Microwave Sintering and Infiltration of Highly Porous Silicon Nitride Ceramics to Form Dense Ceramics

Titelangaben

Willert-Porada, Monika ; Grosse-Berg, Jens ; Ilker, Sen ; Park, Ho-Seon:
Microwave Sintering and Infiltration of Highly Porous Silicon Nitride Ceramics to Form Dense Ceramics.
In: Key Engineering Materials. Bd. 287 (März 2005) . - S. 171-176.
ISSN 1662-9795
DOI: https://doi.org/10.4028/www.scientific.net/KEM.287.171

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Abstract

A new processing route for porous b-Si3N4 –ceramics suitable as substrates for Si3N4 functionally graded materials, FGM`s with an environmental barrier coating, EBC, is described. Such materials could be useful for operation at temperatures up to 1650°C in combustion engines, where oxidation and corrosion under hydrothermal conditions cause severe damage of known dense Si3N4-ceramics. The new process is based on microwave sintering of a-Si3N4–Yb-silicate green parts to obtain up to 60% open porous b-Si3N4 pre-forms equilibrated at high temperature with respect to the RE-silicate content, followed by Si-melt infiltration. A sufficient wetting by molten silicon is achieved by coating the inner surface of the porous pre-form with amorphous carbon prior to infiltration. The influence of different green processing parameters and different heating methods - microwave heating and conventional heating – on the porosity of the pre-form is reported. Infiltration is performed by microwave heating of the carbon coated pre-forms, whereas for nitridation both heating processes are combined.