bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Flow Fractionation in Analysis of Polymers and Rubbers
Authors: Ratanathanawongs Williams S. Kim , Benincasa Maria‐Anna
Published: September 2006

Field‐flow fractionation (FFF) was conceived by J. Calvin Giddings in 1966 as a separation and characterization method for macromolecules, colloids, and particulates. Like chromatography, sample migration is caused by differential interaction with a field acting along an axis orthogonal to that of the transport liquid. Unlike chromatography, where separation is achieved by solutes partitioning between mobile and stationary phases, separation in FFF arises from the distribution of sample components in fluid laminae flowing at different velocities in a single phase. The different flow velocities, described by a parabolic profile, arise from the high aspect ratio of the FFF channel. Different types of fields can be used in FFF as long as they interact with some physicochemical property of the sample. The FFF channel design makes it highly suited for analyses of fragile aggregates, high‐molecular‐weight polymers, and gels. In comparison with packed columns, shear rates in the channel and the probability of plugging the channel are low. The ability of thermal FFF to differentiate polymers and latexes of different bulk and surface composition is unique among currently used separation techniques. The FFF family of techniques can provide a great deal of information about the sample but an initial time investment is often required for methods development.

In this article, the fundamental mechanism of FFF is shown at play in the separation and characterization of polymers and rubbers by the two techniques par excellence in this field: flow FFF and thermal FFF.
Infrared Spectroscopy in Analysis of Plastics Recycling
Authors: Eisenreich Norbert , Rohe Thomas
Published: September 2006

Plastics recycling recovers valuable materials to save natural resources which are limited in the long term. Reprocessing of the materials requires the identification of the various types of polymers. Difficulties in applying physical separation techniques led to the modification of methods of chemical analysis which have to be operated fast and reliably under harsh industrial environments favoring infrared (IR) methods.

In general, the plastic products to be handled can be separated into two main fractions. Domestic wastes contain only five relevant polymers in large quantities. Technical products use a broad variety of polymers containing fillers and additives, e.g. flame retardants, which also have to be identified to allow economic recycling.

Solid samples absorb IR radiation strongly, and the fundamental vibrations of the molecules are especially intense. The near‐infrared (NIR) spectral range with the overtone and combination bands is appropriate for analyzing bulky materials in reflection and transmission modes. The plastics from domestic wastes can be reliably identified by the first overtone of the CH bands between 1600 and 1800 nm. Extending this wavelength range to 1000 nm, technical non‐black plastics can also be treated. In the case of black plastics, which are often used in audio and video appliances, the mid‐infrared (MIR) spectral range has to be applied, owing to the reduced penetration depth of radiation into these materials. Also, larger amounts of additives such as plasticizers and flame retardants can be analyzed.

The identification of plastics from household waste requires fast scanning techniques in the millisecond range, especially if many samples are to be taken for one identification on movement. Mainly acousto‐optic tunable filter (AOTF) spectrometers or grating spectrometers with diode arrays can be applied. Germanium (Ge) and indium gallium arsenide (InGaAs) detectors with extended wavelength sensitivity cover the spectral range of interest. The movement excludes Fourier transform infrared (FTIR) spectrometers with e.g. indium antimonide (InSb) and mercury cadmium telluride (HgCdTe) diodes, but its application to technical plastics is possible because these pieces are heavier and can be identified in a fixed position.

Identification for recycling means a qualitative analysis. Simple algorithms such as those forming the differences of normalized spectra are sufficient for comparing measured with stored spectra. The performance of microprocessors also allows the application of more complex algorithms such as multivariate analysis or even neural networks. The use of NIR spectroscopy in industrial recycling started with application to sorting systems for plastics from household wastes or hand‐held sensors for cable recycling. The MIR technique still suffers from its sensitivity to harsh industrial environments and has been used only rarely and needs further development.
Infrared Spectroscopy in Analysis of Polymer Crystallinity
Authors: Mallapragada Surya K. , Narasimhan Balaji
Published: September 2006

This article provides a comprehensive review of the application of infrared (IR) spectroscopy in the analysis of polymer crystallinity. A brief description of the theory behind the analysis of orientation in polymers using IR spectroscopy is followed by a comparison of various sampling methods for Fourier transform infrared (FTIR) spectroscopy. These include transmission, attenuated total reflectance (ATR), external reflection, diffuse reflectance, photoacoustic and emission spectroscopic techniques. Various modes of measurement, such as polarized IR measurements, deuteration and rheo‐optical measurements to obtain more information from IR spectra and make the interpretation of spectra easier, are also discussed. The use of IR spectroscopy in analyzing both semicrystalline polymers and liquid crystalline polymers is presented. In the case of semicrystalline polymers, applications involve measuring phase transformations, chain conformation/packing, degree of crystallinity, crystallization kinetics, isomer ratios and chain alignment during mechanical treatment. In the case of liquid crystalline polymers, IR spectroscopy has been used to analyze molecular orientation, segmental mobility, photo‐induced reorientation and phase characterization/transformations. A comparison of IR measurements with other techniques used to analyze crystallinity in polymers such as X‐ray diffraction (XRD), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy and neutron scattering has been presented.
Infrared Spectroscopy in Analysis of Polymer Degradation
Authors: Edge Michele
Published: September 2006

Infrared (IR) spectroscopy locates the spectral position (frequency) and intensity of absorbed (or emitted) radiation arising from molecular transitions between quantum states associated with the vibrations and rotations of specific chemical groups. Using this technique both qualitative and quantitative information can be obtained on changes in the composition of polymers during degradation. The use of mathematical data‐processing techniques and instrumental attachments has enabled considerable progress to be made in this field,1–3where changes to the composition of the polymer structure are invariably complex. In conventional IR spectroscopy the light is dispersed and each wavelength is examined separately, whereas the main advantage of Fourier transform infrared (FTIR) spectroscopy is that the signal is multiplexed and each point of an interferogram contains information on all the wavelengths present, enabling all frequencies to be determined simultaneously. The increased speed and higher signal‐to‐noise ratio of FTIR spectroscopy is the prime advantage in the analysis of complex materials. The use of computational software to obtain difference or derivative spectra enhances the dynamic range. This is of particular value when monitoring polymer degradation, where the main interference is from the nondegraded structure of the polymer. The main disadvantage of IR spectroscopy in identifying and quantifying the functional group changes that take place during polymer degradation is that broad and rather featureless bands are frequently produced. As a consequence it is necessary to resolve individual components by subjecting the sample to a prior chemical treatment, or by the use of coupled instrumentation.
Coupled Liquid Chromatographic Techniques in Molecular Characterization
Authors: Kilz Peter , Pasch Harald
Published: September 2006

Complex polymers are distributed in more than one direction of molecular heterogeneity. In addition to the molar mass distribution (MMD), they are frequently distributed with respect to chemical composition, functionality, and molecular architecture (see Size‐exclusion Chromatography of Polymers). For the characterization of the different types of molecular heterogeneity it is necessary to use a wide range of analytical techniques. Preferably, these techniques should be selective towards a specific type of heterogeneity. The combination of two or more selective analytical techniques is assumed to yield multidimensional information on the molecular heterogeneity.

The present review presents the fundamental ideas of combining liquid chromatography (LC) with other analytical techniques in multidimensional analysis schemes (see Size‐exclusion Chromatography of Polymers; Gas Chromatography in Analysis of Polymers and Rubbers; Field Flow Fractionation in Analysis of Polymers and Rubbers). The capabilities and limitations of different coupling techniques are discussed and a number of relevant applications are given. It is shown that multidimensional structural information can be obtained when different chromatographic techniques are combined. Another approach is the hyphenation of LC with information‐rich detectors. These detectors include molar mass‐sensitive detection systems, such as on‐line viscometry (VISC) and light scattering (LS). Information on the chemical composition of complex polymers can be obtained when spectroscopic techniques, like Fourier transform infrared (FTIR) (see Infrared Spectroscopy in Analysis of Polymer Structure–Property Relationships), nuclear magnetic resonance (NMR) or mass spectrometry (MS) are coupled to LC.

The basics and applications of multidimensional LC are addressed rather extensively. A brief introduction to different separation mechanisms is given and the particular requirements for the first and second dimensions are discussed. In conclusion, state‐of‐the‐art examples for on‐line coupled two‐dimensional (2‐D) chromatography are demonstrated, and future developments are reviewed.
Nuclear Magnetic Resonance, Solid State in Analysis of Polymers and Rubbers
Authors: Mirau Peter A.
Published: September 2006

Solid‐state nuclear magnetic resonance (NMR) has emerged as one of the premier methods for polymer characterization in the solid‐state. High‐resolution spectra can be obtained with cross‐polarization and magic‐angle sample spinning using equipment that is commonly available on modern NMR spectrometers. Information about the chain structure, conformation, dynamics, intermolecular interactions and the morphology can be obtained by measuring the chemical shifts, line shapes and relaxation times. New experiments have been developed to filter the NMR response such that the spectrum from aparticular component can be measured. The resolution has been increased with the development of multidimensional NMR methods for measuring the structure and dynamics. Solid‐state NMR experiments can provide the link between the chemical structure and the macroscopic properties of polymers.
Pyrolysis Techniques in the Analysis of Polymers and Rubbers
Authors: Wampler Thomas P.
Published: September 2006

Pyrolysis is defined as a chemical degradation reaction induced by thermal energy only,
1
and analytical pyrolysis is the study of materials based on the results of such reactions. Since the overall result of a pyrolysis reaction is the production of small molecules from larger ones, it is extensively utilized in the analysis of polymers, especially as a sample introduction tool since it permits the application of techniques such as gas chromatography (GC) to such macromolecules by breaking them into fragments which are compatible with the technique. Interpretation of the results of a pyrolytic analysis depend on an understanding of the degradation mechanisms involved, which reflect relative bond strengths within the macromolecule. Since specific polymers are chemically different from each other, the degradation products they make are different, providing characteristic information about the original macromolecule. Analytical pyrolysis, coupled with GC, mass spectrometry (MS), gas chromatography/mass spectrometry (GC/MS), Fourier transform infrared (FTIR) spectroscopy and other techniques, has been used in the study of a wide range of polymer types, including polyolefins, vinyl polymers, polyurethanes, acrylics, rubbers, polyamides and polyesters.

Analytical laboratories employ one of a variety of pyrolysis techniques (microfurnace, resistively or inductively heated filament) interfaced to a detection instrument (GC, MS, FTIR) to create an analytical system. These combined systems have strengths and weaknesses based on the limitations of the individual components and must be optimized for a particular analysis. Systems have been devised which permit the routine analysis of such difficult materials as cured and cross‐linked paints and rubbers, textile fibers, filled composites, laminates, dried adhesives, copolymer systems, coatings and packaging. Practical applications are found in laboratories charged with the analysis of forensic evidence, museum artifacts, ink, paper, lubricants, automobile tires, clothing, varnish, wood products, furniture and food containers.
Temperature Rising Elution Fractionation and Crystallization Analysis Fractionation
Authors: Monrabal Benjamin
Published: September 2006

Temperature rising elution fractionation (TREF) and crystallization analysis fractionation (CRYSTAF) are separation techniques for the characterization of semicrystalline polymers in terms of chemical composition. TREF has become a powerful tool for preparative polymer fractionation and for the analysis of the chemical composition distribution (CCD) in polyolefins. CRYSTAF, a more recent technique and with a simple hardware design, provides a faster approach for the analysis of the CCD. Both TREF and CRYSTAF separate according to the crystallizability of the polymer molecules, which is influenced by tacticity or the comonomer incorporation into the chain. TREF and CRYSTAF are becoming specially relevant in the characterization of the new and complex polyolefins made with combinations of homogeneous and heterogeneous catalysts.
Chemometric Methods in Process Analysis
Authors: Booksh Karl S.
Published: September 2006

Chemometrics may be loosely defined as the development and application of mathematical and statistical techniques to aid in the analysis of chemical data. The goal of chemometrics is to guide the chemist in the optimum extraction of chemically relevant information from a series of complex chemically oriented observations. To this end, this article addresses a wide array of chemometric tools that are applicable to industrial process analysis. The three main sections present statistical and mathematical tools in the context of univariate, multivariate, and multiway analyses. Each of the three sections discusses the benefits and limitations of qualitative analysis, quantitative analysis, and process monitoring with the class of data in question. Additional sections address the appropriate pretreatment of collected data to aid in efficient analysis and validation of the derived chemometric models. In these sections methods for background correction and instrument standardization are discussed.
Nuclear Magnetic Resonance and Magnetic Resonance Imaging for Process Analysis
Authors: McCarthy Michael J. , Bobroff Serge
Published: September 2006

Nuclear magnetic resonance (NMR) spectroscopy is an experimental technique based on the interaction between nuclear magnetic moments and an applied magnetic field. The nuclei emit and absorb energy at a specific frequency that is proportional to the applied magnetic field. Magnetic resonance imaging (MRI) is the term used to describe the spatial resolution of NMR signals within a sample. NMR/MRI may provide information on the weight, chemical composition, physical properties, and structure of a sample. NMR is a noncontacting and noninvasive measurement. NMR and MRI are suitable for use in process control and have been applied to polymer processing, food processing and refinery processes. The response is linear from the detection limits of approximately 10 ppb to 100%. The accuracy of the technique depends on the signal‐to‐noise ratio (S/N), which is a function of the sample size, applied magnetic field strength, the radio‐frequency (rf) coil and the spectrometer hardware. Typical accuracy of the technique is 0.5% for measurements of composition and 1–5% for viscosity. NMR cannot generally be applied to magnetic or highly conductive materials.
Pulp and Paper Matrices Analysis: Introduction
Authors: Sitholé B. Bruce
Published: September 2006

The pulp and paper industry is a major player in the economies of many developed countries. As illustrated in Figure 1(a) and (b), the developed world accounts for more than 60% of the world output in pulp, paper and paperboard capacity. In one particular case, namely Canada, the industry contributes over 15% to the trade balance (see Figure 2). In order to ensure continual survival of the industry, it is necessary to continually improve and/or optimize the utilization of raw materials, the pulping processes, the papermaking process, the product quality properties and the protection of the environment. Analytical chemistry has an important role to play in the improvement and/or optimization of these parameters. This article summarizes how and where analytical chemistry is used, or can be used, to achieve the desired goals. Applications of analytical chemistry in the pulp and industry are reviewed in detail in the rest of the articles in this section on pulp and paper.
Carbohydrates from Chemical Pulps: Characterization by Capillary Zone Electrophoresis
Authors: Ristolainen Matti , Alén Raimo
Published: September 2006

Capillary zone electrophoresis (CZE) is one of the novel separation techniques, being applicable, for example, to virtually all important biomass‐derived monosaccharides. However, in spite of this fact the utilization of this technique in the pulp and paper industry is currently rather limited. In this chapter practical guidance and some application examples are given to show how carbohydrate material (polysaccharides, oligosaccharides, and neutral and acidic monosaccharides) in pulps and spent liquors can be analyzed by CZE. Emphasis is placed on sample preparation and separation conditions including comparison with other separation methods, such as gas chromatography (GC) and high‐performance liquid chromatography (HPLC), generally used for similar purposes. In addition, a short description of other significant degradation products (e.g. aliphatic carboxylic acids and lignin monomers) formed during delignification (e.g. cooking and bleaching) is given. It is concluded that these low‐molecular‐mass (LMM) degradation products could also be analyzed effectively by CZE.
Pulp and Paper Matrices
Authors: Douek Maurice
Published: September 2006

Chemical analysis plays an important role in pulp and paper research and in the day‐to‐day operation of pulp and paper mills. It is used in practically every aspect of the papermaking process, including the characterization of raw materials and products, optimization of process parameters, addressing environmental concerns, and diagnosing operation and product quality problems. This article provides an overview of the major types of chemical analyses conducted on pulp and paper matrices. The emphasis is mainly on the principle, significance, and applications of the various analyses. Major areas of application include the analysis of wood pulp, process liquids, paper, and deposits and contaminants. Analytical techniques and instrumentation range from the traditional or standard wet chemical and instrumental methods designed primarily for routine testing in mills to highly sophisticated techniques used mainly for research purposes.
Semiarid Land Assessment: Monitoring Dry Ecosystems with Remote Sensing
Authors: Hill Joachim
Published: September 2006

Semiarid lands belong to the world's dryland environments, which are permanently, seasonally or temporarily subjected to a significant deficit in moisture availability. Drylands, or dry ecological systems, include the proper deserts as well as their semiarid and subhumid dry margins. The areas referred to range from the cold polar deserts (which, because of their highly specific nature, are not considered in this article) to warm tropical deserts surrounded by tropical semiarid and subhumid drylands, including subtropical Mediterranean latitudes.

Remote sensing is the scientific approach to extracting information from an object without coming into physical contact with it. Broad definitions would need to include computer vision, astronomy, medical and biological imaging, sonar, observation of terrestrial and marine ecosystems and many other fields. Within the restricted context of this article we shall limit our perspective to collecting information about the state of terrestrial ecosystems through air‐ and space‐borne sensor systems. This process is based on the interaction of electromagnetic radiation with the surface constituents, and increasing knowledge about these interaction mechanisms makes it possible to interpret remotely sensed data with regard to specific environmental conditions and their change in time.
Imaging Spectrometry for Geological Applications
Authors: van der Meer Freek D.
Published: September 2006

Reflectance and emittance spectra have been used for many years to obtain compositional information about the Earth's surface. Electronic transition and charge transfer processes associated with transition‐metal ions such as Fe, Ti, Cr, and so on produce diagnostic absorption features in the visible and near‐infrared (VNIR) wavelength region of the spectra of minerals and rocks, while vibrational processes in H2O and OH−produce fundamental overtone absorptions in the shortwave infrared (SWIR) portion of the spectrum. Field and laboratory studies have demonstrated that reflectance spectroscopy can be used for mineral identification and further geological studies. The translation of these measurements to imaging data led to the development of the field of imaging spectrometry in remote sensing. Imaging spectrometers acquire images in a large number of narrow contiguous spectral bands to enable the extraction of reflectance spectra at a pixel scale that can be directly compared with similar spectra measured either in the field or in a laboratory. In this chapter, the use of imaging spectrometer data for geological applications is discussed by describing the processing chain of data analysis from the raw data acquisition to prospective applications. Several topics are addressed.

An appraisal of future spaceborne imaging spectrometer missions and potential prospective applications provides insight into this vastly growing field of research.
Land Cover Assessment and Monitoring
Authors: Lambin Eric
Published: September 2006

Land‐use changes are cumulatively transforming land cover at an accelerating pace, mainly in the tropics. These changes in terrestrial ecosystems are closely linked with the issue of the sustainability of socioeconomic development since they affect essential parts of our natural capital such as climate, soils, vegetation, water resources and biodiversity. Changes in terrestrial ecosystems brought about by human activity are driven by land cover conversion, land degradation, land‐use intensification or other forms of land cover modification. The term land cover refers to the attributes of a part of the Earth's land surface and immediate subsurface, including biota, soil, topography, surface and groundwater, and human structures. The term land use refers to the purposes for which humans exploit the land cover. One generally distinguishes between land cover conversion, the complete replacement of one cover type by another, and land cover modification, more subtle changes that affect the character of the land cover without changing its overall classification. Land cover modifications are generally more prevalent than land cover conversions. Two types of satellite sensors are used in land cover applications: fine spatial resolution systems and coarse spatial resolution/high temporal frequency systems. Data are collected in the visible, thermal and microwave ranges of the spectrum. Information in the spatial domain also provides valuable information on land surface attributes. These data are analyzed either for land cover mapping or for land cover monitoring. Current research is moving toward the direct estimation of biophysical surface parameters by model inversion methods. Multisensor approaches are also increasingly being developed.
Stellar Spectroscopy
Authors: Porter John M. , Steele Iain A.
Published: September 2006

Spectroscopy started with the examination of the Sun's light, making stellar spectroscopy the oldest branch of the subject. We describe modern stellar spectroscopy, and highlight some of the major successes in understanding the light output from stars and what we can deduce about the underlying objects. We present a description of stellar atmospheres considering the mechanical structure and the transport of energy. This leads on to a discussion of how the continuum and spectral lines of stellar spectra are formed and an explanation of the main features observed. The spectral lines observed in stellar spectra are then discussed and the information which can be obtained from examining their line shapes is examined. These include atmospheric pressure and temperature and both coherent and turbulent velocity fields (from stellar rotation and atmospheric convection currents). Magnetic fields, if large enough, may also be detected from careful examination of spectral lines.

Following a discussion of some practical aspects of observing stars, the main observational stellar classification scheme is presented, along with its interpretation regarding the underlying mass, radius, temperatures and evolutionary phase of the star. The effect of the chemical composition on line strengths is discussed, along with observational techniques of measuring it. The information which is obtained from different wavelength regimes – from radio waves to γ‐rays – is presented, along with possible difficulties associated with observing in each regime.

Finally, we discuss what we have learnt from examination of stellar spectra and the current state of theory which is applied to them.
Nuclear Magnetic Resonance in Metals Analysis
Authors: Neue Günther
Published: September 2006

Nuclear magnetic resonance (NMR) is a spectroscopic technique which uses the magnetic component (

B

1
) of radiofrequency (RF) electromagnetic fields to excite nuclear spins which are subject to a static magnetic field (

B

0
). The resonance frequency is proportional to this field. Most stable elements possess at least one isotope with spin I > 0 and, hence, are observable by NMR. Magnetic field gradients make it possible to label spatial coordinates within a sample. Magnetic resonance imaging (MRI) uses this principle to reconstruct images from NMR signals. Skin effect enhanced imaging nuclear magnetic resonance (SEEING‐NMR) derives its submicrometer resolution from the strong shielding properties of metals with respect to RF fields. Resonance frequencies of most isotopes are well separated from each other, making NMR an element‐specific technique. Interactions of spins with their local environment lead to characteristic spectral changes that reflect the chemical state, the physical state or local geometry. The possibility of coherent manipulation and detection of spin states allows for an extreme flexibility in designing new and highly selective NMR experiments. Integrated signal intensities are strictly proportional to concentrations. The disadvantage of NMR is the small signal‐to‐noise ratio, especially for nuclei that have low resonance frequencies. Except for sensitive isotopes like
1
H or
19
F, concentrations should therefore be higher than 1% and samples weighing 10 to 100 mg are recommended. The sensitivity to local interactions often makes it impossible to predict the visibility of NMR signals in unknown substances.
Differential Reflectance Spectroscopy in Analysis of Surfaces
Authors: Hummel R.E.
Published: September 2006

Differential reflectance spectroscopy (DRS) is a surface analytical technique. It uses ultraviolet (UV), visible, or infrared (IR) light as a probing medium. The interaction of light with “strongly absorbing materials”, such as metals, alloys, semiconductors, etc. occurs in the first 10–20 nm. Thus the differential reflectometer probes 50–100 atomic layers into nontransparent solid surfaces. Because of the specific probing depth of light, DRS fills the gap between other surface techniques such as ion‐scattering, Auger spectroscopy, and ESCA (electron spectroscopy for chemical analysis), which probe 1, 5, or even 20 monolayers, and X‐ray diffraction (XRD) which probes as deep as 1–50 µm into a bulk material. The information gained by DRS is somewhat different from that obtained by the other surface techniques mentioned. A “differential reflectogram” reveals details about the electron structure around the Fermi surface. Specifically, the instrument allows the exact measurement of the energies which electrons absorb from photons as they are raised into a higher, allowed energy states. Since each material has a specific electron‐band structure the measurement of the characteristic energies for electron “interband transitions” serves as a means for identifying these materials. Furthermore, investigation of any shift of these characteristic energies, which may be caused by the addition of solute elements to a solvent, by transformations, lattice defects, ordering, or the like, provides a deeper insight into the nature of the solid state. The application of DRS is, of course, not restricted to strongly absorbing materials such as metals, alloys, or semiconductors. Its strength has likewise been demonstrated in the identification and characterization of transparent or semitransparent surface layers as observed in thin‐film corrosion products on metal substrates. DRS is used to scan two samples whose properties differ slightly. Thus, the main advantage of DRS over conventional optical techniques lies in its ability to eliminate any undesirable influences of oxides, windows, electrolytes, instrumental variations, and the like, owing to the differential nature of the technique. No vacuum is needed unless measurements in the vacuum UV are desired. Thus, the formation of a surface layer due to environmental interactions can be studied in situ. The measurements are fast: a complete differential reflectogram, that is, an automatic scan from the UV through the visible into the IR region, is accomplished in about 3 min.
Electron Microscopy and Scanning Microanalysis
Authors: Oleshko Vladimir , Gijbels Renaat , Amelinckx Severin
Published: September 2006

In analytical electron microscopy (AEM), several imaging, diffraction and analytical modes are integrated in a design to provide analytical synergism having obvious advantages over any single instrument. The subject of AEM is to determine the morphology, crystallinity, defect structure, phase and elemental compositions and electronic properties of a material using the focused electron beam and signals generated in the course of its interaction with the specimen. The article considers history and stages of development of AEM, theoretical aspects of electron beam–solid interactions, instrumentation and methodology of particular techniques and image analysis, sample preparation and some typical applications. Various electron–specimen interactions generate a great deal of structural and analytical information in the form of emitted electrons and/or photons and internally produced signals, such as elastically and inelastically scattered electrons, Auger electrons (AE), X‐rays and cathodoluminescence (CL), which can be analyzed in different operating modes. Imaging of transmitted solid materials is essentially due to elastic scattering (diffraction) of electrons by the periodic arrangement of atoms in crystals (diffraction contrast) and/or interference of several diffracted and transmitted beams (phase contrast). High‐resolution imaging in the scanning transmission mode is also possible by using incoherently scattered electrons (Z‐contrast). Inelastic interactions are forming the basis for all chemical analytical techniques (energy‐dispersive (X‐ray) spectroscopy (EDS) and wavelength‐dispersive (X‐ray) spectroscopy (WDS), electron energy‐loss spectroscopy (EELS)/energy‐filtering transmission electron microscopy (EFTEM), AE and CL spectroscopy). Basic data characterizing state‐of‐the‐art modern AEM and current trends in its development are presented.
Scanning Probe Microscopy, Industrial Applications of
Authors: Born Axel
Published: September 2006

Scanning probe microscopy (SPM) has developed to become an integral part of the hierarchy of analytical tools in industrial surroundings, owing to its excellent spatial resolution and its ability to work under ambient conditions. The purpose of this article is to give an insight into the potential of SPM techniques in industrial applications today. Owing to the wide variety of possible applications, this article can present only a small selection of uses.

The given examples highlight typical aspects of the current analytical work of different industrial laboratories. First, an introduction to the specific industry and its analytical obstacles is given. Second, a solution using a SPM method is demonstrated and the particular SPM method is explained in detail. Finally, an actual measurement is given for each example.

To summarize, with the necessary precautions concerning stable conditions during the measurement, SPMs are a useful tool for industrial applications which fulfill the demands of industry today. SPMs are commercially available, rapid, quantitative and reproducible. Furthermore, they are available with a user‐friendly interface. The increasing number of companies that are using SPMs in the laboratory and manufacturing every day provides evidence of the rising popularity of SPM.
Ion Scattering Spectroscopy in Analysis of Surfaces
Authors: Langley Robert A.
Published: September 2006

Ion scattering spectroscopy (ISS) is used to analyze materials for their atomic constituents for depths from a monolayer to many microns. The probing depth and depth resolution are mainly determined by the energy and mass of the projectile. The projectile energy ranges from several thousand to many million electron‐volts. For ISS there are many options for analysis, e.g. scattered incident projectiles, knock‐on target atoms, reactants from nuclear reactions between the projectile and target atom, and X‐rays from excitation of target atoms by the projectiles. There are also numerous experimental techniques for studying various particular material characteristics, e.g. crystal structure, crystal damage, lattice deformation, and impurity content and location. Each of these areas is addressed, as well as the equipment needed for their implementation. Review articles and books on specific relevant subjects are noted, as well as data analysis techniques and computer analysis and simulation programs.
Photoluminescence in Analysis of Surfaces and Interfaces
Authors: Gfroerer Timothy H.
Published: September 2006

Photoluminescence (PL) is the spontaneous emission of light from a material under optical excitation. The excitation energy and intensity are chosen to probe different regions and excitation concentrations in the sample. PL investigations can be used to characterize a variety of material parameters. PL spectroscopy provides electrical (as opposed to mechanical) characterization, and it is a selective and extremely sensitive probe of discrete electronic states. Features of the emission spectrum can be used to identify surface, interface, and impurity levels and to gauge alloy disorder and interface roughness. The intensity of the PL signal provides information on the quality of surfaces and interfaces. Under pulsed excitation, the transient PLintensity yields the lifetime of nonequilibrium interface and bulk states. Variation of the PL intensity under an applied bias can be used to map the electric field at the surface of a sample. In addition, thermally activated processes cause changes in PL intensity with temperature.

PL analysis is nondestructive. Indeed, the technique requires very little sample manipulation or environmental control. Because the sample is excited optically, electrical contacts and junctions are unnecessary and high‐resistivity materials pose no practical difficulty. In addition, time‐resolved PL can be very fast, making it useful for characterizing the most rapid processes in a material. The fundamental limitation of PL analysis is its reliance on radiative events. Materials with poor radiative efficiency, such as low‐quality indirect bandgap semiconductors, are difficult to study via ordinary PL. Similarly, identification of impurity and defect states depends on their optical activity. Although PL is a very sensitive probe of radiative levels, one must rely on secondary evidence to study states that couple weakly with light.
X‐Ray Photoelectron Spectroscopy in Analysis of Surfaces
Authors: Oswald Steffen
Published: September 2006

X‐ray photoelectron spectroscopy (XPS) is an analytical technique that uses photoelectrons excited by X‐ray radiation (usually Mg Kα or Al Kα) for the characterization of surfaces to a depth of 2–5 nm. Elemental identification and information on chemical bonding are derived from the measured electron energy and energy shifts, respectively. The use of ultrahigh vacuum (UHV) during analysis requires special sample handling. Depth profiling is possible using ion sputtering.

In contrast to the most popular surface analytical technique, Auger electron spectroscopy (AES), nonconducting material can be investigated, little material damage occurs, and the chemical shifts are easier to interpret. However, the lateral resolution of AES (typically 50 nm) is much greater than for XPS (50 µm for standard equipment, down to lower than 3 µm for dedicated instruments). The detection limit (of about 0.1 atom %) is not as low as for mass spectroscopic techniques, but the quantification from XPS peak area measurements is much better, even disclaiming standard sample measurements.

This article briefly discusses the principles of the technique, sample requirements, and the typical measuring strategy. Possible information sources (elements, chemical bonding, depth and lateral distributions) are described and their quantification principles are summarized. The main part deals with typical applications relating to several material classes (metals, semiconductors, insulators, polymers) to give a feeling for the effectiveness of the method over a wide range of research and technological problems. A comparison with similar techniques is given as a summary.

Technological developments in electronics, nanotechnology, polymers, biotechnology and medicine are all concerned with surface‐related phenomena, suggesting sustained interest in XPS in the foreseeable future.
Background Correction Methods in Atomic Absorption Spectroscopy
Authors: de Loos‐Vollebregt Margaretha T.C.
Published: September 2006

Atomic absorption spectroscopy (AAS) is based on the absorption of element‐specific primary source radiation by analyte atoms. If part of the radiation isabsorbed by molecules or lost due to scattering, a higher gross absorbance is measured. The difference between the net absorption of the analyte atoms and the measured gross absorbance is called background absorbance. Background absorption and scattering effects have much more serious effects on the results produced in electrothermal atomization atomic absorption spectroscopy (ETAAS) than flame atomic absorption spectroscopy (FAAS).

The amount of incident light deflected or absorbed by nonatomic species must be measured to obtain the correct, net absorbance of the analyte atoms only. Perfect background correction can be obtained only when the background absorbance measurement corresponds exactly in space, time and wavelength with the atomic absorbance measurement. Since exact coincidence of all three parameters is obviously impossible, it is customary to give priority to the equality in space and to make the difference in time and/or wavelength as small as possible. Although molecular absorption and radiation scattering are both broad‐band phenomena, there is no spectral range where constant background attenuation can be guaranteed.

In all background correction systems two measurements are made. The total or gross absorbance is measured at the wavelength of the resonance line emitted by the hollow cathode lamp (HCL). The background attenuation is then subtracted from the measured analyte absorbance to obtain the analyte absorbance. There are several ways in which the nonatomic absorption at the resonance wavelength can be estimated, including two‐line background correction, continuum‐source or deuterium lamp background correction, Zeeman background correction, pulsed lamp or Smith–Hieftje background correction and wavelength‐modulation correction methods. The principle of each method, the instrumentation and applications are discussed. Continuum‐source background correction is widely used in FAAS and ETAAS, whereas Zeeman background correction and pulsed lamp background correction are often preferred in ETAAS.
Flame and Vapor Generation Atomic Absorption Spectrometry
Authors: Amos M.D.
Published: September 2006

Atomic absorption spectrometry (AAS) is a means of specific analysis for most of the metallic and metalloid elements. It achieves its specificity from the highly selective absorption, by free atoms of the analyte, of atomic emission of the same element at characteristic wavelengths. In its simplest form of application the free atoms of the analyte are created by aspiration of a solution of the sample to be analysed into a suitable flame, flame atomic absorption spectrometry (FAAS). The other principal means employed for the production of atoms (atomization) are graphite furnace atomization (GFAAS) and vapor generation atomization (VGAAS). Sample volumes of a few milliliters are normally needed for FAAS and VGAAS, but smaller volumes are needed for GFAAS. For most of the approximately 65 elements amenable to measurement by AAS, detection limits are from parts per billion to parts per million by flame methods and from parts per trillion to parts per billion levels by GFAAS and VGAAS. FAAS is inherently simple and rapid to use, whereas GFAAS and VGAAS are less rapid. The instrumentation used for AAS is relatively inexpensive Since all of these methods generally require the sample to be in solution form, the need for dissolution may be seen as a limitation in some cases. In the most common instrumentation employed, elements are only measured one at a time. It follows that for the determination of many elements in a large group ofsamples the method must be seen to be slow by comparison with multielement techniques such as inductively coupled plasma mass spectrometry (ICPMS) and inductively coupled plasma atomic emission spectrometry (ICPAES). However, the equipment costs involved for these techniques are generally higher and they are more complex to employ.
Glow Discharge Optical Spectroscopy and Mass Spectrometry
Authors: Steiner Robert E. , Barshick Christopher M.
Published: September 2006

Glow discharge (GD) sources provide analytically useful gas‐phase species from solid samples. These sources can be interfaced with a variety of spectroscopic and spectrometric instruments for both quantitative and qualitative analysis. Optical (atomic absorption spectroscopy, AAS; atomic emission spectroscopy, AES; atomic fluorescence spectroscopy, AFS; and optogalvanic spectroscopy) and mass spectrometric (magnetic sector, quadrupole mass analyzer, QMA; quadrupole ion trap, QIT; Fourier transform ion cyclotron resonance, FTICR; and time‐of‐flight, TOF) instrumentation are well suited for coupling to the GD.

The GD is a relatively simple device. A potential gradient (500–1500 V) is applied between an anode and cathode. In most cases the sample is also the cathode. A noble gas (e.g. Ar, Ne, Xe) is introduced into the discharge region prior to power initiation. When a potential is applied, electrons are accelerated toward the anode. As these electrons accelerate they collide with gas atoms. A fraction of these collisions are of sufficient energy to remove an electron from a support gas atom, forming an ion. These ions are, in turn, accelerated toward the cathode. These ions impinge on the surface of the cathode, sputtering sample atoms from the surface. Sputtered atoms that do not redeposit on the surface diffuse into the excitation/ionization regions of the plasma where they can undergo excitation via a number of collisional processes.

GD sources offer a number of distinct advantages that make them well suited for specific types of analyses. These sources afford direct analysis of solid samples, thus minimizing the sample preparation required for analysis. The nature of the plasma also provides mutually exclusive atomization and excitation processes that help to minimize the matrix effects that plague so many other elemental techniques. Unfortunately, the GD source functions optimally in a dry environment, making analysis of solutions difficult. These sources also suffer from difficulties associated with analyzing nonconducting samples.

In this article, the principles of operation of the GD plasma will first be reviewed, with an emphasis on how those principles relate to optical spectroscopy and mass spectrometry. Basic applications of the GD techniques will next be considered. These include bulk analysis, surface analysis, and the analysis of solution samples. The requirements necessary to obtain optical information will be addressed following the analytical applications. This section will focus on the instrumentation needed to make optical measurements using the GD as an atomization/excitation source. Finally, mass spectrometric instrumentation and interfaces will be addressed as they pertain to the use of a GD plasma as an ion source.
Laser Ablation in Atomic Spectroscopy
Authors: Russo Richard E. , Mao Xianglei , Borisov Oleg V. , Liu Haichen
Published: September 2006

Laser ablation (LA) is a unique technique to transform a solid sample into vapor‐phase constituents, which then can be chemically analyzed by atomic spectroscopy. Ablation brings many exciting capabilities to the field of chemical analysis, primarily because of the laser‐beam properties. The ability to analyze directly any solid samplewithout sample preparation and minimal sample‐quantity requirements are just some of the unique capabilities. This article discusses current issues related to using LA in atomic spectroscopy. A general introduction to LA sampling is presented along with a comparison with other solid sampling techniques. The critical issues for all analytical techniques are calibration, accuracy, and sensitivity. Techniques that have been demonstrated to address these analytical characteristics and define these parameters for LA are investigated in detail. Finally, many unique applications are described, ranging from dating geological materials to providing crime‐scene evidence. Most of these applications could not be performed without the use of a laser beam. The inductively coupled plasma (ICP) will be emphasized in this article because it is currently the most prevalent excitation and ionization source for chemical analysis using LA.