Magnetic properties of mechanically milled Sm-Co permanent magnetic materials with the structure

The magnetic properties of Sm(Co,Fe,Cu,Zr) 7 compound with the TbCu 7 structure are studied for the mechanically milled samples. The coercivity could be varied, without affecting the saturation magnetization, from 44 kA/m for the micron sized particles to 280 kA/m by reducing the particle size to sub-micron size (600-900 nm) using high-energy ball milling. The enhancement in the coercivity is attributed to the particles approaching single domain size. The presence of dipolar coupling suggests that the grain sizes are well above the exchange length for the milled samples. The thermal measurements indicate that the compound with the TbCu 7 structure is not stable at high temperatures beyond 743 K

Glassy carbon surface effects on the electroreduction of aromatic carbonyl compounds. II Benzophenone

Results of the voltammetric study of benzophenone reduction in dimethylformamide and aqueous media on GCE are presented together with the comparative discussion of the data for mercury and other electrodes available in the literature. The formation and stability of anion radicals and dianions and their reactivity with protonating agents on GCE are similar to those on mercury electrodes. A new surface prewave noticed in aprotic and neutral aqueous solutions on GCE has not so far been reported on any other electrode. All experimental evidences support the view that this prewave is due to the surface protonation by the acidic functional groups on GCE. The surface protonation is found to be a slow time-dependent process requiring 3-4 minutes for completion. The surface concentration evaluated from the faradaic response of the surface process is found to be around 30% or even less if the surface roughness factor is considered,. The importance of this finding to the general concept of surface acidity effects on electrocatalysis is also emphasised.</jats:p