Real-time powder diffraction studies of energy materials under non-equilibrium conditions

Energy materials form the central part of energy devices. An essential part of their function is the ability to reversibly host charge or energy carriers, and analysis of their phase composition and structure in real time under non-equilibrium conditions is mandatory for a full understanding of their atomic-scale functional mechanism. Real-time powder diffraction is increasingly being applied for this purpose, forming a critical step in the strategic chemical engineering of materials with improved behaviour. This topical review gives examples of real-time analysis using powder diffraction of rechargeable battery electrodes and porous sorbent materials used for the separation and storage of energy-relevant gases to demonstrate advances in the insights which can be gained into their atomic-scale function.

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1D to 2D Na-Ion Diffusion Linked to Structural Transitions in Na0.7CoO2

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314096363 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C363-C363

Author(s):

Marisa Medarde ◽

Mattia Mena ◽

Jorge Gavilano ◽

Ekaterina Pomjakushina ◽

Jun Sugiyama ◽

...

Keyword(s):

Solid State ◽

Structural Similarity ◽

Clean Energy ◽

Rechargeable Batteries ◽

Atomic Scale ◽

Structural Transitions ◽

Ion Diffusion ◽

Energy Materials ◽

Energy Devices ◽

Neutron Powder Diffraction Data

One of the most important scientific problems faced by our society is how to convert and store clean energy. In order to achieve a significant progress in this field we need to understand the fundamental dynamical processes that govern the transfer of energy on an atomic scale. For many energy devices such as solid-state batteries and solid-oxide fuel cells, this means understanding and controlling the complex mechanisms of ion diffusion in solid matter. Because of the unusual evolution of correlated electronic properties (frustrated magnetism and superconductivity), the layered Co-oxide family NaxCoO2 (0<x<1), object of this work, has been extensively studied during the last decade. More recently it has also attracted the attention of applied sciences, mainly because of its structural similarity with LixCoO2, one of the most common Li-ion battery electrodes. In view of the larger abundance of Na in the earth crust with respect to Li, Na-ion batteries enjoy an increased attention. Hence we decided to investigate the Na-ion diffusion in this material, whose possible use as cathode for solid-state rechargeable batteries has recently been proposed [1]. The present study reports the observation of a crossover from quasi-1D to 2D Na-ion diffusion in Na0.7CoO2. High resolution neutron powder diffraction data indicate the existence of two structural transitions at T1=290K and T2=400K [2]. We present here evidence indicating that both transitions are closely related to changes in the Na-ion mobility. Analysis of the anomalies in the Na-Na distances, the Debye-Waller factors and the scattering density in the paths connecting neighbouring Na sites strongly suggest that Na-ion diffusion starts at T1, although for T1<T<T2 it occurs preferentially along quasi-1D paths. A fully isotropic diffusion is only observed for T>T2, coinciding with the equalization of all first-neighbor Na-Na distances in the structure [2]. These findings provide new insight on the subtle mechanisms controlling the Na-ion diffusion in the NaxCoO2 family and could be used for the design of related energy materials with improved functional properties. Fig. 1. Fourier difference maps of the z = 0.25 Na planes at T = 50, 320 and 450 K showing the evolution of the residual scattering density in the paths connecting the Na1 and Na2 sites (from ref.[2]).

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Real Time Analytical Linearization of Turbofan Engine Model

Volume 4: Ceramics; Concentrating Solar Power Plants; Controls, Diagnostics and Instrumentation; Education; Electric Power; Fans and Blowers ◽

10.1115/gt2013-94464 ◽

2013 ◽

Author(s):

Gi-Yun Chung ◽

J. V. R. Prasad ◽

Manuj Dhingra ◽

Richard Meisner

Keyword(s):

Real Time ◽

Linear Model ◽

Separate Flow ◽

Computational Effort ◽

Primary Control ◽

Equilibrium Conditions ◽

Turbofan Engine ◽

Engine Model ◽

Analytical Expressions ◽

Non Equilibrium

This paper presents a methodology for developing a control oriented analytical linear model of a turbofan engine at both equilibrium and non-equilibrium conditions. This scheme provides improved accuracy over the commonly used linearization method based on numerical perturbation. Linear coefficients are obtained by evaluating at current conditions analytical expressions which result from differentiation of simplified nonlinear expressions. Residualization of the fast dynamics states are utilized since the fast dynamics are outside of the primary control bandwidth. Analytical expressions based on the physics of the aerothermodynamic processes of a gas turbine engine facilitate a systematic approach to the analysis and synthesis of model based controllers. In addition, the use of analytical expressions reduces the computational effort, enabling linearization in real time at both equilibrium and non-equilibrium conditions to enable more accurate capture of system dynamics during aggressive transient maneuvers. The methodology is formulated and applied to a separate flow twin spool turbofan engine model in the Numerical Propulsion System Simulation (NPSS) platform. The derived linear model is validated against the full nonlinear engine model.

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Real time study of wet-chemical reaction dynamics at beamline P02.1 @ PETRA III

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314091414 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C858-C858

Author(s):

Ann-Christin Dippel ◽

Jan Torben Delitz ◽

Hanns-Peter Liermann ◽

Christoffer Tyrsted ◽

Dipankar Saha ◽

...

Keyword(s):

High Resolution ◽

Real Time ◽

Powder Diffraction ◽

Structural Changes ◽

Reciprocal Space ◽

Atomic Scale ◽

Polycrystalline Materials ◽

Total Scattering ◽

X Ray ◽

Wet Chemical

The high brilliance synchrotron light source PETRA III in Hamburg, Germany, provides a dedicated X-ray powder diffraction beamline called P02.1 [1]. It is a side station to the hard X-ray diffraction beamline and runs at a fixed photon energy of 60 keV. Its dispersive monochromator produces a highly collimated photon beam of very narrow energy bandwidth and high intensity. These excellent beam characteristics turn P02.1 into an ideal instrument for many different kinds of experiments, ranging from high resolution powder diffraction of polycrystalline materials for structure solution and refinement or microstructure analysis, to the study of nanocrystalline and disordered materials to determine their local structure. In particular, it is the scope of P02.1 to study dynamic processes such as chemical and crystallographic transitions under non-ambient conditions in real time. For this purpose, the beamline is equipped with a large and fast area detector which enables sub-second time-resolution. The accessible range in reciprocal space is beyond Q = 30 Å-1. Hence, P02.1 is a powerful tool for total scattering experiments as it provides high resolution in real and reciprocal space which are determined by the max. Q and the instrumental resolution, respectively. This presentation describes some recent experiments carried out at P02.1 that relate to pair distribution function (PDF) and total scattering analysis. The focus will be on the investigation of structural changes on the atomic scale during the wet-chemical synthesis of nanoparticles, e.g. in the system ZrO2. By means of evaluating the changes of bond distances and atomic coordination on a time scale of seconds, it is possible to describe the molecular structure of intermediates and, thus, to deduce the underlying reaction mechanism. On the basis of this information, synthesis processes may be optimised with respect to tuning the properties of the product and to maximize its yield.

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An Interactive Minicomputer Program for the Indexing and Simulation of Electron Diffraction Patterns

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100092670 ◽

1976 ◽

Vol 34 ◽

pp. 542-543

Author(s):

R.P. Goehner ◽

W.T. Hatfield ◽

Prakash Rao

Keyword(s):

Electron Diffraction ◽

Real Time ◽

Pattern Analysis ◽

Flow Diagram ◽

Hard Copy ◽

Time Analysis ◽

Real Time Analysis ◽

Transmission Electron ◽

One Step ◽

Diffraction Patterns

Computer programs are now available in various laboratories for the indexing and simulation of transmission electron diffraction patterns. Although these programs address themselves to the solution of various aspects of the indexing and simulation process, the ultimate goal is to perform real time diffraction pattern analysis directly off of the imaging screen of the transmission electron microscope. The program to be described in this paper represents one step prior to real time analysis. It involves the combination of two programs, described in an earlier paper(l), into a single program for use on an interactive basis with a minicomputer. In our case, the minicomputer is an INTERDATA 70 equipped with a Tektronix 4010-1 graphical display terminal and hard copy unit.A simplified flow diagram of the combined program, written in Fortran IV, is shown in Figure 1. It consists of two programs INDEX and TEDP which index and simulate electron diffraction patterns respectively. The user has the option of choosing either the indexing or simulating aspects of the combined program.

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