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Lithium-sulfur (Li-S) batteries as extremely promising high-density energy storage devices have attracted extensive concern. However, practical applications of Li-S batteries are severely restricted by not only intrinsic polysulfides shuttle resulting from their concentration gradient diffusion and sluggish conversion kinetics but also serious safety issue caused by thermolabile and combustible polymer separators. Herein, it is presented for the first time that a robust and multifunctional separator with urchin-like Co-doped FeOOH microspheres and multiwalled carbon nanotubes (MWCNTs) as an interlayer simultaneously achieves to suppress polysulfides shuttle as well as improves thermotolerance and nonflammability of commercial PP separator. Accordingly, Li-S batteries with modified separator exhibit remarkable performance in a wide range temperatures of -25–100 °C. Typically, under 25 °C, ultrahigh initial capacities of 1441 and 827.29 mA h g−1 at 1 C and 2 C are delivered, and remained capacities of 936 and 663.18 mA h g−1 can be obtained after 500 cycles, respectively. At 0.1 C, the S utilization can reach up to 97%. Significantly, at 1 C, the batteries also deliver an excellent performance with remained capacities of high to 862.3, 608.4 and 420.6 mA h g−1 after 100, 300 and 450 cycles under 75, 0 and -25 °C, respectively. This work provides a new insight for developing stable and safe high-performance Li-S batteries.

It is extremely desirable but remains greatly challenging to obtain high-performance microwave absorption (MA) materials with thin thickness, lightweight, wide frequency bandwidth, and strong absorption by facile and low-cost preparing methods. In this work, by utilizing an inexpensively commercial melamine-formaldehyde sponge (MFS) as a template for growth of a Co-based metal-organic framework (ZIF-67) and subsequently carbonizing this ZIF-67-decorated MFS in a nitrogen atmosphere, an ultralight (8 mg cm

The mechanical properties and microstructure of geopolymer are affected by the molar ratio of SiO2/Al2O3. Meanwhile, organic polymer has the effect of improving the toughness of geopolymer, which depends on the SiO2/Al2O3 ratio of geopolymer inevitably. Therefore, it is important to investigate the effect of the organic polymer on the mechanical properties and microstructure of geopolymer with varying SiO2/Al2O3 ratio for using organic polymer to modify geopolymer. In this work, the SiO2/Al2O3 ratios of metakaolin-based geopolymers are adjusted to 2.0, 2.5, 3.0, 3.5 and 4.0 by adding silica fume and β-Al2O3, with Na2O/SiO2, H2O/SiO2 being maintained at 0.2, 4.0, respectively. The geopolymers with each SiO2/Al2O3 ratios are modified by addition of 0, 0.4, 0.8, 1.2 and 1.6 wt% of sodium polyacrylate (PAAS).The mechanical properties of these samples are measured and the rate of change is used to characterize the effect of PAAS on the metakalin-based geopolymers. The mechanism is also shown by 29Si NMR, XPS and FTIR. The results show that the effects of polymer on the mechanical properties of metakaolin-based geopolymer are affected by SiO2/Al2O3 ratio and the effect becomes less obvious with SiO2/Al2O3 ratio increasing from 2.0 to 4.0. Incorporation of PAAS can reduce the degree of polymerization of [SiO]4 or [AlO]4 in geopolymer and form the Si‒O‒C bond, which are two main reasons for polymer improving the toughness of geopolymer. But these effects decrease when the SiO2/Al2O3 ratio of geopolymer increases from 2.0 to 4.0, which is corresponding to the effect on the mechanical properties. The toughening effect of organic polymer on geopolymer depends on the SiO2/Al2O3 ratio of geopolymer, and only the geopolymer with lower SiO2/Al2O3 ratio (no more than 2.5 in this work) can be significantly toughening modified by organic polymer. Therefore, it is necessary to consider the SiO2/Al2O3 ratio of the geopolymer when geopolymer modified by organic polymer is designed.

Geopolymers are an environmentally friendly cementitious materials, which have the advantages of high strength, good durability, and stability; however, geopolymers also have some limitatio...

In order to study the stress of box-girder web under prestressing, and confirming the internal stress distribution of the web, analyzing of vertical prestressed box girder, curved beam prestressed sensitivity under the webs. Establishing finite element model of the box-girder webs vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L/4 section of the web.