Page 22 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 1
nitrogen or organic compounds, this type of microplasma can be applied to fabricate metal oxides, nitrides, carbides or metal nanoparticles embeded in polymer coatings shells. The generated products can be collected by simply placing a substrate under the consumed wires.
A typical example which explicitly demonstrates such a plasma configuration and is shown in Figure 1.4, was proposed by Yoshiki Shimizu et al. to synthesize Au nanoparticles.80 In this system a consumable Au wire of 100 μm diameter was used as the metal source and inserted into a quartz capillary (O.D.= 1.2 mm, I.D.=800 μm). A flow of H2/Ar mixture was fed into the capillary at a 200 sccm flow rate. A UHF (450 MHz) generator was applied to sustain the microplasma jet. After the ignition of the plasma, the Au wire was heated and melted due to thermal conduction as well as inductive heating. Then Au nanoparticles resulting from atomization of the consumable wire were carried away by the gas flow and deposited on a glass epoxy plate 5 mm downstream.
80
Microplasma jet with consumable wire electrodes is a special category of microplasma systems. With such a configuration it is possible to produce a broad range of metal nanoparticles, alloys, oxides, nitrides and carbides. The product properties can be controlled and tuned “in-flight” by controlling processing parameters, such as the gas composition, plasma power, gas feeding rate and so on. However, the limitation of such system is to continuously produce the desired products, which is attributed to the metal wires consumption during the reactions. Fortunately, this problem can be circumvented using a mechanism to continuously feed the consumable wire.64 Another problem is due to the temperature gradient in the plasma and the non-uniform volatilization rate of the metal wire, the obtained nanostructures have poor uniformity.
Figure 1.4 Schematic diagram of the microplasma jet with a consumable Au wire electrode. Reprinted
with permission from [
], copyright 2006 Elsevier
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