Crystallization, morphology and magnetic properties of melt-spun (Nd,Pr,Dy)/sub 2/(Fe,Co,Mo)/sub 14/B//spl alpha/-Fe nanocomposites
Crystallization, phase evolution, nanostructure, exchange coupling, and hard magnetic properties of melt-spun Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ and Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ nanocomposites have been studied. All the Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ alloys annealed for 30 s at 565/spl deg/C or above contain nanostructured /spl alpha/-Fe and Nd/sub 2/Fe/sub 14/B-type (2:14:1) phases, whereas Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ alloys annealed at 600/spl deg/C or below are mainly composed of /spl alpha/-Fe and a metastable 1:7 phase. A small amount of 2:14:1 phase forms after annealing at 600/spl deg/C. When annealed at 640/spl deg/C or above, the hard phase in Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ alloys is the 2:14:1 phase rather than the 1:7 phase. The differences in magnetic properties of the Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 85/B/sub 6/ and Nd/sub 2.4/Pr/sub 5.6/Dy/sub 1/Fe/sub 78/Co/sub 6/Mo/sub 1/B/sub 6/ nanocomposites at different anneal temperatures result from the different nanostructures, exchange coupling and phase components present in the alloys, in particular from the different amount of the 1:7 phase.
Exploring the annealing temperature impacting on the magnetic coupling of nanometer soft grain and microstructure hard grain nanocomposites
Abstract Nanocomposites of 70% MgFe2O4 and 30% BaFe12O19 have been prepared by the mechano-chemical coprecipitation method. The prepared samples were annealed at different temperatures (400, 600, 800, and 1000 °C). The thermal gravimetric analysis (TGA) measurements of the as prepared samples has detected three weight losses attributed to evaporation, the decomposition of citric acid and nitrate combustion and the crystal transformation. The crystal growth of the soft phase has been proved by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) measurements. The bonds have been detected by FT-IR measurements and are assigned to the two ferrite phases constituting the nanocomposites, which means that there are no intruder phases that have been detected. The vibrating sample magnetometer measurements (VSM) have displayed a gradually increasing of the saturation magnetization (Ms) with the annealing temperature, while the coercivity (Hc) and remnance (Mr) have exhibited a maximum value at the annealing temperature 600 °C. The ferromagnetic resonance (FMR) and VSM measurements have clarified the magnetic ordering changing inside the nanocomposites at the system transformation from the as prepared amorphous/hexagonal phase to the spinel/hexagonal phase with increasing annealing temperature. The porosity (P), the anisotropy (K) and the line width (ΔH) calculated parameters have been used to study the agreement between the FMR and VSM magnetic measurements.
Satellites and Education in Australia--Learning from International Experience
Australia's domestic satellite service, AUSSAT, began operating in August 1985 and will be fully operational with the launch of the third satellite in late 1986. An examination of international educational satellite systems relevant to primary and secondary education in Australia is presented. Information collected and analysed is intended to inform decision-making.