Characterization techniques

In each step in the development of an advanced nanotechnology system/ apparatus the characterization of the nanomaterials and nanostructures 

21 Carbon coating deposited on the carbon-carbon composite using the TCVD method. Using ceramic materials, with the same technology, it is possible to produce a coating with high mechanical, thermal and chemical characteristics useful for hybrid composite materials employed in space vehicles (for the re-entry phase mission in which the thermal and oxidation conditions are extreme).  

Several analytical characterization tools have been used successfully in past to determine the principal properties of nanostructures and nanomaterials, but a lack of standard methodologies makes it difficult to compare these measurements. The development of a protocol in which standardized analysis methods and procedures are defined is needed. Typical characterization analyses used in the nanotechnology science are  

It is clear that the numerous nanomaterials/structures, available due to the different nanotechnologies developed and modified by different processes (synthesis, purification, integration, etc.), demand close examination when they are used for each application. It is fundamental to have a well-characterized material in order to access the variability of the numerous steps required in the design and development of the previously mentioned applications. For example, the nanocomposite material s preparation and evaluation require measurements that can follow the matrix before and after the addition of nanostructures (e.g. carbon nanotubes). There is a strong need for standard methods to characterize the nanomaterials in order to improve the capability of comparing different samples employed as raw materials. The requested protocol must be characterized by a standard procedure useful for performing a short nano-elements characterization, with high reliability levels. 

This section illustrates the techniques available and the typical uses  

Multinuclear NMR is not only a potential and unique technique for the structural and stereochemical characterization of homometallic Sn(II) complexes, but also for oligometallic derivatives having more than one metallic element, provided that the other metal(s) is(are) NMR active. There are several NMR 

Mass spectrometry can give valuable information on the structural details of Sn(II) heterometallic derivatives, subject to stability with respect to the disproportionation reaction in the vapor phase. The mass spectral results demonstrate that fast atom bombardment mass spectrometry (FARMS) could find immense applications in the characterization of heterometallic derivatives, particularly of non-volatile, high molecular weight compounds, such as those of tin. 

Finally, elemental analysis results may pose difficulties in arriving at the correct composition of tin(II) heterometallic compounds due to changes in metal-ligand ratio. However, with the help of X-ray structural analysis, the CHN results may prove fruitful to prove the stoichiometry of the heterometallic species. 

For the use in catalysis, characterization of G materials requires the combination of typical imaging techniques to prove the 2D morphology and the single layer configuration of G, plus characterization of the activity of the active sites. For characterization of G materials the information provided by, at least, four different techniques, namely Raman and XPS, electron microscopy, and atomic force microscopy (AFM) are required. Raman spectroscopy should show the three 2D, G, and D bands present 

XPS is a technique that has been found extremely useful for the study of carbon materials including G, XPS should give a quantitative analytical atomic composition of G, detecting and quantifying the presence of heteroatoms, particularly oxygen, but also other dopant elements. 

Similarly, nitrogen should be detectable in N-doped G and deconvolution of the experimental N Is XPS peak should inform about the absolute 

The above characterization techniques, however, do not indicate the presence of active sites able to promote catalytic reactions. Depending of the nature of active site general techniques widely applied for solid catalysts could also be in principle applied to G-based catalyst. For instance, acidity and basicity are two of the most important properties from the point of view of catalysis. Many different reaction types including additions, substitutions, condensations, rearrangements, etc. can be catalyzed by these types of sites. Also in G catalysts, acid or basic sites can be present and can participate in the reaction mechanism. Therefore, quantification of the density of these sites and a qualitatively measurement of their strength is very important. 

In those cases in where G is acting as support of active sites such as metal NPs, then the typical techniques for this type of NPs, as for instance 

Spectroscopic measurement is a particularly favored analytical technique because spectra can be compared in a direct way to interpret the chemical and mineralogical composition of dust in various astronomical environments. Depending upon the different spectral regions under analysis and depending on the optical properties of the material, one must use different techniques. In regions of strong absorption, such as in the phonon band range (mid-infrared) or the ultraviolet, direct absorption measurements require very low column densities of material, which can only be achieved with thin films or diluted powder samples. 

Thin films of silicates have been produced by pressing powders in a diamond anvil cell (Hofmeister 1997), by cutting grain samples to submicron thick slices with an ultra-microtome (Bradley et al 1999), by electron-beam evaporation (Djouadi et al. 2005), and by laser deposition in a vacuum (Brucato et al. 2004). On one hand, powders produced in a laboratory are directly measured in transmittance when they are embedded in a matrix of transparent materials (e.g. KBr or polyethylene). On the other hand, reflectance measurements do not require the use of matrices powders of selected-size grains are directly measured with an appropriate optical accessory. Through measurements in both transmittance and reflectance, it is possible to evaluate the optical constants of a material. These are certainly the physical parameters 

In situ Raman spectra of amorphous carbon grains irradiated with 3 keV He+ ions at different fluences are reported in Fig. 5.1 The amorphous carbon grains have been produced by arc discharge between two amorphous carbon electrodes in an inert argon atmosphere. Transmission electron microscopy (TEM) studies 

Most primary condensates are extremely small, ranging from 5 nm to 50 nm in diameter. Adequate characterization of such grains must rely on very high spatial resolution techniques such as transmission electron microscopy (TEM) or analytical electron microscopy (AEM). In the former technique, the emphasis is on obtaining very clear pictures of the morphology, homogeneity, elemental and mineralogical 

One of the prindpal issues complicating the synthesis and characterization of clusters in zeolites is the simultaneous formation of clusters or crystallites outside the zeolite crystals. In many preparations this is apparently unavoidable, yet most of the literature on zeolite supported clusters does not even address this issue. Much of the reported work on metal carbonyl clusters in zeolites has failed to include evidence which should establish whether all the clusters were actually confined within the cages. Characterization techniques are needed which can differentiate between the entrapped entities and those outside the pores by probing the ligand sphere and the metal spedes. 

Most of the characterization methods discussed here are based on comparisons of spectra of entrapped spedes with those of well characterized reference compounds found in solution or in the solid state. The methods work best when the references have been structurally characterized by X-ray diffraction crystallography. Without good models for the entrapped spedes, structures inferred on the 

Metal Precursor Method Quster/Zeolite Characterization Refs. 

Metal Precursor Method Cluster/Zeolite Characterization Refs. 

Pt Pt(NH3)4Cl2 ion exdiange followed by CO treatment [Pt,2(CO)24) -VNaY IR, UV-vis, EXAFS u 

Poly(p-phenylene vinylene) (PPV) is a conjugated polymer, which becomes conductive by the addition of electron donors or acceptors [114, 115], Several methods have been reported for the synthesis of PPV [3, 4, 6], Direct chemical polymerization, which was used in the first attempt of synthesizing PPV, gave a product in the form of an insoluble powder that limited the use of the polymer in many applications [116], The most popular method for the preparation of PPV is base-induced polymerization of sul-fonium salt monomer in aqueous solution [114-118], In this method, PPV films are obtained from the precursor polymer after thermal elimination of the sulfonium groups. PPV has also been prepared electrochemically by reducing p-xylene-bis-(triphenylphosphonium). Two approaches are generally used for the synthesis of PPVs the Wessling 

Although many techniques to synthesize high molecular weight PPVs exist, they are largely limited to the synthesis of predominantly fran -PPVs [125]. Recent work by Katayama and Ozawa [126, 127] has, for the first time, provided access to all cw-PPVs by way of a stereospecific 

Suzuki-Miyaura cross-coupling polymerization of 1,4-bis((Z)-2-bromovinyl)benzenes with aryl-bis-boronic acids. The interest has been in an alternative approach, where rather than building a PPV with a pre-ordained stereochemistry, a postpolymerization yyn-selective reduction on a poly(phenylene ethynylene) (PPE) is used [125]. This scheme has the advantage that high molecular weight PPEs can be synthesized using either Pd-catalysis or alkyne metathesis. This route could also potentially allow for the access to an additional array of PPVs that are uniquely accessible from PPEs. The transformation of the triple bonds in PPEs and other acetylene building blocks to alkenes has considerable potential. 

As most other polymers, conducting polymers can be characterized through a variety of analytical techniques. Many examples exist in the literature, some of which include the following  

cyclic voltammetry, for understanding redox processes in conducting polymers and evaluating potential battery and electrochromic window material candidates  

To characterize the thermal stability of PNCs, TGA data was collected on a TA Instruments Q50, at a heating rate of lO Cmin . Samples were heated up to 800 °C under a flow of 25 ml min nitrogen to study nonoxidative degradation, and under a flow of 25 ml min air to study oxidative degradation. 

In the surface modification, normally other elements are induced. The element identification approaches often are used to identify the surface modification. For instance. X-ray photoelectron spectroscopy (XPS) was used to study the surface change after plasma treatment of the PDMS surface [21]. The infrared spectrometry (IR) was used to 

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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]. 

Other important characterization techniques include electrophoresis measurements of droplets [11, 12] (see Section XIV-3C), infrared absorption of the constituent species [13], and light or x-ray scattering. NMR self-diffusion measurements can be used to determine droplet sizes in W/0 emulsions [14]. 

It is now a practice to use a variety of surface characterization techniques in the study of chemisorption and catalysis. The examples given here are illustrative most references in this section as well as throughout the chapter will contain results from several techniques. 

There are a few other surface-sensitive characterization techniques that also rely on the use of lasers. For instance surface-plasmon resonance (SPR) measurements have been used to follow changes in surface optical properties as a fiinction of time as the sample is modified by, for instance, adsorption processes [ ]. SPR has proven usefiil to image adsorption patterns on surfaces as well [59]. 

Although the teclmiques described undoubtedly provide valuable results on various materials, the most useful infonuation almost always comes from a combination of several (chemical and physical) surface characterization techniques. Table B1.25.1 gives a short overview of the techniques described in this chapter. 

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Over a period of about 50 years, the science of polymer chemistry has developed a comprehensive means of polymer characterization techniques. In the case of PE, these parameters include the composition, molecular weight, and compositional distribution. The composition of ethylene copolymers is usually measured by C-nmr, H-nmr, or in techniques. 

Materials characterization techniques, ie, atomic and molecular identification and analysis, ate discussed ia articles the tides of which, for the most part, are descriptive of the analytical method. For example, both iaftared (it) and near iaftared analysis (nira) are described ia Infrared and raman SPECTROSCOPY. Nucleai magaetic resoaance (nmr) and electron spia resonance (esr) are discussed ia Magnetic spin resonance. Ultraviolet (uv) and visible (vis), absorption and emission, as well as Raman spectroscopy, circular dichroism (cd), etc are discussed ia Spectroscopy (see also Chemiluminescence Electho-analytical techniques It unoassay Mass specthot thy Microscopy Microwave technology Plasma technology and X-ray technology). 

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. 

Rutherford back-scattering spectroscopy (RBS) is one of the most frequently used techniques for quantitative analysis of composition, thickness, and depth profiles of thin solid films or solid samples near the surface region. It has been in use since the nineteen-sixties and has since evolved into a major materials-characterization technique. The number and range of applications are enormous. Because of its quantitative feature, RBS often serves as a standard for other techniques. 

ReflEXAES can be used for near-surface structural analysis of a wide variety of samples for which no other technique is appropriate. As with EXAES, ReflEXAES is particularly suited for studying the local atomic structure around particular atomic species in non-crystalline environments. It is, however, also widely used for the analysis of nanocrystalline materials and for studying the initial stages of crystallization at surfaces or interfaces. ReflEXAES was first proposed by Barchewitz [4.135], and after several papers in the early nineteen-eighties [4.136, 4.168-4.170] it became an established (although rather exotic) characterization technique. Most synchrotron radiation sources now have beam-lines dedicated to ReflEXAES experiments. 

An important part of any cat crackings correlations package is an accurate feed characterization technique. Feed characterization is vital since it quantifies... 

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. 

The data presented in Figure 8 graphically illustrate the tremendous and rapid growth in interest in FOSS chemistry, especially for patented applications. This looks set to continue with current applications in areas as diverse as dendrimers, composite materials, polymers, optical materials, liquid crystal materials, atom scavengers, and cosmetics, and, no doubt, many new areas to come. These many applications derive from the symmetrical nature of the FOSS cores which comprise relatively rigid, near-tetrahedral vertices connected by more flexible siloxane bonds. The compounds are usually thermally and chemically stable and can be modified by conventional synthetic methods and are amenable to the usual characterization techniques. The recent commercial availability of a wide range of simple monomers on a multigram scale will help to advance research in the area more rapidly. 

When chromium atoms were cocondensed at 77 K with 1,7-cyclodeca-diyne (38), complexation was not observed however, an organic trimer of the starting material was formed. Standard, organic characterization-techniques showed that this trimer is the one depicted, rather... 

Selective oxidation of p-xylene to terephthaldehyde (TPAL) on W-Sb oxide catalysts was studied. While WO3 was active in p-xylene conversion but non-selective for TPAL formation, addition of Sb decreased the activity in p-xylene conversion but increased TPAL selectivity significantly. Structure change was also induced by Sb addition. Evidences from various characterization techniques and theoretical calculation suggest that Sb may exist as various forms, which have different p-xylene adsorption property, reactivity toward p-xylene and TPAL selectivity. Relative population of each species depends on Sb content. 

In the past three decades, industrial polymerization research and development aimed at controlling average polymer properties such as molecular weight averages, melt flow index and copolymer composition. These properties were modeled using either first principle models or empirical models represented by differential equations or statistical model equations. However, recent advances in polymerization chemistry, polymerization catalysis, polymer characterization techniques, and computational tools are making the molecular level design and control of polymer microstructure a reality. 

The first attempt to synthesize and characterize Kegj -type heteropoly acid supported on various mesoporous silicas and its application to add catalysis in the formation of acetic anhydride via dehydration of acetic acid were described in this study. A variety of characterization techniques such as Na adsorption, TEM and XRD were applied... 

Figure 4.2. Catalyst characterization techniques The circle represents the sample under study, the inward arrows denote excitation processes, and the outward arrows indicate how the information should be extracted.

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. 

Number of times characterization techniques were used at the ICC Baltimore 1996... 

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