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Herein, two types of Fc-based hypercrosslinked polymers (HHCP and DHCP) with high BET surface area (953.9 and 1062.7 m2 g−1) were prepared by direct one-step phenolic polycondensation aiming at high uptake capacity towards H2. As expected, the hydrogen uptake values of HHCP and DHCP were notably higher than those of porous polymers with a higher surface area under the same conditions. The maximum H2 uptake of HCPs at 77 K/1.0 bar are determined to be 2.51 wt % for HHCP and 2.74 wt % for DHCP, respectively. Despite the pore structure playing a determinant role in hydrogen adsorption, the adsorption sites in the polymer framework can be another essential factor to influence the hydrogen adsorption capacity. The interactions between the Fc building block and H2 are revealed by DFT calculation to fully illustrate the role of Fc in H2 adsorption. The results indicate that both iron atoms and benzene rings in Fc-based HCPs contribute to the adsorption of hydrogen. Moreover, it is interesting to find that the most stable adsorption site around the Fc building unit is the position directly above the Cp ring. The results in this work may more reasonably explain the phenomenon that the introduction of Fc units could enhance the adsorption of H2 in many studies, which also provides possible insights into the application of metallocene compounds in H2 adsorption.

A fiber-reinforced polymer (FRP)-steel composite bars (FSCBs), with an inner steel core and outer FRP jacket, is a novel type of reinforcement designed to inherit good durability and ductility suitable for seawater sea sand concrete structures. The long-term tensile behavior of FSCBs in chloride environments is important. The long-term tensile behavior of glass-type FSCBs with different fiber layer thicknesses under chloride environment attack was investigated in this study. FSCBs with an inner steel bar of fixed diameter (8 mm) and an outer FRP jacket of three thicknesses (2, 4, and 6 mm) were used for research. Seawater-immersion accelerated-aging experiments at three different aging temperatures (23, 40, and 60 °C) and aging times (1, 6 and 12 months) were conducted. The failure modes, equivalent elastic modulus, pseudo strain hardening moduSTlus, and tensile strength retention of the FSCBs under the above mentioned aging temperatures and times were analyzed. The experimental results determined that the chloride environment had no significant effect on the equivalent elastic modulus of the FSCBs. However, the pseudo-strain hardening modulus of the FSCBs decreased with increasing aging time. Moreover, the tensile strength retention of the FSCBs decreased with increasing temperature under the same aging time and FSCBs diameter. A prediction model for the tensile strength retention of FSCBs with different FRP layer thicknesses at different aging temperatures and times was proposed and validated. The results provided a better understanding of the durability of FSCBs in marine hydrothermal environments to establish the criteria and standards of design.

Synthetic fibers are adopted to mix with conventional steel fibers (SF) for ultra-high performance concrete (UHPC) to improve chemical resistance and reduce self-weight. Polyoxymethylene fiber (POMF), as a type of lightweight, high-strength, corrosion-resistant synthetic fiber, is expected to replace SF generally used in UHPC. Due to the obvious difference of mechanical properties between POMF and SF, different POMF/SF hybrid ratios may affect the dynamic compression behavior of UHPC. To investigate the dynamic mechanical behavior of hybrid POMF/SF reinforced UHPC (HUHPC), axial compression and split Hopkinson pressure bar (SHPB) tests with strain rate from 40 to 170 s−1 of HUHPC were conducted. The fiber volume fraction was fixed at 3% and four different POMF/SF hybrid ratios (0:3, 1:2, 2:1, 3:0) were adopted. The effects of hybrid POMF/SF ratios on the dynamic compressive properties of HUHPC, including dynamic compressive strength, dynamic elastic modulus, dynamic increase factor (DIF), and impact toughness were discussed. The results show that HUHPC exhibits obvious strain rate sensitivity under impact loading. With the increase of strain rate, the dynamic compressive strength, dynamic elastic modulus, DIF and impact toughness of HUHPC increased. Based on the linear assumption of fiber volume fraction and dynamic compressive strength enhancement of UHPC, the calculated dynamic compressive strength of HUHPC is lower than the experimental values. As the strain rate increases, the propagation path of microcrack transforms from interface of fiber-matrix to penetrating the fiber, resulting in plastic deformation of SF and fracture of POMF, consuming a large amount of impact energy and improving the impact toughness resistance of HUHPC.

This work investigated the relationship between the morphology of AlFeSi intermetallics compounds (IMCs) and grains, and its influence on the corrosion behavior of the surface of Al–Mg–Si alloy laser welds. Due to the segregation of solute elements on the grain boundary, coarse AlFeSi IMCs were more likely to precipitate along the grain boundary. As a result, the “linear-like” AlFeSi IMCs was only found along the straight grain boundary of columnar grains, leading to the deterioration of corrosion resistance, but for the equiaxed grains, only small rod-like AlFeSi IMCs was along the grain boundary. Compared to the small rod-like AlFeSi IMCs at GBs of equiaxed grains, the “linear-like” AlFeSi IMCs at the straight GBs of columnar grains increased the interface area between α-Al, leading to a more evident intergranular corrosion at columnar boundary.

This work investigated the transformation of Fe-bearing intermetallics and its influence on the corrosion behavior of Al–Mg–Si alloy weld joints. The results showed that the size and type of Fe-bearing intermetallics determined the pitting corrosion resistance of weldment regions. The partially melted zone (PMZ) suffered most serious corrosion attack, because of the formation of coarse needle-like β-AlFeSi. The heat-affected zone (HAZ) immediately behind the PMZ (HAZ-Ⅰ) experienced a complete transformation of β-AlFeSi into α-AlFeSi, but in the rest of the HAZ (HAZ-Ⅱ) was not sufficient for this transformation. Therefore, the HAZ-Ⅰ was more resistant to pitting corrosion than HAZ-Ⅱ.