Abstract:The magnetic characteristics of FINEMET type glass-coated nanowires and submicron wires are investigated by taking into account the structural evolution induced by specific annealing all the way from a fully amorphous state to a nanocrystalline structure. The differences between the magnetic properties of these ultrathin wires and those of the thicker glass-coated microwires and "conventional" wires with similar structures have been emphasized and explained phenomenologically. The domain wall propagation in these novel nanowires and submicron wires, featuring a combination between an amorphous and a crystalline structure, has also been studied, given the recent interest in the preparation and investigation of new materials suitable for the development of domain wall logic applications.

The paper reports solution treatment (ST) and mechanical alloying (MA) effects on the structure and static/dynamic mechanical behaviour of PM-MA'ed FeMnSiCrNi shape memory alloys associated with the formation of thermally and stress-induced martensite. The specimens were subjected to tensile pre-straining, in order to stress induce martensite and their gauges were cut and prepared for X-ray diffraction (XRD) as well as for optical and scanning electron microscopy (SEM). XRD patterns allowed determining the presence of large amounts of α ′ -body centred cubic (bcc) besides ε-hexagonal close packed (hcp) martensite and γ-face centred cubic (fcc) austenite. The decrease in the amount of α ′ -bcc at specimens ST'ed at 1273 and 1373 K, with increasing pre-straining degree, was confirmed by XRD patterns and SEM micrographs. Dynamic mechanical analysis (DMA) was performed by strain sweeps (SS). The SS-DMA graphs displayed storage modulus plateaux which were associated with the formation of ε-hcp martensite.

We introduce a new type of magnetic particles (MPs) prepared by wet milling of superferromagnetic Fe-Cr-Nb-B precursor glassy ribbons for cancer treatment by magneto-mechanical actuation in low magnetic fields (1 ÷ 20 Oe). The rectangular shapes of MPs and the superferromagnetism of the glassy alloys of which are made the MPs induce important magnetic shape anisotropies which, in association with a large saturation magnetization, generate an improved torque in a rotating magnetic field, producing important damages on the cellular viability of MG-63 human osteosarcoma (HOS) cells. The specific parameters such as MPs concentration, frequency and intensity of the applied magnetic field, or the time of exposure have a strong influence on the cancer cells viability. The specific behavior of the Fe-Cr-Nb-B MPs offers them destructive effect even in low magnetic fields such as 10 Oe, and this characteristic allows the use of coils systems which provide large experimental spaces. The novel MPs are used for the magneto-mechanical actuation alone or in association with hyperthermia, but also can be transported to the tumor sites by means of stem cells carriers.

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Dielectric elastomer transducers (DETs), essentially consisting of highly deformable insulating films sandwiched between electrodes, are able to convert mechanical work in electrical energy and vice versa. Although still immature, these represent a simple and low-cost alternative to already known technologies for harvesting energy from renewable sources, in this case converting environmental mechanical energies (e.g., wave energy, human body movement) to an electrical one. However, the development of this new technology raises several challenges in terms of finding more efficient materials. For high conversion efficiencies, a dielectric film should meet certain properties such high breakdown strength and small mechanical hysteresis, while the electrodes should be compliant and able to keep conductivity along repeated large deformations. Regarding these aspects, two types of electrodes were successfully achieved, an ultrathin silver electrode of about 40 nm thickness and a PDMS-carbon black composite rubber electrode of about 30 μm thickness. Both electrodes were analyzed in terms of morphology and electrical and mechanical behaviors, as well as actuation response. The results indicate that the rubber electrode is more appropriate because it has proved to work perfectly in hundreds of cycles at large deformations (150%) without losing conductivity. On this basis, three types of capacitors with 120 mm diameters with coaxial electrodes of 60 mm diameters having one (DEG I), two (DEG II), and three (DEG III) active layers were built by a simple and efficient method using a commercial silicone (Elastosil) as the dielectric. The achieved arrays were tested in an energy-harvesting setup. At 200% strain and a bias voltage of 3 V μm −1 , DEG I produced 0.07 mJ, DEG II produced 0.2 mJ, and DEG III produced almost 1 mJ with an energy density of 1.1 kJ m −3 .