Some characterization techniques

Case Western Reserve University, Cleveland, Ohio 44106, USA 

Most polymers are complex mixtures of materials of various sizes (relative molecular masses) and chemical compositions and with various end groups and molecular architectures. Thus, synthetic and biological polymers present a particularly difficult problem for molecular characterization due to the multicomponent nature of the systems. In practice, no single spectroscopic or analytic technique is sufficient for the complete determination of all of these structures and distributions. 

The purpose of this chapter will be to indicate the molecular-spectroscopic methods and approaches required for the determination of the chemical structure of the 

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In this chapter, we will introduce some typical carbon materials that are widely studied in electrochemistry. Their properties, not restricted to their electrochemical properties, will be briefly described. Some characterization techniques, including spectroelectrochemistry, will be described when applied to selected carbon materials. A brief overview of the application of various carbon materials to electrochemistry will be included in this chapter, which will be concluded by an outlook to the future. 

In many respects, the characterization of the consolidation of ceramic thick films is similar to that of bulk ceramics, which is discussed in Chapter 5. However, several important features of thick films make them unique. Their small thicknesses make some characterization techniques inapplicable and sample preparation for other characterization techniques more difficult. Also, in both screen-printed and tape-cast structures, the ceramic thick film is in intimate contact with one or more dissimilar materials such as a metal. This contact can produce interdiffusion and reactions between these phases. 

The third edition of this well-known textbook discusses the diverse physical states and associated properties of polymeric materials. The contents of the book have been conveniently divided into two general parts, Physical states of polymers and Some characterization techniques. ... 

The process of characterization can be defined as determining some characteristic or property of a material in a defined and reproducible way. Some characterization techniques for substrate surfaces were discussed in Sec. 2.4. Characterization can be at all levels of sophistication and expense. Before spending a lot of money characterizing a film (or substrate), you should ask yourself several questions, namely ... 

Surface active electrolytes produce charged micelles whose effective charge can be measured by electrophoretic mobility [117,156]. The net charge is lower than the degree of aggregation, however, since some of the counterions remain associated with the micelle, presumably as part of a Stem layer (see Section V-3) [157]. Combination of self-diffusion with electrophoretic mobility measurements indicates that a typical micelle of a univalent surfactant contains about 1(X) monomer units and carries a net charge of 50-70. Additional colloidal characterization techniques are applicable to micelles such as ultrafiltration [158]. 

However, it yields dynamic modulus. Some other techniques were also used to characterize hydrogels, for example, viscoelastic measurements [28, 30, 31] and swelling equilibrium [20]. 

After a temptative structure-based classification of different kinds of polymorphism, a description of possible crystallization and interconversion conditions is presented. The influence on the polymorphic behavior of comonomeric units and of a second polymeric component in miscible blends is described for some polymer systems. It is also shown that other characterization techniques, besides diffraction techniques, can be useful in the study of polymorphism in polymers. Finally, some effects of polymorphism on the properties of polymeric materials are discussed. 

Although the diffraction techniques are unique in providing detailed information on the structural organization at the molecular level in the different crystalline forms, there are other characterization techniques which are sensitive to the chain conformation and in some cases to the chain packing, which can be used advantageously (and in some case more efficiently than diffraction techniques) in the recognition and quantification of the different polymorphs in polymeric materials. 

Dendrimers have been characterized by a variety of general techniques of analytical chemistry, and also by some specialized techniques that are particularly suitable for dendrimers. The following sections describe these techniques as they have been applied to dendrimers. For more details, the reader is referred to the books fisted in Further Reading section. 

Figure 4.3 shows some statistics on the use of characterization techniques in catalysis. In this chapter we briefly introduce the most important of these methods and illustrate their use. Further examples can be found in subsequent chapters and in J.W. Niemantsverdriet, Spectroscopy in Catalysis, An Introduction (2000), Wiley-VCFI, Weinheim. 

The difficulty is that characterization techniques are usually not selective towards active sites, so very often the main spectroscopic features are not evidence for active sites manifestations. However, it is possible to find some exceptions mainly among functionalized materials, such as zeolites. One of the few well established examples is TS-1 [7], a zeolite discovered in 1983 behaving as a catalyst for partial oxidation reactions in H2O2/H2O solutions [8-20]. 

After purification, the bimetallic nanoparticles are offered to characterization. The characterization techniques were well reviewed previously in literatures [1,2]. In this section, we highlight recent reports on the characterization methods of bimetallic nanoparticles after presenting some previous researches again. 

In this paper we have endeavored to present a review of some characterization methods of metal nanoclusters, focusing, among the extremely vast array of methods and techniques, on two of them, XRD and TEM, on which we have direct experience, and emphasizing also some recent developments, like the radial distribution function in XRD and EH in TEM. 

In Appendix A, for the sake of clarity, we reported some of the acronyms used throughout the text, whereas in Appendix B a brief description of the experimental characterization techniques used for the present work is added. 

Microanalysis is the common name used to refer to a variety of techniques for identifying, characterizing, and evaluating minute amounts of materials. Some microanalytical techniques are scaled-down versions of well-known conventional or physical analytical techniques others are specialized techniques that can be implemented only on extremely small samples. Table 11 lists the minimum size of samples required for microanalysis and the minimum amount of substance detectable by microanalytical techniques (Janssens and Van Grieken 2004). 

The selection of an analytical technique that allows for the chemical characterization of a contamination or defect that is a potential contributor to a failure is influenced by some major factors. For example, some techniques are able to characterize inorganic materials, while other techniques are better suited for organic materials. Further, some analytical techniques require that the specimen be volatile, other techniques require that the sample be soluble, and still other techniques require that the sample be in a solid form. 

Some of the major questions that semiconductor characterization techniques aim to address are the concentration and mobility of carriers and their level of compensation, the chemical nature and local structure of electrically-active dopants and their energy separations from the VB or CB, the existence of polytypes, the overall crystalline quality or perfection, the existence of stacking faults or dislocations, and the effects of annealing upon activation of electrically-active dopants. For semiconductor alloys, that are extensively used to tailor optoelectronic properties such as the wavelength of light emission, the question of whether the solid-solutions are ideal or exhibit preferential clustering of component atoms is important. The next... 

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... 

Experimental Pitfalls. Several types of systematic inaccuracies in nonlinear optical susceptibility characterization techniques have appeared in the literature due to incomplete analysis of propagation effects. It is believed that use of the above models make them more obvious. Some examples are described in this section. 

Catalyst characterization is a lively and highly relevant discipline in catalysis. A literature survey identified over 4000 scientific publications on catalyst characterization in a period of two years [14]. The desire to work with defined materials is undoubtedly present. No less than 78% of the 143 papers presented orally at the 1 llh International Congress on Catalysis [15] contained at least some results on the catalyst(s) obtained by characterization techniques, whereas about 20% of the papers dealt with catalytic reactions over uncharacterized catalysts. Another remarkable fact from these statistics is that about 10% of the papers contained results of theoretical calculations. The trend is clearly to approach catalysis from many different viewpoints with a combination of sophisticated experimental and theoretical tools. 

In this chapter, we introduce some of the most common spectroscopies and methods available for the characterization of heterogeneous catalysts [3-13], These techniques can be broadly grouped according to the nature of the probes employed for excitation, including photons, electrons, ions, and neutrons, or, alternatively, according to the type of information they provide. Here we have chosen to group the main catalyst characterization techniques by using a combination of both criteria into structural, thermal, optical, and surface-sensitive techniques. We also focus on the characterization of real catalysts, and toward the end make brief reference to studies with model systems. Only the basics of each technique and a few examples of applications to catalyst characterization are provided, but more specialized references are included for those interested in a more in-depth discussion. 

This section provides brief insights on some of the most important characterization techniques used for CNTs and other nanocarbons in addition to microscopy-related (i.e. SEM, TEM, AFM, STM) and diffraction (i.e. X-ray, electron) techniques. 

Analytical scientists will provide support for many of the activities in a biopharmaceutical company. They are responsible for characterizing the molecules in development, establishing and performing assays that aid in optimization and reproducibility of the purification schemes, and optimizing conditions for fermentation or cell culture to include product yields. Some of the characterization techniques will eventually be used in quality control to establish purity, potency, and identity of the final formulation. The techniques described here should provide the beginning of a palette from which to develop analytical solutions. 

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