Post characterization techniques

This chapter provides a concise summary of the most important concepts and characteristics of CNTs including structural aspects (i.e. chirality, defects, doping), properties (i.e. mechanical, electronic, thermal), synthesis and characterization techniques and post-processing strategies (i.e. purification, separation, functionalization), and is thus intended as an introduction for newcomers. 

Since most zeolites are only available as polycrystalline phases, powder diffraction is an essential structural characterization technique. A powder diffraction pattern can be used to identify a material, to determine unit cell parameters, to estimate the quality of a sample, to monitor phase transitions, to evaluate whether or not a post-synthesis treatment has induced structural changes, to establish whether or not impurities (amorphous or crystalline) are present, or to recognize the presence of a significant level of faulting. 

Although indicative of the semiconductor-metal transition, the conductivity data alone cannot be accepted as rigid proof of the formation of Si-II during indentation. Unfortunately, due to obvious complications with the experimental setup, no in situ indentation diffraction data are available as of today. On the other hand, a number of papers provide indirect evidence of the Si-I -> Si-II transformation during indentation based on the post-indentation characterization techniques. We will start with a discussion of the electron microscopy results. 

Unfortunately, up to now only limited information has been pubhshed about post-test analysis, methods, and results, and this is trae of our own research center in addition to any other developer, be it companies or R D centers [1-4]. Only single effects after stack operation, single-cell testing, or model experiments and theoretical considerations have been published, such as metal corrosion, Cr poisoning, and thermodynamics [5-15]. Therefore, this chapter summarizes for the first time the stack dissection method, the underlying reasons for stack post-test analysis, the individual characterization techniques and methods, and the results obtained so far. 

In conclusion, these results are an excellent platform for the further development of processing tools for small nanoparticles below 20 nm. We investigated highly relevant aspects of the process chain that needs to be considered. After having established a comparatively easy and in situ applicable characterization technique for quantum confined semiconductor nanoparticles, we analyzed the particle formation mechanism and different aspects of colloidal stability. The latter included agglomeration phenomena but also shape transformations and shape stability. Finally, post-processing was addressed via classification by size selective precipitation (SSP) (Scheme 1). 

In summary, the order and microstructure of P3HT thin films is extremely sensitive to the solvents used, deposition craiditions, and post-depositirMi treatment. This can pose a problem for reproducibility but also enables wide tunability of transport properties with the same polymer. Hence, careful control of all processing parameters and complementary characterization techniques are crucial before drawing any conclusions from device characteristics. 

Other samples even showed a small increase, resulting in post-irradiation waters having an increased contribution of protein-like relative to humic-like components in comparison to initial waters (Cory et al., 2007). Whole water samples in freshwater systems also typically show a decrease in FI with irradiation. The variation in FI has been shown to be related to relative amounts of SQl and SQ2 in a sample and thus the decrease in H with irradiation time can be attributed to the greater loss of SQ2 in comparison to SQl in Figure 3.10 (Cory et al., 2007). Fluorescence characterization of DOM can help understand how photochemical processes influence DOM quantity and quality, and utihzing spectrophotometric techniques in comparison with other DOM characterization techniques shows promise for understanding how photochemical processes remove and modify DOM in aquatic systems (Spencer et al, 2009a Stubbins et al, 2010). 

SIMS is one of the most powerful surface and microanalytical techniques for materials characterization. It is primarily used in the analysis of semiconductors, as well as for metallurgical, and geological materials. The advent of a growing number of standards for SIMS has gready enhanced the quantitative accuracy and reliability of the technique in these areas. Future development is expected in the area of small spot analysis, implementation of post-sputtering ionization to SIMS (see the articles on SALI and SNMS), and newer areas of application, such as ceramics, polymers, and biological and pharmaceutical materials. 

The large variability in elemental ion yields which is typical of the single-laser LIMS technique, has motivated the development of alternative techniques, that are collectively labeled post-ablation ionization (PAI) techniques. These variants of LIMS are characterized by the use of a second laser to ionize the neutral species removed (ablated) from the sample surface by the primary (ablating) laser. One PAI technique uses a high-power, frequency-quadrupled Nd-YAG laser (A, = 266 nm) to produce elemental ions from the ablated neutrals, through nonresonant multiphoton ionization (NRMPI). Because of the high photon flux available, 100% ionization efflciency can be achieved for most elements, and this reduces the differences in elemental ion yields that are typical of single-laser LIMS. A typical analytical application is discussed below. 

Resonant and non-resonant laser post-ionization of sputtered uranium atoms using SIRIS (sputtered initited resonance ionization spectroscopy) and SNMS (secondary neutral mass spectrometry) in one instrument for the characterization of sub-pm sized single microparticles was suggested by Erdmann et al.94 Resonant ionization mass spectrometry allows a selective and sensitive isotope analysis without isobaric interferences as demonstrated for the ultratrace analysis of plutonium from bulk samples.94 Unfortunately, no instrumental equipment combining both techniques is commercially available. 

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