SM Abbas | DMSRDE - Academia.edu (original) (raw)

Papers by SM Abbas

Nano-composites in toroidal shaped sample have been prepared and electromagnetic (EM) and microwa... more Nano-composites in toroidal shaped sample have been prepared and electromagnetic (EM) and microwave absorbing properties at different thicknesses have been studied using simulation code for metal backed single layer absorber. The vector network analyser (Model PNA E8364B, Software module 85071E) attached with coaxial measurement set up has been utilised to investigate the EM and microwave absorbing properties of the samples in the frequency range of 2-18 GHz. The fabrication of the sample has been carried out using carbon black powder and multiwall carbon nano-tubes (MWCNT) in different ratios as filler in two component polyurethane (PU) matrix. The complex permittivity of the composite has been found to be frequency dependent. The findings reveals that the absorption performances of the composite sample having 250 mg carbon black and 50 mg MWCNT in one ml polyurethane showed minimum absorption peak of-26.2 dB (R L, min,) at a matching frequency (f m) of 11.6 GHz and more than-10 dB loss in the frequency range of 10.3 GHz to 13.5 GHz for the sample thickness of 2.0 mm. The morphology and thermal behavior of the nanocomposite samples have also been investigated through scanning electron microscope (SEM) and thermo gravimetric analysis (TGA) techniques.

Journal of Electronic Materials

Journal of Thermal Analysis and Calorimetry

Applied Physics A

The electromagnetic ͑EM͒ and microwave absorption properties of ͑Co 2+-Si 4+ ͒ substituted barium... more The electromagnetic ͑EM͒ and microwave absorption properties of ͑Co 2+-Si 4+ ͒ substituted barium hexaferrite compositions BaCo x 2+ Fe y +2 Si x+y 4+ Fe 12−2x−2y +3 O 19 ͑x = 0.9 and y = 0.0, 0.05, and 0.2͒ and its polymer composites prepared from hexaferrite, polyaniline, and carbon powders dispersed in polyurethane matrix have been investigated at the microwave frequency range of the X band ͑8.2-12.4 GHz͒. The hexaferrite compositions were synthesized by solid-state reaction technique, whereas polyaniline, by chemical route. The permeabilities of a ferrite are drastically reduced at higher gigahertz frequencies. The permittivities, however, can be enhanced by appropriate choice of composition and processing temperature. In the present ferrite composition, silicon content is taken in excess so as to convert some of the Fe 3+ ions to Fe 2+ ions. This conversion has been shown to enhance EM and absorption properties. Mössbauer spectroscopy on the samples establishes that addition of excess Si 4+ converts some of the Fe 3+ to Fe 2+. The sintered ferrites have shown resonance phenomena, but the composites do not. The EM parameters Ј, Љ, Ј, and Љ were measured using a vector network analyzer ͑Agilent, model PNA E8364B͒. These measured EM parameters were used to determine the absorption spectra at different sample thicknesses based on a model of a single layered plane wave absorber backed by a perfect conductor. The sintered ferrite composition ͑x = 0.9 and y = 0.05͒ showed the best absorption properties ͓a minimum reflection loss of −17.7 to − 14.3 dB over the whole frequency range of the X band ͑8.2-12.4͒ for a sample thickness of just 0.8 mm͔, and it is used in the composite absorbers in powder form along with other constituents. The optimized composite absorber has shown dielectric constant Ј ϳ 11.5, dielectric loss Љ ϳ 2.3, and a minimum reflection loss of −29 dB at 10.97 GHz with the −20 dB bandwidth over the frequency range of 9.7-12.2 GHz for a sample thickness of 2.0 mm. The magnetic parameters Ј and Љ for the composite remained nearly 1 and 0, respectively, throughout the measured frequency range. Both sintered ferrite and composite absorbers can fruitfully be utilized for suppression of electromagnetic interference and reduction of radar signatures ͑stealth technology͒.

Journal of Thermal Analysis and Calorimetry, 2014

ABSTRACT Nanocomposites of the segmented polyurethane (SPU) polymer containing different grades o... more ABSTRACT Nanocomposites of the segmented polyurethane (SPU) polymer containing different grades of Cloisite® nanoclay at 3 mass% loading have been prepared. The morphology of the prepared nanocomposites has been viewed through scanning electron microscope combined with energy dispersive X ray for the confirmation of the nanocomposite formation. Their non-isothermal crystallization kinetics have been investigated by applying modified Avrami and combined Avrami–Ozawa equations at four different cooling rates using a modulated differential scanning calorimeter. The crystallization parameters e.g., peak temperature (T p), associated enthalpy (ΔH), etc., have been calculated. It has been observed that the addition of nanoclay into SPU accelerates the rate of nucleation and thereby, growth of crystallization in SPU. The Avrami exponent ‘n’ has shown two dimensional growth, while the rate constant ‘Z c’ indicates an increase in the crystallization rate with increasing rate of cooling. The activation energy of the crystallization process has been calculated using Kissinger method. The glass transition temperature has also been estimated using thermomechanical analyzer, and the nanocomposites show superiority over the neat SPU.

Journal of Nanoscience and Nanotechnology, 2007

Polyaniline powder in nanosize has been synthesized by chemical oxidative route. XRD, FTIR, and T... more Polyaniline powder in nanosize has been synthesized by chemical oxidative route. XRD, FTIR, and TEM were used to characterize the polyaniline powder. Crytallite size was estimated from XRD profile and also ascertained by TEM in the range of 15 to 20 nm. The composite absorbers have been prepared by mixing different ratios of polyaniline into procured polyurethane (PU) binder. The complex permittivity (epsilon' - jepsilon") and complex permeability (mu' - jmu") were measured in X-band (8.2-12.4 GHz) using Agilent network analyzer (model PNA E8364B) and its software module 85071 (version 'E'). Measured values of these parameters were used to determine the reflection loss at different frequencies and sample thicknesses, based on a model of a single layered plane wave absorber backed by a perfect conductor. An optimized polyaniline/PU ratio of 3:1 has given a minimum reflection loss of -30 dB (99.9% power absorption) at the central frequency 10 GHz and the bandwidth (full width at half minimum) of 4.2 GHz over whole X-band (8.2 to 12.4 GHz) in a sample thickness of 3.0 mm. The prepared composites can be fruitfully utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).

Journal of Magnetism and Magnetic Materials, 2007

The complex permittivity (e 0-je 00), complex permeability (m 0-jm 00) and microwave absorption p... more The complex permittivity (e 0-je 00), complex permeability (m 0-jm 00) and microwave absorption properties of ferrite-polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2-12.4 GHz) frequency range. The M-type hexaferrite composition BaCo +2 0.9 Fe +2 0.05 Si +4 0.95 Fe +3 10.1 O 19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe +3 to Fe +2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured complex permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters e 0 , e 00 , m 0 and m 00 are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of À24.5 dB (499% power absorption) at 12 GHz with the À20 dB bandwidth over the extended frequency range of 11-13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).

Journal of Alloys and Compounds, 2012

Bulletin of Materials Science, 1998

A new hexaferrite composition, BaCo~Si +yFelz_2~_yO19 (x = 0-90; y = 0-05), in fine (-la size) po... more A new hexaferrite composition, BaCo~Si +yFelz_2~_yO19 (x = 0-90; y = 0-05), in fine (-la size) powder form, is prepared. Ferrite paint formulations are made by dispersing this powder in different weight proportions in an epoxy resin. X-band (8-12 GHz) microwave absorption behaviour of the paint coatings of different thicknesses is studied. Remarkably high value, > 10 dB, of signal absorption at 9-5 GHz is observed for a coating thickness of 0.60 mm with a ferrite fill factor of 57 wt%.

Toroidal shaped sample of particulate composite with 30% (by wt.) Ni-Zn nano-ferrite loaded in po... more Toroidal shaped sample of particulate composite with 30% (by wt.) Ni-Zn nano-ferrite loaded in polyurethane (PU) matrix has been successfully prepared. Microwave absorption properties of prepared Ni-Zn ferrite based nano composite have been studied. Simulation study for metal backed single layered absorber has been carried for probing the electromagnetic (EM) absorbing properties for different thicknesses of the samples. The vector network analyser (Model PNA E8364B, Software module 85071E) attached with coaxial measurement set up has been utilized to investigate the complex permittivity & permeability. Microwave absorbing properties were investigated by utilizing the measured values of complex permittivity and complex permeability of the absorber in a frequency range of 110 MHz to 18 GHz. Reflection loss (dB) has also been determined for various thicknesses of the composite employing the simulation code. SEM and TGA were performed to analyse the morphological and thermal behaviour ...

Materials Science and Engineering: B, 2005

The complex permittivity (e 0 -je 00 ), complex permeability (m 0 -jm 00 ) and microwave absorpti... more The complex permittivity (e 0 -je 00 ), complex permeability (m 0 -jm 00 ) and microwave absorption properties of ferrite-polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2-12.4 GHz) frequency range. The M-type hexaferrite composition BaCo +2 0.9 Fe +2 0.05 Si +4 0.95 Fe +3 10.1 O 19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe +3 to Fe +2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured complex permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters e 0 , e 00 , m 0 and m 00 are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of À24.5 dB (499% power absorption) at 12 GHz with the À20 dB bandwidth over the extended frequency range of 11-13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).