Powder characterization atomic absorption spectroscopy

The solid fraction has been recovered by filtration, washed with deionized water up to pH 9 and dried at 70 C in air. The products have been characterized by powder X-ray diffraction, scanning electron microscopy (Cambridge SiOO instrument), atomic absorption spectroscopy and nitrogen adsorption. Characterization by and ai MAS-NMR spectroscopy and thermal gravimetry have been already reported (7). 

In the preceding chapter it had already been discussed that it is less the synthesis itself which may be the bottleneck in high-throughput zeolite science but rather the analysis of the solids formed in a high-throughput program. There are several standard characterization techniques which are typically employed to characterize zeolitic materials. These include powder XRD for phase identification, X-ray fluorescence analysis (XRF) or atomic absorption spectrometry to analyze elemental composition, sorption analysis to study the pore system, IR-speclroscopy, typically using adsorbed probe molecules to characterize the acid sites, NMR spectroscopy and many others. For some of these techniques parallelized solutions have been developed and described in the literature, other properties are more difficult to assess in a parallelized or even a fast sequential fashion. 

Common techniques for the characterization of the electrocatalysts include High Resolution Electron Microscopy (HRTEM), Extended X-ray Absorption Fine Stracture Spectroscopy (EXAFS), Energy Dispersive Spectroscopy (EDS), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Near Edge X-ray Absorption Spectroscopy (XANES), X-Ray Powder Diffraction (XRPD), Infrared and Raman Spectroscopy (IR, RS). 

When a primary beam of monochromatic x-rays falls on a specimen, the x-rays may be absorbed or scattered. Coherent scattering of x-rays from an ordered arrangement of scattering centers (such as the environment present in crystals) leads to diffraction. The use of x-ray diffraction for characterizing powders is described in the next section. The absorption of x-rays leads to electronically excited atoms (ions) due to the ejection of electrons (i.e., the photoelectric effect) or to the transition of electrons to higher energy levels (Fig. 3.16a). (The ejected electrons, as described later, form the basis for the surface characterization technique of x-ray photoelectron spectroscopy.)... 

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