xrd的三维分析

Preface In nature most materials, such as rocks, ice, sand and soil, appear to be aggregates composed of a set of crystalline elements. Similarly, modern society is built on applications of metals, ceramics and other “hard materials”, which also are polycrystalline. So are drugs, bones and trace particles relevant to environmental matters, as well as many objects of artistic or archaeological significance. Remarkably, until recently, no nondestructive method existed for providing comprehensive three-dimensional information on the structure and dynamics of polycrystals at the scale of the individual elements (the grains, subgrains, particles or domains). X-ray and neutron diffraction have been confined to two limiting cases: powder diffraction, which averages over elements, and diffraction performed on single crystals. Most real-world materials occur as heterogeneous aggregates with substantial internal structure, and thus fall between these two extremes. Local information has been provided by tools such as optical, electron, ion beam and scanning probe microscopy. However, these methods probe the near-surface regions only. Hence, the characterization is only two-dimensional and prohibits studies of bulk dynamics. Three-dimensional x-ray diffraction (3DXRD) is a novel experimental method for structural characterization of polycrystalline materials. It is based on two principles: the use of highly penetrating hard x-rays from a synchrotron source and a “tomographic” approach to the acquisition of diffraction data. Uniquely, the method enables a fast and nondestructive characterization of the individual microstructural elements (grains and sub-grains) within millimeter-to-centimeter-sized specimens. The position, morphology, phase and crystallographic orientation can be derived for hundreds of elements simultaneously, and the elastic and plastic strains can also be derived. Furthermore, the dynamics of the individual elements can be monitored during typical processes such as deformation or annealing. Hence, for the first time, information on the interaction between elements can be obtained directly. The provision of such data is vital if we are to extend our knowledge beyond the current structural models. The aim of this book is to give a comprehensive account of 3DXRD microscopy, with a focus both on methodology and on applications. The methodology is presented from a geometric/crystallographic point of view, but with VIII Preface sufficient details of algorithms and hardware to enable the reader to plan his or her own 3DXRD experiments and analyze the resulting data. The main applications are introduced by a short preamble, intended to motivate the use of 3DXRD. To underline the prospects for 3DXRD, a number of untested suggestions for methodological improvements and alternative applications are included. The book is written for a general reader who has a background in the natural sciences and a basic understanding of x-ray diffraction. For historical reasons, the majority of the applications presented relate to materials science. However, as the structure of polycrystals is of more general interest it is my hope that the book may serve to stimulate research in other fields also, such as geophysics, geology, chemistry and pharmaceutical science. Synchrotron instrumentation requires, by its nature, a collaborative effort. Hence, I welcome this opportunity to thank the group of people who have contributed towards the development of 3DXRD methodology. These include Jacob Bowen, Xiaowei Fu, Stephan Garbe, Carsten Gundlach, Dorte Juul Jensen, Erik Knudsen, Axel Larsen, Erik Mejdal Lauridsen, Torben Lorentzen, Lawrence Margulies, Søren Fæster Nielsen, Wolfgang Pantleon, Søren Schmidt, John Wert and Grethe Winther at Risø; Erik Offerman and Jilt Sietsma at the Technical University of Delft; Robert Suter at CMU; Rene Martins at GKSS; and, last but not least, Ulrich Lienert at the APS. The development of the method into the 3DXRD microscope at ESRF was only possible thanks to the dedication and expertise of the in-house staff, in particular Andy Goetz, ˚Ake Kvick and Gavin Vaughan from beamline ID11. The Danish National Research Foundation is gratefully acknowledged for supporting “Center for Fundamental Research: Metal Structures in Four Dimensions”. The work presented in this book would not have been possible without the pioneering studies in hard x-ray diffraction by Jochen Schneider. Furthermore, for numerous very valuable discussions, I thank Roger Doherty, Niels Hansen, Gabor Herman, Veijo Honkim¨aki, Torben Leffers, Wolfgang Ludwig, Adam Morawiec and Jan Teuber. Finally, I’m grateful to Roger Doherty, Dorte Juul Jensen and Brian Ralph for reading and discussing this manuscript. Roskilde, July 2004 Henning Friis Poulsen