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.
Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets
Abstract Magnetic nanocomposite SrFe 12 O 19 /Ni 0.7 Zn 0.3 Fe 2 O 4 powders with different weight fractions of the Ni 0.7 Zn 0.3 Fe 2 O 4 soft ferrite were synthesized by a combination of the sol–gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe 12 O 19 which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe 12 O 19 and 20 wt% Ni 0.7 Zn 0.3 Fe 2 O 4 . The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.
Prediction of net pressure on pressure equalized cavities
Abstract A numerical model has been developed for prediction of net pressure on pressure equalized cavities. The results based on this model show good agreement with those obtained from mock-up tests. Parametric studies verify that reductions in cladding load are possible, with proper design of curtain walls.