Eddy Yahya

XRD line‐broadening characteristics of M‐oxides (M = Mg,Mg‐Al, Y, Fe) nanoparticles produced by coprecipitation method

Simple coprecipitation method has been used to produce nanoparticles of MgO (magnesia), MgO⋅Al2O3 (spinel), Y2O3 (yttria) and Fe3O4 (ferrite). The raw materials were, in respective, magnesium powder, magnesium and aluminium powders, ytrria powder, and natural sand. The coprecipitation included the use of suitable acid and base to dissolve the powders or sand and to produce precipitates, as well as the use of water to wash and purify the precipitates, and drying at relatively low temperatures, namely lower than 100° C, followed by heating at 450° C, 750° C, 600° C and 200° C to produce magnesia, spinel, yttria and ferrite nanopowders, respectively. X‐ray diffractometry was used to characterise the purity and nanocrystallinity of the final powders. It was found qualitatively that the powders were of high purity. Further line‐broadening analysis using single‐line and Rietveld‐based softwares was performed to reveal the nanocrystallinity of the powders. Different line breadth values were found for the powders...

Epoxy Resin Matrix Nanocomposites with Core‐Shell Structure of NiZnFerrite/Ag and NiZnFerrite/PANi as Fillers for Microwave Absorber in Ka‐band

The core‐shell NiZnFerrite/Ag and NiZnFerrite/PANi (7:1 %wt) with epoxy resin forming a nanocomposite structure were synthesized by blending at 70 %vol content and introduced it into epoxy resin to be a microwave absorber. The phase and morphology characterization of the formation processes of NiZnFerrite/Ag and NiZnFerrite/PANi core‐shell structure were studied using X‐ray diffraction, transmission electron microscopy and scanning electron microscopy respectively. Microwave absorbing properties were investigated by reflectivity measurements in Ka‐band (18–26 GHz). The reflection losses were calculated based on the model of a single layered plane wave absorber backed by a perfect conductor. The composite epoxy resin‐NiZnFerrite/Ag shows matching frequency (fm1 = 20.7GHz and fm2 = 23.2GHz), maximum reflection loss (RLm1 = −20.8dB and RLm2 = −29.8dB) and bandwith (Δf1 = 18.6–21.7GHz and Δf2 = 21.7–25.0GHz ) Further, the composite epoxy resin‐NiZnFerrite/PANi shows matching frequency (fm1 = 20.7GHz and fm2 =...

Magnetic Properties of Ni0⋅5Zn0⋅5Fe2O4/Ag Core‐Shell Nanostructures

We report on magnetic properties of Ni0⋅5Zn0⋅5Fe2O4/Ag core‐shell nanostructures. Silver powders were covered with Ni0⋅5Zn0⋅5Fe2O4 spinel ferrites, forming a core‐shell nanostructure prepared by dry mixing at different ferrite/silver mass ratio (7:1, 5:1 and 3:1). The spinel ferrite nanoparticles (∼25 nm) have been synthesized from iron sand by coprecipitation method, whereas the pure silver powders have a typical particle size of ∼3 ▭m. The core‐shell nanostructural morphology has been observed by SEM, while the magnetic properties of this system were measured using vibrating sample magnetometer. It is shown that the increasing silver content in the core‐shell nanostructures has considerably decreased both the saturated magnetization (Ms) and remanent magnetization (Mr) from 50.67 to 39.73 emu/gr and from 12.82 to 10.36 emu/gr respectively, whilst it has not affected appreciably the coercive field (Hc).