Crystallinity assessment

X-ray scattering measures the crystallinity considering only crystals thicker than 2-3 nm. IR measures the total content of helix structures. The very thin crystals (< 2-3 nm) are included in the IR crystallinity assessment. It is also possible that the helices are present in the amorphous phase. 

The first analytical tool to assess tire quality of a zeolite is powder x-ray diffraction. A collection of simulated powder XRD patterns of zeolites and some disordered intergrowths togetlier witli crystallographic data is available from tlie IZA [4o]. Phase purity and x-ray crystallinity, which is arbitrarily defined as tlie ratio of tlie intensity of... 

In colorfastness to acid spotting, ISO 10S-E0S, drops of a solution of either acetic acid (300 g of glacial acetic acid per Hter of water), sulfuric acid (50 g of concentrated acid per Hter), or tartaric acid (100 g of crystalline acid per Hter) are spotted onto the test material, which is then dried and assessed. Colorfastness to alkaH spotting, ISO 10S-E06, is like E05 except that a solution of 100 g of anhydrous sodium carbonate per Hter of water is used. Colorfastness to water spotting, ISO 10S-E07, is like E05 but uses drops of water and assessment is made after 2 min wet and after drying. In colorfastness to hot water, ISO 10S-E08, the textile specimen and adjacents are wound around a glass rod and placed in water adjusted to pH 6 with acetic acid at 70°C... 

In the case of an amorphous polymer the glass transition temperature will define whether or not a material is glass-like or rubbery at a given temperature. If, however, the polymer will crystallise, rubbery behaviour may be limited since the orderly arrangement of molecules in the crystalline structure by necessity limits the chain mobility. In these circumstances the transition temperature is of less consequence in assessing the physical properties of the polymer. 

Whilst completely atactic material would be amorphous, commercial materials have a small measure of crystallinity. This is often assessed in terms of insolubility in n-heptane which is usually of the order of 5-10%. Viseosity average moleeular weights are in the range 20 000-80 000 and specific gravities are about 0.86 g/cm. ... 

EH 74/2 Respirable crystalline silica exposure assessment document... 

Reliability of airflow measurements m assessing ventilation systems performance Cobalt - a review of properties, use and levels of exposure A review of respirable crystalline silica - Exposure and control... 

The orientation of crystallites in PET fibers can also be assessed quantitatively by means of IR spectro-graphic examination. In this case, the basis for the assessment are the values of dichroic ratio (R) of the crystalline absorption bands in the fiber spectrogram. The determination of the values of fc is made using Fraser s dependence [24,25] modified by Chranowski [26] ... 

Reports of kinetic studies do not always include an explicit statement as to whether or not the reactant melted during reaction or, indeed, if this possibility was investigated or even considered (cf. p. 1). This aspect of behaviour is important in assessing the mechanistic implications of any data since reactions in a homogeneous melt, perhaps a eutectic, usually proceed more rapidly than in a crystalline solid. It is accepted that the detection of partial or localized melting can be experimentally difficult, but, in the absence of relevant information, it is frequently impossible to decide whether a reported reaction proceeds in the solid phase. 

Color is the result of an absorption measurement, commonly carried out at X 410 nm, to assess the tinge that is often found in crystallization liquors that impact an off-white to yellowish aspect to the crystalline product. 

We thus see that the RFOT theory provides a rather complete picture of vitrification and the microscopies of the molecular motions in glasses. The possibility of having a complete chart of allowed degrees of freedom is veiy important, because it puts strict limitations on the range of a priori scenarios of structural excitations that can take place in amorphous lattices. This will be of great help in the assessment of the family of strong interaction hypotheses mentioned in the introduction. To summarize, the present theory should apply to all amorphous materials produced by routine quenching, with quantitative deviations expected when the sample is partially crystalline. The presence and amount of crystallinity can be checked independently by X-ray. It is also likely that other classes of disordered materials, such as disordered crystals, will exhibit many similar traits, but of less universal character. 

There are no known examples of supported clusters dispersed in crystallo-graphically equivalent positions on a crystalline support. Thus, no structures have been determined by X-ray diffraction crystallography, and the best available methods for structure determination are various spectroscopies (with interpretations based on comparisons with spectra of known compoimds) and microscopy. The more nearly uniform the clusters and their bonding to a support, the more nearly definitive are the spectroscopic methods however, the uniformities of these samples are not easy to assess, and the best microscopic methods are limited by the smallness of the clusters and their tendency to be affected by the electron beam in a transmission electron microscope furthermore, most supported metal clusters are highly reactive and... 

To assess homogeneity, the distribution of chemical constituents in a matrix is at the core of the investigation. This distribution can range from a random temporal and spatial occurrence at atomic or molecular levels over well defined patterns in crystalline structures to clusters of a chemical of microscopic to macroscopic scale. Although many physical and optical methods as well as analytical chemistry methods are used to visualize and quantify such spatial distributions, the determination of chemical homogeneity in a CRM must be treated as part of the uncertainty budget affecting analytical chemistry measurements. 

One problem with methods that produce polycrystalline or nanocrystalline material is that it is not feasible to characterize electrically dopants in such materials by the traditional four-point-probe contacts needed for Hall measurements. Other characterization methods such as optical absorption, photoluminescence (PL), Raman, X-ray and electron diffraction, X-ray rocking-curve widths to assess crystalline quality, secondary ion mass spectrometry (SIMS), scanning or transmission electron microscopy (SEM and TEM), cathodolumi-nescence (CL), and wet-chemical etching provide valuable information, but do not directly yield carrier concentrations. 

Hameed, P.S. and A.I.M. Raj. 1989. Effect of copper cadmium and mercury on crystalline style of the freshwater mussel Lamellidens marginalis (Lamarck). Indian Jour. Environ. Health 31 131-136. Hamilton, S J. and KJ. Buhl. 1990. Safety assessment of selected inorganic elements to fry of chinook salmon (Oncorhynchus tshawytscha). Ecotoxicol. Environ. Safety 20 307-324. 

Delhi soils by studying its speciation in the soil profile and to assess if there was any spatial variability. Soils representing the Aravali Ridge and the alluvial floodplains of river Yamuna were collected as a single, undisturbed core up to a depth of lm and the profile differentiated into four layers- 0-17 cm, 17-37 cm, 37-57 cm, and 57-86 cm. Pseudo total Aluminum and Iron in the soils were speciated into the operationally defined species (weakly exchangeable, organic matter complexes, amorphous oxides and hydroxides, and crystalline or free oxides) by widely recommended selective extraction procedures. Both A1 and Fe in these soils are bound predominantly as Fe oxides and silicates and have only very low percentages in the easily mobilizable pools. 

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