X-ray diffraction diagrams

The fact that the structure that I formulated for this alloy from chemical arguments with no knowledge about the X-ray diffraction diagram was found later to agree quantitatively with that diagram has convinced me that the structure is correct. I emphasize that I formulated only one structure, and that the X-ray diagram was not involved in any way in its formulation. The probability of chance agreement of the lattice constant to 0,1 A and of adherence to the selection rules for intensities is surely less than 1 in 1,000. 

Unsubstituted Copper Phthalocyanine Blue is polymorphous. X-ray diffraction diagrams point to five different crystal modifications (a, (3, y, 8, e) (Fig. 91). The relative thermodynamic stability of the individual cystal phases decreases in the following order (3>e>8>a = y [13-16],... 

It is worth noticing that for pH > 2, reaction (2) is complete as shown by the absence of the molecular complex Pd(H20)4 + in the solution analyzed by UV-visible spectroscopy. X-ray diffraction diagrams of dried suspensions after neutralization confirm... 

The X-ray diffraction diagrams of pyrite before and after treatment with sodium sulphide are shown in Fig. 3.10, which appears to confirm the presence of sulphur because the diffraction band of elemental sulphur occurs after pyrite treated with Na2S. 

Figure 3.10 X-ray diffraction diagrams of pyrite (a) untreated (b) treated by 8.56 x 10 mol/L Na2S (Wang et al., 1991a,b,c,d)...

Figure 3. X-ray diffraction diagram of an oriented bundle of complex crystals in a fine glass capillary. Needle axis is vertical, and pattern was recorded with flat plate camera...

After the required reaction time, the gel mixtures were cooled, centrifuged, and washed three times with more than a tenfold quantity of distilled water. After drying at 105°C, the products were powdered if necessary. X-ray diffraction diagrams were recorded (Cu Ka radiation), and the phases present were identified by comparing their diffraction peaks with published d values or with those of standard zeolite diffraction diagrams. The quantity of each species was estimated within 5% from relative peak heights compared with the best of their kind, which were also selected for a more detailed crystallographic examination. 

Fig. 2. Diagrammatic representation of the unit cell of cellulose, The monoclinic cell, dimensions 10.3 A x 8.35 A = S4. is delineated hy solid lines with one cellulose chain at each vertical edge and one lamiparallell in the center. Open circles = carbon atoms, solid circles - oxygen atoms. For clearness of the diagram, the hydroxyl groups on carbons 2, 3, and 6 are omitted and hydrogen atoms are omitted. TWo spacing at 6.1 A and 5.4 A are included, inasmuch as these are strongly represented in the x-ray diffraction diagram...

Evidence for the presence of hydrosilicates in the preparations could also be obtained from differential thermal analysis (2). An examination of the curves given in Fig. 2 showed an endothermal deflection at 125-175° C., which must be caused by the expulsion of adsorbed water, since the X-ray diffraction diagram revealed no change. Upon further heating, the preparations display an endothermal deflection characteristic for the compounds present, viz. ... 

As the X-ray diffraction diagrams of an oriented gel (Fig. 6) are poorly crystalline, it has been useful to conduct X-ray crystal structure analyses of oligomer of 3-(l->-3)-D-glucan. The molecular structures of laminarabiose and its acetyl derivative have been determined. 

Figure 8.18 DSC (at 30% solids) and x-ray diffraction diagrams of three amylose-glycerol monostearate complexes differing in the degree of packing oftheir helices in the solid-state. The inset depicts the relationships between Gibbs free energy and temperature for the three structural forms, /, lla and lib the arrow indicates the melt-mediated transformation of metastable form / to lla.20...

Ternary complexes called soda celluloses can form between cellulose, sodium hydroxide, and water [310]. In these complexes, some of the water molecules of the sodium hydroxide hydrates are replaced by the hydroxyl groups of the cellulose [310]. The x-ray diffraction diagrams have been obtained for five soda celluloses as intermediates in the formation of cellulose II from cellulose I [310,316]. 

Fig. 9. X-ray diffraction diagrams of DSP (y-form, needles), DSP (a-form, plates), P2VB, poly-DSP, and poly-P2VB (source Ref.8)...

In the case of p-PDA Me, the directions of all axes of the polymer do not coincide with those erf the monomer. However, the temperature effect on the reaction behavior and the continuous changes of the X-ray diffraction diagrams of all monomers except m-... 

Great advances have been made in protein chemistry since the time of Astbury s pioneering work. Polyalanine, like keratin, exists in an alpha form which may be transformed into the beta conhguration by stretching. It is much easier to interpret X-ray diffraction diagrams of substances of known constitution, such as polyalanine, than those obtained from the infinitely more complex keratin molecule. 

The X-ray diffraction diagram gives a repeat period of 6-95 A (0-695 ftm), which is extremely close to two amino-acid residues fully extended which would be 3-5 A (0-35 nm) each. The structural unit which gives the pattern is probably the glycine alanine residue. 

Unfortunately sericin contains no crystalline regions so no useful information can be gained from X-ray diffraction diagrams. 

Terylene, like nylon, is thermoplastic and can have permanent pleats or shapes imposed by the action of heat with or without steam. It breaks under loads of 4-2 to 4-8 g per denier and the continuous filament has an extension of 22 to 30 per cent at the breaking point. The fibre has marked crystallinity as shown by the X-ray diffraction diagram illustrated in Fig. 2.7, and by the low moisture regain of 0-4 per cent. The closely packed and highly-orientated molecules make Terylene markedly hydrophobic and difficult to dye. Modified polyester fibres are produced with an affinity for both disperse and cationic dyes. 

This may either be done in a stenter, or a Bates Type K machine (Fig. 21.2), in which the fabric is held against electrically heated rollers by means of endless blankets. The temperature which is required for a satisfactory set is between 190° and 250°C (374° to 482°F). Heat setting is preferably carried out before dyeing. X-ray diffraction diagrams show that setting increases the crystallinity of the fibre and therefore reduces accessibility. 

Fig. 3.36. X-ray diffraction diagrams of Sm125Fe875 after mechanical alloying (top), after the formation of Sm2Fe17 by annealing in vacuum (middle), after the nitriding reaction (bottom)...

We have recently obtained x-ray diffraction diagrams of equivalent preparations using pentandiol and hexandiol and are extending the above considerations to these and systems prepared with other chain extenders. Our research is supported by A.R.O. grant number DAAG29-79G-0070. 

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