Dielectric properties of rubber ferrite composites containing mixed ferrites

Abstract

Rubber ferrite composites (RFC) are important since they have useful applications as microwave absorbers and flexible magnets. The mouldability of these composites into complex shapes is another advantage. The evaluation of their dielectric and magnetic properties is important in understanding the physical properties of these composites. Pre-characterized nickel zinc ferrites (Ni1-xZnxFe2O4 where 0 x1 in steps of 0.2) prepared by ceramic techniques were incorporated in to a butyl rubber matrix according to a specific recipe to yield RFCs. The dielectric constant of ceramic Ni1-xZnxFe2O4 and the butyl rubber composites incorporated with Ni1-xZnxFe2O4 are studied as a function of frequency, composition, loading and temperature. The observed data indicates that the dependence of the dielectric constant on frequency follows Maxwell-Wagner interfacial polarization. The compositional (zinc content, i.e. x value) dependence shows that the dielectric constant increases initially and reaches a maximum value for the composition corresponding to x = 0.6 and thereafter it decreases. This can be explained on the basis of porosity and alternating current (AC) conductivity. It was also observed that the dielectric constant of the composite material increases with an increase of the volume fraction of the magnetic filler. These observations satisfy some mixture equations, which correlate the dielectric constant of the matrix, filler and the composites. The temperature dependence of the dielectric constant of the ceramic samples as well as the RFCs shows an increase with an increase of temperature at low frequencies. The dielectric constant of the blank butyl rubber was also determined. It was observed that for a blank sample (without filler) the dielectric constant decreases with an increase of temperature. This is due to the decrease in polymer density with increase in temperature. These results suggest that the magnetic and dielectric properties of RFCs can be manipulated by appropriate loading and a judicious choice of the magnetic filler. The modification of these properties will aid in the design of composite materials for microwave absorbers.

Synthesis of nickel–rubber nanocomposites and evaluation of their dielectric properties

“…The insulating host material can in turn be made conducting or semi-conducting, depending on the amount of filler particles dispersed in the medium [5]. Magnetic fillers are incorporated in rubber matrices to impart magnetic property to the host and such fillers can be metal particles or magnetic oxides like ferrites [6][7][8]. When magnetic oxides are used, very high volume fraction of the filler is necessary to get the required magnetization because of the low density of oxides in comparison to metals.…”

“…Elastomers are flexible materials and composites of these materials can find many useful technological applications mainly due to their flexibility and mouldability [8]. Natural rubber is a commonly available elastomer and there exist reports on the studies on electrical properties of composites based on natural rubber with ferrite particles as fillers [7,8].…”

“…Natural rubber is a commonly available elastomer and there exist reports on the studies on electrical properties of composites based on natural rubber with ferrite particles as fillers [7,8]. However reports on the synthesis of composites of natural rubber dispersed with metal particles are not very abundant in the literature.…”

Structural and Dielectric properties of Co+2 substituted Ni Cu Nanocrystalline Spinel Ferrite Material

“…According to Koop's, at lower frequencies, the resistivity is high and the principal effect is of the grain boundaries (low resistivity regions). Therefore, the energy required for electron hopping between Fe 2+ and Fe 3+ at the grain boundaries is higher and the energy losses (tan δ and ε′′) are larger [20][21][22][23][24][25]. The rapid decrease of dielectric constant at lower frequencies is explained on the basis of space charge polarization.…”

Shielding effectiveness measurements and uncertainty estimation for textiles by a VNA-based free space transmission method

“…For SE applications, materials with electromagnetic screening capabilities are generally used to attenuate the strength of electromagnetic fields in certain areas. A number of research groups have reported the development of cost effective new materials based on conducting polymers, composites and textiles for a number of reasons to use them as a shield [6][7][8][9][10][11]. The main objective of such R&D is searching a material with high EM absorption, minimum reflection and simpler production process with easy adaptability for applications.…”