Search

Abstract: The β-Mn2V2O7 crystals with strip-like shape were successfully synthesized by molten salt method in different molten salt. The samples were investigated by XRD, SEM, TEM, HRTEM and SAED. The results show molten salt species, molten salt content and heating temperature have great effect on the crystal structure and morphology. The products were found to have a monoclinic structure and possess a uniform strip-like shape with different grain size. The XRD patterns and the SAED patterns of single strip indicate that the β-Mn2V2O7 single strip have single crystalline character. HRTEM image further substantiate that the β-Mn2V2O7 strip have anisotropy growth and crystalline integrality. [ABSTRACT FROM AUTHOR]

The high cost and unfavorable catalytic performance for oxygen reduction reaction (ORR) is one of the crucial obstacles that impede widely commercialization of proton-exchange membrane fuel cells (PEMFCs). Herein, we provide a novel, mass-producible ORR catalyst made of low-loading (10 wt%) Pt nanoparticles bound to patchy nitrogen-doped carbon (PNC) with uniformly dispersed FeN 4 sites (Pt/FeN 4 -PNC). The derived catalyst exhibits significantly improved catalytic activity and stability, obtaining a promising mass activity (MA) of 0.94 A mg pt −1 at 0.9 V (vs. RHE) with a negligible decay after 30,000 cycles accelerated durability test (ADT). In the fuel-cell assessment (under H 2 -Air conditions at 80 ℃), the Pt/FeN 4 -PNC and Pt/FeN 4 -PNC-10 g (scaled-up production) achieved peak power densities of 1.13 W cm−2 and 1.14 W cm−2, respectively, and retained 88.5 % and 88.1 % of the initial values after 30,000 voltage cycles (0.60–0.95 V). The patchy structure of PNC substrate guarantees fast electron routes and resistance to corrosion. With the FeN 4 active sites in the PNC substrate, the oxygen molecules are concurrently reduced on the surfaces of the carbon substrate and Pt nanoparticles, thereby causing the ORR reaction zone on the catalyst layer to expand. [Display omitted] ● The patchy structure of the substrate guarantees fast electron routes and resistance to corrosion. ● The FeN 4 active sites in the PNC substrate significantly enhance the intrinsic ORR activity of the catalyst. ● This effective strategy for the rational design of Pt-integrated catalysts can meet the need of industrialization. [ABSTRACT FROM AUTHOR]

Abstract Copper is widely used in many applications due to its excellent electric conductivity, processing ductility and corrosion resistance. However, poor hardness and low strength are the major limitations of copper in many fields. Herein, we report a high-performance copper matrix composites prepared by powder metallurgy. The copper matrix composites were prepared by mixed acid treatment, molecular-level method, ball milling and spark plasma sintering (SPS) process. The fabrication, microstructure, mechanical properties and electrical conductivity of the composites were investigated. The results show that nano-Al 2 O 3 can act as an active mixing agent to disperse CNTs in copper powders and increase the adhesion between CNTs and copper matrix in composites. Additionally, the uniform dispersion of Al 2 O 3 and CNTs can restrict the grain growth and form a strong bonding interface. Thus, the synthesized Cu-1.5CNTs-0.5Al 2 O 3 composite displays the highest comprehensive performance, such as 131 HV hardness, 345 MPa ultimate tensile strength, 324 MPa yield strength, 13.8% elongation, and 50.6 MS/m (87.2%IACS) electrical conductivity. This work provides a feasible way to prepare high-performance copper matrix composites. Graphical abstract Image 1 Highlights • The Cu-CNTs-Al 2 O 3 composites were fabricated. • The dispersion and interfacial strength of CNTs can be improved by Nano-Al 2 O 3 in composites. • The prepared Cu-1.5CNTs-0.5Al 2 O 3 composite exhibits excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

Abstract: ZnO thin films doped with Al concentrations of 1.0, 2.0, 3.0, 4.0, 5.0at% were prepared by a sol–gel spin-coating method on glass substrates and respectively annealed at 550°C for 2h in hydrogen and air. The X-ray diffraction and selected-area electron diffraction results confirm that the Al doped ZnO thin films are of wurtzite hexagonal ZnO. The scanning electron microscope results indicate that the Al doped ZnO nanorod thin films can be got by annealing in hydrogen rather than in air. The optical properties reveal that the Al doped ZnO thin films have obviously enhanced transmittance in the visible region. The electrical properties show that the resistivity of 1.0at% Al doped ZnO thin films has been remarkably reduced from 0.73Ωm by annealing in air to 3.2×10−5 Ωm by annealing in hydrogen. It is originated that the Al doped ZnO nanorod thin films annealed in hydrogen increased in electron concentration and mobility due to the elimination of adsorbed oxygen species, and multicoordinated hydrogen. [Copyright &y& Elsevier]