Self-assembling nacre-like high-strength and extremely tough polymer composites with new toughening mechanism

Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of these properties.Here,a self-assembling nacre-like polymer composite is designed to achieve ex-tremely tough with increasing strength.This special design significantly improved polymer’s mechanical properties,including an ultra-high fracture strain of 1180%,a tensile strength of 55.4 MPa and a toughness of 506.9 MJ/m^(3),which far exceed the highest values previously reported for polymer composites.This ex-cellent combination of properties can be attributed to a novel toughening mechanism,achieved by the synergy of the domain-limiting effect of metallic glass fragments with the strain-gradient-induced orien-tation and crystallisation within the polymer during stretching.Our approach opens a promising avenue for designing robust polymer materials in armour and aerospace engineering for a range of innovative applications.

Experimental demonstration of transverse mode instability enhancement by a counter-pumped scheme in a 2 kW all-fiberized laser

Transverse mode instability(TMI)has become the major limitation for power scaling of fiber lasers with nearly diffraction-limited beam quality.Compared with a co-pumped fiber laser,a counter-pumped fiber laser reveals TMI threshold enhancement through a semi-analytical model calculation.We demonstrated a 2 kW high-power counter-pumped all-fiberized laser without observation of TMI.Compared with the co-pumped scheme,the TMI threshold is enhanced at least 50%in counter-pumped scheme,moreover,stimulated Raman scattering and four-wave mixing are suppressed simultaneously.

Self-templated formation of twin-like metal-organic framework nanobricks as pre-catalysts for efficient water oxidation

Fabrication of single-crystalline metal-organic framework(MOF)hollow nanostructures with two-dimensional(2D)morphologies is a challenging task.Herein,twin-like MOF nanobricks,a quasi-hollow 2D architecture,with multi-metal nodes and replaceable organic ligands,are uniformly and firmly grown on conductive Ni foam through a generic one-pot approach.The formation process of twin-like MOF nanobricks mainly includes selective epitaxial growth of Fe-rich MOF layer and simultaneously dissolution of the pre-formed Ni-rich metal-organic frameworks(MOFs),all of which can be ascribed to a special self-templated mechanism.The fantastic structural merits of twin-like MOF nanobrick arrays,featuring highly exposed active sites,remarkable electrical conductivity,and hierarchical porosities,enable this material for efficient electrocatalysis.Using bimetallic NiFe-MOFs grown on Ni foam as an example,the resultant twin-like nanobrick arrays can be directly utilized as three-dimensional(3D)integrated electrode for high-performance water oxidation in 1 M KOH with a low overpotential,fast reaction kinetics(28.5 mV·dec^(-1)),and superb stability.Interestingly,the unstable NiFe-MOFs were served as an oxygen evolution reaction(OER)pre-catalyst and the single-crystalline NiFe-MOF precursor can be in-situ topochemically regulated into porous and lowcrystalline NiFeOx nanosheets during the OER process.This work extends the hollowing strategy to fabricate hollow MOFs with 2D architectures and highlights their direct utilization for advanced electrocatalysis.

高功率连续绿光激光器的研究进展

近年来,高功率绿光激光器的快速发展引起了国内外学者的广泛关注,已经逐步应用于工业加工、3C电子行业、医疗、军事国防等领域.本文首先对高功率绿光激光相比于近红外激光的优势和主要的应用场景进行介绍,然后对二极管泵浦全固态、半导体、碟片和窄线宽光纤倍频四种类型的高功率连续绿光激光器的国内外发展现状进行总结.其中,光纤激光器具有电光效率高、体积小、光束质量好、成本较低和散热好等特点,并且单通倍频的方案具有结构简单、易于调节安装等优势.将高功率窄线宽光纤激光器和单通倍频方案结合,是实现高功率高亮度小型化绿光激光输出的理想技术方案.然后,主要分析了当前高功率窄线宽绿光光纤激光器的关键技术、发展趋势和面临的主要挑战.最后,介绍了该类型激光器在焊接工艺中的应用,并对未来的发展进行了展望.

Morphology and strain control of hierarchical cobalt oxide nanowire electrocatalysts via solvent effect

Designing highly efficient and low-cost electrocatalysts for oxygen evolution reaction is important for many renewable energy applications.In particular,strain engineering has been demonstrated as a powerful strategy to enhance the electrochemical performance of catalysts;however,the required complex catalyst preparation process restricts the implementation of strain engineering.Herein,we report a simple self-template method to prepare hierarchical porous Co_(3)O_(4)nanowires(PNWs)with tunable compressive strain via thermal-oxidation-transformation of easily prepared oxalic acid-cobalt nitrate(Co(NO_(3))_(2))composite nanowires.Based on the complementary theoretical and experimental studies,the selection of proper solvents in the catalyst preparation is not only vital for the hierarchical structural evolution of Co_(3)O_(4) but also for regulating their compressive surface strain.Because of the rich surface active sites and optimized electronic Co d band centers,the PNWs exhibit the excellent activity and stability for oxygen evolution reaction,delivering a low overpotential of 319 mV at 10 mA·cm^(−2)in 1 M KOH with a mass loading 0.553 mg·cm^(−2),which is even better than the noble metal catalyst of RuO_(2).This work provides a cost-effective example of porous Co_(3)O_(4)nanowire preparation as well as a promising method for modification of surface strain for the enhanced electrochemical performance.