Controlled synthesis of silicon nanopowders by inductively coupled thermal plasma
Empa Activities 09/10 Advanced Materials and Surfaces
2026
The synthesis of silicon nanopowders by a thermal plasma process has been investigated. The experimental approach coupled with computational fluid dynamic (CFD) and neural network modeling led to the design of an improved quenching device. The specific surface area of the produced Si-nanoparticles could then be increased from 60 to 210 m2/g.
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Silicon microscale powders were injected in an inductively-coupled RF thermal plasma, leading to the formation of a silicon loaded gas phase that was subsequently quenched. The understanding of the quenching has been investigated also by CFD and neural network modeling. After validation of the code with in-situ diagnostics, the temperature and flow fields as well as the particle growth have been calculated, depending on various process conditions and quenching devices. An improved quenching design could then been developed leading to an increase of the specific surface area (SSA) of the silicon nanopowders from 60 to 210 m 2 g -1, corresponding to equivalent particle average diameters decreasing from 40 to 13 nm. These results were the basis for a new EU-FP7 project (SIMBA) that has started in September 2009. The aim of the project is to up-scale the plasma technology for the synthesis of silicon-based nanoparticles, including on-line monitoring systems, assuring at the same time safety and controlled quality. The produced nanopowders will be evaluated as anode materials in Li-ion batteries.
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Marc Leparoux
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Fig.1: Modeled temperature of the optimized quenching ring design at the quenching plane (top) and 12 mm below (bottom). Modeled 3D parameters: 3-12-80/6, Vin 126 m.s -1, Tin 6000 K, 40 kPa, 90 slpm Ar quench gas.
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Silicon and silicon-based nanoparticles are promising candidates for e.g. anode materials in battery applications or photovoltaics. There is then a need to produce them safely in large quantities while tailoring their composition, size and size distribution. Thermal plasmas may address this need due to their high energy density, their large volume and their controlled processing atmosphere. The thermal plasma synthesis of nanopowders is based on the rapid condensation of a gas phase. This quenching aims to freeze the growth of the particles, and is therefore one of the most important step of the synthesis.
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Fig. 2: Response surface calculated from neural network showing the variation of SSA of the Si nanoparticles as a function of the feeding rate and the quenching gas flow rate.
Support: KTI Link: www.simba-project.eu
Contact: marc.leparoux@empa.ch
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