[en] The microstructure and mechanical properties of independently designed and manufactured Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.06Sr high strength aluminum alloy was investigated and the effect of pre-recovery on the alloy’s performance was also studied. The results show that pre-recovery heat treatment has little effect on the alloy’s crystal orientation, but it can consume deformation energy, reduce recrystallization driving force, inhibit recrystallization and decrease dislocation density ( the dislocation density decreased from 0.501 to 0.320 × 10¹⁴ m⁻²). Moreover, pre-recovery heat treatment can dramatically increase the electrical conductivity of this alloy (the maximum electrical conductivity increased from 28.55% IACS to 34.01% IACS), however, the hardness all decreased after pre-recovery treatment, but the drop is very small. In addition, pre-recovery heat treatment can significantly improve the alloy’s resistance to intergranular corrosion (the minimum intergranular corrosion depth decreased from 62.67 μm to 47.43 μm), however, the effect of pre-recovery heat treatment on the alloy’s resistance to exfoliation corrosion is negligible. (paper)

[en] A novel modified separator was synthesized with an ultraviolet irradiated polypropylene (PP) membrane and acrylonitrile monomers by a solution grafting reaction. It was demonstrated that polyacrylonitrile (PAN) was grafted on the PP separator surface by analyzing the results of FESEM, ATR–FTIR and XPS. The thermostability and wettability of the PAN-grafted PP (PP-g-PAN) separator were enhanced. Then, Li–S batteries were assembled using the modified separators. The cycling and rate capacity performance is improved clearly because of the higher liquid uptake, smaller porous size, better polysulfides absorption effect and interfacial affinity of the grafted separator. The modified separator can hinder the movement of Li₂S_x effectively to prevent the shuttle effect of a Li–S battery. Therefore, this efficient method has great potential to be applied to the modification of other kinds of polymer membranes.

[en] It is a challenging task to promote the activity and selectivity of a catalyst via precisely engineering the microenvironment, an important factor related with the catalytic performance of natural catalysts. Motivated by the water effect in promoting the catalytic activity explored in this work, a nanoreactor modified with phosphine ligand enabled the efficient hydrogenation of benzoic acid (BA) over Ru nanoparticles (NPs) in organic solvent under mild conditions, which cannot be achieved in unmodified nanoreactors. Both density functional theory (DFT) calculations and catalytic performance tests showed that the phosphine ligands can manipulate the adsorption strength of BA on Ru NPs by tuning the surface properties as well as preferentially interacting with the carboxyl of BA. The insights obtained in the present study provide a novel concept of nanoreactor design by anchoring ligands near catalytically active centers. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

[en] The dynamic dipole polarizabilities for 1S, 2S and 3S states of the hydrogen atom are calculated using the finite B-spline basis set method, and the magic wavelengths for 1S-2S and 1S-3S transitions are identified. In comparison of the solutions from the Schroedinger and Dirac equations, the relativistic corrections on the magic wavelengths are of the order of 10^-2nm. The laser intensities for a 300-E_r-deep optical trap and the heating rates at 514 and 1371 nm are estimated. The reliable prediction of the magic wavelengths would be helpful for the experimental design on the optical trapping of the hydrogen atoms, and in turn, it would be helpful to improve the accuracy of the measurements of the hydrogen 1S-2S and 1S-3S transitions. (authors)

[en] Highlights: • In the weak-magnetic-field approximation, we calculated the hyperfine-induced Landé $g$-factors of the ${}^3{P}_0^o$ clock states in ${}^{27}$Al${}^{+}$ and ${}^{87}$Sr by using the multi-configuration Dirac–Hartree–Fock method. The present results, $\delta g_{\text{hfs}}^{\left(1\right)}\left({}^3{P}_0^o\right)=-1.183\left(6\right)\times {10}^{-3}$ for ${}^{27}$Al${}^{+}$ and $\delta g_{\text{hfs}}^{\left(1\right)}\left({}^3{P}_0^o\right)=7.78\left(30\right)\times {10}^{-5}$ for ${}^{87}$Sr, agree with experimental values very well. • We also estimated the contributions from perturbing states to the $g$-factors concerned so as to truncate the summation over the perturbing states without loss of accuracy. • The computational uncertainties were systematically analyzed. In the weak-magnetic-field approximation, we calculated the hyperfine-induced Landé $g$-factors of the ${}^3{P}_0^o$ clock states in ${}^{27}$Al${}^{+}$ and ${}^{87}$Sr by using the multi-configuration Dirac–Hartree–Fock method. The present results, $\delta g_{\text{hfs}}^{\left(1\right)}\left({}^3{P}_0^o\right)=-1.183\left(6\right)\times {10}^{-3}$ for ${}^{27}$Al${}^{+}$ and $\delta g_{\text{hfs}}^{\left(1\right)}\left({}^3{P}_0^o\right)=7.78\left(30\right)\times {10}^{-5}$ for ${}^{87}$Sr, agree with experimental values very well. The influence of relativistic effects and electron correlations on the involving hyperfine interaction and Zeeman matrix elements, and energy separations were investigated in detail. We also estimated the contributions from perturbing states to the $g$-factors concerned so as to truncate the summation over the perturbing states without loss of accuracy. Based on these, the computational uncertainties were systematically analyzed for the hyperfine-induced Landé $g$-factors of the ${}^3{P}_0^o$ clock states in these two atomic systems.

[en] We have investigated the damage for ZrO₂/SiO₂ 800nm 45^o high-reflection mirror with femtosecond pulses. The damage morphologies and the evolution of ablation crater depths with laser fluences are dramatically different from that with pulse longer than a few tens of picoseconds. The ablation in multilayers occurs layer by layer, and not continuously as in the case of bulk single crystalline or amorphous materials. The weak point in damage is the interface between two layers. We also report its single-short damage thresholds for pulse durations ranging from 50 to 900 fs, which departs from the diffusion-dominated τ_P^1/2 scaling. A developed avalanche model, including the production of conduction band electrons (CBE) and laser energy deposition, is applied to study the damage mechanisms. The theoretical results agree well with our measurements