Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

J Marchi,A.H.A Bressiani,J.C Bressiani

doi:10.1590/s1516-14392001000400002

J Marchi, A.H.A Bressiani + Show 1 more

Open Access

https://doi.org/10.1590/s1516-14392001000400002

Copy DOI

Abstract

Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polished/etched samples was carried out with help of scanning electron microscopy. Silicon carbide ceramics with more than 90% of the theoretical density were obtained by pressureless sintering if a suitable proportion of the additives is used.

Highlights

Silicon carbide is an important ceramic used in structural applications, such as automotive heat engines, cutting tools, heat exchange and mechanical seals
Sintering additives based on the SiO2-Al2O3-Y2O3 system have been found to be suitable to promote SiC densification through liquid phase sintering[20,21,22]
Dilatometric experiments revealed the presence of two shrinkage peaks during sintering of silicon carbide

Summary

Introduction

Silicon carbide is an important ceramic used in structural applications, such as automotive heat engines, cutting tools, heat exchange and mechanical seals These applications are possible because of the unique properties of silicon carbide based materials, including high temperature strength and low density, as compared to conventional steel, and excellent thermal shock and wear resistance[1,2]. Sintering additives based on the SiO2-Al2O3-Y2O3 system (another rare earth oxide may replace Y2O3) have been found to be suitable to promote SiC densification through liquid phase sintering[20,21,22]. These additives have shown to be effective to obtain high density silicon nitride ceramics[23,24,25]. The influence of the oxides proportion on these parameters can be established

Experimental

Powder characterisation

Density

Dilatometric analysis

Microstructural observation

Conclusions