Diffraction traces

Fig. 6. X-ray diffraction traces vs ball milling (mechanical alloying) for Alg5Ni5Fe2Gdg at A, 2 h B, 5 h C, 20 h and D, 80 h. After 80 hours of milling the...

Powder X-ray diffraction traces (not illustrated) confirmed (i) the presence of a crystalline mica impurity which degraded rapidly with milling time and (ii) that the kaolin became less crystalline as the milling time progressed but that the diagnostic 001 and 002 peaks were still present (at much reduced intensity) after 30 minutes milling. 

Figure 5. Typical X-ray diffraction traces of the (001) reflection for mica and mica-illite minerals. Assymmetry is shown towards large values. A - natural 2M muscovite B = natural illite (IMd) C - synthetic illite (lMd), 75% mica, 25% prophyllite composition D = synthetic 1M muscovite E - natural 1M glauconite F = synthetic 1M celadonite mica.

Figure 5.6. X-ray diffraction trace obtained from a multilayer of poly (octadec-l-ene-maleic anhydride). (Reproduced from Tredgold, R.H., Vickers, A.J., Hoorfar, A., Hodge, P. and Khoshdel E. 1985 J. Phys. D Appl. Phys. 18 1139-45 by kind permission of the Institute of Physics).

Crystallinity. Diffraction traces of the cellulosic materials are presented in Figures 1-4. Table I lists the crystallinity indices obtained from the diffraction patterns. Also included in Table I are the crystallite sizes of the unmilled materials obtained from measurement of the half widths of the 002 reflections. The 002 reflection is noticeably sharper in the case of the cotton cellulose. Crystallite size measures 54 A for the cotton cellulose compared to an average of 29 A from the wood celluloses. 

Figure IS. Size and distortion separation. Integral breadth iss against l2 for the 001 reflections of carbon fiber and graphite whisker. Electron diffraction traces with 001 reflections resolved from hkO reflections.

The four major steps required to analyse a simple X-ray diffraction trace have been identified and illustrated by appropriate examples. Correction and normalisation of an X-ray diffraction trace are best carried out over as wide a range of two theta as possible with the normal geometrical corrections for fibres. 

Methods for estimating lattice distortion generally require two or more orders of a particular reflection to be present, and most polymers have only one order available. A method for estimating both crystallinity and lattice disorder, which does not need higher orders of a reflection, and indeed takes into account the whole of the diffraction trace, is that due to Buland (27). This method has been applied to many different fibres by Sotton and his colleagues, who have discussed their results both here (28) and elsewhere (12). The major problem with Ruland s method is that an arbitrary separation of the crystalline scatter from the non-crystalline scatter must be made other restrictions are that the method cannot be used to measure crystallite size and cannot give any indication of the presence of paracrystalline or intermediate-phase material. 

These revolutionary ideas lead to further neutron measurements of the structure of zeolite A, which have confirmed the correctness of the traditional 4 0 ordering scheme.58 59 Neutron diffraction traces for several samples of a dehydrated Na zeolite A with Si to A1 ratios of 1.03, 1.09 and 1.12 failed to show any rhombohedral distortions similar to those reported in ref. 57, and in each case the data was consistent with a cubic structure.58 Neutron diffraction experiments on a T1 exchanged sample of the same Na zeolite that had shown the rhombohedral distortion in ref. 57 showed that the crystals now had cubic symmetry59 60 and therefore the distortion that had been measured for the Na zeolite A must be very sensitive to the identity of the exchangeable cations. Profile refinement of this neutron data56 57 also showed a pronounced bimodal distribution of the bond lengths as would be predicted by the 4 0 model. In conclusion it appears that the chemical shifts observed in the n.m.r. experiments can be influenced by factors such as local strain, as well as by the local environment of each Si atom. 

Figure 5.14 Superimposed x-ray diffraction traces for the base glass composition after heat treating to specified temperatures. Front to back 502°C, 600°C, 660°C, 680°C, 725°C, 740°C, 760°C, 785°C, 800°C, 815°C, 820°C, 840°C, 850°C, 865°C, 925°C, 940°C, 980°C, 1000°C. Phases q=quartz, f=feldspar, c=calcite, n=soda ash, d=dolomite, o=calciurn oxide, m=sodium metasilicate, g=magnesium oxide.

FIGURE 3.5 A selection of the diffraction traces observed in the D17 experiment. Incident wavelength X = 17.4 A. 

FIGURE 12.3 Parts (a) and (b) show sample-to-sample variability studies, the different symbols denoting patterns obtained from different pieces of gel under identical conditions, (a) Diffraction traces obtained from seven samples in the gel phase at T = 5°C. The PEO molecular weight was 2 million, and the concentration variables were fixed as r = 0.01, c = 0.01 M, v = 0.004. (b) Diffraction traces obtained at v = 0.008, with the other variables as defined in part (a), (c) Plot of the rf-values obtained as a function of v at M = 2 million, r - 0.01, c = 0.01 M, T = 5°C. 

The main aim was to determine the distribution of PEO molecules between the gel and the supernatant fluid at r = 0.1, c = 0.1 M, T = 5°C for M = 18,000 (bridging) and polymer volume fractions in the range between v = 0 and v = 0.12. The corresponding neutron diffraction traces are shown in Figure 12.6a. In comparing these structural analyses with an independent analysis of the concentration of the PEO in the supernatant fluid, we established the following protocol in preparing the samples. 

Additional data about the structure of black films are obtained by X-ray diffraction method. The first steps [336,338] have been performed with vertical foam films in a frame in a horizontal scanning diffractometer. Black films from decyltrimethyl ammonium decyl sulphate and NaBr solutions have been studied. The film thickness was calculated using a model of the mean electron density projection on the film normal. However, there was no indication whether the films were CBF or NBF. Platikanov et al. [339,340] used a new device for investigation of a horizontal black films from aqueous NaDoS solution (see Section 2.2.6). They found essentially different X-ray diffraction traces for the three types of black films CBF, NBF and stratified black films. This indicates their different structure. Precise X-ray reflectivity measurements with CBF and NBF films from NaDoS and NaCl aqueous solutions [341-343] provided more details about their structure. The data obtained for the thicknesses of the respective layers which detail the film structure are given below... 

Figure 7 shows schematic reproductions of the shapes of the X-ray diffractive traces of alpaca observed after treatments in water and tetrachloroethylene. The reflections observed at about 9.8° (20) may indicate that the fibers contain ordered components having a specific helical configuration of the polypeptide chains (31). Aqueous treatments caused some changes in the intensities of the traces. In comparison, the nonaqueous treatment in tetrachloroethylene yielded a trace not much different from the control trace. On the basis of these observations, it is postulated that nonaqueous treatments affect the fiber morphology of historic cotton and protein fibers to a lesser degree than aqueous cleaning treatments. 

Analysis of X-ray diffraction patterns of the precipitates resulting from the addition of salts of the four metals to GSL North Arm brine showed that both copper and lead precipitated in the basic carbonate form. Zinc and cadmium compounds were not found in these X-ray diffraction traces, which may be due to these compounds comprising less than five percent of the solid material analyzed. 

Diffraction tracings of the HOPG intercalation compounds used in the conductivity measurements were obtained on a Phillips-Norelco powder diffractometer equipped with a graphite monochromater. Because of moisture... 

Characterization of Catalysts. Comparative surface area measurements were made on a selection of the catalyst samples as described previously (9). X-ray diffraction traces were obtained for each zeolite both before and after use. 

Crystallinity Index. X-ray diffraction traces of the samples were measured -with Rigakudenki X-ray diffractometer type D-9c. Samples partially and completely charred were taken from TGA experiments. Crystallinity indices of the samples -were determined according to Segal s method (2). 

Phosphorus and Chlorine Contents. Phosphorus and chlorine contents of the samples in char residue at kOO C are shown in Table IV. Phosphorus content did not change by thermal decomposition in all samples. But chlorine content decreased by pyrolysis. Chlorine introduced by stannic chloride treatment hardly decreased, but that by grafting decreased easily by pyrolysis. Stannic chloride is not introduced in cotton in the form of stannic chloride, because the chlorine content of stannic chloride treated cellulose is very lower than that calculated from weight increase. X-ray diffraction trace of burned sample... 

Fig. 33.2. X-ray diffraction traces for textured P"-Al203 parallel and perpendicular to the pressing axis.

XRD analysis provides a means by which different crystalline phases are characterized and identified. Samples are normally prepared as finely ground material and then presented to the X-ray beam in such a way that individual crystallites are randomly orientated. Comparison of diffraction traces with standard reference profiles enables the identification of phases to be made. Reference patterns are published by the International Centre for Diffraction Data. In some cases with a careful use of reference materials, internal standards and mass absorption corrections, some quantitative results are obtainable using a variety of mathematical formulas on the peak heights or areas. 

To illustrate the type of data that is obtained. Fig. 5 shows the He diffraction traces from a Au(110)-(1 x 2) surface at two different wavelengths. 

Figure 12.5 Phase distribution versus depth in soi-gei derived PZT 53 47 thin fiims as determined by giancing angie X-ray diffraction, (a) Diffraction trace of the (111) perovskite peak from -350 A an obvious shouider due to a minor perovskite phase with siightiy different chemistry than the main phase is evident, (b) Diffraction trace of the (111) perovskite peak from -2320 A the minor phase peak is diminished compared to the main peak. A peak to due the underiying Pt eiectrode (-40.0°) is aiso evident. (After Reference 48.)...

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