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

纳米级探索性研究(NER)：在电磁场控制的甲烷氧火焰中产生不同碳纳米结构的新方法项目摘要这项研究调查了一项意外发现，可能导致一种廉价的方法来制备各种碳纳米结构。作为研究大气氧燃料火焰中碳结构的实验的一部分，使用位于燃料(甲烷中4%的乙炔)和氧化剂(50%氧气和50%氮气)形成的富氧对流火焰的燃料侧的镍基催化载体，观察了碳纳米管和碳纳米纤维的形成。在相同的火焰参数和相同的催化材料下，从逆流火焰的不同位置观察并获得了种类繁多的碳纳米结构。这是第一次观察到多种形式的纳米结构在一个过程中被产生并被选择性地收获。观察到的碳结构包括：碳纳米管(CNTs)和多壁纳米管(MWNT)束，结晶度不同的纳米纤维，螺旋规则卷曲的管状碳纳米纤维，矩形截面的带状卷曲纳米纤维，以及具有规则内部碳层结构的长(~0.2 mm)均匀直径(~100 nm)管状纳米纤维。所有这些碳纳米结构的变化都可以在逆流氧焰燃料侧的不同区域找到和收获。其中一些结构最近才在其他实验室精心设计的化学气相沉积实验中合成。这项研究的一个关键目标是探索在早期的氧燃料逆流燃烧器研究中观察到的纳米结构的生长和类型是否可以像初步实验所建议的那样使用电磁场来控制。潜在地，这可能导致一种新的制造工艺，用于高速生产不同的纳米结构。布罗德影响目前，氧焰是热解碳(碳黑)的主要工业来源。火焰还被广泛用于大规模生产纳米陶瓷和其他纳米材料。具有可控结构和形貌的碳纳米管和碳纳米纤维的高速合成方法的发展使大量需要碳纳米材料的应用成为可能。这包括具有独特机械和电磁性能的现代复合材料、储氢元件、化学活性材料、燃料添加剂等。初步实验结果表明，在对流富氧火焰的催化种子燃料区形成碳纳米结构，以及应用电磁场控制碳纳米结构的生长速度的初步实验结果表明，从简单的对流燃烧设施的不同区域制造和收获特定类型的纳米结构是可行和可控的。

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..