Mohd Shamsul Ezzad Shafie

MICROWAVE ABSORPTION CHARACTERISTICS OF SOME FERRITE- FILLED POLYMER COMPOSITES

Prior to their use for microwave absorption, different compositions of NixZn1-xFe2O4 (x = 0.5, 0.6, 0.7 and 0.8) were prepared via mechanical alloying and sintering. X-ray diffractometry (XRD) was used to investigate the crystalline phase formation. Scanning transmission electron microscopy (STEM) and field emission electron microscopy (FeSEM) were used to investigate the particle size and surface morphology respectively. The complex-permeability components, μʹ and μʺ, were also measured using an Agilent 4291B material analyzer from 1 MHz to 1 GHz. From the XRD results it is shown that at 900oC the full phase of nickel zinc ferrite was formed. The μʺ values suggest that the ferrite sample can absorb well microwave energy for frequencies 1 MHz to 1 GHz and higher. This is proved by microwave absorption measurements carried out up to 12 GHz.Keywords: NiZn-ferrite, microwave absorption, magnetic materials

Influence of Annealing Temperature on the Magnetic Properties of Rapidly Quenched (Nd,Pr)2-(Fe,Co,Ga,Ti,C)14B/α-Fe Nanocomposite Ribbons

The effects of different heat treatment temperatures on the structure and magnetic properties of Nd-Fe-B nanocomposite permanent magnetic alloys with nominal composition of Nd9.4Pr0.6Fe74.5Co6B6Ga0.5Ti1.5C1.5 have been investigated. The most practical method to produce nanostructured metallic materials is rapid solidification. Melt spinning with constant wheel speed of  m/s was employed to produce ribbons. As-spun ribbons were examined by using differential scanning calorimetry (DSC) and X-ray diffractometer (XRD) with Cu-kα radiation. The ribbons were annealed at different temperatures in order to extract the best magnetic properties. The XRD and electron microscopy technique results confirm that grains are in the size of less than 50 nm. In addition, optimum magnetic properties were obtained at 700°C annealed temperature.