Janan Hameed Saadie Taai

a non-destructive technique for simultaneously EM-properties determination of planar radar absorbing materials is presented. The technique is based on using waveguide radiating into multilayered structure to produce the needed independent reflection coefficients necessary to extract the unknown EM-properties at X-band of microwave frequency range. The measurement geometry consists of rectangular waveguide with finite flange placed against a combination of the sample under test and a known material layer backed by a PEC to increase measurement accuracy. To account for finite flange, the geometry is numerically modeled via Finite Difference Time Domain (FDTD) method yielding theoretical values for reflection coefficients which is imposed on the measured ones to obtain both complex pemittivty εr and permeability μr by inverse problem. Measurement results of εr and μr for several samples of radar absorbing materials are presented.

Spray pyrolysis was applied to deposit Tellurium thin film on glass substrates at 498 ± 283 K in order to investigate the influence of thickness on the electrical and optical properties of the prepared thin films. The film thicknesses were measured in situ by weighting method. The thicknesses were from (150 to 800) nm. X-ray diffraction results showed that the Te thin films formed were polycrystalline with hexagonal structure. The effect of film thickness on the electrical properties of the films was investigated by Hall Effect measurement through the analysis of the I-V plots. The conductivity of the films and carrier concentration were highly increased when the films became thicker. Transmission and absorption spectrum of the prepared thin film had been recorded using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300 - 2000 nm. The values of some important optical parameters of the studied films (absorption coefficient, and optical band gap energy) were determined using these spectra. The transmittance showed better results when thicknesses were being increased. In addition, the absorption coefficient is higher for thinner films and decreases for thicker films showing little dependence for absorption coefficient on thin film thickness in infra-red region of the wavelength. It was found from the optical properties studies that the type of transition of Te film is direct transition. Also, the optical energy band gap was evaluated for different thicknesses. The results have shown that the optical energy band gap was increased by the increase of thickness. Experiments and measurement results are presented.

Abstract Carbon adsorbent materials that were prepared from sunflower straw by a combination of pre-treatment and low-temperature pyrolysis showed better adsorption compared with untreated carbon. Four different pre-treatment agents (steam, alkali (KOH), phosphoric (H3PO4), and salt (ZnCl2)) were analyzed with respect to their effects on the maximum surface area and the micropore area. Samples were measured by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), scanning electron ...

Abstract In this work, Tellurium thin film has been prepared by chemical spray pyrolysis deposition on glass substrates. X-ray diffraction spectrum have shown that the prepared film has polycrystalline structure and peaks for Tellurium hexagonal structure. Also, the microstructure analysis using optical microscope illustrated the contrast of topography of this thin film which showed highest homogeneity and regularity. The obtained results of this work are in good agreement with the standard X-ray published data [1]. Optical properties ...