Rajesh Kalia; J. K. Sharma; Sapna Kalia
Abstract
The dielectric constant (ε') and dielectric loss (ε״) of pristine and C5+ (70 MeV) ion irradiated samples of the PEEK have been investigated with the variation of temperature at different frequencies (100 Hz, 1 kHz, 10 kHz and 100 kHz). The maxima are obtained around 170 oC in dielectric ...
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The dielectric constant (ε') and dielectric loss (ε״) of pristine and C5+ (70 MeV) ion irradiated samples of the PEEK have been investigated with the variation of temperature at different frequencies (100 Hz, 1 kHz, 10 kHz and 100 kHz). The maxima are obtained around 170 oC in dielectric constant (ε') vs. temperature (T) curve. This relaxation is linked with the movement of ketone (>C=0) dipoles linked to the main chain. The irradiation of polymers increases the orientational polarization due to increase in number of dipoles with fluence. The increase in dielectric constant (ε') and dielectric loss (ε'') is attributed to chain scissioning at higher fluence which results in an increase of free radicals and unsaturations. 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.
Sanatombi Sorokhaibam; Ibetombi Soibam; Sumitra Phanjoubam
Abstract
Substituted lithium ferrite having the chemical formula Li0.35 Ni0.1 Mn0.1 Zn0.2 Fe2.35 O4 have been synthesized by the citrate precursor method. The sample was given pre-sintering at 650oC in a conventional furnace. Final sintering was carried out at 900oC in a conventional surface and another ...
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Substituted lithium ferrite having the chemical formula Li0.35 Ni0.1 Mn0.1 Zn0.2 Fe2.35 O4 have been synthesized by the citrate precursor method. The sample was given pre-sintering at 650oC in a conventional furnace. Final sintering was carried out at 900oC in a conventional surface and another in a microwave furnace. The spinel phase structure of the conventional (CS) and microwave sintered (MS) samples was confirmed by the XRD patterns. From the analysis of XRD data, the crystallite size of the samples was estimated and smaller crystallite size was observed in the microwave sintered sample. Scanning Electron Microscopy (SEM) was also carried out. The dielectric studies were investigated. Room temperature dielectric constant ( ) and dielectric loss (tan d) were studied as a function of frequency. Experimental results show dispersion for variation of dielectric constant and dielectric loss tangent with frequency for both CS and MS sample. However, microwave sintered sample show lower dielectric constant and losses. Possible mechanism is being discussed. Copyright © 2016 VBRI Press.
Sathosh K. Kurni; Pradip Paik
Abstract
SiO2 nanoparticles of average size 15-20 nm have been synthesized and its dielectric properties have been investigated as a function of frequency (between 20 Hz to 2 MHz). A very high dielectric constant of ca. 14000 at 20 Hz and at room temperature has been observed which is very high compared to the ...
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SiO2 nanoparticles of average size 15-20 nm have been synthesized and its dielectric properties have been investigated as a function of frequency (between 20 Hz to 2 MHz). A very high dielectric constant of ca. 14000 at 20 Hz and at room temperature has been observed which is very high compared to the conventional bulk SiO2 particles (ca. 50-100). For this new SiO2 the loss value is found to be less than 1. These SiO2 nanoparticles with high dielectric constant and low loss can be offered its use in constructing high efficient electronic circuit boards and storage devices. Spectra between real and imaginary parts of dielectric constant reveal an inclined line with depressed semicircle. Impedance measurements have been performed to know the electrical properties of the novel SiO2 nanoparticles. XRD, TEM and FTIR characterizations confirm the solid state network structural, morphological shape and size, and chemical functionality of SiO2 respectively. Copyright © 2016 VBRI Press
