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It is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0-30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y2O3) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m1/2, respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m-1·K-1. The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10-3 to 6.4 × 10-3, respectively, in 22-26 GHz.


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Improvement in mechanical properties in AlN-h-BN composites with high thermal conductivity

Show Author's information Zetan LIUShiqiang ZHAOTian YANGJi ZHOU( )
State Key Laboratory of New Ceramics & Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

Abstract

It is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0-30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y2O3) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m1/2, respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m-1·K-1. The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10-3 to 6.4 × 10-3, respectively, in 22-26 GHz.

Keywords:

aluminum nitride (AlN), boron nitride (BN), mechanical properties, thermal conductivity
Received: 20 February 2021 Revised: 12 May 2021 Accepted: 03 June 2021 Published: 13 September 2021 Issue date: December 2021
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Publication history

Received: 20 February 2021
Revised: 12 May 2021
Accepted: 03 June 2021
Published: 13 September 2021
Issue date: December 2021

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© The Author(s) 2021

Acknowledgements

This work was supported by the Basic Science Center Project of NSFC (Grant No. 51788104), as well as the National Natural Science Foundation of China (Grant Nos. 51532004 and 11704216).

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