Kinematic Viscosity and Electrical Resistivity of a Multicomponent Melt due to Liquid–Liquid Structure Transition

2021 ◽  
Vol 904 ◽  
pp. 111-116
Author(s):  
Vladimir Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Viktor V. Konashkov ◽  
Yekaterina A. Kochetkova
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Electrical Resistance ◽  
Cluster Size ◽  
Kinematic Viscosity ◽  
Arrhenius Plot ◽  
Liquid Structure ◽  
Structure Transition ◽  
Temperature Range ◽  
Temperature Dependences

We investigated the kinematic viscosity and electrical resistivity of the multicomponent Fe74Cu1Nb1.5Mo1.5B8.5Si13.5 melt during three heating–cooling cycles. The temperature dependence of kinematic viscosity and electrical resistivity have the anomalous zones in the same temperature range and they are associated with the liquid–liquid structure transition (LLST). The anomalies were explained by changes in the activation energy and the cluster size. As the cluster size decreases, the activation energy decreases, but the viscosity and electrical resistance increase. LLST begins with the cluster dissolution, and as a result, the Arrhenius plot becomes nonlinear in the transition temperature range. After three cycles of heating–cooling, the temperature dependences of the kinematic viscosity and electrical resistance did not qualitatively change, and this allows us to conclude that LLST is thermoreversible. With an increase in the number of thermal cycles, the activation energy of viscous flow decreases, as well as the onset temperature and temperature range of LLST.

Viscosity of Liquid Nanocrystalline Alloys

2021 ◽  
Vol 880 ◽  
pp. 35-41
Author(s):  
V.S. Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Nadezhda P. Tsepeleva
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Viscous Flow ◽  
Critical Point ◽  
Free Volume ◽  
Electrical Resistance ◽  
Kinematic Viscosity ◽  
Chemical Compositions ◽  
Cooling Stage ◽  
Temperature Dependences

Temperature dependences of the kinematic viscosity, density, and electrical resistivity of Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 multicomponent melts have been studied. We found different behavior of the temperature dependences of viscosity near the critical point Tk = 1760 K during heating, which is associated with different chemical compositions of the clusters in the melt. In the cooling stage, the activation energy of the viscous flow for these two melts is the same and equal to 43 kJ·mol-1. At a temperature of 1720 K, the relative free volume is 5.1 and 7.5 % of the total melt volume for Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 respectively. In the cooling stage, the electrical resistance of melt is higher than at the heating stage.

scholarly journals Kinematic Viscosity ofMulticomponent FeCuNbSiB-BasedMelts

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1042
Author(s):  
Yuri N. Starodubtsev ◽  
Vladimir S. Tsepelev ◽  
Nadezhda P. Tsepeleva
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Viscous Flow ◽  
Cluster Size ◽  
Kinematic Viscosity ◽  
Cluster Structure ◽  
Liquid Structure ◽  
Logarithmic Scale ◽  
Structure Transition ◽  
Exponential Factor

The work investigated the temperature dependences of the kinematic viscosity for multicomponent melts of nanocrystalline soft magnetic alloys. It is shown that there is a linear relationship between the reduced activation energy of viscous flow Ea·(RT)−1 and the pre-exponential factor ν0. This ratio is universal for all quantities, the temperature dependence of which is expressed by the Arrhenius equation. It is shown that the activation energy of a viscous flow is linearly related to the cluster size on a natural logarithmic scale, and the melt viscosity increases with decreasing cluster size. The change in the Arrhenius plot in the anomalous zone on the temperature dependence of viscosity can be interpreted as a liquid–liquid structure transition, which begins with the disintegration of clusters and ends with the formation of a new cluster structure.

Anomalous Temperature Dependences of Kinematic Viscosity in a Multicomponent Metal Melts

2021 ◽  
Vol 902 ◽  
pp. 3-8
Author(s):  
Vladimir Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Yekaterina A. Kochetkova
Keyword(s):  
Activation Energy ◽  
Cluster Size ◽  
Kinematic Viscosity ◽  
Heating Temperature ◽  
State Theory ◽  
Melt Structure ◽  
Subsequent Formation ◽  
Natural Logarithm ◽  
Temperature Dependences ◽  
Maximum Heating Temperature

The temperature dependence of the kinematic viscosity was determined in the Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 melt, which has an anomaly in the temperature range 1700–1900 K. The cluster sizes participating in the viscous flow were calculated using the transition state theory. It is shown that the activation energy Ea is directly proportional to the natural logarithm of the cluster size d, and the melt viscosity decreases with increasing cluster size. In the anomalous region at heating, the activation energy first decreases and then increases. This behavior was associated with the cluster dissolution and the subsequent formation of new clusters with a different size and chemical composition. Upon cooling, the viscosity corresponds to the melt structure formed at the maximum heating temperature.

scholarly journals Туннельная проводимость и туннельное магнитосопротивление пленок Fe-SiO: корреляция магнитотранспортных и магнитных свойств

2019 ◽  
Vol 61 (7) ◽  
pp. 1262
Author(s):  
Д.А. Балаев ◽  
А.Д. Балаев
Keyword(s):  
Activation Energy ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
Magnetic Method ◽  
Tunnel Mechanism ◽  
Giant Magnetoresistive Effect ◽  
Temperature Dependences ◽  
Magnetoresistive Effect ◽  
Dielectric Region ◽  
Good Agreement

The paper presents the results of a study of the electrical properties of a system of nanogranular amorphous Fe-SiO films with a SiO concentration from 0 to 92 Vol.%. For samples with a low SiO content, metallic conductivity takes place. With an increase of the dielectric content, a concentration transition of conduction from the metallic regime to the tunnel regime at a dielectric concentration x  0.6 is observed. At the same concentration, a transition ferromagnet - superparamagnet occurs, which was previously investigated by the magnetic method. For compositions corresponding to the dielectric region, the temperature dependences of the electrical resistance (T) follow the law (T) ~ exp(2(С/kT)1/2), which is typical for the tunnel mechanism of conductivity. Estimation of the sizes of metal granules from the values of the tunneling-activation energy C showed a good agreement with the sizes obtained earlier from the analysis of magnetic properties. In the dielectric range of the compositions, a giant magnetoresistive effect was obtained, reaching 25% at low temperatures.

ELECTRICAL RESISTIVITY OF COBALT-BORON LQA ALLOYS

1995 ◽  
Vol 09 (23) ◽  
pp. 1535-1538 ◽  
Author(s):  
S. M. M. R. NAQVI ◽  
S. DABIR H. RIZVI ◽  
SAJIDA JAMILA ◽  
SHABANA RIZVI ◽  
S. MOHSIN RAZA ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Amorphous Alloys ◽  
Amorphous Matrix ◽  
Arrhenius Plot ◽  
Amorphous Material ◽  
Activation Energies ◽  
Dangling Bonds ◽  
Crystalline Phases ◽  
Temperature Range

Activation energies determined from Arrhenius plot for cobalt-boron liquid quenched amorphous alloys in the temperature range 40 K < T < 300 K , suggest vacancy and interstitial formation to nucleate crystalline phases in an amorphous matrix preferably at sites where dangling bonds are present. Nucleation of crystallites with preferential tetragonal or orthorhombic structures is a self-evolving process due to catalytic presence of dangling bonds in an amorphous material and that the occurrence of negative activation energies support this evidence.

scholarly journals VISCOSITY AND ELECTRICAL RESISTIVITY OF LIQUID CuNiAl, CuNiAlCo, CuNiAlCoFe ALLOYS OF EQUIATOMIC COMPOSITIONS

2019 ◽  
Vol 25 (4) ◽  
pp. 259
Author(s):  
Olga Chikova ◽  
Vladimir Tsepelev ◽  
Vladimir V’yukhin ◽  
Kseniya Shmakovа ◽  
Vadim Il’in
Keyword(s):  
Electrical Resistivity ◽  
Structural State ◽  
Kinematic Viscosity ◽  
Reaction Rates ◽  
Field Method ◽  
Rotating Magnetic Field ◽  
Atomic Scale ◽  
High Entropy ◽  
Temperature Dependences ◽  
Entropy Of Activation

<p class="AMSmaintext1">The kinematic viscosity and electrical resistivity of equiatomic liquid alloys CuNiAl, CuNiAlCo, CuNiAlCoFe were measured during heating of the sample to 2070 K and subsequent cooling. The kinematic viscosity was measured using the damped torsional vibrations of a crucible with a melt. The measuring results are discussed within the theory of absolute reaction rates. The entropy of activation of viscous flow (characteristic of the structural state of the melt) was are determined by analyzing the temperature dependences of kinematic viscosity. The electrical resistivity was measured was using the rotating magnetic field method. The temperature coefficient of resistivity (characteristic of the structural state of the melt) was are determined. The measuring results interpreted using the Nagel-Tauc model. We considerCuNiAl, CuNiAlCo, CuNiAlCoFe alloysof equiatomic compositions as the multi-principal element alloys (MPEAs),  the complex concentrated alloys (CCAs), the high-entropy alloys (HEAs). It based on the available microgeterogenity concept the measuring results of the vickosity and the resistivity are discussed. We were looking for temperatureis of the heating a melt for destroy of microheterogeneity and mixing components on an atomic scale T*. The temperature T*=1800 K could be determined only  for alloy CuNiAl of equiatomic composition. We have made the assumption that the heating of uid alloy CuNiAl the more 1800K in subsequent crystallization even at relatively low speeds will provide of more homogeneous structure volumetric ingots.</p>

scholarly journals Structure and electrical properties of zinc oxide base iron doped ceramics

2018 ◽  
Vol 4 (3) ◽  
pp. 87-95
Author(s):  
Alexey V. Pashkevich ◽  
Aleksandr K. Fedotov ◽  
Yuliya V. Kasyuk ◽  
Liudmila A. Bliznyuk ◽  
Julia A. Fedotova ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Electrical Resistivity ◽  
Electrical Properties ◽  
Resonance Spectroscopy ◽  
Two Stage ◽  
Wurtzite Phase ◽  
X Ray ◽  
Temperature Dependences ◽  
Stage Synthesis

The search for new economically advantageous technologies of new zinc oxide based composite ceramic materials and the study of their structure and properties attract special attention today. These ceramics have a number of advantages as compared with materials prepared by more expensive technologies, due to the possibility to fabricate items having different shapes and sizes and particularly to vary their morphology, structure and phase composition. This allows controlling their functional properties by varying the powder particle size in charge, the temperatures, durations and atmospheres of synthesis and heat treatment, and the types of doping impurities in the ceramics. The structure and electrical properties of (FexOy)10(ZnO)90 ceramics (0 ≤ x ≤ 3; 1 ≤ y ≤ 4) synthesized in air using single- and two-stage synthesis methods have been studied. FeO, α-Fe2O3 and Fe3O4 powders or (α-Fe2O3 + FeO) mixture have been used for ZnO doping. X-ray diffraction, gamma-ray resonance spectroscopy and Raman spectroscopy data suggest that at average iron concentrations of 1–3 at.% the ceramic specimens contain at least three phases: the Zn1-δFeδO solid solution with a wurtzite structure, the ZnFe2O4 ferrite phase with a spinel structure and FexOy residual iron oxides which were used as doping impurities. Scanning electron microscopy and energy dispersion X-ray analysis have shown that the wurtzite phase grain size in the ceramic specimens decreases from several decades of microns for single-stage synthesis to submicron sizes for two- stage synthesis. We show that iron addition to ZnO induces a compression of the wurtzite phase crystal lattice, the compression of lattice magnitude being proportional to the oxygen content in the FexOy iron oxide doping agent. The temperature dependences of the electrical resistivity suggest that deep donor centers with an activation energy of about 0.37 eV are formed in the Zn1-δFeδO wurtzite phase. The temperature dependences of the electrical resistivity of electrons for undoped ZnO in the 6–300 K range and for doped (FeO)10(ZnO)90 ceramic synthesized in one stage exhibit a variable activation energy below 50 K which indicates a heavily disordered structure.

Semiconducting Molybdenum Pyrochlores for high Temperature Applications

1998 ◽  
Vol 512 ◽  
Author(s):  
V. Ponnambalam ◽  
U. V. Varadaraju
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Low Temperature ◽  
Solid Solutions ◽  
Power Factor ◽  
Charge Carriers ◽  
Temperature Range ◽  
Maximum Power Factor ◽  
Increasing Temperature

ABSTRACTThe solid solutions (Y1-xYbx)2Mo2O7 were prepared and the systematic changes in the electrical resistivity (ρ=l/σ), thermopower (S) and power factor (S2σ) have been studied in the temperature range 300–900 K. The lattice parameters ‘a’ and ‘c’ are smaller for higher Yb3+ content phases due to smaller Yb3+ radius and a small tetragonality is observed for all the phases. Semiconducting behaviour is seen for all compositions with systematic increase in activation energy with increasing Yb content. All compositions show negative thermopower indicating electrons are the majority charge carriers in the temperature range of measurements. The calculated power factor values S2σ increase with increasing temperature in the low temperature region and a maximum power factor of ∼0.76×10−7 Wcm−1K−2 is observed at 650K.

scholarly journals Structure and electric properties of zink oxide−based ceramics doped with iron

2019 ◽  
Vol 21 (3) ◽  
pp. 133-145
Author(s):  
A. V. Pashkevich ◽  
A. K. Fedotov ◽  
Yu. V. Kasyuk ◽  
L. A. Bliznyuk ◽  
J. A. Fedotova ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Iron Oxides ◽  
Synthesis Method ◽  
Resonance Spectroscopy ◽  
Wurtzite Phase ◽  
X Ray ◽  
As Doping ◽  
Temperature Dependences ◽  
One Step

The structure and electrical properties of (FexOy)10 (ZnO)90 ceramics (0 ≤ x ≤ 3; 1 ≤ y ≤ 4) synthesized in air by one− and two−stage method were studied. To dope ZnO, powders of FeO, α−Fe2O3, and Fe3O4 or a mixture (α−Fe2O3 + FeO) were used. On the basis of X−ray diffraction analysis, gamma−resonance spectroscopy and Raman spectroscopy, it was established that at fixed average iron concentrations of 1—3 at.% in ceramic samples, at least three phases are formed: solid solution Zn1−δFeδO with wurtzite structure and residual iron oxides FexOy, used as doping agents. Scanning electron microscopy and energy−dispersive X−ray analysis have shown that, in the studied ceramics, the grain sizes of the wurtzite phase decreased from several tens of micrometers using one−step synthesis to the submicron level for the case of two−step synthesis. It was found that the incorporation of iron into ZnO leads to a contraction of the crystal lattice in the wurtzite phase and the stronger, the higher the proportion of oxygen in the doping iron oxides FexOy. The study of the temperature dependences of the electrical resistivity have shown that deep donor centers with an activation energy of about 0.35 eV are formed in the wurtzite phase Zn1−δFeδO. The temperature dependences of the electrical resistivity in the undoped ZnO in the temperature range of 6—300 K and in the doped ceramics (FexOy)10(ZnO)90, obtained by the one−step synthesis method, at temperatures below 50 K, are characterized by a variable activation energy, which indicates a strong disordering of their structure.

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