Particle formation, technological potential

With a chapter on particle-particle interaction (coagulation) the characteristics of particles and colloids as chemical reactants are discussed. Since charge, and in turn the surface potential of the colloids is important in coagulation, it is illustrated how in simple cases the modelling of surface complex formation permits the calculation of surface charge and potential. The role of particle-particle interaction in natural water and soil systems and in water technology (coagulation, filtration, flotation) is exemplified. 

Despite the advantages of CEC over CE and HPLC, particle-packed columns are plagued with problems such as the difficulty in the preparation of frits to retain the stationary phase and bubble formation that results in current leakage and EOF breakdown. These problems set the pace for the development of column technology to overcome the problems associated with particle-packed columns and to improve on the speed of separation of analytes in mixtures. The fabrication of a continuous porous rod (monoliths), not requiring any frits and ensuring a constant and uniform current flow to give a stable EOF has so far proved a potential development for microseparations. ... 

In the last years supercritical fluid (SCF) technology has occupied a significant place in the high pressure chemical engineering. Due to their specific properties as liquid-like densities, gas-like viscosities and diffusivities intermediate between gas and liquid values, SCF have large potential in extraction and separation processes, polymer science and technology and in elaboration of new materials [1-4], In these last cases, to control the size of particles, we have to deal with the kinetics of their formation. ... 

A method to obtain nano-particles at air/water interfaces has been described in [287]. Spreading of surfactant-coated metallic, semi-conducting, magnetic and ferroelectric nanoparticles on water surfaces results in the formation of monoparticulate thick films which then can be transferred, layer by layer, to solid substrates. These films can find potential applications in advanced electronic and electro-optical devices. Here and further, we give only typical examples of using surfactants in novel technologies. A more detailed description can be found in a new edition of Surfactants Science Series [288]. 

Figure Metal particle catalyzed and laser assisted chemical vapor deposition. Left Chemical vapor deposition causes the formation of a film or coating on a hot surface. Center and right Metal catalyzed and laser assisted chemical vapor deposition causes the formation of a potentially continuous fiber with a diameter corresponding to the hot metal catalyst particle or laser focus respectively. Redrawn from F. T. Wallenberger, P. C. Nordine and M. Boman, Inorganic fibers and microstructures directly from the vapor phase, Composites Science Technology, 5,193-222 (1994).

Following a similar route, Sondi et al. also described the formation of a protective poly(tert-butyl acrylate) layer on the surface of MPS-functionalized silica nanoparticles [155]. The amount of bound polymer was found to depend on the MPS-grafting density, which in turn was a function of the initial MPS concentration. The silica particles, the surface of which was efficiently recovered by both grafted and un-grafted polymers, showed an improved resistance to chemical etching. These studies highlighted the potential interest of encapsulated mineral oxide particles in photo-resistant technologies. 

---