Synthetic submicron particles

Particulate emissions from the synthetic fuels were very low, on the order of 0.01 lb per million BTU, and approximately one order of magnitude less than particulate emissions from No. 6 fuel oil. Data on particulate morphology and submicron particle size distributions Indicate a unlmodal size distribution for the No. 6 fuel oil and the SRC-II fuels while Indicating a blmodal size distribution for the H-Coals. Burners out of service and low excess air (LEA) operation did not significantly contribute added particulate emissions although 1t did tend to shift the unlmodal distributions toward a larger number of smaller particles. 

In case of starch blends with synthetic polymers the presence of starch in form of submicron particles dispersed into the matrix is a clear demonstration that a thermoplastic transformation occurred on starch itself... 

Figure 20.3 Scanning electron micrograph of synthetic hydrotalcite submicron particles [20].

Numerous colloidal systems can be identified in nature. Many synthetic materials which are produced and processed are also colloidal systems. Such systems are always multiphasic and are mostly comprised of submicron particles or nanometer particles. The macroscopic properties of colloidal systems are governed by the microscopic interactions of its dispersed constituents with each other and with the surrounding dispersing medium. The properties of such particle systems are dominated by interfacial effects rather than volume effects because of their huge internal surface. 

In this chapter we describe various methods for preparing molecularly imprinted polymers (MIP) in a colloidal state. The resulting materials consist of submicron scale particles dispersed in a liquid acting as fully functional synthetic affinity receptors. The synthesis, characterization, and performance of colloidal molecularly imprinted polymers are described and applications with this new class of affinity receptors is discussed. 

Synthetic Fe oxides are usually in the micron or submicron size range. Ultrafine particles with dimensions in the nanometer range frequently require more specialized techniques than do the larger crystals. The two basic requirements for a monodisperse system must be met and in addition, coagulation and/or contact recrystallization of the primary particles must be prevented. 

Ionic microgel particles play an important part in studies of the phase transition, as we will learn in Sec. V. In cases of NIPA-based polymerization systems, submicron-sized polyelectrolyte gel particles can easily be prepared using the usual synthetic technique of aqueous redox polymerization. Different polymerization media were then employed surfactant-containing wa-... 

Synthetic hydrotalcites employed in plastics applications are finely divided, free-flotving, odorless, amorphous powders. For polyolefin applications, hydrotalcites with an average particle size of 0.5 (tm and a specific surface area ofless than 20 m /g (BETmethod) are recommended. Their density varies around 2.1 g/cm depending on the composition. Sodium, zinc, and calcium stearate-coated hydrotalcites are available, which show enhanced compatibility with polyolefins [13]. Figure 20.3 is a scanning electron micrograph of a typical submicron-size synthetic hydrotalcite [20]. 

Nanoparticles may be defined as submicronic (<1 /Ltm) colloidal systems generally made of synthetic or natural polymers. According to the morphological structure, nanospheres or nanocapsules can be obtained. Nanospheres are matrix systems in which the drug is dispersed throughout the particle or adsorbed onto its surface nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a unique polymeric shell (Couvreur et al, 1995). 

SEM has been a primary tool for characterizing the fundamental physical properties of oxide materials for some time. For example, SEM is particularly useful for determining the particle shape and approximate size distribution of various silica materials used as supports in chemically bonded stationary phases for chromatography [8]. The visual images provide resolution at the micron to in some cases the submicron level so that surface morphology can be determined. This information is especially useful when evaluating a new synthetic approach to the formation of oxide materials. For example, a recently developed method... 

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