CN115536403A - High-toughness silicon nitride ceramic material and preparation method thereof - Google Patents

High-toughness silicon nitride ceramic material and preparation method thereof Download PDF

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CN115536403A
CN115536403A CN202211159641.2A CN202211159641A CN115536403A CN 115536403 A CN115536403 A CN 115536403A CN 202211159641 A CN202211159641 A CN 202211159641A CN 115536403 A CN115536403 A CN 115536403A
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silicon nitride
sintering
ceramic material
toughness
temperature
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肖亮
谭庆文
谭浩文
钱利洪
谢庆忠
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Hengyang Kaixin Special Materials Technology Co ltd
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Hengyang Kaixin Special Materials Technology Co ltd
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Abstract

The invention belongs to the technical field of ceramic materials, and provides a high-toughness silicon nitride ceramic material and a preparation method thereof. The invention firstly carries out heat treatment on the silicon nitride to coat a layer of SiO with oxide characteristic on the surface of the silicon nitride 2 The film promotes the sintering densification and improves the ceramic performance, then the thermal oxidation silicon nitride, the reinforced phase and the sintering aid are made into a green body, wherein the sintering aid is used for promoting the densification and ensuring the hardness of the ceramic material, the reinforced phase is used for improving the toughness of the silicon nitride ceramic material, and finally, the sintering mode combining high-temperature sintering and low-temperature sintering is adopted, so that the crystal boundary migration can be inhibited, and the green body is densified by utilizing crystal boundary diffusion, thereby ensuring the hardness of the ceramic material. Practice ofThe results of the examples show that the Vickers hardness of the high-toughness silicon nitride ceramic material prepared by the preparation method provided by the invention can reach 22.7GPa, and the fracture toughness can reach 16.7 MPa.m 1/2 。

Description

High-toughness silicon nitride ceramic material and preparation method thereof
Technical Field
The invention relates to the technical field of ceramic materials, in particular to a high-toughness silicon nitride ceramic material and a preparation method thereof.
Background
The silicon nitride ceramic has excellent high-temperature performance, chemical stability and mechanical properties, wherein the mechanical properties comprise high bending strength and fracture toughness, good thermal shock resistance, low high-temperature creep property and the like, and is an ideal engineering ceramic material and widely applied to the fields of machinery, chemical engineering, aerospace, national defense and military industry and the like.
In recent years, silicon nitride ceramics have high theoretical thermal conductivity, and thus become a candidate material for a heat dissipation substrate for a high-power electronic device. At present, the silicon nitride ceramic with high thermal conductivity is prepared by adopting a reaction re-sintering technology (SRBSN), but higher hardness and toughness cannot be obtained simultaneously. Furthermore, although the properties of the silicon nitride ceramic can be controlled by adjusting the material composition and sintering temperature, the high content of α -Si 3 N 4 Or high content of beta-Si 3 N 4 The materials cannot give consideration to both high hardness and high toughness. Therefore, how to prepare a silicon nitride ceramic material with high toughness while ensuring hardness becomes a technical problem to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a high-toughness silicon nitride ceramic material and a preparation method thereof.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a preparation method of a high-toughness silicon nitride ceramic material, which comprises the following steps:
(1) Carrying out heat treatment on the silicon nitride to obtain thermal oxidation silicon nitride;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1), a reinforcing phase and a sintering aid, and then forming to obtain a blank;
(3) Sequentially carrying out high-temperature sintering and low-temperature sintering on the blank obtained in the step (2) to obtain a high-toughness silicon nitride ceramic material; the temperature of the high-temperature sintering is 1800-1900 ℃, and the temperature of the low-temperature sintering is 1600-1700 ℃.
Preferably, the silicon nitride in the step (1) contains alpha-Si 3 N 4 Quality of (1)The content is more than or equal to 90 percent, and the average grain diameter D50 of the silicon nitride is less than or equal to 0.8 mu m.
Preferably, the temperature of the heat treatment in the step (1) is 1150-1250 ℃, and the time of the heat treatment is 1-3 h.
Preferably, the mass content of the thermally oxidized silicon nitride in the blank in the step (2) is 79-92%, the mass content of the reinforcing phase is 3-6%, and the mass content of the sintering aid is 5-15%.
Preferably, the reinforcing phase in step (2) includes one or more of carbon fiber, graphene and carbon nanotube.
Preferably, the sintering aid in step (2) comprises a metal oxide and a rare earth oxide.
Preferably, the metal oxide comprises magnesium oxide and aluminum oxide, and the rare earth oxide comprises yttrium oxide, lanthanum oxide or cerium oxide.
Preferably, the forming in step (2) comprises dry pressing and/or cold isostatic pressing.
Preferably, the heat preservation time of the high-temperature sintering in the step (3) is 10-30 min, and the sintering pressure of the high-temperature sintering is 6-12 MPa; the heat preservation time of the low-temperature sintering is 30-90 min, and the sintering pressure of the low-temperature sintering is 2-3 MPa.
The invention also provides the high-toughness silicon nitride ceramic material prepared by the preparation method in the technical scheme.
The invention provides a preparation method of a high-toughness silicon nitride ceramic material, which comprises the following steps: (1) Carrying out heat treatment on the silicon nitride to obtain thermal oxidation silicon nitride; (2) Mixing the thermal oxidation silicon nitride obtained in the step (1), a reinforcing phase and a sintering aid, and then forming to obtain a blank; (3) Sequentially carrying out high-temperature sintering and low-temperature sintering on the blank obtained in the step (2) to obtain a high-toughness silicon nitride ceramic material; the temperature of the high-temperature sintering is 1800-1900 ℃, and the temperature of the low-temperature sintering is 1600-1700 ℃. The invention firstly carries out heat treatment on the silicon nitride to lead the silicon nitride surface to be coated with a layer of SiO with oxide characteristic 2 Film to promote densification by sintering and to improve ceramic properties, and then thermally oxidizing silicon nitride withThe reinforcing phase and the sintering aid are made into a green body, wherein the sintering aid is used for promoting densification and ensuring the hardness of the ceramic material, the reinforcing phase is used for improving the toughness of the silicon nitride ceramic material, and finally, a sintering mode combining high-temperature sintering and low-temperature sintering is adopted, so that the grain boundary migration can be inhibited, and the green body is densified by using grain boundary diffusion, thereby ensuring the hardness of the ceramic material. The results of the examples show that the Vickers hardness of the high-toughness silicon nitride ceramic material prepared by the preparation method provided by the invention can reach 22.7GPa, and the fracture toughness can reach 16.7 MPa.m 1/2 。
Detailed Description
The invention provides a preparation method of a high-toughness silicon nitride ceramic material, which comprises the following steps:
(1) Carrying out heat treatment on the silicon nitride to obtain thermal oxidation silicon nitride;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1), a reinforcing phase and a sintering aid, and then forming to obtain a blank;
(3) Sequentially carrying out high-temperature sintering and low-temperature sintering on the blank obtained in the step (2) to obtain a high-toughness silicon nitride ceramic material; the temperature of the high-temperature sintering is 1800-1900 ℃, and the temperature of the low-temperature sintering is 1600-1700 ℃.
The invention carries out heat treatment on the silicon nitride to obtain the thermal oxidation silicon nitride. The invention carries out heat treatment on the silicon nitride, so that the surface of the silicon nitride is coated with a layer of SiO with oxide characteristic 2 The film promotes sintering densification and improves ceramic performance.
In the present invention, α -Si in the silicon nitride 3 N 4 The mass content of (B) is preferably not less than 90%, more preferably not less than 95%. The invention preferably adds alpha-Si in the silicon nitride 3 N 4 The mass content of (a) is controlled within the above range, which is advantageous for forming uniform and fine equiaxed grains in the sintered silicon nitride. In the present invention, the average particle diameter D50 of the silicon nitride is preferably not more than 0.8 μm, and in the present invention, it is preferable to control the average particle diameter of the silicon nitride within the above range, so that the sintering densification can be prevented from being inhibited and the hardness of the material can be prevented from being affected when the average particle diameter of the silicon nitride is too large. The invention is used for the source of the silicon nitrideThe solvent is not particularly limited, and a commercially available product known to those skilled in the art may be used.
In the present invention, the temperature of the heat treatment is preferably 1150 to 1250 ℃, more preferably 1200 to 1250 ℃; the time for the heat treatment is preferably 1 to 3 hours, more preferably 2 to 3 hours. The invention preferably controls the temperature and the time of the heat treatment within the range, thereby ensuring the SiO on the silicon nitride surface 2 And (4) forming a film.
After the thermal oxidation silicon nitride is obtained, the thermal oxidation silicon nitride, the reinforcing phase and the sintering aid are mixed and then molded to obtain a blank.
In the present invention, the mass content of the thermally oxidized silicon nitride in the green body is preferably 79 to 92%, more preferably 80 to 90%.
In the present invention, the mass content of the reinforcing phase in the green body is preferably 3 to 6%, more preferably 4 to 5%. In the present invention, the reinforcing phase preferably includes one or more of carbon fiber, graphene and carbon nanotube, and more preferably carbon fiber and/or graphene. The use of the reinforcing phase in the invention is beneficial to improving the toughness of the silicon nitride ceramic material. The source of the reinforcing phase is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
In the present invention, the mass content of the sintering aid in the green body is preferably 5 to 15%, more preferably 6 to 12%. In the present invention, the sintering aid preferably includes a metal oxide and a rare earth oxide. The sintering aid is used for promoting densification and ensuring the hardness of the ceramic material. In the present invention, the mass ratio of the metal oxide to the rare earth oxide is preferably 1 (1 to 2). In the present invention, the metal oxide preferably includes magnesium oxide and aluminum oxide. In the present invention, the magnesium oxide and the aluminum oxide are added in an arbitrary ratio. In the present invention, the rare earth oxide preferably includes yttrium oxide, lanthanum oxide, or cerium oxide, and more preferably yttrium oxide or cerium oxide. The source of the sintering aid is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
In the present invention, the shaping means preferably comprises dry pressing and/or cold isostatic pressing, more preferably cold isostatic pressing.
After the green body is obtained, the high-toughness silicon nitride ceramic material is obtained by sequentially carrying out high-temperature sintering and low-temperature sintering on the green body. The invention adopts a sintering mode combining high-temperature sintering and low-temperature sintering, can inhibit grain boundary migration, and utilizes grain boundary diffusion to densify the blank, thereby ensuring the hardness of the ceramic material.
In the invention, the temperature of the high-temperature sintering is 1800-1900 ℃, preferably 1850-1880 ℃; the temperature of the low-temperature sintering is 1600-1700 ℃, preferably 1650-1680 ℃. According to the invention, the temperature of high-temperature sintering and low-temperature sintering is controlled within the range, so that the full sintering of the ceramic material is ensured, the densification is improved, and the ceramic material with excellent hardness can be obtained.
In the invention, the heat preservation time of the high-temperature sintering is preferably 10-30 min, and more preferably 10-20 min; the sintering pressure of the high-temperature sintering is preferably 6-12 MPa, and more preferably 8-10 MPa; the heat preservation time of the low-temperature sintering is preferably 30-90 min, and more preferably 40-80 min; the sintering pressure for the low-temperature sintering is preferably 2 to 3MPa, and more preferably 2 to 2.5MPa. The invention preferably controls the time and pressure of high-temperature sintering and low-temperature sintering within the range, thereby ensuring the full sintering of the ceramic material.
The invention firstly carries out heat treatment on the silicon nitride to lead the silicon nitride surface to be coated with a layer of SiO with oxide characteristic 2 The method comprises the steps of preparing a film, promoting sintering densification and improving the ceramic performance, preparing a blank from thermal oxidation silicon nitride, a reinforcing phase and a sintering aid, wherein the sintering aid is used for promoting densification and ensuring the hardness of the ceramic material, the reinforcing phase is used for improving the toughness of the silicon nitride ceramic material, and finally adopting a sintering mode combining high-temperature sintering and low-temperature sintering to inhibit grain boundary migration and densify the blank by utilizing grain boundary diffusion so as to ensure the hardness of the ceramic material.
The invention also provides the high-toughness silicon nitride ceramic material prepared by the preparation method in the technical scheme. The high-toughness silicon nitride ceramic material provided by the invention has excellent toughness and hardness.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Treating silicon nitride at 1150 deg.c for 2 hr to obtain thermally oxidized silicon nitride; wherein, alpha-Si in the silicon nitride 3 N 4 The mass content of the particles is more than or equal to 98 percent, and the average particle size D50 is 0.7 mu m;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1) with a reinforcing phase and a sintering aid, and then carrying out cold isostatic pressing to obtain a blank; wherein the mass content of the thermal oxidation silicon nitride in the blank is 85%, the mass content of the reinforcing phase is 5%, and the mass content of the sintering aid is 10%; the reinforcing phase is carbon fiber, the sintering aid is magnesium oxide, aluminum oxide and yttrium oxide, and the mass ratio of the total mass of the magnesium oxide and the aluminum oxide to the yttrium oxide is 1:2;
(3) And (3) sintering the blank obtained in the step (2) at 1850 ℃ for 10min under 8MPa, then cooling to 1650 ℃, keeping the sintering pressure at 2MPa for 40min, and then naturally cooling to obtain the high-toughness silicon nitride ceramic material.
Example 2
(1) Treating silicon nitride at 1150 deg.c for 2 hr to obtain thermally oxidized silicon nitride; wherein, alpha-Si in the silicon nitride 3 N 4 The mass content of the particles is more than or equal to 98 percent, and the average particle size D50 is 0.7 mu m;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1) with a reinforcing phase and a sintering aid, and then carrying out cold isostatic pressing to obtain a blank; wherein the mass content of the thermal oxidation silicon nitride in the blank body is 90%, the mass content of the reinforcing phase is 3%, and the mass content of the sintering aid is 7%; the reinforcing phase is a carbon nano tube, the sintering aid is magnesium oxide, aluminum oxide and cerium oxide, and the mass ratio of the total mass of the magnesium oxide and the aluminum oxide to the cerium oxide is 1:1;
(3) And (3) sintering the blank obtained in the step (2) at 1850 ℃ for 10min under 8MPa, then cooling to 1650 ℃, keeping the sintering pressure at 2MPa for 40min, and then naturally cooling to obtain the high-toughness silicon nitride ceramic material.
Example 3
(1) Treating silicon nitride at 1200 ℃ for 2h to obtain thermal oxidation silicon nitride; wherein, alpha-Si in the silicon nitride 3 N 4 The mass content of the nano-particles is more than or equal to 98 percent, and the average particle size D50 is 0.7 mu m;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1) with a reinforcing phase and a sintering aid, and then carrying out cold isostatic pressing to obtain a blank; wherein the mass content of the thermal oxidation silicon nitride in the blank body is 88 percent, the mass content of the reinforcing phase is 6 percent, and the mass content of the sintering aid is 6 percent; the reinforcing phase is carbon fiber, the sintering aid is magnesium oxide, aluminum oxide and yttrium oxide, and the mass ratio of the total mass of the magnesium oxide and the aluminum oxide to the yttrium oxide is 1:2;
(3) And (3) sintering the blank obtained in the step (2) at 1880 ℃ under 10MPa for 10min, then cooling to 1680 ℃, keeping the sintering pressure at 2.5MPa for 40min, and then naturally cooling to obtain the high-toughness silicon nitride ceramic material.
The high toughness silicon nitride ceramic materials prepared in examples 1 to 3 were tested for vickers hardness and fracture toughness by the indentation method with an applied load of 196N, and the test results are shown in table 1.
TABLE 1 Vickers hardness and fracture toughness of high toughness silicon nitride ceramic materials prepared in examples 1-3
Example 1 Example 2 Example 3
Vickers hardness (GPa) 24.2 22.7 23.6
Fracture toughness (MPa. M) 1/2 ) 15.3 16.7 15.9
The embodiment shows that the high-toughness silicon nitride ceramic material prepared by the preparation method provided by the invention has excellent hardness and fracture toughness, the Vickers hardness can reach 22.7GPa, and the fracture toughness can reach 16.7 MPa.m 1/2 。
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a high-toughness silicon nitride ceramic material comprises the following steps:
(1) Carrying out heat treatment on the silicon nitride to obtain thermal oxidation silicon nitride;
(2) Mixing the thermal oxidation silicon nitride obtained in the step (1), a reinforcing phase and a sintering aid, and then forming to obtain a blank;
(3) Sequentially carrying out high-temperature sintering and low-temperature sintering on the blank obtained in the step (2) to obtain a high-toughness silicon nitride ceramic material; the temperature of the high-temperature sintering is 1800-1900 ℃, and the temperature of the low-temperature sintering is 1600-1700 ℃.
2. According to claimThe method according to 1, wherein the step (1) is performed using α -Si in the silicon nitride 3 N 4 The mass content of the silicon nitride is more than or equal to 90 percent, and the average grain diameter D50 of the silicon nitride is less than or equal to 0.8 mu m.
3. The preparation method according to claim 1, wherein the temperature of the heat treatment in the step (1) is 1150-1250 ℃ and the time of the heat treatment is 1-3 h.
4. The preparation method according to claim 1, wherein the mass content of the thermally oxidized silicon nitride in the green body in the step (2) is 79 to 92%, the mass content of the reinforcing phase is 3 to 6%, and the mass content of the sintering aid is 5 to 15%.
5. The preparation method according to claim 1 or 4, wherein the reinforcing phase in the step (2) comprises one or more of carbon fiber, graphene and carbon nanotube.
6. The production method according to claim 1 or 4, wherein the sintering aid in the step (2) includes a metal oxide and a rare earth oxide.
7. The method according to claim 6, wherein the metal oxide comprises magnesium oxide and aluminum oxide, and the rare earth oxide comprises yttrium oxide, lanthanum oxide, or cerium oxide.
8. The method according to claim 1, wherein the forming in the step (2) comprises dry pressing and/or cold isostatic pressing.
9. The preparation method according to claim 1, wherein the holding time of the high-temperature sintering in the step (3) is 10 to 30min, and the sintering pressure of the high-temperature sintering is 6 to 12MPa; the heat preservation time of the low-temperature sintering is 30-90 min, and the sintering pressure of the low-temperature sintering is 2-3 MPa.
10. A high toughness silicon nitride ceramic material prepared by the preparation method of any one of claims 1 to 9.
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CN116283307A (en) * 2023-02-24 2023-06-23 衡阳凯新特种材料科技有限公司 Nanometer complex phase ceramic material and preparation method and application thereof
CN116553936A (en) * 2023-04-17 2023-08-08 衡阳凯新特种材料科技有限公司 Ultrahigh-temperature vacuum-resistant silicon nitride ceramic material and preparation method thereof

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CN111285692A (en) * 2020-02-21 2020-06-16 武汉理工大学 High-thermal-conductivity Si3N4Ceramic and preparation method thereof
CN111517806A (en) * 2020-04-26 2020-08-11 中国科学院上海硅酸盐研究所 High-toughness silicon nitride ceramic and preparation method thereof

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