Page 82 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 4
Ar+
Ar*
Ar+
e
Ar*
e
e
Plasma Ar+ dissociation
Radicals nucleation
Ar+
Ar+
+ Vapors
e
Figure 4.8 Hypothesized mechanism for the synthesis of TiN nanoparticle
Table 4.3 gives a comparison of the processing parameters between microplasma method and non-plasma methods. As clearly indicated in the table, non-plasma methods are always batch processing, requiring at least two steps, with the total duration time much longer than microplasma methods. The whole processes last for several hours or even overnight in some cases. In addition, all reactions need several toxic chemicals as the starting materials, catalysts, stabilizers or reducing agents. As a consequence, byproducts and impurities are inevitable. Complex pre or post treatments like stirring, washing, drying or annealing are necessitated to obtain high quality and purity products. Furthermore, the average particle size and size distribution varies in a wide range. By contrast, in this study TiN nanoparticles are continuously synthesized in one step by microplasma method. The products are directly collected from the gas phase, without any post treatments. Moreover, only TiCl4 is used as the starting material, with N2 as the N source, allowing the environmentally friendly synthesis of TiN nanoparticles. The short residence time in microplasma process also limits particle agglomeration, resulting in more uniform and smaller sized nanoparticles.
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