Fluid-dynamic characterization of a radio-frequency induction thermal plasma system for nanoparticle synthesis

Abstract

The fluid flow in a radio-frequency induction thermal plasma (RF-ITP) system for the synthesis of nanoparticles has been characterized using three-and two-dimensional modelling supported by enthalpy probe and calorimetric measurements in order to provide insights for the improvement of the process. The RF-ITP system is composed of a commercial inductively coupled plasma torch mounted on a reaction chamber that is equipped with viewports for diagnostics. The three-dimensional model predicted an almost axisymmetric temperature field in the reaction chamber in agreement with enthalpy probe measurements performed along two perpendicular scan axes, whereas recirculating flow patterns resulted in being strongly non-axisymmetric. Temperature profiles at two distances (60 mm and 100 mm) from the torch outlet have been calculated using two-dimensional modelling and compared with enthalpy probe measurements for different operating conditions with the aim of validating the predictive ability of the modelling tool. Calorimetric measurements have been performed in order to estimate the power coupled to the torch, which is usually an arbitrary input parameter for the models. Poor agreement was obtained between energy balances from modelling and from calorimetric measurements and, starting from this, a discussion on the uncertainties in the calculation of the radiative losses has been proposed. Finally, new insights for the improvement of the process of nanoparticle synthesis in the RF-ITP system are suggested.

Gas‐Phase Plasma Synthesis of Free‐Standing Silicon Nanoparticles for Future Energy Applications

“…Thermal plasmas are high power discharges (from a few to hundred kWs) usually operated at or close to atmospheric pressures, and are demonstrated as effective environments for synthesizing Si‐NPs using both DC and RF sources. Thermal plasmas have electron and gas temperatures exceeding well above 1 eV, enabling processing of nanomaterials with high melting points.…”

“…On the other hand, Girshick have reported that in the absence of supersaturated vapor, chemical nucleation plays the key role on the growth of nanoparticles . The group of Colombo have performed a series of studies on the modeling of the formation of Si‐NPs in thermal plasmas . They investigated various mechanisms on Si‐NP formation including fluid dynamics studies, turbulent effects on melting and evaporation of precursor, reactor geometry on the size of synthesized Si‐NPs, all providing deeper insight on nanoparticle growth and formation in thermal plasmas.…”

“…Important efforts on understanding the effect of flow dynamics on the size distribution and morphology of nanoparticles have been put by the group of Colombo. They investigated the effect of reactor geometry, and the effect of flow dynamics at different parts of an inductively coupled thermal plasma nanoparticle synthesis tool using fluid dynamics models in order to achieve control on nanoparticle size distribution and improve the throughput of the process . They have also studied on idealized reactor geometries in order to eliminate the background recirculation patterns, where poor quality of nanoparticles were synthesized, and diffusion of nanoparticles to the wall was observed .…”

Modelling for the optimization of the reaction chamber in silicon nanoparticle synthesis by a radio-frequency induction thermal plasma

“…The operating pressure has been fixed at 40 kPa. The electromagnetic field equations are solved in an enlarged domain extending 40 mm outside of the torch in the y-direction, using the extended field approach [3]. The coupled power has been set to 10 kW, which corresponds to typical lab-scale generator plate power of 18 kW.…”

Calculation and application of combined diffusion coefficients in thermal plasmas

“…The method has been successfully applied to modelling a wide range of phenomena in thermal plasmas. These include demixing in welding arcs 2 3 , plasma torches 4 , arc plasma reactors 5 6 , and inductively-coupled rf plasmas in gas mixtures 7 8 9 10 , mixing of metal vapour in welding arcs 11 12 13 , mixing of air into plasmas 14 15 16 17 18 19 20 21 22 23 , mixing of polymer vapours into the arc in circuit breakers 24 25 26 27 28 29 , and expansion of metal vapour ablated by a laser into the surrounding air 30 .…”