Sandeep Kumar Singh; Amit Kumar Yadav; Ranu Pal; M. J. Akhtar; Kamal K. Kar
Abstract
The nano-sized carbon black (NCB) with particle sizes of 15, 25, 55 and 65 nm are added in epoxy matrix in order to investigate the impact of particle sizes on the microwave absorption properties of the nano composites. The NCB powders were characterized by X-ray diffraction and Scanning electron microscopy ...
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The nano-sized carbon black (NCB) with particle sizes of 15, 25, 55 and 65 nm are added in epoxy matrix in order to investigate the impact of particle sizes on the microwave absorption properties of the nano composites. The NCB powders were characterized by X-ray diffraction and Scanning electron microscopy (SEM) for identification of impurity phases. The complex permittivity spectra were recorded for the composites in the frequency range of 8.2-12.4 GHz. The results revealed that the particle sizes had substantial impact on the electromagnetic properties. On decreasing the particle size, the complex permittivity increases first up to certain extent then decreases. Interestingly, the particle size dependent tangent loss of NCB/epoxy composites shows that 25 nm size is most suited for high loss characteristics, whereas, losses decreases with size < 25 nm, which is attributed to high surface area of the particles. In addition, NCB/epoxy composite with 25 nm particle size illustrated substantial EM absorption efficiency at a frequency of 9.5 GHz, with RL reaching −13.2 dB and reflection loss below −10 dB up to 2.5 GHz with thickness of 2.0 mm. The effect of particle sizes on the electromagnetic properties was also discussed. Copyright © 2018 VBRI Press.
Avanish K. Srivastava; Bhumika Samaria; Smita Soni; Virendra S Chauhan; Jitendra Singh; Rajesh K Shukla; Anuj Shukla; Narendra Kumar
Abstract
In the ongoing search for newer materials for microwave absorption applications, the graphene merits a special consideration owing to its outstanding mechanical, thermal and electrical properties. Here, we report investigation on microwave absorption properties of Fe-Co oxide- thermally exfoliated graphene ...
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In the ongoing search for newer materials for microwave absorption applications, the graphene merits a special consideration owing to its outstanding mechanical, thermal and electrical properties. Here, we report investigation on microwave absorption properties of Fe-Co oxide- thermally exfoliated graphene oxide (Fe-Co oxide-TEGO) composite in a frequency range of 8-18 GHz. Fe-Co oxide was synthesized by thermal decomposition of Fe-Co oxide/aniline- formaldehyde copolymer at 900 0C in air. Fe-Co oxide-TEGO hybrid was prepared by physical mixing of Fe-Co oxide and TEGO. Thereafter, hybrid was characterized using scanning electron microscope, energy dispersive X-ray, Fourier transform infrared spectrometer and X-ray diffractrometer. Thereafter, Fe-Co oxide-TEGO composites were prepared by intermixing in different weight % in PU (polyurethane) resin and their electromagnetic and microwave absorption properties were studied. The effect of varying the weight % of Fe-Co oxide in Fe-Co oxide-TEGO composite on electromagnetic properties was also studied. The absorption bandwidth of 3.5 GHz (8.5-12.0 GHz, X-band) and 5.0 GHz (13.0-18.0 GHz, Ku -band) has been achieved using Fe-Co oxide-TEGO composite (50 wt%) with 2.2 and 1.6 mm thickness, respectively. Microwave absorption studies show Fe-Co oxide- TEGO composite as a potential candidate for microwave absorption applications. Copyright© 2018 VBRI Press.
Bhumika Samaria; Avanish K. Srivastava; Virendra S Chauhan; Jitendra Singh; Smita Soni; Manoj K Dhaka; Rajesh K Shukla; Anuj Shukla; Narendra Kumar
Abstract
The discovery of graphene and subsequent development of graphene-based nanocomposites in different matrices including that in polymer is an important addition in the area of nanoscience and technology. This work deals with the studies on the dielectric properties of the nanocomposites of graphite, graphite ...
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The discovery of graphene and subsequent development of graphene-based nanocomposites in different matrices including that in polymer is an important addition in the area of nanoscience and technology. This work deals with the studies on the dielectric properties of the nanocomposites of graphite, graphite oxide (GO) and thermally exfoliated graphene oxide (TEGO) in epoxy matrix. GO was synthesized using modified Hummers method which on heat treatment at ~300 0C resulted into formation of graphene oxide termed as TEGO. The synthesized GO and TEGO were characterized using scanning electron microscope, energy dispersive X-ray, Fourier transform infrared spectrophotometer, Raman spectrometer, X-ray diffractometer, UV-Vis spectrometer, CHNSO analyzer, surface area analyzer, and dc electrical conductivity. Composites using graphite powder (GP), GO and TEGO individually were prepared in epoxy resin. The dielectric (dielectric permittivity, dielectric loss tangent) properties of composites were studied in frequency range of 8 - 12 GHz. Dielectric tangent loss (tande) vary from 0.02 for GP to 0.35 for TEGO. The effect of addition of GP to GO and TEGO composite on dielectric properties was investigated. The order of tandevalues of composites is: TEGO > GP-TEGO > GP-GO> GO >GP. TEGO composite showed significant dielectric loss among the reported composites. The results thus indicate TEGO as filler for epoxy based composites to afford specific dielectric properties, especially as an alternative of much more expensive carbon nanotubes. Copyright © 2018 VBRI Press.
Anandraj J; Girish M. Joshi; Mayank Pandey
Abstract
We have demonstrated the successful preparation of polyvinyl alcohol (PVA) composed CuBi2S3 polyionic (PI) composites. Polymer composites were sensitive to the external stimuli, the modified PVA moiety exhibits excellent electrical property as a function of temperature. The volume resistance measured ...
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We have demonstrated the successful preparation of polyvinyl alcohol (PVA) composed CuBi2S3 polyionic (PI) composites. Polymer composites were sensitive to the external stimuli, the modified PVA moiety exhibits excellent electrical property as a function of temperature. The volume resistance measured by impedance analyzer (40 to 150oC) under broadband frequency (50Hz -1MHz). The negative temperature coefficient (NTC) was observed in the temperature range of 40 to 150oC. It offers the nonlinear resistivity, ρ = 105 (Ω-m) across pure PVA moiety. The influence of polycationic-ions crucial to obtain the gradual decrease of resistivity (ρ) up to 104 (Ω-m). The thermistor characteristics were disclosed as function of polyionic loading (wt %). Copyright © 2017 VBRI Press
Sandeep Kumar Singh; Amit Kumar Yadav; M. J. Akhtar; K. K. Kar
Abstract
Microwave absorbing material of nickel coated exfoliated graphite (Ni-EG) was prepared by electroless deposition in alkaline coating bath. The coating time, which is an important factor to achieve good coverage of Ni particles over exfoliated graphite (EG), was properly controlled during the process. ...
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Microwave absorbing material of nickel coated exfoliated graphite (Ni-EG) was prepared by electroless deposition in alkaline coating bath. The coating time, which is an important factor to achieve good coverage of Ni particles over exfoliated graphite (EG), was properly controlled during the process. Morphology and phases of Ni-EG were investigated by means of SEM and XRD, respectively. Electromagnetic (EM) properties of Ni-EG/epoxy composites were recorded using VNA over the frequency range of 2-18 GHz. Ni-EG/epoxy composites exhibit significant microwave absorption properties for coating time 10, 20, 30 and 40 minutes. Specially, reflection loss value reached -23.7 dB at 10.9 GHz with 6.0 GHz (8.1-14.1 GHz) and 2.0 GHz (10.1-12.1 GHz) of -10 and -20 dB absorption bandwidths, respectively for 40 minutes of deposition time. Therefore, the proposed material has a great potential for stealth applications. Copyright © 2016 VBRI Press.