Manganese Dioxides: Structural Model and In-Situ Neutron Powder Diffraction Investigation of Thermal Annealing and Electrochemical Reduction

AbstractStarting from the seminal work of De Wolff [1], we have developed a structural description, based on two kinds of defects, which accounts for the scattering function of all γand ε-MnO2. Using numerical simulation results, we propose simple methods to estimate the parameters which characterize real manganese dioxide samples. Real time neutron powder diffraction has been used to investigate in situ the transformations undergone by γ-MnO2 during thermal annealing and electrochemical reduction in alkaline solutions. We have found that thermally induced transformation from MnO2 to ∝-Mn2O3 can involve up to seven different steps and that electrochemical reduction of γ-MnO2 in KOD electrolyte proceeds through three stages, the final one leading in most cases to a breakdown of the initial crystal lattice.

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Electrochemical reduction of La(Ni3.6Co0.7Al0.4Mn0.3) (LaMM) deuterides investigated by in situ neutron powder diffraction: Following the metal-hydride phase transition under technical operating conditions in a KOD electrolyte

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2013.01.186 ◽

2013 ◽

Vol 38 (14) ◽

pp. 5903-5910 ◽

Cited By ~ 1

Author(s):

J. Schefer ◽

L. Keller ◽

Y. Zannatul ◽

S. Paofai ◽

M. Schmalz ◽

...

Keyword(s):

Phase Transition ◽

Electrochemical Reduction ◽

Powder Diffraction ◽

Metal Hydride ◽

Neutron Powder Diffraction ◽

Operating Conditions ◽

Hydride Phase

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In Situ Neutron Powder Diffraction Study of Ti3SiC2 Synthesis

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.2001.tb01003.x ◽

2004 ◽

Vol 84 (10) ◽

pp. 2281-2288 ◽

Cited By ~ 40

Author(s):

Erdong Wu ◽

Erich H. Kisi ◽

Shane J. Kennedy ◽

Andrew J. Studer

Keyword(s):

Diffraction Study ◽

Powder Diffraction ◽

Neutron Powder Diffraction

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Oxygen Ordered Phases in LaxSr1−xMnOy(0 ≤x≤ 0.2, 2.5 ≤ y ≤ 3): An In situ Neutron Powder Diffraction Study

Chemistry of Materials ◽

10.1021/cm703139c ◽

2008 ◽

Vol 20 (4) ◽

pp. 1636-1645 ◽

Cited By ~ 20

Author(s):

Leopoldo Suescun ◽

Bogdan Dabrowski ◽

James Mais ◽

Steven Remsen ◽

James W. Richardson ◽

...

Keyword(s):

Diffraction Study ◽

Powder Diffraction ◽

Neutron Powder Diffraction ◽

Ordered Phases

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Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

Mineralogical Magazine ◽

10.1180/002646100549166 ◽

2000 ◽

Vol 64 (2) ◽

pp. 255-266 ◽

Cited By ~ 10

Author(s):

J. J. Reece ◽

S. A. T. Redfern ◽

M. D. Welch ◽

C. M. B. Henderson

Keyword(s):

Crystal Structure ◽

Phase Transition ◽

New York ◽

High Temperature ◽

Powder Diffraction ◽

Elevated Temperatures ◽

Neutron Powder Diffraction ◽

Site Preference ◽

A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

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Synthesis and structural characterization of Ca12Ga14O33

Scientific Reports ◽

10.1038/s41598-020-73311-w ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Sabrina E. A. McCoy ◽

John R. Salasin ◽

S. Michelle Everett ◽

Claudia J. Rawn

Keyword(s):

Powder Diffraction ◽

Structural Model ◽

Electronic Band Structure ◽

Rietveld Method ◽

Experimental Studies ◽

Phase Evolution ◽

Neutron Powder Diffraction ◽

Electronic Band ◽

Wet Chemistry ◽

X Ray

Abstract Ca12Ga14O33 was successfully synthesized using a wet chemistry technique to promote the homogenous mixing of the Ca and Ga cations. Rietveld refinements on X-ray and neutron powder diffraction data confirm that the compound is isostructural to Ca12Al14O33, however, with a significantly larger lattice parameter allowing for the cages that result from the framework arrangement to expand. In naturally occurring Ca12Al14O33, the mineral mayenite, these cages are occupied by O2− anions, however, experimental studies exchanging the O2− anions with other anions has led to a host of applications, depending on the caged anion. The functional nature of the structure, where framework distortions coupled with cage occupants, are correlated to electronic band structure and modifications to the framework could lead to interesting physical properties. The phase evolution was tracked using thermogravimetric analysis and high temperature X-ray diffraction and showed a lower formation temperature for the Ca12Ga14O33 analogue compared to Ca12Al14O33 synthesized using the same wet chemistry technique. Analyzing both X-ray and neutron powder diffraction using the Rietveld method with two different starting models results in one structural model, with one Ca position and the caged O on a 24d special position, being preferred.

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Performance of Cu-coated vanadium cans forin situneutron powder diffraction experiments on hydrogen storage materials

Journal of Applied Crystallography ◽

10.1107/s002188981202938x ◽

2012 ◽

Vol 45 (5) ◽

pp. 902-905 ◽

Cited By ~ 4

Author(s):

Roxana Flacau ◽

Jim Bolduc ◽

Thomas Bibienne ◽

Jacques Huot ◽

Helmut Fritzsche

Keyword(s):

Hydrogen Storage ◽

High Temperatures ◽

Powder Diffraction ◽

Neutron Powder Diffraction ◽

Simple Design ◽

Hydrogen Storage Materials ◽

High Quality ◽

Handling System ◽

Storage Materials

In situneutron powder diffraction (NPD) measurements of hydrogenation processes taking place at high temperatures pose difficulties related to the choice of sample can material. This article describes a simple design for a copper-coated vanadium can and its connection to the gas-handling system, tested up to 523 K. High-quality NPD patterns of TiV1.2Mn0.8body-centred cubic alloy, as-cast and partially hydrogenated, were collected at 373 K and deuterium pressures up to 2 bar (200 kPa).

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