The influence of applied stress and the composite geometry on impedance properties of composites containing ferromagnetic
microwires has been investigated. The results indicate that the application of tensile stress along the microwire axis
and the increase of composite thickness decreased the magneto-impedance (MI) ratio. The stress induced impedance (SI)
effect was enhanced with increasing composite thickness reflecting the role of the internal residual stresses. Theoretically
calculated matrix-wire interfacial stress from the magneto-impedance profiles is in good agreement with the value of the
applied effective tensile stress. This demonstrates a new route to probing the stress conditions of such composites.
Composites with multiple (bi-) interpenetrating phases are ideally placed to realise multi-functionality and certain multifunctional
and smart materials may be modeled as bi-continuous two-phase composites. This paper estimates the
mechanical properties of such materials using finite element analysis and homogenization. The effect of phase volume
fraction and contiguity on the properties is investigated for a range of microstructures with triply periodic minimal P
interfaces between the two phases. The results show that the properties of the composite depend on not only the overall
volume fraction but also the contiguity of the constituent phases.
Influence of Mn partial substitution for Fe on the magnetic and magnetoimpedance properties of Fe73.5-xMnxSi13.5B9Nb3Cu1 (x = 1, 3, and 5) nanocomposite ribbons were investigated. The results indicated that the Mn addition led to an improved exchange coupling between grains and hence in the magnetic softness. Consequently, the giant magnetoimpedance (GMI) effect was significantly enhanced in these nanocomposites. In the frequency range of 0.1-10 Mhz, the GMI ratio reached the highest values of 83%, 94%, and 130% at the frequency of 2 MHz for x = 1, 3, and 5 compositions, respectively. The corresponding field sensitivity of GMI reached the highest values of 6, 7, and 16 %/Oe, respectively. These indicate that Fe73.5-xMnxSi13.5B9Nb3Cu1 (x = 1, 3, and 5) nanocomposites are potential candidate materials for making GMI sensors.
Fe73-xAlxSi14B8.5Cu1Nb3.5 (x = 0, 2) nanocomposite materials consisting of a nanocrystalline phase in an amorphous matrix were obtained by annealing their precursor amorphous ribbons, which were prepared by the melt-spinning technique, at different temperatures ranging between 350°C and 650°C for 45 min in vacuum. Investigation on their magnetic and magnetoimpedance properties indicates that the Al-containing sample (x = 2) possesses superior magnetic softness and giant magnetoimpedance (GMI) effect over the Al-free counterpart. This can be likely ascribed to the increased magnetic permeability, decreased coercive force and decreased resistivity. The increased magnetic permeability is resulted from a reduction in magnetocrystalline anisotropy and saturation magnetostriction. The correlations between magnetic softness, electrical properties and GMI behaviour is discussed in the light of the skin effect model. These results indicate that the Al-containing Fe-based nanocomposite material can be used for GMI sensor applications.
Conference Committee Involvement (1)
Second International Conference on Smart Materials and Nanotechnology in Engineering
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