Engineering Controlled Ignition for Tunable Graphitic Carbon Tube Synthesis

Significance 

The synthesis of carbon-based materials with precise control over their properties and structures has been a longstanding challenge in materials science and engineering. Traditional methods for producing carbon materials involve either peeling graphene from graphite or chemically synthesizing graphene derivatives. However, these approaches often suffer from limitations related to tunability, scalability, cost, and environmental impact. The study discuss a novel approach that harnesses the principles of combustion, pyrolysis, and chemical transformations to create tunable graphitic carbon tubes. This method offers promising applications in diverse fields, including catalysis, electrochemistry, optoelectronics, separation/storage, and microelectronics.

Combustion and pyrolysis are complex processes with intricate interactions between chemical reactions and fluid dynamics. Combustion, characterized by its highly exothermic nature, has often been considered a “run-away” reaction due to its difficulty to control and direct. On the other hand, pyrolysis, the incomplete combustion of materials, has potential applications in carbon material synthesis. The key challenge lies in efficiently steering these processes across different length scales, especially in the nanoscale and microscale regimes.

In a new study published in Angewandte Chemie International, Chuanshen Du, Paul Gregory, Dhanush U. Jamadgni, Alana M. Pauls, Julia J. Chang, Rick W. Dorn, Andrew Martin, E. Johan Foster, Aaron J. Rossini, and Martin Thuo from the North Carolina State University introduced a new approach that combines surface modification, controlled ignition, and chemical transformations to create carbon tubes with tailored properties. The central idea involves grafting alkylsilanes onto cellulose fibers, followed by flash pyrolysis. The surface-grafted alkylsilanes undergo thermal degradation into non-flammable SiO2, resulting in surface ignition and inward propagation of the ignition front. This “inside-out” thermal degradation process transforms combustion into pyrolysis, leading to the formation of graphitic carbon tubes. The use of surface modifiers with higher flashpoints delays surface ignition, allowing controlled degradation from the fiber’s core.

To further fine-tune the properties of the synthesized carbon tubes, the authors introduce the concept of incorporating synthons into the cellulose fibers prior to thermal degradation. These additives can act as “accelerators” or “heat sinks,” altering the heat dissipation and thermodynamics of the ignition process. For instance, the addition of MnCl2, which exothermically oxidizes upon heating, accelerates ignition propagation, leading to thinner-walled tubes. Conversely, the introduction of KCl, which absorbs heat without transformation, acts as a heat sink, resulting in thicker-walled tubes. This approach showcases the remarkable potential for tailoring carbon tube properties through controlled chemical interactions.

The synthesized carbon tubes are thoroughly characterized using various techniques such as SEM, EDS, XPS, Raman spectroscopy, solid-state NMR, and BET surface area analysis. These characterizations confirm the successful transformation of cellulose into graphitic carbon tubes and offer insights into the underlying chemical processes. The resulting tubes exhibit different wall thicknesses, structures, and properties based on the introduced additives, demonstrating the versatility of the method.

The authors’ proposed approach presents a powerful strategy for the controlled synthesis of graphitic carbon tubes with tunable properties. By coupling surface modification, controlled ignition, and chemical transformation, the authors have developed a versatile platform that can be extended to various applications. The method’s ability to incorporate secondary reactants for precise property modulation opens up new avenues for tailoring carbon materials for specific functions. The study underscores the importance of understanding combustion and pyrolysis kinetics and thermodynamics for engineering advanced materials and lays the foundation for future research and applications in the field.

Engineering Controlled Ignition for Tunable Graphitic Carbon Tube Synthesis - Advances in Engineering

Reference

Chuanshen Du, Paul Gregory, Dhanush U. Jamadgni, Alana M. Pauls, Julia J. Chang, Rick W. Dorn, Andrew Martin, E. Johan Foster, Aaron J. Rossini, Martin Thuo. Spatially Directed Pyrolysis via Thermally Morphing Surface Adducts. Angewandte Chemie International Edition, 2023;

Go To Angewandte Chemie International Edition

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