Effects of Nitrogen Pressure on Microstructure and Mechanical Performance of Porous Silicon Nitride Ceramics

doi:10.3724/SP.J.1077.2014.13531

Journal of Inorganic Materials ›› 2014, Vol. 29 ›› Issue (7): 701-705.DOI: 10.3724/SP.J.1077.2014.13531

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Effects of Nitrogen Pressure on Microstructure and Mechanical Performance of Porous Silicon Nitride Ceramics

ZHANG Jun-Xi¹, XU Zhao-Yun¹, WANG Bo¹, QIN Yi¹, YANG Jian-Feng¹, ZHAO Zhong-Jian², HU Wei², SHI Zhi-Wei²

(1. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China; 2. Shanghai FRP Research Institute CO., Ltd., Shanghai 201404, China)

Received:2013-10-17 Revised:2013-11-27 Published:2014-07-20 Online:2014-06-20
About author:ZHANG Jun-Xi. E-mail: xzy0030@163.com
Supported by:
National Natural Science Foundation of China (51272205,51072157);A3 Foresight Program (51161140399)

Abstract

Abstract:

Porous silicon nitride ceramic was fabricated by using α-Si₃N₄ as raw material and Y₂O₃ as a sintering additive, with nitrogen pressure of 0.12 MPa, 0.32 MPa and 0.52 MPa. Effects of the nitrogen pressure on grain morphology and mechanical properties of the resultant porous Si₃N₄ ceramics were characterized by SEM, XRD and flexural strength. With the increasing of nitrogen pressure, sintering shrinkage decreased, with a corresponding increased porosity. Due to the increase of nitrogen pressure, the viscosity of liquid phase increased due to increased N solubility, leading to the low densification in the sintering. Fibrous β-Si₃N₄ grains were developed in the porous microstructure and the grain morphology and aspect ratio were greatly affected by the nitrogen pressures. The high viscosity of the liquid phase in nitrogen at high pressure led to restraining of the β-Si₃N₄ nucleation, and preferential growth of β-Si₃N₄. Due to the formation of elongated β-Si₃N₄, flexural strength of the porous Si₃N₄ ceramic was improved by the increase of nitrogen pressure, while decreased with the increase of porosity. The porous Si₃N₄ ceramics with porosity of 58% and flexural strength of 140 MPa were obtained at the nitrogen pressure of 0.52 MPa.

Key words: Si3N4 nitrogen pressure, aspect ratio

CLC Number:

TQ174

ZHANG Jun-Xi, XU Zhao-Yun, WANG Bo, QIN Yi, YANG Jian-Feng, ZHAO Zhong-Jian, HU Wei, SHI Zhi-Wei. Effects of Nitrogen Pressure on Microstructure and Mechanical Performance of Porous Silicon Nitride Ceramics[J]. Journal of Inorganic Materials, 2014, 29(7): 701-705.

Figures/Tables 7

Fig. 1 Heating curves of sinter porous Si3N4 ceramics

Fig. 2 Shrinkage and porosity of porous Si3N4 ceramic as a function of N2 pressure

Fig. 3 XRD patterns of porous Si3N4 ceramic sintered at 1750 ℃for 2 h with N2 pressure of 0.32 MPa

Fig. 4 SEM images of porous Si3N4 ceramic sintered at 1750 ℃ with different N2 pressures (a) 0.12 MPa; (b) 0.32 MPa; (c) 0.52 MPa

Fig. 5 Grain size distribution of porous Si3N4 ceramic sintered at 1750 ℃ with different N2 pressures

Fig. 6 Respect ratio of porous Si3N4 ceramic grain sintered at 1750 ℃ with different N2 pressures

Fig. 7 Relation between flexural strength and different N2 pressure for porous Si3N4 ceramics

References 14

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Effects of Nitrogen Pressure on Microstructure and Mechanical Performance of Porous Silicon Nitride Ceramics

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