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Experimental observation of stress formation during selective laser melting using in situ X-ray diffraction
摘要： Despite the ongoing success of metal additive manufacturing and especially the selective laser melting (SLM) technology, process-related defects, distortions and residual stresses impede its usability for fracture-critical applications. In this paper, results of in situ X-ray diffraction experiments are presented that offer insights into the strain and stress formation during the manufacturing of multi-layer thin walls made from Inconel 625. Using different measuring modes and laser scanning parameters, several experimental observations are discussed to validate and extend theoretical models and simulations from the literature. As a sample is built-up layer by layer, the stress state changes continuously up until the last exposure. The localized energy input leads to a complex stress field around the heat source that involves alternating tensile and compressive stresses. The correlation of temperature and yield strength results in a stress maximum at a certain distance to the top layer. The present study demonstrates the potential of high-energy synchrotron radiation diffraction for in situ SLM research.
关键词： Inconel 625,Selective laser melting,Stress formation,In situ,High energy synchrotron radiation diffraction
更新于2025-09-16 10:30:52
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X-ray Beam Induced Current Measurements for Multi-Modal X-ray Microscopy of Solar Cells
摘要： X-ray beam induced current (XBIC) measurements allow mapping of the nanoscale performance of electronic devices such as solar cells. Ideally, XBIC is employed simultaneously with other techniques within a multi-modal X-ray microscopy approach. An example is given herein combining XBIC with X-ray fluorescence to enable point-by-point correlations of the electrical performance with chemical composition. For the highest signal-to-noise ratio in XBIC measurements, lock-in amplification plays a crucial role. By this approach, the X-ray beam is modulated by an optical chopper upstream of the sample. The modulated X-ray beam induced electrical signal is amplified and demodulated to the chopper frequency using a lock-in amplifier. By optimizing low-pass filter settings, modulation frequency, and amplification amplitudes, noise can efficiently be suppressed for the extraction of a clear XBIC signal. A similar setup can be used to measure the X-ray beam induced voltage (XBIV). Beyond standard XBIC/XBIV measurements, XBIC can be measured with bias light or bias voltage applied such that outdoor working conditions of solar cells can be reproduced during in-situ and operando measurements. Ultimately, the multi-modal and multi-dimensional evaluation of electronic devices at the nanoscale enables new insights into the complex dependencies between composition, structure, and performance, which is an important step towards solving the materials' paradigm.
关键词： XBIV,solar cell,lock-in amplification,synchrotron radiation,photovoltaics,multi-modal,XBIC,CIGS,X-ray beam induced voltage,X-ray microscopy,X-ray beam induced current
更新于2025-09-16 10:30:52
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A multi-beam X-ray imaging detector using a branched optical fiber bundle
摘要： We developed a multi-beam X-ray imaging detector, consisting of four scintillator screens connected by a branched optical fiber bundle with a CMOS camera. By using the detector and a multi-beam imaging optics with silicon single crystalline blades designed for a white synchrotron radiation source, we successfully demonstrated multi-beam X-ray imaging with an exposure time of 1 ms. The long and flexible optical fiber bundle used for the detector enables us to realize high-speed multi-beam X-ray imaging with high flexibility at a relatively low cost.
关键词： synchrotron radiation,scintillator screens,optical fiber bundle,multi-beam X-ray imaging,CMOS camera
更新于2025-09-16 10:30:52
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[IEEE 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Sydney, Australia (2018.11.10-2018.11.17)] 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC) - Laser Doped Layer in CdTe Diode Detectors Revealed by Synchrotron XPS
摘要： The X-ray photoelectron spectroscopy (XPS) with 650 eV synchrotron radiation was applied to study the modified surface in the CdTe diode-type X/γ-ray detectors fabricated by the laser-induced doping techniques. Semi-insulating (111)-oriented p-like CdTe single crystals, pre-coated with an In dopant film, were irradiated by nanosecond pulses of a YAG:Nd laser (λ = 1064 nm). The activation of the In/CdTe interface and doping were carried out by laser irradiation of the metalized samples from the In side or through the semiconductor which was transparent for such wavelength. In the first case, laser-induced doping was attributed to the generation of laser-stimulated stress and shock waves which incorporated In atoms into the CdTe surface region. In the second case, it was possible to directly affect the In/CdTe interface because laser radiation was strongly absorbed by a thin layer of the deposited In dopant film and the CdTe was dissolved in molten In. The distribution of In and Cd atoms with the depth and atomic bonding in the In/CdTe interface were analyzed based on the high resolution In 3d and Cd 3d peaks in the XPS spectra of the formed In/CdTe diode structures subjected to Ar-ion sputtering. The stoichiometry and transformation of electronic structure in the modified CdTe layer were analyzed. Rectification properties of the created In/CdTe/Au diodes were due to the formation of an In enriched submicron layer as result of laser-induced solid-phase or liquid-phase doping that depended on irradiation of the In/CdTe structure from the metalized or semiconductor side, respectively. The created In/CdTe/Au diodes have been promising for X/γ-ray detector application.
关键词： laser doping,XPS spectra,synchrotron radiation,CdTe crystals,p-n junction
更新于2025-09-11 14:15:04
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Effect of post heat treatment on the phase composition and strength of laser welded joints of an Al–Mg–Li alloy
摘要： In the present work, the effects of laser beam welding and post-weld heat treatment on the phase composition and mechanical properties of the 1424 alloy (Al–Mg–Li) joints were investigated. Holding the joints at a certain temperature was followed by quenching and artificial aging. The structural studies were carried out using electron microscopy, conventional X-ray diffractometry, and synchrotron radiation diffractometry. The heat treatment conditions were optimized to favor the formation of strengthening phases in the welds, the presence of which imparted mechanical strength to the joints. For the first time, 1424 Al alloy joints with a weld strength of σuts = 500 MPa have been obtained; this value of strength was achieved by applying post-weld annealing followed by quenching and artificial aging.
关键词： X-ray diffraction,Aluminum-lithium alloy,Laser welding,Electron microscopy,Synchrotron radiation,Mechanical properties
更新于2025-09-11 14:15:04
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Coupled Binding and Helix Formation Monitored by Synchrotron-Radiation Circular Dichroism
摘要： Intrinsically disordered proteins organize interaction networks in the cell in many regulation and signaling processes. These proteins often gain structure upon binding to their target proteins in multistep reactions involving the formation of both secondary and tertiary structure. To understand the interactions of disordered proteins, we need to understand the mechanisms of these coupled folding and binding reactions. We studied helix formation in the binding of the molten globule-like nuclear coactivator binding domain and the disordered interaction domain from activator of thyroid hormone and retinoid receptors. We demonstrate that helix formation in a rapid binding reaction can be followed by stopped-flow synchrotron-radiation circular dichroism (CD) spectroscopy and describe the design of such a beamline. Fluorescence-monitored binding experiments of activator of thyroid hormone and retinoid receptors and nuclear coactivator binding domain display several kinetic phases, including one concentration-independent phase, which is consistent with an intermediate stabilized at high ionic strength. Time-resolved CD experiments show that almost all helicity is formed upon initial association of the proteins or separated from the encounter complex by only a small energy barrier. Through simulation of mechanistic models, we show that the intermediate observed at high ionic strength likely involves a structural rearrangement with minor overall changes in helicity. Our experiments provide a benchmark for simulations of coupled binding reactions and demonstrate the feasibility of using synchrotron-radiation CD for mechanistic studies of protein-protein interactions.
关键词： coupled folding and binding,synchrotron-radiation circular dichroism,protein-protein interactions,Intrinsically disordered proteins,helix formation
更新于2025-09-11 14:15:04
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Local valence electronic states of silicon (sub)oxides on HfO2/Si-(sub)oxide/Si(110) and HfSi2/Si-(sub)oxide/Si(110) Islands
摘要： The effect on the local valence electronic states of Sin+ suboxide components (n = 2, 3, and 4) of hafnium deposited on a low-index Si(110) substrate is investigated by Si-L23VV Auger electron Sin+-2p photoelectron coincidence spectroscopy (Si-L23VV-Sin+-2p APECS), and the chemical states and stabilities are discussed. Hafnium-covered Si(110) is immediately oxidized to HfO2 and SiO2 because hafnium serves as an effective catalyst for Si oxidation. Therefore, a HfO2/Sin+-(sub)oxide/Si(110) [HfO2/Sin+/Si(110)] structure is easily formed (n = 1, 2, 3, and 4). Oxygen diffusion from HfO2 layers toward the Si(110) substrate is promoted by annealing at 923 K. Oxygen atom desorption from the HfO2/Sin+/Si(110) surface occurs after annealing at 1073 K, and HfSi2 islands (i-HfSi2) are formed with a partly exposed Si(110)-16 × 2 double domain (DD) surface. i-HfSi2 shows low reactivity toward O2 molecules, whereas the exposed Si(110)-16 × 2 DD surface is immediately oxidized. Here, a i-HfSi2/Sin+-(sub)oxide/Si(110) structure is formed. Furthermore, we measure the Si-L23VV-Sin+-2p APECS spectra of Sin+ in the HfO2/Sin+/Si(110) and the i-HfSi2/Sin+/Si(110) structures (n = 2, 3, and 4) to evaluate the local valence electronic states of the Sin+ (sub)oxide components. The binding energy at the valence band maximum (BEVBM) of Sin+ in the i-HfSi2/Sin+/Si(110) structure is lower than 1.5 ± 0.7 eV as compared to that in the HfO2/Sin+/Si(110) structure (n = 2, 3, and 4). The local valence electric states of the nearest neighbors and the second neighbors through oxygen of Sin+ are determined to affect those of the Sin+ atom (n = 2, 3, and 4). The Sin+ atoms in the i-HfSi2/Sin+/Si(110) structure can directly bond to hafnium atoms as the nearest neighbors and most commonly have Sim+ atoms in lower ionic valence states as second neighbors (m < 4), whereas the Sin+ atoms in the HfO2/Sin+/Si(110) structure cannot form this bond. In addition, the existence of Hf silicide and Si in lower ionic valence states can reduce the band gap of the HfO2/Si(110) structure.
关键词： High-dielectric-constant material,X-ray photoelectron spectroscopy,Local valence electronic states at surface and interface,Synchrotron radiation,Auger photoelectron coincidence spectroscopy,Metal-insulator-semiconductor structure
更新于2025-09-11 14:15:04
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Synchrotron-based Spectroscopy In On-Surface Polymerization of Covalent Networks
摘要： Synchrotron radiation is a powerful tool to probe physical properties of materials on the nanoscopic scale. It can provide a chemical fingerprint of a nanomaterial with unrivalled resolution, it can measure the geometric structure down to thousands of a nanometer with not only elemental sensitivity but also chemical sensitivity, and it can study charge transfer dynamics in the sub-nanosecond regime. Within this article the application of synchrotron radiation to studying on-surface catalysis, to the view of forming two-dimensional covalent networks, will be explored.
关键词： covalent networks,on-surface polymerization,Normal Incidence X-ray Standing Waves,Synchrotron radiation,X-ray Photoemission Spectroscopy,Near Edge X-ray Absorption Fine Structure
更新于2025-09-10 09:29:36
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Towards MYTHEN 3: Characterization of prototype chips
摘要： MYTHEN 3 is a new single-photon-counting readout chip being developed by the SLS detector group in 110 nm UMC technology. It will equip a 60k-channel, 50 μm pitch microstrip detector optimized for powder diffraction experiments. Every readout channel features an amplifier and a shaper with variable gain and shaping time. The shaper output is fed to three independent discriminators, each one having a dedicated threshold, trim bit set and enable signal. The outputs of the three discriminators are processed by the counting logic section which, according to the mode of operation selected, generates the hits for the three following 24-bit counters. Several operation modes are foreseen: dual polarity, energy-windowing, count rate improvement, charge sharing suppression and pump with multiple probe time slots. The first 64-channel prototype has been tested in the lab, with fluorescence X-rays and with a synchrotron beam to characterize its noise and count rate capability. Based on the results obtained from the first chip a second 64-channel prototype has been developed and sent to production. The architecture of the chip and characterization results of the first chip will be presented.
关键词： Frontend,Powder diffraction,DAQ,Synchrotron radiation,Trigger,Silicon microstrip detector
更新于2025-09-10 09:29:36
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[Advances in Experimental Medicine and Biology] Glycobiophysics Volume 1104 || Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism Spectroscopy for Characterizing the Structure of Saccharides
摘要： Circular-dichroism (CD) spectroscopy is a powerful tool for analyzing the structures of chiral molecules and biomolecules. The development of CD instruments using synchrotron radiation has greatly expanded the utility of this method by extending the spectra to the vacuum-ultraviolet (VUV) region below 190 nm and thereby yielding information that is unobtainable by conventional CD instruments. This technique is especially advantageous for monitoring the structure of saccharides that contain hydroxy and acetal groups with high-energy transitions in the VUV region. Combining VUVCD spectra with theoretical calculations provides new insight into the contributions of anomeric hydroxy groups and rotational isomers of hydroxymethyl groups to the dynamics, intramolecular hydrogen bonds, and hydration of saccharides in aqueous solution.
关键词： Glycoprotein,Hydration,Circular dichroism,Synchrotron radiation,Time-dependent density functional theory,Molecular dynamics simulation,Saccharide,Intramolecular hydrogen bond,Solution structure,Structural dynamics,Vacuum ultraviolet,Glycosaminoglycan
更新于2025-09-10 09:29:36