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Method for preparing porous ceramic by coating beta-Si3N4 granule with oxide

A technology of porous ceramics and composite oxides, applied in the field of silicon nitride series ceramics, can solve the problems of complex sintering process, deterioration of material properties, etc., and achieve the effects of low dielectric constant, excellent dielectric properties, and low dielectric loss

Inactive Publication Date: 2009-01-28
BEIHANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In order to completely discharge the pore-forming agent from the green body, a relatively complicated sintering process is required, and there is a risk that the pore-forming agent will react with the matrix to generate impurities and deteriorate the material properties.

Method used

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  • Method for preparing porous ceramic by coating beta-Si3N4 granule with oxide
  • Method for preparing porous ceramic by coating beta-Si3N4 granule with oxide
  • Method for preparing porous ceramic by coating beta-Si3N4 granule with oxide

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0048] Preparation of composite oxide CaO-B 2 o 3 -SiO 2 coated β-Si 3 N 4 The granular porous ceramic has the following preparation steps:

[0049] Step 1: Prepare the Base

[0050] long columnar β-Si 3 N 4 The powder is ground to 200 mesh;

[0051] The second step: making CaO-B 2 o 3 -SiO 2 sol

[0052] Deionized water, ethanol, ethyl orthosilicate, boric acid, calcium nitrate (Ca(NO 3 ) 2 4H 2 O) and citric acid are added in the heating reflux vessel;

[0053] When the temperature is raised to 70°C under stirring, after 60 minutes in a constant temperature water bath, the container is cooled to 25°C with heating and reflux to prepare CaO-B 2 o 3 -SiO 2 Sol; stirring speed 300r / min;

[0054] Dosage: Add 200ml of absolute ethanol, 160ml of tetraethyl orthosilicate, 16g of boric acid HBO to 100ml of deionized water 3 , 130g of Ca(NO 3 ) 2 4H 2 O and 27 g of citric acid;

[0055] The third step: making slurry

[0056] The 200-mesh long columnar β-Si prep...

Embodiment 2

[0074] Preparation of composite oxide CaO-B 2 o 3 -SiO 2 coated β-Si 3 N 4 The granular porous ceramic has the following preparation steps:

[0075] Step 1: Prepare the Base

[0076] long columnar β-Si 3 N 4 The powder is ground to 80 mesh;

[0077] The second step: making CaO-B 2 o 3 -SiO 2 sol

[0078] Deionized water, ethanol, ethyl orthosilicate, boric acid, calcium nitrate (Ca(NO 3 ) 2 4H 2 O) and citric acid are added in the heating reflux vessel;

[0079] When the temperature is raised to 60°C under stirring, after 70 minutes in a constant temperature water bath, the container is cooled to 28°C with heating and reflux, and CaO-B is prepared. 2 o 3 -SiO 2 Sol; stirring speed 400r / min;

[0080] Dosage: Add 120ml of absolute ethanol, 100ml of tetraethyl orthosilicate, 13g of HBO to 100ml of deionized water 3 , 60g of Ca(NO 3 ) 2 4H 2 O and 13 g of citric acid;

[0081] The third step: making slurry

[0082] The 80-mesh long columnar β-Si prepared in...

Embodiment 3

[0092] Preparation of composite oxide CaO-B 2 o 3 -SiO 2 coated β-Si 3 N 4 The granular porous ceramic has the following preparation steps:

[0093] Step 1: Prepare the Base

[0094] long columnar β-Si 3 N 4 The powder is ground to 300 mesh;

[0095] The second step: making CaO-B 2 o 3 -SiO 2 sol

[0096] Deionized water, ethanol, ethyl orthosilicate, boric acid, calcium nitrate (Ca(NO 3 ) 2 4H 2 O) and citric acid are added in the heating reflux vessel;

[0097] When the temperature is raised to 90°C under stirring, after 45 minutes in a constant temperature water bath, the container is cooled to 22°C with heating and reflux to prepare CaO-B 2 o 3 -SiO 2 Sol; stirring speed 300r / min;

[0098] Dosage: Add 250ml of absolute ethanol, 200ml of tetraethyl orthosilicate, 35g of HBO to 100ml of deionized water 3 , 180g of Ca(NO 3 ) 2 4H 2 O and 40 g of citric acid;

[0099] The third step: making slurry

[0100] The 300-mesh long columnar β-Si prepared in the...

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Abstract

The invention discloses a method for preparing porous ceramic by coating beta-Si3N4 particles with a composite oxide CaO-SiO2-B2O3, which is a porous body preparation technology comprising the following steps: the beta-Si3N4 particles are put into a CaO-SiO2-B2O3 sol made from tetraethoxysilane, boric acid, calcium nitrate, citric acid, absolute ethyl alcohol and deionized water, and the vacuum filtration method is adopted to form the porous body by self porous structure of the columnar beta-Si3N4 crystalline particles. The surface of the sintered beta-Si3N4 particles is coated with a modification layer of CaO-SiO2-B2O3 oxide interface, and the modification layer effectively connects the beta-Si3N4 particles and prevents the beta-Si3N4 particles from oxidation at high temperature. The porous ceramic prepared by the method can be used as a radome and a catalyst carrier material.

Description

technical field [0001] The present invention relates to a kind of silicon nitride ceramics, more particularly, refers to an oxide-coated β-Si 3 N 4 Process for preparing porous ceramics from particles. Background technique [0002] Silicon nitride ceramics have the characteristics of high temperature resistance, corrosion resistance, thermal shock resistance, high hardness, good toughness, small thermal expansion coefficient, etc., and have a moderate dielectric constant, which is the ceramic material with the best comprehensive performance. Porous silicon nitride can be regarded as a composite of silicon nitride and pores. It combines the advantages of silicon nitride and porous ceramics to meet the requirements of light weight, heat resistance and broadband wave transmission. It is used in missile radomes and spacecraft communication windows. It has broad application prospects. [0003] Silicon nitride ceramics are difficult to sinter at low temperatures. Scholars at h...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/628C04B35/584C04B35/622
Inventor 王树彬艾洪昌孙雨薇李世杰
Owner BEIHANG UNIV
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