Silica combined porous SiN ceramic with high strength and low dielectric constant and its prepn process

Abstract

The present invention is porous Si3N4 ceramic combined with high purity and low dielectric constant silica and its preparation process. The present invention features adopting graphite as pore creating agent, silica externally added or oxidization produced on the surface of Si3N4 as combining phase to combine Si3N4 through high temperature sintering, and pore forming through powdered material stacking or burning off the pore creating agent to obtain silica combined porous Si3N4 ceramic. The preparation process includes mixing Si3N4, SiO2 and graphite in the weight ratio of 0-100 to 0-30 to 0-25 as well as phenolic resin and alcohol, ball milling, stoving, grinding, sieving, drying pressing to form, and sintering in the air to obtain the silica combined porous Si3N4 ceramic. The porous ceramic has bending strength up to 137 MPa, total porosity of 10-60 % and normal temperature dielectric constant 2-7 at 1GHz, and may be used in antenna hood, catalyst carrier, etc.

Description

technical field [0001] The invention relates to a low-cost preparation of high-strength, low-permittivity silicon nitride porous ceramics and a preparation method, belonging to the field of porous ceramics. Background technique [0002] Porous ceramics are widely used in filters, catalyst carriers, thermal insulation materials and refractory materials due to their light weight, high permeability, stable performance at high temperature, good acid and alkali corrosion resistance and good catalytic activity. Silicon nitride porous ceramics show broad application prospects due to their low thermal expansion coefficient, high thermal conductivity and excellent mechanical properties. Wang Hongjie and others (Chinese patent, application number 200410073163.9) used silicon nitride and phenolic resin as raw materials, alumina and yttrium oxide as sintering aids, and sintered at 1700-1800°C in a nitrogen atmosphere to prepare nitrogen by carbothermal reduction reaction. Silicon carbi...

AI Technical Summary

Problems solved by technology

In order to obtain higher mechanical properties, most of the above silicon nitride porous ceramics are prepared using nitrogen or an inert atmosphere, sintered at a high temperature above 1600 ° C, and the particles are directly bonded with silicon nitride, thus greatly increasing the preparation cost.

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