Preparation of (Ti,Zr,Hf,Nb,Ta)C high-entropy carbide ceramics through carbosilicothermic reduction of oxides
Introduction
The group IV and V transition metal binary carbides with the rock salt type structure (B1), including TiC, ZrC, HfC, NbC, and TaC, are well known as the most refractory compounds having melting temperatures above 3000 °C. At the same time they exhibit extremely high hardness and elastic moduli, providing a rationale for their use in high and ultra-high temperature structural applications [[1], [2], [3]]. Along with the growing interest in the binary carbides listed above, the group IV and V transition metal high-entropy carbides (HECs) have recently attracted great attention. These multi-principal element carbides are found to crystallize in the B1 structure in which the atoms of metals in near-equimolar ratios share a cation position, giving increase in thermodynamic stability due to mixing entropy factor [4]. They have much lower thermal conductivity and diffusivity and better mechanical properties in comparison to those of the binary carbides [[5], [6], [7], [8], [9], [10], [11]]. This makes HEC ceramics a very promising candidate for various industrial applications, e.g., for the components of high temperature nuclear reactors, jet engines and hypersonic vehicles operating under the most extreme environments, etc. Several approaches to fabricating HEC ceramics and ceramic powders are currently known, including pressure-assisted reactive sintering of binary carbides mixtures [[5], [6], [7], [8],[11], [12], [13], [14]], carbothermal reduction of metal oxides mixtures with either graphite or carbon black [[14], [15], [16], [17]], mechanosynthesis through reaction between metallic powders and graphite [[18], [19], [20]]. In addition, magnetron co-sputtering technique can be used to obtain HEC coatings [21,22].
The major difficulty with the preparation of fully dense HEC ceramics is that it requires very high temperature (1800–2200 °C) and pressure (20–60 MPa), because of poor sinterability of HECs. It is suggested that densification temperature can be lowered by using silicon-rich transition metal silicides as sintering aids, by analogy with the case of binary carbide ceramics where MoSi2 and TaSi2 sintering aids have been successfully utilized to improve densification and mechanical properties of the obtained ceramics [[23], [24], [25], [26], [27]]. It is also reasonable to consider the possibility of synthesizing both HEC and transition metal silicide at once in a single synthesis procedure as a convenient way to introduce sintering aid into the material. For this purpose, we suggest an approach based on vacuum carbosilicothermic reduction (VCSTR) of oxides, which has been recently developed for the synthesis of MAX phase T3SiC2 and Ti4SiC3 from TiO2 [[28], [29], [30], [31], [32], [33]]. The essence of the VCSTR approach is that it utilizes a combination of silicon- and carbon-containing reductants, which necessarily includes SiC reductant. This brings together carbothermic and silicothermic reduction processes, allowing both carbide and silicide compounds to be formed simultaneously. In the present study, we aimed to apply the proposed approach for the preparation of HEC ceramics from a mixture of the group IV and V transition metal oxides by two-step technique, which involves the VCSTR synthesis of a composite powder containing both HEC and silicon-rich transition metal silicide sintering aid followed by the hot pressing of the as-synthesized product.
Section snippets
Experimental
Reagent grade TiO2, ZrO2, HfO2, Nb2O5, and Ta2O5 oxide powders were mixed with commercial grade SiC and carbon black powder reductants in the following compositions: 0.2TiO2 + 0.2ZrO2 + 0.2HfO2 + 0.1Nb2O5 + 0.1Ta2O5 + 2C + 0.725SiC. The obtained mixture was wetted with distilled water, and then granulated through a 2.5 mm sieve and dried at 80 °C. Afterwards, the dry granular reaction mixture was heat treated at 1600 °C for 1 h under dynamic high-vacuum conditions in a laboratory-made
Results and discussion
It was observed that the VCSTR synthesis was accompanied by a short-term increase in pressure in the furnace chamber when the temperature was higher than 1200 °C (see Fig. 1). This effect lasted not more than 25 min and was a result of SiO and CO gases evolution during the oxides reduction. A direct consequence of this process was a significant weight loss of about 34.1 %.
The XRD pattern of the sample after the step of VCSTR synthesis is shown in Fig. 2a. It demonstrates that the synthesized
Conclusion
In summary, we have proposed here a two-step technique for preparation of fully dense HEC ceramic from a mixture of the group IV and V transition metal oxides. In the first step, a composite powder containing approximately 75 vol.% HEC, 20 vol.% (Nb1-xMex)Si2 (where Me = Ti, Zr, Hf, Ta), and 5 vol.% SiC was prepared through the VCSTR synthesis at 1600 °C for 1 h. In the second step, the as-synthesized product was hot pressed under 40 MPa at 1750 °C for 1 h into a nearly single-phase HEC ceramic
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors are grateful to the Russian Foundation for Basic Research for grant #19-08-00131. The study was performed using the equipment of the Center for Shared Use of Scientific Equipment “Khimiya” of the Institute of Chemistry, FRC Komi Science Center of the Ural Branch of the Russian Academy of Sciences. The EBSD analysis was performed using the equipment of the TESCAN Demonstration and Methodological Center (Saint-Petersburg, Russia).
References (51)
- et al.
High-entropy carbide: a novel class of multicomponent ceramics
Ceram. Int.
(2018) - et al.
First-principles study, fabrication and characterization of (Zr0.25Nb0.25Ti0.25V0.25)C high-entropy ceramics
Acta Mater.
(2019) - et al.
High entropy carbide ceramics from different starting materials
J. Eur. Ceram. Soc.
(2019) - et al.
Synthesis of single-phase high-entropy carbide powders
Scripta Mater.
(2019) - et al.
Low temperature synthesis of an equiatomic (TiZrHfVNb)C5 high entropy carbide by a mechanically-induced carbon diffusion route
Ceram. Int.
(2019) - et al.
High-entropy (HfTaTiNbZr)C and (HfTaTiNbMo)C carbides fabricated through reactive high-energy ball milling and spark plasma sintering
Ceram. Int.
(2020) - et al.
Nanostructured multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C hard coatings
Surf. Coat. Tech.
(2012) - et al.
Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance
Mater. Des.
(2018) - et al.
Processing, phase evaluation and mechanical properties of MoSi2 doped 4TaC–HfC based UHTCs consolidated by spark plasma sintering
Int. J. Refract. Metals Hard Mater.
(2016) - et al.
Spark plasma sintering of TaC–HfC UHTC via disilicides sintering aids
J. Eur. Ceram. Soc.
(2013)
Transmission electron microscopy on Hf-and Ta-carbides sintered with TaSi2
J. Eur. Ceram. Soc.
Fabrication of Ti3SiC2 and Ti4SiC3 MAX phase ceramics through reduction of TiO2 with SiC
Ceram. Int.
Instrumented and Vickers indentation for the characterization of stiffness, hardness and toughness of zirconia toughened Al2O3 and SiC armor
J. Mater. Sci. Technol.
Crystal structure of NaCl-type transition metal monocarbides MC (M= V, Ti, Nb, Ta, Hf, Zr), a neutron powder diffraction study
Mater. Sci. Eng. B
Refinement of crystallographic parameters in transition metal disilicides with the C11b, C40 and C54 structures
Intermetallics
High-entropy silicide ceramics developed from (TiZrNbMoW)Si2 formulation doped with aluminum
J. Eur. Ceram. Soc.
A high-entropy silicide: (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2
J. Materiomics
Dual-phase high-entropy ultra-high temperature ceramics
J. Eur. Ceram. Soc.
Incorporation effects of Si in TiCx thin films
Surf. Coat. Technol.
Structural, hardness and toughness evolution in Si-incorporated TaC films
Ceram. Int.
Microstructures and mechanical properties of high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C ceramics with the addition of SiC secondary phase
J. Eur. Ceram. Soc.
Densification and joining of a (HfTaZrNbTi) C high-entropy ceramic by hot pressing
J. Eur. Ceram. Soc.
Pressureless sintering and properties of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high-entropy ceramics: the effect of pyrolytic carbon
J. Eur. Ceram. Soc.
Ultra-High Temperature Materials II: Refractory Carbides I (Ta, Hf, Nb and Zr Carbides)
Ultra-High Temperature Materials II: Refractory Carbides II (Ti and V Carbides)
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