High-entropy ceramics (HECs) have attracted much attention due to their huge composition space,unique microstructure,and desirable properties.In contrast to previous studies,which have primarily focused on HECs with o...High-entropy ceramics (HECs) have attracted much attention due to their huge composition space,unique microstructure,and desirable properties.In contrast to previous studies,which have primarily focused on HECs with one anion,herein,we report a new family of ceramics with both multi-cationic and-anionic structures,i.e.,high-entropy carbide-nitrides (Ti0.33Zr0.33Hf0.33)(C0.5N0.5),(Ti0.25Zr0.25Hf0.25-Nb0.25)(C0.5N0.5) and (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5).These as-synthesized HECs are mainly comprised of a face-centered cubic solid-solution phase accompanied by minor inevitable oxide phases.The formation mechanism of the solid-solution phase is discussed in terms of the lattice size difference and thermodynamic competition between configurational entropy and mixing enthalpy.It is found that the increment in the configurational entropy can effectively lower the sintering temperature and increase the fracture toughness.Particularly,the newly developed (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5) exhibits a decent fracture toughness of 8.4 MPa m1/2and a low sintering temperature of 1750°C,making it promising for ultra-high temperature applications.Our work not only enriches knowledge regarding the HECs categories,but also opens a new pathway for developing HECs with multi-cationic and-anionic structures.展开更多
Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AE...Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AEMs),a series of side chain type AEMs were prepared by introducing different proportions of side chains containing anisotropic poly cations with relatively stable piperidinium ring cations and side quaternary ammonium cations as cation groups,using poly(p-terphenyl isatin)(PTI),a main chain polymer without aryl ether bonds.The dense surface of the PTI-N-n series membranes is shown by SEM images;TEM images show that the ion domains are clearly distributed in the membrane,so a continuous ion transport channel is constructed.PTI-N-100 has the highest hydroxide conductivity at 80℃,reaching 96.83 mS cm^(-1) due to multiple transport sites.The PTI-N-100 membrane has a peak power density of 180 mW cm^(2) based on the highest ionic conductivity.Therefore,we believe that the introduction of multi-cations contributes to the performance of anion exchange membranes.展开更多
基金supported by the National Natural Science Foundation of China (51671021,51961160729,1179029,51871016 and 51971017)the Funds for Creative Research Groups of China (51921001)+3 种基金111 Project (B07003)the Program for Changjiang Scholars and Innovative Research Team in University of China (IRT14R05)the Project of SKLAMM-USTB (2019Z-01)the Project supported by the State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China。
文摘High-entropy ceramics (HECs) have attracted much attention due to their huge composition space,unique microstructure,and desirable properties.In contrast to previous studies,which have primarily focused on HECs with one anion,herein,we report a new family of ceramics with both multi-cationic and-anionic structures,i.e.,high-entropy carbide-nitrides (Ti0.33Zr0.33Hf0.33)(C0.5N0.5),(Ti0.25Zr0.25Hf0.25-Nb0.25)(C0.5N0.5) and (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5).These as-synthesized HECs are mainly comprised of a face-centered cubic solid-solution phase accompanied by minor inevitable oxide phases.The formation mechanism of the solid-solution phase is discussed in terms of the lattice size difference and thermodynamic competition between configurational entropy and mixing enthalpy.It is found that the increment in the configurational entropy can effectively lower the sintering temperature and increase the fracture toughness.Particularly,the newly developed (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5) exhibits a decent fracture toughness of 8.4 MPa m1/2and a low sintering temperature of 1750°C,making it promising for ultra-high temperature applications.Our work not only enriches knowledge regarding the HECs categories,but also opens a new pathway for developing HECs with multi-cationic and-anionic structures.
基金The authors gratefully acknowledge the financial support of this work by Natural Science Foundation of China(grant no 22075031)Jilin Provincial Science&Technology Department(grant no 20220201105GX)。
文摘Research on anion exchange membrane fuel cells(AEMFCs)mainly focuses on the membrane module,and improving its performance has always been the focus of researchers.To create high-performance anion exchange membranes(AEMs),a series of side chain type AEMs were prepared by introducing different proportions of side chains containing anisotropic poly cations with relatively stable piperidinium ring cations and side quaternary ammonium cations as cation groups,using poly(p-terphenyl isatin)(PTI),a main chain polymer without aryl ether bonds.The dense surface of the PTI-N-n series membranes is shown by SEM images;TEM images show that the ion domains are clearly distributed in the membrane,so a continuous ion transport channel is constructed.PTI-N-100 has the highest hydroxide conductivity at 80℃,reaching 96.83 mS cm^(-1) due to multiple transport sites.The PTI-N-100 membrane has a peak power density of 180 mW cm^(2) based on the highest ionic conductivity.Therefore,we believe that the introduction of multi-cations contributes to the performance of anion exchange membranes.
