scholarly journals Non-Equilibrium Crystallization Pathways of Manganese Oxides in Aqueous Solution

2018 ◽  
Author(s):  
Wenhao Sun ◽  
Daniil A. Kitchaev ◽  
Denis Kramer ◽  
Gerbrand Ceder
Keyword(s):  
Metal Oxide ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Manganese Oxides ◽  
Energy Landscape ◽  
Metastable Phases ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Pourbaix Diagram ◽  
Non Equilibrium

<p>Aqueous precipitation of transition metal oxides often proceeds through non-equilibrium phases, whose appearance cannot be anticipated from traditional phase diagrams. Without a precise understanding of which metastable phases form, or their lifetimes, targeted synthesis of specific metal oxides can become a trial-and-error process. Here, we derive a new thermodynamic potential for the free-energy of a metal oxide in water, which reveals a hidden metastable energy landscape above the equilibrium Pourbaix diagram. By combining this ‘Pourbaix potential’ with classical nucleation theory, we interrogate how solution conditions can influence the multistage oxidation pathways of manganese oxides. We calculate that even within the same phase stability region of a Pourbaix diagram, subtle variations in <i>p</i>H and redox potential can redirect a crystallization pathway through different metastable phases. Our theoretical framework offers a predictive platform to navigate through the thermodynamic and kinetic energy landscape towards the rational synthesis of target metal oxide phases.</p>

scholarly journals Non-Equilibrium Crystallization Pathways of Manganese Oxides in Aqueous Solution

2018 ◽  
Author(s):  
Wenhao Sun ◽  
Daniil A. Kitchaev ◽  
Denis Kramer ◽  
Gerbrand Ceder
Keyword(s):  
Metal Oxide ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Manganese Oxides ◽  
Energy Landscape ◽  
Metastable Phases ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Pourbaix Diagram ◽  
Non Equilibrium

<p>Aqueous precipitation of transition metal oxides often proceeds through non-equilibrium phases, whose appearance cannot be anticipated from traditional phase diagrams. Without a precise understanding of which metastable phases form, or their lifetimes, targeted synthesis of specific metal oxides can become a trial-and-error process. Here, we derive a new thermodynamic potential for the free-energy of a metal oxide in water, which reveals a hidden metastable energy landscape above the equilibrium Pourbaix diagram. By combining this ‘Pourbaix potential’ with classical nucleation theory, we interrogate how solution conditions can influence the multistage oxidation pathways of manganese oxides. We calculate that even within the same phase stability region of a Pourbaix diagram, subtle variations in <i>p</i>H and redox potential can redirect a crystallization pathway through different metastable phases. Our theoretical framework offers a predictive platform to navigate through the thermodynamic and kinetic energy landscape towards the rational synthesis of target metal oxide phases.</p>

Ostwald’s step rule: a consequence of growth kinetics and nano-scale energy landscape

2021 ◽  
Author(s):  
Patrick Meister
Keyword(s):  
Metastable Phase ◽  
Energy Landscape ◽  
Stable State ◽  
Dynamic Modelling ◽  
Atomic Scale ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Natural Environments ◽  
Mineral Formation ◽  
Nano Scale

&lt;p&gt;In his 1897 article on the formation and transformation of solid phases, Friedrich Wilhelm Ostwald described the phenomenon that hydrous sodium chlorate precipitates from an oversaturated solution, despite the fact that this phase is much more soluble than the non-hydrous salt. The fundamental concept, also known as Ostwald&amp;#8217;s step rule, is best summarized on page 307 of his article (here translated to English):&lt;/p&gt;&lt;p&gt;&amp;#8220;... Such phenomena also frequently occur during melting and condensation of steam and even in homogeneous chemical reactions, and I would like to summarize the previous experiences with this matter in the single phrase that during departure from any state, and the transition to a more stable one, not the under given circumstances most stable state is reached, but the nearest one.&amp;#8220;&lt;/p&gt;&lt;p&gt;Despite its major importance for mineral formation under Earth&amp;#8217;s surface conditions, this concept is still not fully understood on a mechanistic level. While Ostwald&amp;#8217;s step rule is commonly explained with the classical nucleation theory, there are several inconsistencies, especially the conundrum that sometimes stable phases, such as dolomite or quartz, do not form as long as a metastable phase is supersaturated. I propose an alternative interpretation that would be consistent with Ostwald&amp;#8217;s (1897) original formulation as well as with several observations from natural environments and laboratory experiments. If &amp;#8220;nearest&amp;#8221; (in German: &amp;#8220;n&amp;#228;chstliegend&amp;#8221;) is not understood as &amp;#8220;thermodynamically most similar&amp;#8221;, but as the phase with the lowest kinetic barrier, Ostwald&amp;#8217;s step rule should be always valid. The kinetic barrier is surface specific and independent of supersaturation, but it depends on the atomic scale interfacial energy landscape. This concept would better represent the power of Ostwald&amp;#8217;s step rule to explain mineral formation processes and how they are affected by chemical and biological influences. New nano-scale analytical techniques in combination with advanced molecular dynamic modelling bear great potential to explain and appreciate the importance of Ostwald&amp;#8217;s step rule.&lt;/p&gt;

Numerical Simulation of Non-Equilibrium Condensation in Supercritical CO2 Compressors

2019 ◽  
Author(s):  
Kevin W. Brinckman ◽  
Ashvin Hosangadi ◽  
Zisen Liu ◽  
Timothy Weathers
Keyword(s):  
Critical Point ◽  
Residence Time ◽  
Supercritical Co2 ◽  
Equilibrium Phase ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Working Fluid ◽  
Modeling Framework ◽  
Test Loop ◽  
Non Equilibrium

Abstract There is increasing interest in supercritical CO2 processes, such as Carbon Capture and Storage, and electric power production, which require compressors to pressurize CO2 above the critical point. For supercritical compressor operation close to the critical point there is a concern that the working fluid could cross into the subcritical regime which could lead to issues with compressor performance if condensation was to occur in regions where the fluid dropped below the saturation point. Presently, the question of whether there is sufficient residence time at subcritical conditions for condensation onset in supercritical CO2 compressors is an unresolved issue. A methodology is presented towards providing a validated simulation capability for predicting condensation in supercritical CO2 compressors. The modeling framework involves the solution of a discrete droplet phase coupled to the continuum gas phase to track droplet nucleation and growth. The model is implemented in the CRUNCH CFD® Computational Fluid Dynamics code that has been extensively validated for simulation at near critical conditions with a real fluid framework for accurate predictions of trans-critical CO2 processes. Results of predictions using classical nucleation theory to model homogeneous nucleation of condensation sites in supersaturated vapor regions are presented. A non-equilibrium phase-change model is applied to predict condensation on the nuclei which grow in a dispersed-phase droplet framework. Model validation is provided against experimental data for condensation of supercritical CO2 in a De Laval nozzle including the Wilson line location. The model is then applied for prediction of condensation in the compressor of the Sandia test loop at mildly supercritical inlet conditions. The results suggest that there is sufficient residence time at the conditions analyzed to form localized nucleation sites, however, droplets are expected to be short lived as the model predicts they will rapidly vaporize.

Binary metal oxide: advanced energy storage materials in supercapacitors

2015 ◽  
Vol 3 (1) ◽  
pp. 43-59 ◽  
Author(s):  
Yufei Zhang ◽  
Laiquan Li ◽  
Haiquan Su ◽  
Wei Huang ◽  
Xiaochen Dong
Keyword(s):  
Energy Storage ◽  
Transition Metal ◽  
Metal Oxide ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Electrode Materials ◽  
Electronic Conductivity ◽  
Reversible Capacity ◽  
Energy Storage Materials ◽  
Binary Metal Oxide

Binary transition metal oxides (BTMOs) possess higher reversible capacity, better structural stability and electronic conductivity, and have been widely studied to be novel electrode materials for supercapacitors.

An electroless-plating-like solution deposition approach for large-area flexible thin films of transition metal oxide nanocrystals

2014 ◽  
Vol 2 (12) ◽  
pp. 2266-2271 ◽  
Author(s):  
Liangzhuan Wu ◽  
Yuan Yu ◽  
Xianying Han ◽  
Yuan Zhang ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Thin Films ◽  
Transition Metal ◽  
Metal Oxide ◽  
Metal Oxides ◽  
Electroless Plating ◽  
Transition Metal Oxides ◽  
Transition Metal Oxide ◽  
Large Area ◽  
Solution Deposition

We report an electroless-plating-like solution deposition approach for large-area flexible thin films of crystalline transition metal oxides.

RRAM electronics and Switching Mechanism

2007 ◽  
Vol 997 ◽  
Author(s):  
Sheng Teng Hsu ◽  
TingKai Li
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Intrinsic Property ◽  
High Density ◽  
Displacement Current ◽  
Resistance Increase ◽  
Valence Electrons ◽  
Pulse Polarity ◽  
Non Equilibrium

AbstractThe property of PCMO RRAM memory devices have been studied in terms of electrical pulse width, Pulse polarity, voltage ramping, film thickness, resistivity distribution, and temperature dependent of resistance. The PCMO material is deposited using MOD, PVD, or PLD process. The experimental results clearly indicated the resistance increase is due to localization of valence electrons. The narrow pulse induced resistance increase near the cathode indicated the localization of valence electrons is the effect of high density of excessive non-equilibrium electrons through the well known Jahn-Teller effect. High density of non-equilibrium electrons may also be induced by any other means such as displacement current, space charge limited current, SCLC, and radiation. High field intensity collapses the localized valence electrons and returns the device to the low resistance state. This is the intrinsic property of transition metal oxides. We expect all doped and un-doped transition metal oxides to exhibit resistance switching property.

Interaction of a bioactive molecule with surfaces of nanoscale transition metal oxides: experimental and theoretical studies

2019 ◽  
Vol 43 (42) ◽  
pp. 16621-16628 ◽  
Author(s):  
Prasanta Bandyopadhyay ◽  
Rajkumar Jana ◽  
Kalishankar Bhattacharyya ◽  
Oleg I. Lebedev ◽  
Uma Dutta ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Oxide ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Theoretical Studies ◽  
Schematic Diagram ◽  
Bioactive Molecule ◽  
Experimental And Theoretical Studies

Schematic diagram of metal oxide–BTT interaction and the associated changes in experimental UV-Vis spectra. BTT adsorbed α-Fe2O3 is represented by red spectra, while green spectra represent BTT adsorbed NiO. Black spectra represent pure BTT spectra.

Spatially resolved surface valence gradient and structural transformation of lithium transition metal oxides in lithium-ion batteries

2016 ◽  
Vol 18 (42) ◽  
pp. 29064-29075 ◽  
Author(s):  
Hanshuo Liu ◽  
Matthieu Bugnet ◽  
Matteo Z. Tessaro ◽  
Kristopher J. Harris ◽  
Mark J. R. Dunham ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Oxide ◽  
Cathode Material ◽  
Metal Oxides ◽  
Lithium Ion Batteries ◽  
Transition Metal Oxides ◽  
Lithium Ion ◽  
Spatially Resolved ◽  
Oxide Cathode ◽  
Electrochemical Cycling

Study on the chemical and structural degradation of layered lithium transition metal oxide cathode material upon electrochemical cycling.

scholarly journals Nanostructured transition metal oxides obtained by SPVD

2020 ◽  
Vol 7 ◽  
pp. 12
Author(s):  
Adriana Gabriela Plăiașu ◽  
Marian Cătălin Ducu ◽  
Sorin Georgian Moga ◽  
Aurelian Denis Negrea ◽  
Ecaterina Magdalena Modan
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Physical Vapor Deposition ◽  
Manganese Oxides ◽  
Oxidation States ◽  
Microstructural Characteristics ◽  
Original Process ◽  
Synthesis Parameters ◽  
D Orbitals

The interest in the unique properties associated with materials having structures on a nanometer scale has been increasing at an exponential rate in last decade. Transition metal oxides are preferred materials for catalytic applications due to their half-filled d orbitals that make them exist in different oxidation states. Transition metal oxides show a broad structural variety due to their ability to form phases of varying metal to oxygen ratios reflecting multiple stable oxidation states of the metal ions. The Solar Physical Vapor Deposition (SPVD) presented in the paper as elaboration method is an original process to prepare nanopowders working under concentrated sunlight in 2 kW solar furnaces. The influence of the synthesis parameters on the chemical and microstructural characteristics of zinc and manganese oxides synthesized nanophases has been systematically studied using XRD, SEM and EDX.

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