X-ray diffraction study of the strains in the texture of Ca(OH)₂at the transition zone of concrete

Abstract

At present ideal method for the dislocation density determination does not exist. Actual techniques are destructive or require a long time. The aim of our works is development of the express non-destructive method allowing to detem1ine the dislocation density with high accuracy. Another purpose is expe1imental testing of different modern theories of diffraction in real single crystals.Gamma-ray diffractometry method has been applied for investigations of the quartz single crystals, containing dislocations with wide range of their density. Strictly mathematically the problem of the dynamical scattering in dislocationcontaining single crystals is not solved yet. The method based on the statistical dynamical theory of diffraction seems to be fruitful. Unfortunately primary theory proposed by Kato can lead to inaccurate results in certain cases. Modifications of this theory so far have been applied to rather pe1fect dislocationless silicon single crystals. In present work they are propagated to dislocation-containing, more imperfect quartz crystals, which permits to can-y out experimental testing of the different versions of the statistical dynamical theory of diffraction.Data obtained by means of this technique have been compared with those obtained by other methods (X-ray topography, etching channel counting). Developed technique allows to determine ve1-y low dislocation density with high accuracy (a few dislocations I c.cm). To study the influence of plastic deformation on the structure of point defect in the intermetallic compound NiAl, the advantage of Laue method, its full spectral exposure, and advantages of the image plate, its high sensitivity, wide dynamic range and high counting rate, are combined. Furthem1ore, back reflection exposure is chosen to avoid sample modification, so that the real deformation effect can be observed.Laue method is a laboratory routine to determine crystal orientation and to study disorders, such as grain structure and mosaic spread. However, it is not so straight forward to get structure factor with Laue method. The measured intensity must be normalized with some extra factors, such as spectral intensity of incident radiation, spectral sensitivity of the detector. and readout efficiency, besides well known factors, such as polarization factor, Lorentz factor, temperature factor and absorption factor. The solution is further hindered by the so called multireflection problem. Since many of, if not most of, strong low index reflections are involved in multiplicity, it is necessary to deconvolute energy overlap. It is achieved experimentally either by rotating sample or by changing tube voltage.For samples like NiAl which acquire high symmetry, it is possible to get a quite complete intensity data set on a single exposure. Fourier synthesis is then carried out with structure factors thus extracted and electron distribution map is plotted to show some features of point defect configuration. Even if the data set is not so complete, by comparing measured structure factors with that cal...

X-ray interference topography investigation of Si/GexSi1 x/Si(001) heterosystem

“…Thus, the intensity variation up to 0.2 (see the left step of 3 nm high in figure 1(b)) cannot be explained in the framework of the models [20]. Note that the observed contrast peculiarities are fundamentally different from those investigated in [21,22], since the thickness of the intermediate layer is far less than 0 .…”