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Here we report a non-toxic β-type titanium alloy exhibiting unstable elastic and plastic deformation behavior. Elastic instability leads to remarkable elastic softening, i.e., the decrease of incipient Young’s modulus with slight pre-straining. In spite of partial recovery during room-temperature aging, a stable modulus of 33GPa matching that of human bone can be maintained. Plastic instability causes highly-localized deformation which is very effective in grain refinement but contributes little to strength. We thus obtain soft nanostructured metallic materials (NMMs): The flow stress increases by only ∼5.5% as coarse grains are reduced to below 50nm, in contrast with several times increase for previously-reported NMMs.

Emerging sodium-ion batteries (SIBs) have aroused great attention in large-scale energy storage. However, it is still a great challenge to develop suitable electrode materials due to the large radius of Na+. This work demonstrates a strategy to synthesize hierarchical tubular MoS2 via a facial hydrothermal method with the assistance of tetramethylammonium bromide (TMAB). The results show that sufficient amounts of TMA+ ions are necessary to form the hierarchical tubular structures of MoS2. The obtained tubular MoS2 displays a high diffusion coefficient of Na+ ions, a high specific capacity of 652.5 mAh/g at the current density of 100 mA/g after 50 cycles, and a good cycling stability (94.2% of the initial capacity can be retained after 100 cycles at 1000 mA/g). In situ XRD during the discharge/charge process displays a reversible intercalation/deintercalation of Na+ into MoS2 layers followed by a conversion-type reaction. Systematic analyses reveal that the enhanced electrochemical performance is attributed to its tubular hierarchical structures with the wall composed of loosely stacked nanosheets, which can provide nearly unobstructed ion transportation paths, sufficient active sites, and enough space to mitigate the effects of the volume change during the discharge/charge process. This synthetic approach can be easily extended to other metal oxides and metal sulfides with hierarchical structures for versatile applications.

A novel composite with imine-linked covalent organic frameworks on graphene was synthesized in one step with the amine functionalized reduced graphene oxide as the support. The excellent electrochemical properties of this composite can be ascribed to the synergistic effect of the introduction of covalent organic frameworks as well-dispersed nanoscale deposits on the conductive graphene surfaces.Driven by environmental problems and the energy crisis, the development of clean and renewable energy storage materials as well as their devices is urgently needed. 1 Among various energy storage devices, rechargeable batteries and electrochemical capacitors (ECs) are regarded typically as a suitable choice to store energy by transforming chemical energy into electrical energy. 2 Electrochemical capacitors, also called supercapacitors, which store energy using either ion adsorption or fast surface redox reactions, are supposed to be promising candidates for alternative electrical energy storage devices due to their high power density, exceptional cycle life, and low maintenance cost. 3 The performance of supercapacitors is highly dependent on the properties of electrode materials. Many materials have been investigated as the electrode materials in supercapacitors, including carbonaceous materials, transition metal oxides and conducting polymers. 4 Each type of electrode material has its pros and cons. The novel electrode materials with terric performance should be developed.Covalent organic frameworks (COFs) are a novel class of crystalline organic materials with well-dened and predictable two-or-three-dimensional pore structures assembled from molecular building blocks. 5 Their crystal structures are entirely held by strong bonds solely from light elements (B, C, N, H, and O) to form rigid porous architectures. These materials have exceptional thermal stabilities, and low densities, and permanent porosity with high specic surface areas. Their extraordinary and versatile properties have offered the COF materials superior potential in diverse applications, such as gas storage, 6 adsorption, 7 optoelectricity, 8 catalysis, 9 and biosensor. 10 As we know, many COFs have an extended p-conjugated system and inherent nanopores, which may hold promise for fundamental advances in supercapacitor electrode materials. 11 While, COFs has been scarcely reported as electrode materials for supercapacitors, which may be due to the limited chemical and oxidative stability of established COFs linkages precludes this applications.Since the rst report of graphene synthesized in 2004, it has emerged as one of the most active research elds. 12 Due to its fascinating properties, graphene is considered as a highly desirable support for many applications. 13 Here, we present a simple method to fabricate the COFs/graphene composite through the reaction of aldehyde group in 1,3,5-triformylbenzene and amine group in NH 2 -graphene and 1,4diaminobenzene in one step on the surface of amino functionalized graphene. The synthesized conjugated cova...