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Mechanical behavior, microstructural evolution and texture analysis of AA2024-T351 processed by multi-layer friction surfacing with high build rates
No full textSolid-state additive manufacturing (AM) processes such as multi-layer friction surfacing (MLFS) can overcome typicaldisadvantages of fusion-based AM such as high residual stresses, porosity or hot cracking. The tool-less process setup ofMLFS prevents contamination of the resulting components, e.g., caused by wear or the use of lubricants. The present studyinvestigates MLFS for the precipitation-hardenable alloy AA2024-T3 using a process parameter that yields a high buildrate relevant for industrial applications. The fatigue performance is shown and the microstructural and the mechanicalanisotropy is examined. The fatigue properties in deposition direction show a high cycle fatigue limit of 170.5 MPa anda decrease in the maximum stress level compared to the base material due to precipitate overageing. The microstructureshows a Brass{011}⟨211⟩ texture at the bottom of the layers due to the application of high axial forces. In the center of thelayer, no preferred texture was observed, while B{̄112}⟨110⟩/ ̄B{1̄1̄ 2}⟨̄1̄10⟩ shear textures were observed at the top part ofthe deposited layers. An elongated grain morphology with aspect ratios above 2 is present over the entire layer height. Thesemicrostructural characteristics cause anisotropy in mechanical properties, with highest ultimate tensile strength and elongationin deposition direction, i.e., 408 ± 5 MPa and 18 ± 3 % respectively, and the lowest values along the build direction,i.e., 377 ± 21 MPa and 9 ± 3 % respectively. The observed behavior is of considerable importance for the industrial designand application of components manufactured with MLFS as they show that MLFS can also result in anisotropic materialproperties, depending on the chosen process parameters. It requires careful selection of the right combination of stud materialand process parameters to achieve isotropic properties in the deposited structure
Interpolating families of integrable AdS3 backgrounds
No full textWe construct families of integrable deformations that interpolate between and either or . They preserve half of the supersymmetry of the original background, namely one copy of the algebra. From this it follows a similar integrable interpolation between and , which also preserves half of the supersymmetry, namely a copy of the algebra. In all cases, the interpolating backgrounds are constructed by using TsT transformations, which makes it easy to implement them in the integrability formalism in the full quantum theory. To illustrate this point, we discuss the lightcone gauge fixing of the models and compute their pp-wave Hamiltonian
Flavored Circular Collider: cornering New Physics at FCC-ee via flavor-changing processes
No full textWe illustrate the potential of a future high-intensity collider running at the pole in probing extensions of the Standard Model via precise measurements of flavor-changing processes. We illustrate this potential both within effective field theories and simplified models inspired by current -physics data, focusing on selected flavor-physics measurement projections at FCC-ee, and by the theoretically well-motivated scenario of TeV-scale new physics predominantly coupled to third-generation fields. In particular, we demonstrate the key role played by the interplay among different flavor-physics measurements, and between flavor and electroweak measurements, in cornering the New Physics parameter space. Updated constraints on new physics, in the limit that no deviations from the Standard Model are observed, are also presented
NNLO+PS Double Higgs boson production with top-quark mass corrections in GENEVA
No full textWe present the implementation of the NNLO QCD corrections to double Higgs boson production at hadron colliders in GENEVA, matched to the parton shower. We include all the known top-quark mass effects and the resummation of large logarithms of the zero-jettiness , up to NNLL accuracy. This work extends our previous study, which was performed in the infinite top-quark mass approximation, providing a more realistic simulation framework for Higgs boson pair production. We validate our approach against NNLO predictions by MATRIX and assess the importance of mass effects comparing with our previous implementation
MeV cosmic-ray electrons modify the TeV pair-beam plasma instability
No full textRelativistic pair beams created in the intergalactic medium (IGM) by TeV gamma rays from blazars are expected to produce a detectable GeV-scale electromagnetic cascade, but the cascade component is absent in the spectra of many hard-spectrum TeV-emitting blazars. One common explanation is that weak intergalactic magnetic fields deflect the electron–positron pairs away from our line of sight. An alternative possibility is that electrostatic beam-plasma instabilities drain the energy of these pairs before a cascade can develop. Recent studies have shown that beam scattering by oblique electrostatic modes leads to minimal energy loss. But these modes might be suppressed by linear Landau damping (LLD) due to MeV-scale cosmic-ray electrons in the IGM. In this work, we explore the impact of LLD on the energy-loss efficiency of plasma instabilities in pair beams associated with 1ES 0229+200. We find that LLD effectively suppresses oblique electrostatic modes, while quasi-parallel ones grow to larger amplitudes. In this way, LLD enhances the energy-loss efficiency of the instability by more than an order of magnitude
High‐Performance Phototransistor Based on a 2D Polybenzimidazole Polymer
No full textPhotodetectors are fundamental components of modern optoelectronics, enabling the conversion of light into electrical signals. The development of high-performance phototransistors necessitates materials with both high charge carrier mobility and robust photoresponse. However, achieving both in a single material poses challenges due to inherent trade-offs. Herein, this study introduces a polybenzimidazole-(1,3-diazole)-based 2D polymer (2DPBI), synthesized as few-layer, crystalline films covering ≈28 cm2 on the water surface at room temperature, with large crystalline domain sizes ranging from 110 to 140 µm2. The 2DPBI incorporates a π-conjugated photoresponsive porphyrin motif through a 1,3-diazole linkage, exhibiting enhanced π-electron delocalization, a narrow direct band gap of ≈1.18 eV, a small reduced electron–hole effective mass (m* = 0.171 m0), and a very high resonant absorption coefficient of up to 106 cm−1. Terahertz spectroscopy reveals excellent short-range charge carrier mobility of ≈240 cm2 V−1 s−1. Temperature-dependent photoconductivity measurements and theoretical calculations confirm a band-like charge transport mechanism. Leveraging these features, 2DPBI-based phototransistors demonstrate an on/off ratio exceeding 108, photosensitivity of 1.08 × 107, response time of 1.1 ms, and detectivity of 2.0 × 1013 Jones, surpassing previously reported standalone few-layer 2D materials and are on par with silicon photodetectors. The unique characteristics of 2DPBI make it a promising foundation for future optoelectronic devices
Understanding Mn-modulated restructuring of Fe-based catalysts for controlling selectivity in CO hydrogenation to olefins
No full textFor CO hydrogenation over iron-based catalysts, revealing the promoting effect of manganese and the nature of catalytically active sites remains a challenge that hinders targeted catalyst design. Here we elucidate the manganese-modulated restructuring of such catalysts during preconditioning and CO hydrogenation using in situ X-ray absorption spectroscopy. The reaction-induced decoration of the surface of iron carbide with a MnO-containing layer is essential to hinder methane formation in favour of C–C olefins and C hydrocarbons. The selectivity changes were rationalized via spatially resolved steady-state and time-resolved (micro)kinetic tests combined with density functional theory calculations. The promoter affects the ability of iron carbide to generate surface species from H, CO and CH, thus controlling the surface C/H ratio, which is decisive for product selectivity. Consequently, the design of efficient multi-component heterogeneous catalysts requires a thorough understanding of the optimal catalyst architecture and, in particular, how to generate and stabilize it under reaction conditions
Plasmonic Polymorphs by Combining Shape Anisotropy and Soft Interactions in Bipyramid Thin Films
No full textThin-film plasmonic supercrystals of pentagonal gold nanobipyramids (AuBP) exhibit a diverse range of packing structures that influence the near-field distribution of the enhanced electric field and the far-field response. By varying the molecular weight of the coating ligands, the softness of the anisotropic building blocks is changed. A thorough structural characterization reveals that this affects the resulting superstructures from self-assembly more intricately than with isotropic building blocks. Softer coatings lead to smaller aligned domains in monolayers, while bilayers exhibit more crystalline domains with dominant interlayer twist angles near 0° and 90°. The far-field distribution and near-field response are measured using micro-absorbance and electron energy loss spectroscopy (EELS). Correlating these data with high-resolution transmission electron microscopy (HR-TEM) structural analysis enabled the identification of the longitudinal and transverse individual and collective plasmonic modes. Notably, for large crystalline bilayer domains, a strong polarization-dependent optical response is observed. These features underline the potential of these superstructures for applications in surface-enhanced spectroscopies, plasmonic photocatalysis, and advanced optical manipulation in switchable optical metamaterials
Three-point functions from integrability in orbifold theories
No full textBesides solving the spectral problem of Super-Yang-Mills (SYM) theory, integrability also provides us with tools to compute the structure constants of the theory, most prominently through the hexagon formalism. We show that, with minor modifications, this formalism can also be applied to orbifolds of SYM theory, which are integrable theories in their own right.To substantiate this claim, we test our results against a direct gauge theory calculation at tree-level. We focus here on a family of supersymmetric -orbifold theories. BPS-correlators in these theories have recently been investigated with independent localisation techniques and a tentative matching with wrapping-corrections in the hexagon formalism was observed. Together with our weak-coupling evidence, this suggests that a full determination of the structure constants of orbifold theories at finite coupling may be within reach
A Green and Efficient Electrocatalytic Route for the Highly‐Selective Oxidation of C−H Bonds in Aromatics over 1D CoO ‐Based Nanoarrays
No full textElectrocatalytic oxidation of C−H bonds in hydrocarbons represents an efficient and sustainable strategy for the synthesis of value-added chemicals. Herein, a highly selective and continuous-flow electrochemical oxidation process of toluene to various oxygenated products (benzyl alcohol, benzaldehyde, and benzyl acetate) is developed with the electrocatalytic membrane electrodes (ECMEs). The selectivity of target products can be manipulated via surface and interface engineering of CoO-based electrocatalysts. We achieved a high benzaldehyde selectivity of 90 % at a toluene conversion of 47.6 % using 1D CoO nanoneedles (NNs) loaded on a microfiltration (MF) titanium (Ti) membrane, i.e, CoO NNs/Ti. In contrast, the main product shifted to benzyl alcohol with a selectivity of 90.1 % at a conversion of 32.1 % after modifying MnO2 nanosheets (NSs) on Co3O4 NNs/Ti (CoO@MnO/Ti) catalyst. Moreover, benzyl acetate product can be obtained with a selectivity of 92 % at a conversion of 58.5 % at high current density (>1.5 mA cm−2), demonstrating that the pathway of toluene oxidation is readily maneuvered. DFT results reveal that modifying MnO on CoO optimizes the electron structure of CoO@MnO/Ti and modulates the adsorption behavior of intermediate species. This work demonstrates a sustainable, efficient, and continuous-flow process for precise control over the production selectivity of value-added oxygenated derivatives in the electrochemical oxidation of aromatic hydrocarbons