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Islamabad, Pakistan

Khan L.A.,Center for Emerging science | Mahmood A.H.,NED University of Engineering and Technology | Khan Z.,National University of Sciences and Technology
Polymer Composites | Year: 2013

Poly epoxy is a high performance room temperature cured epoxy system which provides excellent physical and mechanical properties. However, the effects of post curing of this resin system on the properties of different sandwich structures are unknown. This study aims to evaluate the effect of post curing (at 70°C for 2 hr) on the edgewise compressive and flexural strengths of a sandwich structure, constructed with Styrofoam and honeycomb as core materials and a plain weave carbon fabric as face sheet. Tested factors evaluated from edgewise compressive tests were as follows: peak load, compressive strength, and crash energy absorption of sandwich structures while core shear stress and bending stress of sandwich structures were determined and compared with flexural tests. It was observed that post curing affects significantly on the bending and compressive strengths of the sandwich structures. However, the data obtained for crash energy absorption suggested that the effect of post curing on the core shear strength and the total deflection was statistically insignificant. The matrix polymer was also inspected using dynamic-mechanical thermal analysis to assess the changes in glass transition temperature and degree of conversion due to post cure. © 2013 Society of Plastics Engineers. Source


Anwar H.,National University of Sciences and Technology | Maqsood A.,Center for Emerging science | Pervaiz E.,National University of Sciences and Technology
Journal of Superconductivity and Novel Magnetism | Year: 2013

The Mn0.5Ni0.5Fe2O4 nanoferrites with different morphology were prepared using the PEG assisted coprecipitation method. The two different iron salts were used for preparing the Mn-Ni ferrites with different morphologies by the coprecipitation air oxygenation method. Spherical and acicular nanoparticles were obtained by the calcination of the precursor. The phase, morphology, and crystallite size of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Magnetic properties were measured by the vibrating sample magnetometer (VSM). The saturation magnetization (Ms ), coercivity (Hc ) and Bohr magneton (nB ) were found to be increased with an increase in effective anisotropy. The dielectric properties were found to decrease with the increased heterogeneity in the samples. The dielectric constant (ε′) and dielectric loss (tanδ) measured from 20 Hz to 1 GHz and variation in magnitudes show dependence on morphology of the prepared samples. Impedance spectroscopic measurements revealed that the electrical conduction in ferrite ceramics is due to resistance of grains interior. © 2013 Springer Science+Business Media New York. Source


Azad F.,National University of Sciences and Technology | Maqsood A.,Center for Emerging science
Electronic Materials Letters | Year: 2014

Nano crystalline erbium oxide (Er2O3) was synthesized in the laboratory through sol-gel method. The effect of different annealing temperatures on the crystal structure has been studied using x-ray diffraction (XRD). The comparison of the specific surface area (s); calculated using Brunauer, Emmett & Teller theory and (XRD) results, was made and found in agreement with an approximate error of 7%. The morphology of the samples has been studied using scanning electron microscope (SEM) and particles are found having a spherical morphology. Elemental analysis of the erbium oxide was also carried using energy dispersive spectrum (EDS) of the synthesized samples. Fourier transform infrared spectrum (FTIR) of the prepared samples showed the characteristic peaks for Er2O3. The dielectric properties of Er2O3 were also studied in the wide range of frequency (100 Hz - 5MHz). The activation energy for erbium oxide was found to be between 0.5-0.8 eV in the temperature range of 373 K-573 K. Hall effect measurements were done on the synthesized erbium oxide and it was found that erbium oxide can have useful applications in the Hall effect sensors (HES). © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Source


Anwar H.,National University of Sciences and Technology | Maqsood A.,Center for Emerging science
Electronic Materials Letters | Year: 2013

Polycrystalline nano ferrites with composition Li0.5Mnx/2Zn0.75-x/2Fe2O4 (x = 0.0, 0.3, 0.6, 0.9, and 1.2) were prepared from sol-gel auto combustion method. The formation of single phase cubic spinel structure was confirmed from XRD analysis and IR-spectroscopy (FT-IR), particle morphology with scanning electron microscopy (SEM) and DC electrical resistivity from two probe method. Electromagnetic measurements were performed from 1 MHz - 1 GHz. The results showed Mn addition improves the magneto-dielectric properties of the prepared samples. The low magnetic loss in very high frequency and ultra-high frequency (VHFUHF) makes them useful in miniaturizing the antennas in the frequency range 1MHz to 1000 MHz. The high reflection loss (RL) of 45 dB for x = 0 and relatively wide-band gap made them suitable to use in the lower micro wave (MW) region. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Source


Ahmad I.,Bahauddin Zakariya University | Abbas T.,University of Punjab | Ziya A.B.,Bahauddin Zakariya University | Maqsood A.,Center for Emerging science
Ceramics International | Year: 2014

A series of nanocrystalline Li0.25Ni0.5Fe 2.25-xErxO4 (x=0.00, 0.02, 0.06, 0.08, and 0.10) ferrite powders, having a cubic spinel crystal structure and a low value of coercivity, was synthesized by the sol-gel auto-combustion route. The structure, morphology and magnetic properties of the prepared nanoferrites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the magnetic property measurement system (MPMS). A well-defined single phase spinel structure is confirmed in all the samples by X-ray diffraction analysis. The lattice parameters of the samples increase slightly with increasing the erbium content. The crystallite size of the Er-doped samples is smaller than that of pure Li-Ni ferrite, and decrease regularly in the range of 36.0-14.5 nm. It has been observed that the magnetic properties of these ferrites are strongly influenced by the added erbium content. The magnetic measurements indicate that saturation magnetization (Ms) and coercivity (Hc) decrease gradually with the increase of Er content in the lattice. © 2014 Elsevier Ltd and Techna Group S.r.l. Source

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