Characterisation methods

It is no exaggeration to claim that it was the extensive worldwide body of research on semiconductors from the late 1930s onwards that converted physicists to the recognition that scrupulous control of purity, stoichiometry and crystal perfection, together with characterisation methods that could check on these features, are a precondition of understanding the nature of semiconductors and thus also a precondition of exploiting them successfully - indeed, not only semiconductors but, by extension, many kinds of materials. 

Surface characterisation methods, both elemental (e.g. XPS, AES) and molecular (e.g. ToF-SIMS), are gaining in importance, in view of the active development of surface-modification technology to render fillers of all types more acceptable to the matrix and improve... 

The main advantages of CPAA as a surface characterisation method are that it requires no sample preparation, its high accuracy and its low detection limits. It is an independent method, because no standard samples calibrated by other methods are needed, so that its value may lie in its ability to calibrate standard samples for other, more routine analytical methods. 

Stretching a polymer in two perpendicular directions, either successively or by blowing a bubble of molten material, leads to its biaxial orientation, which strongly improves mechanical properties in the stretching directions and/or gas permeability (e.g., biaxial orientation of polypropylene leads to BOPP (for biaxially oriented polypropylene) or biaxial orientation of poly(ethylene terephthalate) gives CC>2-impermeable bottles for carbonated beverages.) (Characterisation methods for determining molecular orientation are considered in Chapter 8.)... 

In random degradation molecular mass decreases early, while in chain degradation the molecular mass of the polymer remains almost constant. Characterisation methods for molecular mass are thus very sensitive methods to follow random degradation. In contrast, as monomer is produced in chain depolymerisation, weight loss measurement techniques are the best methods to follow this kind of degradation. (Chapters 10-12, in Section IV, of this book focus on the methods used in the molecular characterisation and analysis of polymer degradation and polymer degradation mechanisms.)... 

Another polymer symposia was organised by IUPAC in 1947 in Liege. At this conference, the discussion included synthesis and technology of polymers like polyethylene, nylon, polyester. New characterisation methods such as x-ray scattering, x-rays, electron microscope, osmometry, nmr, IR, Raman spectroscopy, etc. were now available for characterisation of polymers. These methods become essential because of increasing complexity of new polymers. 

The most versatile surface characterisation methods are based on gas or vapour sorption and these techniques can provide physico-chemical information such as enthalpies, surface energies and diffusion constants but also surface area and pore size distributions. 

Lately one has been able to encounter experimental studies more frequently denoted Chemical Force Microscopy , CMF. This includes various attempts to observe tip-surface interactions which are specific to the chemical constitution of the surface. Mostly, CFM involves modification of the tip by a surface layer with molecules which contain particular functional groups, i.e. hydrophilic or hydro-phobic moieties, hydrogen bonding groups, ionic substituents and molecular units which can undergo electron-donor-acceptor interactions. However, sometimes the term Chemical Force Microscopy is just used for any method which can provide a material specific contrast. Depending on the specificity, CFM provides valuable information on the nanoscale composition complementary to other surface characterisation methods which are sensitive to the chemical con-... 

The application of analytical methods to speciation measurements in complicated systems has remained rather limited, despite the considerable technological progress during the past 25 years. The characterisation methods (e.g. spectroscopy, nuclear magnetic resonance) are often limited to the study of isolated compounds at relatively high concentrations. They, therefore, necessitate the prior employment of sophisticated separation and pre-concentration methods which introduce severe risks of perturbation. The trace analysis methods are often insensitive to the chemical form of the elements measured (e.g. atomic absorption, neutron activation). Those which possess sufficient element specificity (e.g. electron spin resonance, fluorescence, voltammetry) still require significant development before their full potential can be realised. 

Name and characterise methods for obtaining a-olefin copolymers with polar vinyl monomers in the presence of coordination catalysts. 

An alternative two-part classification has been proposed by Pearlman et al. [90], who characterise methods as either cell-based or distance-based, these classes corresponding to partition-based methods and to all the other types of method, respectively. As Pearlman et al. note, distance-based methods can be used with any type of structural representation but are most effective when the need is to identify subsets (of whatever sort) cell-based... 

In this paper we present a new characterisation method for porous carbonaceous materials. It is based on a theoretical treatment of adsorption isotherms measured in wide temperature (303 to 383 K) and pressure ranges (0 to 10000 kPa) and for different adsorbates (N2, CH4, Ar, C3H8 and n-C4Hio). The theoretical treatment relies on the Integral Adsorption Equation concept. We developed a local adsorption isotherm model based on the extension of the Redlich-Kwong equation of state to surface phenomena and we improved it to take into account the multilayer formation. The pore size distribution fimction is assumed to be a bi-modal gaussian. By a minimisation procedure, it is possible to determine the bi-modal pore size distribution function witch can be used for purely characterisation purposes or to predict adsorption isotherms. 

FIGURE 10.11 lUPAC classification of physisorption isotherms. (Following Schoofs, T., Surface area analysis of finely divided and porous solids by gas adsorption measurements, in Particle and Surface Characterisation Methods, R.H. Muller and W. Mehnert, Eds., Medpharm GmbH Scientific, Stuttgart, 1997.)... 

High 95- 99 % X-ray crystallography and most physico-chemical characterisation methods... 

The theory of transport in multicomponent gas mixtures in micropore systems should be further developed and more data on competitive adsorption of multicomponent gas mixtures on the membrane material should become available together with adequate characterisation methods of porosity and pore size of supported systems. 

A variety of other static characterisation methods have been described in this chapter which are not listed in Table 4.2. Many of these are new and in a state of rapid evolution, as for example those involving NMR and radiation scattering. Whilst appropriate for research investigations they do not seem yet to be appropriate as a means of general characterisation. However with the rapid progress under way in these areas, some of these techniques we feel may in the future be ideally suited to membrane characterisation. 

Geil P H (1996) Modem Textile Characterisation Methods, Raheel, M (ed.), Marcel Dekker, New York, 23. 

Characterisation methods. Vanadium and phosphorus contents were determined by an ICP analysis (inductive coupled plasma atomic absorption) after dissolution in 0.1 M nitric acid, carbon by measuring the amount of CO2 produced by total oxidation using Coulomat 702 Stroelheim. The BET specific surface area was obtained using ASPAP 2000 (Micromeritics) by nitrogen adsorption at - 196 °C after degassing samples at 125 °C. 

R. Wiithrich, U. Spaelter, Y. Wu, H. Bleuler A systematic characterisation method for gravity feed micro-hole drilling in glass with Spark Assisted Chemical Engraving (SACE). Journal of Micromechanics and Microengineering 16 (2006), p. 1891. 

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