RESUMEN
Dielectric capacitors are critical components in electronics and energy storage devices. The polymer-based dielectric capacitors have the advantages of device flexibility, fast charge-discharge rates, low loss, and graceful failure. Elevating the use of polymeric dielectric capacitors for advanced energy applications such as electric vehicles (EVs), however, requires significant enhancement of their energy densities. Here, we report a polymer thin film heterostructure-based capacitor of poly(vinylidene fluoride)/poly(methyl methacrylate) with stratified 2D nanofillers (Mica or h-BN nanosheets) (PVDF/PMMA-2D fillers/PVDF), that shows enhanced permittivity, high dielectric strength, and an ultrahigh energy density of ≈75 J/cm3 with efficiency over 79%. Density functional theory calculations verify the observed permittivity enhancement. This approach of using oriented 2D nanofillers-based polymer heterostructure composites is expected to be versatile for designing high energy density thin film polymeric dielectric capacitors for myriads of applications.
RESUMEN
Colloidal assembly of nC60 fullerene with naturally abundant magnetic iron oxide NPs will affect their fate and transformation in environmental media. In solution, fullerene association to aggregating iron oxide NPs/clusters greatly enhanced the overall colloidal stability. Development of depletion-mediated structured fullerene layers between pure and surface modified γFe2O3 NPs possibly resulted in such stabilization. Here, we also report that on air-water interface, association of fullerene to pure and humic acid (HA7) coated γFe2O3 NPs led to the formation of ordered assemblies, e.g., binary wires and closed-packed "crystalline" and "glassy" structures in the presence and absence of electrolytes suggesting immobilization of the former. The interaction of fullerene to Fe3O4 NPs and clusters also produced ordered assemblies along with amorphous aggregates. Fullerene interaction with Fe3O4 NPs in low concentration of HA1 and Na(+) at pH 6 formed dendritic growth and polycrystalline circular assemblies on air-water interface. HRTEM study further revealed that the monolayer circular assemblies were highly ordered but structural degeneracy was evident in multilayers. Therefore, interfacial assemblies of fullerene with iron oxide NPs resulted in short-range periodic structures with concomitant immobilization and reduction in availability of the former, especially in soils or sediments rich in the latter.
