Low‐temperature reactive sintering of carbon vacant high‐entropy carbide ceramics with in‐situ formed silicon carbide

Abstract

It is thought that the sintering of high-entropy (HE) ceramics is generally more difficult when compared to that of the corresponding single-component ceramics. In this paper, we report a novel approach to densify the HE carbide ceramics at relatively low temperatures with a small amount of silicon. Reactive spark plasma sintering (SPS) was used to densify the ceramics using powders of HE carbide and silicon as starting materials. Dense ceramics can be obtained at 1600 -1700 • C. X-ray diffraction analysis reveals that only non-stoichiometric HE carbide phase with carbon vacancy and SiC phase exist in the obtained ceramics. The in-situ formed SiC phase inherits the morphology of the starting silicon powder owing to the slower diffusion of silicon atoms compared to that of the carbon atoms in HE carbide phase. The mechanical properties of the prepared ceramics were preliminarily studied.

Fabrication and characterization of medium‐entropy carbide ceramics in low temperature sintering

“…Therefore, the introduction of vacancy cannot only promote the atomic diffusion of sintering process but also promote the formation of single‐phase solid solution. This is very similar to the phenomenon described in the Lin et al 29 . Nonstoichiometric carbides have better sinterability at higher temperatures.…”

Synthesis, mechanical, and thermophysical properties of high‐entropy (Zr,Ti,Nb,Ta,Hf)C0.8 ceramic

“…The introduction of carbon vacancies in TMCs could remarkably lower the activation energy and accelerate the mass transfer, and thus can significantly reduce their sintering temperatures 29 . Similarly, the sintering behaviors of high‐entropy TMCs can be largely improved by regulating carbon stoichiometry 26–28,30 . Due to the promoted diffusion, more un‐synthesized single‐phase high‐entropy TMCs could be obtained by introducing carbon vacancies.…”

“…24 One of the typical features of TMCs is the high tolerance to variable unoccupied carbon sites. [25][26][27][28] The introduction of carbon vacancies in TMCs could remarkably lower the activation energy and accelerate the mass transfer, and thus can significantly reduce their sintering temperatures. 29 Similarly, the sintering behaviors of high-entropy TMCs can be largely improved by regulating carbon stoichiometry.…”

“…29 Similarly, the sintering behaviors of high-entropy TMCs can be largely improved by regulating carbon stoichiometry. [26][27][28]30 Due to the promoted diffusion, more un-synthesized single-phase high-entropy TMCs could be obtained by introducing carbon vacancies. It is also promising that the irradiation tolerance could be enhanced significantly in high-entropy TMCs with moderate carbon vacancies.…”

Low‐temperature reactive hot‐pressing of Ta0.2Hf0.8C–SiC ceramics at 1700°C

“…Moreover, the formation of carbon vacancy can also promote the elements diffusion in the THC lattice and improve the densification of the samples. 30 During the nucleation and growth of SiC, some SiC particles can wrap small-sized THC grains, resulting in some white-bright THC embedded in the black SiC particles, as shown in Figures 3 and 4.…”