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Flexible dielectrics with large dielectric constant (ε′) coupled with low loss are highly pursued in many applications. To bolster the ε′ of raw Zn (zinc)/poly(vinylidene fluoride, PVDF) while maintaining pimping dielectric loss, in this study, the core@double–shell structured Zn@zinc carbonate (ZnCH)@polystyrene (PS) particles are first synthesized through a suspension polymerization of styrene, and then composited with PVDF to elevate the ε′ and keep low loss of the composites. By optimizing the PS shells' thickness and tailoring the electrical resistivity of Zn@ZnCH@PS particles, both the slow inter‐particle polarization and fast intra‐particle polarization in the composites can be decoupled and synergistically tuned, thus, the Zn@ZnCH@PS/PVDF achieves a much higher ε′ and lower dielectric loss, simultaneously, which far exceed the unmodified Zn/PVDF. Both experiment and theoretic calculation reveal that the double‐shell ZnCH@PS not only induces and promotes multiple polarizations enhancing the composites' ε′, especially at the optimized PS's thickness, but also maintains suppressed loss and conductivity thanks to their obvious barrier effect on long‐range charge migration. The core@double–shell filler design strategy facilitates the development of polymer composites with desirable dielectric properties for applications in electronic and electrical power systems. [ABSTRACT FROM AUTHOR]

Polymers with high thermal conductivity (TC) and dielectric constant (ε) but low dielectric loss show enormously potential applications in electrical power systems. To enhance the ε and TC while significantly suppressing the loss of β‐silicon carbide whisker (β‐SiCw)/polyvinylidene fluoride (PVDF), in this study, SiO2 shells with different morphologies were constructed on the superficies of β‐SiCw via a facile oxidation method in air atmosphere. The SiO2 shell' morphology on the TC and dielectric performances of the β‐SiCw@SiO2/PVDF are systematically explored as a function of the frequency and filler loading. The β‐SiCw@SiO2/PVDF demonstrate astonishingly restricted loss and meliorative TC when compared to the β‐SiCw/PVDF because the SiO2 shell not only suppresses the β‐SiCw from direct contact with one another and impedes the long‐distance charges migration thereby resulting in rather low loss and leakage conductivity, but also restrains the thermal interfacial resistance via increased interfacial compatibility and interactions. The concurrent enhancement effect in the ε and TC but low loss of the composites is more evident in the crystalline SiO2 interlayer with a high TC compared with amorphous one. These results provide insight into the exploration of composite nanodielectrics with large TC and ε but low loss for applications in electrical power systems. Highlights: Core@shell structured β‐SiCw@SiO2/PVDF were obtained by a facile oxidation.The great reduction in both loss and conductivity is attributed to the SiO2 shell.Crystalline SiO2 shell can improve the composites' thermal conductivity.The SiO2 shell prevents long‐range carrier migration. [ABSTRACT FROM AUTHOR]

Exploring polymer composites with a high dielectric constant (ε′) and breakdown strength (Eb), low dissipation factor (tanδ), as well as a high thermal conductivity (TC) is of crucially important thanks to their potential applications in modern electronics. Herein, in this paper, two kinds of core–shell-structured Si particles, i.e., Si@SiO2, Si@SiO2@PS, were prepared by high temperature oxidation and polystyrene (PS) coating and incorporated into PVDF (poly(vinylidene fluoride)). The results indicate that both the fillers' kinds and loading have obvious influences on dielectric and thermal properties of the composites. The SiO2 interlayer between the Si and PVDF matrix remarkably suppresses the loss and reduces leakage conductivity, whereas encapsulation of Si@SiO2 with a PS shell further inhibits the loss and conductivity, and the organic PS interlayer enhances the interfacial compatibility and promotes the fillers' homogeneous dispersion in PVDF, therefore improving the Eb of the composites. More importantly, the PVDF composites with 50 wt.% of Si@SiO2@PS show good comprehensive performances: ε′ of 66.6 but tanδ of 0.04 at 100 Hz, Eb of 2.48 kV/mm as well as a high TC of 1.0 W/m K. The prepared Si@SiO2@PS/PVDF composites show promising potential applications in microelectronics and electrical industries. [ABSTRACT FROM AUTHOR]

Developing a high dielectric constant (εr) polymer dielectrics with low dielectric loss and high thermal conductivity (TC) is still continuous demands for advanced electrical power systems. Herein, nickel (Ni) particles were encapsulated by silica (SiO2) via a sol–gel process using sodium silicate as a precursor, and the obtained core–shell Ni@SiO2 powders were blended into poly(vinylidene fluoride) (PVDF) to investigate the effects of SiO2 insulating layer and its thickness on dielectric properties and TC of composites. Compared with pristine Ni, the Ni@SiO2/PVDF composites exhibit a superior εr, and remarkably suppressed loss and conductivity, attributable to the SiO2 interlayer between the core Ni particles which effectively prevents them from direct contacts and significantly reduces the leakage loss. Moreover, the Ni@SiO2/PVDF composites still possess a high TC owing to the restrained thermal interfacial resistance and enhanced interfacial compatibility between the fillers and the matrix. The developed Ni@SiO2/PVDF composites with high k and TC but low loss are potential for microelectronic industry. [ABSTRACT FROM AUTHOR]

To simultaneously improve the impact strength and dielectric properties of cured epoxy (EP), herein we explore liquid rubber toughened EP based on a nonpolar epoxidized hydroxyl‐terminated polybutadiene (EHTPB), where the rubber is covalently bonded to the EP. Fourier transform infrared and nuclear magnetic resonance proved the chemical reaction between EHTPB and EP, which makes the immiscible EHTPB‐EP blend change to compatible one. The results indicate that both the impact strength and dielectric properties can be visibly enhanced with the addition of EHTPB and the maximum values are obtained at 10 phr of EHTPB loading. The improved mechanical toughness can be ascribed to the extensive shear yielding induced by the uniformly dispersed EHTPB domains and the enhanced interfacial compatibility between the two components. Moreover, the enhanced electrical resistivity and dielectric breakdown strength as well as the reduced dielectric constant and loss for the EHTPB‐EP can be attributed to the combination of the excellent insulating properties of HTPB and dielectrically favorable interfaces. Therefore, the EHTPB‐EP with a concurrent improvement in impact strength and dielectric properties can be used as promising insulating materials for high‐frequency microelectronics and high‐voltage electrical equipment. [ABSTRACT FROM AUTHOR]

To suppress the high dielectric loss of graphene oxide (GO)/poly(vinylidene fluoride) (PVDF) while maintaining high dielectric constant (high- k) near the percolation threshold, in this study, GO nanosheets coated with polydopamine (PDA) were integrated into PVDF to investigate the effects of the PDA shell and its concentrations on the dielectric properties of the nanocomposites. The results indicate that the dissipation factor and conductivity of the GO@PDA/PVDF are significantly suppressed to very low values compared with the pristine GO/PVDF composites, attributable to the PDA interlayer between the GO nanosheets which prevents them from direct contact with each other and remarkably reduces the leakage loss. Furthermore, activation energies of the GO/PVDF and GO@PDA/PVDF composites were calculated as 1.247 and 0.884 eV, respectively, indicating that the presence of PDA interlayer reduces the relaxation activation energy and makes the relaxation occur at low temperature for the GO@PDA/PVDF. The prepared GO@PDA/PVDF nanocomposites with high- k but low loss have potential applications in microelectronic engineering. [ABSTRACT FROM AUTHOR]

To suppress dielectric loss while still harvesting high dielectric constant (k) and thermal conductivity in polymer composites, core–shell structured fillers are synthesized via controlled calcination under air, where the conductive copper (Cu) particles are encapsulated by a thin insulating oxidation layer (CuO). The dielectric constant can be substantially improved in the poly(vinylidene fluoride) PVDF composites filled with Cu@CuO fillers, and the dielectric loss is strongly restrained even at high filler loadings. The improved dielectric performance can be ascribed to the insulating CuO shell, which promotes the multiple interfacial polarization and meanwhile impedes the long-range electron migration. Additionally, the Cu@CuO/PVDF composites exhibit higher thermal conductivity (TC) than the unfilled polymer and the Cu/PVDF, owing to the reduced interfacial thermal resistance between the fillers and the matrix. Composites with high TC and k but low loss are promising materials for potential applications in microelectronic, electrical and energy storage devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Surface modification of core‐shell structured Al (Al@Al2O3) nanoparticles was performed using γ‐(Aminopropyl)‐triethoxysilane (APS) and dopamine (DA), respectively, and the microstructures, dielectric properties and thermal conductivities of the Al/poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. Both DA and APS enhance the interfacial bonding strength between the fillers and the matrix, leading to homogeneous dispersion of Al nanoparticles in PVDF matrix. Compared with raw Al nanoparticles, surface‐treated Al/PVDF exhibit much higher dielectric permittivity due to the enhanced interfacial interactions between the two components, whereas, the dielectric loss and electric conductivity of the nanocomposites still remain at rather low levels owing to the insulating alumina shell preventing effectively core Al from direct contact. The dynamic dielectric properties results reveal that dielectric constant and loss increase with temperature due to the gradually enhanced mobility of molecular chain segments of PVDF for the raw Al/PVDF and treated Al/PVDF nanocomposites. Additionally, the PVDF nanocomposites with Al treated with APS and DA show enhanced thermal conductivities compared with raw Al/PVDF under the same filler loading because of reduced thermal interfacial resistance promoting phonon transfer across the interfaces. POLYM. ENG. SCI., 59:103–111, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The broadband dielectric spectroscopy was carried out in the frequency range of 1–107 Hz at the −20–200°C range to investigate the effect of temperature on the dynamic thermal–dielectric behavior of the aluminum (Al)/epoxy composite. The epoxy composites with core-shell–structured Al particles were prepared by solution method. The results show that the dielectric permittivity of the composites increased smoothly with a rise of filler content and reduced with an increase in frequency at room temperature. While the dielectric loss and conductivity still remained at low level owing to the nanoscale alumina insulating shell serving as a barrier layer to control the dielectric loss. The dielectric permittivity, dissipation factor, and conductivity of the composites increased with temperature and exhibited an abrupt rise around the glass transition temperature (Tg). A large increase in the dissipation factor and conductivity with temperature is attributed to the direct current conduction of thermal-activated charge carriers resulting from pure epoxy above Tg. The observed temperature-dependent dielectric relaxations of the composites indicated a thermally activated behavior of the relaxation time of epoxy chain segments. [ABSTRACT FROM AUTHOR]

The urgent requirement for high reliability and increasingly miniaturized electronic devices necessitates packaging polymers with giant dielectric constant (ε′), low loss and high breakdown strength (E b). To significantly restrain the dielectric loss and leakage current of molybdenum (Mo)/poly (vinylidene fluoride, PVDF) while still holding a large ε′ , the silica (SiO 2) encapsulated Mo core@shell structured particles were prepared in this work utilizing a sol-gel method, and then composited with PVDF to explore the silica shell's impact and regulating effect on the dielectric properties of the PVDF composites. The findings on the relationship between microstructure and dielectric properties showcase that the introduced SiO 2 interlayer not only enhances the interface interactions but also mitigates the great interfacial mismatch in both ε′ and conductivity between the two components, resulting in elevated E b of the composites. Moreover, the dielectric loss and conductivity of the composites can be remarkably reduced because the silica shell introduces deep traps inhibiting the passage of long-distance electron migration. And the overall dielectric properties of the Mo@SiO 2 /PVDF can be effectively tuned by modifying the Mo@SiO 2 's electric resistivity and optimizing the shell thickness. This work provides a beneficial strategy for the design and preparation of dielectric composites with superior dielectric performances for prospective applications. • The Mo@SiO 2 /PVDF exhibits superior overall dielectric properties than pure Mo/PVDF. • The SiO 2 layer mitigates the mismatch in ε′ and conductivity between filler and matrix, elevating E b of the composites. • The SiO 2 shell introduces deep traps, inhibits electron migration resulting in very low dielectric loss. • The dielectric properties of the Mo@SiO 2 /PVDF can be modulated via adjusting the silica thickness. [ABSTRACT FROM AUTHOR]

Polymer dielectrics with a high dielectric constant (high ε), low dielectric loss and high thermal conductivity (k) are constantly pursued for advanced electrical power systems, driven by the continuous demands of device miniaturization and high operating temperature. In this paper, we present an effective approach to concurrently improve the dielectric properties and thermal conductivity of composites by tailoring filler interface. Core@double-shell structured aluminum particles are synthesized, with the metallic aluminum core encapsulated by a double-shell of amorphous and crystalline aluminum oxide. The double-shell filler structure enables a substantial increase in dielectric constant and reduction in dielectric loss for the corresponding composites, surpassing the performance of the unfilled polymer and the polymer composites containing the single-shell fillers. The improved dielectric properties can be attributed to the enhanced interfacial polarization. Furthermore, the thermal conductivity of the composites is also significantly improved when the low- k amorphous aluminum oxide shell is transformed into its crystalline phase with high thermal conductivity. [ABSTRACT FROM AUTHOR]