A method for preparing a Si3N4-Si2N2O-based wave-transparent ceramic material by normal pressure sintering

Abstract

The application discloses a method for preparing Si3N4-Si2N2O-based wave-transparent ceramic material by normal-pressure sintering. Firstly, Si2N2O powder is prepared by sintering Si powder and SiO powder; then, the Si2N2O powder is uniformly dispersed and homogenized to form a gel-state liquid; then, an initiator is added into the gel-state liquid; a high-strength blank is formed in-situ by a physical and chemical reaction in a corresponding mold cavity; the blank is pre-sintered to decompose a small part of the Si2N2O to obtain Si3N4; finally, high-temperature normal-pressure sintering is carried out in a nitrogen atmosphere to inhibit the decomposition of the Si2N2O and to densify the Si2N2O. The method of 'firstly sintering powder and then sintering' is used to prepare high-purity silicon oxynitride powder, and the Si3N4-Si2N2O-based wave-transparent ceramic is prepared by a two-step sintering process, so that the excellent wave-transparent performance of Si2N2O is retained, the good mechanical performance of Si3N4 is introduced, and finally the preparation of high-temperature wave-transparent ceramic material is realized.

Description

Technical Field

[0001] This invention relates to the field of ceramic material powder preparation and ceramic material preparation technology, and more specifically to a Si3N4-Si2N2O-based microwave-transparent ceramic material and its preparation method. Background Technology

[0002] Si₂N₂O possesses low dielectric constant and dielectric loss, excellent high-temperature mechanical properties, and resistance to oxidation and thermal shock, demonstrating great potential in the field of high-temperature microwave-transparent materials. Si₃N₄ is characterized by high hardness, high strength, and low coefficient of thermal expansion. Especially noteworthy are the excellent high-temperature resistance, chemical inertness to metals, ultra-high hardness, and fracture toughness exhibited by silicon nitride ceramics under high-temperature conditions. Combining the two yields Si₃N₄-Si₂N₂O-based microwave-transparent ceramic materials, which further improve mechanical properties while maintaining excellent high-temperature microwave transmission performance.

[0003] Ohashi et al. studied the effects of different sintering aid oxides on the liquid-phase reaction synthesis of Si2N2O. The results showed that Si2N2O is formed by the reaction of SiO2 and Si3N4, and its formation rate is affected by the liquid phase composition. Equimolar amounts of MgO have a greater promoting effect on Si2N2O formation than equimolar amounts of ZrO2, 1 / 2Al2O3, 1 / 2Ln2O3, and PSZ. With increasing amounts of sintering aids, the high-temperature liquid phase during sintering increases, and the intergranular phase also increases after cooling, leading to a deterioration in the high-temperature mechanical properties and oxidation resistance of Si2N2O ceramics. Huang Zhengyu et al. prepared Si2N2O and α-Si3N4 synergistically toughened Si3N4 ceramics by adding 5 wt.% Si2N2O seed crystals through gel injection molding and pressureless sintering processes. Traditional preparation methods use Si3N4 and SiO2 as raw materials to generate Si2N2O. This method of preparing Si3N4-Si2N2O multiphase ceramics using Si3N4 as raw material has the following problems: it requires the addition of SiO2, the preparation method is complicated, and SiO2 is easily left in the final product.

[0004] Patent CN102807389A discloses a method for preparing Si3N4-Si2N2O porous multiphase ceramics. The method involves mixing Si3N4 with a dispersant and other reactants to form a slurry, drying and statically pressing it to obtain a green body, and then sintering the green body without pressure to obtain Si3N4-Si2N2O porous multiphase ceramics. However, the mixed slurry formed by this patent has poor dispersibility and uniformity, which leads to insufficient subsequent reactions. During the sintering stage, the temperature gradient is not refined, making it difficult to control the decomposition of Si2N2O and the formation of Si3N4. This reduces the density of Si3N4-Si2N2O and affects its performance. Summary of the Invention

[0005] To overcome the problem of poor sintering density of existing Si3N4-Si2N2O ceramics, this invention provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering, characterized by comprising the following steps:

[0008] S1. Mix raw material Si powder and SiO powder evenly according to the mass ratio, vacuum the mixture and then introduce N2. Sinter at 1400-1450℃ to obtain coarse powder. Then add alcohol and dispersant and grind to obtain Si2N2O powder.

[0009] S2. Mix Si2N2O powder and sintering aid with organic matter to form a gel-like liquid;

[0010] S3. Add an initiator to the gel liquid to form a preform;

[0011] S4. Pre-sintering treatment of the green body: heating from 40℃ to 150~160℃ at a heating rate of 0.5~3℃ / min, holding for 10~20min; heating from 200℃ to 350~400℃ at a heating rate of 3~7℃ / min, holding for 20~30min; heating from 420℃ to 750~800℃ at a heating rate of 3~7℃ / min, holding for 10~20min; heating at a rate of 3~7℃ / min, and finally holding at 1100~1300℃ for 0.5~1h.

[0012] S5. The pre-sintered green body is subjected to high-temperature atmospheric pressure sintering: under N2 atmosphere protection at 0.02-0.05 MPa, the temperature is raised to 550-600℃ at a heating rate of 3-7℃ / min; to 950-1000℃ at a heating rate of 10℃ / min; and to 1400-1600℃ at a heating rate of 3-7℃ / min, and held for 1-2 hours.

[0013] Furthermore, the amount of dispersant added in step S1 is 2 wt.%.

[0014] Furthermore, the mass ratio of Si powder and SiO powder to alcohol is 1:1:2.

[0015] Furthermore, the sintering stage in step S1 includes: pumping the gas pressure down to -0.25 MPa and then introducing N2 to return it to normal pressure; raising the sintering temperature to 550-600℃ at a heating rate of 3-7℃ / min, to 950-1000℃ at a heating rate of 10℃ / min, and to 1400-1450℃ at a heating rate of 5℃ / min, and holding at that temperature for 1-2 hours.

[0016] Furthermore, the sintering aid content is 5 wt.% MgO, 9 wt.% Y2O3, and the organic matter content is 20 wt.%.

[0017] Furthermore, the organic matter is a monomer, a crosslinking agent, a dispersant, an initiator, or a catalyst, with a mass ratio of 8:8:2:1:1.

[0018] Further, the sintering aid is one or more of MgO and Y2O3; the monomer is one or more of acrylic acid and dimethylacrylamide; the crosslinking agent is N,N-methyleneacrylamide; the dispersant is one or more of polyethylene glycol, polyethylene glycol, and ammonium polyacrylate; the catalyst is tetramethylethylenediamine; and the initiator is one or more of potassium persulfate and sodium persulfate.

[0019] Furthermore, the average particle size of the Si2N2O powder is less than 10 μm.

[0020] Furthermore, the mass ratio of the gel liquid to the initiator in S3 is 8:1.

[0021] A Si3N4-Si2N2O-based microwave-transparent ceramic material obtained by the above preparation method.

[0022] Compared with existing technologies, the beneficial effects are:

[0023] This invention utilizes Si powder and SiO powder reacted under normal pressure to generate Si2N2O powder, thereby improving the purity of Si2N2O powder and reducing dependence on equipment. The invention employs a gel-liquid system to ensure uniform dispersion of Si2N2O powder and sintering aids. The preform is pre-sintered and then sintered at 1450℃ under a N2 atmosphere, reducing Si2N2O decomposition. Simultaneously, the N2 environment inhibits the formation of lattice oxygen, transforming the pre-sintered Si3N4 into β-phase Si3N4, further enhancing the mechanical properties of Si3N4-Si2N2O-based microwave-transparent ceramics. Attached Figure Description

[0024] Figure 1 The XRD pattern of the Si3N4-Si2N2O high-temperature resistant microwave-transparent ceramic prepared in Example 1;

[0025] Figure 2 The image shows the SEM pattern of the high-temperature resistant microwave-transparent ceramic Si3N4-Si2N2O prepared in Example 1. Detailed Implementation

[0026] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application; however, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1

[0030] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0031] Preparation of S1 Si2N2O powder: Si powder and SiO powder with a molar ratio of 1:1 were uniformly mixed in a planetary ball mill and then placed in a tube furnace. The gas pressure inside the corundum tube was evacuated to -0.25MPa and then N2 was introduced to return it to normal pressure. The sintering parameters were as follows: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature in the furnace, coarse powder was obtained. The coarse powder and alcohol were ball-milled in a ball mill jar at a mass ratio of 1:2 and the dispersant content was 2wt.%. After that, the powder was dried and sieved.

[0032] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0033] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0034] S4 Dehydration, Degreasing, and Introduction of Si3N4: Slowly dehydrate and remove some lipids at 40-160℃ for 10h; heat at a rate of 5℃ / min, and hold at 200-400℃ and 420-800℃ twice to ensure complete degreasing; heat at a rate of 5℃ / min to 1200℃ and hold for 1h to introduce Si3N4 and maintain a certain strength in the green body, then cool to room temperature with the furnace.

[0035] S5 High-Temperature Sintering: Sintering is carried out at atmospheric pressure at 1400℃~1600℃ under N2 atmosphere protection at 0.05MPa. The temperature is increased to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min, and held for 2 hours.

[0036] Example 2

[0037] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0038] Preparation of S1 Si2N2O powder: Si powder and SiO powder with a molar ratio of 2:1 were uniformly mixed in a planetary ball mill and then placed in a tube furnace. The gas pressure inside the corundum tube was evacuated to -0.25MPa and then N2 was introduced to return it to normal pressure. The sintering parameters were as follows: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature in the furnace, coarse powder was obtained. The coarse powder and alcohol were ball-milled in a ball mill jar at a mass ratio of 1:2 and the dispersant content was 2wt.%. After that, the powder was dried and sieved.

[0039] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0040] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0041] S4 Dehydration, Degreasing, and Introduction of Si3N4: Slowly dehydrate and remove some lipids at 40-160℃ for 10h; heat at a rate of 5℃ / min, and hold at 200-400℃ and 420-800℃ twice to ensure complete degreasing; heat at a rate of 5℃ / min to 1200℃ and hold for 1h to introduce Si3N4 and maintain a certain strength in the green body, then cool to room temperature with the furnace.

[0042] S5 High-Temperature Sintering: Sintering is carried out at atmospheric pressure at 1400℃~1600℃ under N2 atmosphere protection at 0.05MPa. The temperature is increased to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min, and held for 2 hours.

[0043] Example 3

[0044] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0045] Preparation of S1 Si2N2O powder: Si powder and SiO powder with a molar ratio of 1:2 were uniformly mixed in a planetary ball mill and then placed in a tube furnace. The gas pressure inside the corundum tube was evacuated to -0.25MPa and then N2 was introduced to return it to normal pressure. The sintering parameters were as follows: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature in the furnace, coarse powder was obtained. The coarse powder and alcohol were ball-milled in a ball mill jar at a mass ratio of 1:2 and the dispersant content was 2wt.%. After that, the powder was dried and sieved.

[0046] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0047] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0048] S4 Dehydration, Degreasing, and Introduction of Si3N4: Slowly dehydrate and remove some lipids at 40-160℃ for 10h; heat at a rate of 5℃ / min, and hold at 200-400℃ and 420-800℃ twice to ensure complete degreasing; heat at a rate of 5℃ / min to 1200℃ and hold for 1h to introduce Si3N4 and maintain a certain strength in the green body, then cool to room temperature with the furnace.

[0049] S5 High-Temperature Sintering: Sintering is carried out at atmospheric pressure at 1400℃~1600℃ under N2 atmosphere protection at 0.05MPa. The temperature is increased to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min, and held for 2 hours.

[0050] Example 4

[0051] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0052] Preparation of S1 Si2N2O powder: Si powder and SiO powder with a molar ratio of 1:1 were uniformly mixed in a planetary ball mill and then placed in a tube furnace. The gas pressure inside the corundum tube was evacuated to -0.25MPa and then N2 was introduced to return it to normal pressure. The sintering parameters were as follows: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature in the furnace, coarse powder was obtained. The coarse powder and alcohol were ball-milled in a ball mill jar at a mass ratio of 1:2 and the dispersant content was 2wt.%. After that, the powder was dried and sieved.

[0053] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0054] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0055] S4 Dehydration and Degreasing: Slow dehydration and partial lipid removal at 40-160℃ for 10 hours; heating rate 5℃ / min, and holding at 200-400℃ and 420-800℃ twice respectively to ensure complete degreasing.

[0056] S5 High-Temperature Sintering: Sintering is carried out under normal pressure in N2 atmosphere protection at 0.05MPa, with a heating rate of 5℃ / min to 600℃, a heating rate of 10℃ / min to 1000℃, and a heating rate of 5℃ / min to 1450℃ and held for 2 hours.

[0057] Example 5

[0058] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0059] Preparation of Si2N2O powder: Si3N4 powder and Si powder with a molar ratio of 1:1 were placed in a muffle furnace under air atmosphere: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature with the furnace, coarse powder was obtained. Alcohol and dispersant were added and ball milled in a ball mill jar. Then the powder was dried and sieved.

[0060] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0061] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0062] S4 Dehydration, Degreasing, and Introduction of Si3N4: Slowly dehydrate and remove some lipids at 40-160℃ for 10h; heat at a rate of 5℃ / min, and hold at 200-400℃ and 420-800℃ twice to ensure complete degreasing; heat at a rate of 5℃ / min to 1200℃ and hold for 1h to introduce Si3N4 and maintain a certain strength in the green body, then cool to room temperature with the furnace.

[0063] S5 High-Temperature Sintering: Sintering is carried out at atmospheric pressure at 1400℃~1600℃ under N2 atmosphere protection at 0.05MPa. The temperature is increased to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min, and held at that temperature for 2 hours.

[0064] Example 6

[0065] This embodiment provides a method for preparing Si3N4-Si2N2O-based microwave-transparent ceramics, including the following steps:

[0066] Preparation of S1 Si2N2O powder: Si powder and SiO powder with a molar ratio of 1:1 were uniformly mixed in a planetary ball mill and then placed in a tube furnace. The gas pressure inside the corundum tube was evacuated to -0.25MPa and then N2 was introduced to return it to normal pressure. The sintering parameters were as follows: the temperature was raised to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min and held for 2 hours. After cooling to room temperature in the furnace, coarse powder was obtained. The coarse powder and alcohol were ball-milled in a ball mill jar at a mass ratio of 1:2 and the dispersant content was 2wt.%. After that, the powder was dried and sieved.

[0067] S2 gel-liquid process for dispersing and homogenizing Si2N2O powder: 5 wt.% MgO and 9 wt.% Y2O3 are added; monomers are acrylic acid (AA) and dimethacrylamide (DMAA); crosslinking agent is N,N-methyleneacrylamide (MBAM); initiator is one or more of ammonium sulfate (APS) and redox initiator (sodium metabisulfite); dispersant is polyethylene glycol (PEG400), polyethylene glycol (PEG1000), and ammonium polyacrylate (NH4PAA). The total organic matter accounts for 20 wt.% of the powder mass. Finally, Si2N2O powder and sintering aids are added to the organic mixture and mixed evenly in a heated stirring device to form a gel state.

[0068] S3 molding: Add initiator (1:1 ratio, total amount 1wt.%) potassium persulfate and sodium persulfate, catalyst (1wt.%) tetramethylethylenediamine, and heat to 50°C to mix; finally, cast into a block.

[0069] S4 Dehydration, Degreasing, and Introduction of Si3N4: Slowly dehydrate and remove some lipids at 40-160℃ for 10h; heat at a rate of 5℃ / min, and hold at 200-400℃ and 420-800℃ twice to ensure complete degreasing; heat at a rate of 5℃ / min to 1300℃ and hold for 2h to introduce Si3N4 and maintain a certain strength in the green body, then cool to room temperature with the furnace.

[0070] S5 High-Temperature Sintering: Sintering is carried out at atmospheric pressure at 1400℃~1600℃ under N2 atmosphere protection at 0.05MPa. The temperature is increased to 600℃ at a heating rate of 5℃ / min, to 1000℃ at a heating rate of 10℃ / min, and to 1450℃ at a heating rate of 5℃ / min, and held for 2 hours.

[0071] The Si3N4-Si2N2O-based microwave-transparent ceramics prepared in steps 1 to 6 were subjected to performance tests, and the various properties are shown in Table 1.

[0072] Table 1

[0073] Example 1 408 4.0 3.2 Example 2 417 4.3 3.4 Example 3 368 4.5 3.7 Example 4 386 5.0 3.9 Example 5 421 4.6 3.7 Example 6 435 4.7 3.8

[0074] From Table 1 and Figure 1 As can be seen, in Example 1, Si2N2O powder was prepared by sintering Si powder and SiO powder, and then dispersed and homogenized to form a gel liquid. An initiator was then added to the gel liquid, and a physicochemical reaction occurred in situ within the corresponding mold cavity to form a high-strength green body. This green body was then pre-sintered to allow a small portion of Si2N2O to decompose into Si3N4. Finally, it was sintered at high temperature and normal pressure under a nitrogen atmosphere to suppress the decomposition of Si2N2O and densify it, thus obtaining Si3N4-Si2N2O high-temperature transparent ceramic with good mechanical properties and high bending strength.

[0075] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering, characterized in that, Includes the following steps: S1. The raw materials Si powder and SiO powder are uniformly mixed according to the mass ratio, vacuumed, and then N2 is introduced. After sintering at 1400~1450℃, coarse powder is obtained. Then, alcohol and dispersant are added and ground to obtain Si2N2O powder. The sintering stage includes: evacuating the gas pressure to -0.25MPa and then introducing N2 to return it to normal pressure. The sintering temperature is increased to 550~600℃ at a heating rate of 3~7℃ / min, to 950~1000℃ at a heating rate of 10℃ / min, and to 1400℃~1450℃ at a heating rate of 5℃ / min, and held at that temperature for 1~2h. S2. Mix Si2N2O powder and sintering aid with organic matter to form a gel-like liquid; S3. Add an initiator to the gel liquid to form a preform; S4. Pre-sintering treatment of the green body: heating from 40℃ to 150~160℃ at a heating rate of 0.5~3℃ / min, holding for 10~20min; heating from 200℃ to 350~400℃ at a heating rate of 3~7℃ / min, holding for 20~30min; heating from 420℃ to 750~800℃ at a heating rate of 3~7℃ / min, holding for 10~20min; heating at a rate of 3~7℃ / min, and finally holding at 1100~1300℃ for 0.5~1h. S5. The pre-sintered green body is subjected to high-temperature atmospheric pressure sintering: under N2 atmosphere protection at 0.02~0.05MPa, the temperature is raised to 550~600℃ at a heating rate of 3~7℃ / min; to 950~1000℃ at a heating rate of 10℃ / min; and to 1400℃~1600℃ at a heating rate of 3~7℃ / min, and held for 1~2h.

2. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 1, characterized in that, The amount of dispersant added in step S1 is 2 wt.%.

3. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 1, characterized in that, In step S1, the mass ratio of Si powder, SiO powder, and alcohol is 1:1:

2.

4. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 1, characterized in that, The sintering aids contain 5 wt.% MgO, 9 wt.% Y2O3, and 20 wt.% organic matter.

5. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 4, characterized in that, The organic compounds are monomers, crosslinking agents, dispersants, initiators, and catalysts, with a mass ratio of 8:8:2:1:

1.

6. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 5, characterized in that, The monomer is one or more of acrylic acid and dimethylacrylamide; the crosslinking agent is N,N-methyleneacrylamide; the dispersant is one or more of polyethylene glycol and ammonium polyacrylate; the catalyst is tetramethylethylenediamine; and the initiator is one or more of potassium persulfate and sodium persulfate.

7. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 1, characterized in that, The average particle size of the Si2N2O powder is less than 10 μm.

8. The method for preparing Si3N4-Si2N2O-based microwave-transparent ceramic materials by atmospheric pressure sintering according to claim 1, characterized in that, The mass ratio of gel liquid to initiator in S3 is 8:

1.

9. The Si3N4-Si2N2O-based microwave-transparent ceramic material obtained by the preparation method according to any one of claims 1 to 8.

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