Molybdenum powder pattern

Several other methods for preparing molybdenum disulfide have been reported in the literature, but caution should be exercised in assigning a particular crystal modification to the materials obtained on the basis of powder diagrams1 s. Such materials often show stacking faults thereby, the powder patterns show differences from those of natural molybdenite15. ... 

FIGURE 5.17 Cellulose diffraction patterns. Top left synchrotron radiation x-ray diffraction pattern for cotton fiber bundle. The fiber was vertical and the white circle and line correspond to a shadow from the main beam catcher and its support. (Credit to Zakhia Ford.) Top right electron diffraction pattern of fragments of cotton secondary wall. The much shorter arcs in the top right figure are due to the good alignment and small number of crystallites in the electron beam. (Credit to Richard J. Schmidt.) Bottom a synthesized powder pattern for cellulose, based on the unit cell dimensions and crystalline coordinates of Nishiyama et al. [209]. (Credit to Zakhia Ford.) Also shown are the hkl values for the Miller indices. The 2-theta values are for molybdenum radiation instead of the more commonly used copper radiation. 

Figure 7.17 contains the XRD pattern for the precursor molybdenum powder. Although the XRD pattern for the black powder in Figure 7.18 contained peaks for unreacted molybdenum that correspond to those in Figure 7.17, no unreacted nickel was detected. Molybdenum and nickel carbide peaks were both present. The XRD pattern of the light gray powder is shown in Figure 7.19. Although nickel and molybdenum carbides are again present, less unreacted molybdenum was present than in the black powder. The cause of reaction of molybdenum with the carbide powder in the presence of nickel is unclear. Recall that in the absence of nickel, molybdenum processed for 1 h reacted only minimally at the surface.

Figure 1. Powder X-ray diffraction patterns for the mesostructured lamellar molybdenum sulfides (a) M0S-L-I6C, (b) MoS-L-14C and (c) MoS-L-12C.

X-ray Diffraction of Pure MoFe, High Temperature Form. X-ray diffraction powder photographs of MoFe taken at 10 °C. can be indexed on the basis of a body-centered cubic unit cell with a lattice constant, a = 6.23 zb 0.01 A. The similarity of the MoFe diffraction pattern to that of molybdenum metal indicates that the molybdenum atoms in the hexafluoride, as in the metal, are located at the body center and comers of a cube. 

The Powder Diffraction File search was unsuccessful and therefore, further analysis and a structure solution were undertaken. Thermogravimetric analysis in an oxygen atmosphere reveals sharp 7.3 wt. % weight loss at 300°C and the powder diffraction pattern, collected from a solid residue after the TGA, confirms the formation of molybdenum oxide, M0O3. Assuming the following decomposition reaction ... 

The plutonium-bearing precipitate obtained from nitric acid solutions (containing molybdenum, zirconium and plutonium) gives an X-ray powder diffraction pattern not distinguishable from that of ZrMo207(0H)2(H20)2 precipitated without plutonium. However, since the Pu content is low, the Pu could be present either in the Pu molybdate structure or replacing Zr in the Zr molybdate structure and not be detected in the X-ray patterns. 

The classical photographic method for recording powder diffraction patterns is still used, particularly when the amount of sample is small. I hc most common instrument for this purpose is the Dehyc-SchernrpovjdcT camera, which is shown schematically in Figure 12-17a. Here, the beam from an X-ray lube is filtered to produce a nearly ntonochromalic beam (often the copper or molybdenum Ka line), which is collimated by passage through a narrow tube. 

FIGURE 7.18 XRD pattern of black product from hour-long reaction among nickel, molybdenum, and carbon black powder in argon M02C, Mo, NijC, Ni3Mo. 

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