Particle synthesis: mechanisms

Fine Particles Synthesis, Characterization, and Mechanisms of Gro A4h, edited by Tadao Sugimoto... 

Fig. 7.5 Plausible mechanism of nano CaC03 particle synthesis during sonocrystallization in presence of surfactants [43]...

Matijevic, E. Partsch, R.E. (2000) Synthesis of monodispersed colloids by chemical reactions. In Sugimoto.T. (ed.) Fine Particles Synthesis, Characterization and Mechanism of Growth. Marcel Dekker, New York Matijevic, E. Sapieszko, R.S. (2000) Forced hydrolysis in homogeneous solutions. In Sugi-moto, T. (ed.) Fine Particles. Basel, Marcel Dekker, 2-34... 

This chapter focuses on silica synthesis via the microemulsion-mediated alkoxide sol-gel process. The discussion begins with a brief introduction to the general principles underlying microemulsion-mediated silica synthesis. This is followed by a consideration of the main microemulsion characteristics believed to control particle formation. Included here is the influence of reactants and reaction products on the stability of the single-phase water-in-oil microemulsion region. This is an important issue since microemulsion-mediated synthesis relies on the availability of surfactant/ oil/water formulations that give stable microemulsions. Next is presented a survey of the available experimental results, with emphasis on synthesis protocols and particle characteristics. The kinetics of alkoxide hydrolysis in the microemulsion environment is then examined and its relationship to silica-particle formation mechanisms is discussed. Finally, some brief comments are offered concerning future directions of the microemulsion-based alkoxide sol-gel process for silica. 

Fine particles synthesis, characterization, and mechanisms of growth / edited by Tadao Sugi-moto. 

Environmental organic matter is a composite of humic and nonhumic substances, which is formed through operation and interactions of various biotic and abiotic processes. Humic substances are formed through both selected preservation (residue) and catalytic synthesis mechanisms. Both enzymatic and mineral catalyses contribute to the formation of humic substances in the environment. The relative importance of these catalytic reactions would depend on vegetation, microbial population and activity, enzymatic activity, mineralogical composition and surface chemistry of environmental particles, management practices, and environmental conditions. Selective preservation pathways would play a more important role in humification processes in poorly drained soils and lake sediments, compared with more aerated environmental conditions. 

The macroscopic properties of liquid suspensions of fumed powders of silica, alumina etc. are not only affected by the size and structure of primary particles and aggregates, which are determined by the particle synthesis, but as well by the size and structure of agglomerates or mesoscopic clusters, which are determined by the particle-particle interactions, hence by a variety of product- and process-specific factors like the suspending medium, solutes, the solid concentration, or the employed mechanical stress. However, it is still unclear how these secondary and tertiary particle structures can be adequately characterized, and we are a long way from calculating product properties from them [1,2]. 

Matijevic, E. and Sapiesko, R. S. (2000) Metal oxides Forced hydi olysis in homogeneous solutions. In T. Sugimoto (ed.). Fine particles Synthesis, characterization and mechanism of growth. Marcel Dekker, New York, in press. 

Fievet, F., Polyol Process in T. Sugimoto, Fine Particles Synthesis, Characterization, and Mechanisms of Growth, Marcel Dekker, NY, pp. 460-496, 2000... 

For industrial applications, the particle size, morphology, and texture of the mesoporous material are important, which include several critical points such as mechanical stability and macroscopic shapes with well defined properties. Morphology control is one of the most interesting issues in the research field of mesoporous materials. It plays a very important role in understanding the basic synthesis mechanism. 

Kulbaba. K. Cheng. A. Bartole, A. Greenberg, S. Resendes. R. Coombs, N. Safa-Sefat. A. Greedan. J.E. Stover. H.D.H.iOzin, G.A. Manners, . Polyferrocenylsil-ane microspheres Synthesis, mechanism of formation, size and charge tunability, electrostatic self-assembly, and pyrolysis to spherical magnetic ceramic particles. J. Am. Chem. Soc. 2002. 124. 12522- 12534. 

Few results have been published in this rich area, but as the advantages and properties of these systems become known we expect to see more work in this area. A fundamental study of reaction mechanisms in a near-critical microemulsion was carried out by Zhang et al. [43]. Further, microemulsions in near-critical and supercritical fluids have been used in particle synthesis, hydrogenation, and polymerization reactions [41,67,68]. These diverse areas are discussed in this section. 

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