Influence of zirconia addition on reaction bonded silicon nitride produced from various silicon particle sizes

Abstract

Reaction bonded silicon nitride ceramics have been produced from Si powders of different particle size and both with and without zirconia as a nitride catalyzing element. The effect of the ZrO2 on the nitridation rate of the specimens was studied as a function of temperature, and the mechanism of enhanced nitridation was discussed. At all temperatures, the degree of nitridation of specimens sintered with ZrO2 was higher than those without additions for all particle sizes. In the case of nitridation of specimens produced without ZrO2, the degree of nitridation was dependent on particle size, with larger sizes resulting in less nitridation. For specimens with ZrO2 the finest powder also showed highest transformation, but there was no difference in the degree of nitridation of medium and coarse powders. It was found that during heating of the specimens the ZrO2 was transformed to ZrN at low temperature and enhanced nitridation is considered to be due to this phase re-converting to ZrO2 at higher temperature and thereby supplying nitrogen to the interior of the specimens. At lower temperatures, the strength of the specimens with ZrO2 were higher than those without, attributed to the enhanced nitridation. However, comparing strengths of fully nitrided specimens, those with ZrO2 were lower than those without, thought to be due to the presence of ZrO2 particles disrupting the connectivity of adjacent silicon nitride grains.

Synthesis of porous Si3N4/SiC ceramics with rapid nitridation of silicon

“…For the effects of silicon particle sizes, the smaller size resulted in higher extent of nitridation. This is because the silicon powder with larger particle size has smaller reactive area per unit mass, thus slowing down the reaction kinetics during the silicon nitridation [22,23], as shown in Fig. 1(a).…”

Fabrication of Dense β-SiAlON Ceramics with ZrO2 Additions Via a Rapid Reaction-Bonding and Postsintering Route

“…On the other hand, in the case of the SiAlON powder with ZrO 2 additions, the starting temperature of the main weight gain step occurring around 13001C was clearly lower than those for the other powders. 19,20 (2) Reaction Bonding and Postsintering Figure 3 shows the photographic images of the reaction-bonded SiAlON samples with and without ZrO 2 as a function of differ- Fig. 17 Figure 2 shows the normalized degree of nitridation, calculated from the TG analysis results, for mixed powders corresponding to the SiAlON composition of Z 5 1 with and without ZrO 2 that were heated and then held at 14001C under flowing nitrogen conditions.…”

“…This nitridation-enhancing mechanisms has been reported by the authors in detail. 19,20 (2) Reaction Bonding and Postsintering Figure 3 shows the photographic images of the reaction-bonded SiAlON samples with and without ZrO 2 as a function of differ- Fig. 1.…”

Nitridation behaviour of ZrO2 added silicon powder with different ZrO2 particle sizes

“…16), 17) However, in that work the effect of ZrO2 particle size was not clarified. In this study, the nitridation behaviour of silicon powder with various particle size of ZrO2 was studied using thermo-gravimetric analysis under nitrogen gas flow conditions.…”