NER: Novel Method of Producing Different Carbon Nanostructures in Oxy-Methane Flames Controlled by Electro-Magnetic Fields

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Nanoscale Exploratory Research (NER): Novel Method of Producing Different CarbonNanostructures in Oxy- Methane Flames Controlled by Electro-Magnetic FieldsProject SummaryThis study investigates an adventitious discovery that may lead to an inexpensive means for producing a variety of carbon nanostructures. As part of experiments examining carbon structures in atmospheric oxy-fuel flames, the formation of carbon nanotubes and carbon nanofibers was observed using a nickel-based catalytic support positioned at the fuel side of an oxygen-enriched opposed-flow flame formed by streams of fuel (4% acetylene in methane) and oxidizer (50% oxygen and 50% nitrogen). For constant flame parameters and the same catalytic material, a wide variety of carbon nanostructures were observed and harvested from different positions in the opposed-flow flame. This is the first observation of multiple forms of nanostructures being generated in a single process and selectively harvested. Observed carbon structures include: carbon nanotubes (CNTs) and multi-wall nanotubes (MWNT) bundles, nanofibers with varying degrees of crystallinity, helical regularly coiled tubular carbon nanofibers, ribbon-like coiled nanofibers with rectangular cross section, and, finally, long (~0.2 mm) uniform-diameter (~100 nm) tubular nanofibers exhibiting a regular internal structure of carbon layers. All these variations of carbon nanostructures could be found and harvested in different regions of the fuel side of the opposed-flow oxy-flame. Some of these structures have only recently been synthesized in other laboratories in carefully designed chemical vapor deposition experiments. A key objective of this study is to explore whether the growth and type of nanostructures observed in the earlier studies on an oxy-fuel, counter-flow burner can be controlled using electromagnetic fields, as suggested by preliminary experiments. Potentially, this could result in a new manufacturing process for high-rate production of different nanostructures.Broader ImpactAt present, oxy-flames are the major industrial source of pyrolytic carbon (carbon black). Flames are also widely used for large-scale production of nanoceramics and other nanomaterials. The development of a high-rate synthesis method for carbon nanotubes and carbon nanofibers with controlled structure and morphology makes feasible numerous applications requiring large amounts of carbon nanomaterials. This includes modern composites with unique mechanical and electromagnetic properties, hydrogen storage elements, chemically active materials, fuel additives, etc. Preliminary experimental results showing carbon nanostructures are formed in a catalytic seeded fuel zone of an opposed-flow oxygen-enriched flame and on the application of electromagnetic fields to control the growth rates of carbon nanostructures suggest that manufacturing and harvesting specific types of nanostructures from different regions of a simple opposed-flow combustion facility is feasible and controllable..