diffraction de rayons X sur poudres

CONT: Diffraction de rayons sur poudres : analyse quantitative de composés modèles du ciment anhydre. [...] Ce stage sera consacré à la caractérisation par diffraction des rayons X de mélanges d'alites de synthèse M1 et M3. La méthode expérimentale utilisée sera la diffraction des rayons X sur poudres jointe aux autres méthodes de laboratoire associées.
CONT: À l'aide de la diffraction de rayons X de poudres, différentes formes polymorphiques peuvent être détectées pour des molécules à activité pharmacologique.

CONT: X-ray powder diffraction is used in the identification of crystalline phases in unknown samples, finding the lattice parameter and other lattice related information, quantitative determination of phases in multiphase samples, finding the orientation in single crystals, and stereographic projections. The samples must be crystalline solids such as metals, ceramics, rocks etc. These samples are usually about 1 mg in size. If the sample fits in the sample holder then there is no preparation necessary otherwise the sample may have to be crushed in order to fit. The sample takes less than one hour to be analyzed for qualitative analysis in major phases and up to 16 hours for trace phases. The quantitative analysis can take several minutes to several hours after set up. There are several detectors used in XRPD varying from films to cameras to diffractometers.
CONT: Powder X-Ray Diffraction. Powders of crystalline materials diffract X-Rays. A beam of X-rays passing through a sample of randomly-oriented micro-crystals produces a pattern of rings on a distant screen. Powder X-Ray diffraction provides less information than single-crystal diffraction, however, it is much simpler and faster. Powder X-Ray diffraction is useful for confirming the identity of a solid material and determining crystallinity and phase purity. Modern powder X-Ray diffractometers consist of an X-Ray source, a movable sample platform, an X-Ray detector, and associated computer-controlled electronics. The sample is either packed into a shallow cup-shaped holder or deposited as a slurry onto a quartz substrate, and the sample holder spins slowly during the experiment to reduce sample heating. The X-Ray source is usually the same as used in single-crystal diffractometers, Mo or Cu. The X-Ray beam is fixed and the sample platform rotates with respect to the beam by an angle theta. The detector rotates at twice the rate of the sample and is at an angle of 2 theta with respect to the incoming X-Ray beam.
CONT: Fine particles such as clays must be separated from larger particles and measured separately if they are to be detected properly. To reduce errors associated with preferred orientation of minerals, samples are most commonly ground to a powder before analysis, a technique known as powder X-ray diffraction.