Effects of Sintering Conditions and Additives on Translucent Silicon Nitride Ceramics

2012 ◽  
Vol 724 ◽  
pp. 282-286 ◽  
Author(s):  
Wen Wu Yang ◽  
Miki Inada ◽  
Yumi Tanaka ◽  
Naoya Enomoto ◽  
Junichi Hojo
Keyword(s):  
Silicon Nitride ◽  
Visible Region ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Sintering Additives ◽  
Nitride Ceramics ◽  
Sintering Conditions

Translucent β-Si3N4 sintered ceramics have been fabricated by using AlN-MgO sintering additives. In the present study, the authors employed AlN-MgO as a standard sintering aid, and investigated the effects of sintering conditions on the translucency of Si3N4. Furthermore, various oxides such as HfO2, Sm2O3, Y2O3, Sc2O3, La2O3, Nd2O3, CeO2, CaO, ZrO2 etc. were used as the sintering aids of Si3N4, and the sintered β-Si3N4 ceramics exhibited different transmittances in the visible region. It was found that the transmittance of sintered ceramics was mainly affected by the sintering additives.

Crystallization of Zirconium Nitride in Silicon Nitride Ceramics with Nitrogen Pressures and Sintering Additives

2005 ◽  
Vol 287 ◽  
pp. 253-258 ◽  
Author(s):  
S.M. Lee ◽  
K.H. Park ◽  
Jung Whan Yoo ◽  
Hyung Tae Kim
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Surface Region ◽  
Nitrogen Atmosphere ◽  
Zirconium Nitride ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Heat Treated ◽  
Nitride Ceramics ◽  
Sintered Silicon

We investigated grain boundary crystallization of gas-pressure-sintered silicon nitride with zirconia and magnesia as sintering aids. Cation compositions were mostly uniform throughout the specimen however, ZrO2 was crystallized in the surface region, while ZrN in the inside. When the specimen was heat-treated at 1 atm nitrogen atmosphere, ZrO2 in the surface region transformed to ZrN. The transformation, however, was suppressed when alumina was incorporated as an additional sintering aid. Based on these results, we propose a model describing the reaction among Si3N4, SiO2, ZrO2, ZrN and N2. Observed microstructures and measured mechanical properties were consistent with the model.

Characterization of Hot-Pressed Silicon Nitride Ceramics with Alkoxide-Derived Oxide Mixtures As the Sintering Aid

1992 ◽  
Vol 287 ◽  
Author(s):  
Y. Sato ◽  
C. Sakurai ◽  
M. Ueki ◽  
K. Sugita
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Weight Ratio ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Oxide Powders ◽  
Nitride Ceramics ◽  
Final Weight ◽  
Alkoxide Method

ABSTRACTA homogeneous mixture of Y2O3, CeO2 and MgO with a final weight ratio of 3:1: 2 was prepared by the alkoxide method. The powder mixture was then added into Si3N4 powder in amounts ranging from 4 to 12 wt%, andconsolidated by hot-pressing. Microstructure and mechanical properties of the sintered bodies were determined and compared to those of materials prepared by the conventional route of mixing the oxide powders as sintering aids individually in essentially same composition. The β-fraction (modification ratio) in same composition was higher in thesintered bodies made through the alkoxide method than those made through the conventional one. The room temperature flexural strength was maximized with 6wt% addition of the alkoxide derived oxide, whereas, 12wt% addition of the total oxide was required to maximize the strength by conventional processing.

Effects of Sintering Additives on the Microstructure and Mechanical Properties of Silicon Nitride Ceramics by GPS

2010 ◽  
Vol 105-106 ◽  
pp. 27-30 ◽  
Author(s):  
Wei Ru Zhang ◽  
Feng Sun ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Transformation ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Additives ◽  
Microstructure And Mechanical Properties ◽  
Nitride Ceramics

Silicon nitride ceramics were prepared by gas pressure sintering (GPS) with different sintering additives, including La2O3, Sm2O3 and Al2O3. Effect of sintering additives on the phase-transformation, microstructure and mechanical properties of porous silicon nitride ceramics was investigated. The results show that the reaction of sintering additives each other and with SiO2 had key effects on the phase-transformation, grain growing and grain boundaries. With 9MPa N2 atmosphere pressure, holding 1h at 1850°C, adding 10wt% one of the La2O3, Sm2O3, Al2O3, porous silicon nitride was prepared and the relative density was 78%, 72%, 85% respectively. The flexural strength was less than 500MPa, and the fracture toughness was less than 4.8MPam1/2. Dropping compounds sintering additives, such as La2O3+Al2O3, Sm2O3+Al2O3 effectively improves the sintering and mechanical properties. The relative density was 99.2% and 98.7% with 10wt% compounds sintering additives. The grain ratio of length to diameter was up to 1:8. The flexural strength was more than 900MPa, and the fracture toughness was more than 8.9MPam1/2.

Development of High Performance Silicon Nitride Ceramics and their Applications

1992 ◽  
Vol 287 ◽  
Author(s):  
Yo Tajima
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
High Performance ◽  
Future Prospect ◽  
Cutting Tools ◽  
Sintering Process ◽  
Sintering Additives ◽  
Nitride Ceramics ◽  
Engine Components

ABSTRACTProgress in sintering process and improvement of mechanical properties of silicon nitride ceramics are reviewed. Emphases are placed on contributions of advanced sintering techniques and better understanding of sintering additives and microstructure-properties relations. Current applications as engine components and cutting tools are described, and future prospect is considered.

Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability

1999 ◽  
Vol 5 (S2) ◽  
pp. 778-779
Author(s):  
R.W Carpenter ◽  
W Braue ◽  
M.J. Kim
Keyword(s):  
Silicon Nitride ◽  
Heterogeneous Nucleation ◽  
Radiation Stability ◽  
Silicon Oxynitride ◽  
Minor Constituent ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Nucleation Sites ◽  
Heterogeneous Formation ◽  
A Minor

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.

Analysis of Internal Friction on Silicon Nitride with Visco-Elastic Model

2006 ◽  
Vol 317-318 ◽  
pp. 429-432 ◽  
Author(s):  
Shuji Sakaguchi
Keyword(s):  
Relaxation Time ◽  
Silicon Nitride ◽  
Internal Friction ◽  
Temperature Dependence ◽  
Creep Deformation ◽  
Maxwell Model ◽  
Elastic Model ◽  
Sintering Aids ◽  
Characteristic Peak ◽  
Nitride Ceramics

Temperature dependence of internal friction on silicon nitride ceramics with yttria and alumina sintering aids was discussed using 4-elements visco-elastic model. It is known that the internal friction of this ceramic material shows a characteristic peak at around 1040 oC and an exponential increase over 1200 oC. This temperature dependence of internal friction was well approximated with using parallel Maxwell model. The parameters for this model and the relaxation time on this model were obtained. The relaxation time was very short, compared to the transient creep deformation of this ceramics. The analyzed results on internal friction could not be related with the creep deformation.

Microstructural analyses of Si3N4 ceramics containing various sintering aids and additional Si3Ni4

1990 ◽  
Vol 48 (4) ◽  
pp. 1074-1075
Author(s):  
C.M. Sung ◽  
K.J. Ostreicher ◽  
S.T. Buljan ◽  
J.G. Baldoni ◽  
J. Hefter
Keyword(s):  
Glass Phase ◽  
Chemical Nature ◽  
Glass Composition ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Intergranular Phase ◽  
Expected Effect ◽  
Heat Treated ◽  
Nitride Ceramics ◽  
Si3n4 Ceramics

Silicon nitride ceramics containing Al2O3 (1.5 wt%)+MgO (4 wt%) (=AM4) and Al2O3 (1.5 wt%) +Y2O3 (6 wt%)(=AY6) sintering aids together with an additional 30 v% Si3N4 have been hot pressed or hot pressed and heat-treated in an attempt to devitrify the glass phase. The expected effect of adding Si3N4 to both these formulations was to modify the glass composition in addition to the overall microstructure of the ceramics while reducing the relative amount of sintering aid. The present investigation was conducted to determine the microstructural and chemical nature of the intergranular phases present.Investigation of the intergranular phase (IGP) in the AM4-30 v% Si3N4 material indicated that the IGP was generally larger in size than the IGP in AM4 without additional Si3N4.

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