共查询到9条相似文献,搜索用时 0 毫秒
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Irina Lokteva Michael Koof Michael Walther Gerhard Grübel Felix Lehmkühler 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(20)
Self‐assembled nanocrystal superlattices have attracted large scientific attention due to their potential technological applications. However, the nucleation and growth mechanisms of superlattice assemblies remain largely unresolved due to experimental difficulties to monitor intermediate states. Here, the self‐assembly of colloidal PbS nanocrystals is studied in real time by a combination of controlled solvent evaporation from the bulk solution and in situ small‐angle X‐ray scattering (SAXS) in transmission geometry. For the first time for the investigated system a hexagonal closed‐packed (hcp) superlattice formed in a solvent vapor saturated atmosphere is observed during slow solvent evaporation from a colloidal suspension. The highly ordered hcp superlattice is followed by a transition into the final body‐centered cubic superlattice upon complete drying. Additionally, X‐ray cross‐correlation analysis of Bragg reflections is applied to access information on precursor structures in the assembly process, which is not evident from conventional SAXS analysis. The detailed evolution of the crystal structure with time provides key results for understanding the assembly mechanism and the role of ligand–solvent interactions, which is important both for fundamental research and for fabrication of superlattices with desired properties. 相似文献
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Pter Szalva Imre Norbert Orbulov 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(9):1949-1958
AlSi9Cu3(Fe) aluminum alloy fatigue test specimens were produced by high pressure die casting (HPDC) and vacuum‐assisted die casting (VPDC) techniques. Non‐destructive material tests (NDT) have been performed on cast specimens by computed tomography (CT). Uniaxial fatigue tests with two stress ratios of R = ?1 and R = 0.1 have been performed in the high cycle fatigue (HCF) regime, and the CT results were reassigned after the fatigue test in order to identify the origin of the failure. The aim of this paper is to establish a relationship between the CT result and fatigue failure of die cast specimens. The location and the size of the casting defect determine the specimen fatigue life. It has also been found that the fatigue life is determined not only by the size of the defect but also by its location with respect to the position of the highly stressed area. The results can be used to judge the applicability of cast parts after non‐destructive testing. 相似文献
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Insights into the Effect of Structural Heterogeneity in Carbonized Electrospun Fibrous Mats for Flow Battery Electrodes by X‐Ray Tomography 下载免费PDF全文
Matt D. R. Kok Rhodri Jervis Dan Brett Paul R. Shearing Jeff T. Gostick 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(9)
Electrospun custom made flow battery electrodes are imaged in 3D using X‐ray computed tomography. A variety of computational methods and simulations are applied to the images to determine properties including the porosity, fiber size, and pore size distributions as well as the material permeability and flow distributions. The simulations are performed on materials before and after carbonization to determine the effect it has in the internal microstructure and material properties. It is found that the deposited fiber size is constantly changing throughout the electrospinning process. The results also show that the surfaces of the fibrous material are the most severely altered during carbonization and that the rest of the material remained intact. Pressure driven flow is modeled using the lattice Boltzmann method and excellent agreement with experimental results is found. The simulations coupled with the material analysis also demonstrate the highly heterogeneous nature of the flow. Most of the flow is concentrated to regions with high porosity while regions with low porosity shield other pores and starve them of flow. The importance of imaging these materials in 3D is highlighted throughout. 相似文献
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Tu‐Ngoc Lam Wei‐Jie Huang Chun‐Chieh Wang Wei‐Tsung Chuang Ya‐Wen Su E‐Wen Huang 《Advanced Engineering Materials》2018,20(7)
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Flow Batteries: Insights into the Effect of Structural Heterogeneity in Carbonized Electrospun Fibrous Mats for Flow Battery Electrodes by X‐Ray Tomography (Small 9/2018) 下载免费PDF全文
Matt D. R. Kok Rhodri Jervis Dan Brett Paul R. Shearing Jeff T. Gostick 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(9)
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