Microstructure Effects on Bending Strength Characteristics of LPS - SiC Ceramic

J. Ocean Eng. Technol. 2006;20(5):77-81.

Yoon, Han-Ki;Jung, Hun-Chae;

Department of Mechanical Engineering, Dongeui University;Graduate School of Mechanical Engineering, Dongeui University;

LPS - SiC 세라믹스의 굽힘강도 특성에 미치는 미시조직 영향

윤한기;정헌채;

동의대학교 기계공학과;동의대학교 대학원 기계공학과;

Keywords: Liquid phase sintered SiC, Hotpress, Sintering temperature, Sintering additives, Flexural strength, Microstructure

핵심용어: 액상소결 탄화규소, 핫프레스, 소결온도, 소결조제, 굽힘강도, 미시조직

Abstract

In this study, monolithic liquid phase sintered SiC (LPS-SiC) was made by the hot pressing method with nano-SiC powder, whose particle size is 30 nm and less on the average. Alumina ($Al_{2}O_{3}$), yttria ($Y_{2}O_{3}$), and silica ($S_{i}O_{2}$) were used for sintering additives. To investigate the effects of $S_{i}O_{2}$, the $Al_{2}O_{3}/Y_{2}O_{3}$ composition was fixed and the ratio of $S_{i}O_{2}$ was changed, with seven different ratios tested. And to investigate the effects of the sintering temperature, the sintering temperature was changed, with $1760^{circ}C,;1780_{circ}C$, and $1800_{circ}C$ being used with a $S_{i}O_{2}$ ratio of 3 wt%. The materials were sintered for 1 hour at $1760^{circ}C,;1780^{circ}C$ and $1800^{circ}C$ under a pressure of 20 MPa. The effects on sintering from the sintering system used, as well as from the composition of the sintering additives, were investigated by density measurements. Mechanical properties, such as flexural strength, were investigated to ensure the optimum conditions for a matrix of SiCf/SiC composites. Sintered densityand the flexural strength of fabricated LPS-SiC increased with an increase in sintering temperature. Particularly, the relative density of a sintered body at $1800^{circ}C$ with a non-content of $S_{i}O_{2}$, a specimen of AYSO-1800, was 95%. Also, flexural strength was about 750MPa.