Physical Properties of Composites Near Percolation

Abstract

Dramatic changes in the physical properties of composites occur when filler particles form a percolating network through the composite, particularly when the difference between the properties of the constitutive phases is large. By use of electric conductivity and dielectric properties as examples, recent studies on the physical properties of composites near percolation are reviewed. The effects of geometric factors and intrinsic properties of the fillers and the matrix, and especially of the interface between fillers and matrix, on electric and dielectric properties near percolation are discussed. Contact resistivity at the interface is less desirable for enhancing electrical conductivity. By contrast, an interface with high resistivity suppresses tunneling between adjacent fillers and leads to percolative composites with higher dielectric constant but lower dielectric loss. This review concludes with an outlook on the future possibilities and scientific challenges in the field.

Tuning Electrical and Thermal Properties in Epoxy/Glass Composites by Graphene-Based Interphase

“…As it can be seen in Figure 8a, the permittivity level did not change as the applied frequency increased, which is in accordance with the behavior commonly observed for insulating materials such as epoxy and GF [34]. Due to the insulating nature of GO, coating of GF with GO did not provide any capacitive properties to Ep-GO-GF composite.…”

Obtaining ultimate functionalities in nanocomposites: Design, control, and fabrication

“…The dielectric constant of such a nanocomposite diverges at the percolation threshold f c , at which suffi cient nanoparticles are present to form a long-range connected network . 12 Many experiments have shown that, near to f c , the dielectric constant of the composite can become unbounded and extraordinarily high compared to that of the dielectric matrix. This composite effect comes from many conductive nanoparticles being isolated by thin dielectric layers, thus forming nanocapacitors.…”

Effects of magnetic field treatment on dielectric properties of CCTO@Ni/PVDF composite with low concentration of ceramic fillers

“…According to percolation theory, a composite's dielectric and conductive properties will enhance extraordinarily when its filler concentration is close to the percolation threshold. 9,20 The increases in dielectric permittivity and conductivity of PVDF#1 over PVDF#0 likely resulted from the percolation effect. These results demonstrate that magnetic field treatment may induce the percolation effect at a low loading of 5 vol.% and enhance the interfacial polarization effect, improving the dielectric permittivity of the composite by several orders of magnitude.…”

“…The loss tangent of PVDF#1 was as high as 10 3 at 10 Hz; as the frequency increased, the loss tangent increased slightly and then decreased dramatically above 10 3 Hz, which may have been caused by the percolation effect enhancing the conductivity. 13,20 The loss tangents of PVDF#2 FIG. 7.…”

“…However, this improvement in dielectric permittivity is still far from satisfactory; ideally, the improvement would be several orders of magnitudes at a relatively low volume-fraction loading, perhaps even below the percolation threshold in percolation composites. 9,20 However, there are few reports on ceramic/polymer composites with CCTO ceramics modified with magnetic nanoparticles.…”