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Leaching in active protective coatings observed in-situ by nano-CT using synchrotron radiation
No full textActive protective coatings have been used and studied for decades. It is well known that the coating composition and microstructure determine the leaching behavior of the corrosion inhibiting species from the coating matrix. However, the leaching process on the microscale is a complex phenomenon important details of which remain obscured till today. Non-destructive spatial observation of the leaching process by nano-computed tomography using synchrotron radiation can contribute to a deeper understanding. Here, we report on the first truly in-situ 3D observation of microscale leaching. 3D images were generated while individual inhibitor particles dissolve from the coating matrix due to exposure to flowing water. The development and growth of pores and pore clusters was observed with a sequence of 3D images as a function of time demonstrating that leaching progresses by successive dissolution of inter-connected soluble particles
Searching for Axion Dark Matter Near Relaxing Magnetars
No full textAxion dark matter passing through the magnetospheres of magnetars can undergo hyper-efficient resonant mixing with low-energy photons, leading to the production of narrow spectral lines that could be detectable on Earth. Since this is a resonant process triggered by the spatial variation in the photon dispersion relation, the luminosity and spectral properties of the emission are highly sensitive to the charge and current densities permeating the magnetosphere. To date, a majority of the studies investigating this phenomenon have assumed a perfectly dipolar magnetic field structure with a near-field plasma distribution fixed to the minimal charge-separated force-free configuration. While this {may} be a reasonable treatment for the closed field lines of conventional radio pulsars, the strong magnetic fields around magnetars are believed to host processes that drive strong deviations from this minimal configuration. In this work, we study how realistic magnetar magnetospheres impact the electromagnetic emission produced from axion dark matter. Specifically, we construct charge and current distributions that are consistent with magnetar observations, and use these to recompute the prospective sensitivity of radio and sub-mm telescopes to axion dark matter. We demonstrate that the two leading models yield vastly different predictions for the frequency and amplitude of the spectral line, indicating systematic uncertainties in the plasma structure are significant. Finally, we discuss various observational signatures that can be used to differentiate the local plasma loading mechanism of an individual magnetar, which will be necessary if there is hope of using such objects to search for axions
Intrinsic Structure of Lipoplexes Embedded in Polyelectrolyte Multilayers
No full textThe functionalization of surfaces with therapeutically applicable nucleic acid carriers provides promising strategies in biomedical research to develop therapies that focus on local nucleic acid delivery. One such approach is the embedding of lipoplexes (LPXs) in polysaccharide-based polyelectrolyte multilayers (PEMs). PEMs based on hyaluronic acid and chitosan lead to efficient embedding of customized LPX connected with good biological activity. However, although quantitative evaluation demonstrates LPX embedding, information about detailed characteristics of embedded LPXs has been missing. In this study, we used synchrotron-based grazing-incidence small-angle X-ray scattering to investigate the effects of the change in the chemical environment caused by the embedding into PEMs on the LPX’s internal mesoscopic structure. While the lamellar character of the LPXs was preserved, the repeat distance was affected by embedding into polysaccharide-based coatings
Multimodal characterization of flow-induced thrombus initiation and growth in extracorporeal membrane oxygenation
No full textIn cases of severe cardiopulmonary failure, extracorporeal membrane oxygenation (ECMO) may be temporarily used as a life-saving support for cardiac and/or lung function. Operating under non-physiological flow conditions, characterized by elevated shear rates and stagnant flow zones, there is an increased risk of inducing thrombosis, bleeding and hemolysis. Pinpointing the underlying mechanism triggering the onset of thrombus formation may aid development of device design, as well as management of anti-coagulation, benefiting patient outcome. Here we present a combined methodology enabling a multiscale understanding of thrombus development. Two thrombi collected from different ECMO circuits were analyzed by computational fluid dynamics (CFD), ultra small angle X-ray scattering (USAXS) and scanning electron microscopy (SEM). USAXS quantified the density and bulk alignment of fibrin, building the thrombus scaffold structure. SEM provided information on cellular morphology and surface fibrin structure, and CFD identified regions in the ECMO circuit with high thrombotic potential. Together, this combined approach was able to link local flow conditions and the structural growth of thrombi in ECMO circuits
Synchrotron X-ray diffraction for carbide evolution during tempering of laser powder bed fusion tool steel
No full textIn pursuit of enhancing the mechanical properties of laser powder bed fusion (L-PBF)-produced hot work tool steels, this study investigates the evolution of carbides from the as-built state to the quenched and tempered conditions of a modified H13 steel. The heat treatment involved austenitization and quenching, followed by tempering at two temperatures: 600 °C and 625 °C. To monitor microstructural changes over time, tempering durations of 10, 20, 40, 80, 120, 130, 140, 160, 200, and 240 min were applied at both temperatures. Subsequently, the samples underwent synchrotron radiation analysis, scanning electron microscopy (SEM), and hardness testing. The results revealed notable variations in carbide fractions, martensite tetragonality, and micro-strain depending on tempering time and temperature. Synchrotron X-ray diffraction (XRD) is shown to effectively track carbide evolution in L-PBF tool steels which provides guidance for optimizing post-process heat treatment
Local Structure Distortion in Mn, Zn Doped CuVO: Supercapacitor Performance and Emergent Spin-Phonon Coupling
No full textSupercapacitors are rapidly gaining attention as next-generation energy storage devices due to their superior power and energy densities. This study pioneers the investigation of Mn/Zn co-doping in -CuVO (CVO) to enhance its performance as a supercapacitor electrode material. Structural and local Structural properties of Mn/Zn co-doped CVO have been investigated through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and X-ray Absorption Spectroscopy (XAS), revealing significant distortions that enhance supercapacitor performance. The optimized sample demonstrates a remarkable specific capacitance of 1950.95 Fg, energy density of 97.54 Whkg, and enhanced capacitive retention,attributedtotheuniqueCucoordinationenvironmentandimproved charge transfer kinetics. Temperature-dependent Raman spectroscopy unveils spin-phonon coupling (SPC), particularly in VO stretching modes, supported by magnetic measurements that shows a reduction in the Néel temperature and the emergence of zero field-cooled (ZFC) exchange bias (EB). This work is the first to report the impact of local structure distortion on both supercapacitor performance and SPC in CVO, offering a novel strategy for developing high-performance energy storage materials with spintronics potential. In addition, the assembled symmetric optimized supercapacitor shows a high energy density of 93.32 Whkg and excellent cycling stability. A prototype device incorporating the optimized CVO successfully powers eight commercial LED bulbs, demonstrating its practical application potential
Three-dimensional mapping of residual stresses and crack propagation in refill friction stir spot welded aluminium samples via synchrotron X-ray diffraction and X-ray micro-computed tomography
No full textRefill Friction Stir Spot Welding (refill FSSW) shows strong potential to replace riveting in the aerospace industry. However, the complex deformation and thermal effects associated with this process lead to residual stresses that may influence the fatigue life of the joint. This study reveals for the first time the non-uniform residual stresses across the thickness of a refill FSSW aluminium joint using synchrotron X-ray radiation in combination with a conical slit cell. Clear differences can be observed in the stresses between the region subjected to plasticisation and that affected solely by heat input. A fatigue testing campaign on the aluminium joints demonstrated their high reproducibility and robustness. X-ray micro-computed tomography enabled the three-dimensional visualisation of fatigue crack nucleation and propagation morphology, the latter correlated with the tensile residual stresses in the weld area. The results can contribute to the development of more accurate fatigue life prediction models and improve the overall reliability of refill FSSW aluminium joints in engineering applications
Chirped-pulse Fourier transform microwave spectrum of the HCl–DCl heterodime
No full textAbstract: Hydrohalic acid dimers provide a fundamental opportunity to study hydrogen bond rearrangement dynamics at a high level of detail. The (HCl)2 and (DCl)2 homodimers do not have a pure rotational spectrum due to rapid geared tunneling motions that interchange the role of the hydrogen bond donor and acceptor. In this work, we report the pure rotational spectrum of HCl–DCl, which has a preference for deuterium in the hydrogen bond donor position. However, the quadrupole coupling constants indicate a significant amount of geared tunneling, consistent with significant zero-point wavefunction amplitude in the less stable DCl–HCl configuration. A comparison of experimental results with previously published wavefunction calculations based on model and ab initio potentials is consistent with a picture in which about 14% of the probability density distribution is located in the less stable well
Non-destructuve 3D microstructure mapping for large samples with complex microstructure
No full textScanning 3D x-ray diffraction is a non-destructive synchrotron technique for mapping the 3D microstructure of polycrystalline materials where a focused hard x-ray beam is scanned across the sample to obtain spatially-resolved microstructure information. We demonstrate a new approach to such an experiment which extends the capabilities of existing techniques to be able to handle more complex and highly deformed microstructures. We demonstrate this by mapping the formation of sub micro meter sized deformation twins in-situ and in the bulk at deformation levels up to 20% in an as-built additively manufactured steel sample