| 1. |
- Wang, Tiantian, et al.
(författare)
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Microstructural probing of phosphonium-based ionic liquids on a gold electrode using colloid probe AFM
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:41, s. 25411-25419
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Tidskriftsartikel (refereegranskat)abstract
- Atomic force microscopy (AFM) with a gold colloid probe modeled as the electrode surface is employed to directly capture the contact resonance frequency of two phosphonium-based ionic liquids (ILs) containing a common anion [BScB]− and differently lengthened cations ([P6,6,6,14]+ and [P4,4,4,8]+). The comparative interfacial studies are performed by creating IL films on the surface of gold, followed by measuring the wettability, thickness of the films, adhesion forces, surface morphology and AFM-probed contact resonance frequency. In addition, the cyclic voltammetry and impedance spectroscopy measurements of the neat ILs are measured on the surface of the gold electrode. The IL with longer cation alkyl chains exhibits a well-defined thin film on the electrode surface and enhanced the capacitance than the shorter chain IL. The AFM contact resonance frequency and force curves reveal that the longer IL prefers to form stiffer ion layers at the gold electrode surface, suggesting the “…anion–anion–cation–cation…” bilayer structure, in contrast, the shorter-chain IL forms the softer cation–anion alternating structure, i.e., “…anion–cation–anion–cation…”.
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| 2. |
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| 3. |
- Su, Yiqun, et al.
(författare)
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Effect of Electrode Surface Chemistry on Ion Structuring of Imidazolium Ionic Liquids
- 2023
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 39:24, s. 8463-8474
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Tidskriftsartikel (refereegranskat)abstract
- Surface chemistry plays a critical role in the ion structuring of ionic liquids (ILs) at the interfaces of electrodes and controls the overall energy storage performance of the system. Herein, we functionalized the gold (Au) colloid probe of an atomic force microscope with −COOH and −NH2 groups to explore the effect of different surface chemical properties on the ion structuring of an IL. Aided by colloid-probe atomic force microscopy (AFM), the ion structuring of an imidazolium IL, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6], abbreviated as BP hereafter), on the Au electrode surface and the ion response to the change in the surface chemistry are investigated. AFM morphologies, contact angles, and approaching force–distance curves of the BP IL on the functionalized Au surfaces exhibited that the IL forms a more obvious layering structure on the −COOH-terminated Au surface (Au–COOH), while it forms heterogeneous and aggregating droplets on the −NH2 surface (Au–NH2). The formed uniform and aggregation-free ion layers in the vicinity of the Au–COOH surface are due to the π–π+ stacking interaction between the delocalized π+ electrons from the imidazolium ring in the IL [BMIM]+ cation and the localized π electrons from the sp2 carbon on the −COOH group. The in situ observation of nano-friction and torsional resonance frequency at the IL–electrode interfaces further demonstrated the ion structuring of the IL at Au–COOH, which results in a more sensitive electrochemical response associated with a faster capacitive process.
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| 4. |
- Tian, Rong, et al.
(författare)
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A multiresolution continuum simulation of the ductile fracture process
- 2010
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Ingår i: Journal of the mechanics and physics of solids. - : Elsevier BV. - 0022-5096 .- 1873-4782. ; 58:10, s. 1681-1700
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Tidskriftsartikel (refereegranskat)abstract
- With the advancement in computational science that is stepping into the Petascale era and experimental techniques that enable rapid reconstruction of the 3D microstructure, quantitative microstructure simulations at an unprecedented fidelity level are giving rise to new possibilities for linking microstructure to property. This paper presents recent advances in 3D computational modeling of ductile fracture in high toughness steels. Ductile fracture involves several concurrent and mutually interactive mechanisms at multiple length scales of microstructure. With serial sectioning tomographic techniques, a digital data set of microstructure features associated with the fracture process has been experimentally reconstructed. In this study, primary particles are accurately and explicitly modeled while the secondary particles are modeled by a two scale multiresolution continuum model. The present numerical simulation captures detailed characteristics of the fracture process, such as zigzag crack morphology, critical void growth ratios, local stress triaxiality variation, and intervoid ligament structure. For the first time, fracture toughness is linked to multiscale microstructures in a realistic large 3D model.
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| 5. |
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| 6. |
- Wang, Xin, et al.
(författare)
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Quantifying and Decoupling Molecular Interactions of Ionic Liquids with Gold Electrodes
- 2024
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Ingår i: Langmuir. - : American Chemical Society. - 0743-7463 .- 1520-5827. ; 40:23, s. 12017-12026
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Tidskriftsartikel (refereegranskat)abstract
- This work combined gold colloid probe atomic force microscopy (AFM) with a quartz crystal microbalance (QCM) to accurately quantify the molecular interactions of fluorine-free phosphonium-based ionic liquids (ILs) with gold electrode surfaces. First, the interactions of ILs with the gold electrode per unit area (?′A?A′, N/m2) were obtained via the force–distance curves measured by gold probe AFM. Second, a QCM was employed to detect the IL amount to acquire the equilibrium number of IL molecules adsorbed onto the gold electrode per unit area (NIL, Num/m2). Finally, the quantified molecular interactions of ILs with the gold electrode (F0, nN/Num) were estimated. F0 is closely related to the IL composition, in which the IL with the same anion but a longer phosphonium cation exhibits a stronger molecular interaction. The changes in the quantified interactions of gold with different ILs are consistent with the interactions predicted by the extended Derjaguin–Landau–Verwey–Overbeek theory, and the van der Waals interaction was identified as the major contribution of the overall interaction. The quantified molecular interaction is expected to enable the direct experimental-derived interaction parameters for molecular simulations and provide the virtual design of novel ILs for energy storage applications.
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