Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal\ndoped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu\nsingle crystal with dimensions of 10* 10* 10 mm^3 was irradiated by X-rays. The emission light\nphoton intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range\nfrom 50 to 130 kV. The results of this work were compared with data obtained under similar\nconditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce\nsingle crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of\noptical sensors, was also examined. The AE of the 10* 10* 10 mm^3 CaF2:Eu crystal peaked in the\nrange from 70 to 90 kV (22.22 efficiency units; E.U). The light emitted from CaF2:Eu is compatible\nwith photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used\nas radiation sensors in medical imaging systems. Considering the AE results in the examined\nenergies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal\ncould be considered for radiographic applications, including the detection of charged particles and\nsoft gamma rays....
Ce-doped nano-a-Fe2O3 was successfully synthesized via the hydrothermal method. The\nproperties of the prepared particles were studied by X-ray diffraction (XRD), scanning electron\nmicroscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray\nphotoelectron spectroscopy (XPS) and electrochemical methods. It was found that the Ce element\ncan be doped into the a-Fe2O3 lattice resulting in lattice distortion, which can refine the grain and\nimprove the crystal surfaceâ??s integrity significantly. In addition, doping of Ce element can shorten the\nFe-O bond length in the a-Fe2O3 crystal, cause a blue shift of the stretching vibration band, enhance\nbinding energy of Fe-O and the chemical stability of the a-Fe2O3 crystal....
We investigated arc ion-plated Al70Cr30N and Al80Cr20N thin films deposited with three\ndifferent bias voltages (50 V, 100 V, and 150 V) to study crystal phase stabilities, residual stresses,\nand mechanical properties. Commercial compositions of AlxCr100-xN coatings typically range from x\n=50 to 70 where the cubic face centered crystal phase occurs. The present study focuses on films near\nthe solubility limit of Al in the cubic Cr(Al)N lattice around 70 at.%, above which hexagonal AlN\n(h-AlN) starts to form in significant amounts. Residual stress values are obtained by two methods:\ngrazing incidence diffraction with the whole pattern fitting and the conventional side inclination\nmethod (sin2Y method). When multiple phases are present in the film, whole pattern fitting turns\nout to be particularly effective and a comparison of both measurement methods will be discussed.\nThe Al70Cr30N films consist of the cubic phase with crystallite sizes of about 70 nm for all bias\nvoltages. Compressive stress increased with bias voltage from about 3 to almost 6 GPa and coatings\nbecome brittle. Al80Cr20N films showed a different dependence on bias voltage. Using 50 V bias\nvoltage in deposition, the major phase is h-AlN phase with a crystallite grain size of < 30 nm and\n(0002) preferred orientation. With increasing bias the cubic phase is stabilized also reaching about\n70 nm crystallite size. In general, the compressive residual stress was significantly lower than for\nAl70Cr30N films for the same bias voltages which may be a result of the presence of the hexagonal\nphase. Wear and scratch tests confirmed higher ductility of the Al80Cr20N variants but reduced\nresistance of the films in impact wear testing....
By analyzing the three-dimensional digital model of a real carbon paper gas diffusion layer\n(GDL) reconstructed by X-ray computed tomography (CT), it was found that fibers are not distributed\nat any angle but within a certain range. The fiber orientation can be represented by fiber pitch (i.e., the\nangle between a single fiber and the in-plane direction). The effect of fiber orientation on stochastic\nreconstruction and transport properties (permeability) was investigated in this paper to find which\nfiber pitch range can achieve a better GDL on fluid flow. First, the actual fiber pitch was measured by\nanalyzing SGL-24BA images obtained by X-ray CT. Also, seven different ranges of fiber pitch were\nrandomly chosen to reconstruct GDL. Then, the permeability of these digital models was calculated\nusing the Lattice Bolzmann Method (LBM) and discussed to obtain the fiber pitch range of the optimal\npermeability......................
Water plays a vital role on the hydromechanical behavior of unsaturated soils. An important concern in unsaturated soil\nmechanics is to determine the distribution of water within voids and its interaction with soil grains. This paper presents some\nresults of the spatial distribution of water in different soils using the synchrotron-based X-ray microcomputed tomography\n(micro-CT). Three materials (glass beads, natural sand, and clay) were first prepared at a water content of about 10%, statically\ncompacted under vertical total stress of 500 kPa, and then scanned by synchrotron X-rays at an energy of 18 or 20 keV. The three dimensional\n(3D) microstructure of the samples including air, liquid, and solid phases was reconstructed, and some new\nobservations were obtained: (i) the iodine-based contrast medium (KI) can increase the peak greyscale value of water from 110 to\n122, enhance the air-water contrast, and thus facilitate the segmentation of water phase; (ii) in the compacted glass beads and sand,\nwater distribution is characterized using the micro-CT and image reconstruction technique. The water contents obtained by phase\nsegmentation, i.e., 10.2% and 9.3%, are comparable with those measured by the oven-drying method, i.e., 9.7% and 9.4% for the\nglass beads and sand, respectively; (iii) water is preferably distributed within aggregates when it is mixed with the oven-dried\nparticles, and an aggregate-dominated 3D structure is observed. However, it is impossible to determine the water phase for the\nstudied material even with the resolution of 0.65 micro m/pixel....
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