The influence of additive content on microstructure and mechanical properties on the Csf/SiC composites after annealed treatment

Zhang, Yun-Long; Hu, Ming; Qin, Xiangge; Xiao-gang, Song

doi:10.1016/j.apsusc.2013.04.033

Cited by 7 publications

(1 citation statement)

References 13 publications

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“…As an alternative, the concept of in situ growth of SiC nanowires within the ceramic matrix was suggested. The growth of SiC nanowires in SiC matrix was achieved by lanthanum-catalyzed re-deposition technology [ 10 ], laser processing [ 11 ], La 2 O 3 -Al 2 O 3 -catalyzed chemical vapor deposition [ 12 , 13 ], and chemically activated combustion synthesis [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of In Situ Grown SiC Nanowires on the Pressureless Sintering of Heterophase Ceramics TaSi2-TaC-SiC

et al. 2020

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To ascertain the influence of SiC nanowires on sintering kinetics of heterophase ceramics, two composite powders (TaSi2-TaC-SiC and TaSi2-TaC-SiC-SiCnanowire) are fabricated by mechanically activated combustion synthesis of Ta-Si-C and Ta-Si-C-(C2F4) reactive mixtures. Remarkable compressibility is achieved for the TaSi2-TaC-SiC-SiCnanowire composition (green density up to 84% as compared with 45.2% achieved for TaSi2-SiC-TaC) which is attributed to the lubricating effect of residual adsorbed fluorinated carbon (most likely C4F8). The outcomes of pressureless sintering of TaSi2-TaC-SiC and TaSi2-TaC-SiC-SiCnanowire compositions are vastly different; the former experiences no significant densification or grain growth and does not attain structural integrity, whereas the latter achieves relative density up to 93% and hardness up to 11 GPa. The SiC nanowires are not retained in consolidated ceramics, but instead, act as a sintering aid and promote densification and grain growth. Sintering mechanisms of TaSi2-TaC-SiC and TaSi2-TaC-SiC-SiCnanowire powders are analyzed using thermodynamic and ab initio grand potential calculations, as well as the analysis of grain size versus relative density relations. In the case of solid-state sintering, the densification and grain growth in heterophase non-oxide ceramics are governed by the same mechanisms as previously investigated single-phase oxides. The presence of SiC nanowires enhances grain-boundary related diffusion processes due to the high specific surface and aspect ratio of the nanowires. At 1500 °C, where the formation of the transient Si-based liquid phase is thermodynamically viable, only the SiC nanowire-containing composition demonstrated the intense grain coarsening and densification associated with liquid-assisted sintering. This effect can be attributed both to the presence of SiC nanowires and purification of residual oxide impurities due to C2F4-activated combustion synthesis employed for the in situ formation of SiC nanowires.

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