A high-density, high-thermal-conductivity silicon nitride ceramic, its preparation method and application

Abstract

This invention discloses a high-density, high-thermal-conductivity silicon nitride ceramic, its preparation method, and its applications, belonging to the field of ceramic material preparation technology. The preparation method includes the following steps: 1. Ball milling and mixing: Weigh 72-80% ceramic powder, 15-25% photosensitive resin, 2-5% dispersant, 0.5-0.8% initiator, and 0.03-0.09% defoamer by mass percentage, and ball mill and mix to obtain a mixture; 2. Photocuring and molding; 3. Vacuum debinding; 4. Air decarburization; 5. Sintering. Beneficial effects: This invention significantly improves the comprehensive performance of photocurable silicon nitride ceramic slurry by optimizing the type and ratio of the slurry, effectively overcoming problems such as poor fluidity, sedimentation, and decreased thermal conductivity in existing technologies, providing technical support for the efficient and precise manufacturing of high-performance silicon nitride ceramics. The prepared silicon nitride ceramic parts have high thermal conductivity and are suitable for electronic devices and precision machinery with high heat dissipation requirements.

Description

Technical Field

[0001] This invention relates to the field of ceramic material preparation technology, specifically to a high-density, high-thermal-conductivity silicon nitride ceramic, its preparation method, and its application. Background Technology

[0002] Silicon nitride (Si3N4) has been widely used in electronics, aerospace, and precision machinery due to its excellent mechanical properties, chemical stability, and high thermal conductivity. In recent years, as the manufacturing industry has developed towards high performance and complex structures, traditional silicon nitride preparation methods (such as compression molding and injection molding) have become insufficient to meet the requirements of complex shapes, high precision, and customization.

[0003] Photopolymer 3D printing technology, with its high precision and efficiency, offers a new solution for manufacturing complex-shaped ceramic parts. However, traditional photopolymer ceramic slurries are mostly based on oxide ceramics, and the development of nitride ceramic slurries still faces many challenges. In particular, high thermal conductivity silicon nitride slurries, due to their high viscosity, high solid content, and optical properties, struggle to balance flowability, dispersibility, and curing properties in photopolymer printing, directly affecting the accuracy and performance of the printed parts.

[0004] While existing technologies have proposed methods to improve slurry formulations, such as introducing dispersants, modifying photoinitiators, or optimizing slurry components to enhance the performance of silicon nitride slurries, these methods often lead to a decrease in the thermal conductivity of the material while improving slurry flowability or curing speed, making it difficult to meet the requirements of high thermal conductivity applications. Furthermore, the stability issues of the slurry during long-term printing, such as sedimentation and uneven curing, have not been adequately addressed, resulting in significant fluctuations in the quality of printed parts.

[0005] Chinese patent application CN118420356A discloses a silicon nitride powder, its preparation method, and silicon nitride ceramics. The preparation method of the silicon nitride powder includes mixing liquid silicon halide and a silicon-based additive with a particle size of 50 nm-500 nm in a protective atmosphere at a weight ratio of 100:1-11 to form a mixed slurry; introducing the mixed slurry into the interior of liquid ammonia in a reactor, where the liquid silicon halide and liquid ammonia react in a temperature range of -50°C to 50°C to obtain precursor powder; allowing it to stand, filter, separate, and solvent-wash to remove byproducts, obtaining a solid mixture; calcining the solid mixture in a nitrogen-containing atmosphere at a temperature range of 1300°C-1600°C for 0.5-5 hours to obtain silicon nitride powder; the weight ratio of liquid silicon halide to liquid ammonia is 1:3-15, and the silicon-based additive is silicon powder or α-phase silicon nitride with an α-phase content greater than or equal to 93%. However, the thermal conductivity of silicon nitride ceramics prepared by this method is not high and needs further improvement. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to solve the problems of poor stability of existing photopolymer 3D printing ceramic slurry and poor thermal conductivity of the prepared ceramic material.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] This invention proposes a method for preparing high-density, high-thermal-conductivity silicon nitride ceramics, comprising the following steps:

[0009] (1) Ball milling and mixing: Weigh 72-80% ceramic powder, 15-25% photosensitive resin, 2-5% dispersant, 0.5-0.8% initiator and 0.03-0.09% defoamer by mass percentage, and ball mill and mix to obtain a mixture;

[0010] The ceramic powder is a mixture of silicon nitride, magnesium oxide, and yttrium oxide in a mass ratio of 95:1.5:3.5;

[0011] (2) Photopolymerization molding: The mixture is sieved and fed into the material cylinder of the photopolymerization printer. The prepared slice file is imported into the printer to start printing the green blank.

[0012] (3) Vacuum debinding: The silicon nitride ceramic green body obtained in step (2) is placed in a vacuum furnace and pre-fired;

[0013] (4) Air decarbonization: Place the material obtained in step (3) in a muffle furnace and pre-fire it;

[0014] (5) Sintering: The material obtained in step (4) is sintered to obtain a high-density, high-thermal-conductivity silicon nitride ceramic.

[0015] Preferably, the average particle size of the silicon nitride, magnesium oxide, and yttrium oxide is 0.1-1.0 μm.

[0016] Preferably, the photosensitive resin is any one or a mixture of HEA and HDDA.

[0017] Preferably, the dispersant is any one or a mixture of CPD03, CPD07, and CPD08.

[0018] Preferably, the initiator is any one or a mixture of CPI-01, CPI-02, and CPI-03.

[0019] Preferably, the defoamer is any one or a mixture of SN485, BYK-066N, and TBP.

[0020] Preferably, in step (2), the mixture is passed through a 300-mesh sieve.

[0021] Preferably, in step (3), the preheating temperature is 380-420℃ and the time is 1-3h.

[0022] Preferably, in step (4), the preheating temperature is 550-650℃ and the time is 0.5-1.5h.

[0023] Preferably, in step (5), the sintering temperature is 1800-2000℃ and the time is 1-3h.

[0024] A second aspect of the present invention provides for the preparation of high-density, high-thermal-conductivity silicon nitride ceramics by the above-described preparation method.

[0025] A third aspect of the present invention proposes the application of the above-mentioned high-density, high-thermal-conductivity silicon nitride ceramics in the fields of electronic instruments and precision machinery.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention significantly improves the overall performance of photocurable silicon nitride ceramic slurry by optimizing the type and ratio of the slurry, effectively overcoming problems such as poor fluidity, sedimentation, and decreased thermal conductivity in existing technologies. This provides a technical guarantee for the efficient and precise manufacturing of high-performance silicon nitride ceramics. The prepared silicon nitride ceramic parts have high thermal conductivity and are suitable for electronic devices, precision machinery, and aerospace applications with high heat dissipation requirements.

[0028] 2. Excellent dispersibility and flowability: By optimizing the type and amount of dispersant, the slurry of this invention maintains good dispersibility even under high solid content (40-60wt%), with viscosity controlled at 500-2000 mPa·s (25℃), effectively improving the material flowability and uniformity during the printing process. No significant sedimentation occurs during long-term printing, ensuring stable print quality.

[0029] 3. Rapid and uniform photocuring performance: Utilizing a suitable photoinitiator system and resin formulation, the slurry cures rapidly in the ultraviolet band (365-405nm), with a curing time of less than 5 seconds and a curing depth of 70-150μm, meeting the needs of precision 3D printing. Strong adhesion between cured layers prevents interlayer breakage or warping, improving the overall mechanical properties of the printed parts.

[0030] 4. The resulting ceramic parts have high thermal conductivity: The thermal conductivity of silicon nitride ceramic parts prepared after printing and sintering can reach more than 80W / m·K, which is comparable to or even better than that of traditional silicon nitride ceramic parts. They are suitable for electronic devices, precision machinery and aerospace fields with high heat dissipation requirements. Attached Figure Description

[0031] Figure 1 The figure shows the viscosity test results of the silicon nitride ceramic slurry prepared in Example 1 of this invention;

[0032] Figure 2 This is a graph showing the viscosity test results of the silicon nitride ceramic slurry prepared in Comparative Example 1 of this invention;

[0033] Figure 3 This is a graph showing the viscosity test results of the silicon nitride ceramic slurry prepared in Comparative Example 2 of this invention; Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0035] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0036] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0037] Experimental Example 1:

[0038] A method for preparing high-density, high-thermal-conductivity silicon nitride ceramics includes the following steps:

[0039] Step 1: Ball Milling and Mixing: Weigh out a fixed amount of ceramic powder, photosensitive resin, dispersant, initiator, and defoamer according to a 50 vol% solid content. The ceramic powder is a mixture of silicon nitride, magnesium oxide, and yttrium oxide in a mass ratio of 95:1.5:3.5 (the average particle size of silicon nitride, magnesium oxide, and yttrium oxide is 0.6 μm). The photosensitive resin is either HEA or HDDA (mass ratio 1:1). CPD07 is used as the dispersant, CPI-01 as the initiator, and SN-485 as the defoamer. After conversion, the weighing ratio of each raw material in this process is as follows:

[0040] Table 1

[0041]

[0042]

[0043] After weighing the raw materials, they were mixed in a planetary ball mill at 350 r / min for 4 h to obtain a mixture.

[0044] Step Two: Photopolymerization: The slurry obtained in Step One is fed into the ink tank of a 382nm wavelength photopolymer printer through a 300-mesh sieve, and the exposure intensity is set to 100mW / cm². 2Set the exposure time to 3 seconds and the scraper movement speed to 1000 mm / min. Import the prepared slice file into the printer and start printing the green blank.

[0045] Step 3: Vacuum debinding: The silicon nitride ceramic green body obtained in Step 2 is heated to 400℃ in a vacuum furnace at a rate of 0.3℃ / min and pre-fired for 2 hours to remove organic matter.

[0046] Step 4: Air decarbonization: The material obtained in Step 3 is heated to 600℃ in a muffle furnace at a rate of 10℃ / min and pre-fired for 1 hour to remove residual carbon from organic matter.

[0047] Step 5: Sintering: The material obtained in Step 4 is heated to 1900℃ in air pressure at 5℃ / min and sintered for 2h to obtain high-density, high-thermal-conductivity silicon nitride ceramic.

[0048] The performance of the slurry and finished silicon nitride ceramic of Example 1 was tested using the following method:

[0049] The viscosity of the silicon nitride slurry was tested using a rotational viscometer of model NDJ-8S. A #4 rotor was used, and the rotational speed was set to 60 RPM. The reading on the viscometer was read after the progress bar on the side of the viscometer reached the top.

[0050] Thermal conductivity of silicon nitride wafers was tested using a laser flare method.

[0051] The test results show that the viscosity of the silicon nitride ceramic slurry is 2610 mPa·s. (e.g.) Figure 1 (As shown)

[0052] Three samples were randomly selected and their thermal conductivity was tested. The results are shown in Table 2 below:

[0053] Table 2

[0054]

[0055] As shown in Table 1, the measured thermal conductivity values ​​are 80.670, 81.561, and 80.419 W / (m*K).

[0056] Example 2:

[0057] The difference between this embodiment and Embodiment 1 is that the average particle size of silicon nitride, magnesium oxide, and yttrium oxide is 0.1 μm, while the rest is the same as in Embodiment 1.

[0058] Example 3:

[0059] The difference between this embodiment and Embodiment 1 is that the average particle size of silicon nitride, magnesium oxide, and yttrium oxide is 1.0 μm, while the rest is the same as in Embodiment 1.

[0060] Example 4:

[0061] The difference between this embodiment and Embodiment 1 is that: 72% ceramic powder, 25% photosensitive resin, 2.41% dispersant, 0.5% initiator and 0.09% defoamer, the rest are the same as in Embodiment 1.

[0062] Example 5:

[0063] The difference between this embodiment and Embodiment 1 is that: 80% ceramic powder, 15% photosensitive resin, 4.17% dispersant, 0.8% initiator and 0.03% defoamer, the rest are the same as in Embodiment 1.

[0064] Example 6:

[0065] The difference between this embodiment and embodiment 1 is that: in step (3), the pre-firing temperature is 380℃ and the time is 3h; in step (4), the pre-firing temperature is 650℃ and the time is 0.5h; in step (5), the sintering temperature is 1800℃ and the time is 3h, and the rest is the same as in embodiment 1.

[0066] Example 7:

[0067] The difference between this embodiment and embodiment 1 is that: in step (3), the pre-firing temperature is 420℃ and the time is 1h; in step (4), the pre-firing temperature is 550℃ and the time is 1.5h; in step (5), the sintering temperature is 2000℃ and the time is 1h, and the rest is the same as in embodiment 1.

[0068] Comparative Example 1:

[0069] The difference between this comparative example and Example 1 is that the powder ratio in step one is modified: the powder is a mixture of silicon nitride, magnesium oxide, and yttrium oxide in a mass ratio of 95:3.5:1.5. The rest is the same as in Example 1. After conversion, the weighing ratio of each raw material in this process is:

[0070] Table 3

[0071]

[0072] The performance of the slurry and finished silicon nitride ceramic of Comparative Example 1 was tested using the same method as in Example 1.

[0073] The test results show that the viscosity of the silicon nitride ceramic slurry is 2949 mPa·s. (e.g.) Figure 2 (As shown)

[0074] Three samples were randomly selected and their thermal conductivity was tested. The results are shown in Table 4 below:

[0075] Table 4

[0076]

[0077] As shown in Table 4, the measured thermal conductivity values ​​are 45.289, 44.550, and 44.583 W / (m*K).

[0078] Comparative Example 2:

[0079] The difference between this comparative example and Example 1 is that the type of powder in step one has been modified: the powder is now only silicon nitride. The remaining steps are the same as in Example 1. After conversion, the weighing ratio of each raw material in this process is:

[0080] Table 5

[0081]

[0082] The performance of the slurry and finished silicon nitride ceramic of Comparative Example 2 was tested using the same method as in Example 1.

[0083] The test results show that the viscosity of the silicon nitride ceramic slurry is 2520 mPa·s. (e.g.) Figure 3 (As shown)

[0084] Three samples were randomly selected and their thermal conductivity was tested. The results are shown in Table 6 below:

[0085] Table 6

[0086]

[0087] As shown in Table 6, the measured thermal conductivity values ​​are 22.254, 21.403, and 22.560 W / (m*K).

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-density, high-thermal-conductivity silicon nitride ceramic, characterized in that, Includes the following steps: (1) Ball milling and mixing: Weigh 72-80% ceramic powder, 15-25% photosensitive resin, 2-5% dispersant, 0.5-0.8% initiator and 0.03-0.09% defoamer by mass percentage, and ball mill and mix to obtain a mixture; The ceramic powder is a mixture of silicon nitride, magnesium oxide, and yttrium oxide in a mass ratio of 95:1.5:3.5; The photosensitive resin is any one or a mixture of HEA and HDDA; The dispersant is any one or a mixture of CPD03, CPD07, and CPD08; The initiator is any one or a mixture of CPI-01, CPI-02, and CPI-03; the defoamer is any one or a mixture of SN485, BYK-066N, and TBP. (2) Photopolymerization molding: The mixture is sieved and fed into the material cylinder of the photopolymerization printer. The prepared slice file is imported into the printer to start printing the green blank. (3) Vacuum debinding: Place the silicon nitride ceramic green body obtained in step (2) in a vacuum furnace for pre-firing; the pre-firing temperature is 380-420℃ and the time is 1-3h; (4) Air decarbonization: Place the material obtained in step (3) in a muffle furnace and pre-fire it; the pre-fire temperature is 550-650℃ and the time is 0.5-1.5h; (5) Sintering: The material obtained in step (4) is sintered to obtain a high-density, high-thermal-conductivity silicon nitride ceramic; The sintering temperature is 1800-2000℃ and the time is 1-3h.

2. The preparation method according to claim 1, characterized in that, The average particle size of the silicon nitride, magnesium oxide, and yttrium oxide is 0.1-1.0 µm.

3. The preparation method according to claim 1, characterized in that, The photosensitive resin is HEA.

4. The preparation method according to claim 1, characterized in that, The dispersant is CPD07.

5. The preparation method according to claim 1, characterized in that, The initiator is CPI-01; the defoamer is SN485.

6. The preparation method according to claim 1, characterized in that, In step (2), the mixture is passed through a 300-mesh sieve.

7. The preparation method according to claim 1, characterized in that, In step (3), the preheating temperature is 400℃ and the time is 2 h; in step (4), the preheating temperature is 600℃ and the time is 1 h.

8. The preparation method according to claim 1, characterized in that, In step (5), the sintering temperature is 1900℃ and the time is 2 h.

9. The high-density, high-thermal-conductivity silicon nitride ceramic prepared by the preparation method according to any one of claims 1-8.

10. The application of the high-density, high-thermal-conductivity silicon nitride ceramic of claim 9 in the fields of electronic instruments and precision machinery.

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