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Abstract The use of silicon nanoparticles for lithium-ion batteries requires a precise control over both their average size and their size distribution. Particles larger than the generally accepted critical size of 150 nm fail during lithiation because of excessive swelling, while very small particles (<10 nm) inevitably lead to a poor first cycle coulombic efficiency because of their excessive specific surface area. Both mechanisms induce irreversible capacity losses and are detrimental to the anode functionality. In this manuscript we describe a novel approach for enhanced growth of nanoparticles to ∼20 nm using low-temperature flow-through plasma reactors via pulsing. Pulsing of the RF power leads to a significant increase in the average particle size, all while maintaining the particles well below the critical size for stable operation in a lithium-ion battery anode. A zero-dimensional aerosol plasma model is developed to provide insights into the dynamics of particle agglomeration and growth in the pulsed plasma reactor. The accelerated growth correlates with the shape of the particle size distribution in the afterglow, which is in turn controlled by parameters such as metastable density, gas and electron temperature. The accelerated agglomeration in each afterglow phase is followed by rapid sintering of the agglomerates into single-crystal particles in the following plasma-on phase. This study highlights the potential of non-thermal plasma reactors for the synthesis of functional nanomaterials, while also underscoring the need for better characterization of their fundamental parameters in transient regimes.
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In-flight iron ore reduction and nanoparticle formation in an atmospheric pressure hydrogen microwave plasma
Abstract The in-flight reduction of iron ore particles using an atmospheric pressure hydrogen plasma is investigated. Iron ore particles with a size less than 75 µm are aerosolized and carried with an argon-hydrogen (90%–10%) gas mixture through an atmospheric pressure microwave plasma. After the treatment, the collected particles are observed to follow three distinct populations: (i) fully reduced nanoparticles, (ii) partially reduced spheres, larger than the feedstock, and (iii) partially melted, partly reduced agglomerates. A model is developed to explain the possible mechanism for the origin of the three populations. The nanoparticles (i) are found to be likely formed from the previously evaporated material whereas the particles (ii) and (iii) result from the partial/complete melting of the particles and agglomerates flowing through the reactor. The gas temperature is estimated to be more than 2000 K, which enables the rapid melting, evaporation, and reduction of these particles within residence times of only a few 10 ms.
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- Award ID(s):
- 2011401
- PAR ID:
- 10512745
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics D: Applied Physics
- Volume:
- 57
- Issue:
- 35
- ISSN:
- 0022-3727
- Format(s):
- Medium: X Size: Article No. 355201
- Size(s):
- Article No. 355201
- Sponsoring Org:
- National Science Foundation
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