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Atmospheric-pressure and low-temperature sintering method of beta-silicon nitride ceramic

A low-temperature sintering technology for silicon nitride ceramics, applied in the sintering field of ceramics, can solve problems such as material fracture sources, abnormal particle growth, and dislocation, and achieve the effects of reducing equipment costs, low equipment requirements, and cost reduction

Active Publication Date: 2013-05-08
中国科学院唐山高新技术研究与转化中心
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the abnormal growth of particles must be controlled during sintering, otherwise defects such as pores, cracks, and dislocations will occur, and these defects are likely to become the source of fracture of the material
Due to the complexity of the phase transition, the abnormal growth of grains is difficult to be effectively controlled
Therefore, it is difficult to guarantee the uniformity and repeatability of the materials obtained by sintering with high α-phase powder
Currently pure α-Si 3 N 4 The sintering technology of powder at high temperature has been mature, and pure β-Si 3 N 4 There is no report on sintering silicon nitride ceramics within 1600 °C under the protection of atmospheric nitrogen

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Example 1: Mix 85wt% of β-silicon nitride powder with 15wt% of sintering aid to obtain mixed powder; MgO 25wt% in sintering aid, CeO 2 20wt%, AlPO 4 10wt%, Y 2 o 3 10wt%, Li 2 CO 3 35wt%; the mixed powder was put into a high-efficiency grinder and added tap water to grind for 1h, then the slurry was dried for subsequent use; polyvinyl alcohol was added to the dried slurry (amount: powder: polyvinyl alcohol=100 : 1 weight ratio) to prepare a uniform slurry; the uniform slurry is sprayed and granulated by a spray granulator, and it is used after passing through a 200-mesh sieve; the powder obtained after granulation is loaded into a mold, and isostatically Press molding into a molded body with a molding pressure of 200Mpa; put the molded body into a debinding furnace for debinding at 700°C for 1 hour; put the degummed molded body into a molybdenum crucible, and place it under normal pressure Burn naked in a nitrogen high-temperature furnace, and keep it at 1550°C...

Embodiment 2

[0029] Example 2: Mix 90wt% of β-silicon nitride powder with 10wt% of sintering aid to obtain mixed powder; MgO 35wt% in sintering aid, CeO 2 10wt%, AlPO 4 5wt%, Y 2 o 3 20wt%, Li 2 CO 3 30wt%; the mixed powder was put into a high-efficiency grinder and added tap water to grind for 2 hours, then the slurry was dried for subsequent use; polyvinyl alcohol was added to the dried slurry (amount: powder: polyvinyl alcohol=100 : 0.5 weight ratio) to be prepared into a uniform slurry; the uniform slurry is sprayed and granulated by a spray granulator, and it is used after passing through a 200-mesh sieve; Press molding into a molded body with a molding pressure of 250Mpa; put the molded body in a debinding furnace for debinding at 600°C for 2 hours; put the degummed molded body into a molybdenum crucible, and place it under normal pressure Burn naked in a nitrogen high-temperature furnace, and keep it at 1600°C for 2 hours; you can get β-silicon nitride ceramics.

[0030] A...

Embodiment 3

[0031] Example 3: Mix 95wt% of β-silicon nitride powder with 5wt% of sintering aid to obtain mixed powder; MgO 33wt% in sintering aid, CeO 2 17wt%, AlPO 4 7wt%, Y 2 o 3 18wt%, Li 2 CO 3 25wt%; the mixed powder was put into a high-efficiency grinder and added tap water to grind for 3 hours, and then the slurry was dried for subsequent use; the above-mentioned dried slurry was added to polyvinyl alcohol (consumption: powder: polyvinyl alcohol = 100: 2 weight ratio) to prepare a uniform slurry; the uniform slurry is sprayed and granulated by a spray granulator, and is used after passing through a 200-mesh sieve; the powder obtained after granulation is put into a mold, and pressed by a cold isostatic press Form into a molded body with a molding pressure of 230Mpa; put the molded body into a debinding furnace and debind at 800°C for 0.5 hours; put the degummed molded body into a molybdenum crucible, Baked firing in a high-temperature furnace, and heat preservation at 1500...

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Abstract

The invention discloses an atmospheric-pressure and low-temperature sintering method of beta-silicon nitride ceramic, comprising the following steps of: using beta-silicon nitride as a raw material, adding a sintering aid to prepare a mixed powder, and carrying out liquid phase sintering on the mixed powder at normal pressure and in nitrogen atmosphere. The sintering aid is made from the following components of: by weight, 25-35% of MgO, 10-20% of CeO2, 5-10% of AlPO4, 1-20% of Y2O3 and 25-35% of Li2CO3. The high-output beta-silicon nitride powder which is cheap and easily available is adopted in the invention; in comparison with an expensive high-purity alpha-silicon nitride powder, the beta-silicon nitride powder is used to greatly reduce the cost. By the liquid phase sintering at normal pressure and in nitrogen atmosphere with the sintering temperature being within 1600 DEG C, the method provided by the invention has low requirement of equipment so as to reduce the equipment cost. According to the silicon nitride ceramic obtained by the method, the relative density is larger than or equal to 98%, the bending strength ranges from 600Mpa to 700Mpa, and the indentation hardness reaches 7-8Gpa.

Description

technical field [0001] The invention relates to a ceramic sintering method, in particular to a method for sintering β-silicon nitride ceramics at normal pressure and low temperature. Background technique [0002] Silicon nitride ceramic is a kind of α-Si 3 N 4 and β-Si 3 N 4 Special ceramic material with main crystal phase, is an ideal high-temperature structural material and tool material, with a series of excellent properties, such as high strength, high toughness, corrosion resistance, high temperature resistance, oxidation resistance, low specific gravity and thermal shock resistance Wait. It has a wide range of application markets in machinery, metallurgy, chemical industry, automobile, aerospace and other fields. [0003] Since Si 3 N 4 It is a strong covalent bond, low self-diffusion coefficient, and easy to decompose above 1800 ° C. Pure silicon nitride is difficult to sinter and densify. At present, silicon nitride products generally use α-Si 3 N 4 Sintere...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B35/596C04B35/622
Inventor 刘得顺王福杨连弟王京甫徐锦标郭金砚邹艺峰
Owner 中国科学院唐山高新技术研究与转化中心