System components dispersion

Even while Raman spectrometers today incorporate modem teclmology, the fiindamental components remain unchanged. Connnercially, one still has an excitation source, sample illuminating optics, a scattered light collection system, a dispersive element and a detechon system. Each is now briefly discussed. 

Conducting Polymer Blends, Composites, and Colloids. Incorporation of conducting polymers into multicomponent systems allows the preparation of materials that are electroactive and also possess specific properties contributed by the other components. Dispersion of a conducting polymer into an insulating matrix can be accompHshed as either a miscible or phase-separated blend, a heterogeneous composite, or a coUoidaHy dispersed latex. When the conductor is present in sufftcientiy high composition, electron transport is possible. 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

A.S. Kabalnov, A.V. Pertsov and E.D. Shchukin Ostwald Ripening in Two-Component Disperse Phase Systems Application to Emulsion Stability. Colloid Surfaces 24, 19 (1987). 

Some distillate fuel stabilizers possess dispersant-like properties. By acting as a dispersant, any sludge or deposit-like component which may form can be suspended in the fuel and maintained as a soluble compound. As a result, deposits do not accumulate onto fuel system components, but remain dispersed in the fuel. However, due to this dispersing action, the fuel may appear dark in color. 

Corrosion-inhibiting properties of fuel stabilizers can be a secondary effect of the dispersing action of a fuel stabilizer. By functioning as a dispersant, sludge and water are held in suspension and prevented from initiating metal surface corrosion. Also, some stabilizer dispersants can form a thin film on the metal surfaces of fuel system components. This film-forming property enables the stabilizer-dispersant to function in corrosion control. A typical oil-soluble dispersant compound is shown in FIGURE 6-3. 

Polar additives in oil formulation What type of interactions can you predict in the engine oil two-component system ZDDP + dispersant (a) in the hydrocarbon formulation, and (b) on the surface Consider the stronger the complexation, the greater adverse effect on wear. 

Fruits and vegetables in vivo are nothing more than living macromolecular systems or biocolloidal dispersions. Outside the living tissue, they are multi-component dispersions and suspensions. It is these physical forms, influenced by one or more critical variables, that have many applications. The kind and scope of the polysaccharide response to stimuli in vitro depend on the polysaccharide s chemistry, the intensive properties engineered into it as a result of extraction, purification, and modification, and its interaction with the solvent surroundings. 

In two-part epoxy adhesive systems, the filler can generally be incorporated into either the epoxy resin or the curing agent component. Prevailing factors will be the characteristics mentioned above (viscosity of each component, dispersion characteristics, etc.). However, the effect on the mix ratio and on the ease of mix-... 

Carbon black is far less resistant to the flow of electricity on its surface than the plastic resins in which the black is dispersed. Therefore, carbon black can be used to lower the resistivity of plastics, imparting antistatic, semiconductive, or conductive properties. End uses for conductive carbon blacks range from material handling bins and device carrier tapes in the electronics industry to fuel system components to semiconductive strand shielding for power cable. 

Multicomponent polymers systems such as polyblends, and block copolymers often exhibit phase separation in the solid state which results in one polymer component dispersed in a continuous phase of a second component. The morphological properties of these systems depend upon a number of factors such as the molar ratios of the components, the molecular weights, the thermal history of the system and, for solvent cast films, the solvent and drying conditions. 

In order to explain such a microhardness depression, AH = Heal — Hexp (Table 5.4), it is convenient to consider the behaviour of the harder component dispersed in the liquid component (with zero hardness). It seems reasonable here to assume that the total microhardness of such a system will also depend on the viscosity of the soft component in which the particles of the harder component are floating . The deviation of Hexp from Hcai may actually reflect the viscosity of the soft-segment phase which also contributes to the resistance of the total system against the applied load. The viscosity of the soft phase introduces two important effects. 

Aroma compounds frequently exist as trace components, dispersed in complex systems that complicate their isolation and identification. While many fields benefitted from the invention of gas chromatography, it has been especially valuable to those in flavor chemistry. Gas chromatography is not a mature science in many ways, it is still an art, and developments in the field continue. While these developments offer some exciting new opportunities, they can also be employed improperly with adverse effects on the analytical results. 

This set of experiments can be regarded as a basic toolbox for systematic studies on dispersed nanoparticles. It simultaneously yields data on the chemical identity and on rotational as well as lateral mobility. Hence, it allows for a clear assignment of all chemical constituents to the various system components such as particle matrix, capsule contents, or the continuous phase. Further, it gives access to data on the size and shape of the particles and the chemical exchange on the particle surface. 

The combination of direct excitation or cross-polarization NMR experiments with off-MAS sample spinning seems to be the most powerful approach for the study of rotational diffusion of all system constituents. It allows for a chemical identification of all organic system components and simultaneously yields data on their rotational diffusion. Hence, for detailed studies on particle tumbling in complex systems, it represents the preferred experimental condition for all particle dispersions which are stable enough to survive the inertial field during sample spinning for an adequate period of time. ... 

NMR spectroscopy represents a valuable and versatile tool for the characterization of dispersed nanoparticles. In contrast to alternative analytical techniques, it combines a distinctly non-invasive character with the ability to analyse for chemical composition as well as for local mobility of individual system components. Its main disadvantages - poor sensitivity and time consuming acquisition of experimental data - can be overcome by a suitable choice of the pulse sequence and the experimental conditions. The advantages of the NMR approach are especially promising for the study of nanoparticle dispersions used as drug carriers, where many important system characteristics such as release properties, surface exchange processes or decomposition pathways are readily available by relatively simple pulse experiments. 

Most methods deal with the formation of metal particles on a support that is preformed since this leads to simpler preparation processes. There is an important route, however, typically used for metal-SiCh and metal-AI2O3 catalysts, which involves (Table I) the coprecipitation in a precursor form (hydroxides, nitrates, carbonates, silicates, etc.) of both the support and the active phase from a solution 37a,b, 38, 41). The advantage is to produce an intimate mixing of metal precursor and support. The precipitate leads on calcination to a support with the active component dispersed throughout the bulk as well as at the surface. After reduction to the final catalyst, it is difficult to obtain metal crystallites of uniform size 42, 43) because of the presence of both the oxides (of the support and of the active metal) and other intermediate compounds [e.g., nickel alumi-nate or silicate for the Ni/Al203 42) and Ni/SiCh 43) systems, respectively] that have different reducibilities. 

The systems containing dispersed particles with anisotropic polarizability possess some unique optical properties. The axis of dipole induced by primary wave in such a particle does not coincide with the direction of electric vector in incident light wave. As a result, upon irradiation with polarized light, the dipole moments of chaotically distributed particles form different angles with respect to the initial direction of polarization. This leads to the appearance of perpendicularly polarized components in the scattered wave, i.e., partial depolarization of light occurs (Fig. V-26) [21]. 

Besides the gas handling, heating, and cleaning facilities, the two most important system components are the equipment for dispersion of the wet feed and the containment in which hot gas contacts the dispersed wet material and drying takes place. 

Nonhydrocarbon Solvents, Although an asphaltene fraction can be removed from petroleum by using a wide variety of hydrocarbon liquids (14), the use of nonhydrocarbon solvents as deasphalting media and their influence on asphaltene dispersibility and compatibility has also been investigated. Dispersibility of asphaltenes in petroleum is suggested to be conveniently related to the surface tension of the system components (8, 20, 21, 22, 23). Obviously, asphaltene dispersion and compatibility is complex and is dependent on several factors and varies markedly with the character of the added liquid. 

The behavior of binary blends with only one crystaUizable component has been studied by several authors, who have investigated different systems. The crystals of the crystaUizable matrix have grown in equilibrium with their own melt phase. The presence of separate domains of non-crystallizable component, dispersed in the molten matrix during the crystallization process, (owing to the kinetic and morphological effects), may cause a depression of the observed melting tem-... 

For a direct transponation. the shonest and thinnest conduits that are practical should be used in order to avoid unnecessary dispersion. The dispersion contribution of various transport conduits in FI-AAS systems have been studied in detail, and the importance of tube diameter, length and configuration have been stressed [5]. The dispersion contribution of this seemingly unimportant system component may often be overlooked. However, to obtain optimum performance, careful minimization of dispersion is required, especially when the columns are small, and the concentrate zones in the eluate well-focused. A shortest possible length, not exceeding 20 cm of 0.35 mm i.d tubing has been recommended for the transport conduits in AAS applications, and should be also applicable to other detection systems which do not require post column reactions. 

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