Densification and joining of a (HfTaZrNbTi)C high-entropy ceramic by hot pressing

Sun, Kun; Yang, Zhenwen; Mu, Ruijie; Niu, Shiyu; Wang, Ying; Wang, Dongpo

doi:10.1016/j.jeurceramsoc.2020.12.043

Cited by 47 publications

(13 citation statements)

References 48 publications

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“…5,7 However, in other studies, the average grain sizes of as-sintered samples are several micrometers and lots of pores are trapped inside grains. 6,10 In our experiment (shown in this work), numerous irregular HEC grains were formed when the sample was still porous, the formation of which cannot be explained solely by grain boundary migration mechanism. Since the fabrication of materials with desirable microstructures and properties relies on a good understanding of microstructure evolution during sintering, in-depth research on the sintering of HEC ceramics is necessary.…”

Section: Introductionmentioning

confidence: 52%

“…In some studies, (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )C ceramics with nano or submicron‐sized grains were obtained, and almost no intragranular pores could be observed, suggesting a lower grain boundary mobility than pore mobility, as expected from the sluggish diffusion effect 5,7 . However, in other studies, the average grain sizes of as‐sintered samples are several micrometers and lots of pores are trapped inside grains 6,10 . In our experiment (shown in this work), numerous irregular HEC grains were formed when the sample was still porous, the formation of which cannot be explained solely by grain boundary migration mechanism.…”

Section: Introductionmentioning

confidence: 78%

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Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering

Zhao

et al. 2022

J Am Ceram Soc.

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High‐entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C ceramics (HEC) are fabricated via spark plasma sintering using different die configurations, including the conductive and insulating dies. Compared to the conductive die, the grain sizes of samples sintered in the insulating die are significantly larger, which is attributed to the higher local temperature as a result of the higher current density in the sample. Furthermore, the microstructure evolution and grain growth mechanism of HEC are investigated for the first time. We find that at moderate temperatures (∼1600°C), the grain growth of HEC can occur by a grain coalescence mechanism, forming numerous irregular grains in the porous sample. Three factors are crucial to induce grain coalescence, including the formation of partial melting layers on particle surfaces, nanograin rearrangement via rotation and sliding, and the formation of low‐angle grain boundaries. During the final sintering stage, the irregular grains will change into polyhedral shapes by grain boundary migration. These findings are of assistance to better understand and control the microstructure evolution of HEC and other ultrahigh‐temperature carbide ceramics.

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Section: Introductionmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 78%

Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering

Zhao

et al. 2022

J Am Ceram Soc.

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“…11,12 In addition, experimental work is normally devoted to the equimolar systems for a purpose of maximum entropy. 13,14 Moreover, carbides with the identical crystal structure are favored by researchers, which are mainly concentrated in Groups IVB and VB, while there was not much reported literature on systems containing elements in Group VIB, especially element Cr. Castle et al 15 fabricated bulk (HfTaZrTi)C and (HfTaZrNb)C ceramics by ball-milling corresponding binary carbides and following spark plasma sintering with a dwell time of 2 min at 2573 K, and indicated that lattice parameter of each component was the key factor for determining the formation of solid solution.…”

Section: Introductionmentioning

confidence: 99%

“…As a result of the characteristics including high melting point and low diffusion coefficient of carbides, the formation of HECs requires harsh production conditions, like spark plasma sintering, hot pressing sintering. 14,22,23 However, a temperature over 2373 K will lead to the coarse particles of HECs and excessive energy consumption. Meanwhile, in order to improve the performance of the products, fine-grained powders are needed to prepare fine-grained ceramics by sintering technology, and low temperature is beneficial for obtaining powders with smaller particle sizes.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of high entropy carbide powders by low temperature processing

Wang

Cui

et al. 2022

Int J Applied Ceramic Tech

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High-entropy carbides (HECs) possess superior properties such as favorable corrosion resistance and marvelous hardness and are widely applied in specific extreme environments. Herein, a novel method was proposed for synthesizing HECs powders with raw materials of corresponding oxides and carbon black, which was composed of steps of ball-milling in stainless jar, carbothermic reduction at 1873 K, as well as the following calcium posttreatment at 1273 K to remove residual carbon by generating CaC 2 . Finally, pure HECs powders could be fabricated after acid leaching treatment. Under the current experimental conditions, besides HfC-TaC-ZrC-NbC quaternary system, a homogeneous solid solution could be fabricated by adding Mo or/and Ti, but it could not be achieved for systems with addition of V, W, or Cr, owing to the low lattice constant or different crystal structure of corresponding carbides. In the reduction step, iron resulted from ball milling process acted as the diffusion channel to promote the mutual diffusion of different components. Meanwhile, the calcium treatment temperature had a weak effect on particle size of HEC powders. HfC-TaC-ZrC-NbC-MoC-TiC powders prepared at the calcium posttreatment temperature of 1273 K had an oxygen content of .302% and an average grain size of 252 nm.

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“…It is crucially important that usually the synthesis of refractory carbides of transition metals (including high-entropy carbides) is performed in vacuum using various sintering techniques, like spark plasma sintering (SPS). [6,8,10,14,15,17,18] Less common synthesis methods include hot isostatic pressing, [15] and other techniques, [19][20][21][22] but all mentioned techniques require vacuum for the synthesis of high-quality carbide materials and thus are expensive and resource-consuming.…”

Section: Introductionmentioning

confidence: 99%

Large‐Scale Synthesis and Applications of Hafnium–Tantalum Carbides

Kvashnin

Никитин

Shanenkov

et al. 2022

Adv Funct Materials

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Comprehensive theoretical and experimental studies are performed to discover a new way of synthesis of HfTaC coatings. Here, an evolutionary search for stable crystal structures in the ternary HfTaC system with subsequent selective large‐scale experimental synthesis of coatings using a unique plasma dynamic experimental setup is performed. Optimization of the experimental process allows us to perform selective synthesis of coatings made of hafnium–tantalum carbides with predefined stoichiometry, crystal structure, and properties. Along with more than 70 compounds, the HfTaC system belongs to ternary and quaternary carbides of group IV and V transition metals, and this study opens the door to synthesis of a large number of functional coatings composed of other carbides including high‐entropy carbides.

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Densification and joining of a (HfTaZrNbTi)C high-entropy ceramic by hot pressing

Cited by 47 publications

References 48 publications

Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering

Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering

Synthesis of high entropy carbide powders by low temperature processing

Large‐Scale Synthesis and Applications of Hafnium–Tantalum Carbides

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Densification and joining of a (HfTaZrNbTi)C high-entropy ceramic by hot pressing

Cited by 47 publications

References 48 publications

Grain coalescence in (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C during spark plasma sintering

Grain coalescence in (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C during spark plasma sintering

Synthesis of high entropy carbide powders by low temperature processing

Large‐Scale Synthesis and Applications of Hafnium–Tantalum Carbides

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Product

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Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering

Grain coalescence in (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C during spark plasma sintering