Gas Pressure Sintering of Silicon Nitride to Optimize Fracture Toughness

Sintered reaction bonded silicon nitride with aligned whisker seeds was prepared by tape casting silicon slurry with 5 wt% b-Si3N4 whisker seeds followed by nitridation and sintering. Three different sintering additives were used for the samples; 7 wt% Y2O3, 6 wt% Y2O3 + 1 wt% Al2O3 and 5 wt% Y2O3 + 2 wt% Al2O3. The sample with 5 wt% Y2O3 + 2 wt% Al2O3 showed the fastest a to b phase transformation after nitridation and the highest fracture toughness and flexural strength after gas pressure sintering among the samples. It also had finer microstructure than the other samples after sintering at 2248 K and at 2273 K. The finer microstructure was related to the faster phase transformation after nitridation, which resulted in the higher flexural strength.

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Development of α-β SiAlON Ceramics from Different Si3N4 Starting Powders

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.403.107 ◽

2008 ◽

Vol 403 ◽

pp. 107-108 ◽

Cited By ~ 1

Author(s):

Nurcan Calis Acikbas ◽

Ferhat Kara ◽

Hasan Mandal

Keyword(s):

Fracture Toughness ◽

Process Parameters ◽

Gas Pressure ◽

Economic Viability ◽

Si3n4 Powder ◽

Gas Pressure Sintering

- SiAlON ceramics were produced from different starting Si3N4 powders including β-Si3N4 and α-Si3N4 powders and mixtures of these powders. Gas pressure sintering was used for sintering. After sintering, resultant fracture toughness values were correlated with microstructure and starting powders. By optimizing chemistry and process parameters; - SiAlON ceramics with reasonable fracture toughness can be produced from rather coarse β-Si3N4 powder. This could improve the economic viability of SiAlON ceramics since -Si3N4 powders are less costly.

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Thermal Conductivity of Si₃N₄ Ceramics Fabricated From Carbothermal-reduction-derived Powder

10.21203/rs.3.rs-910628/v1 ◽

2021 ◽

Author(s):

Yuelong Wang ◽

Xingyu Li ◽

Haoyang Wu ◽

Baorui Jia ◽

Deyin Zhang ◽

...

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Fracture Toughness ◽

Grain Size ◽

Flexural Strength ◽

Grain Boundaries ◽

Carbothermal Reduction ◽

Secondary Phase ◽

Gas Pressure ◽

Gas Pressure Sintering

Abstract Si3N4-based ceramic (Si3N4-5wt%Y2O3-3wt%MgO) was obtained from carbothermal-reduction-derived powder combined with gas pressure sintering. The phase, microstructure, thermal conductivity and mechanical properties of Si3N4 ceramics were comprehensively analyzed. Dense Si3N4 ceramic with uniform grain size was obtained after sintering at 1900°C for 7 h under a N2 pressure of 1.2 MPa. The secondary phase consisted of Y4Si2O7N2 and Y2Si3O3N4 was found to gather around triangular grain boundaries. The thermal conductivity, flexural strength, hardness and fracture toughness of the Si3N4 ceramics were 95.7 W·m-1·k-1, 715 MPa, 17.2 GPa and 7.2 MPa·m1/2, respectively. The results were compared with product derived from commercial powder, the improvement of thermal conductivity (~8.3%) and fracture toughness (~4.3%) demonstrating the superiority of Si3N4 ceramics prepared from carbothermal-reduction-derived powder.

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