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Noncrystalline solids

The otiier type of noncrystalline solid was discovered in the 1980s in certain rapidly cooled alloy systems. D Shechtman and coworkers [15] observed electron diffraction patterns with sharp spots with fivefold rotational synnnetry, a syimnetry that had been, until that time, assumed to be impossible. It is easy to show that it is impossible to fill two- or tliree-dimensional space with identical objects that have rotational symmetries of orders other than two, tliree, four or six, and it had been assumed that the long-range periodicity necessary to produce a diffraction pattern with sharp spots could only exist in materials made by the stacking of identical unit cells. The materials that produced these diffraction patterns, but clearly could not be crystals, became known as quasicrystals. [Pg.1369]

Structure and Bonding in Noncrystalline Solids G. E. Walrafen, A. G. Revesz, Eds., Plenum, New York (1986). [Pg.320]

Raman spectroscopy is particularly useful for investigating the structure of noncrystalline solids. The vibrational spectra of noncrystalline solids exhibit broad bands centered at wavenumbers corresponding to the vibrational modes of the corresponding crystals (Figure 5). In silicate glasses shifts in the high-wavenumber bands... [Pg.437]

Raman spectroscopy is a very convenient technique for the identification of crystalline or molecular phases, for obtaining structural information on noncrystalline solids, for identifying molecular species in aqueous solutions, and for characterizing solid—liquid interfaces. Backscattering geometries, especially with microfocus instruments, allow films, coatings, and surfaces to be easily measured. Ambient atmospheres can be used and no special sample preparation is needed. [Pg.440]

Some organic contaminants are volatilized and escape from the soil surface and must be collected by a vacuum system. Inorganics and some organics are trapped in the melt, which, as it cools, becomes a form of obsidian or very strong glass. When the melt is cooled, it forms a stable noncrystalline solid. [Pg.166]

Rahman, M.M., Takafuji, M., Ansarian, H.R., and Ihara, H., Molecular shape selectivity through multiple carbonyl-pi interactions with noncrystalline solid phase for RP-HPLC, Anal. Chem., 11, 6671, 2005. [Pg.293]

M. Glora, M. Wiener, R. Petricevic, H. Probstle, and J. Fricke. Integration of carbon aerogels in PEM fuel cells. Journal of Noncrystalline Solids 285 (2001) 283-287. [Pg.289]

This information is reported as the percentage that each of the clay mineral type contributes to total identifiable clay mineral content of the noncarbonate clay-sized fraction of the surface sediments. These percentages were determined by x-ray diffraction, which is luiable to identify noncrystalline solids. Using this technique, clay minerals were found to comprise about 60% of the mass of carbonate-free fine-grained fraction. Most of the noncrystalline soUds are probably mixed-layer clay minerals. Carbonate was removed to facilitate the x-ray diffraction characterization of the clay minerals. In some cases, roimd off errors cause the sum of the percentages of kaolinite, illite, montmorillonite, and chlorite to deviate slightly from 100%. [Pg.371]

Figure 1.49 Comparison of preparation procedures of noncrystalline solids illustrating the difference between glassy and amorphous solids. Reprinted, by permission, from H. Scholze, Glass, p. 123. Copyright 1991 by Springer-Verlag. Figure 1.49 Comparison of preparation procedures of noncrystalline solids illustrating the difference between glassy and amorphous solids. Reprinted, by permission, from H. Scholze, Glass, p. 123. Copyright 1991 by Springer-Verlag.
Tauc, J., 1972. Optical properties of noncrystalline solids, in Optical Properties of Solids, F. Abeles (Ed.), Elsevier, New York, pp. 277-313. [Pg.517]

It was mentioned earlier (Section 3.4) that all materials can be rendered amorphous. What is often not recognized by chemists is that a large variety of materials - catalysts, catalyst supports, xerographic photoreceptors, optical fibres, large-area solar cells and many biominerals - are noncrystalline (Elliott et al, 1986). Noncrystalline solids possess no long-range order and their structure is akin to that of a frozen liquid. Most... [Pg.214]

In the case of those noncrystalline solids that are of sufficiently high electrical condnctivity that dielectric relaxation proscribes the application of the transit time ontlined earlier, the experimental configuration displayed in Fig. 3.1(c) may be of the valne. Here, carriers of both species are excited in equal and uniform concentration across the active area of a specimen film fitted with coplanar electrodes. For step-function illumination, the rate of increase of photocurrent with time is linearly proportional to the carrier generation rate and the carrier drift velocity (and at times sufficiently short that recombination may be neglected). Thus, under the assumption that one species of carrier dominates the behavior, its mobility may be determined. [Pg.41]

Polysaccharides (non-sugars), (C6Hio05) noncrystalline solids, insoluble in water, tasteless,... [Pg.279]

Sodium 9-cyano-9-hydrido-9-borabicydo 3.3.1 nonane (9BBN-NaCN) (1). Mol. wt. 171.03, tacky noncrystalline solid. The reagent is prepared by reaction of NaCN with 9-BBN in THF. [Pg.584]

Amorphous A noncrystalline solid substance. Unlike crystalline materials, the atoms of amorphous substances do not have regular (ordered) arrangements. Glass is an amorphous substance. [Pg.439]

Demethoxyabresoline (67) was obtained as a noncrystalline solid. Spectroscopic investigation revealed the presence of a phenolic OH, a 1-phenyl-quinolizidine system, and a trans-cinnamyl group. The stereochemistry at C-l, C-3, and C-5 was the same as in abresoline. The molecular formula C25H29N05 was established by mass spectrometry. The presence of fragment ions at m/e 259 (M —164) and 258 was characteristic of p-hydroxy-cinnamyl esters of the phenylquinolizidol (63a). The assigned structure 68 was confirmed by basic hydrolysis to 63a and p-hydroxycinnamic acid as well as by catalytic hydrogenation to a known dihydro derivative (52). [Pg.287]

Glass is a noncrystalline solid substance with similarities to a liquid. To put it simply, glass is made up of an irregular network of particles (usually Si02) into the gaps between which the other components (the network converters such as Na20, K20) are woven, Figure 2.2. [Pg.20]

A noncrystalline solid with no well-defined ordered structure. [Pg.6]


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See also in sourсe #XX -- [ Pg.66 ]




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Noncrystallinity

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