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Evolution of microstructure and mechanical properties of a graded TiAlON thin film investigated by cross-sectional characterization techniques
摘要： In the last years, quaternary oxynitrides have emerged as a new class of materials due to their tunable properties. Within the present work, a graded TiAl(O)N film was grown by magnetron sputter deposition, using TiAl targets with a Ti/Al atomic ratio of 40/60, constant nitrogen and stepwise increasing oxygen partial pressure over the film thickness. The microstructural evolution of the film was investigated by transmission electron microscopy and synchrotron X-ray nanodiffraction. Complementary, cross-sectional μ-Raman spectroscopy was performed to further validate the phase evolution. The first layer, grown without the addition of oxygen, showed a prevalent wurtzite (w) structure and a subordinate face centered cubic (fcc) phase fraction. The addition of small amounts of oxygen resulted in the stabilization of the fcc-phase and the w-phase vanished. With increasing film thickness and thus, increasing oxygen content, increasing amounts of an additional amorphous phase fraction were observed. In the first layers, tensile in-plain strain was determined, which turns to compressive towards the film surface. Cross-sectional nanonindentation revealed increasing hardness and elastic modulus with increasing oxygen content in the first layers as a result of the w to fcc transition; however, towards the film surface the hardness decreases, which can be related to the increasing amorphous phase fraction.
关键词： sputtering,TiAlON,graded film,cross-sectional nanoindentation,synchrotron X-ray nanodiffraction,TEM
更新于2025-09-04 15:30:14
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Absolute Configurations of Naturally Occurring [5]- and [3]-Ladderanoic Acids: Isolation, Chiroptical Spectroscopy, and Crystallography
摘要： We have isolated mixtures of [5]- and [3]-ladderanoic acids 1a and 2a from the biomass of an anammox bioreactor and have separated the acids and their phenacyl esters for the first time by HPLC. The absolute configurations of the naturally occurring acids and their phenacyl esters are assigned as R at the site of side-chain attachment by comparison of experimental specific rotations with corresponding values predicted using quantum chemical (QC) methods. The absolute configurations for 1a and 2a were independently verified by comparison of experimental Raman optical activity spectra with corresponding spectra predicted using QC methods. The configurational assignments of 1a and 2a and of the phenacyl ester of 1a were also confirmed by X-ray crystallography.
关键词： absolute configurations,quantum chemical methods,Raman optical activity,X-ray crystallography,ladderanoic acids,HPLC,anammox bioreactor
更新于2025-09-04 15:30:14
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Reductive Dissolution Mechanisms at the Hematite-Electrolyte Interface Probed by <i>In Situ</i> X-ray Scattering
摘要： The electron-catalyzed dissolution and reprecipitation of iron (oxyhydr)oxides constitute critical steps in natural geochemical iron cycling. However, the atomic-scale mechanisms of reductive dissolution and oxidative precipitation of Fe2+ remain poorly understood because they are difficult to directly experimentally probe. Using in situ synchrotron X-ray scattering and a novel electrochemical cell, we interrogate the interfacial structure between the hematite (α-Fe2O3) (1102) surface and acidic aqueous solution (5 mM Na2SO4, pH 4.0) under controlled electrochemical potential from open circuit to cathodic bias as the reductive dissolution potential is approached and then exceeded. The crystalline order of the surface improves under mild reducing conditions, and the surface Fe stoichiometry changes with cathodic bias. After significant reductive dissolution occurs and cathodic bias is removed, dissolved Fe is re-deposited, forming a disordered interface. Unlike at circumneutral pH, water layers at the hematite interface with acidic solution are poorly ordered, likely due to the adsorption of sulfate from the electrolyte. These results provide a novel atomic-scale view into the behavior of reducible transition metal oxide surfaces under fluctuating (electro)chemical conditions.
关键词： X-ray scattering,hematite,interface structure,electrochemical potential,reductive dissolution
更新于2025-09-04 15:30:14
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The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics || Fundamentals of Ray Tracing
摘要： A ray is defined as the collection of straight-line path segments followed by an energy bundle from its point of emission to its point of absorption. The definition includes the possibility of intermediate reflection, scattering, refraction, and even diffraction events. Ray tracing involves the application of basic mathematics to the process of identifying the intersection of ray segments with surfaces. Most engineering and science students acquire the required mathematical tools long before they enter university. The current chapter provides a review of the mathematical principles governing ray tracing and the related issues of meshing and indexing.
关键词： Monte Carlo Method,Radiation Heat Transfer,Applied Optics,Mathematical Principles,Ray Tracing
更新于2025-09-04 15:30:14
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The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics || Extension of the MCRT Method to Non-Diffuse, Non-Gray Enclosures
摘要： The assumption of diffuse emission and diffuse-specular reflection in gray enclosures is adequate for many applications encountered in engineering practice. This is especially true in the conceptual and preliminary design stages. However, final design and performance studies often require the use of bidirectional surface optical models restricted to a specified wavelength interval. In this chapter we develop the concept of the band-averaged spectral radiation distribution factor, which is the most general tool available for treating radiant exchange among surfaces, but first we learn through extended examples how to compose and use models to simulate the optical behavior of non-diffuse surfaces.
关键词： Monte Carlo Ray-Trace Method,Non-Gray Enclosures,Radiation Heat Transfer,Applied Optics,Bidirectional Spectral Surfaces,Non-Diffuse
更新于2025-09-04 15:30:14
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Aurophilicity and Photoluminescence of (6-Diphenylpnictogenoacenaphth-5-yl)gold Compounds
摘要： The organotin precursors 6-Br-Ace-5-SnBu3 (6, Ace = acenaphthyl) and 6-Ph2E-Ace-5-SnBu3 (7a: E = P; 7b: E = As; 7c: E = Sb) were prepared and used for the synthesis of organogold complexes, namely, the homodinuclear arylgold(I) species (6-Ph2E-Ace-5-Au)2 (8a: E = P; 8b: E = As; 8c: E = Sb), arylgold(III) dichloride 6-Ph2P-Ace-5-AuCl2 (9), diarylgold(III) chloride [trans-(6-Ph2P-Ace-5-)2Au]Cl ([10]Cl) as well as the heterodinuclear gold complexes 6-Ph2P(AuX)-Ace-5-Au(AsPh3) (11a: X = Cl; 11b: X = Br). Compounds 8a - 8c, 11a, and 11b show significant aurophilic interactions, which are related to their photoluminescence upon exposure to UV light. In the solid state, 11a and 11b show green-yellow emission, whereas 8a - 8c are non-emissive. In solution under an argon atmosphere, all five compounds 8a - 8c as well as 11a and 11b show green-yellow emission. The organogold complexes were characterized by multinuclear NMR spectroscopy, photoluminescence spectroscopy, single-crystal X-ray crystallography as well as (TD-)DFT calculations including real-space bond indicators derived from atoms-in-molecules (AIM), the electron localization indicator (ELI-D), and the non-covalent interaction (NCI) index.
关键词： DFT calculations,aurophilicity,photoluminescence,X-ray crystallography,NMR spectroscopy,organogold complexes
更新于2025-09-04 15:30:14
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<i>In situ </i>soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces
摘要： In situ soft x-ray absorption spectroscopic study of polycrystalline Fe/MgO interfaces. It is found that at the interface of iron and MgO film, about two monolayers of Fe3O4 is formed. Fe3O4 being the oxide of iron with the highest heat of formation, the reaction appears to be controlled thermodynamically. On the other hand, on the interface with MgO (001) surface, FeO is formed, suggesting that the reaction is limited by the availability of oxygen atoms. Magnetic behavior of the FeO layer gets modified significantly due to proximity effect of the bulk ferromagnetic iron layer.
关键词： FeO,soft x-ray absorption spectroscopy,Fe/MgO interfaces,Fe3O4,magnetic behavior
更新于2025-09-04 15:30:14
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Cascaded systems analysis of a-Se/a-Si and a-InGaZnO TFT passive and active pixel sensors for tomosynthesis
摘要： Medical imaging systems like full field digital mammography (FFDM) and digital breast tomosynthesis (DBT) commonly use amorphous selenium (a-Se) based passive pixel sensor (PPS) direct conversion x-ray detectors. On one hand, direct conversion detectors inherently offer better resolution characteristics in terms of a higher modulation transfer function (MTF), in comparison to the indirect CsI:Tl PPS x-ray imager. On the other hand, especially at lower doses, this superior performance of the direct imager is seldom retained in its detective quantum efficiency (DQE) curves. It is well known that a-Se PPS x-ray imagers suffer from high additive electronic noise originating from the from the amorphous silicon (a-Si) thin film transistor (TFT) array that is being used in the current back-plane technology. This degrades the noise power spectrum (NPS) and subsequently the overall DQE. To address this deficiency, we propose to replace the PPS back-plane by active pixel sensor (APS) back-plane technology, which has the potential to reduce the back-plane electronic noise by amplifying the input signal, especially at low doses. The proposed APS is based on amorphous In-Ga-Zn-O (a-IGZO) TFT technology, which can offer high mobility (5-20 cm2/V-s), low leakage current (< 10-13 A) and low flicker noise (Hooge’s parameter αH ~ 1.5 × 10-3), leading to better imager noise performance. To test our hypothesis, we used linear cascaded systems analysis to model the imaging performance (MTF, NPS and DQE) of the PPS and APS a-Se direct imagers. This model was first validated using experimentally measured data obtained for a 85 μm pixel pitch a-Se/a-Si TFT PPS imager. Using this model, we analyzed the noise performance of the direct a-Se and indirect CsI:Tl x-ray a-IGZO APS imagers at different dose and electronic noise levels. Obtained results clearly showed that lowering back-plane electronic noise can significantly improve the performance of the a-Se/a-IGZO TFT APS imager. Our simulated results showed that a higher DQE at lower radiation doses (maximum DQE of 0.6 can be achieved at an exposure level of 1 μGy) can be achieved with the a-Se detector, thereby making this combination a promising candidate for low dose applications like DBT.
关键词： cascaded analysis,active pixel sensors,amorphous selenium,x-ray detectors,metal oxide
更新于2025-09-04 15:30:14
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Advances in the measurements of the mass attenuation coefficients
摘要： The knowledge of atomic fundamental parameters, such as mass attenuation coefficients or fluorescence yields with low uncertainties, is of decisive importance in elemental quantification involving X‐ray fluorescence analysis techniques. Several databases providing the mass attenuation coefficients are accessible and frequently used within a large community of users. These compilations are most often in good agreement for photon energies in the hard X‐ray ranges. However, they significantly differ for low photon energies and around the absorption edges of the elements. Mass attenuation coefficients of several elements were determined experimentally in the photon energy range from 100 eV to 35 keV by using monochromatized radiation at the SOLEIL synchrotron (France). The application of high‐accuracy experimental techniques resulted in low uncertainty mass attenuation coefficients. The results are compared with tabulated data.
关键词： photon energy,X‐ray fluorescence analysis,mass attenuation coefficients,SOLEIL synchrotron
更新于2025-09-04 15:30:14
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Catalyst-Assisted Solution–Liquid–Solid Synthesis of CdS/CuInSe <sub/>2</sub> and CuInTe <sub/>2</sub> /CuInSe <sub/>2</sub> Nanorod Heterostructures
摘要： Axial nanowire heterostructures composed of cadmium sulfide (CdS)/copper indium diselenide (CuInSe2) and copper indium telluride (CuInTe2)/copper indium diselenide (CuInSe2) were synthesized by a solution?liquid?solid (SLS) method with the catalyzer of bismuth nanocrystals. Electron microscopy and diffraction studies show CuInTe2 and CuInSe2 segments growing along the [112] direction with a clear epitaxial interface between them. In CdS/CuInSe2 nanorod heterostructures, CuInSe2 and CdS segments grow along the [112] and [111] direction, respectively, with an obvious epitaxial interface between them. Energy-dispersive X-ray spectrometry demonstrates the alloy-free composition modulation in two nanorod heterostructures. In CuInTe2/CuInSe2 nanorod heterostructures, Te and Se are localized in CuInTe2 and CuInSe2 segments, respectively. Cu/In/Se and Cd/S are localized in the CuInSe2 and CdS sections of the CdS/CuInSe2 nanorod heterostructures. This research confirms that the SLS mechanism provides a general alternate technique to prepare multicomponent axial 1D heterostructures that have been difficult to generate by using either catalyst-free solution-phase synthesis or vapor?liquid?solid growth.
关键词： epitaxial interface,nanowire heterostructures,solution?liquid?solid (SLS) method,bismuth nanocrystals,energy-dispersive X-ray spectrometry
更新于2025-09-04 15:30:14