Effect of sintering additives on properties of Si₃N₄-BN composites fabricated via die pressing and precursor infiltration and pyrolysis route

Abstract

The Si₃N₄-BN composites have been prepared via die pressing and precursor infiltration and pyrolysis route using borazine as precursor, and the effect of sintering additives on properties of the composites has been investigated. After sintering additives are adopted, the α to β phase transition of Si₃N₄ and the mechanical properties of the composites at both room temperature and high temperature are all increased with small extent. When using Y₂O₃+Al₂O₃ as additives, the phase transition of Si₃N₄ and the mechanical properties of the composites have better results. The β-Si₃N₄ content is 17.47%. The flexural strength, elastic modulus and fracture toughness of the composites are 188.74 MPa, 84.34 GPa and 2.96 MPa·m^1/2, respectively. After exposed at 1 000 °C in the air for 15 min, the flexural strength of the composites is 154.62 MPa with a residual ratio of 81.92%. The elongated β-Si₃N₄ grains appear in all composites with different sintering additives. Relatively more rod like β-Si₃N₄ grains can be observed in composites with Y₂O³⁺Al₂O₃ as additives, making it to possess better mechanical properties.

Keywords

silicon nitride / boron nitride / borazine / composites / sintering additives

References

[1] Garcés J M, Kuperman A, Millar D M, . Synthetic Inorganic Materials[J]. Adv. Mater., 2000, 12(23): 1 725-1 735.

[2] Zerr A, Riedel R, Sekine T, . Recent Advances in New Hard Highpressure Nitrides[J]. Adv. Mater., 2006, 18: 2 933-2 948.

[3] Zou C R, Zhang C R, Li B, . Microstructure and Properties of Porous Silicon Nitride Ceramics Prepared by Gel-casting and Gas Pressure Sintering[J]. Mater. Des., 2013, 44: 114-118.

[4] Paquette D G Method of Making a Radar Transparent Window Material Operable above 2 000 °C[P], 1997

[5] Barta J, Manela M, Fischer R Si₃N₄ and Si₂N₂O for High Performance Radomes[J]. Mater. Sci. Eng., 1984, 71: 265-272.

[6] Liu H Y, Hsu S M Fracture Behavior of Multiplayer Silicon Nitride/Boron Nitride Ceramics[J]. J. Am. Ceram. Soc., 1996, 79(9): 2 452-2 457.

[7] Kovar D, Thouless M D, Halloran J W Crack Deflection and Propagation in Layered Silicon Nitride/Boron Nitride Ceramics[J]. J. Am. Ceram. Soc., 1998, 81(4): 1 004-1 012.

[8] Liu K, Zhang C R, Xiao Y D, . Synthesis of Si₃N₄-BN Composites Using Borazine as the Precursor[J]. Mater. Sci. Eng. A, 2013, 575: 48-50.

[9] Klemm H Silicon Nitride for High-temperature Applications[J]. J. Am. Ceram. Soc., 2010, 93(6): 1 501-1 522.

[10] Riley F L Silicon Nitride and Related Materials[J]. J. Am. Ceram. Soc., 2000, 83(2): 245-265.

[11] Tsuge A, Nishida K High Strength Hot-pressed Si₃N₄ with Concurrent Y₂O₃ and Al₂O₃ Additions[J]. Am. Ceram. Soc. Bull., 1978, 57(4): 424-431.

[12] Li C W, Wang C A, Huang Y, . Effects of Sintering Aids on the Microstructure and Mechanical Properties of Laminated Si₃N₄/BN Ceramics[J]. Mater. Lett., 2003, 57: 3 473-3 478.

[13] Zou L H, Hong Y, Wang C A The Characterization and Measurement of Interfacial Toughness for Si₃N₄/BN Composites by the Four-point Bend Test[J]. J. Eur. Ceram. Soc., 2004, 24: 2 861-2 868.

[14] Koh Y H, Kim H W, Kim H E, . Thermal Shock Resistance of Fibrous Monolithic Si₃N₄/BN Ceramics[J]. J. Eur. Ceram. Soc., 2004, 24: 2 339-2 347.

[15] Wei D Q, Meng Q C, Jia D C Mechanical and Tribological Properties of Hot-pressed h-BN/Si₃N₄ Ceramic Composites[J]. Ceram. Int., 2006, 32: 549-554.

[16] Sun Y, Meng Q C, Jia D C, . Effect of Hexagonal BN on the Microstructure and Mechanical Properties of Si₃N₄ Ceramics[J]. J. Mater. Process. Tech., 2007, 182: 134-138.

[17] Li J S, Zhang C R, Li B, . An Investigation on the Synthesis of Borazine[J]. Inorg. Chim. Acta, 2011, 366(1): 173-176.

[18] Kawai C, Yamakawa A Effect of Porosity and Microstructure on the Strength of Si₃N₄: Designed Microstructure for High Strength, High Thermal Shock Resistence, and Facile Maching[J]. J. Am. Ceram. Soc., 1997, 80(10): 2 705-2 708.

[19] American Society for TestingMaterials. Standard Method of Testing Small Clear Specimens of Timber[S]. ASTM D 143-94, 1998

[20] Becher P F, Painter G S, Shibata N, . Influence of Additives on Anisotropic Grain Growth in Silicon Nitride Ceramics[J]. Mater. Sci. Eng. A, 2006, 422: 85-91.

[21] Li W K, Chen D Y, Zhang B L, . Effect of Rare-earth Oxide Additives on the Morphology of Combustion Synthesized Rod-like β-Si₃N₄ Crystals[J]. Mater. Lett., 2004, 58: 2 322-2 325.