In this work, epoxy (EP) resin composites with “point-surface” heterostructures constructed by hybrid fillers of Ni particles and graphene nanosheets (GNPs) are prepared via a blending method under magnetic field. Effects of filler content and magnetic orientation on dielectric, thermally and electrically conductive, and thermomechanical properties of the resultant composites are investigated. The findings disclose that the synergistic effect of hybrid fillers and the magnetic orientation result in the formation of a complex heterogeneous network structure, significantly improving both thermal and electrical conductivities. From the temperature distribution analysis, it is the construction of the heterogeneous network that improves the thermally conductive and thermomechanical properties. Sample Y4 (containing 28 wt% Ni and 2 wt% GNP) displays an average heating rate (AHR) of 152.4 °C min −1 and has an out-of-plane thermal conductivity of 0.930 W m −1 K −1 (267.6% higher than that of neat EP). The infrared thermal imaging (ITI) together with SEM observations further confirms that the Ni chains in situ formed under a magnetic field are responsible for the improved composite's thermal conductivity and thermal management capability, which make it potentially applicable for 3D packaging materials in power-intensive electronic components.
Dissolved organic matter (DOM), which is ubiquitously distributed in groundwater, has a crucial role in the fate and reactivity of iron materials. However, there is a lack of direct evidence on how different DOMs interact with nFe/Ni in promoting or inhibiting the dechlorination efficiency of chlorinated aromatic contaminants. By comparing humic acid (HA), fulvic acid (FA), and biochar-derived dissolved organic matter (BDOM) at different pyrolysis temperatures, we first demonstrated that the dechlorination effect of nFe/Ni on 2,4-dichlorophenol (2,4-DCP) depended on the nature of DOMs and their adsorption on nFe/Ni. HA showed an enhancing effect on the dechlorination of 2,4-DCP by nFe/Ni, while the inhibition effect of other DOMs resulted in the following dechlorination order: BDOM300 ≈FA>BDOM700 ≈BDOM500. The C2 component with higher aromaticity and molecular weight promoted the corrosion of nFe/Ni and the production of reactive hydrogen atoms (H*). The effects of different DOMs on nFe/Ni include that (1) HA accelerates the corrosion and H* production of nFe/Ni, (2) FA and BDOM300 enhance the corrosion but inhibit H* production, and (3) Both nFe/Ni corrosion and H* formation are suppressed by BDOM500/BDOM700. Therefore, this study will provide a reference for understanding the nature of DOM-nFe/Ni interaction and improving the catalytic activity of nFe/Ni when different DOMs coexist in practical applications.
Ze-Min Zhao,Yu Zhang,Yu Chen,Jieying Jing,Wen-Ying Li
Nickel–aluminum (Ni–Al) spinel catalysts with distinct Ni/Al molar ratios were synthesized to construct Ni 2+ coordination sites. Owing to the favorable distribution of Ni 2+ coordination sites and the presence of suitable concentration of Ni 2+ in octahedral sites, Ni/Al-0.725 catalyst achieved an 86.1 % average yield of perhydrophenanthrene, which was higher than that obtained with Ni/Al-0.25 (6.3 %). Characterization results indicated that Ni 2+ of the Ni/Al-0.725 catalyst was present in octahedral sites and ∼ 40.4 % Ni 2+ was reduced to Ni, whereas the active Ni metal of Ni/Al-0.25 catalyst mainly comprised Ni 2+ occupying tetrahedral sites as precursors. Furthermore, the Ni/Al-0.725 catalyst exhibited the smallest Ni particle size (2.82 nm) and the largest Ni available surface (19.62 m 2 /g sample ), which helped alleviate competitive adsorption among aromatic hydrocarbons. The Ni reduced by the spinel catalysts was in an electron-deficient state, which enhanced the adsorption of polycyclic aromatic hydrocarbons.
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