A kind of high beta phase dense silicon nitride ceramics and low temperature preparation method

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...

AI Technical Summary

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

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