Infrared micro-spectroscopy materials

Three different ZSM-5 crystal types have been studied by synchrotron infrared micro-spectroscopy, namely parent zeolite (ZSM-5-P), mildly treated zeolite (ZSM-5-MT) and severely treated zeolite (ZSM-5-ST). The goal is to compare the influence of different dealumination conditions on the molecular diffusion and reactivity of individual ZSM-5 crystals. Synchrotron-based IR micro-spectroscopy [34] was used in combination with pyridine adsorption. Pyridine, having a molecular dimension of 0.57 nm, is able to diffuse throughout the micropore system of ZSM-5 and allows the detection of all acidic sites present within the zeolite material [35]. The sorption of pyridine was introduced at room temperature and the samples were subsequently heated up to 573 K and 673 K. The Bronsted acid sites, giving rise to IR spectra of adsorbed pyridine at around 1545 cm , allow the visualization of differences in the nature and strength of the acid sites in the zeolite crystals under investigation. Fig. 4 shows the IR spectra of the adsorbed pyridine collected at room temperature, 573 K and 673 K for the ZSM-5-P, ZSM-5-MT and ZSM-5-ST crystals. 

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

However, over the last decade, important advances have been made in IR micro-spectroscopy with a synchrotron source [16], which can provide new opportunities and motivation for the study of polymeric materials. The most utilized key synchrotron parameter for this community is the ability, thanks to the source brightness, to differentiate the chemical nature of the constituents in multicomponent polymeric systems. When the sizes of the different domains are in the range of the IR wavelength (micron scale), the spatial differentiation and study of each of these domains is possible using SR-FTIR micro-spectroscopy. Such analytical tools allow the study of various aspects related to the chemical composition, structure and morphology of the polymeric materials. Some of the areas that have benefited from synchrotron infrared over the last four years are reviewed in this section. 

Time-resolved in-situ micro-infrared spectroscopy was applied for the first time by Nowotny et al. [862] on a process occurring in a zeolite single crystal. These authors monitored the thermal decomposition of the template (tripropylamine, TPA) in single crystals of MFI materials with nsi/n i ratios below 1000 (silicalite-1), 122, and 31 (ZSM-5). Bands of the CH stretching modes at 2981, 2943,2882 and 2746 cm and of the CH bending vibrations at 1473 and 1458 cm" were observed. From the presence of the latter two bands the authors concluded that at ambient temperature TPA is rather immobile in the channels of the as-synthesized ZSM-5 crystals. From their measurements they arrived at the conclusions that... 

Other useful microscopic analytical techniques include hot stage, fluorescence, and cathodolumines-cence microscopies micro-infrared spectroscopy micro-Raman spectroscopy ultraviolet-visible microspectrophotometry and X-ray diffraction however, the discussion of these techniques is beyond the scope of this article. Briefly stated, each of these techniques can be used to ascertain additional information about characteristic properties of a material. The microscopist must be aware of all of these techniques, and others, so as to be able to extract the necessary information from a sample when the need arises. 

Two major fillers used in the rubber industry are silica and carbon black. Carbon black is black because it absorbs/scatters all radiation, including infrared, impinging on it. Hence, simple transmission spectroscopy of carbon black filled specimens is not straightforward and is usually not possible unless the samples are very thin. Carbon black filled samples have not been readily examinable using micro-spectroscopic methods. Silica filled systems are more amenable to microscopic techniques [76] and can be examined to determine silica-polymer(rubber) interactions. The presence of inorganic materials, e.g., transition metal complexes in... 

Merging of spectroscopy with microscopy has generated an entirely new discipline, termed microspectroscopy, which allows measurement of the spatial distribution of chemical stractures in materials. Microspectrophotometry (MSP), primarily in the UVAHS and NIR ranges (220 to 2500 nm), has been practised in some way since the 1930s with emphasis on the microscope functionality [368, 369]. On the other hand, the recent convergence of infrared with microscopy accentuates the spectroscopic functionality. Microspectroscopy is a powerful tool for characterisation of micro samples, for examination of heterogeneous materials and for analysis of processes such as migration that involve spatial... 

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