Chemical analyses, characterization

A fundamental requirement in powder processing is characterization of the as-received powders (10—12). Many powder suppHers provide information on tap and pour densities, particle size distributions, specific surface areas, and chemical analyses. Characterization data provided by suppHers should be checked and further augmented where possible with in-house characterization. Uniaxial characterization compaction behavior, in particular, is easily measured and provides data on the nature of the agglomerates in a powder (13,14). 

Whatever the development of knowledge in the fields of chemical analysis and structure-property relationships, the characterization by determination of conventional properties of usage and other values related empirically to properties of usage will remain mandatory and unavoidable, as a minimum because it is required with regard to specifications. 

Faulkner, L. R. Electrochemical Characterization of Chemical Systems. In Kuwana, T. E., ed.. Physical Methods in Modern Chemical Analysis, Vol. 3. Academic Press New York, 1983, pp.137-248. 

The proportionality between the concentration of chromophores and the measured absorbance [Eqs. (6.8) and (6.9)] requires calibration. With copolymers this is accomplished by chemical analysis for an element or functional group that characterizes the chromophore, or, better yet, by the use of isotopically labeled monomers. 

Many attempts have been made to characterize the stabiUty of the colloidal state of asphalt at ordinary temperature on the basis of chemical analysis in generic groups. For example, a colloidal instabiUty index has been defined as the ratio of the sum of the amounts in asphaltenes and flocculants (saturated oils) to the sum of the amounts in peptizers (resins) and solvents (aromatic oils) (66) ... 

In electron-optical instruments, e.g. the scanning electron microscope (SEM), the electron-probe microanalyzer (EPMA), and the transmission electron microscope there is always a wealth of signals, caused by the interaction between the primary electrons and the target, which can be used for materials characterization via imaging, diffraction, and chemical analysis. The different interaction processes for an electron-transparent crystalline specimen inside a TEM are sketched in Eig. 2.31. 

Section 2 of this chapter describes the characterization of carbonaceous materials by powder X-ray diffraction, small-angle-X-ray scattering (SAXS), measurements of surface area, and by the carbon-hydrogen-nitrogen (CHN) test, a chemical analysis of composition. In this section, we also describe the electrochemical methods used to study carbonaceous materials. 

Surface and bulk characterization were carried out using electron spectroscopy for chemical analysis (ESCA or XPS) and x-ray diffraction (XRB). The results will be discussed In relation to methanatlon activity. 

The samples were characterized by chemical analysis induced coupled plasma and atomic absorption techniques apparatus), nitrogen adsorption isotherms (at 77 K), XRD patterns ( Siemens diffractometer and (3uKa radiation), SEM observations (Hitachi S800 apparatus of the University C. Bernard, Lyon I) and TGA-DTA (Setaram 92-12 apparatus). The IR spectra were recorded with a Bruker IPS 48 FTIR spectrometer. 

During production and characterization of various internal animal tissue reference materials for a number of metals, a comparative study was performed for Pb in six bovine teeth and two bovine bone materials using calibration with a solid RM and two versions of wet chemical analysis with GF-AAS and electrochemical (DPASV) detection. There was good agreement in the range of approx. 1.3-3 tng/kg dry weight for all techniques used (Liicker et al. 1992). 

The effects of tin/palladium ratio, temperatnre, pressnre, and recycling were studied and correlated with catalyst characterization. The catalysts were characterized by chemisorption titrations, in situ X-Ray Diffraction (XRD), and Electron Spectroscopy for Chemical Analysis (ESCA). Chemisorption studies with hydrogen sulfide show lack of adsorption at higher Sn/Pd ratios. Carbon monoxide chemisorption indicates an increase in adsorption with increasing palladium concentration. One form of palladium is transformed to a new phase at 140°C by measurement of in situ variable temperature XRD. ESCA studies of the catalysts show that the presence of tin concentration increases the surface palladium concentration. ESCA data also indicates that recycled catalysts show no palladium sulfide formation at the surface but palladium cyanide is present. 

Sedgwick, R. D. and D. M. Hindenlang (1988), Mass-spectrometry and chromatog-raphy-mass-spectrometry, in Sibila, J. (ed.), A Guide to Materials Characterization and Chemical Analysis, VCH Verlag GmbH, Weinheim, pp. 45-53. 

In one of the earliest reports of the use of clean evaporated alloy films in surface studies, Stephens described the preparation and characterization of Pd-Au films and presented some results for the adsorption of oxygen on them 46). Films of pure Pd and 60% Au were evaporated directly from wires, while films of 80% Au and pure Au were evaporated from a pre-outgassed tungsten support wire. The films were evaporated in a UHV system and the pressure was kept below PC8 Torr during evaporation. After evaporation, the films were stabilized by cycling between —195° and 30°C four times. They w ere characterized by X-ray diffraction and chemical analysis surface areas were measured by the BET method using krypton adsorption. 

The film electrodeposition process was studied by means of linear sweep voltammetry. The rate of electrochemical reaction was determined from current density (current-potential curves). The film deposits were characterized by chemical analysis, IR - spectroscopy, XRD, TG, TGA and SEM methods. 

V-Mo-Zeolite catalysts prepared by solid-state ion exchange were studied in the selective catalytic reduction of NOx by ammonia. The catalysts were characterized by chemical analysis, X-ray powder diffraction, N2 adsorption (BET), DRIFT, UV-Vis and Raman, spectroscopy and H2 TPR. Catalytic results show that upon addition of Mo to V-ZSM-5, catalytic performance was enhanced compared to V-ZSM-5. 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

Clark H.A., Kopelman R., Tjalkens R., Philbert M.A., Optical Nanosensors for Chemical Analysis inside Single Living Cells. 1. Fabrication, Characterization, and Methods for Intracellular Delivery of PEBBLE Sensors, Anal. Chem. 1999 71 4831— 4836. 

The NBO analysis characterizes the 7tcc— nnf interaction as relatively modest (25.0kcal mol-1), with 0.09e charge transfer from ethylene to HfH4. Accordingly, the coordinated alkene is somewhat activated toward nucleophilic attack, but the chemical effects are minor compared with those for other donor-acceptor motifs to be discussed below. 

Olfactorily active compounds carried in human milk have rarely been subjected to chemical analysis (Stafford, Horning and Zlatkis 1976 Pellizari, Hartwell, Harris III, Waddell, Whitaker and Erickson 1982 Shimoda, Ishikawa, Hayakawa and Osajima 2000 Bingham, Sreven-Tuttle, Lavin and Acree 2003), and so far no attempt was undertaken to characterize the volatile composition of human AG secretions. Thus, the degree of their chemical overlap or specificity cannot be evaluated. Here we present preliminary data from such comparative analyses of colostrum and AG secretions from the same women. 

Sibilia, J.P. (1988). A Guide to Materials Characterization and Chemical Analysis. VCH, New York. 

Ambrose, S.H. (1990). Preparation and characterization of bone and tooth collagen for isotopic analysis. Journal of Archaeological Science 17 431 451. Ambrose, S.H. (1993). Isotopic analysis of paleodiets methodological and interpretative considerations. In Investigations of Ancient Human Tissue Chemical Analysis in Anthropology, ed. Sandford, M.K., Gordon and Breach, Langhorne, pp. 59-130. 

Four samples of faujasite were synthesized at Si/Al ratios of 2.61, 2.80, 2.97 and 3.03 using published methods from seeded slurries (8-9) and using proprietary methods. One additional sample of Si/Al ratio 2.58 was purchased from Union Carbide. The samples were characterized by X-ray powder diffraction, by surface area measurements, and by wet chemical analysis. The results of these measurements are contained in Table I. 

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