Graphite powder diffraction pattern

The structure refinement program for disordered carbons, which was recently developed by Shi et al [14,15] is ideally suited to studies of the powder diffraction patterns of graphitic carbons. By performing a least squares fit between the measured diffraction pattern and a theoretical calculation, parameters of the model structure are optimized. For graphitic carbon, the structure is well described by the two-layer model which was carefully described in section 2.1.3. 

X-ray Powder Pbotograidiy. X-ray powder diffraction patterns of solid samples were obtained with an Enraf apparatus (Delft, Holland), using graphite-monochromatized Cu Ko radiation. A finely powdered sample was sealed into 0.5-mm quartz capillaries as described for Raman spectroscopy. 

X-ray powder diffraction patterns were obtained with a Philips AFD 3600 diffractometer (graphite monochrometer and theta-compensating silts) using Cu-Ka radiation and a scan rate of 2 deg 20 mln l The reported line positions were corrected using an Internal silicon standard (SRM-640b). Y-123 concentrations were calculated by... 

The product is a microcrystalline black powder with a graphitic character. The powder diffraction pattern has been reported by Beckmann et al. Grinding tends to introduce some stacking disorder into the material and broadens reflections associated with the hkl h + k jtQ) lines in the powder... 

Doping of alkali-metals into CNTs has been examined [11]. The X-ray powder diffraction (XRD) patterns of the K- or Rb-doped CNTs show that alkali-metals are intercalated between the CNT layers. The hexagonal unit cell is essentially the same as that of the stage-1 alkali-metal intercalated graphite ACg (A=K, Rb). For a sample doped with Rb, the observed lattice parameter of the perpendicular... 

Some other situation is realized in a case of TEG-tin CMs. Electron microscopy studies of the obtained TEG-Sn powders revealed the uniform coverage of TEG surface by tin particles. Tin particles are of spherical shape and their sizes are about 40-80 nm, i.e. somewhat higher than in a case of silicon particles. Low scatter of particle sizes is observed as in a case of TEG-silicon system. However, as it is clearly seen from the data of the X-ray structure analysis (Figure 4) tin particles deposited on the surface of graphite support are in crystalline state. The distinct and narrow tin reflections at the X-ray diffraction pattern evidence this fact. 

Typical X-ray diffraction patterns of three different carbon powder samples are shown in Fig. 3. Two 00/ and two hkO diffraction peaks can be distinguished in the patterns of samples produced at 800°C and 1000°C. The 002 (26 26.9°) and 004 (26 54.9°) peaks correspond to the parallel graphene layers. The 100 (26 43°) and 110 (26 77.8°) diffraction peaks are characteristics of the 2D in-plane symmetry along the graphene layers. Based on its XRD pattern, the powder synthesized at 500°C is not graphitized, which is in agreement with Raman analysis. This low temperature sample also contains traces of iron chlorides. 

Figure 10. Elastic neutron diffraction pattern from a 0.4-layer nitric oxide film adsorbed on a recompressed graphite powder Papyex (431. Background scattering from the substrate has been subtracted. The molecules are assumed to be lying down as shown in the unit cell (inset). The arrows indicate the position and relative intensities of the Bragg peaks calculated for this structure.

The first tasks of the work described in this paper were to define the chemical compositions of the vacuum-stable products derived from the interaction of graphite with AsF, AsF, mixed with F2, and OjAsF,. The second tasks were to explain the peculiar features of the X-ray powder diffraction (XRPD) pattern for the stage-one C,4AsF, (/, a 7.6 A). A novel structure involving fluoride ligand nestling of the AsF," in the hexagonal depressions of the carbon atom sheets is proposed. 

The relative crystallinity and framework compositions were estimated from XRD measurements. Powder X-ray diffraction patterns were obtained with a PW-1130 Philips diffractometer with Ni-filtered CuKa source and a graphite monochromator. The relative crystallinity of the preheated samples, y / is reported as the ratio between the peak heights measured for the sample heated to a predetermined temperature for 2 h and for the sample activated at 400°C. In these calculations (530) and (150) reflections were chosen for faujasites and mordenites, respectively. The number of framework A1 atoms in the unit cell (Nai) was calculated from the lattice parameters according to the equations described in [1,2]. Lattice parameters were determined in the presence of a 10% Y2O3 internal standard for faujasites and a 10% Si internal standard for mordenites. 

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