Nitridation enhancing effect of ZrO2 on silicon powder

Self Cite

Joining of silicon nitride parts by a silicon nitride joint without mechanical pressure was attempted. Reaction-bonded silicon nitride (RBSN) parts were joined using a silicon slurry by a slip-cast technique, followed by reaction bonding and post-sintering. The sintering process changed the original RBSN parts and the consolidated silicon slurry to dense silicon nitride. The joined silicon nitride was successfully obtained and it exhibited an average strength of 404 MPa. Therefore, this technique has the potential to produce strong joints.

“…Here, zirconia was chosen as one of the additives to enhance RB. 13), 14) The raw powders were ball-milled for mixing and grain refinement, followed by drying to produce a mixed powder.…”

Section: Methodsmentioning

confidence: 99%

Joining of silicon nitride with silicon slurry via reaction bonding and post sintering

Kondo

Hyuga

Kita

2010

Self Cite

“…25)28) For example, Yang et al 25) investigated the catalytic effect of ZrO 2 on the nitridation of Si, and found that the conversion of Si to Si 3 N 4 increased from 43 to 96% upon using 10 wt % ZrO 2 . Hyuga 26) and Hu 27) also found that ZrO 2 could promote the nitridation process of Si powder at a relatively low temperature. On the other hand, according to Yang et al, 25) the conversion of Si to Si 3 N 4 could be increased from 43 to 90% by using 10 wt % Fe 2 O 3 .…”

Section: Introductionmentioning

confidence: 95%

Preparation of Cr<sub>2</sub>O<sub>3</sub> nanoparticles via surfactants-modified precipitation method and their catalytic effect on nitridation of silicon powders

Zhao

Zhang

Liu

et al. 2017

Cr 2 O 3 nanoparticles (NPs) were successfully prepared by a facile surfactant-modified precipitation method, and their phase composition and microstructure were characterized by X-ray diffraction, field emission-scanning electron microscopy and transmission electron microscopy. The effects of various processing parameters including surfactants type and amount, pH value and firing temperature on the synthesis of Cr 2 O 3 NPs were investigated. Highly dispersed Cr 2 O 3 NPs with an average crystalline size of 17 nm were obtained under the following optimal conditions: [Cr(NO 3 ) 3 ·9H 2 O] = 0.0316 mol/L, PEG/Cr 2 O 3 = 5 wt %, pH = 5.2, calcination temperature = 500°C and holding time = 2 h. Cr 2 O 3 NPs showed a significant accelerating effect on the nitridation of Si powder, the conversion rate of Si to Si 3 N 4 after 2 h at 1300°C reached 100 wt % upon using 3 wt % Cr 2 O 3 NPs as catalysts, but only 40 wt % in the case without using any catalysts.

“…14) However, the nitridation mechanism, the amount of ZrO2 and the mechanism behind the catalytic effect of ZrO2 on silicon nitridation have not been reported in detail. The authors focused on the catalytic effect of ZrO2 on the nitridation of silicon powder because ZrO2 is used as a kind of sintering additive 15) for the densification of silicon nitride ceramics during the post sintering process following nitridation.…”

Section: )-7)mentioning

confidence: 99%

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

Hyuga

Yoshida

Kondo

et al. 2008

Self Cite

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.