Laser Synthesis of Single Wall Carbon Nanotubes with Furnace Near the Eutectic Temperature for Ni-C/Co-C

Single Wall Carbon Nanotubes (SWCNTs) have brought great interest due to their exceptional electronic and physical properties in applications including photovoltaics, lithium-ion batteries, and integrated electronics. The impact of electronic type and diameter on device performance is largely influenced by the ability to precisely control SWCNT intrinsic properties during synthesis. The predominant synthesis methods have been chemical vapor deposition, laser vaporization, and arc discharge. Laser vaporization is of particular interest due to the resulting high quality of SWCNTs produced, as well as the ability to systematically control the accompanying diameter distribution through catalyst selection, carrier gas, and furnace temperature.<br/>Results in the literature show that synthesis temperatures ranging from 700-1200 °C have demonstrated a direct correlation to mean SWCNT diameter. The utility of different carrier gases with a range of thermal conductivities can further alter the cooling dynamics to modify the type of SWCNT chirality and SWCNT diameter during laser synthesis. Conventional laser vaporization synthesis for Ni-C and Co-C systems has been primarily studied at furnace temperatures around 1100-1200 °C, where typical quartz tube furnace systems are stable. Synthesis at higher temperatures near the eutectic point of the catalyst system (~1320 °C) are expected to increase SWCNT diameter as well as other physical properties like length and purity given the extended time in the growth phase. <br/>In the present work, an advanced pulsed laser vaporization setup is used. It incorporates high temperature stability furnace tubes (e.g. mullite, SiC, etc.) and complementary endcaps to surpass temperature limitations of a typical quartz tube, realizing temperatures up to 1400 °C . The physical properties of the SWCNT soot synthesized in both argon and helium gas environments over a range of temperatures will be compared. The quality of the as-produced raw SWCNT soot is characterized by thermogravimetric analysis, scanning electron microscopy, and optical absorption spectroscopy to determine a purity level relative to the conventional materials synthesized at 1150 °C. The diameter distributions are analyzed using Raman spectroscopy to establish the fundamental diameter relationship with temperature. Overall, this work will summarize the physical implications of conducting laser synthesis with furnace temperatures near the eutectic temperature for Ni-C/Co-C systems.