Local atomic structural changes on structural relaxation in a Pd82Si18 amorphous alloy

The structural changes effect on functional properties of ribbon shaped samples of the Fe81B13Si4C2 amorphous alloy during annealing process was investigated in this paper. Differential scanning calorimetry method has shown that this alloy crystallizes in one stage, in temperature range from room temperature up to 700?C. Structural relaxation process was investigated by sensitive dilatation method in nonisothermal and isothermal conditions. It has been shown that structural relaxation process occurs in two stages by measuring thermal expansion at constant temperatures of t1=420?C, t2 = 440?C and t3 = 460?C. The first stage is characterized by linear logarithmic dependence of thermal expansion upon time at constant temperature. The second stage of structural relaxation process is characterized by linear dependence of isothermal expansion upon the square root of process time. These results imply that the first stage of structural relaxation process is a rapid kinetic process, while the second stage of structural relaxation process is a slow diffusion process. The rate constants k11 = 2,27?10- 3 s-1, k12 = 2,79?10-3 s-1, k13 = 3,6?10-3 s-1, k21 = 0,67?10-4 s-1, k22 = 3,72?10-4 s-1, k23 = 21,53?10-4 s-1 and activation energies E1 = 48,64 kJ/mol and E2 = 366, 23 kJ/mol were determined for both stages of structural relaxation process. The distinct correlation between structural relaxation process and magnetic susceptibility relative change was determined by thermomagnetic measurements. It has been shown that magnetic susceptibility can be increased by up to 80%, by convenient annealings after structural relaxation process, at magnetic field intensity of 8 kA/m.

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THERMAL INVESTIGATION OF SiO2-Bi2O3 HEAVY METAL GLASSES

International Journal of Modern Physics B ◽

10.1142/s0217979205032073 ◽

2005 ◽

Vol 19 (20) ◽

pp. 3293-3299 ◽

Cited By ~ 2

Author(s):

V. SIMON ◽

M. TODEA ◽

S. SIMON

Keyword(s):

Thermal Analysis ◽

Heavy Metal ◽

Differential Thermal Analysis ◽

Silicon Dioxide ◽

Melting Temperature ◽

Structural Relaxation ◽

Structural Changes ◽

Glass Stability ◽

Thermal Investigation ◽

Metal Glasses

Structural changes induced by temperature rising in binary silico-bismuthate glasses are investigated by differential thermal analysis. Several exothermic peaks are recorded for all samples. Progressive substitution of Bi 2 O 3 by SiO 2 contributes to the structural relaxation of vitreous network and leads to diminishing of the melting temperature, even as SiO 2 content reaches 40 mol%. Glass stability is enhanced by addition of silicon dioxide.

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The effect of temperature and frequency on magnetic properties of the Fe81B13Si4C2 amorphous alloy

Science of Sintering ◽

10.2298/sos1102175d ◽

2011 ◽

Vol 43 (2) ◽

pp. 175-182 ◽

Cited By ~ 3

Author(s):

S. Djukic ◽

V. Maricic ◽

A. Kalezic-Glisovic ◽

L. Ribic-Zelenovic ◽

S. Randjic ◽

...

Keyword(s):

Signal Processing ◽

Magnetic Properties ◽

Amorphous Alloy ◽

Frequency Domain ◽

Magnetic Permeability ◽

Structural Relaxation ◽

Substantial Reduction ◽

Effect Of Temperature ◽

Influence Of Temperature ◽

Mean Frequency

In this study it was investigated influence of temperature and frequency on permeability, coercivity and power loses of Fe81B13Si4C2 amorphous alloy. Magnetic permeability measurements performed in nonisothermal and isothermal conditions was confirmed that efficient structural relaxation was occurred at temperature of 663 K. This process was performed in two steps, the first one is kinetic and the second one is diffuse. Activation energies of these processes are: Ea1 = 52.02 kJ/mol for kinetic and Ea2 = 106.9 kJ/mol for diffuse. It was shown that after annealing at 663 K coercivity decrease about 30% and therefore substantial reduction in power loses was attained. Investigated amorphous alloy satisfied the criteria for signal processing devices that work in mean frequency domain.

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The effect of structural changes during sintering on the electric and magnetic traits of the Ni96.7Mo3.3 alloy nanostructured powder

Science of Sintering ◽

10.2298/sos0902175r ◽

2009 ◽

Vol 41 (2) ◽

pp. 175-184 ◽

Cited By ~ 7

Author(s):

L. Ribic-Zelenovic ◽

M. Spasojevic ◽

A. Maricic ◽

M.M. Ristic

Keyword(s):

Electrical Resistivity ◽

Magnetic Permeability ◽

Structural Relaxation ◽

Crystalline Phase ◽

Structural Changes ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Fcc Lattice ◽

Lower Permeability ◽

Structural Powder

Ni96.7Mo3.3 powder was electrochemically obtained. An X-ray diffraction analysis determined that the powder consisted of a 20% amorphous and 80% crystalline phase. The crystalline phase consisted of a nanocrystalline solid nickel and molybdenum solution with a face-centred cubic (FCC) lattice with a high density of chaotically distributed dislocations and high microstrain value. The scanning electronic microscopy (SEM) showed that two particle structures were formed: larger cauliflower-like particles and smaller dendriteshaped ones. The thermal stability of the alloy was examined by differential scanning calorimetry (DSC) and by measuring the temperature dependence of the electrical resistivity and magnetic permeability. Structural powder relaxation was carried out in the temperature range of 450 K to 560 K causing considerable changes in the electrical resistivity and magnetic permeability. Upon structural relaxation, the magnetic permeability of the cooled alloy was about 80% higher than the magnetic permeability of the fresh powder. The crystallisation of the amorphous portion of the powder and crystalline grain increase occurred in the 630 K to 900 K temperature interval. Upon crystallisation of the amorphous phase and crystalline grain increase, the powder had about 50% lower magnetic permeability than the fresh powder and 3.6 times lower permeability than the powder where only structural relaxation took place.

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Origin of the enhanced structural and reorientational relaxation rates in the presence of relatively weak dc electric fields

Pure and Applied Chemistry ◽

10.1351/pac200476010215 ◽

2004 ◽

Vol 76 (1) ◽

pp. 215-221 ◽

Cited By ~ 5

Author(s):

A. Vegiri

Keyword(s):

Molecular Dynamics ◽

Electric Field ◽

Electric Fields ◽

Structural Relaxation ◽

Structural Changes ◽

Common Mechanism ◽

Weak Electric Field ◽

Water Molecules ◽

Relaxation Rates ◽

Dynamics Simulations

The origin of the dramatic increase of the reorientational and structural relaxation rates of single water molecules in clusters of size N = 16, 32, and 64 at T = 200 K, under the influence of an external, relatively weak electric field (~0.5 107 V/cm) is examined through molecular dynamics simulations. The observed effect is attributed not to any profound structural changes, but to the increase of the size of the molecular cage. The response of water to an electric field in this range shows many similarities with the dynamics of water under low pressure. By referring to simulations and experiments from the literature, we show that in both cases the observed effects are dictated by a common mechanism.

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