(18d) Production of CNT Yarns from Methane Gas for Use As Filaments in Incandescent Bulbs: Effect of Hydrogen Co-Feeding on the Properties of As-Spun CNT Yarns

In spite of the excellent electrical, mechanical and optical properties of carbon nanotubes (CNTs), their application in electronics devices have been limited. Therefore, organization of CNTs into their macroscopic sizes while maintaining the quality of the individual CNTs could be instrumental to paving the way for further application of CNTs, e.g. in incandescent bulb. Application of CNTs as filament to replace tungsten in incandescent bulbs requires the assembly of CNTs into macroscopic strings called yarns. Tungsten as a filament in incandescent bulbs is currently being phased out and undergoing outright ban in many countries owing to its very low efficiency (only about 5% of the energy input into incandescent bulbs with tungsten as filament is used for lightening and the rest is dissipated as heat and resultant emissions) [1]. However, the use of CNT yarns as filament presents an option for improving the environmental and economical inefficiency of tungsten based incandescent bulbs. In addition, co-feeding of hydrogen during the production of CNTs has been reported to be detrimental to the morphology, electrical conductivity and mechanical properties of synthesized CNT yarns [2].

Spontaneous assembly of single walled, double walled and even mixed CNTs during synthesis due to Van der Vaal forces [3, 4] is enhanced in this study, where carbon nanotubes were synthesized using methane as carbon source and ferrocene as catalyst and spun into yarns in a vertical Swirled Floating Catalyst Chemical Vapour Deposition (SFCCVD) reactor. Furthermore, investigation of the effect of hydrogen co-feeding on length, compactness and number of walls of the CNTs produced from saturated hydrocarbon feedstock was carried out.

Experiments are on-going, however, it is expected that the results of the investigation will shed light on the relationship that exists between the mechanical property and electrical property of the as-produced CNTs as will be obtained from Raman spectroscopy and X-ray diffraction. Furthermore, the study will provide information on the effect of hydrogen co-feeding on the morphology, crystallinity, mechanical property and electrical conductivity of the as-produced yarns. The results could form a basis to arguably compare the obtained results with literature such as the report of Tsentalovich et al [5]. At the moment, results from our preliminary investigations indicate the predominance of multi-walled CNTs during the production.

References

[1] MacIsaac, D., Kanner, G., & Anderson, G. (1999). Basic physics of the incandescent lamp (lightbulb). The physics teacher, 37(9), 520-525.

[2] Ma, Y., Dichiara, A. B., He, D., Zimmer, L., & Bai, J. (2016). Control of product nature and morphology by adjusting the hydrogen content in a continuous chemical vapor deposition process for carbon nanotube synthesis. Carbon, 107, 171-179.

[3] Li, Y., Zhang, X. B., Tao, X. Y., Xu, J. M., Huang, W. Z., Luo, J. H., ... & Geise, H. J. (2005). Mass production of high-quality multi-walled carbon nanotube bundles on a Ni/Mo/MgO catalyst. Carbon, 43(2), 295-301.

[4] Colomer, J. F., Henrard, L., Van Tendeloo, G., Lucas, A., & Lambin, P. (2004). Study of the packing of double-walled carbon nanotubes into bundles by transmission electron microscopy and electron diffraction. Journal of Materials Chemistry, 14(4), 603-606.

[5] Tsentalovich, D. E., Headrick, R. J., Mirri, F., Hao, J., Behabtu, N., Young, C. C., & Pasquali, M. (2017). Influence of carbon nanotube characteristics on macroscopic fiber properties. ACS applied materials & interfaces, 9(41), 36189-36198.