Encapsulation of gamma-Fe2O3 decorated reduced graphene oxide in polyaniline core-shell tubes as an exceptional tracker for electromagnetic environmental pollution

The ultimate goal of the development of a new material gamma-Fe2O3 decorated reduced graphene oxide (rGO)-polyaniline (PANI) core-shell tubes has been done for absorbing electromagnetic interference (EMI) pollution. Herein, we report on the synthesis and characterization of PANI tubes consisting of rGO decorated with iron oxide nanoparticles (RF). The intercalated RF was synthesized by thermal decomposition of ferric acetyl acetonate in a reducing atmosphere. Furthermore, RF was encapsulated through oxidative polymerization of aniline in the presence of beta-naphthalene sulphonic acid which results in RF-PANI core-shell morphology. Scanning electron microscopy results confirm the formation of tubular core-shell morphology having 5-15 mu m length and 1-5 mu m diameter. The presence of rGO-gamma-Fe2O3 in PANI core enhances the interfacial polarization and the effective anisotropy energy of the composite which contributes to more scattering and leads to high shielding effectiveness (SET similar to 51 dB) at a critical thickness of 2.5 mm. Additionally, the effective complex permeability and permittivity parameters of the composites have been evaluated from the experimental scattering parameters (S-11 & S-21) using theoretical calculations given in Nicholson-Ross and Weir algorithms

Lightweight and solution processible thin sheets of poly(o-toluidine)-carbon fiber-novolac composite for EMI shielding

An attempt has been made to generate lightweight and processible thin sheets of poly (o-toluidine)-carbon fiber (PoTCF) composite for electromagnetic interference shielding. PoTCF composite synthesized by oxidative emulsion polymerization was physically blended with different weight ratios of novolac resin to prepare a new class of composite material, which was further processed to form thin sheets (thickness of similar to 0.85 mm) by a compression moulding technique. In situ incorporation of carbon fiber into the polymer matrix leads to the formation of composites with improved mechanical, thermal, electrical and shielding properties, which were further optimized by varying the amount of novolac resin in the sheets. Structural and morphological studies were carried out by UV-vis, FTIR, XRD and SEM. PoTCF composite sheets with 50 wt% loading of novolac resin have flexural strength of 36.0 MPa and exhibit a shielding effectiveness of 24 dB in the X-band (8.2-12.4 GHz) at a critical thickness of similar to 2.11 mm, which is more than the limit required for techno-commercial applications. Therefore, indigenously fabricated polymer-based sheets would be potentially useful for making durable enclosures for electronic equipment

Barium ferrite decorated reduced graphene oxide nanocomposite for effective electromagnetic interference shielding

There is an increased interest in the development of high performance microwave shielding materials against electromagnetic pollution in recent years. Barium ferrite decorated reduced graphene oxide (BaFe12O19@RGO) nanocomposite was synthesized by a high energy ball milling technique and its electromagnetic properties were investigated in the frequency range of 12.4-18 GHz (Ku band). The results showed that barium ferrite (BaFe12O19) nanoparticles with an average particle size of 20-30 nm were well distributed and firmly anchored onto the surface of the reduced graphene oxide sheets. The obtained nanocomposite exhibited a saturation magnetization of 18.1 emu g(-1) at room temperature. The presence of BaFe12O19 nanoparticles in the nanocomposite enhances the space charge polarization, natural resonance, multiple scattering and the effective anisotropy energy leading to a high electromagnetic interference shielding effectiveness of 32 dB (similar to 99.9% attenuation) at a critical thickness of 3 mm. The results suggested that the as-prepared BaFe12O19@RGO nanocomposite showed great potential as an effective candidate for a new type of microwave absorbing material

Facile synthesis and photoluminescence spectroscopy of 3D-triangular GaN nano prism islands

We report a strategy for fabrication of 3D triangular GaN nano prism islands (TGNPI) grown on Ga/Si(553) substrate at tow temperature by N-2(+) ions implantation using a sputtering gun technique. The annealing of Ga/Si(553) (600 degrees C) followed by nitridation (2 key) shows the formation of high quality GaN TGNPI cross-section. TGNPI morphology has been confirmed by atomic force microscopy. Furthermore, these nano prism islands exhibit prominent ultra-violet luminescence peaking at 366 nm upon 325 nm excitation wavelength along with a low intensity yellow luminescence broad peak at 545 nm which characterizes low defects density TGNPI. Furthermore, the time-resolved spectroscopy of luminescent TGNPI in nanoseconds holds promise for its futuristic application in next generation UV-based sensors as well as many portable optoelectronic devices

High yield synthesis of electrolyte heating assisted electrochemically exfoliated graphene for electromagnetic interference shielding applications

Herein, we demonstrate a facile one pot synthesis of graphene nanosheets by electrochemical exfoliation of graphite. In the present study, we report a significant increase in the yield of graphene by electrolyte heating assisted electrochemical exfoliation method. The obtained results of heating assisted electrochemically exfoliated graphene (utilizing H2SO4 + KOH + DW) synthesis clearly exhibit that the yield increases similar to 4.5 times i.e. from similar to 17% (room temperature) to similar to 77% (at 80 degrees C). A plausible mechanism for the enhanced yield based on lattice expansion and vibration of intercalated ions has been put forward and discussed in details. The quality of graphene was examined by Raman, XPS, FTIR, AFM, SEM, TEM/HRTEM and TGA techniques. The Raman as well as morphogenesis results confirm the quality of the graphene nanosheets. We have used this graphene as electromagnetic interference shielding material where a comparatively large quantity of graphene is required. This graphene exhibits enhanced shielding effectiveness (46 dB at 1 mm thickness of stacked graphene sheets in frequency region 12.4 to 18 GHz) as compared to conventional electromagnetic interference shielding materials, which is greater than the recommended limit (similar to 30 dB) for techno-commercial applications. Thus the present work is suggestive for future studies on enhancement of yield of high quality graphene by proposed method and the use of synthesized graphene in electromagnetic interference shielding and other possible applications

Performance of a nanoarchitectured tin oxide@reduced graphene oxide composite as a shield against electromagnetic polluting radiation

Tin oxide nanoparticles architectured with a reduced graphene oxide composite (SnO2@RGO) have been synthesised by in situ reduction of graphene oxide in the presence of stannous chloride. The microwave shielding performance of SnO2@RGO has been evaluated over the X-band (8.2-12.4 GHz) range. XRD and TEM studies show that the tin oxide nanoparticles are anchored uniformly onto the surface of the reduced graphene oxide sheets. A total electromagnetic interference shielding effectiveness in the order of 62 dB was achieved, which is more than the required values (similar to 30 dB) desired for techno-commercial applications

Tailored polyaniline/barium strontium titanate/expanded graphite multiphase composite for efficient radar absorption

The present paper reports the synthesis of a high-performance microwave absorbing material using a simple, cost-effective and scalable method by encapsulating barium strontium titanate (BST) and expanded graphite (EG) in a polyaniline (PANI) matrix. One of the formulations (higher content of BST) shows shielding effectiveness due to absorption of more than 50 dB (>99.9999% attenuation) with minimum reflection loss (<= 1 dB) in the Ku-band (12.4-18 GHz) frequency range. Another formulation (higher content of EG) shows a total shielding effectiveness of more than 81 dB with a reflection loss of 10 dB. In order to probe the relationship between the observed shielding response and the electromagnetic attributes, dielectric and permeability parameters have been calculated from the measured scattering parameters (S-11, S-22, S-12, S-21) using the Nicolson-Ross-Weir algorithm. The synthesised formulations were characterized thoroughly using XRD, FTIR, TGA, UV, Raman spectroscopy, SEM and HRTEM

Enhanced electromagnetic shielding behavior of multi-walled carbon nanotube entrenched poly (3,4-ethylenedioxythiophene) nanocomposites

Exceptionally high electromagnetic shielding behavior shown by composites of poly (3,4-ethylenedioxythiophene)/multi-walled carbon nanotube (PCNT) which showed maximum shielding attenuation of 58 dB in the Ku-band. The electron micrographs confirm the wrapping of poly (3,4-ethylenedioxthiophene) (PEDOT) over multiwalled carbon nanotubes (MWCNTs) resulting in strong interfacial, electronic and space charge polarizations. The EMI shielding results showed that shielding by PCNT composites are mainly due to shielding effectiveness by absorption rather than shielding attenuation by reflection. Complex permittivity and permeability of composites have been calculated using scattering parameters (S-11 and S-21) based on theoretical calculations given in the Nicolson-Ross-Weir method. The composites were further characterized by Raman spectroscopy, TGA, XRD, and FTIR

New insight into the shape-controlled synthesis and microwave shielding properties of iron oxide covered with reduced graphene oxide

We proposed various approaches for the shape-controlled synthesis of iron oxide-RGO composites to evaluate the effect of different morphologies on their microwave shielding properties. The nature of various ferrite structures (flakes, cubes and rods) covered by reduced graphene oxide multilayers has been investigated using X-ray diffraction, Raman spectroscopy, FT-IR, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopic techniques. The electromagnetic interference (EMI) shielding effectiveness of iron oxide of different shapes coated with reduced graphene oxide was investigated in the Ku band frequency range (12.4-18 GHz). The rod shaped iron oxide covered with reduced graphene oxide sheets demonstrates the highest shielding effectiveness value of similar to 33.30 dB (>99.9% attenuation) as compared to flake and cube shaped iron oxides due to the combined effect of magnetic losses (hysteresis, eddy current loss and effective anisotropy) and dielectric losses (space charge polarization, interfacial polarization, surface defects, multiple scattering, etc.). These innovative proposed structures and their obtained EMI shielding results deliver a new insight into the morphology dependent nature of iron oxides covered with RGO nanosheets and create new opportunities for next generation EMI materials

Multifunctional, robust, light-weight, free-standing MWCNT/phenolic composite paper as anodes for lithium ion batteries and EMI shielding material

Energy density of Li-ion batteries is marred due to the additional weight of copper, which is used as a current collector. In this work, fabrication of strong, graphitized, multiwalled carbon nanotubes (GCNTs)/phenolic composite paper using a new dispersion technique is reported. The composite paper has been used as a free-standing current collector, as well as an anode material for Li-ion batteries, because of its good electrical conductivity of 76 S cm(-1). This highly thin conductive composite paper (thickness 140 mu m) also shows efficient electromagnetic interference (EMI) shielding effectiveness of 32.4 dB in Ku-band (12.4-18 GHz). Moreover, structural and morphological studies were carried out using TEM and SEM. The flexural strength of the composite paper was 30 MPa, which is good enough for use as an electrode in batteries. The electrochemical properties of the composite paper were investigated by galvanostatic charge-discharge test. It exhibits a stable reversible specific capacity for more than 45 cycles. EMI shielding effectiveness (SE) was measured using a vector network analyzer, and the total EMI-SE surpasses the value needed for commercial applications