scholarly journals Influence of High Conductive Magnetite Impurity on the Electrical Conductivity of Dry Olivine Aggregates at High Temperature and High Pressure

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 44 ◽  
Author(s):  
Lidong Dai ◽  
Haiying Hu ◽  
Wenqing Sun ◽  
Heping Li ◽  
Changcai Liu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
High Pressure ◽  
Percolation Threshold ◽  
Atmospheric Pressure ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Frequency Range ◽  
Arrhenius Relation ◽  
Conductivity Anomalies

The electrical conductivity of dry sintered olivine aggregates with various contents of magnetite (0, 3, 5, 7, 10, 20, and 100 vol. %) was measured at temperatures of 873–1273 K and a pressure of 2.0 GPa within a frequency range of 0.1–106 Hz. The changes of the electrical conductivity of the samples with temperature followed an Arrhenius relation. The electrical conductivity of the sintered olivine aggregates increased as the magnetite-bearing content increased, and the activation enthalpy decreased, accordingly. When the content of interconnected magnetite was higher than the percolation threshold (~5 vol. %), the electrical conductivity of the samples was markedly enhanced. As the pressure increased from 1.0 to 3.0 GPa, the electrical conductivity of the magnetite-free olivine aggregates decreased, whereas the electrical conductivity of the 5 vol. % magnetite-bearing sample increased. Furthermore, the activation energy and activation volume of the 5 vol. % magnetite-bearing sintered olivine aggregates at atmospheric pressure were calculated to be 0.16 ± 0.04 eV and −1.50 ± 0.04 cm3/mole respectively. Due to the high value of percolation threshold (~5 vol. %) in the magnetite impurity sample, our present results suggest that regional high conductivity anomalies in the deep Earth’s interior cannot be explained by the presence of the interconnected magnetite-bearing olivine aggregates.

scholarly journals Dependence of Electrical Properties on Frequency and Temperature for Novel Cyclopentenone Derivatives

2020 ◽  
Vol 1 (1) ◽  
pp. 13-25
Author(s):  
Salama A. H.
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Electrical Properties ◽  
Arrhenius Equation ◽  
Charge Carriers ◽  
Frequency Range ◽  
Ac Electrical Conductivity ◽  
Dc Electrical Conductivity ◽  
Arrhenius Relation

Electrical properties of some new cyclopentenone derivatives have been studied. The structures of prepared samples were characterized by (UV), (XRD) and (SEM). The dependence of electrical properties such as σdc , σac , ɛ' and ɛ'' on frequency and temperature were studied at frequency range from 50 Hz to 5 MHz and the temperature range from 25oC to 140oC. It was found that, ɛ' decreased with increasing frequency while it increases with increasing temperatures within the used ranges. Moreover, dielectric constant is structural dependent which is obvious from the variation of dielectric constant for each sample. Ac-electrical conductivity increased with increasing frequency which was attributed to the polarization of the charge carriers. The temperature dependence of dc-electrical conductivity show typical Arrhenius relation for the three prepared samples. The activation energy calculated from Arrhenius equation and the results are discussed in detailed.

The electrical conductivity of dry polycrystalline olivine compacts at high temperatures and pressures

2010 ◽  
Vol 74 (5) ◽  
pp. 849-857 ◽  
Author(s):  
Lidong Dai ◽  
Heping Li ◽  
Chunhai Li ◽  
Haiying Hu ◽  
Shuangming Shan
Keyword(s):  
Electrical Conductivity ◽  
Oxygen Fugacity ◽  
Conduction Mechanism ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Small Polaron ◽  
Frequency Range ◽  
Exponential Factor ◽  
Exponential Factors ◽  
The Relationship

AbstractThe electrical conductivity of dry polycrystalline olivine compacts (hot-pressed and sintered pellets) was measured at pressures of 1.0–4.0 GPa, at temperatures of 1073–1423 K, and at different oxygen fugacities via the use of a YJ-3000t multi-anvil press. Oxygen fugacity was controlled successfully by means of five solid buffers: Fe3O4-Fe2O3, Ni-NiO, Fe-Fe3O4, Fe-FeO and Mo-MoO2. Within the selected frequency range of 102–106 Hz, the experimental results indicate that the grain interior conduction mechanism is characterized by a semi-circular curve on an impedance diagram. As a function of increasing pressure, the electrical conductivity of polycrystalline olivine compacts decreases, whereas the activation enthalpy and the temperature-independent pre-exponential factors increase slightly. The activation energy and activation volume of polycrystalline olivine compacts were determined to be 141.02±2.53 kJ/mol and 0.25±0.05 cm3/mol, respectively. At a pressure of 4.0 GPa, electrical conductivity was observed to increase as a function of increasing oxygen fugacity, and the relationship between electrical conductivity and oxygen fugacity can be described as log10 (σ) = (2.47±0.085) + (0.096±0.023)×log10fO2 + (–0.55±0.011)/T, which presents the exponential factor q (˜0.096). Our observations demonstrate that the primary conduction mechanism for polycrystalline olivine compacts is a small polaron.

Electrical conductivity studies on silica phases and the effects of phase transformation

2019 ◽  
Vol 104 (12) ◽  
pp. 1800-1805
Author(s):  
George M. Amulele ◽  
Anthony W. Lanati ◽  
Simon M. Clark
Keyword(s):  
Electrical Conductivity ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Hydrogen Charge ◽  
Charge Compensation ◽  
Composition Analysis ◽  
Conductivity Measurements ◽  
Pressure System ◽  
Electrical Conductivities ◽  
Silica Phases

Abstract Starting with the same sample, the electrical conductivities of quartz and coesite have been measured at pressures of 1, 6, and 8.7 GPa, respectively, over a temperature range of 373–1273 K in a multi-anvil high-pressure system. Results indicate that the electrical conductivity in quartz increases with pressure as well as when the phase change from quartz to coesite occurs, while the activation enthalpy decreases with increasing pressure. Activation enthalpies of 0.89, 0.56, and 0.46 eV, were determined at 1, 6, and 8.7 GPa, respectively, giving an activation volume of –0.052 ± 0.006 cm3/mol. FTIR and composition analysis indicate that the electrical conductivities in silica polymorphs is controlled by substitution of silicon by aluminum with hydrogen charge compensation. Comparing with electrical conductivity measurements in stishovite, reported by Yoshino et al. (2014), our results fall within the aluminum and water content extremes measured in stishovite at 12 GPa. The resulting electrical conductivity model is mapped over the magnetotelluric profile obtained through the tectonically stable Northern Australian Craton. Given their relative abundances, these results imply potentially high electrical conductivities in the crust and mantle from contributions of silica polymorphs. The main results of this paper are as follows:The electrical conductivity of silica polymorphs is determined by impedance spectroscopy up to 8.7 GPa.The activation enthalpy decreases with increasing pressure indicating a negative activation volume across the silica polymorphs.The electrical conductivity results are consistent with measurements observed in stishovite at 12 GPa.

High Pressure Dielectric Studies of 8CB in the Isotropic, Nematic, and Smectic A Phases

1999 ◽  
Vol 54 (5) ◽  
pp. 275-280 ◽  
Author(s):  
Phineus Markwick ◽  
Stanislaw Urban ◽  
Albert Würflinger
Keyword(s):  
Activation Energy ◽  
Complex Permittivity ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Retardation Factor ◽  
Smectic A ◽  
Parallel Component ◽  
Temperature And Pressure

The static and complex permittivity of 4-n-octyl-4'-cyanobiphenyl (8CB) has been measured for the isotropic, nematic and smectic A phases as functions of temperature and pressure. The ranges of 297 - 361 K, 0.1 - 220 MPa, and 0.1 - 13 MHz, were covered. Only the parallel component of the complex permittivity, ɛ*( f ) = ɛ' ( f ) - iɛ"(f), was measured. The relaxation times T||(p, T) as well as Tis(p, T) were analysed at constant temperature, pressure and volumes yielding the activation volume, Δ ≠V(T), activation enthalpy Δ≠H(p), and activation energy Δ≠U(V), respectively. All activation parameters calculated for the smectic A phase of 8CB are smaller than those obtained for the nematic phase. The activation energy constitutes approximately half of the activation enthalpy value in all three phases studied. The pressure study allowed to calculate the pressure dependence of the retardation factor g|| (p, T), from which the nematic potential q(p,T) can be derived. Using the relationships between g\\ and q/ RT proposed by Kalmykov and Coffey, the order parameter (P2(p, T)) was calculated as a function of pressure.

Die Kinetik des Zerfalls von tert. Butylperoxypivalat bei hohen Drücken und Temperaturen / The Kinetics of the Decomposition of tert.Butylperoxypivalate up to High Pressures and Temperatures

1981 ◽  
Vol 36 (12) ◽  
pp. 1371-1377 ◽  
Author(s):  
M. Buback ◽  
H. Lendle
Keyword(s):  
Activation Energy ◽  
High Pressure ◽  
High Pressures ◽  
Activation Volume ◽  
Rate Law ◽  
First Order ◽  
Order Rate ◽  
High Pressures And Temperatures ◽  
Kinetics Of

AbstractThe decomposition of tert. butylperoxypivalate dissolved in n-heptane has been measured ir-spectroscopically in optical high-pressure cells up to 2000 bar at temperatures between 65 °C and 105 °C. The reaction follows a first order rate law with an activation energy Ea = 122.3 ±3.0 kJ · mol-1 and an activation volume ⊿V≠ = 1.6 ± 1.0 cm3 mol-1 .

scholarly journals Electrical Conductivity Studies of Composites Based on (Cu1–xAgx)7GeSe5I Solid Solutions

2020 ◽  
Vol 65 (1) ◽  
pp. 55
Author(s):  
A. I. Pogodin ◽  
M. M. Luchynets ◽  
V. I. Studenyak ◽  
O. P. Kokhan ◽  
I. P. Studenyak ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Impedance Spectroscopy ◽  
Solid Solutions ◽  
Frequency Range ◽  
Total Electrical Conductivity ◽  
Cationic Substitution ◽  
Nyquist Plots ◽  
Ionic Components ◽  
Frequency Dependences

Polymer composites based on (Cu1−xAgx)7GeSe5I solid solutions are produced. The electrical conductivity of the composites is measured by impedance spectroscopy in the frequency range from 20 Hz to 2×106 Hz and in the temperature interval 292–338 K. The frequency dependences of the total electrical conductivity are obtained, the Nyquist plots are constructed, and their analysis is performed. The effect of Cu+ →Ag+ cationic substitution on the total electrical conductivity and the activation energy, as well as on the electronic and ionic components of the electrical conductivity of composites based on (Cu1−xAgx)7GeSe5I solid solutions is studied on the basis of compositional dependences.

scholarly journals High Pressure Dielectric Studies of a Substance with the Smectic A1 Phase

1999 ◽  
Vol 54 (8-9) ◽  
pp. 455-458
Author(s):  
Stanisław Urban ◽  
Albert Würflinger
Keyword(s):  
High Pressure ◽  
Relaxation Time ◽  
Phase Transitions ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Dielectric Studies ◽  
Smectic A ◽  
Smectic A Phase ◽  
Nematic Phases

The results of dielectric studies of 5-n-hexyl-2-(4'-isothiocyanato)-l,3-dioxane (6DBT) in the smectic A, phase at pressures up to 150 MPa and temperatures up to 340 K are presented. The low frequen-cy relaxation time τ|| (p, T) yields the activation volume Δ# V|| = RT(∂|| In τ||/p)T and activation enthalpy Δ# H|| = R(∂In τ||/∂T-1)p. The calculated values of these parameters are compared with those ob-tained recently for n-octyl-cyanobiphenyl (8CB) forming the smectic Ad phase. In the case of 6DBT both these quantities are practically constant, whereas those for 8CB decrease, when going away from the phase transitions isotropic -smectic A1 (6DBT) or nematic -smectic Ad (8CB). These differences support our earlier conclusion that increase of pressure leads to a breaking of the antiparallel associa-tions of cyanobiphenyl molecules in the smectic as well as in the nematic phases.

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