Method for preparing high-compactness silicon nitride ceramic by adding composite additives

A technology of silicon nitride ceramics and composite additives, applied in the field of ceramic materials, can solve the problems of high porosity, high cost, and complicated equipment, and achieve the effects of high bending strength, good compactness, and simple operation

Inactive Publication Date: 2016-05-04
HEBEI COREFRA SILICON NITRIDE MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Among them, hot isostatic pressing has high sintering pressure, complex equipment, strict production process requirements, low production efficiency and high cost.
Silicon nitride ceramics produced by reaction sintering have poor density and high porosity, and there will be residual unreacted substances in the product

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] 1 g of polyvinyl alcohol (88% degree of alcoholysis) was prepared into 10 mL of polyvinyl alcohol solution by heating and stirring. Put 82g of silicon nitride (D50=0.45μm, α=94.2%), 10g of alumina, 8g of yttrium oxide, 0.04g of tributyl phosphate solution, 90mL of deionized water, and 10mL of the above-mentioned polyvinyl alcohol solution into a ball mill jar. Put the ball mill pot into a planetary ball mill and mix evenly, the speed is 580r / min, and the ball milling time is 2h.

[0018] Put the homogeneously mixed slurry into a drying oven for drying and pass through a 18-mesh sieve to obtain granulated powder. The granulated powder was placed in a mold for dry pressing molding, the molding pressure was 15MPa, and the pressure holding time was 60s to obtain a green body to be fired. After the green body is dried, it is put into a multifunctional sintering furnace and kept at 1730°C for 1 hour. Nitrogen at 0.6 atmospheres is always used as an inert gas protection atmo...

Embodiment 2

[0021] Put 81g of silicon nitride (D50=0.55μm, α=94.2%), 3g of alumina, 5g of yttrium oxide powder, 5g of lanthanum oxide, 6g of silicon dioxide, 1g of polyvinyl alcohol, and 100mL of deionized water into a ball mill jar Ball milling, rotating speed 580r / min, ball milling time 6h. Dry the above ball-milled uniform slurry and pass it through an 18-mesh sieve to obtain a granulated powder. The granulated powder was placed in a mold for dry pressing molding with a molding pressure of 20 MPa and a holding time of 60 s to obtain a calcined green body. After the green body is dried, it is placed in a multifunctional sintering furnace for sintering, the sintering temperature is 1650°C, and the holding time is 1h. During the whole sintering process, nitrogen at 2 atmospheres was always used as an inert gas protection atmosphere.

[0022] The silicon nitride ceramic obtained in this embodiment has a density of 97% of the theoretical density and a bending strength of 830 MPa.

Embodiment 3

[0024] Silicon nitride 88g (D50=0.95μm, α=92.5%), aluminum oxide 3g, magnesium oxide 5g, yttrium oxide 4g, polyethylene glycol solution 40mL (concentration 5%), ammonium polyacrylate 0.8g, tributyl phosphate Put 0.06g of fat solution and 45mL of deionized water into a ball mill jar for wet milling at a speed of 580r / min and a ball milling time of 4h. Dry the uniformly mixed solution, pass through a 40-mesh sieve for granulation. The granulated powder was put into a mold for dry pressing molding, the molding pressure was 25MPa, and the holding time was 100s to obtain a green body. The green body was kept at 1700° C. for 2 hours to obtain silicon nitride ceramics, and the pressure of the nitrogen protective atmosphere was 0.4 atmospheres.

[0025] The relative density of the silicon nitride ceramic obtained in this embodiment is 98%, the ablation rate is 0.6%, and the bending strength is 890MPa.

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Abstract

The invention relates to the technical field of ceramic materials, in particular to a method for preparing high-compactness silicon nitride ceramic by adding composite additives. Auxiliary materials are prepared from, by mass, 70-90% of silicon nitride, 4-15% of metal oxide, 3-12% of rare earth oxide, 0.5-3% of a binding agent, 0-8% of silicon dioxide, 0-3% of cesium fluoride, 0-1% of a dispersing agent and 0-0.15% of a defoaming agent. The raw materials, grinding medium balls and dispersing media are mixed and dried and then are screened, and granulation powder is obtained; the granulation powder is placed in a mold to be pressed into green bodies, the green bodies are placed in a sintering furnace after being dried, and the high-compactness silicon nitride ceramic is obtained through sintering under nitrogen protection. By mans of the preparation method, the silicon nitride ceramic can be sintered at normal pressure, operation is easy, convenient and feasible, cost is low, and the preparation method is suitable for industrial production. Besides, the silicon nitride ceramic obtained through sintering is good in compactness and high in bending strength and can be widely used as structural element materials in the fields of machinery, metallurgy, aerospace and the like.

Description

technical field [0001] The invention belongs to the technical field of ceramic materials, and in particular relates to a method for preparing high-density silicon nitride ceramics by adding compound additives. Background technique [0002] As an excellent high-temperature structural material, silicon nitride ceramics have many advantages such as high mechanical strength, high temperature resistance, good thermal shock resistance, low density, corrosion resistance, oxidation resistance, and self-lubrication. In machining, aerospace, military, life and other fields. Tools produced from silicon nitride can perform high-speed cutting, high-impact cutting, and threading. Silicon nitride bearings can operate normally under harsh conditions such as high temperature, corrosion, high speed, and no lubrication. Cars equipped with silicon nitride glow plugs only need to warm up for ten seconds when starting in cold winter. The moment of inertia of the turbine rotor made of silicon n...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/584C04B35/622
CPCC04B35/584C04B35/622C04B2235/3206C04B2235/3217C04B2235/3224C04B2235/3225C04B2235/3227C04B2235/3229C04B2235/3232C04B2235/3244C04B2235/3418
Inventor 张红冉刘久明
Owner HEBEI COREFRA SILICON NITRIDE MATERIAL
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