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  • The oxidation behaviour of Co and Dy modified NdFeB magnets
    Škulj, Irena, 1972-
    A study has been made of the influence of Co, Dy additions and minor additions of Zr and V on oxidation behaviour of NdFeB magnets. Various EM techniques have been used to characterise the sample as ... well as XRD and Mössbauer spectroscopy. The oxidation of these materials follows a parabolic rate, with oxidation taking place internally; i.e. oxygen diffuses into the magnet to form an internally oxidised layer and the reaction occurs at the interface between the unaffected magnet and the thick internally oxidised layer. Multilayered oxides are formed at the surface, with uniform thickness along the surface. The outer layer ([in leraliton]5[mu]m) consists predominantly of a mixture of heamatite ([alpha]-Fe[sub]{2}O[sub]3) with smaller quantities of Co[sub]{3}O[sub]4 in the Co containing compositions. The second layer is very thin ([in relation]100nm) and is composed of magnetite (Fe[sub]{3}O[sub]4) or Fe[sub]{3-x}Co[sub]{x}O[sub]4 (in Co containing compositions) as the main phase. The inner layer is the thickest layer, and varies in thickness with the high-temperature exposure value and duration. It consists of narrow (200-600nm) columnar grains of iron (solid solution with Co) containing a fine dispersion of neodymium oxide. The Co addition to a Nd[sub]{16}Fe[sub]{76}B[sub]8 alloy affects the oxidation rate, while the oxidation kinetics remain parabolic. It is believed that this change in oxidation rate is due to the microstructural differences between the internally oxidised layer and the layer formed on the surface of the Nd[sub]{16}Fe[sub]{76}B[sub]8 or Nd[sub]{16}Co[sub]{10}Fe[sub]{66.9}B[sub]7.1 material. In the second case, the layer formed provides fewer grain boundariesfor oxygen diffusion. The consequence of this is a slower oxidation of the material.
    Vrsta gradiva - disertacija ; neleposlovje za odrasle
    Založništvo in izdelava - Birmingham : [I. Škulj], December 2004
    Jezik - angleški
    COBISS.SI-ID - 422314

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