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.
Effects of additional elements on the structure and magnetic properties of Nd2Fe14B/alpha-Fe-type nanocomposite magnets
The effects of a partial substitution of Mo, Ga, Si or Al, respectively, for Fe on the structure and magnetic properties of Nd-8.4 Fe-87.1 BJ(4.5) alloy prepared by mechanical alloying have been studied in detail. The addition of 1.1 at% Mo, Si or Ga results in the improvement of the intrinsic coercivity of the nanocomposite magnets. In contrast, the substitution of 1.1 at% Al is unfavourable for improving the magnetic properties. The optimum average grain size d(op) of the alpha-Fe is different for various element substitutions. It is found that in addition to the grain size of alpha-Fe. the grain size of Nd2Fe14B is another important factor in determining the magnetic properties of nanocomposite magnets. The main effects of these substitutions on the magnetic properties of the nanocomposite magnets originate Rom modifications of the grain sizes of the soft magnetic phase and the hard magnetic phase. The best magnetic properties: mu(0)H(c) = 0.4 T (4 kOe), J(r) = 1.07 T (10.7 kGs), (BH)(max) = 93.2 kJ m(-3) (11.7 MGOe), J(r)/J(s) = 0.68, are achieved for the Nd8.4Fe86Ga1.1B4.5 alloy.
The effect of continuous exposure to low frequency electric fields on three generations of mice: A pilot study
Mice were allowed to mate, gestate, deliver and rear their offspring for 3 successive generations while being continuously exposed to 60 Hz electric fields. Mice exposed to vertical electric fields exhibited decreased body weights at 35 days postpartum and increased mortality, rates for 3 successive generations. Mice exposed to horizontal electric fields exhibited decreased body weights for 2 successive generations.