Floating Catalyst Chemical Vapor Deposition Derived Carbon Nanotube Sheets: Optimization and Applications
Creators: name: Sehrawat, Manoj
Publisher: name: RMIT University
Year: 2025
Subjects: classificationCode: 400101
subject: Aerospace materials
classificationCode: 401807
subject: Nanomaterials
classificationCode: 400102
subject: Aerospace structures

description: The physical macroforms of carbon nanotubes (CNTs) have long been considered a crucial link for translating their exceptional nanoscale properties into practical materials. However, productivity and scalability issues arising from the complex synthesis process have posed significant challenges. The aim of this PhD research is to gain a comprehensive understanding of the direct spinning of CNT aerogel via floating catalyst chemical vapor deposition (FCCVD) to produce CNT sheets. To achieve this, studies were conducted using an indigenously developed FCCVD setup, focusing on the role of underlying parameters in synthesizing non-woven CNT sheets. The process was thoroughly optimized to identify parameters that ensure maximum productivity (carbon conversion rate of 7.5 mg/min), homogeneous purity (IG/ID &gt; 7), and extended production time. Observations and qualitative analyses, including various characterizations, helped identify the functional roles of the input parameters. 
The synthesized CNT sheet was then explored to advance current efforts in structural materials for aerospace and environmental remediation applications. First, the CNT sheets were applied to oil-water separation to address the issue of oil spills. The dense CNT sheets were transformed into CNT sponges using a simple foaming approach, maintaining the hydrophobic nature of the CNTs. These sponges were then mechanically reinforced through nano welding of the joints with amorphous carbon, significantly enhancing their compressive strength, modulus, and oil sorption properties. The resulting amorphous carbon-coated CNT sponge demonstrated outstanding results in absorbing oils and organic solvents, outperforming several existing CNT-based materials. Moreover, the developed method required significantly less energy input per gram compared to existing sponge materials, making it a sustainable choice for environmental remediation. 
Additionally, the study addressed the low fracture toughness of carbon fiber reinforced polymer (CFRP) composites, a well-known limitation in aerospace applications. The current practice of interleaving CNT films in CFRP composites is limited by their thickness, density, and weak interlaminar bonding with the matrix. To overcome this, the study proposed coating CNTs with ethanolamine to enhance the wettability and bonding of the CNT sheet, regardless of their thickness. The resulting ethanolamine-coated CNT (EACNT) modified CFRP composites exhibited a remarkable improvement in Mode I and Mode II fracture toughness values due to increased interaction with the matrix material. The toughening mechanisms and chemical bonding are discussed in detail for a thorough understanding. 
Finally, the study concludes by providing a brief outlook on how the current work can be further extended to foster advancements and innovations in the respective fields for better outcomes.