Effect of surface organic modified layered double hydroxide on UV ageing resistance of bitumen

Layered double hydroxide (LDH) was surface organic modified by γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560) and applied to improve UV ageing resistance of bitumen. KH560 has been successfully grafted to the surface of LDH according to Fourier Transform Infrared Spectroscopy. Then, the effect of KH560 surface modified LDH (KH560-LDH) and LDH on physical and rheological properties of bitumen were thoroughly investigated. The results showed that KH560-LDH existed more stably in bitumen and KH560-LDH-modified bitumen possessed better high-temperature performance compared with LDH. After UV ageing, the properties of bitumen became worse obviously. Compared with LDH, KH560-LDH exhibited better improvement on UV ageing resistance of bitumen.     

镍铝层状双氢氧化物正极锌镍电池充放电性能

在化学共沉淀法的基础上采用喷涂技术制备镍铝层状双氢氧化物,对产物进行了结构表征和物理性能测试,并用作正极活性物质制备锌镍实验电池,考察了电池的充放电性能.果表明,合成样品晶型结构为单-α相,颗粒形貌呈不规则角块状,比表面积达到14.1m2/g,平均粒径为18.8μm.球形β-Ni(OH)2正极锌镍电池相比,实验电池的循环稳定性、放电容量和电压平台均有明显提高,1 C倍率充放电120次循环平均比容量达到287.4mAh/g,放电中值电压达到1.688 V.     

Ca–Al layered double hydroxides-derived Ni-based catalysts for hydrogen production via auto-thermal reforming of acetic acid

Biomass-derived acetic acid (HAc) is an alternative resource for hydrogen production, and heat self-sustained auto-thermal reforming (ATR) of HAc shows potential for practical application, while robust and stable catalysts remain as a key factor. Ca–Al layered double hydroxides (LDHs)-derived Ni-based catalysts were synthesized by co-precipitation, and tested in ATR of HAc for hydrogen production. Over the LDHs-derived Ca_2.55Ni_0.45AlO_4.5 catalyst, active sites of Ni–CaO–Ca₁₂Al₁₄O₃₃ were formed, and interaction among Ni, CaO and Ca₁₂Al₁₄O₃₃ was proved to be a pivotal role for 1) thermal stability, 2) resistance to oxidation of Ni⁰ species, and 3) inhibiting coke deposition through catalytic cycle, CaO + CO₂↔CaCO₃ and CaCO₃+*C↔CaO+2CO, for gasification of coking precursors. Hence, the Ca_2.55Ni_0.45AlO_4.5 catalyst showed enhanced activity with no obvious deactivation in ATR: the acetic acid conversion rate was 100%, and the hydrogen yield remained stable near 2.75 mol-H₂/mol-HAc at a rate of 40.34 mmol-H₂/s/g-catalyst.     

Computational modeling of high performance cementitious thin shell elements under in-plane shear

High-performance cementitious materials are widely used in the construction of thin shell elements. This study investigates a simulation method based on composite layered shells for the nonlinear analysis of high-performance cementitious elements under in-plane shear. A tube torsion test is simulated and analyzed with MSC-MARC and its results are compared to an alternative calculation method, the Simplified Model for Combined Stress resultants (SMCS), as well as with experimental data. The simulation method is found to produce accurate results for fully under-reinforced elements with a range of strong to weak reinforcement ratios less than 2.     

Chemical interpretation,enhanced ferroelectric property and dielectric breakdown strength of CuO-added Sr2Nb2O7 ceramics

The structural interpretation and electrical properties of perovskite layer structured (PLS) Sr₂Nb₂O₇-xwt%CuO ceramics prepared by solid-state reaction method are investigated. The chemical interpretation of enhanced piezoelectricity is confirmed to be attributed to the rotation and/or distortion of oxygen octahedron caused by possible Cu²⁺ substitution at the A-site of Sr₂Nb₂O₇ by XRD refinement and variable-temperature Raman spectra. Sr₂Nb₂O₇-xwt%CuO (x?=?0.3, 0.5 and 0.7) ceramics shows enhanced ferroelectric properties with a larger P_r of ～4.1?μC/cm² and a smaller E_c of ～63.1?kV/cm. This study further explains the cations in A-site play a major structural role in the polarization process for PLS system. It was found that dielectric breakdown strength increases up to 258.8?kV/cm and then decreases gradually with the increase of CuO content. Impedance spectroscopy indicated that CuO addition could be helpful in increasing the grain boundary resistance then dielectric breakdown strength.     

Rapid Characterization of Ultrathin Layers of Chalcogenides on SiO2/Si Substrates

There has been emerging interest in exploring single‐sheet 2D layered structures other than graphene to explore potentially interesting properties and phenomena. The preparation, isolation and rapid unambiguous characterization of large size ultrathin layers of MoS₂, GaS, and GaSe deposited onto SiO₂/Si substrates is reported. Optical color contrast is identified using reflection optical microscopy for layers with various thicknesses. The optical contrast of these thin layers is correlated with atomic force microscopy (AFM) and Raman spectroscopy to determine the exact thickness and to calculate number of the atomic layers present in the thin flakes and sheets. Collectively, optical microscopy, AFM, and Raman spectroscopy combined with Raman imaging data are analyzed to determine the thickness (and thus, the number of unit layers) of the MoS₂, GaS, and GaSe ultrathin flakes in a fast, non‐destructive, and unambiguous manner. These findings may enable experimental access to and unambiguous determination of layered chalcogenides for scientific exploration and potential technological applications.     

Propagation of TH-waves in a pre-stressed layered formation

In this article we present new results concerning TH-waves propagation in pre-stressed layered materials. Our results generalize, for initial mechanical fields, classical results from seismology concerning Love wave propagation. Here, we obtain and analyze the dispersion relations into a parallel-sided plate, respectively into a layer on a substrate structure for various classes of anisotropy. We derive the energy density and the energy flux distribution for a Love type wave. We obtain and analyze the mean energy density and mean energy flux, respectively, the total mean energy density and total mean energy flux.     

Effects of layered double hydroxides on the thermal and flame retardant properties of intumescent flame retardant high density polyethylene composites

In this study, two layered double hydroxides (LDHs), ZnAl-LDH, and MgAl-LDH, were combined with intumescent flame retardant (IFR) consisting of ammonium polyphosphate and tris (2-hydroxyethyl) isocyanurate to prepare flame retardant high density polyethylene composites. The thermal and flame retardant properties of these composites were investigated by thermogravimetric analysis, limiting oxygen index measurement, and cone calorimetry, while the morphology and chemical structure of the char residue were analyzed by scanning electron microscopy, Fourier transfer infrared spectroscopy, and laser Raman spectroscopy. The results showed that the peak heat release rate (PHRR) of both HD/IFR/Zn-LDH and HD/IFR/Mg-LDH composites was 52.0% and 12.0% lower than that of HD and HD/IFR, respectively, suggesting that there was no difference in the reduction of PHRR between the two LDHs. The use of LDHs resulted in the formation of compact char residue with a high graphitic degree, but no significant increase in tensile strength.