Minia University

About: Minia University is a education organization based out in Minya, Egypt. It is known for research contribution in the topics: Population & Medicine. The organization has 4967 authors who have published 8986 publications receiving 108384 citations.

Influence of temperature on the photodegradation process using Ag-doped TiO2 nanostructures: Negative impact with the nanofibers

Abstract: In this study, the influence of the temperature on the photodegradation process using Ag-doped TiO2 nanostructures was investigated. Two morphologies were used; nanoparticles and nanofibers. The nanofibers were synthesized by electrospinning of a sol–gel consisting of titanium isopropoxide, silver nitrate and poly(vinyl acetate). The silver nitrate amount was changed to produce nanofibers having different silver contents. Typically, sol–gels containing 0.5, 1.0, 1.5, 2.0 and 2.5 wt% silver nitrate were utilized. Calcination of the electrospun mats at 700 °C led to produce well morphology Ag-doped TiO2 nanofibers for all formulations. The nanoparticles were prepared from the same sol–gels, however, instead of spinning the gels were dried, grinded and sintered at 700 °C. Photodegradation under UV irradiation for the rhodamine B at 5, 15, 25, 45 and 55 °C were performed. For the nanoparticles, increasing the temperature has positive impact as the best degradation was obtained at 55 °C. In contrast to the known influence of the temperature on the chemical reactions, in case of the nanofibrous morphology, the temperature has negative impact as the experimental work indicated that the optimum temperature is 25 °C. The observed strange effect of the temperature in case of the nanofibrous morphology indicates instant degradation of the dye molecules in the active zones surrounding the nanofibers. Therefore, the increase of temperature results in increase the kinetic energy of the dye molecules so the molecules escape from the active thin film surrounding the photocatalyst. Overall, this study shows that the nanofibrous morphology strongly enhances the surface activity of the photocatalyst which generates negative influence of the temperature.

A compact double-sided MIMO antenna with an improved isolation for UWB applications

Abstract: This paper presents compact size 4 × 4 cm 2 MIMO antenna for UWB applications. The proposed antenna consists of four symmetric circular elements printed on low cost FR4 substrate with partial slotted ground plane. The two sides of the substrate are symmetric and each side is consisting of two radiators with the partial ground planes associated to the two other elements mounted on the other side. The two elements of the front side are orthogonal to the two other elements of the back side in order to increase the isolation between elements. For further reduction in the mutual coupling between elements, decoupling structures are presented in the top and bottom layers of the substrate. The simulated and measured results are investigated to study the effectiveness of the MIMO-UWB antenna. The results demonstrate the satisfactory performance of MIMO-UWB antenna, which has a return loss less than −10 dB from approximately 3.1 GHz to more than 11 GHz with an insertion loss lower than −20 dB through the achieved frequency band, and a correlation less than 0.002. Moreover, the proposed MIMO model exhibits a nearly omni-directional radiation pattern with almost constant gain of average value 3.28 dBi.

Cobalt nanofibers encapsulated in a graphite shell by an electrospinning process

Abstract: As cobalt is an important ferromagnetic material and the nanofibrous shape greatly improves the magnetic properties, we are introducing cobalt nanofibers encapsulated in graphite shell to gain the advantages of the nanofibrous shape as well as to produce protected materials. An electrospun nanofiber mat consisting of cobalt acetate and poly(vinyl alcohol) has been calcined in argon atmosphere at 850 °C. Calcination of cobalt acetate in an inert atmosphere leads to the production of pure cobalt which strongly enhanced graphitization of the utilized polymer to form a graphite shell. Physicochemical characterization analyses indicated that the final product was pure cobalt nanofibers enveloped in a 10 nm thick graphite shell. The graphite shell did not affect the magnetic properties of the synthesized graphite-encapsulated cobalt nanofibers compared with the bare ones which reveal preeminent magnetic characteristics; moreover the shell modifies some of these properties to be temperature independent.