Transformation of ferrihydrite to hematite: anin situinvestigation on the kinetics and mechanisms

AbstractThe kinetics and mechanisms of the transformation of 2-line ferrihydrite (FH) to hematite (HM), in the presence of Pb at elevated temperatures and high pH condition, were elucidated using synchrotron-based,in situenergy dispersive X-ray diffraction (EDXRD). The time-resolved diffraction data indicated that HM crystallization occurred via a two-stage process. Based on the EDXRD data, combined with high-resolution electron microscopic images, an aqueous-aided 2D growth mechanism is proposed for both HM crystallization stages.

Download Full-text

High resolution electron microscopic and X-ray studies of non-random disorder in an unusual layered silicate (chloritoid)

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1978.0109 ◽

1978 ◽

Vol 361 (1707) ◽

pp. 399-411 ◽

Cited By ~ 12

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Structural Model ◽

Layered Silicate ◽

Real Space ◽

X Ray Diffraction ◽

Electron Microscopic ◽

X Ray ◽

Resolution Electron ◽

Random Disorder

The power of high resolution electron microscopy as a technique for the direct study of non-random disorder in layered minerals is illustrated by the discovery, reported herein, of two new polytypes (one of monoclinic, the other of trigonal symmetry) in the orthosilicate chloritoid. These new variants had hitherto escaped detection in previous X-ray studies of chloritoid. Several specimens of this layered mineral, which cleaves on {110} as well as the expected {001} planes, were also analysed in parallel by X-ray diffraction, the limitations of which are demonstrated by these investigations. The X-ray diffraction procedures, unlike the real-space electron microscopic approach, yield no information concerning the inhomogeneity of intergrowths of one polytype within others. Apart from the existence of new polytypes, unexpected structural faults, in which one polytypic variant terminates within another, have also been identified by electron microscopy. A plausible structural model, which describes the atomic reorganization and the implied change in chemical composition, is proposed for this fault.

Download Full-text

In situ time resolved wide angle X-ray diffraction study of nanotube carpet growth: Nature of catalyst particles and progressive nanotube alignment

Carbon ◽

10.1016/j.carbon.2015.01.046 ◽

2015 ◽

Vol 87 ◽

pp. 246-256 ◽

Cited By ~ 10

Author(s):

Périne Landois ◽

Mathieu Pinault ◽

Stéphan Rouzière ◽

Dominique Porterat ◽

Cristian Mocuta ◽

...

Keyword(s):

Diffraction Study ◽

Wide Angle ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray

Download Full-text

Applications of High-Resolution Powder X-Ray Diffraction

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.130.7 ◽

2007 ◽

Vol 130 ◽

pp. 7-14 ◽

Cited By ~ 4

Author(s):

Andrew N. Fitch

Keyword(s):

High Resolution ◽

Synchrotron Radiation ◽

Powder Diffraction ◽

X Rays ◽

X Ray Diffraction ◽

Crystalline Materials ◽

X Ray ◽

Structural Characterisation ◽

Pdf Analysis

The highly-collimated, intense X-rays produced by a synchrotron radiation source can be harnessed to build high-resolution powder diffraction instruments with a wide variety of applications. The general advantages of using synchrotron radiation for powder diffraction are discussed and illustrated with reference to the structural characterisation of crystalline materials, atomic PDF analysis, in-situ and high-throughput studies where the structure is evolving between successive scans, and the measurement of residual strain in engineering components.

Download Full-text

Electric-field-induced lattice distortion in epitaxial BiFeO3 thin films as determined by in situ time-resolved x-ray diffraction

Applied Physics Letters ◽

10.1063/1.5000495 ◽

2017 ◽

Vol 111 (8) ◽

pp. 082907 ◽

Cited By ~ 2

Author(s):

Seiji Nakashima ◽

Osami Sakata ◽

Hiroshi Funakubo ◽

Takao Shimizu ◽

Daichi Ichinose ◽

...

Keyword(s):

Thin Films ◽

Electric Field ◽

Lattice Distortion ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray ◽

Bifeo3 Thin Films

Download Full-text

Green rust as a precursor for magnetite: an in situ synchrotron based study

Mineralogical Magazine ◽

10.1180/minmag.2008.072.1.201 ◽

2008 ◽

Vol 72 (1) ◽

pp. 201-204 ◽

Cited By ~ 40

Author(s):

A. Sumoondur ◽

S. Shaw ◽

I. Ahmed ◽

L. G. Benning

Keyword(s):

Direct Evidence ◽

Green Rust ◽

Stable Phase ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray ◽

Subsequent Transformation ◽

Rapid Formation ◽

Reaction Proceeds

AbstractIn this study, direct evidence for the formation of magnetite via a green rust intermediate is reported. The Fe(II) induced transformation of ferrihydrite, was quantified in situ and under O2-free conditions using synchrotron-based time-resolved energy dispersive X-ray diffraction. At pH 9 and Fe(II)/Fe(III) ratios of 0.5 and 1, rapid growth (6 min) of sulphate green rust and its subsequent transformation to magnetite was observed. Electron microscopy confirmed these results, showing the initial rapid formation of hexagonal sulphate green rust particles, followed by the corrosion of the green rust as magnetite growth occurred, indicating that the reaction proceeds via a dissolution-reprecipitation mechanism. At pH 7 and Fe(II)/Fe(III) ratio of 0.5, sulphate green rust was the stable phase, with no transformation to magnetite.

Download Full-text

Time-resolved, in situ X-ray diffraction studies of the hydrothermal syntheses of microporous materials

Microporous and Mesoporous Materials ◽

10.1016/s1387-1811(98)00009-2 ◽

1998 ◽

Vol 21 (4-6) ◽

pp. 253-262 ◽

Cited By ~ 19

Author(s):

Dermot O'Hare ◽

John S.O. Evans ◽

Robin J. Francis ◽

P. Shiv Halasyamani ◽

Poul Norby ◽

...

Keyword(s):

Microporous Materials ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray ◽

Hydrothermal Syntheses

Download Full-text

Elucidating the Structural Evolution of a Highy Porous Responsive Metal-Organic Framework (DUT-49(M)) upon Guests Desorption by Time-Resolved In-Situ Powder X-Ray Diffraction

10.26434/chemrxiv.12753593.v1 ◽

2020 ◽

Author(s):

Bikash Garai ◽

Volodymyr Bon ◽

Francesco Walenszus ◽

Azat Khadiev ◽

Dmitri Novikov ◽

...

Keyword(s):

Adsorption Isotherms ◽

Metal Organic Framework ◽

Structural Evolution ◽

Structural Transformations ◽

X Ray Diffraction ◽

Time Resolved ◽

X Ray ◽

Metal Organic ◽

Subcritical Fluid

Variation in the metal centres of M-M paddle-wheel SBU results in the formation of isostructural DUT-49(M) frameworks. However, the porosity of the framework was found to be different for each of the structures. While a high and moderate porosity was obtained for DUT-49(Cu) and DUT-49(Ni), respectively, other members of the series [DUT-49(M); M= Mn, Fe, Co, Zn, Cd] show very low porosity and shapes of the adsorption isotherms which is not expected for op phases of these MOFs. Investigation on those MOFs revealed that those frameworks undergo structural collapse during the solvent removal at the activation step. Thus, herein, we aimed to study the detailed structural transformations that are possibly occurring during the removal of the subcritical fluid from the framework.

Download Full-text

Time-resolved XRD experiments for a fine description of mechanisms induced during reactive sintering

Science of Sintering ◽

10.2298/sos0501027p ◽

2005 ◽

Vol 37 (1) ◽

pp. 27-34 ◽

Cited By ~ 7

Author(s):

S. Paris ◽

E. Gaffet ◽

D. Vrel ◽

D. Thiaudiere ◽

M. Gailhanou ◽

...

Keyword(s):

Reactive Sintering ◽

X Ray Diffraction ◽

Reaction Parameters ◽

Time Resolved ◽

X Ray ◽

Synthesis Conditions ◽

Nanostructure Materials ◽

Synchrotron Beam ◽

The One

The control of Mechanically Activated Field Activated Pressure Assisted Synthesis hereafter called the MAFAPAS process is the main objective to be achieved for producing nanostructure materials with a controlled consolidation level. Consequently, it was essential to develop characterization tools "in situ" such as the Time Resolved X-ray Diffraction (TRXRD), with an X-ray synchrotron beam (H10, LURE Orsay) coupled to an infrared thermography to study simultaneously structural transformations and thermal evolutions. From the 2003 experiments, we took the opportunity to modify the sample-holder in order to reproduce the better synthesis conditions of the MAFAPAS process, but without the consolidation step. The versatility of the setup has been proved and could even be enhanced by the design of new sample holders. In addition, this work clearly shows that this equipment will allow, on the one hand, to make progress of the understanding of MAFAPAS mechanisms and, on the other hand, to adjust reaction parameters (mechanical activation and combustion synthesis) for producing many materials with an expected microstructure.

Download Full-text