Effect of high aspect ratio filler on dielectric properties of polymer composites: a study on barium titanate fibers and graphene platelets

Abstract

High aspect ratio fillers are predicted to increase the dielectric constant of polymer composites more efficiently than spherical fillers according to the rule of mixtures. Using high aspect ratio fillers is a promising route for creating high dielectric constant, low loss materials at a low filler volume fraction, for use as capacitor and electric field grading materials. In this work, two high aspect ratio fillers were mixed into a polymer matrix, and the dielectric properties of composites were studied. Barium titanate fibers were synthesized by electrospinning a sol-gel, followed by a heat treatment to obtain a perovskite crystal structure. The heat treatment conditions were found to be crucial for obtaining tetragonal barium titanate fibers with high dielectric constant. Graphene platelets were prepared by a thermal shock method, which was found to result in a larger dielectric constant. A combination of barium titanate and graphene platelets yielded the highest dielectric constant when used in a polydimethyl siloxane matrix. The increase in dielectric loss over the pure matrix was small when the volume fraction was below the percolation threshold of graphene platelets. Electric flux density-electric field (D-E) measurements showed a linear dielectric constant in barium titanate filled composites and higher loss when graphene was added. The ac breakdown strength was reduced compared to the neat polymer and was affected by filler aspect ratio. The mechanisms that lead to the observed phenomena are discussed.

Dielectric silicone elastomers with mixed ceramic nanoparticles

“…There are different types of fillers that are generally used for improving the permittivity of the dielectric elastomer: i) ceramic particles with a high dielectric constant -most used are titanium dioxide, barium titanate, magnesium niobate, lead magnesium niobate-lead titanate, and strontium titanate nanoparticles [13][14][15]; ii) conductive particles, such as carbon nanotubes, carbon black, copper-phthalocyanine/polyaniline [16]; iii) highly polarizable conjugated polymers -undoped poly(3-hexyltiophene), polyaniline, or polythiophene incorporated by blending [10,14,[17][18][19][20][21].…”

Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

“…This is because heating prediction using the first law of thermodynamics becomes possible by improving the MW absorption of the powder. Wang et al [11] reported that the heating behavior of mixed powders of BaTiO 3 fibers and graphene is consistent with the Maxwell-Garnett rule at low densities. They predicted the heating behavior of the fiber using the shape factor of the Maxwell-Garnett rule derived from an elliptic model.…”

“…The relationship between the powder (or slurry) density and its MW heating behavior is an important issue. Wang et al [11] investigated graphene platelets to develop TiBaO 3 fibers and concluded that the loss of graphene platelets increased dramatically when the loading reached the percolation threshold. Yoshikawa et al [12] measured the complex permittivity and direct current (DC) conductivity of FeO(OH)/C and trichloropropane/C mixtures, and analyzed the measured data using the percolation theory.…”

Polarization Parameters and Scaling Matter—How Processing Environment and Shape Factor Influence Electroactive Nanocomposite Characteristics

“…Two phase composites with randomly distributed electrically conductive fillers have drawn a lot of attention in the past few years due to their scalability and the ease of processing techniques and their flexibility [74,102]. Towards the direction of fabrication of embedded passive components, two phase metal-polymer and metal-ceramic composites has been studied to obtain high dielectric constants of >500 [103,104]. Among these materials two-phase composites with MWCNT as conductive inclusions randomly distributed in a relaxor ferroelectric matrix, PMMA show improvements in electrical properties with increased volume fraction of the conductive inclusion [79,80] and exhibit a dramatic increase in electrical properties around the critical concentration around 0.1% of MWCNT by weight, known as the percolation threshold [3,22].…”