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A small energy offset (ΔE < 0.2 eV) between Γ(pxy) and Γ(pz) band orbitals in AB2X2 Zintl compounds enables the realization of band alignment for an increased band degeneracy as well as an enhanced electronic performance. The SrMg2Bi2 Zintl compound has been theoretically illustrated to have a small ΔE, suggesting an approximately inherent convergence of two band orbitals. Therefore, this work is devoted to the revelation of the thermoelectric potential of the SrMg2Bi2 Zintl compound in a broad Hall carrier concentration of 0.3–5 × 1019 cm−3 by Ag-doping at the Sr site. The electrical transport properties can be well predicted by the single parabolic band model with acoustic phonon scattering, which reveals a multi-band transporting behavior in the heavily doped samples due to Fermi level deepening, leading to a significant zT-enhancement. In terms of the model, a peak zT of up to 1.0 is achievable by assuming the amorphous minimum lattice thermal conductivity, which demonstrates this compound as a promising thermoelectric material. [ABSTRACT FROM AUTHOR]

The metal flow is complicated and will be affected by the dimensions of the rolling deformation zone during the rolling of doubly curved sheet metal surfaces. The dimensions of the rolling deformation zone are mainly affected by the rolling reduction and the central cross-section diameters of rollers. The work studied the influences of central cross-section diameters of rollers on the longitudinal bending deformation of formed spherical surfaces and the stability of the rolling process combined with the rolling reduction. The results showed that the larger the central cross-section diameters of rollers, the more stable the rolling process, and the better the shape accuracy of formed spherical surfaces. When the central cross-section diameters of rollers were relatively small, the longitudinal bending deformation of formed spherical surfaces increased with the increased central cross-section diameters of rollers. However, an excessively large roller diameter restrained the longitudinal bending deformation of the sheet. When the central cross-section diameters of rollers were relatively large, the longitudinal bending deformation of formed spherical surfaces decreased with the increased central cross-section diameters of rollers. The results can be used as a reference for designing rollers to ensure that formed doubly curved surfaces can obtain greater longitudinal bending deformations and better shape accuracy under the same rolling reduction. [ABSTRACT FROM AUTHOR]

The 3D curved parts rolling based on rigid arc-shaped rollers is a novel plastic forming process for rapidly manufacturing curved parts with double curvature. This work proved that the method can form different types of 3D curved parts through small adjustments of the rolling reduction without replacing the rollers. The study found that when the generatrix radius of the convex roller is smaller than that of the concave roller, the distribution rule of uneven roll gap could vary with the change of the rolling reduction. Therefore, the forming method can change the distribution rule of uneven roll gaps by adjusting the rolling reduction to form different types of curved parts (spherical parts, saddle-shaped parts, or cylindrical parts). The relationship between the rolling reduction and the distribution rule of roll gaps is studied by analytical, finite element, and experiment method. And the influence of the rolling reduction on the bending deformation of different types of curved parts is studied. The research results show that the longitudinal bending deformation of formed curved parts is greatly affected by the rolling reduction. The longitudinal curvature of formed saddle-shaped parts decreases with the increase of the rolling reduction, and the longitudinal curvature of formed spherical parts increases with the increases of the rolling reduction. The transverse bending deformation of formed curved parts is little affected by the rolling reduction. [ABSTRACT FROM AUTHOR]

A one-dimensional yolk-shell Sb2O3/TiO2 composite with excellent lithium-storage properties has been successfully fabricated, including preparation of one-dimensional Sb2O3 precursor and coating of TiO2 film. As an anode material for lithium-ion batteries (LIBs), the Sb2O3/TiO2 composite can display the initial discharge specific capacity of 1285 mAh g−1 at a current density of 100 mA g−1 and maintain a discharge specific capacity of 579 mAh g−1 after 100 cycles, approximately 2.7 times as high as the pure Sb2O3. The excellent lithium-storage properties can be attributed to the synergistic effect between the one-dimensional structural Sb2O3 and the TiO2 film, in which the external TiO2 shell can effectively restrain the volume expansion during the charge and discharge cycle, making the electrochemical reaction highly reversible. [ABSTRACT FROM AUTHOR]

Rolling technology based on arc-shaped rollers is a novel method for rapid manufacturing of 3D curved parts. The method uses a pair of arc-shaped rollers (a convex roller and a concave roller) as forming tools, forming an unevenly distributed roll gap. The sheet metal has both transverse bending and longitudinal uneven extension during rolling, so that surface parts with double curvature are processed. The curvature of the formed surface part can be changed by changing the rolling reduction. Changing the vertical distance between the rollers will cause the overall change of the roll gap height, which will inevitably have a great impact on the forming effect of formed 3D curved parts. In this paper, a finite element model and experiment with different rolling reductions was designed; the influence of rolling reduction on the bending deformation and shape accuracy of formed 3D curved parts was studied. The results show that, with the slight increase of rolling reduction (from 0.04 to 0.12 mm), the longitudinal bending deformation of the formed 3D curved part increases significantly, but its transversal bending is almost not affected. When the maximum rolling reduction is 0.04 and 0.06 mm (the corresponding minimum rolling reduction is less than or equal to zero), the shape accuracy of the formed 3D curved parts is not good enough; when the maximum rolling reduction is greater than 0.06 mm (the corresponding minimum rolling reduction is greater than zero), the shape accuracy of the formed 3D curved parts is significantly better. This indicates that, for the rolling of 3D curved parts based on arc-shaped rollers, ensuring that the minimum rolling reduction is greater than zero is the key to ensuring good shape accuracy of the formed 3D curved parts. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) has a wide range of applications in the treatment and prevention of major diseases owing to its high sensitivity and excellent resolution. However, there is still much room for optimization in the readout circuit and fast pulse sampling to further improve the performance of the PET scanner. In this work, a LIGHTENING ® PET detector using a 13 × 13 lutetium-yttrium oxyorthosilicate (LYSO) crystal array read out by a 6 × 6 silicon photomultiplier (SiPM) array was developed. A novel sampling method, referred to as the dual time interval (DTI) method, is therefore proposed to realize digital acquisition of fast scintillation pulse. A semi-cut light guide was designed, which greatly improves the resolution of the edge region of the crystal array. The obtained flood histogram shown that all the 13 × 13 crystal pixels can be clearly discriminated. The optimum operating conditions for the detector were obtained by comparing the flood histogram quality under different experimental conditions. An average energy resolution (FWHM) of 14.3% and coincidence timing resolution (FWHM) of 972 ps were measured. The experimental results demonstrated that the LIGHTENING ® PET detector achieves extremely high resolution which is suitable for the development of a high performance time-of-flight PET scanner. [ABSTRACT FROM AUTHOR]