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# MEASUREMENT OF DIELECTRIC CONSTANT AND LOSS FACTOR OF THE DIELECTRIC MATERIAL AT MICROWAVE FREQUENCIES

Progress in Electromagnetic Research 01/2007; 69:47-54. DOI: 10.2528/PIER06111204

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**ABSTRACT:**Composites of rice husks and carbon nanotubes (RHC- NTs) are an innovation in improving the absorption of microwave signals. Rice husks, which are an agricultural waste material, have been found to possess a significant propensity for absorbing microwave sig- nals. Studies have shown that both rice husks and carbon nanotubes (CNTs) have high percentages of carbon. Thus, in this paper, we present the results of our experimental study in which we varied the ratios of rice husks and CNTs in the composite materials and deter- mined the dielectric properties of the composites and measured their abilities to absorb microwave signals. The experimental microwave absorber was fabricated using rice husks and CNTs, which increased the dielectric constant and the loss factor. Complex permittivity was measured using an Agilent dielectric probe. The RHCNT composites were investigated to determine their reflection loss and absorption performance as microwave absorbers. For the fabricated microwave absorber, we used the rectangular waveguide measurement technique to study reflection loss, transmission loss, and absorption performance in the frequency range of 12.4–18 GHz. Carbon has an essential role in the absorber due to its ability reflect/absorb microwave signals. Thus, we compared the abilities of a pure rice-husk (PRH) absorber and RHCNT composites absorbers to absorb microwave signals.Progress In Electromagnetics Research 01/2013; 140:813-831. · 5.30 Impact Factor -
##### Article: Diffusion coefficient of vacancies and jump length of electrons in Co1−x Zn x Fe2O4 ferrites

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**ABSTRACT:**A series of polycrystalline samples of Co1−x Znx Fe2O4 where (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) were prepared by the usual ceramic technique. X-ray diffraction patterns confirmed the spinel cubic structure. The diffusion coefficients of oxygen vacancies were estimated from dc conductivity measurements. It was noticed that the diffusion coefficient decreases with increasing Zn2+ concentrations. An increase of temperature increases the diffusion of lattice vacancies. The Curie temperature, lattice parameter and jump length of electrons were studied as a function of Zn2+ concentration. From the correlation between the ionic radius and the radii of octahedral and tetrahedral sites, the theoretical lattice parameters were calculated and suggested cation distribution for the given ferrites was determined.Journal of Advanced Ceramics. 1(2). - [Show abstract] [Hide abstract]

**ABSTRACT:**PTFE samples were prepared with different thicknesses. Their electric field intensity and distribution of the PTFE samples placed inside a rectangular waveguide were simulated using finite element method. The calculation of transmission/reflection coefficients for all samples thickness was achieved via FEM. Amongst other observable features, result from calculation using FEM showed that the attenuation for the 15 mm PTFE sample is −3.32 dB; the 30 mm thick PTFE sample has an attenuation of 0.64 dB, while the 50 mm thick PTFE sample has an attenuation of 1.97 dB. It then suffices to say that, as the thickness of the PTFE sample increases, the attenuation of the samples at the corresponding thicknesses increases.Advances in Materials Science and Engineering 01/2014; 2014. · 0.90 Impact Factor

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