Optical microscopy information

Microscopic identification models ate similar to the CMB methods except that additional information is used to distinguish the source of the aerosol. Such chemical or morphological data include particle size and individual particle composition and are often obtained by electron or optical microscopy. 

The properties and performance of cemented carbide tools depend not only on the type and amount of carbide but also on carbide grain size and the amount of biader metal. Information on porosity, grain size and distribution of WC, soHd solution cubic carbides, and the metallic biader phase is obtained from metaHographicaHy poHshed samples. Optical microscopy and scanning and transmission electron microscopy are employed for microstmctural evaluation. Typical microstmctures of cemented carbides are shown ia Figure 3. 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

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). 

We use optical microscopy to examine samples at magnifications from about 5x up to approximately l,000x. Samples may be examined using either transmitted or reflected light, depending on the nature of the sample and the information that we are seeking. 

The first linkage between a microscope and an IR spectrophotometer was reported in 1949 [15]. Today, every manufacturer of IR spectrophotometers offers an optical/IR microscope sampling accessory. The use of optical and IR microscopy is a natural course of action for any solid state investigation. Optical microscopy provides significant information about a sample, such as its crystalline or amorphous nature, particle morphology, and size. Interfacing the microscope to an IR spectrophotometer ultimately provides unequivocal identification of one particular crystallite. Hence, we have the tremendous benefit of IR microscopy for the identification of particulate contamination in bulk or formulated drug products. 

Transmission electron microscopy (TEM) is a powerful and mature microstructural characterization technique. The principles and applications of TEM have been described in many books [16 20]. The image formation in TEM is similar to that in optical microscopy, but the resolution of TEM is far superior to that of an optical microscope due to the enormous differences in the wavelengths of the sources used in these two microscopes. Today, most TEMs can be routinely operated at a resolution better than 0.2 nm, which provides the desired microstructural information about ultrathin layers and their interfaces in OLEDs. Electron beams can be focused to nanometer size, so nanochemical analysis of materials can be performed [21]. These unique abilities to provide structural and chemical information down to atomic-nanometer dimensions make it an indispensable technique in OLED development. However, TEM specimens need to be very thin to make them transparent to electrons. This is one of the most formidable obstacles in using TEM in this field. Current versions of OLEDs are composed of hard glass substrates, soft organic materials, and metal layers. Conventional TEM sample preparation techniques are no longer suitable for these samples [22-24], Recently, these difficulties have been overcome by using the advanced dual beam (DB) microscopy technique, which will be discussed later. 

Transmission electron microscopy (TEM) resembles optical microscopy, except that electromagnetic instead of optical lenses are used to focus an electron beam on the sample. Two modes are available in TEM, a bright-freld mode where the intensity of the transmitted beam provides a two-dimensional image of the density or thickness of the sample, and a dark-field mode where the electron diffraction pattern is recorded. A combination of topographic and crystallographic information, including particle size distributions, can be obtained in this way [32],... 

Although the detailed information on the polymorphic phases has to be obtained with e.g., diffraction and scanning probe methods, our eyes are attracted by the beauty of optical microscope images often encountered with polymorphs under transformation. Figure 5.17 shows an optical microscopy image of a / -NPNN thin film (thickness 2 pm) on a glass substrate, exhibiting a transformation at... 

Polystyrene latex particles were coagulated by the addition of Ba(N03)2. The number of dispersed particles deposited onto a planar polystyrene surface was determined 15 min after the addition of salt by optical microscopy. The light microscope does not permit the aggregation of the deposited particles to be determined subsequent examination by the electron microscope gives this information. Clint et al. obtained the following results ... 

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