Intrinsically conducting polymers (ICP) and conductive fillers incorporated conductive polymer-based composites (CPC) greatly facilitate the research in electromagnetic interference (EMI) s...

Electromagnetic Interference Shielding Polymers and Nanocomposites - A Review

Comparative study of electromagnetic interference shielding properties of injection molded versus compression molded multi-walled carbon nanotube/polystyrene composites

The interface between filler and matrix has long been a critical problem that affects the thermal conductivity of polymer composites. The effects of the interface on the thermal conductivity of the composite with low filler loading are well documented, whereas the role of the interface in highly filled polymer composites is not clear. Here we report on a systematic study of the effects of interface on the thermal conductivity of highly filled epoxy composites. Six kinds of surface treated and as received AlN particles are used as fillers. Three kinds of treated AlN are functionalized by silanes, i.e., amino, epoxy, and mercapto group terminated silanes. Others are functionalized by three kinds of materials, i.e., polyhedral oligomeric silsesquioxane (POSS), hyperbranched polymer, and graphene oxide (GO). An intensive study was made to clarify how the variation of the modifier would affect the microstructure, density, interfacial adhesion, and thus the final thermal conductivity of the composites. It was f...

Role of interface on the thermal conductivity of highly filled dielectric epoxy/AlN composites

Dielectric polymer composites with high dielectric constants and high thermal conductivity have many potential applications in modern electronic and electrical industry. In this study, three-phase composites comprising poly(vinylidene fluoride) (PVDF), barium titanate (BT) nanoparticles, and β-silicon carbide (β-SiC) whiskers were prepared. The superiority of this method is that, when compared with the two-phase PVDF/BT composites, three-phase composites not only show significantly increased dielectric constants but also have higher thermal conductivity. Our results show that the addition of 17.5 vol % β-SiC whiskers increases the dielectric constants of PVDF/BT nanocomposites from 39 to 325 at 1000 Hz, while the addition of 20.0 vol % β-SiC whiskers increases the thermal conductivity of PVDF/BT nanocomposites from 1.05 to 1.68 W m–1 K–1 at 25 °C. PVDF/β-SiC composites were also prepared for comparative research. It was found that PVDF/BT/β-SiC composites show much higher dielectric constants in compariso...

Large dielectric constant and high thermal conductivity in poly(vinylidene fluoride)/barium titanate/silicon carbide three-phase nanocomposites.

Compared with fuel cells and electrochemical capacitors, dielectric capacitors are regarded as promising devices to store electrical energy for pulsed power systems due to their fast charge/discharge rates and ultrahigh power density. Dielectric materials are core components of dielectric capacitors and directly determine their performance. Over the past decade, extensive efforts have been devoted to develop high-performance dielectric materials for electrical energy storage applications and great progress has been achieved. Here, we present an overview on the current state-of-the-art lead-free bulk ceramics for electrical energy storage applications, including SrTiO3, CaTiO3, BaTiO3, (Bi0.5Na0.5)TiO3, (K0.5Na0.5)NbO3, BiFeO3, AgNbO3 and NaNbO3-based ceramics. This review starts with a brief introduction of the research background, the development history and the basic fundamentals of dielectric materials for energy storage applications as well as the universal strategies to optimize their energy storage performance. Emphases are placed on the design strategies for each type of dielectric ceramic based on their special physical properties with a summary of their respective advantages and disadvantages. Challenges along with future prospects are presented at the end of this review. This review will not only accelerate the exploration of higher performance lead-free dielectric materials, but also provides a deeper understanding of the relationship among chemical composition, physical properties and energy storage performance.

High-performance lead-free bulk ceramics for electrical energy storage applications: design strategies and challenges

This article discusses the theoretically deduced mechanisms for the magnitude and the trends of conduction and polarization in electrical insulation (dielectrics) with molecular and physical structure, frequency, and temperature. The discussion intends to explain the atomic, electronic, molecular, and ionic basis for these electrical properties, so that the reader can better understand why dielectrics behave the way they do. Application of these principles should also guide the reader to make estimates or rough predictions of conductivity and dielectric constant levels, and their variations, from an examination of the molecular/atomic composition of a material. Most of the discussion is more directly applicable to the condensed phases, solids and liquids. Gases, in principle, behave the same, but they have important differences because of their very much lower density and lack of restraint to molecular rotation and translation. An overriding factor in the magnitude of conduction and polarization is the number density of the participating species: electrons, ions, or dipolar molecules

T.W. Dakin

Papers

Conduction and polarization mechanisms and trends in dielectric