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Abstract: Quasi-static tests were performed on carbon reinforced composite tubes to examine their axial crushing response. Stable progressive crushing processes with brittle fracturing crushing modes were observed during experiments. Numerical investigations were also conducted. Details on the numerical modelling strategy were given and discussed. It is found that triggers introduced in the numerical simulation can effectively model the bevel trigger at the end of the tubular specimens and result in stable progressive crushing. It is also found that the two-layer finite element model based on the Chang–Chang failure criteria is effective in representing the energy absorption characteristics and crushing failure mode of the tubular composite specimens. [Copyright &y& Elsevier]

Abstract: The paper investigates the elastoplastic buckling behavior of thin rectangular plates under biaxial loadings by using the differential quadrature (DQ) method for the first time. Both flow and deformation plasticity theories are adopted and iteration processes are involved due to the material non-linearity. The methodology and procedures are worked out in detail. The buckling behavior of thin rectangular plates with various combinations of boundary conditions and under various loadings is studied. It is found that the DQ results are compared well with existing analytical solutions for plates with two boundaries simply supported and the others either simply supported or clamped. Buckling loads for plates with other combinations of boundary conditions, no analytical solutions are available in such cases, are also presented. The existence of an optimal loading path for the deformation theory model, firstly reported by Durban and Zuckerman, is also observed in such cases. The possible reason is given to explain the large discrepancy in predictions for thicker plates by the flow theory and deformation plasticity theory. [Copyright &y& Elsevier]

It is key to develop novel economical and effective non-noble metal bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting cells. Herein, a series of novel two-dimensional (2D) ultrathin donor-acceptor Co-based metal organic framework nanoplates (U-DA-CoMOF-NPs) as bifunctional HER/OER catalysts have been designed and fabricated based on a donor-acceptor strategy. Density functional theory calculations demonstrate that the fabricated U-DA-CoMOF-NPs are fine donor-acceptor pairs having HOMO-LUMO localizations and a HOMO-LUMO gap of 2.60 eV and give the Gibbs free energy for a reasonable OER mechanism. Additionally, changes in anions can affect the physicochemical characterizations and HER/OER performance of the fabricated U-DA-CoMOF-NPs. As a result, the fabricated U-DA-CoMOF-NPs-1 using NO 3 − as an anion exhibits the optimal HER/OER performance in alkaline solution thanks to the thinnest nanoplate thickness, the largest surface area and hierarchical mesoporous structure. Moreover, a self-assembled overall water splitting cell with U-DA-CoMOF-NPs-1/NF as both cathode and anode achieves a low potential of 1.65 V and a high cycling stability at 10 mA cm−2 for at least 15 h. The present study offers an option to design and fabricate other cost-effective donor-acceptor MOF-based catalysts for water splitting cells. • A series of U-DA-CoMOF-NPs have been fabricated with a donor-acceptor strategy. • The HOMO positioning is on Tdc, LUMO localization is at Tpt and a gap is 2.6 eV. • Co–N has more positive catalytic ability for OER than pyridinic-N and thiophene-S. • The representative U-DA-CoMOF-NPs-1 exhibits the optimal HER/OER performance. • A U-DA-CoMOF-NPs-1/NF cell shows a low potential and high stability at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The first cross-dehydrogenative coupling of secondary benzylic ethers. • Isochroman-based tertiary ether synthesis in high efficiency. • Coupling of α-substituted isochromans with indoles and pyrroles. • The first example of catalytic asymmetric cross-dehydrogenative coupling leading to quaternary center. Abstract Current studies on cross-dehydrogenative coupling of benzylic ethers for new C–C bond construction predominantly focus on primary ether moieties. Oxidative cross-coupling of secondary benzylic ethers remains elusive. Herein, we describe the first cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles for tertiary ether construction. A broad range of α-aryl substituted isochromans react with a variety of electronically varied indoles and pyrroles smoothly under mild metal-free conditions in high efficiency. In addition, the catalytic asymmetric variant was preliminarily explored, and corresponding tertiary ether was obtained in 69% ee. [ABSTRACT FROM AUTHOR]

The exploration of economical and effective non-noble metal catalysts is essential for oxygen reduction reaction (ORR) in energy devices. Recently, heteroatom-doped metal-organic frameworks (MOFs) have shown great potential in ORR due to their high efficiencies and low costs. Herein, three-dimensional (3D) urchin-like N/S co-doped Mn-based MOFs (U–N/S–Mn-MOFs) as an effective ORR catalyst have been successfully prepared by a facile one-step solvothermal methodology. The unique 3D urchin-like structure with a spherical interior and dendritic exterior may provide more catalytic sites and transport channels for ORR. Simultaneously, the doped N and S combined with Mn can promote oxygen adsorption and reduce the reaction energy barrier. These characteristics endow U–N/S–Mn-MOFs with high ORR performance. The present work provides a new opportunity for multiple heteroatom-doped MOFs to achieve high electrocatalytic performance. • U–N/S–Mn-MOFs have been prepared by a facile one-pot solvothermal methodology. • The impact factors of the prepared MOFs are investigated in detail. • U–N/S–Mn-MOFs exhibit high ORR performance in alkaline medium. • The unique 3D urchin-like structure and N/S codoping ensure high ORR performance. [ABSTRACT FROM AUTHOR]

Design and development of cost-efficient multifunctional three-dimensional (3D) metal organic frameworks (MOFs) towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are very significant for green energy devices. Herein, a scalable one-pot solvothermal method is developed to obtain a series of multifunctional 3D flower-like MOFs. In addition, systematic studies are also conducted on the effects of various metal cations and N-containing ligands on the structures, compositions, and multifunctional performance of the obtained MOFs. As a result, 3D flower-like Co-MOFs using Co2+ as a metal cation and 2,2':6′,2″-terpyridine as a N-containing ligand exhibit the highest multifunctional performance towards ORR, OER and HER. The scalable method provides a new prospect to design and develop other MOFs-based multifunctional catalysts. • F–Co-MOFs have been developed via a scalable one-pot solvothermal method. • The effect factors of the obtained MOFs are studied in detail. • F–Co-MOFs display high ORR, OER and HER performance in alkaline medium. • The 3D flower-like structure and MOFs ensure high multifunctional performance. [ABSTRACT FROM AUTHOR]

Abstract: Nelumbo nucifera (Nn.) fiber is the isolated secondary wall of the Nn. leafstalk Tracheary elements which has a unique shape. As the shape of the fiber may strongly affect the industrial uses especially for textile usage, the morphology and structure of Nn. fiber at different growth stages were investigated by several techniques in the present work. The Nn. fiber has spriral morphology with cellulose I structure. The diameter of mature fiber is about 4μm and the cross-section shows elliptical or slightly oval shape without lumen. These findings aim to deeply understand the structure of Nn. fiber which is expected to be helpful to bring Nn. fiber into industrial use. [Copyright &y& Elsevier]

Abstract: Lotus fiber is a natural cellulose fiber isolated from lotus petiole. Botanically, the fiber is the thickened secondary wall in xylem tracheary elements. In order to obtain essential information for the preparation and processing of lotus fibers, the fine structure and properties of lotus fibers were investigated by the aid of transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), X-ray diffraction (XRD), and so on. The results show that lotus fibers display a rough surface topography and an internal structure different from common plant fibers. The percent crystallinity and preferred orientation of crystallites in lotus fibers are 48% and 84%, respectively. Considering the average breaking tenacity and Young''s modulus, lotus fibers are similar to cotton. The elongation of lotus fibers is only about 2.6% while their moisture regain is as high as 12.3%. [Copyright &y& Elsevier]