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Fatigue of Materials at Very High Numbers of Loading Cycles (Experimental Techniques, Mechanisms, Modeling and Fatigue Life Assessment) || Three-dimensional characterization of duplex stainless steel by means of synchrotron radiation X-ray diffraction imaging techniques
摘要： The combined use of X-ray diffraction contrast tomography (DCT) and X-ray phase imaging techniques like phase contrast tomography and holotomography enable non-destructive characterization of the three dimensional grain and phase microstructure in austenitic-ferritic duplex stainless steel. Phase contrast tomography highlights discontinuities of the refractive index inside a material and is therefore ideally suited for imaging fatigue cracks and phase boundaries. The acquisition of phase images at multiple propagation distances allows for the two-step procedure of phase retrieval and tomographic reconstruction of the refractive index via holotomography. Combined with appropriate regularization and segmentation techniques, this technique provides the sensitivity to discriminate the minute difference in electron density between the austenitic and ferritic constituent phases of duplex steel. X-ray diffraction contrast tomography on the other hand exploits X-ray Bragg diffraction signals of the individual crystallites and yields three-dimensional grain orientation maps for each of the constituent phases (austenite and ferrite). Merging the results of both imaging modalities, the fidelity of the inter-phase boundaries (derived from X-ray holotomography) can be used to enhance the spatial fidelity of the 3D grain orientation maps produced by DCT. We have combined this microstructure characterization scheme with time lapse observations of a propagating fatigue crack by means of repeated phase contrast tomography inspection during an interrupted fatigue test. Access to the crack growth history and the crystallographic microstructure allow for qualitative analysis of fatigue crack – microstructure interactions and provides valuable input for refinement and benchmarking of image based crystal plasticity finite element calculations.
关键词： texture,fatigue cracks,microstructural barriers,X-ray diffraction contrast tomography,residual strain,X-ray orientation imaging,annealing twins,X-ray phase contrast tomography
更新于2025-09-10 09:29:36
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Niobium oxynitride prepared by thermal NH3 nitridation as a photoanode material for solar water splitting
摘要： Niobium oxynitride (NbON) is a promising photoanode material for photoelectrochemical water splitting using visible light up to ~600 nm in wavelength. However, the NH3 nitridation method widely used for oxynitride synthesis cannot convert Nb2O5 (Nb5+) to crystalline NbON (Nb5+), due to the generation of NbOxNy (Nb2+-3+). To prevent Nb reduction during nitridation, we added O2 as an oxidant to the NH3 nitridation reaction system. Investigation of the relationship between O2 concentration and the crystal phase of the resulting samples revealed that Nb2O5 nitridation produces crystalline NbON (Nb5+) within a specific O2 concentration range. The O2 concentration required to synthesize NbON increases from 0.05% to over 0.40% upon increasing the nitridation temperature from 600 °C to 750 °C. The photoelectrochemical properties of NbON films were also investigated. Under simulated sunlight illumination, a NbON photoanode produced a photocurrent of 0.6 mA cm-2 at 1.2 V vs. RHE in H2O2 aqueous solution.
关键词： B. Optical properties,C. X-ray diffraction,D. Electrochemical properties,A. Nitrides,A. Ceramics
更新于2025-09-10 09:29:36
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Structural, optical and magnetic properties of YIG and TbErIG nanofilms prepared using a sol-gel method
摘要： A series of yttrium iron garnet (YIG) and terbium erbium iron garnet (TbErIG) nanocrystalline films were successfully grown using a sol-gel method. A crystalline analysis carried out using an X-ray diffractometer confirmed that all films had a single-phase garnet structure. The TbErIG films annealed in O2 and Ar gas had a larger number of crystallisation peaks, with a lattice constant that was close to the standard value for ErIG. The transparency increased from 94% for YIG (O2) to 98% for TbErIG (O2) films in the near-infrared region. All films were soft ferrite materials, as indicated by their magnetic hysteresis loops. The value of saturated magnetisation was increased for samples annealed in air, and was markedly decreased for samples subjected to O2 and Ar atmospheres. An increase in the coercivity value (91 Oe) was also observed for the TbErIG (Ar) film. YIG and TbErIG showed a phase transition from ferrimagnetic to paramagnetic at the Curie temperature, Tc = 556 K and 557.3 K, respectively. The low saturation magnetisation, low optical absorption and highly crystalline structure of TbErIG (O2 and Ar) films mean that these films may potentially be used in a magneto-optical compact isolator in the visible and NIR regions.
关键词： nanostructures,Sol-gel,magnetic properties,X-ray diffraction,optical properties
更新于2025-09-10 09:29:36
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Role of the reactive sputtering deposition power in the phase control of cobalt oxide films
摘要： The influence of the reactive magnetron sputtering deposition power on determining the stoichiometry and structure of cobalt oxide polycrystalline films is investigated using experimental and simulated data. Direct current discharges with powers in the 80–240 W range are tested using a metallic Co target and an Ar + O2 plasma. X-ray diffraction results show that lower deposition powers favor the spinel Co3O4 phase, while higher powers produce films presenting the rocksalt CoO phase. Computer simulations indicate that lower power processes occur in the poisoned target regime, while higher power depositions favor the metallic target regime. Consistent with the simulations, oxygen optical emissions (OI = 777:3 m) from the plasma show a significant decrease while the cobalt emissions (e.g., the CoI = 340:5 nm line) are significantly increased when the deposition power is increased. The results show that the film stoichiometry and structure are directly related to the deposition power, at constant O2 flow.
关键词： optical emissions,deposition power,X-ray diffraction,reactive sputtering,cobalt oxide,phase control
更新于2025-09-10 09:29:36
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Concurrent monitoring of zeroth-order and diffraction-order interference fringes for mosaicking echelle
摘要： A mosaicking method for echelles is proposed. The ‘‘zero-order’’ and diffraction-order interference fringes of the echelle can be imaged simultaneously on the detector using a mirror–echelle structure designed. The five-dimensional mosaicking errors are divided into two categories for elimination using the ‘‘zero order’’ and the diffraction order. During the experiments, adjustment devices for the mosaicking errors are installed on two echelles for these two categories to avoid mechanical coupling. As theoretical analysis, we follow the experimental steps to obtain a mosaicked echelle.
关键词： Diffraction,Mosaicked echelle,Interferometry
更新于2025-09-10 09:29:36
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Structural and dielectric properties of BaTi0.5 (Co0.33 Mo0.17) O3 perovskite ceramic
摘要： The polycrystalline sample BaTi0.5 (Co0.33 Mo0.17) O3 was synthesized by the sol-gel method. The effect of replacing titanium by cobalt and molybdenum on the structural and electrical properties of our compound was investigated. The results of X-ray diffraction (XRD) at room temperature showed a pure tetragonal perovskite. The electrical response was studied by complex impedance spectroscopy over a broad frequency range (30 - 106 Hz) at different temperatures. The values of ac conductivity were fitted by Jonscher’s law σ(ω) = σDC + Aωn and supported by the correlated barrier hopping (CBH) mechanism. Complex impedance analysis confirmed the existence of an electrical relaxation in the compound. The dielectric constant and the dielectric loss decreased with the increase in frequency. This behavior can be explained by the presence of the Maxwell–Wagner type of polarization responsible for the electric conduction. The modulus plots were characterized by the Havriliak–Negami (H-N) and the empirical Kohlrausch–Williams–Watts (K.W.W.) functions. The Normalized plot of the imaginary part of modulus indicates that the dynamical processes are temperature independent.
关键词： Impedance spectroscopy,Sol-gel processes,Permittivity,X-ray diffraction,Conductivity
更新于2025-09-10 09:29:36
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Effect of gamma irradiation dose on the structure and pH sensitivity of ITO thin films in extended gate field effect transistor
摘要： Even though several studies have demonstrated the use of Indium Tin Oxides (ITO) as an extended gate field effect transistor (EGFET), the effect of different doses of gamma radiation on the intrinsic properties of the ITO films has not been considered. This study investigates the effect of gamma irradiation on the structural, optical, morphological and electrical properties as well as pH sensitivity (as an extended gate field effect transistor) of ITO thin films. ITO thin films with thickness of 400 nm were prepared using a radio frequency sputtering technique. The samples were then subjected to various doses of gamma radiation from a Co-60 radio-isotope (0.5 kGy, 1 kGy, 1.5 kGy, and 2 kGy). The structural and morphological changes as well as transmission and absorption of the thin films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field-Emission Scanning Electron Microscope (FESEM) and UV-Vis spectrophotometry, before and after irradiation. The irradiated ITO thin films were then used as an extended gate field effect transistor to determine its ability to improve sensitivity as pH sensors. The grain size and transmittance in the range 300-900 nm of the ITO films were found to decrease with increasing gamma irradiation dose. In contrast, the uniformity and surface roughness of ITO thin films increased with increasing gamma radiation dose due to the formation of lattice defects. Moreover, the electrical resistance of the thin films increased with increasing dose because of the low current density and high number of surface defects associated with irradiation. The pH sensitivity of the ITO thin films improved after irradiation, possibly due to the concomitant increase in surface roughness with increasing radiation dose. The improvements in the pH sensitivity of ITO thin films after irradiation justify their potential use as pH sensors.
关键词： EGFET,pH sensor,Optical band gap,Gamma irradiation,X-ray diffraction,Indium Tin Oxide,Thin films
更新于2025-09-10 09:29:36
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Development and evaluation of realistic optical cell models for rapid and label-free cell assay by diffraction imaging
摘要： Methods for rapid and label-free cell assay are highly desired in life science. Single-shot diffraction imaging presents strong potentials to achieve this goal as evidenced by past experimental results using methods such as polarization diffraction imaging flow cytometry. We present here a platform of methods toward solving these problems and results of optical cell model (OCM) evaluations by calculations and analysis of cross-polarized diffraction image (p-DI) pairs. Four types of realistic OCMs have been developed with two prostate cell structures and adjustable refractive index parameters to investigate the effects of cell morphology and index distribution on calculated p-DI pairs. Image patterns have been characterized by a gray-level co-occurrence matrix (GLCM) algorithm and 4 GLCM parameters and linear depolarization ratio δL have been selected to compare calculated against measured data of prostate cells. Our results show that the irregular shapes of and heterogeneity in refractive index (RI) distributions for organelles play significant roles in the spatial distribution of scattered light by cells in comparison to the average RI values and their differences among the organelles. Discrepancies in GLCM and δL parameters between calculated and measured p-DI data provide useful insight for understanding light scattering by single cells and improving OCM.
关键词： cell models,light scattering,diffraction imaging,cell analysis
更新于2025-09-10 09:29:36
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Surface structures of tellurium on Si(111)–(7?×?7) studied by low-energy electron diffraction and scanning tunneling microscopy
摘要： The Te-covered Si(111) surface has received recent interest as a template for the epitaxy of van der Waals (vdW) materials, e.g. Bi2Te3. Here, we report the formation of a Te buffer layer on Si(111)–(7×7) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While deposition of several monolayer (ML) of Te on the Si(111)–(7×7) surface at room temperature results in an amorphous Te layer, increasing the substrate temperature to 770 K results in a weak (7×7) electron diffraction pattern. Scanning tunneling microscopy of this surface shows remaining corner holes from the Si(111)–(7×7) surface reconstruction and clusters in the faulted and unfaulted halves of the (7×7) unit cells. Increasing the substrate temperature further to 920 K leads to a Te/Si(111)–(2√3×2√3)R30° surface reconstruction. We find that this surface configuration has an atomically flat structure with threefold symmetry.
关键词： scanning tunneling microscopy,surface reconstruction,Si(111),tellurium,low-energy electron diffraction
更新于2025-09-10 09:29:36
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Real-time coherent diffraction inversion using deep generative networks
摘要： Phase retrieval, or the process of recovering phase information in reciprocal space to reconstruct images from measured intensity alone, is the underlying basis to a variety of imaging applications including coherent diffraction imaging (CDI). Typical phase retrieval algorithms are iterative in nature, and hence, are time-consuming and computationally expensive, making real-time imaging a challenge. Furthermore, iterative phase retrieval algorithms struggle to converge to the correct solution especially in the presence of strong phase structures. In this work, we demonstrate the training and testing of CDI NN, a pair of deep deconvolutional networks trained to predict structure and phase in real space of a 2D object from its corresponding far-field diffraction intensities alone. Once trained, CDI NN can invert a diffraction pattern to an image within a few milliseconds of compute time on a standard desktop machine, opening the door to real-time imaging.
关键词： phase retrieval,deep learning,coherent diffraction imaging,real-time imaging,neural networks
更新于2025-09-10 09:29:36