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Unformatted text preview: UNIVERSITY OF CALIFORNIA, DAVIS Department of Chemical Engineering and Materials Science EMS 162L: Structure and Characterization of Materials Laboratory Winter 2010 X-RAY DIFFRACTION OF UNKNOWN POWDER Purpose : The purpose of this laboratory is to give you the opportunity to interpret powder x-ray diffraction data. You will identify an unknown material (Bravais lattice, lattice parameter, and chemical formula) based on the peaks observed in the x-ray diffraction spectra and you will identify the ratio of powders in the mixture using the reference intensity ratio method. Equipment and Safety : The equipment you will be using in this laboratory is a Scintag XDS 2000 x-ray diffractometer. The x-rays are generated by a 2.2kW and typical operating conditions of -45kV and 40 mA. Because you will not be officially certified to use the equipment and will not be issued dosimetry, you will not be permitted to place your hands or any other part of your body inside the diffractometer and you must be accompanied by a certified user at all times. You will be permitted to observe the diffractometer while in operation and to control the diffractometer via the computer interface. Samples : The samples for this lab will consist of pure unknown powder sample and one powder sample which is a mixture of two powders. One of the mixture powders is α-iron (Fe) powder which we had previously x-rayed. Procedure : 1. Carefully measure a small amount of the powder mixture and place it in the recess in the square holder. Be careful while handling the powders as they can pose a minor hazard due to the fine particle size. 2. Ensure that the powder is densely compacted into the holder, but be careful not to impose a texture (preferential alignment) to the powder. Use a glass slide to ensure a level surface with the top of the square holder. 3. The TA will load your sample into the diffractometer for you. 4. Perform a scan of the sample at a slow scan rate (1-5 degrees/minute) to obtain a high quality scan from 40 – 100 degrees using the Ni filter. Using the PDF card for α-iron identify the peaks that result from α-iron and those from the unknown powder. With these 2 θ values, you can identify the unknown powder. Powder Diffraction Files: The International Centre for Diffraction Data (ICDD ®) is a non-profit scientific organization dedicated to collecting, editing, publishing, and distributing powder diffraction data for the identification of crystalline materials. Figure 1 shows the powder diffraction file (PDF) card for corundum. Figure 1 shows the powder diffraction file (PDF) card for corundum....
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- Spring '08
- Crystallography, unknown powder, Prof. Kim