Kostas G. Efthimiadis

Nanostructured melt-spun Sm(Co-Fe-Zr-B)/sub 7.5/ alloys for high temperature magnets

In this paper, we report high coercivity in as spun and annealed ribbons of Cu free Sm(Co/sub bal/Fe/sub z/Zr/sub y/B/sub x/)/sub 7.5/ samples, with varying B, Zr and Fe content (x-0.005-0.06, y=0.02-0.16, z=0.08-0.3) were studied. Also TEM studies have been used to investigate microstructure and grain size distribution. Average grain size is 30-50 nm is as spun ribbons and 70 to 100 nm for annealed ribbons. The grain distribution is very uniform in the scale of nanometers for the samples with square loop. Very good loop squareness and a maximum energy product of (BH)/sub max/=10.7 MGOe has been obtained at RT for sample with composition Sm(Co/sub bal/Fe/sub 0.3/Zr/sub 0.02/B/sub 0.04/)/sub 7.5/ after annealing at 600/spl deg/C for 75 min.

Structural and Magnetic Properties of New Zr(Fe0.8Cu0.2)2 and Zr(Fe0.8Cu0.1Co0.1)2 Hydrogen Storage Materials

In this work we investigate the effect of hydrogen absorption/desorption at room temperature on the structural, magnetic and microstructural characteristics of Zr(Fe0.8Cu0.2)2 and Zr(Fe0.8Co0.1Cu0.1)2. Hydrating kinetics of the as cast bulk samples have been examined while in both samples an anomalous behavior at the absorption part of the P-C curve has been observed. Co doped sample absorbs higher hydrogen content at lower pressure. Crystal structure analysis has been performed by using the Rietveld method. Co free sample has saturation magnetization of 50.85 Am2/kg while Co doped sample has 54.04 Am2/kg at external field of 1.8 T. After hydrogenation the magnetization decreases. Thermomagnetic analysis in the range of 4.2 to 1100 K reveals that the Curie temperature of AB2 phases is in the range of 510 to 550 K. Scanning electron microscopy with energy dispersive x-ray spectroscopy was used in order to examine the composition and surface morphology of the bulk samples. The grain size reduces due to hydrogenation and this is attributed to the more hysteretic magnetization curve.