Plasma Modeling: Plasma-Induced Effects on Nanoparticles
The arc discharge in high pressure inert gases between graphite electrodes is one of the standard methods of nanoparticle synthesis. The arc is a very powerful light emission source, which is close to a blackbody source. We recently proposed a theoretical model of heating the spherical carbon nanoparticles in the Rayleigh regime of the radiation absorption, depending on their size and the parameters of the radiating arc and the surrounding gas [Shneider, 2015]. This issue is very important for synthesis processes, but is also related to the application of laser diagnostics of nanoparticles in the vicinity of a stationary arc. We considered the conditions specific to the far periphery of the arc, where the degree of ionization is very small and the contribution of plasma effects to the heat balance is negligible. The following cooling processes were taken into account: radiative cooling; cooling in collisions with a cooler buffer gas atoms, and thermionic emission. The results demonstrated that the nanoparticle temperatures significantly exceed the local temperature of the buffer gas. The temperature of the particle is higher for particles closer to the arc. The particle temperature reaches steady-state equilibrium with radiation within 10 microseconds. Convective displacement of the particles is negligible on this time scale. The heating of nanoparticles by radiation can affect the synthesis process. The degree of heating of the particle is affected by the particles geometry, and this effect opens additional possibilities for new nonintrusive in situ optical diagnostics of nanoparticles (e.g by LII) and control of nanosynthesis process.