Perigo E.A.,University of Luxembourg |
Gilbert E.P.,Australian Nuclear Science and Technology Organisation |
Metlov K.L.,Donetsk Institute for Physics |
Michels A.,University of Luxembourg
New Journal of Physics | Year: 2014
The pole-avoidance principle of magnetostatics results in an angular anisotropy of the magnetic neutron scattering cross section d∑M/Ω. For the case of a sintered Nd-Fe-B permanent magnet, we report the experimental observation of a 'spike' in d∑M/Ω along the forward direction. The spike implies the presence of long-wavelength magnetization fluctuations on a length scale of at least 60 nm. Using micromagnetic theory, it is shown that this type of angular anisotropy is the result of the presence of unavoidable magnetic poles in the bulk of the magnet and is related to q ≠ 0 the Fourier modes of the magnetostatic field. Thus, our observation proves the existence of such modes. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Danilenko I.,Donetsk Institute for Physics |
Konstantinova T.,Donetsk Institute for Physics |
Volkova G.,Donetsk Institute for Physics |
Burkhovetski V.,Donetsk Institute for Physics |
Glazunova V.,Donetsk Institute for Physics
Journal of Ceramic Science and Technology | Year: 2015
In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1-2wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders. © 2015 Göller Verlag.