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High-entropy(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) with good high temperature stability,low thermal conductivity,and anisotropic thermal expansivity

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Journal of advanced Ceramics 2020年第5期9卷 595-605页

作者： Zifan ZHAO Huimin XIANG Heng CHEN Fu-Zhi DAI Xiaohui WANG Zhijian PENG Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China School of Engineering and Technology China University of GeosciencesBeijing 100083China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The critical requirements for the environmental barrier coating(EBC)materials of silicon-based ceramic matrix composites(CMCs)include good tolerance to harsh environments,thermal expansion matches with the interlayer mullite,good high-temperature phase stability,and low thermal ***-structured rare-earth aluminates RE_(4)Al_(2)O_(9) have been considered as candidates of EBCs for their superior mechanical and thermal properties,but the phase transition at high temperatures is a notable drawback of these *** suppress the phase transition and improve the phase stability,a novel cuspidine-structured rare-earth aluminate solid solution(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) was designed and successfully synthesized inspired by entropy stabilization effect of high-entropy ceramics(HECs).The as-synthesized HE(Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) exhibits a close thermal expansion coefficient(6.96×10^(-6) K^(-1) at 300-1473 K)to that of mullite,good phase stability from 300 to 1473 K,and low thermal conductivity(1.50 W·m^(-1)·K^(-1) at room temperature).In addition,strong anisotropic thermal expansion has been observed compared to Y_(4)Al_(2)O_(9) and Yb_(4)Al_(2)O_(9).The mechanism for low thermal conductivity is attributed to the lattice distortion and mass difference of the constituent atoms,and the anisotropic thermal expansion is due to the anisotropic chemical bonding enhanced by the large size rare-earth cations.

关键词： (Nd_(0.2)Sm_(0.2)Eu_(0.2)Y_(0.2)Yb_(0.2))_(4)Al_(2)O_(9) high-entropy ceramics(HECs) environmental barrier coatings phase stability thermal properties

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Fully Exposed Copper Single-Atom Sites on Mesoporous N/S-Codoped Graphene for Efficient Zinc-Air Battery

SSRN

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SSRN 2024年

作者： Yang, Lifen Du, Changliang Tian, Jiachen Yao, Xiuyun Zhang, Qianwei Ma, Xilan Zhu, Youqi Zou, Meishuai Cao, Chuanbao Research Center of Materials Science Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications Beijing Institute of Technology Beijing100081 China

Transition metal single-atom catalysts are recently emerging as the most potential candidates for the oxygen reduction reaction due to their remarkable activity and durability, yet subjected to limited availability proportion of active sites to reactant in practice due to the lack of favorable morphology. Herein, the ultrathin mesoporous N/S-codoped graphene is fabricated by a potassium thiocyanate (KSCN) assisted pyrolysis of metal-organic framework (ZIF-8) as the robust substrate for anchoring copper single-atom sites. The KSCN-assisted pyrolysis can not only create N and S coordination atoms but also regulate the fully exposed morphology. The g-Cu-SACs show excellent catalytic activity in alkaline oxygen reduction reaction with a half-wave potential of 0.920 VRHE and good cycling stability. Furthermore, the zinc-air battery assembled with g-Cu-SACs also exhibits high specific capacity and remarkable cycling lifetime. This work provides a novel strategy to construct highly exposed single-atom catalysts for energy-related applications. © 2024, The Authors. All rights reserved.

关键词： Graphene

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Microwave Assisted Synthesis of Cobalt-Doped Copper Selenite Nanorice as Bifunctional Electrocatalyst for Overall Water Splitting

SSRN

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SSRN 2024年

作者： Rashid, Umair Zhu, Youqi Cao, Chuanbao Research Center of Materials Science Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications Beijing Institute of Technology Beijing100081 China

In the research and development of noble-metal free catalysts, copper-based materials such as copper selenite have shown interest as electrocatalysts to drive the oxygen evolution reaction (OER) in basic medium, however their Hydrogen evolution reaction (HER) activity is still unexplored. Therefore, we have performed the synthesis of cobalt doped copper selenite nanoparticles which can robustly and effectively do electrocatalysis for both the OER and HER in basic medium electrolyte. The novelty lies in the fact that microwave synthesis procedure utilizing oxidizing agent as a key precursor is entirely new, this particular material was never employed in water splitting and catalyst need very low amount of binder. The results revealed that cobalt doped copper selenite have a relatively lower starting potential and a higher current density due to the synergistic effects of a large active area, quick charge, mass transport, and a three-dimensional conducting path, having OER and HER overpotentials of 365 mV and 226mV at 10 mA/cm2 current densities, respectively. We found a novel doped structure featuring porous surfaces and distinctive rice like morphology which facilitate an efficient electron transportation during the water splitting thereby illustrating an exceptional performance of this system along with rapid synthesis and lower costs. © 2024, The Authors. All rights reserved.

关键词： Copper

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The Comprehensive Understanding of Intrinsic Contribution of Nickel Foam as a Conductive Substrate in Water Splitting

SSRN

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SSRN 2024年

Using nickel foam as a substrate for electrocatalyst to report overpotential in a manuscript is a popular method in electrochemical testing or water-splitting i.e., the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). However, use of coated Nickel foam as substrate methodology is, in essence, not reasonable for studying the intrinsic chemistry difference of electrocatalysts. To assess water-splitting devices, Ni-foam is a valid substrate if nanoparticles are grown uniformly;however, when drop-casted ink methodology is used or there is inhomogeneous growth of nanoparticles, it becomes difficult to determine whether a particular electrocatalyst is intrinsically active or not. In order to gain a rational understanding of the electrochemical activity and overpotential findings of a specific catalyst, it is essential to recognize the limitations of Ni-foam on reflecting its intrinsic role in electrocatalytic activity. Ni-foam is therefore should not be preferred as a conductive substrate during electrochemical testing (ET). On the contrary, use of other neutral substrates like carbon fiber paper (CFP) and glassy carbon electrode (GCE) should be employed. © 2024, The Authors. All rights reserved.

关键词： Electrocatalysts

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Fe-Doping Accelerated Magnesium Storage Kinetics in Rutile Tio2 Cathode Materials

SSRN

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SSRN 2024年

作者： Zhang, Qianwei Liu, Xin Du, Changliang Jin, Mingwei Yang, Lifen Jiang, Rong Ma, Xilan Zhu, Youqi Cao, Chuanbao Zou, Meishuai Research Center of Materials Science Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications Beijing Institute of Technology Beijing100081 China

Rutile titanium dioxide (TiO2) is theoretically favored as the efficient cathode materials for magnesium secondary batteries, yet rarely reported due to sluggish kinetics, low capacity, and inferior reversibility. Herein, a defect engineering strategy is developed via cationic Fe-doping to enhance the electrochemical magnesium storage kinetics of the rutile TiO2 cathode materials and achieve the surface Mg2+ adsorption/diffusion mechanism. Abundant oxygen vacancies can be generated by Fe cations in rutile TiO2 via a molten salt flux method. The optimized rutile TiO2 cathode materials show large specific capacity of 204.8 mAh g−1 at current density of 100 mA g−1, higher than that of the TiO2-based counterparts reported previously. Additionally, the Mg2+ diffusion coefficient of Fe-doped rutile TiO2 cathode materials are significantly improved to enable rapid magnesium storage. Fe cations can activate the cathode surface and weaken the Coulombic interactions between Mg2+ and anions in the host material. Oxygen vacancies can provide active adsorption sites for Mg2+ and MgCl+ to avoid slow solid-state diffusion and thus accelerate magnesium storage kinetics. Ex-situ XRD and XPS indicate that Fe-doped rutile TiO2 cathode materials undergo the energy storage mechanism of Mg2+ adsorption/diffusion without phase transition or significant lattice expansion. © 2024, The Authors. All rights reserved.

关键词： Cathodes

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Initiating Cationic-Anionic Chemistry with Stepwise Surface-to-Inner Conversion in Copper Selenide Superstructures for High-Energy Rechargeable Magnesium Batteries

SSRN

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SSRN 2024年

作者： Du, Changliang He, Siru Yang, Lifen Liu, Xin Jiang, Rong Ma, Xilan Zhu, Youqi Zou, Meishuai Cao, Chuanbao Research Center of Materials Science Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications Beijing Institute of Technology Beijing100081 China

Copper selenides are viewed as the most capable cathode materials for rechargeable magnesium batteries, yet suffer from unsatisfactory energy density due to their low operating voltage plateau (~0.9 V vs. Mg/Mg2+) and insufficient reversible capacity. Herein, a stepwise conversion from surface cationic-anionic redox to inside electrochemical displacement reaction is realized in copper selenide (Cu2-xSe) superstructure cathodes. A highly reversible high-voltage platform at ~1.6 V is discovered during discharge process. Ex-situ spectroscopy and microscopy results demonstrate that the high-voltage plateau is contributed by surface Cu2+ charge-carrier transformation and anionic Se2– redox reaction while sufficient inner Cu-Mg replacement conversion at low-voltage region. Following the favorable mechanism, the Cu2-xSe superstructure cathodes can present high specific capacity of 385.4 mAh g–1 at 0.1 A g–1 and outstanding energy density of 426.3 Wh kg–1. Moreover, the Cu2-xSe superstructure cathodes also maintain a reversible capacity of 223.6 mAh g–1 over 700 cycles with 0.0147% capacity degradation per cycle at 1.0 A g–1 and long-term charge-discharge lifetime for 3000 cycles at 5.0 A g–1. This research reports a new Mg2+ storage mechanism for copper selenide cathodes and provides novel route to develop high-energy-density rechargeable magnesium batteries. © 2024, The Authors. All rights reserved.

关键词： Cathodes

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dx2−y2-wave Bose metal induced by next-nearest-neighbor hopping anisotropy

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Physical Review B 2025年第13期111卷 134512-134512页

作者： Zhangkai Cao Jianyu Li Jiahao Su Tao Ying Ho-Kin Tang School of Science Harbin Institute of Technology Shenzhen 518055 China Shenzhen Key Laboratory of Advanced Functional Carbon Materials Research and Comprehensive Application Shenzhen 518055 China School of Physics Harbin Institute of Technology Harbin 150001 China

Superconductivity arises when electrons form Cooper pairs with phase coherence. In contrast, a lack of phase coherence in Cooper pairs can lead to an uncondensed metallic ground state known as the Bose metal state. In this paper, we investigate an attractively interacting fermionic system with nearest-neighbor hopping (t) and next-nearest-neighbor hopping (t′) anisotropy between two species of spins in a two-dimensional lattice. Utilizing the constrained path quantum Monte Carlo method, we demonstrate the existence of a dx2−y2-wave Cooper pair Bose metal (CPBM) phase with t′/t>0.7. The CPBM phase exhibits a domelike structure in the phase diagram of filling n∼0.65, with the maximal region around an optimal t′/t∼0.2, suggesting that an appropriate value of t′ facilitates the formation of the Bose metal. Furthermore, we find that a Bose metal formed by fermions with a closed Fermi surface confirms that the crucial condition for this exotic phenomenon is primarily the anisotropy of the Fermi surface rather than its topology. Our finding of the dx2−y2-wave CPBM demonstrates the same pairing symmetry as the pseudogap behavior in cuprates, and its experimental realization in ultracold atom systems is also feasible.

关键词： Anisotropy

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A highly efficient atomically thin curved Pd Ir bimetallene electrocatalyst

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National science Review 2021年第9期8卷 100-110页

作者： Fan Lv Bolong Huang Jianrui Feng Weiyu Zhang Kai Wang Na Li Jinhui Zhou Peng Zhou Wenxiu Yang Yaping Du Dong Su Shaojun Guo School of Materials Science and Engineering Peking University Department of Applied Biology and Chemical Technology Hong Kong Polytechnic University Frontier Institute of Science and Technology jointly with College of Science Xi'an Jiaotong University Center for Functional Nanomaterials Brookhaven National Laboratory School of Materials Science and Engineering & National Institute for Advanced Materials Nankai University College of Engineering Peking University

The multi-metallene with an ultrahigh surface area has great potential in precise tuning of surface heterogeneous d-electronic correlation by surface strain effect for the distinctive surface electronic structure, which is a brand new class of promising 2 D electrocatalyst for sustainable energy device application. However, achieving such an atomically thin multi-metallene still presents a great ***, we present a new synthetic method for an atomic-level palladium-iridium（Pd Ir） bimetallene with an average thickness of only～1.0 nm for achieving superior catalysis in the hydrogen evolution reaction（HER） and the formic acid oxidation reaction（FAOR）. The curved Pd Ir bimetallene presents a top-ranked high electrochemical active area of 127.5 ± 10.8 m2g Pd+Ir-1in the reported noble alloy materials, and exhibits a very low overpotential, ultrahigh activity and improved stability for HER and FAOR. DFT calculation reveals that the Pd Ir bimetallene herein has a unique lattice tangential strain, which can induce surface distortion while concurrently creating a variety of concave-convex featured micro-active regions formed by variously coordinated Pd sites agglomeration. Such a strong strain effect correlates the abnormal on-site active 4 d10-t2g-orbital Coulomb correlation potential and directly elevates orbital-electronegativity exposure within these active regions, resulting in a preeminent barrier-free energetic path for significant enhancement of FAOR and HER catalytic performance.

关键词： strain metallene PdIr alloy atomically thin electrocatalyst

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Low Temperature Sintering of High Performance Al2O3/ZrO2 Nanocomposite Ceramics

SSRN

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SSRN 2023年

作者： Liu, Xudong Yuan, Yuchen Wang, Renjie Zhu, Shiyang Bai, Yuelei Fang, Canqing Chen, Ce Zheng, Yongting National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Centre for Composite Materials and Structures Harbin Institute of Technology Harbin150080 China

In this work, amorphous/solid solution Al2O3/ZrO2 powder was prepared by combustion synthesis assisted with rapid cooling in water, followed by grinding for further refinement. The solubility of Al2O3 in the ZrO2 lattice was greatly enhanced by the rapid cooling process in water. The transformation of the metastable state and the presence of oxygen vacancies in the powder can accelerate the mass transfer during sintering, allowing for the preparation of nearly fully densified ceramics through hot press sintering at temperatures as low as 1300°C. During sintering, large numbers of ultra-fine nanoparticles (~5 nm) were precipitated from the solid solution and evenly dispersed throughout the matrix. The nanoparticles exhibit a high degree of coherence with the matrix due to the similarities in crystal structure between t-ZrO2 and α-Al2O3. The nanoparticle reinforcement effect and t-m phase transformation of ZrO2 both contributed to the ceramics' excellent mechanical properties. To compare the sintering capabilities and the performance of the ceramics, commercial powders were also sintered at the same temperature. This research may offer a new instruction for the low temperature fabrication of nanoparticles-strengthened ceramics. © 2023, The Authors. All rights reserved.

关键词： Solid solutions

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Z2 order fractionalization, topological phase transition, and odd frequency pairing in an exactly solvable spin-charge ladder

arXiv

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arXiv 2024年

作者： Miao, Jian-Jian Chen, Wei-Qiang Shenzhen508045 China Department of Physics Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and Technology Shenzhen518055 China

Motivated by the order fractionalization in Kitaev-Kondo model, we propose an exactly solvable spin-charge ladder model to study the order fractionalization with discrete symmetry. The spin-charge ladder is composed of a spin chain and a superconducting wire coupled via an Ising-type interaction, and we obtain the exact solution in the flat band limit. The exact solution reveals the Z2 order fractionalization with dual symmetry breaking and intertwined order parameters. We investigate the topological phase transition of the spin-charge ladder via the spectral chiral index, and identify the correlated topological superconductor (TSC*) phase with gapped Z2 Kondo flux excitations. We demonstrate Majorana spinons generated odd frequency pairing in the superconducting wire. We also discuss the order fractionalization in the perspective of Z2 lattice gauge theory. © 2024, CC BY.

关键词： Topology

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