| 1. |
- Li, Hui, et al.
(författare)
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Enabling the transition to ductile MAX phases and the exfoliation to MXenes via tuning the A element
- 2023
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Ingår i: Journal of The American Ceramic Society. - : Wiley-Blackwell. - 0002-7820 .- 1551-2916. ; 106:6, s. 3765-3776
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional MXenes, exfoliated from their parental precursors-MAX phases, exhibit several outstanding properties and have achieved several accomplishments in a vast range of fields. Developing novel and high-performance MXenes has become a vital task in materials science, so estimating the possibilities for exfoliation is a topic positioned at the research frontier. Here, the likelihood of exfoliating 36 M(2)AC MAX phases was explored by using density functional theory. For MAX phases, the composition-dependent mechanical performances were investigated, highlighting evident trends, and, more essentially, improving MAX phases toughness, which can be achieved via modulating the A site. Two novel criteria were then introduced to assess the probability of exfoliating MXenes from MAX phases, having less complexity and lower computational cost than the prior studies. The excellent agreement provided by the new criteria with the reported results demonstrates that they are feasible, reliable as well as easily accessible. Furthermore, some key features that were previously suggested to be related to exfoliation are instead determined to be weakly correlated with it. We thus performed a detailed numerical analysis to locate representative and correlated features that are fundamental for the exfoliation. Our findings provide deep insight into the synthesis process and accelerate the discovery of new MXenes.
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| 2. |
- Zhang, Jing, et al.
(författare)
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Unraveling the role of the BCC-B2 transition and V occupancies in the contradictory magnetism-ductility relationship of FeCoV alloys
- 2024
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 997
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Tidskriftsartikel (refereegranskat)abstract
- The contradictory relationship between magnetism and ductility restricts further applications of FeCoV alloys in high-performance electrical machines. The role of the BCC-B2 transition, accompanied by vanadium (V) site occupancies, in magnetic moments and ductility has been explored using first-principles calculations. The variations in magnetism and ductility of FeCoV alloys are attributed to the coupling of the BCC-B2 transition and V occupancies. When V replaces Fe atoms in the equiatomic B2-FeCo alloy, the superior magnetism observed in B2-Fe50-cCo50Vc alloys is a consequence of the enhanced local magnetic moment of Fe and the ferrimagnetic-ferromagnetic transition in the magnetic state. Moreover, due to the preferential V occupancy in the B2 phase, the B2-Fe46Co50V4 alloy exhibits comparable ductility to the BCC-Fe50Co46V4 alloy. The results indicate that the increased brittleness in the B2 phase arises from the raised Peierls stress and the enhanced covalent component in interatomic bonding, which is caused by the strong hybridization between Fe and Co atoms. Pearson correlation analysis illustrates that valence electron concentration (VEC) and V content are significant factors in the contradictory relationship between magnetization and ductility. The theoretical results demonstrate that tuning the V content and atomic occupancies is helpful to achieve a trade-off between magnetization and ductility in B2-FeCoV alloys.
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| 3. |
- Lee, Chunsik, et al.
(författare)
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VEGF-B prevents excessive angiogenesis by inhibiting FGF2/FGFR1 pathway
- 2023
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Ingår i: SIGNAL TRANSDUCTION AND TARGETED THERAPY. - : SPRINGERNATURE. - 2095-9907 .- 2059-3635. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Although VEGF-B was discovered as a VEGF-A homolog a long time ago, the angiogenic effect of VEGF-B remains poorly understood with limited and diverse findings from different groups. Notwithstanding, drugs that inhibit VEGF-B together with other VEGF family members are being used to treat patients with various neovascular diseases. It is therefore critical to have a better understanding of the angiogenic effect of VEGF-B and the underlying mechanisms. Using comprehensive in vitro and in vivo methods and models, we reveal here for the first time an unexpected and surprising function of VEGF-B as an endogenous inhibitor of angiogenesis by inhibiting the FGF2/FGFR1 pathway when the latter is abundantly expressed. Mechanistically, we unveil that VEGF-B binds to FGFR1, induces FGFR1/VEGFR1 complex formation, and suppresses FGF2-induced Erk activation, and inhibits FGF2-driven angiogenesis and tumor growth. Our work uncovers a previously unrecognized novel function of VEGF-B in tethering the FGF2/FGFR1 pathway. Given the anti-angiogenic nature of VEGF-B under conditions of high FGF2/FGFR1 levels, caution is warranted when modulating VEGF-B activity to treat neovascular diseases.
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| 4. |
- Li, Shaohan, et al.
(författare)
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Pushing the limit of thermal conductivity of MAX borides and MABs
- 2022
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Ingår i: Journal of Materials Science & Technology. - : Elsevier. - 1005-0302. ; 97, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of MAX borides as well as MAB phases attracted great attention because of the renewable developments of ternary ceramics and offering great opportunities in potential applications. However, the number of borides remains limited, and further fundamental descriptions and detailed investigations on various properties are still lacking. In this report, we employ an integrated computational scheme that combines density functional theory with the evolutional algorithm to search for the favorable structures of P- and S-glued ternary borides terminated by Nb metal. We discover that the structures of 212-type, as e.g. Nb2PB2 and Nb2SB2, belong to the P‾6m2 space group, while those of 211-type, as e.g. Nb2PB and Nb2SB, prefer to crystallize in the P63/mmc space group, and the corresponding carbides Nb2PC and Nb2SC are also considered for the sake of completeness and comparative analsys. The predicted Nb2PB2, Nb2PB, Nb2SB, Nb2PC and Nb2SC are energetically stable, as revealed by the negative formation energies and by the proposed reaction paths with respect to the most competing phases, as well as dynamically stable, as suggested by the non-imaginary phonon spectra. The thermal conductivities of the six materials show unusual behaviors, particularly for the acoustic and optical contributions, and are accompanied by a strong anisotropy. Most importantly, Nb2PB2 is found to be an excellent thermal conductor with a total thermal conductivity of ~65 W/(m K), while Nb2SC is found to be an ultra-low thermal conductor, with a total thermal conductivity of ~5 W/(m K). These values are clearly outside the currently reported range of thermal conductivities, which makes Nb2PB2 and Nb2SC extremely interesting for fundamental research as well as prospective applications with the aid of artificial tunings on the almost independent MB block and the A layer. The discovery of these novel materials is expected to contribute substantially to the rapid development of ternary ceramics and to accelerate attempts in the applicability of MAX phases for heat conduction.
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| 5. |
- Li, Yuhan, et al.
(författare)
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Understanding the electrochemical properties of A(2)MSiO(4) (A = Li and Na; M = Fe, Mn, Co and Ni) and the Na doping effect on Li2MSiO4 from first-principles calculations
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:44, s. 17455-17463
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Tidskriftsartikel (refereegranskat)abstract
- To explore the feasibility of regarding silicate materials as sustainable cathode materials for rechargeable Na ion batteries, the voltage plateaus, cycling stabilities, electrical conductivities and ionic conductivities of Li2MSiO4 and Na2MSiO4 (M = Fe, Mn, Co and Ni) are investigated by first principles calculations. The calculated electrochemical performance of silicate materials gives reasonable explanations for the poor capacity retention of Li2MnSiO4 as well as the reason why Li2FeSiO4 and Li2CoSiO4 exchange only one Li ion per formula unit. In comparison with Na2MSiO4, Li2MSiO4 presents higher voltage and better cycling stability. However, Na2MSiO4 displays higher electrical and ionic conductivities. Moreover, Na2NiSiO4 also presents significant potential for application as a good cathode material for Na ion batteries, as it can deliver high voltage and reversibly exchange 1.5 Li ions per formula unit. Furthermore, to make full use of the advantages of Li2MSiO4 and Na2MSiO4, a Na doped Li1.5Na0.5MSiO4 system is explored as well. The results suggest that Na doping can improve the electronic and ionic conductivities of Li2MSiO4 materials and simultaneously maintain the voltage and cycling stability. Therefore, Na ion doping should be an effective methodology to improve the performance of Li2MSiO4 cathode materials.
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| 6. |
- Usman, Rabia, et al.
(författare)
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Investigation of Charge-Transfer Interaction in Mixed Stack Donor-Acceptor Cocrystals Toward Tunable Solid-State Emission Characteristics
- 2018
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Ingår i: Crystal Growth & Design. - : AMER CHEMICAL SOC. - 1528-7483 .- 1528-7505. ; 18:10, s. 6001-6008
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Tidskriftsartikel (refereegranskat)abstract
- The formation of three mixed binary charge transfer (CT) cocrystals with tunable photoluminescence behavior featuring both CT interaction and directional hydrogen bonding is presented. Our strategy consists of the CT induced cocrystallization of three polycyclic (naphthalene, anthracene, and pyrene) carrying a-cyanostilbene (CS) derivatives, namely, 3-(naphthalene-2-yl)-2-(p-tolyl) acrylonitrile (NPA), 3-(anthracene-9-yl)-2-phenylacrylonitrile (APA), and 2-(4-methoxyphenyl)-3-(pyrene-I-yl) acrylonitrile (MPA) as donors (D) with 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor (A). The as prepared cocrystals were probed in detail by various analytical techniques, namely, X-ray diffraction data, vibrational spectroscopy, diffuse reflectance absorption spectroscopy, fluorescence properties, and fluorescence quantum yields and lifetimes, affirming the formation of CT complexes. Complex IA features a mixed stack arrangement (D-A-D-A-D), while IIA and IIIA revealed (DAD-DAD) stack arrangement. The CT products showed distinct tunable emission colors and photoluminescence characteristics, which is closely associated with the CT interactions between the donor and acceptor moiety, and ionization potential or the it pi-electron rich character of the polycyclic moiety of the donor molecule. This research demonstrates the development of new hybrid CT functional materials with enhanced optical properties such as absorption, fluorescence emissions, and lifetimes compared to the pristine donors, which is important for the exploration of new solid-state luminescent materials.
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| 7. |
- Wei, Xiao-Ping, et al.
(författare)
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Investigations on electronic, Fermi surface, Curie temperature and optical properties of Zr2CoAl
- 2017
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Ingår i: Journal of Solid State Chemistry. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0022-4596 .- 1095-726X. ; 247, s. 97-104
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Tidskriftsartikel (refereegranskat)abstract
- Using full-potential local-orbital minimum-basis along with spin-polarized relativistic Korringa-Kohn-Rostoker methods, we study the electronic, Fermi surface, Curie temperature and optical properties of Zr2CoAl alloy. The alloy with Li2AgSb and Cu2MnAl structures are compared in terms of magnetic properties, and the electronic structures in two structures are also discussed. According to the calculated electronic states, it finds that the Zr2CoAl with Li2AgSb structure is half-metallic ferromagnet with an integral magnetic moment of 2.00 mu(beta), meanwhile we also notice the d-d and p-d hybridizations are responsible for the formation of minority-spin gap, furthermore, the fat-bands are applied to discuss the mixture between d and p electrons in the vicinity of the Fermi level. The Fermi surfaces related to the valence bands are constructed, and it is found that the spin-up valence bands 26, 27 and 28 across the Fermi energy dominate the nature of electrons. By mapping the system onto a Heisenberg Hamiltonian, we obtain the exchange coupling parameters, and observe that the Zr(A)-Co(C) and Zr(A)-Zr(B) interactions provide a major contribution for exchange interactions. Based on the calculated exchange coupling parameters, the Curie temperature is estimated to be 287.86 K at equilibrium, and also the dependence of Curie temperature on lattice constant related to the tunable Curie temperature in Zr2CoAl alloy is studied. Finally, we report the optical properties of Zr2CoAl alloy, and present the photon energy dependence of the absorption, the optical conductivity and the loss function.
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| 8. |
- Zhang, Jing, et al.
(författare)
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Understanding the magnetism-ductility trade-off in FeCoMn alloys: The role of the BCC-B2 transition and Mn occupancies
- 2024
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Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- The magnetism-ductility contradictory relationship presents a significant challenge in the development of magnetic alloys. The impact of the BCC-B2 transition, along with Mn site occupancy, on magnetism and ductility have been investigated by using first-principles calculations. The calculations involved the evaluation of magnetic moments, density of states (DOS), phase stability and ductility of FeCoMn alloys. The results of binary alloys confirm the enhancement of magnetism due to the BCC-B2 transition. Furthermore, the ordering phase transition can strengthen the magnetic interaction between Fe and Mn atoms, which is associated with minimal variations in the density of states of Fe and Mn in the B2 structure. Regarding the ductility of FeCoMn alloys, two factors contribute to increased brittleness. Firstly, the increased covalent component in bonding, as a result of the strong hybridization between different elements, leads to an increased brittleness. Secondly, the increased Peierls stress provides a larger resistance to dislocation motion, which also contributes to the increased brittleness. Finally, the Pearson correlation coefficients and data analysis indicate that VEC, spin polarizations and Mn content provide major contributions to the contradictory relationship between magnetism and ductility.
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| 9. |
- Chen, Haiyang, et al.
(författare)
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Heterogeneous Nucleating Agent for High-Boiling-Point Nonhalogenated Solvent-Processed Organic Solar Cells and Modules
- 2024
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Tidskriftsartikel (refereegranskat)abstract
- High-boiling-point nonhalogenated solvents are superior solvents to produce large-area organic solar cells (OSCs) in industry because of their wide processing window and low toxicity; while, these solvents with slow evaporation kinetics will lead excessive aggregation of state-of-the-art small molecule acceptors (e.g. L8-BO), delivering serious efficiency losses. Here, a heterogeneous nucleating agent strategy is developed by grafting oligo (ethylene glycol) side-chains on L8-BO (BTO-BO). The formation energy of the obtained BTO-BO; while, changing from liquid in a solvent to a crystalline phase, is lower than that of L8-BO irrespective of the solvent type. When BTO-BO is added as the third component into the active layer (e.g. PM6:L8-BO), it easily assembles to form numerous seed crystals, which serve as nucleation sites to trigger heterogeneous nucleation and increase nucleation density of L8-BO through strong hydrogen bonding interactions even in high-boiling-point nonhalogenated solvents. Therefore, it can effectively suppress excessive aggregation during growth, achieving ideal phase-separation active layer with small domain sizes and high crystallinity. The resultant toluene-processed OSCs exhibit a record power conversion efficiency (PCE) of 19.42% (certificated 19.12%) with excellent operational stability. The strategy also has superior advantages in large-scale devices, showing a 15.03-cm2 module with a record PCE of 16.35% (certificated 15.97%). The heterogeneous nucleating agent (BTO-BO) is developed to suppress the excessive aggregation of L8-BO in high-boiling-point nonhalogenated solvents processing, achieving the active layer with high crystallinity and nano-scaled phase separation morphology. The resultant OSCs achieve record power conversion efficiencies of 19.42% (0.062-cm2) and 16.35% (15. 03-cm2) with excellent operational stabilities. image
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| 10. |
- Dai, Jingjing, et al.
(författare)
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Behavior of intrinsic defects in BaF2 under uniaxial compressions : An ab initio investigation
- 2021
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Ingår i: Materials Today Communications. - : Elsevier. - 2352-4928. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- We revisit the defects and related optical properties of one of the prototypical scintillator materials, BaF2, by means of density functional theory calculations. The interstitial F atom is found to be the most favorable defect to be formed, while it is rather difficult to create a F vacancy, Ba vacancy and Ba interstitial intrinsically, unless external forces are applied to the lattice, such as shock compression. The migration barriers for the above defects are remarkably path dependent. For a Ba vacancy, the migration barrier in the (001) (loading) direction is significantly reduced compared to those in the perpendicular (100) and (010) directions, while the migration along the (101) direction has the least value, which is surprisingly smaller than that at ambient pressure. An interstitial Ba atom prefers to move along the (100) and (010) directions in a manner similar to collective diffusion. The F vacancy has the lowest energy barrier along the (001) direction, while uniaxial strain greatly hinders the diffusion of F interstitials. We also study the role of defects on the optical absorption and find that a F vacancy, and interstitial F and Ba atoms are able to introduce pronounced changes to the spectra, whereas the Ba vacancy only shows marginal effects. The favorable migration paths for the different types of defects under strain or pressure can contribute to the design of specific ionic conductor properties under extreme conditions.
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