321034 research outputs found
Sort by
Impact of Humidity on Water Dynamics and Electrical Conductivity in PEDOT:PSS/Cellulose Nanofibril Nanocomposite Films: Insights from Quasi-Elastic Neutron Scattering
No full textThe water dynamics in a nanocomposite film that consists of the electrically conductive poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and cellulose nanofibrils (CNFs) have been investigated during three cycles of exposure to low and high relative humidity (RH = 5% and 85%, respectively) using quasi-elastic neutron scattering (QENS). The obtained dynamical structure factors are transformed into the imaginary part of the dynamic susceptibility to better differentiate between the individual relaxation processes. In a humid environment, two different water species are present inside the films: fast-moving bulk water and slow-moving hydration water. During the first cycle, a large amount of hydration water enhances the polymer chain mobility, eventually leading to irreversible structural rearrangements within the film. In the subsequent cycles, we observed a release of all bulk water and portions of hydration water upon drying, along with an uptake of both water species in a humid environment. The relaxation times of hydration water diffusion as a function of momentum transfer can be described by a jump-diffusion model. The obtained jump lengths, residence times, and diffusion coefficients of hydration water suggest a change in the hydration layer upon drying: water molecules around hydrophobic groups are released from the film, while the hydrogen bonds between water and hydrophilic groups are sufficiently strong to keep these molecules inside the films, even in a dry state. The QENS results can be correlated to the structural and conductive properties. In the dry state, the low hydration water content and the absence of bulk water allow for improved wetting of the CNFs by PEDOT:PSS, which eventually increases the electrical conductivity of the films
Perturbative bootstrap of the Wilson-line defect CFT: Bulk-defect-defect correlators
No full textWe study the correlators of bulk and defect half-BPS operators in = 4 Super Yang-Mills theory with a Maldacena-Wilson line defect, focusing on the case involving one bulk and two defect local operators. We analyze the non-perturbative constraints on these correlators, which include a topological sector, pinching and splitting limits: and we compute a variety of bulk-defect-defect correlators up to next-to-leading order at weak coupling, observing that transcendental terms cancel. Additionally, we study the two leading terms in the strong-coupling regime, and present partial results for the next-to-next-to-leading order
Scalable solution chemical synthesis and comprehensive analysis of BiTe and SbTe
No full textThermoelectric (TE) materials can directly convert heat into electrical energy. However, they sustain costly production procedures and batch-to-batch performance variations. Therefore, developing scalable synthetic techniques for large-scale and reproducible quality TE materials is critical for advancing TE technology. This study developed a facile, high throughput, solution-chemical synthetic technique. Microwave-assisted thermolysis process, providing energy-efficient volumetric heating, was used for the synthesis of bismuth and antimony telluride (BiTe, SbTe). As-made materials were characterized using various techniques, including XRPD, SEM, TEM, XAS, and XPS. Detailed investigation of the local atomic structure of the synthesized BiTe and SbTe powder samples was conducted through synchrotron radiation XAS experiments. Radial distribution functions around the absorbing atoms were reconstructed using reverse Monte Carlo simulations, and effective force constants for the nearest and distant coordination shells were subsequently determined. The observed differences in the effective force constants support high anisotropy of the thermal conductivity in BiTe and SbTe in the directions along and across the quintuple layers in their crystallographic structure. The as-made materials were consolidated via Spark Plasma Sintering to evaluate thermal and electrical transport properties. The sintered TE materials exhibited low thermal conductivity, achieving the highest TE figure-of-merit values of 0.7 (573 K) and 0.9 (523 K) for n-type BiTe and p-type SbTe, respectively, shifted significantly to the high-temperature region when compared to earlier reports, highlighting their potential for power generation applications. The scalable, energy- and time-efficient synthetic method developed, along with the demonstration of its potential for TE materials, opens the door for a wider application of these materials with minimal environmental impact
Probing the Limits of Mechanical Stability of the Mesoporous Metal–Organic Framework DUT-76(Cu) by Hydrocarbon Physisorption
No full textThe mechanical robustness of MOFs is crucial in most adsorption-related applications. Herein, we investigated the interaction of the mesoporous metal–organic framework DUT-76(Cu) with various C1–C4 hydrocarbons at their boiling points. During adsorption, the pore structure partially collapsed into an amorphous phase while retaining a residual porosity. We employed a combination of multicycle physisorption experiments using different hydrocarbons (methane, ethane, ethylene, propane, propylene, n-butane, and 1,3-butadiene) along with X-ray diffraction, scanning electron microscopy, and total scattering to examine this transition. This methodology allowed us to gain a comprehensive understanding of the effects on the crystal structure, local structure, and macroscopic behavior of the material. Furthermore, we identified specific correlations among the chain length, number of double bonds, and adsorption/desorption cycle stability, which are influenced by adsorption-induced stress. These multicycle adsorption experiments served as semiquantitative tools for assessing the mechanical stability of mesoporous frameworks
Suppression of intrinsic Hall effect through competing Berry curvature in CrTe
No full textWe conducted a comprehensive analysis of the magnetic and electronic transport properties of the layered chalcogenide CrTe in its single-crystalline form. This material exhibits a ferromagnetic transition at a critical temperature of _=191K, characterized by significant thermal hysteresis in the magnetization data below this temperature. Measurements of isothermal magnetization, magnetocaloric effect, and magnetoresistance indicate that the system exhibits strong magnetocrystalline anisotropy, with the axis serving as the easy axis of magnetization. The CrTe compound shows a pronounced anomalous Hall effect (AHE); however, existing experimental and theoretical data do not provide a clear understanding of the nature and origin of this phenomenon. Our experimental findings suggest that the skew scattering mechanism primarily accounts for the observed AHE. In contrast, our theoretical study reveals the presence of gapped nodal points accompanied by nonzero Berry curvature, which are expected to contribute towards intrinsic AHE. A detailed analysis of the electronic band structure, obtained by density functional theory calculations, reveals that the Berry curvature at different nodal points exhibits both positive and negative signs. These opposing contributions largely cancel each other out, thereby significantly diminishing the intrinsic contribution to the AHE
Center-of-mass energy dependence of intrinsic- distributions obtained from Drell–Yan production
No full textThe internal motion of partons inside hadrons has been studied through its impact on very low transverse momentum spectra of Drell–Yan (DY) pairs created in hadron-hadron collisions. We study DY production at next-to-leading order using the Parton Branching (PB) method which describes the evolution of transverse momentum dependent parton distributions. The main focus is on studying the intrinsic transverse momentum distribution (intrinsic-) as a function of the center-of-mass energy . While collinear parton shower Monte Carlo event generators require intrinsic transverse momentum distributions strongly dependent on , this is not the case for the PB method. We perform a detailed study of the impact of soft parton emissions. We show that by requiring a minimal transverse momentum, , of a radiated parton, a dependence of the width of the intrinsic- distribution as a function of is observed. This dependence becomes stronger with increasing
Influence of the Ti:Al:Cr proportion on the structure and oxidation resistance of ternary intermetallic coatings produced by non-vacuum electron beam cladding
No full textTitanium is known to be a material with poor oxidation resistance. When heated, it reacts with atmospheric gases, leading to the formation of the TiO oxide film on its surface. This film does not protect the material against further oxidation. To solve this problem, heat-resistant coatings, including TiAl-based ones, are applied to titanium. This study investigates ternary Ti-Al-Cr surface layers with different concentrations of components. The protective layers were fabricated on titanium substrates by non-vacuum electron beam cladding. This method provides the formation of thick coatings (up to 2 mm in a single pass of the electron beam); however, the structure of the cladding layers can be significantly inhomogeneous. To reveal the influence of microstructural features of the coatings and the uneven elemental distribution on their oxidation behavior, detailed structural studies combined with the CALPHAD method were performed both before and after oxidation testing. It was found that an Al-rich alloy consisting primarily of the γ-phase provided the best protection against oxidation. The introduction of high concentrations of both Al and Cr yielded contradictory results. Although the L1-and C14-phases formed in the coating are predicted to contribute to the development of a protective AlO film, the oxidation resistance of this cladding layer was comparable to that of titanium. This result can be attributed to the inhomogeneity of the coating and the appearance of the B2-phase in local areas of the coating at oxidation temperature and the decomposition of the Cr-depleted C14-phase. Furthermore, the Cr-rich B2-phase provides better oxidation resistance than the α-phase of Al-lean cladding layers
Measurement of branching fractions, CP asymmetry, and isospin asymmetry for decays using Belle and Belle II data
No full textWe present measurements of and decays using a combined data sample of pairs collected by the Belle experiment and pairs collected by the Belle II experiment in collisions at the resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II data sets yields and decays. The measured branching fractions are and for and decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry and the direct CP asymmetry