BULK CHARACTERIZATION TECHNIQUES

The majority of characterization techniques discussed thus far have been surface-related, with some capable of analyzing sub-surface depths through in situ ion etching. This final section will focus briefly on a selection of common bulk techniques that may be used to characterize as-synthesized materials such as polymers, ceramics, etc. More details on these and other techniques not discussed herein may be found in the Further Reading section at the end of this chapter. In particular, these additional resources, as well as countless others online, will highlight solid-state characterization techniques such as  

More information on the components and operation of reflection microscopes may be obtained from 

Mass of a Golf Ball http //hypertextbook.com/facts/1999/ImranArif.shtml 

It is important to note the general trend of decreasing wavelength (and greater resolution) as the velocity of electrons is increased (/.e., higher accelerating voltages). 

For example, see http //accelconf.web.cern.ch/AccelConf/p05/PAPERS/WOAC001.PDF O Dwyer, C. Navas, D. Lavayen, V. Benavente, E. Santa Ana, M. A. Gonzalez, G. Newcomb, S. B. Sotomayor Torres, C. M. Chem. Mater. 2006,18, 3016. 

The majority of characterization techniques discussed thus far have been surface-related, with some capable of analyzing sub-surface depths through in situ ion etching. This final section will focus briefly on a selection of common bulk 

Though TGA/DSC and DMA are extremely useful for polymer characterization, these techniques provide no (direct) structural information. As an alternative, structural information such as conformational changes of noncrystalline macromolecules may be determined by small-angle scattering (SAS) techniques. 

IMPORTANT MATERIALS APPLICATIONS VII SO WHICH ACRONYM SHALL I CHOOSE  

Mcnje information cm the components and opeiadcm of reflection microsc s may be obtained from htlp //www.microscopyu.com/articles/dic/reflecteddicJitml 

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For a precipitated iron catalyst, several authors propose that the WGS reaction occurs on an iron oxide (magnetite) surface,1213 and there are also some reports that the FT reaction occurs on a carbide surface.14 There seems to be a general consensus that the FT and WGS reactions occur on different active sites,13 and some strong evidence indicates that iron carbide is active for the FT reaction and that an iron oxide is active for the WGS reaction,15 and this is the process we propose in this report. The most widely accepted mechanism for the FT reaction is surface polymerization on a carbide surface by CH2 insertion.16 The most widely accepted mechanism for the WGS reaction is the direct oxidation of CO with surface 0 (from water dissociation).17 Analysis done on a precipitated iron catalyst using bulk characterization techniques always shows iron oxides and iron carbides, and the question of whether there can be a sensible correlation made between the bulk composition and activity or selectivity is still a contentious issue.18... 

Limitations of bulk characterization techniques when applied to study catalytic reactions occurring at the surface. 

The crystallization of PEO was also unveiled at the level of individual lamellae in ultrathin films (278-280). It was observed that although lamellar growth rates were retarded in films thinner than 200 nm because of interfacial interactions, SFM provided the same qualitative and quantitative information as typically applied bulk characterization techniques on lamellar growth rates, lamellar thicknesses, and melting points. The Hoffman-Weeks extrapolation, the Gihhs-Thompson equation, and the Hoffman-Lauritzen theory were apphed and the results compared favorably to the corresponding hulk data. 

In summary, the Raman studies have provided a deeper understanding of the molecular structure and reactivity properties of bulk metal oxide catalysts during selective oxidation reactions. However, the fundamental insights have primarily been limited to the bulk properties of the bulk metal oxide catalysts. In order to obtain surface information about metal oxide catalysts with Raman spectroscopy (essentially a bulk characterization technique), it is necessary to look at chemisorbed species on the surface of bulk metal oxides (see Sec. VIII) or highly dispersed metal oxide systems such as supported metal oxide catalysts. 

For applied work, an optical characterization technique should be as simple, rapid, and informative as possible. Other valuable aspects are the ability to perform measurements in a contactless manner at (or even above) room temperature. Modulation Spectroscopy is one of the most usehil techniques for studying the optical proponents of the bulk (semiconductors or metals) and surface (semiconductors) of technologically important materials. It is relatively simple, inexpensive, compact, and easy to use. Although photoluminescence is the most widely used technique for characterizing bulk and thin-film semiconductors. Modulation Spectroscopy is gainii in popularity as new applications are found and the database is increased. There are about 100 laboratories (university, industry, and government) around the world that use Modulation Spectroscopy for semiconductor characterization. 

The substantial literature on the bulk characterization of porous materials using conventional techniques provides a useful foundation as a starting point for overlapping the basic physics of traditional materials analysis with the parameters that can be measured using NMR. 

Extensive experimental techniques have been developed for porous material characterization [1], including direct imaging [2-5] and bulk measurement techniques for the statistical properties of the pore space. NMR is one such bulk measurement that is both non-destructive and compatible with large samples. 

XPS has typically been regarded primarily as a surface characterization technique. Indeed, angle-resolved XPS studies can be very informative in revealing the surface structure of solids, as demonstrated for the oxidation of Hf(Sio.sAso.5)As. However, with proper sample preparation, the electronic structure of the bulk solid can be obtained. A useful adjunct to XPS is X-ray absorption spectroscopy, which probes the bulk of the solid. If trends in the XPS BEs parallel those in absorption energies, then we can be reasonably confident that they represent the intrinsic properties of the solid. Features in XANES spectra such as pre-edge and absorption edge intensities can also provide qualitative information about the occupation of electronic states. 

Qualitative characterization techniques are outlined as well as the development of quantitative methods for the determination of one polymorphic form in another at the bulk or dosage product level. 

Elemental and Structural Characterization Many oxidation reactions occur on mixed oxides of complex composition, such as SbSn(Fe)0, VPO, FePO, heteropolycompounds, etc. Very often the active surfaces are not simple terminations of the three dimensional structure of the bulk phases. There is need to extensively apply structural characterization techniques to the study of catalysts, if possible in their working state. 

In this paper it has been attempted to provide an introductory overview of some of the various nonlinear optical characterization techniques that chemists are likely to encounter in studies of bulk materials and molecular structure-property relationships. It has also been attempted to provide a relatively more detailed coverage on one topic to provide some insight into the connection between the macroscopic quantities measured and the nonlinear polarization of molecules. It is hoped that chemists will find this tutorial useful in their efforts to conduct fruitful research on nonlinear optical materials. 

In bulk heterojunction solar cells, the metal/semiconductor interface is even more complex. Now the metal comes into contact with two semiconductors, one p-type (typically the polymer) and one n-type (typically the fullerene) semiconductor. A classical electrical characterization technique for studying the occurrence of charged states in the bulk or at the interface of a solar cell is admittance spectroscopy. If a solar cell is considered as a capacitor with capacitance C, the complex admittance Y is given by... 

The organic dielectrics known as polyimides have been studied extensively by a variety of bulk characterizational techniques as a perusal of the literature will illustrate. Little has been published on their surface properties. X-ray photoelectron spectroscopy (ESCA) has been extremely useful for polymer characterization (, 7, ), In a previous paper ( ), we have reported the ESCA spectra of structurally different polyimides derived from both commercially available polyamic acid resins (DuPont s PI5878, PI2525, PI2550), and from laboratory synthesized polyamic acid resins. 

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