C0.3N0.7Ti-SiC Toughed Silicon Nitride Hybrids with Non-Oxide Additives Ti3SiC2.

Heng Luo,Haibin Zhang,Chen Li,Lianwen Deng,Yang Li,Peng Xiao

doi:10.3390/ma13061428

Heng Luo, Haibin Zhang + Show 4 more

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https://doi.org/10.3390/ma13061428

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Abstract

In situ grown C0.3N0.7Ti and SiC, which derived from non-oxide additives Ti3SiC2, are proposed to densify silicon nitride (Si3N4) ceramics with enhanced mechanical performance via hot-press sintering. Remarkable increase of density from 79.20% to 95.48% could be achieved for Si3N4 ceramics with 5 vol.% Ti3SiC2 when sintered at 1600 °C. As expected, higher sintering temperature 1700 °C could further promote densification of Si3N4 ceramics filled with Ti3SiC2. The capillarity of decomposed Si from Ti3SiC2, and in situ reaction between nonstoichiometric TiCx and Si3N4 were believed to be responsible for densification of Si3N4 ceramics. An obvious enhancement of flexural strength and fracture toughness for Si3N4 with x vol.% Ti3SiC2 (x = 1~20) ceramics was observed. The maximum flexural strength of 795 MPa for Si3N4 composites with 5 vol.% Ti3SiC2 and maximum fracture toughness of 6.97 MPa·m1/2 for Si3N4 composites with 20 vol.% Ti3SiC2 are achieved via hot-press sintering at 1700 °C. Pull out of elongated Si3N4 grains, crack bridging, crack branching and crack deflection were demonstrated to dominate enhance fracture toughness of Si3N4 composites.

Highlights

Several alternatives of structural ceramics have been proposed, silicon nitride (Si3 N4 )-based ceramics remain competitive due to their superior properties, involving high strength and hardness at elevated temperatures, high resistance to oxidation and chemical attack, low coefficient of tribological friction and thermal expansion, and low dielectric permittivity, etc. [1,2,3,4,5,6,7,8,9,10]
For Si3 N4 ceramics which HP sintered at 1600 ◦ C without aids, the density is only 2.58
Partial densification may be attributed to the residual SiO liquid phase during firing at g·cm high-temperature which always present on Si3 N4 powder particles

Summary

Introduction

Several alternatives of structural ceramics have been proposed, silicon nitride (Si3 N4 )-based ceramics remain competitive due to their superior properties, involving high strength and hardness at elevated temperatures, high resistance to oxidation and chemical attack, low coefficient of tribological friction and thermal expansion, and low dielectric permittivity, etc. [1,2,3,4,5,6,7,8,9,10]. Effective approaches to ensure rapid consolidation and high mechanical performance of Si3 N4 -based ceramics are actively being explored, including gas pressure sintering (GPS) [11], hot-pressing sintering (HPS) [20,21,22,23,24,25,26], hot isostatic pressing sintering (HIP) [27], spark plasma sintering (SPS) [26,28,29], and microwave sintering [1,30], etc. Previous considerable efforts have demonstrated that fully dense Si3 N4 ceramics with superior strength could be achieved through liquid phase sintering by Materials 2020, 13, 1428; doi:10.3390/ma13061428 www.mdpi.com/journal/materials

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