Method for sintering β-silicon nitride ceramics under normal pressure and low temperature

A low-temperature sintering technology for silicon nitride ceramics, applied in the field of ceramic sintering, can solve the problems of material fracture source, abnormal particle growth, dislocation, etc., and achieve the effect of reducing equipment cost, low equipment requirements, and superior performance

Active Publication Date: 2011-12-14
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 85% by weight of β-silicon nitride powder and 15% by weight of sintering aid to obtain mixed powder; 25% by weight of MgO and CeO in the sintering aid 2 20wt%, AlPO 4 10wt%, Y 2 O 3 10wt%, Li 2 CO 3 35wt%; put the mixed powder into a high-efficiency grinder and add tap water to grind for 1 hour, then dry the slurry for use; add polyvinyl alcohol to the dried slurry (amount: powder: polyvinyl alcohol = 100 :1 weight ratio) is formulated into uniform slurry; uniform slurry is sprayed and granulated by a spray granulator and passed through a 200-mesh sieve for use; the powder obtained after granulation is put into a mold, and a cold isostatic press is used 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 debinding molded body into a molybdenum crucible, and place it in a molybdenum crucible. Bare firing in a nitrogen high-temperature furnace, holding ...

Embodiment 2

[0029] Example 2: Mix 90wt% of β-silicon nitride powder with 10wt% of sintering aid to obtain mixed powder; in the sintering aid, 35wt% of MgO, CeO 2 10wt%, AlPO 4 5wt%, Y 2 O 3 20wt%, Li 2 CO 3 30wt%; put the mixed powder into a high-efficiency grinder and add tap water to grind for 2h, and then dry the slurry for use; add polyvinyl alcohol to the dried slurry (amount: powder: polyvinyl alcohol = 100 : 0.5 weight ratio) is formulated into uniform slurry; uniform slurry is sprayed and granulated by spray granulator, and then passed through a 200-mesh sieve for use; the powder obtained after granulation is put into a mold, and a cold isostatic press is used Press molding into a molded body with a molding pressure of 250Mpa; put the molded body into a debinding furnace at 600°C for 2 hours; put the discharged molded body into a molybdenum crucible, and place it in a molybdenum crucible. Bare firing in a nitrogen high-temperature furnace, holding at 1600°C for 2h; β-silicon nit...

Embodiment 3

[0031] Example 3: Mix 95wt% of β-silicon nitride powder with 5wt% of sintering aid to obtain mixed powder; in the sintering aid, 33wt% of MgO, CeO 2 17wt%, AlPO 4 7wt%, Y 2 O 3 18wt%, Li 2 CO 3 25wt%; put the mixed powder into a high-efficiency grinder and add tap water to grind for 3 hours, and then dry the slurry for use; add the above-mentioned dried slurry to polyvinyl alcohol (amount: powder: polyvinyl alcohol = 100: 2 Weight ratio) is formulated into a uniform slurry; the uniform slurry is sprayed and granulated by a spray granulator and passed through a 200-mesh sieve for use; the powder obtained after granulation is put into a mold and pressed by a cold isostatic press Shaped into a shaped body with a molding pressure of 230Mpa; put the shaped body into a debinding furnace for debinding at 800°C for 0.5 hours; put the debinding shaped body into a molybdenum crucible, in the presence of atmospheric nitrogen It is bare-fired in a high-temperature furnace and kept at 15...

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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 method for sintering ceramics, 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 The special ceramic material with the main crystalline phase is an ideal high-temperature structural material and tool material. It has 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 the fields of machinery, metallurgy, chemicals, automobiles, aerospace and aviation. [0003] As Si 3 N 4 It is a strong covalent bond, low self-diffusion coefficient, and easy to decompose above 1800 ℃, pure silicon nitride is difficult to sinter and densify. Currently, α-Si is commonly used in silicon nitride products 3 N 4 S...

Claims

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Application Information

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Patent Type & Authority Applications(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
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