Scanning electron microscopy advantages

In 1994, we reported the dispersion polymerization of MM A in supercritical C02 [103]. This work represents the first successful dispersion polymerization of a lipophilic monomer in a supercritical fluid continuous phase. In these experiments, we took advantage of the amphiphilic nature of the homopolymer PFOA to effect the polymerization of MMA to high conversions (>90%) and high degrees of polymerization (> 3000) in supercritical C02. These polymerizations were conducted in C02 at 65 °C and 207 bar, and AIBN or a fluorinated derivative of AIBN were employed as the initiators. The results from the AIBN initiated polymerizations are shown in Table 3. The spherical polymer particles which resulted from these dispersion polymerizations were isolated by simply venting the C02 from the reaction mixture. Scanning electron microscopy showed that the product consisted of spheres in the pm size range with a narrow particle size distribution (see Fig. 7). In contrast, reactions which were performed in the absence of PFOA resulted in relatively low conversion and molar masses. Moreover, the polymer which resulted from these precipitation... 

Fig. 7 (a) Beads packing device working in a flow system, taking advantage of a leaky wall (reproduced from [27]) (with permission), (b) a scanning electron microscopy image of a flow through reactor composed of pillar made walls used to pack microspheres (reproduced from [28]) (with permission)... 

Texture controls the accessibility of active components of catalysts to the reagents. Textural analysis is thus one of the most frequent requests by manufacturers. The aim is to determine the dimensions, form and interconnection of the micrograins. Methods such as porosim-etry and picnometry, based on absorption, have the advantage of providing an overall view of the solid and can be used to quantify the texture. Scanning electronic microscopy, which is not only a more local but also a more visual method, as well as small angle X-ray scat-... 

This chapter outlines emulsion characterization techniques ranging from those commonly found infield environments to those in use in research laboratories. Techniques used in the determination of bulk emulsion properties, or simply the relative amount of oil, water, and solids present, are discussed, as well as those characterization methods that measure the size distribution of the dispersed phase, rheological behavior, and emulsion stability. A particular emphasis is placed on optical and scanning electron microscopy as methods of emulsion characterization. Most of the common and many of the less frequently used emulsion characterization techniques are outlined, along with their particular advantages and disadvantages. 

Whilst the use of enamel and dentine as test substrates is widespread, they are complex materials to work with due to the natural variability both within and between specimens. A number of authors have examined alternative materials, which have similar mechanical properties to enamel and dentine, to use as test substrates. Acrylic [19, 20] and synthetic hydroxyapatite [21] have been proposed as suitable materials for abrasion testing, where mechanical effects dominate. These materials have several advantages since they are available as relatively large, smooth samples and exhibit better intra- and inter-sample reproducibility than their natural counterparts. This may, therefore, give better discrimination between test products for formulation development. However, the use of natural enamel and dentine is preferred, particularly for studies that aim to understand interactions between toothpaste products and tooth hard tissues. Other methods for assessing toothpaste abrasivity to hard tissues include gravimetry [22], scanning electron microscopy [23] and laser reflection [24]. 

Electron Microscopy. Scanning electron microscopy and energy-dispersive X-ray microanalysis can be effectively used in combination to provide both structural and elemental information about individual mineral particles in coal and other materials (42,53-55). Transmission electron microscopy has the advantage of higher resolution (56,57) allowing more detailed characterization of mineral inclusions. 

Before specifically dealing with coherent x-ray imaging, its foundations, and its advantages, we note that alternate experimental solutions were used to tackle these problems. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) probe the surface morphology and the overall microstructure of metal electrodeposits. However, they do not work in real time they are used to analyze the final products after the end of the growth. 

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