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A novel functional nanocomposites microwave shielding material using natural rubber (NR) loaded with binary active fillers barium hexaferrite (BF) (BaFeO) and carbon nanoparticle (CB) were fabricated by conventional roll milling technique. Nanocrystalline barium hexaferrite with particle size of 16 nm were successfully synthesized by hydrothermal approach at low temperature. The surface morphology of the nanocomposites was investigated using X-ray, field emission scanning electron microscopy and transmission electron microscopy. The electrical resistivity of the nanocomposites is decreased with BF loading level. The dielectric constant of the composites is decreased with increasing microwave frequency. NR/BF nanocomposites were screened for electromagnetic interference (EMI) shielding effectiveness (SE) over a frequency band of 1-12 GHz. A maximum SE value is approximately 75 dB in the frequency range of 1-12 GHz for BF content of 20 wt % and thickness of 1 mm. An excellent agreement between the theoretically predicted SE and the measured data was found. These features collectively demonstrated the potential of NR/BF nanocomposites for versatile applications in microwave shielding application and commercial electronic devices issues. [ABSTRACT FROM AUTHOR]

Nano-structured graphene oxide (GO) freestanding paper was synthesized by an arc recharge technique in flowing of oxygen for the first time. This technique offers new ways on how e.g. layers structure nanomaterials could be produced. The morphology and structural properties of the as-synthesized GO were examined by means of X-ray diffraction, Fourier transform infrared spectra, scanning electrom microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy and selective area electron diffraction techniques. The structural and morphological characterizations revealed that the synthesized GO were well-defined nanosheets with a thickness of 6 nm. The optical band gap was calculated from the absorption spectrum, and was found to be 3.32 eV. Furthermore, we aim to use GO paper to develop new electromagnetic interference shielding sheets that have a high shielding effectiveness (SE) (over 30 dB) at frequencies in the 1-12 GHz range. The complex permittivity and total shielding effectiveness of as synthesized GO freestanding paper are measured at frequencies from 1 to 12 GHz. Finally, to enhance the performances of the electromagnetic shields effectiveness, five-layered GO sheets were made. Furthermore, the highest SE for the light-weight freestanding GO paper was 50 dB at 1 GHz, indicating commercial use for many industrial or military shielding applications as an attractive candidate for the new type of microwave shielding. [ABSTRACT FROM AUTHOR]

Conductive polymer composites are at the forefront of composites science research because of the huge number of applications that have been developed around their interesting and unique properties. The present article is focused on the fabrication of natural rubber/polyaniline (NR/PANI) compounds for electromagnetic wave shielding applications at microwave frequency. Their microstructures were examined by means of scanning electron microscopy and thermogravimetric analyses. The as-fabricated NR/PANI composite was mechanically characterized to investigate the effect of dispersion of PANI on NR matrix composite. The dielectric spectroscopy, absorption loss, and reflection loss of NR/PANI composite in the frequency range from 1 to 12 GHz have been performed. The total electromagnetic interference shielding effectiveness by absorption and reflection loss depends on PANI content in the composite. Results show that the NR/PANI composite represents a new class of conducting lightweight material that makes the NR/PANI with good electromagnetic shielding effectiveness that is suitable for use in industrial application such as electronic conducting composite in polymer package and for radar absorbing materials. [ABSTRACT FROM AUTHOR]

In this study, the influence of carbon nanotubes (CNT) in concentrations from 2 to 10 phr on the dielectric (dielectric permittivity, dielectric loss angle tangent) and microwave (reflection coefficient, attenuation coefficient, shielding effectiveness) properties of nanocomposites on the basis of natural rubber has been investigated in the wide frequency range (2–12 GHz). Some additional investigations on the morphology and microstructure of the CNT used and studied composites have been carried out by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results achieved allow recommending carbon nanotubes as filler for natural rubber based composites to afford specific dielectric and microwave properties. [ABSTRACT FROM PUBLISHER]

A novel nitrile butadiene rubber (NBR)/magnetite (Fe3O4) nanocomposite for electromagnetic interference (EMI) shielding at microwave frequency was successfully fabricated. The structural features of as-synthesized magnetite and NBR/Fe3O4 were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The number of elastically effective chains, volume fraction of rubber, interparticle distance among conductive sites, polymer-filler interaction, and porosity of the nanocomposites were evaluated. The mechanical properties, including the tensile strength, elongation at break, and hardness, of the composites were measured. The static electrical properties, such as the electrical conductivity, carrier mobility, and number of charge carriers, as a function of magnetite content were evaluated. The interrelation between the electrical conductivity, shielding effectiveness (SE), dielectric constant, and skin depth of the composites are discussed. Finally, the EMI SE versus frequency was tested. The results reveal that an SE of 28-91 dB against EMI in the 1-12 GHz range depended on the loading of the conducting magnetite within the NBR matrix. Accordingly, these nanocomposites may used in the field of microwave absorption devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

The study presents the effect that two elastomeric matrices different in their chemical nature (a non-polar and crystallizing natural rubber and a polar and non-crystallizing acrylonitrile-butadiene rubber) have upon the electrical properties and shielding effectiveness of composites comprising different amounts of conductive carbon black. Various factors (filler concentration, pressure and temperature) were taken into consideration. The experimental results show that the matrices studied and their specific properties have a great impact upon both electrical properties and shielding effectiveness of the composites based on them. It was found out that there is a strong correlation dependency between the volume resistivity and the electromagnetic shielding effectiveness. With the acrylonitrile butadiene rubber the degree of correlation is higher than in natural rubber, which is associated with the contribution of attenuation and reflection for the formation of shielding effectiveness value. [ABSTRACT FROM AUTHOR]

Abstract: Poly(vinyl Chloride)/graphite nanosheet/nickel (PVC/GN) nancomposites are new alternative candidates for electrostatic charge dissipation and electromagnetic interference shielding applications due to their lightweight, ease processing and tunable conductivities. The structures of the nanocomposites were examined by means of scanning electron microscopy (SEM) and X-ray analysis. The mechanical properties such as hardness, modulus of elasticity and elongation at break as a function of GN content were examined. The applicability of the nanocomposites as electrostatic charge dissipation was tested in terms of displaying the variation of decay voltage with time. In addition, the dielectric properties such as real and imaginary permittivity of composites as functions of frequency were investigated. Finally, the electromagnetic properties were measured in the frequency range from 1 to 12GHz and compared with theoretical modeling. The highest shielding effectiveness at microwave frequency of these nanocomposites was 47dB which is realistic for defense applications like radar evasion. [Copyright &y& Elsevier]

The modern advances in portable and flexible electronic devices require integration of flexibility into future electromagnetic interference shielding nanocomposites. Lightweight and flexible acrylonitrile butadiene rubber/graphene nanosheets (NBR/GN) nanocomposites were fabricated using conventional rubber – roll milling technique. The surface morphology of as prepared GN and NBR/GN nanocomposites were examined by scanning and high resolution electron microscopy. The incorporation of GN nanosheets into NBR matrix has significantly enhanced the mechanical properties and electrical conductivity of nanocomposites. The dielectric properties of (NBR/GN) in the frequency range from 1 GHz to 12 GHz were studied. The electromagnetic interference shielding effectiveness (SE) of conducting NBR/GN nanocomposites was studied as a function of GN content, frequency and thickness of absorber and their interrelation was explored. We found an excellent agreement among theoretically predicted shielding effectiveness and the experimental data. The obtained results revealed that NBR/GN nanocomposites can be used as very effective, lightweight microwave shielding materials for spacecraft, aircraft, microelectronic and structural applications. [ABSTRACT FROM AUTHOR]