The multiphase approach was adapted to enhance the electromagnetic interference (EMI) shielding effectiveness (SE) of polyaniline (PANI) based nanocomposites. The natural graphite flakes (NGF) incorporated modified PANI was used for the development of multi-walled carbon nanotubes (MWCNTs) based nanocomposites. In PANINGF-MWCNTs composites, multilayer graphene was synthesized in situ by ball milling. The resultant PANINGF-MWCNTs nanocomposites were characterized by different techniques. It was revealed from the transmission electron microscope (TEM) observation that in situ derived multilayer graphene acts as a bridge between PANI and MWCNTs, and plays a significant role for improving the properties of multiphase nanocomposites. It was observed that EMI-SE increases with increasing the MWCNTs content from 1 to 10 wt% in the multiphase nanocomposites. The maximum value of total EMI-SE was -98 dB of nanocomposite with 10 wt% of MWCNTs content. The high value of EMI-SE is dominated by the absorption phenomenon which is due to the collective effect of increase in space charge polarization and decrease in carrier mobility. The decrease in carrier mobility has a positive effect on the shore hardness value due to the strong interaction between the reinforcing constituent in multiphase nanocomposites. As a consequence, shore hardness increases from 56 to 91 at 10 wt% of MWCNTs.

/pdf/multi-walled-carbon-nanotube-graphene-polyaniline-multiphase-irg2kj765x.pdf

Multi-walled carbon nanotube-graphene-polyaniline multiphase nanocomposite with superior electromagnetic shielding effectiveness.

Microwave shielding properties of chemically synthesized MnO2 decorated graphene nanoribbons (GNRs) are reported for the first time. The nature of MnO2 decoration on the GNRs has been investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. The electromagnetic interference (EMI) shielding effectiveness of this material was investigated in the microwave region (Ku-band, 12.4–18 GHz). The presence of MnO2 on GNR enhances the interfacial polarization, multiple scattering, natural resonances and the effective anisotropy energy, which leads to absorption dominated high shielding effectiveness of −57 dB (blocking >99.9999% radiation) by a 3 mm thick sample. Dielectric attributes (e′ and e′′) were evaluated to understand the mechanism of the excellent shielding effectiveness. The material will be an excellent choice for radar absorbing applications.

/pdf/mno2-decorated-graphene-nanoribbons-with-superior-3xugwythxz.pdf

MnO2 decorated graphene nanoribbons with superior permittivity and excellent microwave shielding properties

Graphene quantum dots (GQDs) are an attractive nanomaterial consisting of a monolayer or a few layers of graphene having excellent and unique properties GQDs are endowed with the properties of both carbon dots (CDs) and graphene This review addresses applications of GQD based materials in sensing, bioimaging and energy storage In the first part of the review, different approaches of GQD synthesis such as top-down and bottom-up synthesis methods have been discussed The prime focus of this review is on green synthesis methods that have also been applied to the synthesis of GQDs The GQDs have been discussed thoroughly for all the aspects along with their potential applications in sensors, biomedicine, and energy storage systems In particular, emphasis is given to popular applications such as electrochemical and photoluminescence (PL) sensors, electrochemiluminescence (ECL) sensors, humidity and gas sensors, bioimaging, lithium-ion (Li-ion) batteries, supercapacitors and dye-sensitized solar cells Finally, the challenges and the future perspectives of GQDs in the aforementioned application fields have been discussed

/pdf/graphene-quantum-dot-based-materials-for-sensing-bio-imaging-21zv3c6jzp.pdf

Graphene quantum dot based materials for sensing, bio-imaging and energy storage applications: a review

Free-standing layer-structured Ag nanowire (Ag-NW)/polyaniline (PANI) composite films were prepared via a novel but simple two-step casting process. The as-prepared layer-structured PANI composite film with 14 vol% Ag-NWs show a very high electrical conductivity (EC) of 5300 S cm−1, a reasonably good mechanical strength of 44 MPa and an excellent electromagnetic interference (EMI) shielding efficiency of above 50 dB over a wide bandwidth of 1.2 GHz. Comparatively, the plain-structured composite counterparts prepared via the commonly used direct-mixing process exhibit a higher percolation threshold, a lower EC of 4234 S cm−1 and an inferior EMI shielding performance of above 50 dB over a narrow bandwidth of 0.4 GHz. In spite of this, the plain-structured Ag-NW/PANI composite films also display a relatively higher EMI SE when compared to other PANI based composites reported previously. This study provides a facile and effective strategy to fabricate layer-structured composite films with excellent EMI shielding efficiency in the X-band, which may find applications in electronic devices and radiation sources.

Layer-structured silver nanowire/polyaniline composite film as a high performance X-band EMI shielding material

Increasing use of the latest electronic gadgets in modern society causes rapid growth in electromagnetic pollution, which leads to detrimental effects on the function of highly sensitive precision electronic equipment as well as on human life. Mitigating this effect requires efficient electromagnetic radiation shielding materials, which should be lightweight, corrosion resistant and cost-effective. In this review article, we have presented lightweight polymer composite foams filled with carbon nanofibers, carbon nanotubes and graphene as efficient electromagnetic radiation shielding materials. It is seen that the low loading of multiwalled carbon nanotubes with uniform dispersion in polymer, uniform cell size of pore and controlled dielectric constant results in the attenuation of electromagnetic radiation by absorption phenomena. Flexible graphene–polymer composite foam derived using the chemical vapor deposition technique demonstrates a specific shielding effectiveness of ∼333 dB cm3 g−1, which is the highest value among those reported in literature. The SE is mostly dominated by the absorption of electromagnetic radiation, which is due to the multiple reflection of radiation inside the cells of the composite foam. Moreover, different carbon nanomaterial, such as carbon nanofibers and few layer graphene-filled polymer composite foams, with varying content of conducting filler are reported in this review. Their use in different applications, their future prospective and the challenges ahead are discussed in this review.

Polymer nanocomposite foam filled with carbon nanomaterials as an efficient electromagnetic interference shielding material

Graphene derivatives are intensively used as high performance nano fillers for the fabrication of polymer nanocomposites. The challenge is to achieve significant improvement in interfacial adhesion between polymer matrix and reinforcing filler. In the present work, we report the preparation of polyvinyl chloride (PVC) /Graphene Oxide (GO) composite by the colloidal blending method. PVC/GO composite films were further studied using fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and polarized optical microscopy (POM). The effect of GO loading on wettability of PVC/GO composites films were studied by measuring contact angle of composites films. Optical microscopy reveals that GO have been dispersed homogeneously throughout the PVC matrix. From morphological studies, a network of a denser stacking and randomly aggregate structure having rough surface was observed as a function of GO loading. The values of contact angle decrease with respect to GO loading for all the liquids used. The solid surface energy (SE) of composite films was estimated using contact angle measurements. The surface energies were measured and compared using Fowke’s and Good-Grifalco methods with respect to four different liquids having a wider range of surface tensions (44≤ lv ≤ 72. 8 mJ/m2). The composite film surfaces were tuned by controlling incorporation of GO in order to optimize the surface roughness.

/pdf/surface-properties-of-graphene-oxide-reinforced-polyvinyl-54hysgcw93.pdf

Surface properties of graphene oxide reinforced polyvinyl chloride nanocomposites

Effect of dopant and DC bias potential on dielectric properties of polyvinyl alcohol (PVA)/PbTiO3 - composite films

We have successfully demonstrated the effect of Gamma-irradiation on Polyacrylonitrile (PAN) gel in terms of admittance (Y), Susceptance (B) and Conductance (G). The trend of Y and B decreases by 297 microSec and 138 microSec respectively and conductance (G) increases by 100 μS. Electrical mechanism associated with microstructure of PAN gel under external DC bias potential is the novelty of this work. External field stimuli responded due to delocalization of charge carriers. These properties are important as novel electronic material.

Effect of Gamma-Irradiation on Admittance, Suceptance and Conductance of Polyacrylonitrile Gel

The novel approach was developed for grafting of amine-functionalized multiwall carbon nanotubes with carboxylic acid, modified epoxy resin containing free acid anhydride group, which gives enhance...

S.M. Khatake

Papers

Surface properties of graphene oxide reinforced polyvinyl chloride nanocomposites

Effect of dopant and DC bias potential on dielectric properties of polyvinyl alcohol (PVA)/PbTiO3 - composite films

Effect of Gamma-Irradiation on Admittance, Suceptance and Conductance of Polyacrylonitrile Gel

Grafting of Amine-Functionalized Multiwall Carbon Nanotubes with Free Acid Anhydride in Carboxylic Acid Modified Epoxy