Powder spectroscopy

The boron nitride obtained in this study was characterized by infrared spectroscopy, powder x-ray diffractometry and transmission electron microscopy. Trace elemental analyses were also performed by energy dispersive x-ray analysis and carbon arc emission spectroscopy. Representative spectra are displayed in Figures 2-4. 

O. Bemtsson, L.G. Danielsson, B. Lagerholm, S. Folestad, Quantitative in-line monitoring of powder blending by near infrared reflection spectroscopy, Powder Technol. 123 (2002) 185—193. 

As shown by differential scanning calorimetry, temperature-controlled FT-IR spectroscopy, UV-Vis spectroscopy, powder X-ray diffraction, and circular... 

In this perspective we have afforded the study, via computer simulation, of an oxidative reaction, NOj -H 5 O2 —> NO3, inside the sodalite cages. Such intracage reaction has been experimentally studied by IR and wti-visible spectroscopies, powder X-rays diffraction and thermogravimetry in the temperature range 900-1000 K [1, 2, 3]. It has been proved that (i) the reaction occurs in air, (ii) the oxidizing agent is molecular oxygen, (in) the reaction is first order with respect to NOj and is completed in 30 hours. However, the reported experiments do not allow a detailed microscopic analysis of the reaction mechanism. 

In the aluminate route to LDH, aluminum salt (113,114), aluminum hydroxide (115,116), or aluminate (117-119) is initially treated with the required amount of base (e.g., six hydroxides for each aluminum if the product is to be of type M(II)2A1(0H)6X), followed by addition of M(II), either in a salt or a carbonate form (113-115,117,119) or in the form of an oxide or hydroxide (116,118,120,121). The pH graph observed for this titration shows endpoints related to the formation of Al(OH)3, aluminate, and LDH. This method of formation yields LDH directly from solution, with no intervening solid phase. The product has an increased degree of order in the metal hydroxide layer and slightly smaller surface area when compared to LDH prepared by other methods, as shown by infrared spectroscopy, powder X-ray diffractometry, scanning electron microscopy, and MAS Al and MAS Cl NMR (113,114,122). 

The formation of LDH materials is monitored by several techniques, most of which will be discussed in further detail in Section III. One such technique is the monitoring of the pH. As previously discussed, study of the pH can assist in determination of LDH formation and the mechanism through which the LDH is formed. Use of analytical techniques such as infrared spectroscopy, powder x-ray diffraction, and nuclear magnetic resonance spectroscopy can give information about such matters as the quality of LDH formed, the identity and packing of the interlayer anion, and the internal order within the metal hydroxide layer. 

See also Inorganic Compounds and Minerals Studied Using X-Ray Diffraction Materials Science Applications of X-Ray Diffraction Nucleic Acids and Nucleotides Studied Using Mass Spectrometry Nucleic Acids Studied Using NMR Polymer Applications of IR and Raman Spectroscopy Powder X-Ray Diffraction, Applications Small Molecule Applications of X-Ray Diffraction. 

Physical background. MAS will narrow the inliomogeneously broadened satellite transitions to give a series of sharp sidebands whose intensity envelopes closely follow the static powder pattern so that the quadnipole interaction can be deduced. The work of Samoson [25] gave real impetus to satellite transition spectroscopy by showing that both the second-order quadnipolar linewidths and isotropic shifts are fiinctions of / and Some combinations of / and produce smaller second-order quadnipolar effects on the satellite lines than... 

Fig. 4. Scanning electron micrograph of 5-p.m diameter Zn powder. Neck formation from localized melting is caused by high-velocity interparticle coUisions. Similar micrographs and elemental composition maps (by Auger electron spectroscopy) of mixed metal coUisions have also been made.

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. 

The ease of sample handling makes Raman spectroscopy increasingly preferred. Like infrared spectroscopy, Raman scattering can be used to identify functional groups commonly found in polymers, including aromaticity, double bonds, and C bond H stretches. More commonly, the Raman spectmm is used to characterize the degree of crystallinity or the orientation of the polymer chains in such stmctures as tubes, fibers (qv), sheets, powders, and films... 

In this chapter shock modification of powders (their specific area, x-ray diffraction lines, and point defects) measurements via analytical electron microscopy, magnetization and Mossbauer spectroscopy shock activation of catalysis, solution, solid-state chemical reactions, sintering, and structural transformations enhanced solid-state reactivity. 

IF7 has been shown to act as a weak Lewis acid towards CsF and NOF, and the compounds CsIFg and NOIFg have been characterized by X-ray powder patterns and by Raman spectroscopy they are believed to contain the IFg anion. 

Chiral salen chromium and cobalt complexes have been shown by Jacobsen et al. to catalyze an enantioselective cycloaddition reaction of carbonyl compounds with dienes [22]. The cycloaddition reaction of different aldehydes 1 containing aromatic, aliphatic, and conjugated substituents with Danishefsky s diene 2a catalyzed by the chiral salen-chromium(III) complexes 14a,b proceeds in up to 98% yield and with moderate to high ee (Scheme 4.14). It was found that the presence of oven-dried powdered 4 A molecular sieves led to increased yield and enantioselectivity. The lowest ee (62% ee, catalyst 14b) was obtained for hexanal and the highest (93% ee, catalyst 14a) was obtained for cyclohexyl aldehyde. The mechanism of the cycloaddition reaction was investigated in terms of a traditional cycloaddition, or formation of the cycloaddition product via a Mukaiyama aldol-reaction path. In the presence of the chiral salen-chromium(III) catalyst system NMR spectroscopy of the crude reaction mixture of the reaction of benzaldehyde with Danishefsky s diene revealed the exclusive presence of the cycloaddition-pathway product. The Mukaiyama aldol condensation product was prepared independently and subjected to the conditions of the chiral salen-chromium(III)-catalyzed reactions. No detectable cycloaddition product could be observed. These results point towards a [2-i-4]-cydoaddition mechanism. 

An initial solution was prepared by dissolving metallic niobium powder in 40% hydrofluoric acid. The dissolution was performed at elevated temperature with the addition of a small amount of nitric acid, HN03, to accelerate the process. The completeness of niobium oxidation was verified by UV absorption spectroscopy [21]. The prepared solution was evaporated to obtain a small amount of precipitate, which was separated from the solution by filtration. A saturated solution, containing Nb - 7.01 mol/1, HF - 42.63 mol/1, and corresponding to a molar ratio F Nb = 6.08, was prepared by the above method. The density of the solution at ambient temperature was p = 2.0 g/cc. Concentrations needed for the measurements were obtained by diluting the saturated solution with water or hydrofluoric acid. 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

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