Graphite crystal, diffraction

Eig. 1. Laue x-ray diffraction pattern of a single natural graphite crystal. 

The phase composition of catalysts was studied by X-ray diffraction [XRO) technique. XRD spectra were recorded by using a Phillips 17D0 powder diffractometer equipped with a graphite crystal monochromator and CuK radiation. 

Yb-ln-Sb. The ternary YbsI Sbe compound was obtained from a direct element combination reaction in a sealed graphite tube at 973 K, and its crystal structure was determined by X-ray single crystal diffraction methods. It crystallizes in the Ba5ln2Sb6 structure type with a unit cell of a = 0.73992, b = 2.3001, c = 0.45139 (Kim et al., 2000). 

Figure 5.3. SEM images of cross-section of the samples that were shock-compressed (a) perpendicularly and (b) parallel to the basal plane of the graphite crystal structure. The former and latter will be abbreviated to postshock sample I and II, respectively, (c) and (d) Cross-sectional schemes 1, copper capsule 2, sample. The parts designated as - in the schemes were analyzed by SEM and HREM observations and the X-ray diffraction method. Capital letters A, B, and C represent the upper, middle, and lower parts, respectively. The direction of shock wave propagation is downward.

FIG. 3 Electron diffraction patterns from individual microtubules of graphitic carbon. The patterns show mm2 symmetry, and are indexed by multiple superpositions of hO/ -type reflections and hM reflections of graphite crystal. The needle axes are horizontal, a, Superposition of three sets of [hkO] spots taken from a seven-sheet tubule, b, Superposition of four sets of hkO) spots from a nine-sheet tubule. 

The increase in preferred orientation on stretching [121] is accompanied by an increase in crystal size in the direction of the c-axis, measured by the parameter L, was obtained by measuring the line broadening of the graphite (002) diffraction arc. The results for different stretch ratios and temperatures are given in Table 5.14. 

X-Ray Diffraction Studies on Carbon and Graphite, W. Ruland Vaporization of Carbon, Howard B. Palmer and Mordecai Shelef Growth of Graphite Crystals from Solution, S. B. Austerman... 

X-ray diffraction (XRD) patterns were obtained by a Siemens D 500 powder diffractometer equipped with a graphite crystal monochromator using a Copper Ka X-ray radiation source. Experiments were run in step-scan mode witii a step interval of 0.02° 2e and a count rate of 1 second per step over the range 5° to 90° 20. The fraction of tetragonal to monoclinic form was determined by Rietveld method [11,12] while the crystallite size was determined by Warren-Averbach X-ray broadening method [13],... 

The X-ray diffraction signal from the (001) reflection which is usually absent in the spectrum of perfect graphitic crystals may exist in the spectra of carbons composed of quasi-graphitic domains and those with high concentration of two-dimensional defects. The latter Get us mark it for brevity as F-component... 

The carbonized material is often called amorphous or baked carbon . It is without long-range crystalline order and the deviation of the interatomic distances of the carbon atoms (from the perfect graphite crystal) is greater than 5% in both the basal plane ab directions) and between planes (c direction), as determined by x-ray diffraction. 

Artifacts produced by terminatioii are most often in the form of spurious P(x) peaks or a loss of resolution that prevents peak separation. An interesting example is given in the literature [11]. The authors calculated P(x) for a graphite crystal limiting artificially I(s) at s = 1 (the range of selected area diffraction patterns) which is a strong termination effect. They thus demonstrated the production of spurious peaks. 

X-Ray Diffraction Studies on Carbon and Graphite, W Ruland Vaporization of Carbon, Howard B. Palmer and Mordecai Shelef Growth of Graphite Crystals from Solution, S. B. Austerman Internal Friction Studies on Graphite, T. Tsuzuku and M. H. Saito The Formation of Some Graphitizing Carbons, J. D. Brooks and G. H. Taylor Catalysis of Carbon Gasification, P. L. Walker, Jr., M. Shelef, and R. A. Anderson... 

IG-21 was recrystallized from ethyl acetate to give colorless crystals (0.30 mm x 0.20 mm x 0.20 mm) suitable for X-ray single-crystal diffraction. The crystal structure of IG-21 was recorded on a Smart Apex CCD diffractometer using graphite monochromated MoKa radiation (A = 0.071073 nm). In the range of... 

Jin x-ray monochromator. A monochromator is a large single crystal (usually graphite) that is oriented so that a very iatense reflection is directed toward the sample. AH wavelengths are absorbed by the monochromator except a small range of wavelengths used for the diffraction experiment. Usually only the characteristic radiation is used if an x-ray tube is the x-ray source. 

Crystal Structure. Diamonds prepared by the direct conversion of well-crystallized graphite, at pressures of about 13 GPa (130 kbar), show certain unusual reflections in the x-ray diffraction patterns (25). They could be explained by assuming a hexagonal diamond stmcture (related to wurtzite) with a = 0.252 and c = 0.412 nm, space group P63 /mmc — Dgj with four atoms per unit cell. The calculated density would be 3.51 g/cm, the same as for ordinary cubic diamond, and the distances between nearest neighbor carbon atoms would be the same in both hexagonal and cubic diamond, 0.154 nm. 

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