Optical microscopy, various techniques

As Fig. 2.6 reveals, optical microscopy with polarized light makes it possible to distinguish various intermediate products formed from a precursor of graphitic carbon at different stages of pyrolysis. The observed morphology is the so-called optical texture, which enables carbon sohds to be classified according to their degree of anisotropy. Besides optical microscopy, other techniques... 

There are various reasons to study the composition of ancients cements. The actual composition of a cement, for example, provides information on its nature, the technology used for making it, and the provenance of its components (Middendorf et al. 2005). It may also elicit differences between the nature of an original cement used for building and that used for later repairs (Streicher 1991 Jedrzejewska 1990). Most analytical work concerning ancient cement in the recent past has been based mainly on the use of optical microscopy and classical analysis techniques. Sometimes, such studies are complemented with information derived by instrumental techniques (Blauer-Bohm and Jagers 1997). 

Figure 10.1 Comparision of various techniques for examination of defects and voids in materials (OM-optical microscopy, TEM- transmission electron microscopy STM-Scanning tunneling microscopy, AFM-atomic force microscopy, Mech-mechanical techniques).

Optical microscopy. Interferometry, various electron microscopies, atomic force techniques (AFM, STM), surface diffraction, BET (+t-plot), poroslmetry. 

Among the various techniques, we shall only discuss STM, scanning force microscopy (SFM or AFM), and scanning near-field optical microscopy (SNOM or NSOM), as those can well be considered the most prominent members of the SPM family. Among the three, we shall further focus on SFM, as most of the work done on polymers has indeed made use of this method. However, a brief note on STM and SNOM seems appropriate. 

The aggregation behavior of selected dibiock copolymers with various compositions was investigated applying several techniques, such as polarized optical microscopy (POM), tensiometry measurements, fluorescence studies, deuterium NMR spectroscopy, SAXS measurements, and cryogenic TEM [4, 5]. In systematic studies we particularly focused on the effect of an increase in the dimethylsiloxane chain length on the aggregation behavior of the investigated surfactants. 

The optical microscope is a valuable tool in the laboratory and has numerous applications in most industries. Depending on the type of data that is required to solve a particular problem, optical microscopy can provide information on particle size, particle morphology, color, appearance, birefringence, etc. There are many accessories and techniques for optical microscopy that may be employed for the characterization of the physical properties of materials and the identification of unknowns, etc. Utilization of a hot-stage accessory on the microscope for the characterization of materials, including pharmaceutical solids (drug substances, excipients, formulations, etc.), can be extremely valuable. As with any instrument, there are many experimental conditions and techniques for the hot-stage microscope that may be used to collect different types of data. Often, various microscope objectives, optical filters, ramp rates, immersion media, sample preparation techniques, microchemical tests, fusion methods, etc., can be utilized. 

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