Densification process of binder injection molded silicon nitride ceramic and prepared silicon nitride ceramic
By preparing a binder by mixing silicon nitride powder with a polysilazane precursor and combining it with a multiple impregnation and pyrolysis process, the forming and processing problems of silicon nitride ceramics were solved, enabling the preparation of high-density and high-performance ceramics and expanding their application range.
Patent Information
- Application Number
- CN202511287096.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-10
- Publication Date
- 2025-12-16
AI Technical Summary
Silicon nitride ceramics are difficult to mold into complex components using traditional molding processes and suffer from low density, making them difficult to process and limiting their application in high-precision industries.
A binder was prepared by mixing silicon nitride powder with a polysilazane precursor. The binder was sprayed and molded in combination with a multiple impregnation and pyrolysis process to significantly improve the density of the ceramic green body and achieve densification.
It significantly improves the density and mechanical properties of silicon nitride ceramics, expanding their application range in fields such as medical and chemical engineering, while being low in cost and highly efficient.
Smart Images
Figure CN121135441A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of ceramic material preparation, and particularly relates to a densification process of binder jetting silicon nitride ceramic and prepared silicon nitride ceramic. BACKGROUND
[0002] Silicon nitride (Si3N4) ceramic has excellent performances such as wear resistance, high temperature resistance, chemical stability, high strength and the like, is widely researched and applied as a basic material, is a high-tech material that is developed by many countries, and has been gradually applied to key fields such as aerospace, automobile industry and mechanical manufacturing. However, silicon nitride ceramic is difficult to form complex integrated components due to the limitation of traditional forming processes, and processing has great difficulty and limitation due to the hard and brittle characteristics, which seriously restricts the in-depth application of silicon nitride ceramic in high-precision industries. The binder jetting forming technology can effectively solve the problems such as difficult forming and difficult processing of traditional ceramic materials with complex shapes. However, one of the challenges faced by the ceramic binder jetting technology is that the green body after printing has the problem of low density (or high porosity). In the past research, chemical vapor infiltration / deposition (CVI / CVD) and other methods are usually used for densification treatment of ceramics to improve the performance of the ceramics. However, these technologies have the defects of high cost and long cycle.
[0003] Therefore, it is necessary to design a low-cost and high-efficiency process method for improving the density of the binder jetting formed ceramic and improving the performance of the ceramic to meet the application requirements of silicon nitride ceramic in many fields such as medical treatment and chemical industry. SUMMARY
[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a densification process of binder jetting silicon nitride ceramic, which uses silicon nitride powder and polysilazane precursor to prepare a binder, and can significantly improve the green body density of the ceramic through binder jetting forming. Combined with the multiple impregnation and pyrolysis process, the porosity is further filled to realize densification, effectively solving the problem of low density of silicon nitride ceramic and expanding its application field.
[0005] Another purpose of the present application is to provide a silicon nitride ceramic prepared by the densification process of binder jetting silicon nitride ceramic.
[0006] The technical solutions adopted by the present application are as follows: The densification process of binder jetting silicon nitride ceramic comprises the following steps: (1) mixing and ball milling polysilazane precursor and silicon nitride powder to obtain mixed slurry; (2) using the mixed slurry prepared in step (1) as a binder to perform binder jetting forming on the silicon nitride powder to obtain a ceramic green body; (3) performing heat curing treatment on the ceramic green body prepared in step (2) to obtain a ceramic blank; (4) performing impregnation and pyrolysis on the ceramic blank prepared in step (3) under vacuum conditions by using a polysilazane precursor as an impregnating agent, and repeating the impregnation and pyrolysis process until the density no longer increases, to complete the densification of the silicon nitride ceramic.
[0007] In step (1), the mass ratio of the polysilazane precursor to the silicon nitride powder is (70-90):(10-30).
[0008] In step (1), the particle size of the silicon nitride powder is 20-100 nm.
[0009] In step (1), the ball milling time is 1-6 h, and the ball-to-material ratio is 3:1.
[0010] In step (2), the process parameters of the binder jetting are as follows: the coarse roller speed is 20-100 rpm, the fine roller speed is 150-200 rpm, the platform moving speed is 1-5 mm / sec, the ultrasonic frequency is 20-100 HZ, the printing layer thickness is 30-50 µm, and the binder saturation is 75-160%.
[0011] In step (3), the heat curing temperature is 180-220 ℃, and the time is 4-8 h.
[0012] In step (4), the impregnation time is 1-3 h.
[0013] In step (4), the pyrolysis temperature is 900-1100 ℃, and the pyrolysis time is 2-4 h.
[0014] In step (4), the impregnation and pyrolysis process is repeated for 3-7 times.
[0015] The silicon nitride ceramic is prepared by using the above-mentioned binder jetting densification process of the silicon nitride ceramic, and has a relative density of >95%.
[0016] Compared with the prior art, the present application has the following advantages: (1) By using the silicon nitride powder and the polysilazane precursor to prepare the binder for binder jetting, the ceramic body can be effectively filled by binder jetting during the silicon nitride ceramic forming process, and the internal voids of the formed body can be filled, which significantly improves the density of the ceramic green body during the printing stage compared with the original binder of the equipment. (2) This invention implements multiple impregnation and pyrolysis processes on the ceramic green body, using polysilazane precursor as impregnating agent to further fill the internal pores of the green body and achieve densification, and finally completes the densification process of silicon nitride ceramic; compared with similar densification methods, this process has lower cost, shorter cycle and higher efficiency. (3) The silicon nitride ceramic prepared by the present invention has high density and its key mechanical properties such as hardness and bending strength are significantly improved, which can meet the application requirements of high-performance silicon nitride ceramics in the fields of medical and chemical industries and effectively expand the application scope of silicon nitride ceramics. Attached Figure Description
[0017] Figure 1 The image shows a scanning electron microscope (SEM) image (×1000) of the silicon nitride ceramic prepared in Example 1. Figure 2 The image shows a scanning electron microscope (SEM) image (×1000) of the silicon nitride ceramic prepared in Example 2. Figure 3 The image shows a scanning electron microscope (SEM) image (×1000) of the silicon nitride ceramic prepared in Example 3. Figure 4 The image shows a scanning electron microscope (SEM) image (×1000) of the silicon nitride ceramic prepared in Comparative Example 2. Detailed Implementation
[0018] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.
[0019] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.
[0020] The following is a description of some of the raw materials used in the examples and comparative examples: DURAZANE 1500RC (polysilazane): purchased from Guangzhou Honghai Chemical Technology Co., Ltd. The particle size of silicon nitride powder is 60±40nm.
[0021] Example 1 The densification process for binder-sprayed silicon nitride ceramics includes the following steps: (1) Mix 80g of polysilazane precursor with 20g of silicon nitride powder, put them into a ball mill and ball mill for 6h, using silicon nitride grinding balls, with a ball-to-material ratio of 3:1; after ball milling, a mixed slurry is obtained; (2) In the binder jet printing equipment, silicon nitride powder dried at 60℃ for 4h is used as the powder bed substrate, and the mixed slurry prepared in step (1) is used as the binder. The process parameters for binder jet molding are set as follows: coarse roller speed 50rpm, fine roller speed 175rpm, platform moving speed 3mm / sec, ultrasonic frequency 100HZ, printing layer thickness 50μm, and binder saturation 100%. The printing program is started, and silicon nitride powder is evenly dispersed on the molding platform by ultrasonic vibration, and then compacted by roller to form a flat powder bed; according to the three-dimensional model data after slicing, the nozzle sprays binder in the designated area, and the binder quickly penetrates to the microscopic surface of the powder. The process of spreading powder, compacting, and spraying binder is repeated. By layering, the silicon nitride powder is jet molded with binder to obtain ceramic green body. (3) The ceramic green body obtained in step (2) is transferred to a curing box for heat curing treatment for 6 hours. The heat curing temperature is 190℃. After heat curing is completed, the ceramic green body is obtained. (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) is impregnated and pyrolyzed under -0.1MPa conditions. The impregnation time is 2h, the pyrolysis temperature is increased from room temperature to 1000℃ at a rate of 5℃ / min, and the pyrolysis time is 4h. The impregnation and pyrolysis process is repeated 3 times to complete the densification of silicon nitride ceramic.
[0022] Example 2 The densification process for binder-sprayed silicon nitride ceramics includes the following steps: (1) Mix 70g of polysilazane precursor with 30g of silicon nitride powder, put them into a ball mill and ball mill for 3h. Use silicon nitride grinding balls and the ball-to-material ratio is 3:1. After ball milling, a mixed slurry is obtained. (2) In the binder jet printing equipment, silicon nitride powder dried at 60℃ for 4h is used as the powder bed substrate, and the mixed slurry prepared in step (1) is used as the binder. The process parameters for binder jet molding are set as follows: coarse roller speed 50rpm, fine roller speed 175rpm, platform moving speed 3mm / sec, ultrasonic frequency 100HZ, printing layer thickness 50μm, and binder saturation 100%. The printing program is started, and silicon nitride powder is evenly dispersed on the molding platform by ultrasonic vibration, and then compacted by roller to form a flat powder bed; according to the three-dimensional model data after slicing, the nozzle sprays binder in the designated area, and the binder quickly penetrates to the microscopic surface of the powder. The process of spreading powder, compacting, and spraying binder is repeated. By layering, the silicon nitride powder is jet molded with binder to obtain ceramic green body. (3) The ceramic green body obtained in step (2) is transferred to a curing box for heat curing treatment for 6 hours. The heat curing temperature is 190℃. After heat curing is completed, the ceramic green body is obtained. (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) is impregnated and pyrolyzed under -0.1MPa conditions. The impregnation time is 2h, the pyrolysis temperature is increased from room temperature to 1000℃ at a rate of 5℃ / min, and the pyrolysis time is 4h. The impregnation and pyrolysis process is repeated 5 times to complete the densification of silicon nitride ceramic.
[0023] Example 3 The densification process for binder-sprayed silicon nitride ceramics includes the following steps: (1) Mix 80g of polysilazane precursor with 20g of silicon nitride powder, put them into a ball mill and ball mill for 4h, using silicon nitride grinding balls, with a ball-to-material ratio of 3:1; after ball milling, a mixed slurry is obtained; (2) In the binder jet printing equipment, silicon nitride powder dried at 60℃ for 4h is used as the powder bed substrate, and the mixed slurry prepared in step (1) is used as the binder. The process parameters for binder jet molding are set as follows: coarse roller speed 50rpm, fine roller speed 175rpm, platform moving speed 3mm / sec, ultrasonic frequency 100HZ, printing layer thickness 50μm, and binder saturation 100%. The printing program is started, and silicon nitride powder is evenly dispersed on the molding platform by ultrasonic vibration, and then compacted by roller to form a flat powder bed; according to the three-dimensional model data after slicing, the nozzle sprays binder in the designated area, and the binder quickly penetrates to the microscopic surface of the powder. The process of spreading powder, compacting, and spraying binder is repeated. By layering, the silicon nitride powder is jet molded with binder to obtain ceramic green body. (3) The ceramic green body obtained in step (2) is transferred to a curing box for heat curing treatment for 6 hours. The heat curing temperature is 190℃. After heat curing is completed, the ceramic green body is obtained. (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) was impregnated and pyrolyzed under -0.1MPa conditions. The impregnation time was 2h, and the pyrolysis temperature was increased from room temperature to 1000℃ at a rate of 5℃ / min. The pyrolysis time was 4h. The impregnation and pyrolysis process was repeated 7 times to complete the densification of silicon nitride ceramic.
[0024] The silicon nitride ceramics prepared in Examples 1-3 were characterized using scanning electron microscopy, and the results are as follows: Figures 1-3 As shown. By Figures 1-3 It can be seen that with the increase of the number of impregnation and pyrolysis cycles, the microscopic surface of the obtained silicon nitride ceramic tends to be smooth and dense. This indicates that the densification process of binder spray molding silicon nitride ceramic described in this invention can achieve the filling of ceramic pores; and after high-temperature pyrolysis, silicon nitride ceramic can be generated in situ to further fill the pores, thereby increasing the ceramic density.
[0025] Example 4 The densification process for binder-sprayed silicon nitride ceramics includes the following steps: (1) Mix 70g of polysilazane precursor with 30g of silicon nitride powder, put them into a ball mill and ball mill for 6h, using silicon nitride grinding balls, with a ball-to-material ratio of 3:1; after ball milling, a mixed slurry is obtained; (2) In the binder jet printing equipment, silicon nitride powder dried at 60℃ for 4h is used as the powder bed substrate, and the mixed slurry prepared in step (1) is used as the binder. The process parameters for binder jet molding are set as follows: coarse roller speed 20rpm, fine roller speed 150rpm, platform moving speed 1mm / sec, ultrasonic frequency 100HZ, printing layer thickness 30μm, and binder saturation 75%. The printing program is started, and silicon nitride powder is evenly dispersed on the molding platform by ultrasonic vibration, and then compacted by roller to form a flat powder bed; according to the three-dimensional model data after slicing, the nozzle sprays binder in the designated area, and the binder quickly penetrates to the microscopic surface of the powder. The process of spreading powder, compacting, and spraying binder is repeated. By layering, the silicon nitride powder is jet molded with binder to obtain ceramic green body. (3) The ceramic green body obtained in step (2) is transferred to a curing box for heat curing treatment for 4 hours. The heat curing temperature is 180℃. After heat curing is completed, the ceramic green body is obtained. (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) is impregnated and pyrolyzed under -0.1MPa conditions. The impregnation time is 1h, the pyrolysis temperature is increased from room temperature to 1000℃ at a rate of 5℃ / min, and the pyrolysis time is 2h. The impregnation and pyrolysis process is repeated once to complete the densification of silicon nitride ceramic.
[0026] Example 5 The densification process for binder-sprayed silicon nitride ceramics includes the following steps: (1) Mix 90g of polysilazane precursor with 10g of silicon nitride powder, put them into a ball mill and ball mill for 6h, using silicon nitride grinding balls, with a ball-to-material ratio of 3:1; after ball milling, a mixed slurry is obtained; (2) In the binder jet printing equipment, silicon nitride powder dried at 60℃ for 4h is used as the powder bed substrate, and the mixed slurry prepared in step (1) is used as the binder. The process parameters for binder jet molding are set as follows: coarse roller speed 100rpm, fine roller speed 200rpm, platform moving speed 5mm / sec, ultrasonic frequency 100HZ, printing layer thickness 50μm, and binder saturation 100%. The printing program is started, and silicon nitride powder is evenly dispersed on the molding platform by ultrasonic vibration, and then compacted by roller to form a flat powder bed; according to the three-dimensional model data after slicing, the nozzle sprays binder in the designated area, and the binder quickly penetrates to the microscopic surface of the powder. The process of spreading powder, compacting, and spraying binder is repeated. By layering, the silicon nitride powder is jet molded with binder to obtain ceramic green body. (3) The ceramic green body obtained in step (2) is transferred to a curing box for heat curing treatment for 8 hours. The heat curing temperature is 200℃. After heat curing is completed, the ceramic green body is obtained. (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) was impregnated and pyrolyzed under -0.1 MPa conditions. The impregnation time was 3 h, and the pyrolysis temperature was increased from room temperature to 1000℃ at a rate of 5℃ / min. The pyrolysis time was 4 h. The impregnation and pyrolysis process was repeated 7 times to complete the densification of silicon nitride ceramic.
[0027] Comparative Example 1 The difference from Example 3 is that step (1) is omitted, and in step (2), AquaFuse adhesive from ExOne Corporation of the United States (included with the device) is used.
[0028] Comparative Example 2 The difference from Example 3 is that in step (4), the immersion pyrolysis is performed only once, without repeating the immersion pyrolysis process.
[0029] The silicon nitride ceramics prepared in Comparative Example 2 were characterized using scanning electron microscopy, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the precursor can fill the pores after impregnation, but the number of impregnations is limited, and the ceramic microstructure still has many pore defects and poor compactness.
[0030] The relative density, flexural strength, and Vickers hardness of the silicon nitride ceramics prepared in the examples and comparative examples were tested respectively, and the test methods are as follows: Relative density (%): Tested according to Archimedes' method of displacement; Bending strength (MPa): Tested according to GB / T 45763-2025; Vickers hardness (HV): Tested according to GB / T 16534-1996.
[0031] The test results are shown in Table 1.
[0032] Table 1 Density test results
[0033] As shown in Table 1, in the examples, a mixed slurry prepared from polysilazane precursor and silicon nitride powder was used as a binder. Combined with the impregnation pyrolysis process, silicon nitride was generated in situ from the polysilazane precursor during the pyrolysis process. By repeating the impregnation pyrolysis process, the polysilazane precursor could further fill the ceramic pores. As the number of impregnation pyrolysis cycles increased, the density of the obtained silicon nitride ceramic gradually increased. Moreover, the density was positively correlated with the bending strength and Vickers hardness, and the overall performance of the ceramic was improved accordingly.
[0034] In Comparative Example 1, the binder used was the one that came with the binder jet printing equipment. This binder would completely volatilize during sintering at 1000℃, resulting in defects such as pores inside the silicon nitride ceramic, and a decrease in both density and performance.
[0035] In Comparative Example 2, the limited number of impregnation and pyrolysis cycles prevented the filling of ceramic pores, resulting in the failure to improve the density of the prepared silicon nitride ceramic.
Claims
1. A densification process for binder-sprayed silicon nitride ceramics, characterized in that, Includes the following steps: (1) The polysilazane precursor and silicon nitride powder were mixed and ball-milled to obtain a mixed slurry; (2) The mixed slurry obtained in step (1) is used as a binder to spray silicon nitride powder to obtain a ceramic green body; (3) The ceramic green body obtained in step (2) is subjected to heat curing treatment to obtain a ceramic blank; (4) Using polysilazane precursor as impregnating agent, the ceramic green body obtained in step (3) is impregnated and pyrolyzed under vacuum conditions. The impregnation and pyrolysis process is repeated until the density no longer increases, thus completing the densification of silicon nitride ceramic.
2. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (1), the mass ratio of polysilazane precursor to silicon nitride powder is (70-90):(10-30).
3. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (1), the particle size of silicon nitride powder is 20-100 nm.
4. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (1), the ball milling time is 1-6 hours, and silicon nitride grinding balls are used.
5. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (2), the process parameters for adhesive spraying molding are as follows: coarse roller speed 20-100 rpm, fine roller speed 150-200 rpm, platform moving speed 1-5 mm / sec, ultrasonic frequency 20-100 HZ, printing layer thickness 30-50 μm, and adhesive saturation 75-160%.
6. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (3), the temperature for heat curing is 180-220℃ and the time is 4-8h.
7. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (4), the soaking time is 1-3 hours.
8. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (4), the pyrolysis temperature is 900-1100℃ and the pyrolysis time is 2-4h.
9. The densification process for binder-sprayed silicon nitride ceramics according to claim 1, characterized in that, In step (4), the impregnation and pyrolysis process is repeated 3-7 times.
10. A silicon nitride ceramic, characterized in that, The material is prepared by the densification process of binder spray molding silicon nitride ceramic as described in any one of claims 1-9, and its relative density is >95%.