1.1 Introduction

Nanoparticles play a vital role in high performance materials in high technology industries. The studies of nanoparticles started in the early 1980's and have now become one of the hottest worldwide research fields (Pui and Chen, 1997).

There are four main processing approaches for the preparation of nanoparticles by chemical method (Riman, 1993): (1) chemistry in liquid phase including direct strike (Murata, et al., 1976), nonsolvent addition (Mulder, 1970), solvent removal (Cheng, et al., 1986), gel drying (sol-gel) (Perthuis, And Colomban, 1984) and precipitation from homogeneous solution (Gordon, et al., 1959); (2) chemistry between heterogeneous phase including hydrothermal synthesis (Adair, et al., 1987), molten salt synthesis (Arendt, et al., 1979), pyrolysis (Wada, et al., 1987) and spark erosion (Berkowitz, et al., 1987); (3) chemistry in a droplet including emulsions (Woodhead, et al., 1980), micelles (Gobe, et al., 1983) or microemulsions (Kandori, et al., 1988) and aerosols (Balboa, et al., 1987); (4) chemistry in the vapor phase including heating method (Mazdiyasni, et al., 1965), vapor precursors (Iwama, et al., 1982), liquid precursors (Kagawa, et al., 1983) and solid precursors (Watanabe, et al., 1986). The most attractive methods are those which synthesize in the liquid medium, including methods of precipitation, reduction, dehydration, solvent evaporation, reversed micelle technology and microemulsion polymerization, etc. In this chapter, we will focus on the nanoparticles made from both W/O microemulsion (reversed micelles) and O/W microemulsion procedures.

Hence it is necessary to introduce...