High-beta-phase compact silicon nitride ceramic and low-temperature preparation method

A silicon nitride ceramic and dense technology, which is applied in the field of silicon nitride ceramics, can solve the problems of difficult solid-phase sintering, high sintering temperature, and reduced industrial production efficiency, so as to increase the content of β-silicon nitride phase and promote nitridation. Silicon phase transition, the effect of maintaining excellent performance

Active Publication Date: 2019-12-20
SINOSTEEL LUOYANG INST OF REFRACTORIES RES
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Problems solved by technology

The sintering preparation of dense silicon nitride ceramics has always been a research hotspot, because silicon nitride is a strong covalent bond material, which makes it difficult to sinter in the solid state, and it is necessary to add sintering aids to promote its sintering through the liquid phase as a mass transfer medium. Densification sintering; At present, the production of silicon nitride ceramic products mostly relies on high-cost sintering methods such as hot pressing and air pressure sintering. There is a transition from α phase to β phase, which has a decisive influence on the densification degree and the improvement of mechanical properties of silicon nitride ceramics, and it is difficult to complete a higher phase transition at low temperature, which greatly limits the Industrialized production and popular application of high-performance silicon nitride ceramics in many high-tech fields
[0003] Most of the preparation of silicon nitride is sintered by hot pressing or air pressure at high temperature: for example: Zhang Hui's patent "A Preparation Method for Densified Silicon Nitride Ceramic Material" (publication number CN103553632A) adopts a sintering temperature of 1750 ℃~1850℃, the high sintering temperature leads to a sharp increase in the required equipment and cost
Zhao Zhenwei's patent "a sintering method for improving the performance consistency of silicon nitride materials" (publication number CN104119079A) uses air pressure and hot pressing sintering methods, resulting in high production costs and low efficiency
Yu Fangli's patent "A Silicon Nitride Ceramic and Its Preparation Method" (publication number CN105859301A) adopts air pressure sintering method, and the sintering temperature also reaches 1800°C, resulting in high cost
[0004] Due to the high sintering temperature and harsh production equipment requirements of silicon nitride ceramics, its industrial production efficiency is greatly reduced. At present, there are very few related researches on the technology of preparing high-β-phase dense silicon nitride ceramics at low temperature. Therefore, a low-temperature preparation High-performance silicon nitride ceramic preparation technology becomes extremely important

Method used

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Experimental program
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Effect test

Embodiment 1

[0033] According to Li 2 O (raw material is Li 2 CO 3 ) and Al 2 o 3 The molar ratio is 1.02:1, and then ball milling is carried out on a planetary ball mill for 6 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 5:1.

[0034] The mixed powder after ball milling was dried and put into an alumina crucible for calcination at 1000°C for 2h.

[0035] The single-phase LiAlO obtained after calcination 2 Grind through 40 mesh sieve with Y 2 o 3 and Si 3 N 4 The powder is mixed according to the mass ratio of 10:2:88, and ball milled on a planetary ball mill for 24 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 5:1.

[0036] Then spray granulate the uniformly mixed powder, the process is N 2 Atmosphere, set the inlet temperature at 160°C and the outlet temperature at 80°C to obtain Si 3 N 4 Granulated powder.

[0037] The granulated Si 3 N 4 The powder is put into an isostatic pressing ...

Embodiment 2

[0041] According to Li 2 O (raw material is Li 2 CO 3 ) and Al 2 o 3 The molar ratio is 1.02:1, and then ball milling is carried out on a planetary ball mill for 6 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 7:1.

[0042] After ball milling, the mixed powder was dried and put into an alumina crucible for calcination at 900°C for 3h.

[0043] The single-phase LiAlO obtained after calcination 2 Crushed through 40 mesh sieve and Y 2 o 3 and Si 3 N 4 The powder is mixed according to the mass ratio of 8:4:88, and ball milled on a planetary ball mill for 24 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 7:1.

[0044] Then spray granulate the uniformly mixed powder, the process is N 2 Atmosphere, set the inlet temperature at 180°C and the outlet temperature at 90°C to obtain Si 3 N 4 Granulated powder.

[0045] The granulated Si 3 N 4 The powder is put into an isostatic pressing ...

Embodiment 3

[0049] According to Li 2 O (raw material is Li 2 CO 3 ) and Y 2 o 3 The molar ratio is 1.5:1, and then ball milling is carried out on a planetary ball mill for 12 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 10:1.

[0050] After the ball-milled sintering aid mixed powder is dried, it is put into an alumina crucible for calcination at 1300°C for 2 hours.

[0051] Calcined single-phase LiYO 2 Crushed through 40 mesh sieve with MgO and Si 3 N 4 The powder is mixed according to the mass ratio of 4:8:88, and ball milled on a planetary ball mill for 24 hours. The ball milling medium is silicon nitride balls, and the ball-to-material ratio is 10:1.

[0052] Then spray granulate the uniformly mixed powder, the process is N 2 Atmosphere, set the inlet temperature at 180°C and the outlet temperature at 90°C to obtain Si 3 N 4 Granulated powder.

[0053] The granulated Si 3 N 4 The powder is put into an isostatic pressing mold an...

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Abstract

The invention belongs to the technical field of silicon nitride ceramics, and relates to a high-beta-phase compact silicon nitride ceramic, and a low-temperature preparation method. The preparation raw materials of the high-beta-phase compact silicon nitride ceramic comprise Si3N4 powder and a sintering aid; the sintering aid is a composite sintering aid consisting of LixMOy type lithium salt andone or more other oxides; wherein the LixMOy type lithium salt is one selected from LiAlO2, LiYO2, LiNbO3, Li2ZrO3, LiYbO2 and Li2SiO3, and the other oxides are one or more selected from rare earth oxide or metal oxide, Y2O3, CeO2, Yb2O3, MgO, CaO and MgAl2O4; the mass ratio of the LixMOy type lithium salt to other oxides in the composite sintering aid is (4-12): (0-8); the mass ratio of the Si3N4powder to the composite sintering aid is (85-94): (6-15). According to the method, the sintering temperature is greatly reduced, volatilization of the silicon nitride ceramic is reduced, and the excellent performance of the silicon nitride ceramic is better maintained.

Description

technical field [0001] The invention belongs to the technical field of silicon nitride ceramics, and relates to a dense silicon nitride ceramic with high β phase content and a low-temperature preparation method. Background technique [0002] Silicon nitride ceramics have good wear resistance and corrosion resistance, high flexural strength, good fracture toughness, great hardness and high theoretical thermal conductivity (200–300Wm -1 ·K -1 ), and are therefore widely used in modern industries (automotive engine parts, nuclear reactor supports, knives, ceramic armor, and aerospace). The sintering preparation of dense silicon nitride ceramics has always been a research hotspot, because silicon nitride is a strong covalent bond material, which makes it difficult to sinter in the solid state, and it is necessary to add sintering aids to promote its sintering through the liquid phase as a mass transfer medium. Densification sintering; At present, the production of silicon nitr...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/584C04B35/622C04B35/64
CPCC04B35/584C04B35/622C04B35/64C04B2235/3203C04B2235/3208C04B2235/3217C04B2235/3225C04B2235/3244C04B2235/6562C04B2235/6567C04B2235/658C04B2235/668C04B2235/96
Inventor 赵世贤郭昂王战民李凌锋司瑶晨王刚李红霞
Owner SINOSTEEL LUOYANG INST OF REFRACTORIES RES
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