Identification of phases

Despic, A. R., Identification of Phase Structure of Alloys by Anodic Linear Sweep Voltammetry, in Electrochemistry in Transition, O. J. Murphy, S. Srinivasan, and B. E. Conway, Eds., 1992, New York Plenum Press. 453. 

Electron diffraction performed with a parallel incident beam, i.e. Selected-Area Electron Diffraction is used to obtain good electron micrographs. The two-beam condition allows the observation of defects. SAED is also used in High-Resolution Electron Microscopy (HREM) to set a crystal to a zone axis so that the atomic columns are vertical in the microscope. SAED is very useful for the identification of phases and the... 

Kassahun K, Davis M, Hu P, Martin B, Baillie T. (1997) Biotransformation of the naturally occurring isothiocyante sulforaphane in the rat Identification of phase I metabolities and glutathione conjugates. Chem Res Toxicol 10 1228-1233. 

X-n s. In some ways this is an even simpler method of determining a phase diagram as sample preparation can be easy. The sample is placed in some form of X-ray diffractometer and its characteristic X-ray pattern obtained. If the crystal structure of the phases is known, the identification of phase fields can be rapid and reliable. X-ray methods do not tend to be a primary method for determination of... 

Phase Diagrams Construct phase diagram from Tfu, and Tvap measurements Phase transitions Identification of phase boundaries Comparison with Clausius-Clapeyron equation... 

The most obvious choice to determine phases that may be present in the molybdena catalyst is XRD. Matching of diffraction lines obtained for the catalyst with those of pure bulk compounds gives unequivocal identification of phases present. This is one of the few techniques that yields positive results. The absence of matching diffraction lines, however, is not proof that the phase in question is not present in the catalyst. The XRD technique is limited to particle sizes of above approximately 40 A for oxides or sulfides, lower sized particles giving no discernible pattern over that of the broad alumina pattern. Thus, the presence of a highly dispersed phase, either as small crystallites or as a surface compound of several layers thickness will not be detected. Also, if the phase is highly disordered (amorphous), a sharp pattern will not be obtained, although some broad structure above that of the alumina may be detected. It is a moot point as to whether such a case is considered as a separate phase or a perturbation of the alumina structure. Ratnasamy et al. (11) have examined their CoMo/Al catalyst from the latter point of view, with particular emphasis on the effect of calcination temperature. 

In electron microscopy as in any field of optics the overall contrast is due to differential absorption of photons or particles (amplitude contrast) or diffraction phenomena (phase contrast). The method provides identification of phases and structural information on crystals, direct images of surfaces and elemental composition and distribution (see Section H below). Routine applications, however, may be hampered by complexities of image interpretation and by constraints on the type and preparation of specimens and on the environment within the microscope. 

The identification of phase grading from XRD alone is not possible microscopic methods (Chui and Chan, 2005 Dutoit et al., 1995 Hills et al., 1999 Prakash et al., 2005) are needed to determine the locations of the phases that are identified. It is critical to compare the same active state of the catalyst in XRD and in microscopic investigations, as core-shell structures may be the result of phase segregation during sample preparation and transfer from a metastable statistical mix (Conte et al., 2006 Havecker et al., 2003 Hutchings, 2004 Kiely et al., 1996) into the more stable graded phase mixture (Frenkel et al., 2001 Fu et al., 2005 Hills et al., 1999). 

Figure 10.12 Identification of phases in a reactor deposit. The existence of anglesite shows the poisoning of the catalyst by lead.

In the pharmaceutical field, TSP LC-MS mainly found application in the identification of (Phase-I) metabolites and in quantitative bioanalysis. Two examples... 

The generation of Phase-I metabolites can be considered as a preparation for the Phase-II metabolism. The detection and identification of Phase-I metabolites is important, because possibly toxic metabolites are formed. Some metabolites are even more active than the dmg itself, either in the action the dmg was administered for or in toxic side effects. Administration of a prodrag with more favourable properties is sometimes performed. The prodrag is rapidly transformed in the actual active substance. Moreover, in quite a number of cases the analytical strategy is directed at identification of the Phase-I metabohtes, even after chemical or enzymatic deconjugation of the Phase-II metabolites. 

The Debye-Scherrer and other variations of the powder method are very widely used, especially in metallurgy. The powder method is, of course, the only method that can be employed when a single-crystal specimen is not available, and this is the case more often than not in metallurgical work. The method is especially suited for determining lattice parameters with high precision and for the identification of phases, whether they occur alone or in mixtures such as polyphase alloys, corrosion products, refractories, and rocks. These and other uses of the powder method will be fully described in later chapters. 

Identification of Phases in Blends of PMMA and PB Sample Preparation Spincoating of Blends... 

The identification of phases in polymer blends can be accomplished in force modulation mode (FMM) AFM. Using FMM AFM the relative moduli (a convolution of storage and loss moduli) are mapped on the specimen surface. The rms amplitude of the FMM cantilever, driven in an oscillatory fashion, reflects directly the modulus of underlying polymer specimen. In the blend discussed below three phases can be differentiated. 

Few detailed studies of xenobiotic metabolism vivo have been carried out In Invertebrates, and these few have concentrated on Identification of phase 1 metabolites. It Is presumed that invertebrates, like Insects, use glucose rather than glucuronic acid (36). 

C-JC Jackson, JW Hubbard, G McKay, JK Cooper, EM Hawes, KK Midha. Identification of phase-I and phase-II metabolites of fluphenazine in rat bile. Drug Metab Dispos 19 188, 1991. 

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