compressive strength: The compressive strength of the pressureless sintered silicon carbide load-bearing component was measured using a universal testing machine in accordance with standard GB / T4740-2024. The sample size was 50mm×50mm×5mm.

[0093] 3. Experimental Results:

[0094] The test results are summarized in Table 1.

[0095] Table 1

[0096]

[0097] As shown in Table 1, the slurry viscosity of Examples 1-4 was significantly lower than that of Comparative Examples 1 and 2, indicating that the particle shape modifier of the present invention can effectively disperse powder, reduce slurry viscosity, and greatly improve the rheological properties and flowability of the slurry during the molding process, making it compatible with subsequent spray granulation and extrusion molding. Meanwhile, the flexural strength of the green blanks of Examples 1-4 was much higher than that of Comparative Examples 1-2, proving that the particle shape modifier, through synergistic effect with the binder, significantly enhanced the mechanical strength of the green blank and reduced the breakage rate during handling and pre-sintering treatment.

[0098] Furthermore, the sintered bodies of Examples 1-4 exhibit significantly superior density, Vickers hardness, and compressive strength compared to Comparative Examples 1-2. The substantial performance improvement compared to Comparative Example 1 demonstrates that hydroxyethyl cellulose alone cannot achieve the effects of this invention. This invention, through dual modification with adipic anhydride and glycidyl methacrylate, endows cellulose with better dispersibility and powder compatibility. The double bonds on its molecular chains may form a weak cross-linked network in the green body, enhancing its strength and allowing for more thorough decomposition and removal during sintering, reducing carbon residue and promoting densification, resulting in products with higher hardness and strength. The performance difference compared to Comparative Example 2 is even greater, further confirming the necessity and crucial role of the particle shape adjuster in this invention.

[0099] Experimental Example 2

[0100] 1. Test Samples:

[0101] The pressureless sintered silicon carbide support components prepared in Examples 1 to 4 were used as comparison components, and pressureless sintered silicon carbide support components of Comparative Example 1 and Comparative Example 2 were also prepared as comparison components.

[0102] 2. Test methods and standards:

[0103] Apparent porosity: Measured according to standard GB / T 25995-2010;

[0104] Coefficient of thermal expansion: The average linear expansion coefficient from 25 to 1500℃ was measured according to standard GB / T 16968-2021, and the test atmosphere was argon.

[0105] Thermal conductivity: Measured using a laser flash thermal conductivity meter according to standard GB / T 22588-2008, with argon atmosphere and a test temperature of 20℃.

[0106] 3. Experimental Results:

[0107] The test results are summarized in Table 2.

[0108] Table 2

[0109]

[0110] As shown in Table 2, the apparent porosity of Examples 1-4 is only 0.21%-0.30%, all controlled within 0.3% at a high densification level, significantly better than Comparative Examples 1-2. This indicates that the particle shape modifier can adhere to the surface of the powder particles, reducing interparticle agglomeration and friction, providing lubrication and steric hindrance, enabling the green body to achieve sufficient densification during forming and sintering, effectively reducing internal porosity defects, and providing structural protection for the improvement of the material's mechanical and thermal properties. Furthermore, in terms of thermal expansion coefficient and thermal conductivity, Examples 1-4 are also significantly better than Comparative Examples 1-2, indicating that the thermal properties of Examples 1-4 are synergistically optimized, suitable for high-temperature service scenarios. The pressureless sintered silicon carbide load-bearing components prepared by this invention can be applied to refractory load-bearing structures for shuttle kilns, tunnel kilns, roller kilns, bell kilns, and other industrial sealed furnace roofs, as well as load-bearing components for high-temperature sintered products on kiln cars.

[0111] Please see Figure 1 As can be seen, the grain size distribution is relatively uniform. According to the 10μm scale in the lower right corner of the figure, the grain length is approximately 4–10μm. A small number of diffusely distributed dark micro-dots can be seen in the figure, corresponding to residual pores or sintering aid-enriched phases. No obvious intergranular looseness or coarse pores are observed, indicating that the material has high density. This is consistent with the test results of ≤0.3% porosity shown in Table 2, which is in line with the structural characteristics of low porosity in pressureless sintered silicon carbide.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pressureless sintered silicon carbide load-bearing component, characterized in that: The density of the pressureless sintered silicon carbide support component is 3.03–3.14 g / cm³. 3 Apparent porosity ≤0.3%, compressive strength ≥3900MPa, coefficient of thermal expansion 4.4×10 -6 ~4.5×10 -6 K -1 Its thermal conductivity is 160–180 W / (mk); The pressureless sintered silicon carbide support component is made from the following raw materials by weight: 91.0-94.5 parts of ultrafine silicon carbide powder, 1.5-4.5 parts of sintering aid, 2.5-3.5 parts of binder, 0.3-1.0 parts of dispersant, and 0.2-1.0 parts of particle shape modifier; The raw materials are first ball-milled, spray-dried and granulated, mixed and extruded to obtain a green body, and then sintered at 2100-2200℃ under an argon protective atmosphere. The particle shape modifier is a low-viscosity hydroxyethyl cellulose that is dual-modified with adipic anhydride and glycidyl methacrylate, and the viscosity of the low-viscosity hydroxyethyl cellulose at 25°C and a 2% aqueous solution concentration is 200-300 mPa·s.

2. The pressureless sintered silicon carbide bearing component according to claim 1, characterized in that: The ultrafine silicon carbide powder has a purity of ≥99.8% and a particle size D50 of 0.5~1.0μm.

3. The pressureless sintered silicon carbide load-bearing component according to claim 1, characterized in that: The sintering aid is a compound system of boron carbide and carbon powder, wherein the purity of the boron carbide is ≥99.5%, the purity of the carbon powder is ≥99.0%, and the mass ratio of boron carbide to carbon powder is 1:2 to 1:

4.

4. The pressureless sintered silicon carbide bearing component according to claim 1, characterized in that: The adhesive is any one of polyvinyl alcohol, sodium carboxymethyl cellulose, and hydroxypropyl methyl cellulose.

5. The pressureless sintered silicon carbide bearing component according to claim 1, characterized in that: The dispersant is any one of tetramethylammonium hydroxide, ammonium polyacrylate, and triammonium citrate.

6. The pressureless sintered silicon carbide load-bearing component according to claim 1, characterized in that: The preparation method of the particle shape modifier includes the following steps: (a) dispersing 100g of low-viscosity hydroxyethyl cellulose treated through an 80-mesh sieve in 680mL of isopropanol, adding 120mL of deionized water, and treating with ultrasound at a frequency of 20-30kHz until a uniform milky white suspension is formed; (b) slowly adding 25-30mL of a 20wt% sodium hydroxide aqueous solution to the suspension, heating to 28-32℃ and maintaining the temperature for 25-30min, then continuing to heat to 40-45℃ and reacting for another 35-40min to obtain an alkalized suspension; (c) heating the alkalized suspension to 80-84℃, adding 12-15g of adipic anhydride and 0.3-0.5g of... 4-Dimethylaminopyridine was added with 20wt% sodium hydroxide aqueous solution via an online pH monitor to maintain the pH value of the system at 9.5±0.

5. The reaction was carried out at 300-600 r / min for 2-3 h to obtain an adipic anhydride-modified intermediate. (d) The adipic anhydride-modified intermediate was cooled to 70-78℃, and 2.0-2.5 g of tetrabutylammonium bromide was added. Under nitrogen protection, 18-22 g of glycidyl methacrylate was slowly added dropwise. The reaction was carried out at 300-600 r / min for 2-3 h to obtain a dual-modified intermediate. (e) The dual-modified intermediate was cooled to room temperature, and the pH value was adjusted to 7.0±0.2 with glacial acetic acid. The mixture was filtered under vacuum at 0.09 MPa, and the filter cake was washed three times with isopropanol. The filter cake was collected and vacuum dried at 50-60℃ for 1-2 h. The mixture was then pulverized through an 80-mesh sieve to obtain the particle shape adjuster.

7. A method for preparing a pressureless sintered silicon carbide support component as described in any one of claims 1 to 6, characterized in that: The preparation steps include the following: S1. Ball milling: Mix the raw material with deionized water, control the solid content to be 55-65 wt%, and then place it in a ball mill. Use silicon carbide as grinding balls, control the ball-to-material ratio to be 2:1-3:1, the rotation speed to be 200-300 r / min, and ball mill for 3-4 hours to obtain a slurry. S2. Spray drying granulation: The slurry is added to a spray drying device, and the feed temperature is controlled at 25-40℃, the feed rate is 15-20mL / min, the atomizer speed is 20000-25000r / min, the inlet air temperature is 200-220℃, and the outlet air temperature is 85-95℃ to obtain granulated powder. S3. Mixing and extrusion: The granulated powder is added to a vacuum mixer, the mixing temperature is controlled at 90-110℃, the mixing time is 40-50 min, the vacuum degree is -0.085--0.095 MPa, and then it is formed by extruder with an extrusion pressure of 8-12 MPa and an extrusion rate of 0.8-1.5 m / min to obtain a green preform. S4. Pressureless sintering: The blank is placed in a graphite crucible and sintered in two steps under argon protection: first, the temperature is raised to 1300-1500℃ at 8-10℃ / min and held for 0.5-1h; then, the temperature is raised to 2100-2200℃ at 3-5℃ / min and held for 1.5-2h; and then the temperature is lowered to room temperature at 10-15℃ / min to obtain the pressureless sintered silicon carbide support component.

8. The method for preparing a pressureless sintered silicon carbide load-bearing component according to claim 7, characterized in that: In S1, the particle size D50 of the slurry is ≤0.8μm, and its viscosity is 800~1500mPa·s.

9. The method for preparing a pressureless sintered silicon carbide load-bearing component according to claim 7, characterized in that: In S2, the particle size D50 of the granulated powder is 90-110 μm, and its moisture content is ≤0.5 wt%.

Images