To suppress the high loss of nickel (Ni)/poly(vinylidene fluoride) (PVDF) while remaining high dielectric constant (k) near the percolation threshold. In this study, core-shell structured Ni (Ni@NiO) particles were prepared by heat treatment of raw Ni powder under air atmosphere and incorporated into PVDF to prepare Ni@NiO/PVDF dielectric composites. The morphological, dielectric properties and thermal conductivity of the composites are characterized. The results indicate that compared with the raw Ni reinforced PVDF composites, the Ni@NiO particles endow PVDF with a high-k and rather low dissipation factor owing to the presence of NiO shell between Ni core and PVDF which serves as an interlayer between the Ni cores preventing them from contacting with each other. Additionally, the Ni@NiO/PVDF composites still possess a high thermal conductivity. Therefore, the as-prepared Ni@NiO/PVDF composites possess high-k but low loss, high thermal conductivity, making them promising for the industrial application as embedded capacitors.
By using density functional theory (DFT) and ab initio molecular dynamics, we investigate the dehydrogenation reactivity of 13 atoms platinum cluster supported on the alumina (100) surface. We provide a detailed free energy profile and structural analysis of the dehydrogenation mechanisms of methyl-cyclohexane (MCH) into toluene. We highlight the quantitative impact of dispersion corrections on the free energy profile and on the adsorption configurations of the intermediates exhibiting a dual interaction with the cluster and with the alumina surface. During the step by step dehydrogenation of MCH, several reconstructions of the Pt cluster and hydrogen migrations occur. Due to the cluster ductility, they are moderately activated and provide optimal active sites catalyzing the C-H bond cleavages. According to a preliminary kinetic analysis based either on energetic spans or on activation free energies of elementary steps, we found that many states and/or steps may be considered as determining ones. This may explain some diverging interpretations brought by previous experimental kinetic studies. We finally discuss how the cluster ductility challenges the historical concept of structure sensitivity/insensitivity for a given reaction in the case of nanometer-size metallic clusters dispersed on a support.
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