| 1. |
- Ding, Haoming, et al.
(författare)
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Synthesis of MAX phases Nb2CuC and Ti2(Al0.1Cu0.9)N by A-site replacement reaction in molten salts
- 2019
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Ingår i: Materials Research Letters. - : Taylor & Francis. - 2166-3831. ; 7:12, s. 510-516
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Tidskriftsartikel (refereegranskat)abstract
- New MAX phases Ti2(AlxCu1−x)N and Nb2CuC were synthesized by A-site replacement by reacting Ti2AlN and Nb2AlC, respectively, with CuCl2 or CuI molten salt. X-ray diffraction, scanning electron microscopy, and atomically resolved scanning transmission electron microscopy showed complete A-site replacement in Nb2AlC, which lead to the formation of Nb2CuC. However, the replacement of Al in Ti2AlN phase was only close to complete at Ti2(Al0.1Cu0.9)N. Density-functional theory calculations corroborated the structural stability of Nb2CuC and Ti2CuN phases. Moreover, the calculated cleavage energy in these Cu-containing MAX phases are weaker than in their Al-containing counterparts.The preparation of MAX phases Nb2CuC and Ti2(Al0.1Cu0.9)N were realized by A-site replacement in Ti2AlN and Nb2AlN, respectively.
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| 2. |
- Li, Mian, et al.
(författare)
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Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes
- 2019
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 141:11, s. 4730-4737
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Tidskriftsartikel (refereegranskat)abstract
- Nanolaminated materials are important because of their exceptional properties and wide range of applications. Here, we demonstrate a general approach to synthesizing a series of Zn-based MAX phases and Cl-terminated MXenes originating from the replacement reaction between the MAX phase and the late transition-metal halides. The approach is a top-down route that enables the late transitional element atom (Zn in the present case) to occupy the A site in the pre-existing MAX phase structure. Using this replacement reaction between the Zn element from molten ZnCl2 and the Al element in MAX phase precursors (Ti3AlC2, Ti2AlC, Ti2AlN, and V2AlC), novel MAX phases Ti3ZnC2, Ti2ZnC, Ti2ZnN, and V2ZnC were synthesized. When employing excess ZnCl2, Cl-terminated MXenes (such as Ti3C2Cl2 and Ti2CCl2) were derived by a subsequent exfoliation of Ti3ZnC2 and Ti2ZnC due to the strong Lewis acidity of molten ZnCl2. These results indicate that A-site element replacement in traditional MAX phases by late transition-metal halides opens the door to explore MAX phases that are not thermodynamically stable at high temperature and would be difficult to synthesize through the commonly employed powder metallurgy approach. In addition, this is the first time that exclusively Cl-terminated MXenes were obtained, and the etching effect of Lewis acid in molten salts provides a green and viable route to preparing MXenes through an HF-free chemical approach.
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| 3. |
- Li, Youbing, et al.
(författare)
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Electrochemical Lithium Storage Performance of Molten Salt Derived V2SnC MAX Phase
- 2021
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Ingår i: Nano-Micro Letters. - : Springer. - 2311-6706 .- 2150-5551. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- MAX phases are gaining attention as precursors of two-dimensional MXenes that are intensively pursued in applications for electrochemical energy storage. Here, we report the preparation of V2SnC MAX phase by the molten salt method. V2SnC is investigated as a lithium storage anode, showing a high gravimetric capacity of 490 mAh g(-1) and volumetric capacity of 570 mAh cm(-3) as well as superior rate performance of 95 mAh g(-1) (110 mAh cm(-3)) at 50 C, surpassing the ever-reported performance of MAX phase anodes. Supported by operando X-ray diffraction and density functional theory, a charge storage mechanism with dual redox reaction is proposed with a Sn-Li (de)alloying reaction that occurs at the edge sites of V2SnC particles where Sn atoms are exposed to the electrolyte followed by a redox reaction that occurs at V2C layers with Li. This study offers promise of using MAX phases with M-site and A-site elements that are redox active as high-rate lithium storage materials.
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| 4. |
- Li, Youbing, et al.
(författare)
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Multielemental single atom-thick A layers in nanolaminated V2(Sn, A) C (A = Fe, Co, Ni, Mn) for tailoring magnetic properties
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 117:2, s. 820-825
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Tidskriftsartikel (refereegranskat)abstract
- Tailoring of individual single-atom-thick layers in nanolaminated materials offers atomic-level control over material properties. Nonetheless, multielement alloying in individual atomic layers in nanolaminates is largely unexplored. Here, we report 15 inherently nanolaminated V-2(A(x)Sn(1-x))C (A = Fe, Co, Ni, Mn, and combinations thereof, with x similar to 1/3) MAX phases synthesized by an alloy-guided reaction. The simultaneous occupancy of the 4 magnetic elements and Sn in the individual single-atom-thick A layers constitutes high-entropy MAX phase in which multielemental alloying exclusively occurs in the 2 -dimensional (2D) A layers. V-2(A(x)Sn(1-x))C exhibit distinct ferromagnetic behavior that can be compositionally tailored from the multielement A-layer alloying. Density functional theory and phase diagram calculations are performed to understand the structure stability of these MAX phases. This 2D multielemental alloying approach provides a structural design route to discover nanolaminated materials and expand their chemical and physical properties. In fact, the magnetic behavior of these multielemental MAX phases shows strong dependency on the combination of various elements.
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| 5. |
- Li, Youbing, et al.
(författare)
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Single-Atom-Thick Active Layers Realized in Nanolaminated Ti-3(AlxCu1-x)C-2 and Its Artificial Enzyme Behavior
- 2019
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Ingår i: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 13:8, s. 9198-9205
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Tidskriftsartikel (refereegranskat)abstract
- A Ti-3(AlxCu1-x)C-2 phase with Cu atoms with a degree of ordering in the A plane is synthesized through the A site replacement reaction in CuCl2 molten salt. The weakly bonded single -atom -thick Cu layers in a Ti-3(AlxCu1-x)C-2 MAX phase provide actives sites for catalysis chemistry. As -synthesized Ti-3(AlxCu1-x)C-2 presents unusual peroxidase-like catalytic activity similar to that of natural enzymes. A fabricated Ti-3(AlxCu1-x)C-2/chitosan/glassy carbon electrode biosensor prototype also exhibits a low detection limit in the electrochemical sensing of H2O2. These results have broad implications for property tailoring in a nanolaminated MAX phase by replacing the A site with late transition elements.
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