Activation energy, activation enthalpy, activation volume

2011 ◽  
Keyword(s):  
Activation Energy ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Energy Activation

Activation Energy−Activation Volume Master Plots for Ion Transport Behavior in Polymer Electrolytes and Supercooled Molten Salts

2005 ◽  
Vol 109 (35) ◽  
pp. 16567-16570 ◽  
Author(s):  
Malcolm D. Ingram ◽  
Corrie T. Imrie ◽  
Zlatka Stoeva ◽  
Steven J. Pas ◽  
Klaus Funke ◽  
...  
Keyword(s):  
Activation Energy ◽  
Ion Transport ◽  
Polymer Electrolytes ◽  
Molten Salts ◽  
Activation Volume ◽  
Transport Behavior ◽  
Master Plots ◽  
Energy Activation

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.

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.

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.

Towards constraining Mars' thermal evolution using machine learning

2021 ◽  
Author(s):  
Siddhant Agarwal ◽  
Nicola Tosi ◽  
Pan Kessel ◽  
Sebastiano Padovan ◽  
Doris Breuer ◽  
...  
Keyword(s):  
Activation Energy ◽  
Enrichment Factor ◽  
Activation Volume ◽  
Initial Conditions ◽  
Thermal Evolution ◽  
Diffusion Creep ◽  
Dynamic Simulations ◽  
Mixture Density ◽  
Lithospheric Thickness ◽  
Mantle Temperature

<p>The thermal evolution of terrestrial planets depends strongly on several parameters and initial conditions that are poorly constrained. Often, direct or indirect observables from planetary missions such as elastic lithospheric thickness, crustal thickness and duration of volcanism are inverted to infer the unknown parameter values and initial conditions. The non-uniqueness and non-linearity of this inversion necessitates a probabilistic inversion framework. However, due to the expensive nature of forward dynamic simulations of thermal convection , Markov Chain Monte Carlo methods are rarely used. To address this shortcoming, some studies have recently shown the effectiveness of Mixture Density Networks (MDN) (Bishop 1995) in being able to approximate the posterior probability using only the dataset of simulations run prior to the inversion (Meier et al. 2007, de Wit et al. 2013, Käufl et al. 2016, Atkins et al. 2016).</p><p>Using MDNs, we systematically isolate the degree to which a parameter can be constrained using different “present-day” synthetic observables from 6130 simulations for a Mars-like planet. The dataset – generated using the mantle convection code GAIA (Hüttig et al. 2013)- is the same as that used by Agarwal et al. (2020) for a surrogate modelling study.</p><p>The loss function used to optimize the MDN (log-likelihood) provides a single robust quantity that can be used to measure how well a parameter can be constrained. We test different numbers and combinations of observables (heat flux at the surface and core-mantle boundary, radial contraction, melt produced, elastic lithospheric thickness, and duration of volcanism) to constrain the following parameters: reference viscosity, activation energy and activation volume of the diffusion creep rheology, an enrichment factor for radiogenic elements in the crust, and initial mantle temperature. If all observables are available, reference viscosity can be constrained to within 32% of its entire range (10<sup>19</sup>−10<sup>22</sup> Pa s), crustal enrichment factor (1−50) to within 15%, activation energy (10<sup>5</sup>−5×10<sup>5</sup> J mol-1 ) to within 80%, and initial mantle temperature (1600−1800K) to within 39%. The additional availability of the full present-day temperature profile or parts of it as an observable tightens the constraints further. The activation volume (4×10<sup>-6</sup> −10×10<sup>-6</sup>  m<sup>3</sup> mol<sup>-1</sup>) cannot be constrained and requires research into new observables in space and time, as well as fields other than just temperature. Testing different levels of uncertainty (simulated using Gaussian noise) in the observables, we found that constraints on different parameters loosen at different rates, with initial temperature being the most sensitive. Finally, we present how the marginal MDN proposed by Bishop (1995) can be modified to model the joint probability for all parameters, so that  the inter-parameter correlations and the associated degeneracy can be capture, thereby providing a more comprehensive picture of all the evolution scenarios that fit given observational constraints.</p>

Dielectric Studies of 4-w-Hexyloxy-4’-Cyanobiphenyl (60CB) at Elevated Pressure

1999 ◽  
Vol 54 (6-7) ◽  
pp. 365-369 ◽  
Author(s):  
S. Urban ◽  
M. Smoluchowski
Keyword(s):  
Dielectric Permittivity ◽  
Order Parameter ◽  
Nematic Phase ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Ambient Pressure ◽  
Relaxation Times ◽  
Elevated Pressure ◽  
Dielectric Anisotropy ◽  
Dielectric Studies

Abstract The principal dielectric permittivity components in the nematic phase of 4-rc-hexyloxy-4’-cyanobiph-enyl (60CB) were measured as functions of temperature at ambient pressure and as functions of pres-sure up to 100 MPa at several constant temperatures. The dielectric anisotropy is analized in the frame of the Maier-Meier equations. The pressure dependence of the order parameter is deduced. Preliminary results for the activation volume and activation enthalpy from the pressure and temperature dependenc-es of the longitudinal relaxation times are obtained.

Oxidation of dibenzothiophene using the heterogeneous catalyst of tungsten-based carbon nanotubes

2019 ◽  
Vol 8 (1) ◽  
pp. 68-77 ◽  
Author(s):  
Nguyen Duc Vu Quyen ◽  
Tran Ngoc Tuyen ◽  
Dinh Quang Khieu ◽  
Ho Van Minh Hai ◽  
Dang Xuan Tin ◽  
...  
Keyword(s):  
Activation Energy ◽  
Carbon Nanotubes ◽  
Heterogeneous Catalyst ◽  
Activation Enthalpy ◽  
Intermediate Compound ◽  
Activation Process ◽  
Modern Methods ◽  
The Stability ◽  
Reaction Cycles ◽  
Mechanism Of The Reaction

Abstract Highly effective tungsten-based carbon nanotubes (W/CNT) were synthesized and used as a heterogeneous catalyst for the oxidation of dibenzothiophene (DBT) with the oxidant H2O2. The obtained materials were characterized by modern methods. The Langmuir–Hinshelwood kinetics model described the precursor mechanism of the reaction well through an intermediate compound. The low activation energy showed that the reaction was mainly controlled by diffusion. The positive activation enthalpy proved the endothermic nature of the activation process, and this process did not alter the inside structure of the catalyst. The thermodynamic parameters of the reaction were determined, which implied that the oxidation was endothermic and spontaneous at 303 K. The more negative values of the Gibbs free energy from 283 to 323 K confirmed that the reaction was more favorable at high temperatures. The stability and activity of catalyst were retained after three reaction cycles.

scholarly journals The Application of Equivalent Age Concept to Sand Concrete Compared to Ordinary Concrete

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Nabil Bella ◽  
Ilham Aguida Bella ◽  
Aissa Asroun
Keyword(s):  
Activation Energy ◽  
Coarse Aggregate ◽  
Strength Development ◽  
Arrhenius Law ◽  
Ordinary Concrete ◽  
Equivalent Age ◽  
Heat Treated ◽  
Sand Filler ◽  
Energy Activation ◽  
Prestressed Beams

In this research the equivalent age concept was used, in order to simulate strength development of heat treated sand concrete compared with ordinary concrete at different temperature, 35, 55, and 70°C, and validate the simulation results with our experimental results. Sand concrete is a concrete with a lower or without coarse aggregate dosage; it is used to realize thin element as small precast prestressed beams, in injected concrete or in regions where sand is in extra quantity and the coarse aggregate in penury. This concrete is composed by principally sand, filler, superplasticizer, water, and cement. The results show that the simulation of ordinary concrete was acceptable with an error lower than 20%. But the error was considerable for the sand concrete. The error was due to large superplasticizer dosage, which modified the hardening of sand concrete; the most influent parameter in Arrhenius law is apparent energy activation, to search for the value of the activation energy which gives the best simulation; a superposition is used of two curves of different temperature and with superplasticizer dosage 4% and several values of activation energy, 15, 20, 25, and 30 × 10 kcal. The simulation becomes ameliorated with the adequate value of activation energy.

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