- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Photoluminescence emission from nanostructured porous preparations of CdSa??ZnTiO <sub/>3</sub> assembled nanoparticles
摘要： This study reports the structural and optical properties of CdS/ZnTiO3 nanocomposites prepared using a chemical bath and different titanate concentrations. Commercial ZnTiO3 nanoparticles were introduced into a chemical bath that had been used to produce CdS semiconductor nanoparticles (NPs). Here, the growing CdS crystallites precipitated onto the suspended zinc titanate NPs. X-ray diffraction patterns revealed that samples of CdS/ZnTiO3 nanopowders were made of cubic ZnTiO3 and hexagonal CdS wurtzite. The morphology of the particles was studied using transmission electron microscopy and scanning electron microscopy images. These images demonstrated the different characteristics of the CdS/ZnTiO3 nanocomposites and their dependence on titanate concentration when placed into the CdS-growing solution. Photoluminescence spectra showed three main emission bands for the electron transitions in the CdS/ZnTiO3 composite. This composite produced three photoluminescence bands, the intensities of which depended on composite shape, which in turn depended on the relative concentrations of CdS and ZnTiO3.
关键词： CdS/ZnTiO3 nanocomposites,transmission electron microscopy,X-ray diffraction,chemical bath,photoluminescence,scanning electron microscopy
更新于2025-09-19 17:13:59
-
Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting
摘要： The influence that complex component geometries can have on microstructure formation is investigated in a rocket engine impeller fabricated of a Ti-6Al-4V alloy by selective laser melting (SLM). The SLM melt pool monitoring, indicative of the component’s thermal history during processing, is linked to the bulk mapping of martensite decomposition obtained by high energy synchrotron X-ray diffraction. In addition to the martensitic and lamellar microstructures typically obtained during SLM of Ti-6Al-4V, spheroidization is identified to take place in the component’s down-skin regions. Grain boundary migration may contribute to the latter effect. Small recrystallized grains form along grain boundaries.
关键词： Titanium alloys,X-ray diffraction,Microstructure,Selective laser melting,Synchrotron radiation
更新于2025-09-19 17:13:59
-
Diffractive dipolar coupling in non-Bravais plasmonic lattices
摘要： Honeycomb plasmonic lattices are paradigmatic examples of non-Bravais lattices. We experimentally measure surface lattice resonances in effectively free-standing honeycomb lattices composed of silver nanospheres. By combining numerical simulations with analytical methods, we analyze the dispersion relation and the near-field properties of these modes along high symmetry trajectories. We find that our results can be interpreted in terms of dipole-only interactions between the two non-equivalent triangular sublattices, which naturally lead to an asymmetric near-field distribution around the nanospheres. We generalize the interaction between the two sublattices to the case of variable adjacent interparticle distance within the unit cell, highlighting symmetry changes and diffraction degeneracy lifting associated to the transition between Bravais and non-Bravais lattices.
关键词： honeycomb plasmonic lattices,surface lattice resonances,non-Bravais lattices,diffraction degeneracy lifting,silver nanospheres,near-field properties,dipole-only interactions
更新于2025-09-19 17:13:59
-
Supercooled Liquid β-Diketones with Mechanoresponsive Emission
摘要： Shear-induced crystallization of dyes in the amorphous state is an effective strategy for generating higher energy emission after mechanical perturbation—a rare phenomenon in mechanoresponsive materials. Recently, we reported that a β-diketone with a 3,4,5-trimethoxy-substituted phenyl ring formed a stable supercooled liquid (SCL) phase after melting and cooling in air. To tune the lifetime of β-diketones in the SCL phase, a series of dyes with 3,4,5-trimethoxy-substituted phenyl rings were synthesized. Derivatives with naphthyl and phenyl rings were prepared in order to modulate crystallization through arene interactions. Additionally, dyes were substituted with alkoxy chains of varying length to promote crystallization through increased van der Waals interactions. Video screening in conjunction with differential scanning calorimetry and X-ray diffraction studies indicated that naphthyl-substituted derivatives exhibited increased melted state lifetimes and that increasing the alkoxy chain length can induce crystallization. Analysis of molecular packing of single crystals of PH, PC1, PC3, and PC5 revealed that the central para-substituted methoxy group of the trimethoxy-substituted ring was forced out of the molecular plane because of steric interactions with neighboring methoxy groups. The stabilities of the SCLs were generally correlated with the torsion angles of the para methoxy groups, where derivatives with smaller angles exhibited faster rates of crystallization. Mechanical perturbation of the SCL phases resulted in shear-induced crystallization of PH, PC1, PC3, and NC6 derivatives. In some cases, traditional mechanochromic luminescence with a crystalline-to-amorphous phase transition was also observed, which indicates that some trimethoxy-substituted β-diketones exhibit more than one type of mechanoresponsive luminescence.
关键词： van der Waals interactions,supercooled liquid (SCL),mechanochromic luminescence,mechanoresponsive materials,X-ray diffraction,β-diketone,Shear-induced crystallization,differential scanning calorimetry
更新于2025-09-19 17:13:59
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Chalcogenide Glass Fiber Components for the Fabrication of Mid-Infrared Optical Sources
摘要： The positioning of electromagnetic (EM) sources on the complex plane, though a mathematical construct, is often applied in solving EM problems with directive confined (collimated) propagation characteristics. Equivalent dipole modeling, which finds its application in characterizing various current sources can be computationally expensive for large structures. Here, the complex localization of equivalent source points combined with the particle swarm optimization is used to improve the performance of the equivalent dipole modeling.
关键词： Complex source point,edge dipoles,diffraction,particle swarm optimization,equivalent dipole model,feature selective validation
更新于2025-09-19 17:13:59
-
Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD
摘要： Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process.
关键词： X-ray diffraction (XRD),residual stresses,AlSi10Mg,selective laser melting,surface roughness
更新于2025-09-19 17:13:59
-
Decoding the structure of interfaces and impurities in 2D materials by photoelectron holography
摘要： The properties of atomically thin materials essentially depend on their structures, including impurities, defects and interfaces with underlying substrates. Thus, the detailed structural information is relevant for creation of 2D materials with desired properties. Here, we explore the capabilities of photoelectron diffraction and holography for structural analysis of atomically thin layers using as examples such systems as h-BN, graphene, and modified graphene with boron impurities. We show that for planar 2D crystals with commensurate interface to the substrate, it is possible to visualize the interface and impurities with high spatial resolution, and to distinguish possible non-equivalent structural units. Our approach applied to B-doped graphene on Ni(1 1 1) and Co(0 0 0 1) surfaces has allowed to reveal asymmetry of boron concentrations in the two carbon sublattices and established its dependence on the applied synthesis procedure and chosen substrate. The obtained results suggest that such approach can be widely applied for studies of various 2D systems, where the structures of interfaces and defects are of remarkable importance.
关键词： doping,structure,photoelectron diffraction,graphene,hexagonal boron nitride,photoelectron holography
更新于2025-09-19 17:13:59
-
Residual stress in laser cladded heavy-haul rails investigated by neutron diffraction
摘要： Residual stress is one of the critical parameters affecting the fatigue behaviour of tribological components, which can be introduced by a thermo-mechanical process such as laser cladding. In this study, the residual stress distribution of laser cladded rails was evaluated using a neutron diffraction technique. The substrate rail for the laser cladding was hypereutectoid rail steel used in Australian heavy-haul railway track, and the cladding materials were 410L (a low carbon content stainless steel alloy) and Stellite 6 (a Co-based alloy). The cladding materials were selected based on their high wear, corrosion and fatigue resistance properties. This study measured the residual stress in full-scale laser cladded rails where the residual stresses were measured in the cladding layer, heat affected zone (HAZ) and substrate zone of the railhead. A new sample preparation strategy was developed to quantify the residual stresses in the full-scale rails with high spatial resolution. Higher compressive residual stress was found in the cladding layer, which may have resulted from the martensitic transformation occurred in that region. Tensile stresses occurred in the HAZ to a depth of 4 mm, which might be mainly caused by thermal contraction and volumetric change in the microstructure. The addition of a second cladding layer did not significantly affect the magnitude of the residual stresses, but the peak tensile residual stress shifted to a deeper location from the surface, which is beneficial in resisting wear. Post-cladding heat treatment significantly reduced the undesirable high residual stress from the cladding layer and HAZ.
关键词： Post-cladding heat treatment,Residual stress,Neutron diffraction,Laser cladding,Heavy-haul rail
更新于2025-09-16 10:30:52
-
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
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Electromagnetic Diffraction by Fractal Dusts, Triangles and Carpets: A Kirchhoff Approach to Circulation
摘要： The diffraction of plane waves by perfectly-conducting thin screens is of fundamental physical and mathematical interest in electromagnetics [1]. Classic laser-optics experiments involve both open (single- and double-slit arrangements) and closed (circular and regular-polygon) apertures, with analyses often being confined to the Fresnel [2] and Fraunhofer [3] regimes. Here, we consider a class of scattering problem involving fully-2D fractal screens, where the scatterer possesses the property of self-similarity. A more general formulation of the diffracted wave, based on Kirchhoff’s theory and 3D Green’s functions [4], is also deployed.
关键词： Kirchhoff’s theory,self-similarity,diffraction,Green’s functions,fractal screens
更新于2025-09-16 10:30:52