Dispersion of ultrafine

I. Hussain, I. Gameson, P.A. Anderson, M. Slaski, P.P. Edwards, and A. Dyer, A Route to the Dispersion of Ultrafine Cobalt Particles on Zeolite Na-X through Salt Occlusion and Reduction, j. Chem. Soc., Dalton Trans., 1996, 775-781. 

Solid Phase Dispersion of Ultrafine Particles into a Polymer Through Thermal Relaxation... 

Magnetic fluids are stable dispersions of ultrafine magnetic particles or encapsulated magnetic particles in an organic or aqueous carrier medium. The stabihza-tion of these particles can be achieved by surfactants which hinder the particles from flocculation or sedimentation. In ideal cases, the particles also keep their stability under the exposition of magnetic fields. 

Inorganics can also be synthesized and used as templates. Thus, controlled siloxane networks were formed when dispersions of alkoxysilanes (such as (MeO)3SiMe) are mixed with the suitable template matrixes. Ultrafine particles of metal oxides can be used as starting materials for the formation of metal oxide films. For instance, a mixture of a double-chained ammonium amphiphile and an aqueous solution of aluminum oxide particles (diameter about 10 100 nm) gives a multilayered aluminum oxide film when calcinated at over 300°C. 

One important class of particulate composites is dispersion-hardened alloys. These composites consist of a hard particle constituent in a softer metal matrix. The particle constituent seldom exceeds 3% by volume, and the particles are very small, below micrometer sizes. The characteristics of the particles largely control the property of the alloy, and a spacing of 0.2-0.3 tim between particles usually helps optimize properties. As particle size increases, less material is required to achieve the desired interparticle spacing. Refractory oxide particles are often used, although intermetallics such as AlFes also find use. Dispersion-hardened composites are formed in several ways, including surface oxidation of ultrafine metal powders, resulting in trapped metal oxide particles within the metal matrix. Metals of commercial interest for dispersion-hardened alloys include aluminum, nickel, and tungsten. 

Morawska and co-workers have produced a number of review articles on this topic. For example, Holmes and Morawska [20] reviewed several simple and complex models covering a wide range of urban scales for the dispersion of particulate matter. Morawska et al. [21] focused on vehicle produced ultrafine particles and discussed limitations of measurement methods, sources, characteristics, transport and exposure of these particles in urban environments. Their further review focused on indoor and outdoor monitoring of airborne nanoparticles [3]. Morawska [22] discussed the importance of airborne ENPs from the health perspective. Regulations and policy measures related to the reduction of ambient particulate matter were discussed in their follow-up article [23], Their recent review article discussed the commuters exposure to ultrafine particles and associated health effects [24]. 

Separation of Ultrafine Pyrite from High Sulfur Coals by Selective Dispersion and Flocculation... 

The considerable increase of elastic modulus with low amoimt of ultrafine amorphous silica Si02 (< 0.1 pm) shows the nanoparticles to be well dispersed. It cannot be explained by classical models (Kemer, Nielsen) we have to take into account that a part of the polymer matrix is occluded in the aggregates. It can also be explained by adsorption of the polymer on the surface of the silica. Silica-PP adhesion is high, and so the molecular mobility is reduced this effect is all the more important as the surface area is high (> 150 m /g). This effect has been observed on elastomeric materials, where polymer adsorption on silica control the modulus [23]. 

Electrocatalyst support The main functions of the carbon support are to (a) disperse the ultrafine electrocatalyst particles, (b) bind strongly with the... 

It is commonly recognized that a comprehensive understanding of the properties of a new material is an essential prerequisite to finding its new applications. In this respect, the study of ultrafine diamond is incomplete and its properties remain to be fully elucidated. For example, the nature of the surface functional groups and the method of their modification the nature of the agglomeration of ultrafine crystallites and effective methods of de-agglomeration to prepare mono-dispersed suspension the crystalline and surface structures of the nano-scaled diamond, etc., are appropriate subjects of research An efficient method for the determination of particle size distributions and structures of nano-sized particles in suspension is very important, and is worth developing in the near future. 

A sol-gel process is an important method to synthesize many materials in a variety of shapes and forms such as particles, films, and bulks. This method is especially suited for the synthesis and preparation of ultrafine rare earths oxide particles at relatively low temperatures. A sol is a stable colloidal dispersion of small particles suspended in a liquid. The particles are amorphous or crystalline and particle aggregation is prevented by electrostatic repulsion. The particles in some sols interact to form a continuous network of connected particles called a gel, instead of aggregating to form larger particles (precipitates). 

Preparation of ultrafine monodisperse hybride particles, dispersible in low polar organic solvent, from monodisperse colloidal silica by two-step polymer modification was studied. Bindings of the secondary polymer to monodisperse poly(maleic anhydride-styrene)-modified colloidal silica particles (120 nm) have made the composites in low polar solvent dispersible. The dispersion of the particles in good solvent for the secondary polymer is due to the steric repulsion of solvated polymer chains. The dispersibility of the hybrid particles in poor solvent-rich solution was controlled by delicate balance between nonpolar-nonpolar interaction and electrostatic repusion among the particles. 

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