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Abstract: We experimentally and theoretically demonstrated a flat superlens by negative refraction imaging for acoustic waves in a two-dimensional phononic crystal. The sample consists of a square array of steel cylinders immersed in water. The dispersion surfaces at the first band for this sample are nearly circular around point M in the first Brillouin zone, which makes the index of the negative refraction for the phononic crystal sample be well defined for all angles of incidence. Both the observed negative refraction behavior and imaging effect are in excellent agreement with numerical simulations by the Multiple Scattering Theory method. [Copyright &y& Elsevier]

• Novel C 60 /EUR films were fabricated for controlling wheat scab fungus. • Structure and properties of C 60 /EUR films were extensively investigated. • C 60 /EUR films showed the excellent UV-blocking performance and stretchability. • 2 % C 60 /EUR film exhibited good inhibition of Fusarium graminearumt for 10 days. It is significant to develop biodegradable and functional claddings instead of plastic covers providing an environmental-friendly solution for wheat scab fungus control in agriculture. Herein, the nanocomposite films were prepared by adding different amounts of fullerene C 60 into the Eucommia ulmoides rubber (EUR) matrix under ultrasonic-assisted treatment. These nanocomposite films were characterized by using AFM, Raman, XPS, UV and XRD, and their thermal stability, mechanical properties, WVP, EM wave absorption, and inhibition effect on Fusarium graminearum in vitro as well as in wheat seeds were also investigated in detail. The results showed the incorporation of C 60 effectively enhanced the crystallinity, melting and mechanical properties. More importantly, C 60 could endow the nanocomposite films excellent UV-blocking performance, 100 % of the UV spectrum was shielded. Interestingly, it was found photoselective inhibition of F. graminearum by UV-blocking using C 60 /EUR nanocmoposite films. Especially, 2 % C 60 /EUR nanocomposite film displayed excellent incidence rate control for 10 days. [ABSTRACT FROM AUTHOR]

A purely physically crosslinked double network (DN) hydrogel, poly(sulfobetaine- co -acrylic acid)/chitosan-citrate (P(SBMA-co-AAc)/CS-Cit) DN hydrogel, was prepared based on electrostatic interaction and hydrogen bonding between the polymer chains. The hydrogel is highly stretchable, transparent, anti-fatigue, self-adhesive and has good self-healing properties with a self-healing efficiency as high as 95.4%. Furthermore, the resistance of the P(SBMA-co-AAc)/CS-Cit DN hydrogel is sensitive to a wide strain window and the relative resistance shows stable and reliable change during deformation. Herein, the hydrogel was demonstrated as a strain sensor to detect human motions, such as joint bending and swallowing. More excitingly, before ionic crosslinking, the P(SBMA-co-AAc)/CS-Cit composite hydrogel is injectable, thus the P(SBMA-co-AAc)/CS-Cit DN hydrogel sensor can be made into various complex shapes by injecting the P(SBMA-co-AAc)/CS-Cit composite hydrogel into citrate solution, including multilayer structures, exhibiting a great potential for applications as 3D printing strain sensors. Unlabelled Image • A purely physically crosslinked P(SBMA-co-AAc)/CS-Cit DN hydrogel was successfully prepared. • The hydrogel is highly stretchable, transparent, anti-fatigue, self-adhesive and has good self-healing properties. • The hydrogel is sensitive to a wide strain window and the relative resistance shows stable and reliable change. • The hydrogel is injectable, exhibiting a great potential for applications as 3D printing strain sensors. [ABSTRACT FROM AUTHOR]

• High-performance PCM-N was prepared by a new method. • PCM-N has well-developed pore structure and large specific surface area. • PCM-N has a high effect on Cr (VI) removal. • PCM-N has good regenerative abilities. Nitrogen-doped carbon spheres (CSs-N) were synthesized by a hydrothermal method with glucose as the carbon source and urea as the nitrogen source. The synthesized nitrogen-doped carbon spheres were activated by KOH to prepare high performance nitrogen-doped porous carbon material (PCM-N) for adsorption of Cr(VI). SEM, TEM, BET, Raman spectroscopy, XRD, XPS, Zeta potential and elemental analysis techniques were used to characterize the materials, and the properties of the materials were tested by a batch adsorption method. The results show that the specific surface area of PCM-N is 1600.67 m2/g, and the maximum adsorption capacity of Cr(VI) is 402.9 mg/g, and the performance was better than that of a similar materials (Longan seed and Fox nutshell and so on). Furthermore, the adsorption capacity will increase with increasing temperature. In this study, the kinetics and isotherm model of adsorption parameters are fitted, and it is found that the adsorption process is in accordance with the Pseudo-second-order kinetic model and Freundlich model, thermodynamic parameters show that the adsorption of Cr(VI) onto the PCM-N was spontaneous endothermic process. The regeneration adsorption experiment showed that PCM-N has good reusability and high application value. [ABSTRACT FROM AUTHOR]

• The synergistic influences of US and PS are reviewed. • Operational factors influencing the removal efficiency are discussed and summarized. • Reaction mechanisms of sono-activated persulfate oxidation are evaluated and outlined. • Knowledge gaps and research needs of sono-activated persulfate are proposed. Persulfate (PS) has attracted great attention as an alternative to H 2 O 2 for advanced oxidation processes in recent years. Among various activation techniques, ultrasound (US) activation acts as an emerging method and has gained increasing interest especially in recent years. The combination of US and PS is a promising alternative for organic wastewater treatment. In this review, the synergistic effects of US and PS were investigated based on wide applications. The degradation efficiency is easily influenced by the reaction factors, including ultrasonic power and frequency, pH, temperature, PS concentration, and coexisting inorganic anions etc. These factors were summarized and analyzed to give the optimal references for further in-depth studies. Moreover, the decomposing mechanisms are outlined in terms of molecular structures due to the one-sidedness of reactive radical analysis. In the end, the concluding remarks and perspectives are made for future study on US-PS technologies. This review can provide an overview for the systematic understanding of the mechanisms and synergistic effects of US and PS combination. [ABSTRACT FROM AUTHOR]

In this work, friction stir welding (FSW) was used to weld dissimilar metals (Type 304 stainless steel (SS304) and Q235 low carbon steel). The microstructure, interfacial characteristics, residual stress distribution and mechanical properties of the joint were investigated. The results show that FSW results in grain refinement in the stir zone (SZ) and thermal-mechanical affected zone (TMAZ) in SS304 side. Discontinuous dynamic recrystallization and twinning-induced dynamic recrystallization are the main grain refinement mechanisms. Dynamic recovery occurs in the heat-affected zone (HAZ). On the Q235 steel side, the acicular ferrite and pearlite are generated in the SZ, which is due to its peak temperature of up to Ac 3. Additionally, the amount of acicular ferrite decreases in the TMAZ. Continuous and discontinuous dynamic recrystallization is the main recrystallization mechanism in the two regions. The interfacial bonding mechanism of FSW joint consists of both mechanical and metallurgical bonding. In addition, the difference in expansion coefficient and microstructure between the two steels results in the formation of residual compressive stress in the SZ. Grain refinement and acicular ferrite are responsible for the microhardness distribution in the whole joint. The tensile strength of FSW joint is 493 MPa, which is more than that of Q235 steel by around 4%. However, the elongation is 17%, which shows a decrease of around 50%. Furthermore, the fracture surface shows ductile fracture with dimples. • Recrystallization mechanism of dissimilar FSWed SS304 and Q235 steel was investigated. • Peak temperature of Q235 steel side during FSW was estimated. • Bonding mechanism welding joint is both mechanical and metallurgical bonding. [ABSTRACT FROM AUTHOR]