Hollow hydrangea-like nitrogen-doped NiO/Ni/carbon composites as lightweight and highly efficient electromagnetic wave absorbers

Hierarchical hollow-structured magnetic–dielectric materials are considered to be promising and competitive functional absorbers for microwave absorption(MA).Herein,a hierarchical hollow hydrangea multicomponent metal oxides/metal-carbon was designed and successfully produced via a facile self-assembly method and calcination process.Adequate magnetic NiO and Ni nanoparticles were suspended within the hollow hydrangea-like nitrogen-doped carbon matrix(HH N-NiO/Ni/C),constructing a unique hierarchical hollow structured multicomponent magnetic–dielectric MA composite.The annealing temperature and oxidation time were carefully regulated to investigate the complex permittivity and permeability.HH N-NiO/Ni/C delivers exceptional MA properties with maximum reflection loss of–45.8 dB at 1.7 mm thickness and displays a wide effective absorption frequency range of 5.6 GHz.The superior MA performance can be attributed to the following aspects:(1)The hierarchical hollow multicomponent structure offers plentiful of heterojunction interfaces triggering interfacial polarization;(2)nitrogen doped-carbon(N-C)facilitates the conductive loss by the unique electron migration path in the graphitized C and NiO/Ni;(3)magnetic NiO/Ni nanoparticles homogeneously dispersed within N-C form extensive C skeleton and strengthen the magnetic response ability;(4)hierarchical hollow wrinkled structures possess a large interspace and heterogeneous interface improving polarization loss and enhancing multireflection process and the unique structure satisfies magnetic and dielectric loss simultaneously resulting from synergistic effects of different components within the composites.

Geochemistry of the Mesoproterozoic Intrusions, Geochronology and Isotopic Constraints on the Xiaonanshan Cu-Ni Deposit along the Northern Margin of the North China Craton

Mesoproterozoic magma events in the Bayan Obo rift belt have remained poorly constrained and as a result, the Late Paleoproterozoic–Mesoproterozoic tectonic evolution of the rift belt has remained unclear. By a multiple-facetted regional geological investigation of this belt, we have resolved the stratigraphic sequence and geochronology of the Bayan Obo Group and made new discoveries including a three-stage mantle-derived magmatic sequence. Zircon and baddeleyite dating of Xiaonanshan hornblende pyroxenite emplaced into the Bayan Obo Group yields 207Pb/206Pb ages of ca. 1.34 and 1.33 Ga. The geochronological, geochemistry, Hf isotopic analyses place an important constraint on ages of the Late Paleoproterozoic–Mesoproterozoic strata and the evolution of the rift belt. Our field observations and U-Pb dating results suggest that mineralization is genetically related to Mesoproterozoic magmatism in North China Craton, i.e., 1.33–1.34 Ga. The δ34SV-CDT values of sulphide from the ore-bearing ultra-/mafic samples are about 6.2‰, whereas the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values vary in the ranges of 17.598–18.115, 15.496–15.501, and 37.478–37.952, respectively. The Late Paleozoic mafic gabbro and acidic granite porphyry intrusions are possible to bimodal magmatic event related to the extensional tectonic setting of the Central Asia in this period.

合理设计多电子转移机制实现更好的水系锌-有机电池

由于环境相容性好、分子结构可定制和有机物资源丰富等优势,水系锌-有机物电池(AZOBs)成为构建新一代大规模储能系统的关键技术.然而,电导率差、有机物溶解和单一活性基团等问题严重限制了有机物正极材料的倍率性能、稳定性和比容量.因此,具备多氧化还原中心和稳定骨架的有机物正极材料对于实现高性能有机物正极材料至关重要.这些多官能团有机物可协同作用并激发基于多电子转移的氧化还原反应,进而促进H^(+)/Zn^(2+)共嵌以显著提升电池性能.本文探索了多官能团有机物电极的分子结构与其氧化还原反应机理之间的构效关系.本文综述了多官能团有机正极材料在提高氧化还原电位、比容量、动力学以及稳定性等方面面临的挑战和解决策略,为进一步开发先进AZOBs的关键正极材料提供了重要基础.