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2000 (1)
1996 (1)
1Author    G. A. Ennas, Falqur, G. Piccaluga, S. Solinas, D. Gatteschi, C. Sangregorio, A. BenedettiRequires cookie*
 Title    Properties of Nanocrystalline Nickel Particles in Ni-Si0 2 Composites  
 Abstract    Nickel-Silica nanocomposites with a nickel content equal to 10, 15, 20 wt% have been prepared by a sol-gel method starting from ethanolic solutions of tetraethoxysilane and nickel nitrate hex-ahydrate. After selation the samples were reduced in H-> flow at selected temperature (450 °C < T < 600 °C). The morphological, structural and magnetic properties were investigated by transmission electron microscopy (TEM), wide and small angle X-ray scattering (WAXS, SAXS), magnetic susceptibility in zero field cooled and field cooled mode (ZFC and FC), and magnetic hysteresis loop. Nanometric nickel particles are observed in all the investigated samples. TEM, WAXS and SAXS techniques indicate that the average nickel particle size grows slightly but almost regularly with the nickel concentration. TEM results moreover indicate that also the width of the particle size distribution, which can be simulated by log-normal functions, follows this trend. All the sample treated in hydrogen show superparamagnetic behaviour. The magnetisation falls to reach saturation up to highest measuring field of 70 kOe even at 3 K, while the observed coercivity H c is much higher than the theoretical bulk one. Some uncertainty in the complete interpretation of the sequence of magnetic measurements is attributed to a progressive oxidation of the samples when these are air exposed. 
  Reference    Z. Naturforsch. 55a, 581—588 (2000); received March 9 2000 
  Published    2000 
  Keywords    Nanocomposites, Nickel-Silica, X-ray Diffraction, TEM, Magnetic Properties 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0581.pdf 
 Identifier    ZNA-2000-55a-0581 
 Volume    55 
2Author    M. Sorescu, E. T. KnobbeRequires cookie*
 Title    Mössbauer Spectroscopy Evidence for Phase Selectivity in Excimer Laser Induced Amorphization of Thermally Annealed FeCoBSi Metallic Glass  
 Abstract    Pulsed excimer laser irradiation effects (/. = 308 nm, T = 10 ns, w = 3 J/cm 2 , N = 2 laser pulses/ spot, repetition rate 1 Hz) on the magnetic properties and phase composition of thermally annealed Fe 66 Co 18 B 15 Si 1 metallic glass have been studied by transmission and conversion electron Möss-bauer spectroscopy (CEMS). Radiation-driven surface modifications were examined by scanning electron microscopy (SEM). Excimer laser induced amorphization was observed in partially crystal-lized Fe 66 Co 18 B 15 Si 1 samples (7" A = 648 K, r A = 1 hour) and was found to be accompanied by the development of laser-induced magnetic anisotropy. In totally crystallized Fe^Co^B^Si! speci-mens (T A = 723 K, = 1 hour), the effect of excimer laser induced amorphization exhibited phase selectivity with respect to the crystalline components of the alloy system. When compared to bulk data, a different behavior of the surface magnetic texture and relative abundance of alloy phases was observed. The laser-induced phase transformation of thermally annealed Fe 66 Co 18 B 15 Si 1 specimens was shown to consist of partial amorphization and surface oxidation of the irradiated material. 
  Reference    Z. Naturforsch. 51a, 389—395 (1996); received February 3 1996 
  Published    1996 
  Keywords    Metallic glasses, Laser processing, Phase transformations, Magnetic properties, Möss-bauer spectroscopy 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0389.pdf 
 Identifier    ZNA-1996-51a-0389 
 Volume    51