Phase composition spectroscopy

The phase composition of products obtained from the thermal treatment of LiNbOF4 and NaNbOF4 was investigated using X-ray diffraction and vibration spectroscopy, as reported in [379]. Compounds with the following structures were found M2NbOF5, MNb02F2 and MNbC>3, where M = Li or Na. 

The phase composition of glycine crystal forms during the drying step of a wet granulation process has been studied, and a model developed for the phase conversion reactions [88], X-ray powder diffraction was used for qualitative analysis, and near-infrared spectroscopy for quantitative analysis. It was shown that when glycine was wet granulated with microcrystalline cellulose, the more rapidly the granulation... 

This process has been studied by infrared spectroscopy by Dwyer (22), using 9% Pt/Si02 and the cell used by Ueno et al. (19). The bands arising from gaseous CO2 and surface CO were followed after a switch in the gas phase composition from 3kPa O2 in helium, to pure helium for a few seconds and then to 2kPa CO in helium. 

The gas-phase composition before or after the reactor was monitored by mass spectroscopy although no such data are shown here, experience indicated the necessity of a fast-response inlet system. 

Doyle, C.A., Vickers, T.J., Mann, C.K., and Dorsey, J.G, Characterization of CIS bonded hqnid chromatographic stationary phases by Raman spectroscopy the effect of mobile phase composition, J. Chromatogr. A, 877, 25, 2000. 

Fe(OH), using Mdssbauer spectroscopy, optical spectroscopy and transmission electron microscopy. Phy. Chem. Min. 22 11-20 McCreadie, H. Blowes, D.W. (2000) Influence of reduction reactions and solid-phase composition on porewater concentrations of arsenic. Environ. Sd. Tedm. 34 3159-3166 McFadden, L.D. Hendricks, D.M. (1985) Changes in the content and composition of pedogenic iron oxyhydroxides in a chronose-quence of soils in Southern Cahfomia. Quart. Res. 23 189-204... 

The phase composition changes for the ultrafine catalyst were also very similar to those seen for the precipitated catalyst. Mossbauer spectroscopy... 

There are comparatively few measurements of the hydrate phase composition, due to experimental difficulty. Hydrate phase difficulties arise because water is often occluded in the hydrate mass, separation of hydrate and water is difficult, and the hydrate phase of mixtures is often inhomogeneous in experiments. Consequently, the ratio of water to hydrocarbon is often inaccurate. As discussed in Chapter 6, only over the last two decades have experimental techniques (e.g., diffraction and NMR and Raman spectroscopy) become accurate enough to determine the degree of filling of hydrate cavities with different types of molecules. 

Zhang, X., Do, M.D., Hoobin, P. and Burgar, I. 2006. The Phase Composition and Molecular Motions of Plasticized Wheat Gluten-Based Biodegradable Polymer Materials Studied by Solid-State NMR Spectroscopy. Polymer, 47, 5888-5896. 

Phase composition, distribution character of the modifier particles on the surface of graphite particles has been analyzed using the X-ray studies, the Auger spectroscopy, electron microscopy and secondary ion mass spectrometry. The investigations have been performed using the following equipment DRON-4-07 X-ray diffractometer (filtered CoKa radiation), LAS-2000 Auger spectrometer (Riber, France), JSM-840 electron microscope (Japan). 

TG/DTA, TPR, and complementary techniques for characterizing catalysts in the working state (e.g., XRD Raman, IR, and UV-vis spectroscopies) can provide structural and metal valence information under reaction conditions. However, the capability of TR-XAFS spectroscopy to reveal quantitative phase composition and average metal valence together with the evolution of the local structure of a catalyst under varying (reaction) conditions, combined with a time resolution of 100 ms will continue to be a very powerful tool for kinetics investigations in solid-state chemistry and heterogeneous catalysis. 

Mossbauer spectroscopy has been quite successful in identifying catalyst components. Mossbauer spectroscopy provides quantitative site populations, easily discriminating between various metal oxidation states and anion coordinations, and it can lead to phase compositions or distributions between phases of the isotope under investigation. It also gives quantitative population distributions of local distortion environments and local chemical environments, via extracted quadrupolar splitting distributions. 

Diffraction Calorimetry Spectroscopy Monitor solid phase composition... 

Near-infrared spectroscopy was used to quantitatively determine the phase composition of a compound capable of existing in two polymorphic forms even though the NIR spectra were fairly similar.79 Using a five-wavelength calibration model, nearly 100% recovery was obtained in a series of spiked calibration samples, with relative standard deviation values ranging from 0.1% to 0.9%. The authors concluded that the use of NIR spectroscopy... 

In a wide-ranging study, NIR spectroscopy was used to quantitate the phase composition in various forms of sulfamethoxazole, sulfathiazole, lactose, and ampicillin.80 For instance, as shown in Figure 4, the o -mono-hydrate phase of lactose is easily distinguished from /Mactose anhydrate on the basis of the characteristic band at 1940 nm associated with the water combination mode. In all cases, however, properly calibrated NIR methods were able to yield good predictions of phase composition relative to the actual composition of the standards used, and it was concluded that the quantitative NIR was equally effective for such work as other commonly used quantitative methods. 

A convenient starting point for such an assessment involves two independent investigations of the surface composition of tin-antimony oxides by X-ray photoelectron spectroscopy (XPS) in 1979 (/J, 27). The study by Pyke and Cross (13) followed their earlier work on the phase composition (72) and showed the extent of surface enrichment in antimony to depend on bulk composition and calcination conditions. For example, the surface of a material with a bulk antimony content of 20% and calcined at 600 C for 16 hr was found to be enriched by a factor of about 2.7, with the degree of enrichment decreasing rapidly with depth from surface until the bulk composition was attained at 50A. Although the surface enrichment factor was found to vary with bulk composition at constant temperature, the dependence of the surface composition on calcination temperature represented an even more interesting feature of the study and is depicted in Fig. 2. 

For instance, Raman spectroscopy was used to study the effect of pressure and temperature on the phase composition of fluoranil crystals. Figure 2 shows the Raman spectra obtained at a series of increasing pressures, where the changes in band frequency indicate the existence of pressure-induced phase transitions. It was deduced from sharp discontinuities in the Raman spectra that a phase transition took place at a temperature of around 180 K if the pressure was 1 atm, but that this transition shifted to 300 K if the pressure was increased to 0.8 GPa. Other work indicates that this particular phase transition does not entail a change in the crystal space group, but involves displacement within the unit cell. 

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