scholarly journals Selective Metathesis Synthesis of MgCr2S4 by Control of Thermodynamic Driving Forces

2019 ◽  
Author(s):  
akira miura ◽  
Hiroaki Ito ◽  
Christopher Bartel ◽  
Wenhao Sun ◽  
Nataly Carolina Rosero-Navarro ◽  
...  
Keyword(s):  
Driving Force ◽  
Driving Forces ◽  
S Phase ◽  
Inorganic Materials ◽  
Synthesis Methods ◽  
Metathesis Reaction ◽  
Reaction Enthalpy ◽  
Alternative Synthesis ◽  
Thermodynamic Driving Force ◽  
Kinetics Of

MgCr<sub>2</sub>S<sub>4</sub> thiospinel is predicted to be a compelling Mg-cathode material, but its preparation via traditional solid-state synthesis methods has proven challenging. Wustrow et al. [Inorg. Chem. 57, 14 (2018)] found that the formation of MgCr<sub>2</sub>S<sub>4</sub> from MgS + Cr<sub>2</sub>S<sub>3</sub> binaries requires weeks of annealing at 800 ℃ with numerous intermediate regrinds. The slow reaction kinetics of MgS + Cr<sub>2</sub>S<sub>3 </sub>--> MgCr<sub>2</sub>S<sub>4</sub> can be attributed to a miniscule thermodynamic driving force of ΔH = –2 kJ/mol. Here, we demonstrate that the double ion-exchange metathesis reaction, MgCl<sub>2</sub> + 2 NaCrS<sub>2</sub> --> MgCr<sub>2</sub>S<sub>4</sub> + 2 NaCl, has a reaction enthalpy of ΔH = –47 kJ/mol, which is thermodynamically driven by the large exothermicity of NaCl formation. Using this metathesis reaction, we successfully synthesized MgCr<sub>2</sub>S<sub>4</sub> nanoparticles (< 200 nm) from MgCl<sub>2</sub> and NaCrS<sub>2</sub> precursors in a KCl flux at 500 °C in only 30 minutes. NaCl and other metathesis byproducts are then easily washed away by water. We rationalize the selectivity of MgCr<sub>2</sub>S<sub>4</sub> in the metathesis reaction from the topology of the DFT-calculated pseudo-ternary MgCl<sub>2</sub>-CrCl<sub>3</sub>-Na<sub>2</sub>S phase diagram. Our work helps to establish metathesis reactions as a powerful alternative synthesis route to inorganic materials that have otherwise small reaction energies from conventional precursors.<br>

scholarly journals Selective Metathesis Synthesis of MgCr2S4 by Control of Thermodynamic Driving Forces

2019 ◽  
Author(s):  
akira miura ◽  
Hiroaki Ito ◽  
Christopher Bartel ◽  
Wenhao Sun ◽  
Nataly Carolina Rosero-Navarro ◽  
...  
Keyword(s):  
Driving Force ◽  
Driving Forces ◽  
S Phase ◽  
Inorganic Materials ◽  
Synthesis Methods ◽  
Metathesis Reaction ◽  
Reaction Enthalpy ◽  
Alternative Synthesis ◽  
Thermodynamic Driving Force ◽  
Kinetics Of

MgCr<sub>2</sub>S<sub>4</sub> thiospinel is predicted to be a compelling Mg-cathode material, but its preparation via traditional solid-state synthesis methods has proven challenging. Wustrow et al. [Inorg. Chem. 57, 14 (2018)] found that the formation of MgCr<sub>2</sub>S<sub>4</sub> from MgS + Cr<sub>2</sub>S<sub>3</sub> binaries requires weeks of annealing at 800 ℃ with numerous intermediate regrinds. The slow reaction kinetics of MgS + Cr<sub>2</sub>S<sub>3 </sub>--> MgCr<sub>2</sub>S<sub>4</sub> can be attributed to a miniscule thermodynamic driving force of ΔH = –2 kJ/mol. Here, we demonstrate that the double ion-exchange metathesis reaction, MgCl<sub>2</sub> + 2 NaCrS<sub>2</sub> --> MgCr<sub>2</sub>S<sub>4</sub> + 2 NaCl, has a reaction enthalpy of ΔH = –47 kJ/mol, which is thermodynamically driven by the large exothermicity of NaCl formation. Using this metathesis reaction, we successfully synthesized MgCr<sub>2</sub>S<sub>4</sub> nanoparticles (< 200 nm) from MgCl<sub>2</sub> and NaCrS<sub>2</sub> precursors in a KCl flux at 500 °C in only 30 minutes. NaCl and other metathesis byproducts are then easily washed away by water. We rationalize the selectivity of MgCr<sub>2</sub>S<sub>4</sub> in the metathesis reaction from the topology of the DFT-calculated pseudo-ternary MgCl<sub>2</sub>-CrCl<sub>3</sub>-Na<sub>2</sub>S phase diagram. Our work helps to establish metathesis reactions as a powerful alternative synthesis route to inorganic materials that have otherwise small reaction energies from conventional precursors.<br>

scholarly journals Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 699 ◽  
Author(s):  
Miloslav Pekař
Keyword(s):  
Steady State ◽  
Chemical Reaction ◽  
Driving Force ◽  
Driving Forces ◽  
Point Of View ◽  
Fluid Mixtures ◽  
Similar Work ◽  
Chemical Potentials ◽  
Thermodynamic Driving Force ◽  
Reacting Systems

Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on the steady state, which has been the core subject of previous similar work. It is argued that such relationships should also contain, besides the thermodynamic driving force, a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in the Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of force, resistance and flux.

scholarly journals Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

2020 ◽  
Author(s):  
Miloslav Pekař
Keyword(s):  
Steady State ◽  
Chemical Reaction ◽  
Driving Force ◽  
Driving Forces ◽  
Point Of View ◽  
Fluid Mixtures ◽  
Similar Work ◽  
Chemical Potentials ◽  
Thermodynamic Driving Force ◽  
Reacting Systems

Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on steady state, which has been the core subject of previous similar work. It is argued that such relationships should contain, besides the thermodynamic driving force, also a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of force-resistance-flux.

scholarly journals Kinetics of Hydride Transfer from Metal-Free Hydride Donors to CO2

2020 ◽  
Author(s):  
Ravindra Weerasooriya ◽  
Jonathan L. Gesiorski ◽  
Abdulaziz Alherz ◽  
Stefan Ilic ◽  
George Hargenrader ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Driving Force ◽  
Selective Reduction ◽  
Hydride Transfer ◽  
Metal Free ◽  
Thermodynamic Driving Force ◽  
Solar Conversion ◽  
Reorganization Energies ◽  
Kinetics Of ◽  
Kinetic Barriers

Selective reduction of CO<sub>2</sub> to formate represents an ongoing challenge in photoelectrocatalysis. To provide mechanistic insights, we investigate the kinetics of hydride transfer (HT) from a series of metal-free hydride donors to CO<sub>2</sub>. The observed dependence of experimental and calculated HT barriers on the thermodynamic driving force was modeled using the Marcus hydride transfer formalism to obtain the insights into the effect of reorganization energies on the reaction kinetics. Our results indicate that, even if the most ideal hydride donor were discovered, the HT to CO<sub>2</sub> would exhibit sluggish kinetics (less than 100 turnovers at 0.1 eV driving force), indicating that the conventional HT may not be an appropriate mechanism for Solar conversion of CO<sub>2</sub> to formate. We propose that the conventional HT mechanism should not be considered for CO<sub>2</sub> reduction catalysis and argue that the orthogonal HT mechanism, previously proposed to address thermodynamic limitations of this reaction, may also lead to lower kinetic barriers for CO<sub>2</sub> reduction to formate.

scholarly journals Kinetics of Hydride Transfer from Metal-Free Hydride Donors to CO2

2020 ◽  
Author(s):  
Ravindra Weerasooriya ◽  
Jonathan L. Gesiorski ◽  
Abdulaziz Alherz ◽  
Stefan Ilic ◽  
George Hargenrader ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Driving Force ◽  
Selective Reduction ◽  
Hydride Transfer ◽  
Metal Free ◽  
Thermodynamic Driving Force ◽  
Solar Conversion ◽  
Reorganization Energies ◽  
Kinetics Of ◽  
Kinetic Barriers

Selective reduction of CO<sub>2</sub> to formate represents an ongoing challenge in photoelectrocatalysis. To provide mechanistic insights, we investigate the kinetics of hydride transfer (HT) from a series of metal-free hydride donors to CO<sub>2</sub>. The observed dependence of experimental and calculated HT barriers on the thermodynamic driving force was modeled using the Marcus hydride transfer formalism to obtain the insights into the effect of reorganization energies on the reaction kinetics. Our results indicate that, even if the most ideal hydride donor were discovered, the HT to CO<sub>2</sub> would exhibit sluggish kinetics (less than 100 turnovers at 0.1 eV driving force), indicating that the conventional HT may not be an appropriate mechanism for Solar conversion of CO<sub>2</sub> to formate. We propose that the conventional HT mechanism should not be considered for CO<sub>2</sub> reduction catalysis and argue that the orthogonal HT mechanism, previously proposed to address thermodynamic limitations of this reaction, may also lead to lower kinetic barriers for CO<sub>2</sub> reduction to formate.

scholarly journals Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

2020 ◽  
Author(s):  
Miloslav Pekař
Keyword(s):  
Steady State ◽  
Chemical Reaction ◽  
Driving Force ◽  
Driving Forces ◽  
Point Of View ◽  
Fluid Mixtures ◽  
Similar Work ◽  
Chemical Potentials ◽  
Thermodynamic Driving Force ◽  
Reacting Systems

Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on steady state, which has been the core subject of previous similar work. It is argued that such relationships should contain, besides the thermodynamic driving force, also a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of force-resistance-flux.

scholarly journals Thermodynamic Driving Forces and Chemical Reaction Fluxes; Reflections on the Steady State

2019 ◽  
Author(s):  
Miloslav Pekař
Keyword(s):  
Steady State ◽  
Chemical Reaction ◽  
Driving Force ◽  
Driving Forces ◽  
Point Of View ◽  
Fluid Mixtures ◽  
Similar Work ◽  
Chemical Potentials ◽  
Thermodynamic Driving Force ◽  
Reacting Systems

Molar balances of continuous and batch reacting systems with a simple reaction are analyzed from the point of view of finding relationships between the thermodynamic driving force and the chemical reaction rate. Special attention is focused on steady state, which has been the core subject of previous similar work. It is argued that such relationships should contain, besides the thermodynamic driving force, also a kinetic factor, and are of a specific form for a specific reacting system. More general analysis is provided by means of the non-equilibrium thermodynamics of linear fluid mixtures. Then, the driving force can be expressed either in Gibbs energy (affinity) form or on the basis of chemical potentials. The relationships can be generally interpreted in terms of force-resistance-flux.

Simple Analytical Models for Dendrite Arm Coarsening under High and Medium Temperature Gradients

2006 ◽  
Vol 508 ◽  
pp. 331-336 ◽  
Author(s):  
Altan Turkeli
Keyword(s):  
Driving Force ◽  
Driving Forces ◽  
Zone Melting ◽  
Temperature Gradients ◽  
Analytical Models ◽  
Curvature Effect ◽  
Medium Temperature ◽  
Gradient Zone ◽  
Coarsening Kinetics ◽  
Kinetics Of

The coarsening of secondary dendrite arms is discussed in terms of two different driving forces, which are the curvature effect and the temperature gradient zone melting (TGZM) effect. It is shown that the driving force due the TGZM effect can be higher than that due to the curvature effect at high temperature gradients and equal to each other at medium temperature gradients. For such high and medium temperature gradients, simple analytical models are proposed to predict the coarsening kinetics of secondary arms during solidification in a binary alloy. The prediction of the present analytical model agrees with experimental data obtained from the solidification of Fe – 1.6 wt. % Mn – 0.75 wt. % C steel.

Dynamic Transformation of Austenite at Temperatures above the Ae3

2018 ◽  
Vol 941 ◽  
pp. 633-638
Author(s):  
John Joseph Jonas ◽  
Clodualdo Aranas Jr. ◽  
Samuel F. Rodrigues
Keyword(s):  
Electron Microscopy ◽  
Driving Force ◽  
Energy Difference ◽  
Accelerated Cooling ◽  
Free Energy Difference ◽  
Dynamic Transformation ◽  
Plate Rolling ◽  
Temperature Transformation ◽  
Mn Steel ◽  
Kinetics Of

Under loading above the Ae3 temperature, austenite transforms displacively into Widmanstätten ferrite. Here the driving force for transformation is the net softening during the phase change while the obstacle consists of the free energy difference between austenite and ferrite as well as the work of shear accommodation and dilatation during the transformation. Once the driving force is higher than the obstacle, phase transformation occurs. This phenomenon was explored here by means of the optical and electron microscopy of a C-Mn steel deformed above their transformation temperatures. Strain-temperature-transformation (STT) curves are presented that accurately quantify the amount of dynamically formed ferrite; the kinetics of retransformation are also specified in the form of appropriate TTRT diagrams. This technique can be used to improve the models for transformation on accelerated cooling in strip and plate rolling.

scholarly journals Driving forces on dislocations: finite element analysis in the context of the non-singular dislocation theory

2021 ◽  
Author(s):  
Xiandong Zhou ◽  
Christoph Reimuth ◽  
Peter Stein ◽  
Bai-Xiang Xu
Keyword(s):  
Finite Element ◽  
Dislocation Loop ◽  
Driving Force ◽  
Complex Geometry ◽  
Driving Forces ◽  
Singular Solutions ◽  
Dislocation Model ◽  
Configurational Force ◽  
Element Analysis ◽  
Dislocation Configuration

AbstractThis work presents a regularized eigenstrain formulation around the slip plane of dislocations and the resultant non-singular solutions for various dislocation configurations. Moreover, we derive the generalized Eshelby stress tensor of the configurational force theory in the context of the proposed dislocation model. Based on the non-singular finite element solutions and the generalized configurational force formulation, we calculate the driving force on dislocations of various configurations, including single edge/screw dislocation, dislocation loop, interaction between a vacancy dislocation loop and an edge dislocation, as well as a dislocation cluster. The non-singular solutions and the driving force results are well benchmarked for different cases. The proposed formulation and the numerical scheme can be applied to any general dislocation configuration with complex geometry and loading conditions.

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