Xi'an Jiaotong University

About: Xi'an Jiaotong University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Heat transfer & Dielectric. The organization has 85440 authors who have published 99682 publications receiving 1579683 citations. The organization is also known as: '''Xi'an Jiaotong University''' & Xi'an Jiao Tong University.

Grain-orientation-engineered multilayer ceramic capacitors for energy storage applications.

Abstract: Dielectric ceramics are highly desired for electronic systems owing to their fast discharge speed and excellent fatigue resistance. However, the low energy density resulting from the low breakdown electric field leads to inferior volumetric efficiency, which is the main challenge for practical applications of dielectric ceramics. Here, we propose a strategy to increase the breakdown electric field and thus enhance the energy storage density of polycrystalline ceramics by controlling grain orientation. We fabricated high-quality -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics, in which the strain induced by the electric field is substantially lowered, leading to a reduced failure probability and improved Weibull breakdown strength, on the order of 103 MV m−1, an ~65% enhancement compared to their randomly oriented counterparts. The recoverable energy density of -textured NBT-SBT multilayer ceramics is up to 21.5 J cm−3, outperforming state-of-the-art dielectric ceramics. The present research offers a route for designing dielectric ceramics with enhanced breakdown strength, which is expected to benefit a wide range of applications of dielectric ceramics for which high breakdown strength is required, such as high-voltage capacitors and electrocaloric solid-state cooling devices. The energy density of dielectric ceramic capacitors is limited by low breakdown fields. Here, by considering the anisotropy of electrostriction in perovskites, it is shown that -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 ceramics can sustain higher electrical fields and achieve an energy density of 21.5 J cm−3.

Nanoscale simulation of shale transport properties using the lattice Boltzmann method: permeability and diffusivity

Abstract: Porous structures of shales are reconstructed using the markov chain monte carlo (MCMC) method based on scanning electron microscopy (SEM) images of shale samples from Sichuan Basin, China. Characterization analysis of the reconstructed shales is performed, including porosity, pore size distribution, specific surface area and pore connectivity. The lattice Boltzmann method (LBM) is adopted to simulate fluid flow and Knudsen diffusion within the reconstructed shales. Simulation results reveal that the tortuosity of the shales is much higher than that commonly employed in the Bruggeman equation, and such high tortuosity leads to extremely low intrinsic permeability. Correction of the intrinsic permeability is performed based on the dusty gas model (DGM) by considering the contribution of Knudsen diffusion to the total flow flux, resulting in apparent permeability. The correction factor over a range of Knudsen number and pressure is estimated and compared with empirical correlations in the literature. For the wide pressure range investigated, the correction factor is always greater than 1, indicating Knudsen diffusion always plays a role on shale gas transport mechanisms in the reconstructed shales. Specifically, we found that most of the values of correction factor fall in the slip and transition regime, with no Darcy flow regime observed.

Enhanced Photocatalytic Hydrogen Evolution over Cu-Doped ZnIn2S4 under Visible Light Irradiation

Abstract: A series of Cu-doped ZnIn2S4 photocatalysts has been synthesized by a facile hydrothermal method, with the copper concentration varying from 0 wt% to 2.0 wt%. The physical and photophysical properties of these Cu-doped ZnIn2S4 photocatalysts were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), and UV−visible diffuse reflectance spectroscopy (UV−vis). The diffuse reflectance and photoluminescence spectra of Cu-doped ZnIn2S4 shifted monotonically to longer wavelengths as the copper concentration increased from 0 wt% to 2.0 wt%, indicating that the optical properties of these photocatalysts greatly depended on the amount of Cu doped. Meanwhile, the layered structure of ZnIn2S4 would be destructed gradually by Cu doping. The photoactivity of ZnIn2S4 was enhanced when Cu2+ was doped into the crystal structure. The highest photocatalytic activity was observed on Cu (0.5 wt%)–doped ZnIn2S4, with the rate of hydrogen evolution to be 151.5 μmol/h u...

Improved measurement of electron antineutrino disappearance at Daya Bay

Abstract: With 2.5× the previously reported exposure, the Daya Bay experiment has improved the measurement of the neutrino mixing parameter sin^2 2θ_(13) = 0.089 ± 0.010(stat) ± 0.005(syst). Reactor anti-neutrinos were produced by six 2.9 GW_(th) commercial power reactors, and measured by six 20-ton target-mass detectors of identical design. A total of 234,217 anti-neutrino candidates were detected in 127 days of exposure. An anti-neutrino rate of 0.944±0.007(stat)±0.003(syst) was measured by three detectors at a flux-weighted average distance of 1648 m from the reactors, relative to two detectors at 470 m and one detector at 576 m. Detector design and depth underground limited the background to 5 ± 0.3% (far detectors) and 2 ± 0.2% (near detectors) of the candidate signals. The improved precision confirms the initial measurement of reactor anti-neutrino disappearance, and continues to be the most precise measurement of θ_(13).