![]() Typically, general purpose curve-fitting software is used. At present, conventional peak deconvolution involves curve fitting to the observed pattern with the individual visible peaks plus a very broad, but simple, e.g., Gaussian, peak for the amorphous material. Perhaps Hermans and Weidinger (1948) were first to suggest that the area under diffraction peaks be divided by the total area. Another approach, peak deconvolution, is more effort to carry out and to attribute. It had 4871 citations as of this writing, despite frequent use with no attribution or with only citations of secondary publications. The most prevalent, and by far the simplest, is the Segal peak height method (Segal et al. Several diffraction methods are used to analyze cellulose crystallinity (Thygesen et al. First, a brief review of diffraction crystallinity methods. Two papers in this issue mark a transition in general understanding of cellulose crystallinity analysis. polarisation to actually ‘show’ stress in transparent materials.Abstract: Crystallinity analysis is important for practical reasons and related research can offer information on the nature of amorphous cellulose. So X-ray diffraction is a technique to demonstrate mechanical stress in crystalline materials. Stress can result in broader peaks as well as in peak displacement towards a larger or smaller crystal plane spacing. After all, atoms in the lattice – and therefore crystal planes as well – are slightly pulled apart or squeezed together under stress. X-ray diffraction also allows you to check whether a material is subjected to mechanical stress. With a certain preferred orientation, certain crystal planes will reflect X-rays much more often than in the case of a random orientation, so that the peak associated with that crystal plane becomes larger. For a polycrystalline material, you can also say something about the crystallite size – smaller crystallites cause broader peaks – or about a possible preferred orientation of the crystallites. Using X-ray diffraction, you can determine so much more than only the crystal structure. X-ray diffraction can be carried out with single crystals, but also with polycrystalline materials that are ground into powders. For many known crystals, these patterns are available in a library, and by comparing a newly recorded diffraction pattern with the patterns in the library, you can find out which crystalline material you are dealing with. This X-ray diffraction pattern is characteristic for the crystal structure, a fingerprint indeed. A recorder measures the intensity of the reflected radiation, and this is expressed in a pattern with peaks at certain angles (2θ) or crystal plane distances. If you bombard a stationary crystal with X-rays from different incident angles, then there will be different crystal planes, each with their own crystal plane spacing, that successfully reflect the X-rays. This happens at a suitable combination of the incident angle θ under which the X-rays hit the plane, the wavelength λ of this radiation and the spacing d between adjacent lattice planes. In most directions, these reflected rays cancel each other, but in certain directions they reinforce each other. Where a normal mirror reflects visible light, the crystal planes act as a mirror for X-rays. This is radiation with a wavelength of about 1 Angstrom (10 -10 m), in the same order of magnitude as the distance between atoms in a crystal. You do this by bombarding the material with X-rays. X-ray diffraction (XRD) is an analysis technique to determine the crystal structure of crystalline materials. ![]()
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