Amorphous TiO2-coated reduced graphene oxide hybrid nanostructures for polymer composites with low dielectric loss

The Effect of Polyethylene Glycol Addition on Wettability and Optical Properties of GO/TiO2 Thin Film

Modification has been made to TiO₂ thin film to improve the wettability and the absorption of light. The sol-gel spin coating method was successfully used to synthesize GO/TiO₂ thin films using a titanium (IV) isopropoxide (TTIP) as a precursor. Different amounts of polyethylene glycol (PEG) (20 to 100 mg) were added into the parent sol solution to improve the optical properties and wettability of the GO/TiO₂ thin film. The effect of different amounts of PEG was characterized using X-ray diffraction (XRD) for the phase composition, scanning electron microscopy (SEM) for microstructure observation, atomic force microscopy (AFM) for the surface topography, ultraviolet–visible spectrophotometry (UV-VIS) for the optical properties and wettability of the thin films by measuring the water contact angle. The XRD analysis showed the amorphous phase. The SEM and AFM images revealed that the particles were less agglomerated and surface roughness increases from 1.21 × 10² to 2.63 × 10² nm when the amount of PEG increased. The wettability analysis results show that the water contact angle of the thin film decreased to 27.52° with the increase of PEG to 80 mg which indicated that the thin film has hydrophilic properties. The optical properties also improved significantly, where the light absorbance wavelength became wider and the band gap was reduced from 3.31 to 2.82 eV with the presence of PEG.

Ultralight Microcellular Polymer-Graphene Nanoplatelet Foams with Enhanced Dielectric Performance

Dielectric polymer nanocomposites with high dielectric constant (ε') and low dielectric loss (tan δ) are extremely desirable in the electronics industry. Percolative polymer-graphene nanoplatelet (GnP) composites have shown great promise as dielectric materials for high-performance capacitors. Herein, an industrially-viable technique for manufacturing a new class of ultralight polymer composite foams using commercial GnPs with excellent dielectric performance is presented. Using this method, the high-density polyethylene (HDPE)-GnPs composites with a microcellular structure were fabricated by melt-mixing. This was followed by supercritical fluid (SCF) treatment and physical foaming in an extrusion process, which added an extra layer of design flexibility. The SCF treatment effectively in situ exfoliated the GnPs in the polymer matrix. Moreover, the generation of a microcellular structure produced numerous parallel-plate nanocapacitors consisting of GnP pairs as electrodes with insulating polymer as nanodielectrics. This significantly increased the real permittivity and decreased the dielectric loss. The ultralight extruded HDPE-1.08 vol % GnP composite foams, with a 0.15 g·cm^-3 density, had an excellent combination of dielectric properties (ε' = 77.5, tan δ = 0.003 at 1 × 10⁵ Hz), which were superior to their compression-molded counterparts (ε' = 19.9, tan δ = 0.15 and density of = 1.2 g·cm^-3) and to those reported in the literature. This dramatic improvement resulted from in situ GnP's exfoliation and dispersion, as well as a unique GnP parallel-plate arrangement around the cells. Thus, this facile method provides a scalable method to produce ultralight dielectric polymer nanocomposites, with a microscopically tailored microstructure for use in electronic devices.

Mechanical and dielectric properties of epoxy composites filled with hybrid aluminum particles with binary size distribution

Epoxy composites incorporated with three kinds of hybrid aluminum (Al) particles with binary size distribution, that is, [1 μm/45 μm], [1 μm/18 μm], and [18 μm/45 μm], respectively, were prepared, and the mechanical and dielectric properties of the hybrid Al/epoxy composites were investigated as a function of relative weight fraction of smaller-size Al ( Ws) of hybrid Al particles at a total filler content of 50 wt%. The mechanical and electrical properties of the hybrid Al/epoxy composites are found to mainly depend on the type of hybrid filler and the Ws and can be tuned by changing the Ws. The maximum tensile strength and elongation at break of the composites appear at an optimal Ws. Furthermore, the dielectric permittivity, dielectric breakdown strength, and volume resistivity of the hybrid Al/epoxy composites also exhibit the similar variations as the mechanical properties with the Ws. The obvious enhancements in the physical properties can be ascribed to the synergistic effect of hybrid particles in the matrix at the optimal Ws, which endows the composites with better mechanical and dielectric properties. So, the results give a facile strategy to enhance the dielectric and mechanical properties of the composites by choosing a proper Ws at a fixed total filler loading.