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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.

Ahmad I.,Bahauddin Zakariya University | Abbas T.,Bahauddin Zakariya University | Islam M.U.,Bahauddin Zakariya University | Maqsood A.,Center for Emerging science
Ceramics International | Year: 2013

Nano sized polycrystalline soft ferrite particles with composition Cu 1-xCoxFe2O4 (x =0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by the sol-gel technique. The existence of well-defined single cubic spinel structure was confirmed in all the samples by X-ray diffraction. The crystallite size found by XRD varied from 14.8 to 34.0 nm. The microstructure was also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Slight expansion of the unit cell was detected with the increase of Cobalt concentration, which may be attributed due to larger ionic radius of Co2+. Lattice parameter ranged from 8.34 Å to 8.37 Å for Co2+ from 0.1-0.9. The distribution of cations amongst A- and B-sites of the lattice was estimated by X-ray diffraction by using the R-factor technique. The results showed that both Cu2+ and Co2+ ions occupy mainly the B-site while Fe3+ ions were equally distributed among A- and B-sites. The data obtained from cation distribution analysis was used to determine the magnetic moment for each sample and VSM studies were also carried out to validate these calculations. Magnetic measurements showed that the saturation magnetization (Ms) and coercivity (Hc) increased with increasing cobalt content. © 2013 Elsevier Ltd and Techna Group S.r.l.

Amin F.,International Islamic University, Islamabad | Ahmed S.,International Islamic University, Islamabad | Ahmed S.,Center for Emerging science
Journal of Physics: Conference Series | Year: 2013

The advancement in semiconductor process engineering and nano-scale fabrication technology has made it convenient to transport specific biological fluid into or out of human skin with minimum discomfort. Fluid transdermal delivery systems such as Microneedle arrays are one such emerging and exciting Micro-Electro Mechanical System (MEMS) application which could lead to a total painless fluid delivery into skin with controllability and desirable yield. In this study, we aimed to revisit the problem with modeling, design and simulations carried out for MEMS based silicon hollow out of plane microneedle arrays for biomedical applications particularly for transdermal drug delivery. An approximate 200 μm length of microneedle with 40 μm diameter of lumen has been successfully shown formed by isotropic and anisotropic etching techniques using MEMS Pro design tool. These microneedles are arranged in size of 2 × 4 matrix array with center to center spacing of 750 μm. Furthermore, comparisons for fluid flow characteristics through these microneedle channels have been modeled with and without the contribution of the gravitational forces using mathematical models derived from Bernoulli Equation. Physical Process simulations have also been performed on TCAD SILVACO to optimize the design of these microneedles aligned with the standard Si-Fabrication lines. © Published under licence by IOP Publishing Ltd.

Butt S.,Institute of Space Technology | Butt S.,National University of Sciences and Technology | Shah N.A.,COMSATS Institute of Information Technology | Nazir A.,Italian Institute of Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

Polycrystalline CdS thin films were deposited on glass substrates by close spaced sublimation technique. Samples of various thicknesses, ranging from 250 to 940 nm were obtained. The optical and electrical properties of pure CdS thin films were studied as a function of film thickness. The resistivity of as-deposited CdS films was in the order of 106-108 Ω cm, depending upon the film thickness. In the high temperature region, carriers are transported over the grain boundaries by thermionic emission. Resistivity was reduced to the order of 10-2-101 Ω cm by the thermally diffusion of indium into CdS films, without changing the type of carriers. The annealing temperature dependence of structural, optical and electrical properties of In-doped CdS films showed that the samples annealed at 350 °C and 400°C exhibited better results. © 2013 Elsevier B.V. All rights reserved.

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.

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.

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.

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.

Anwar H.,National University of Sciences and Technology | Maqsood A.,Center for Emerging science
Materials Research Bulletin | Year: 2014

A series of Co doped Mn-Zn ferrites compounds with the formula Mn 0.5Zn0.5 - xCoxFe2O4 (x = 0, 0.15, 0.25, 0.35 and 0.50) were successfully synthesized by polyethylene glycol-assisted coprecipitation and hydrothermal methods. The structural characterization of the samples was done using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). All the samples found to have cubic spinel structure. The average crystallite size of all nanoparticles were estimated using Scherrer's formula and found to lie between 10 and 25 ± 3 nm with small size distribution of particles prepared by hydrothermal method. The FTIR spectrum showed two absorption bands of tetrahedral and octahedral metal-oxygen sites. DC electrical resistivity varied from 4.12 × 107 to 8.32 × 1010 ohm cm with cobalt doping. The dielectric measurements were performed from 20 Hz to 3 MHz and from 1 MHz to 1 GHz frequency ranges. The value of dielectric constant (É′) varies from 15.54 to 106.25 (1 MHz) and 6.73-16.48 (1 GHz) for all the samples at room temperature. Impedance spectroscopy was carried out from 20 Hz to 3 MHz, at room temperature to study the grains and grain boundaries effect. © 2013 Elsevier Ltd. All rights reserved.

Rehan M.,Center for Advanced Studies in Engineering | Khan Z.H.,Center for Emerging science
2012 International Conference on Robotics and Artificial Intelligence, ICRAI 2012 | Year: 2012

This paper describes a robust formation control strategy for aerial refueling. Two types of control algorithms are designed and compared: first a conventional control system based on the Proportional Integral derivative (PID) controller is used for stability and control augmentation, and then a robust formation controller is designed to minimize the effect of disturbances and un-modeled dynamics. Both controllers are then compared for their performance under disturbance conditions. © 2012 IEEE.

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