Superior-Strong Carbon Nanofibers via Electrospinning Machine and PAN Jetting

Introduction 

Carbon nanofibers (CNFs) exhibit significant advantages in electrical and mechanical properties, making them ideal for applications in aerospace, automotive, and energy sectors. However, maximizing the benefits of these scale effects remains a challenge. Polyacrylonitrile (PAN) jetting offers promising features due to its continuity, microscopic structure, and scale effects, which can be enhanced through structural modifications at the microscopic level. By understanding the initiation of PAN jetting and altering its microstructure, it becomes possible to produce superior-strong carbon nanofibers through additive nanostructuring and carbonization.

Abstract 

This study presents a method for additive nanostructuring and carbonization of PAN jetting via electrospinning machine to form continuously superior-strong carbon nanofibers. By analyzing the electrostatic submicro-initiation of PAN jetting and altering its microstructure at the nanoscale, zigzag conformations of molecular chains within the PAN nanofibers were achieved. This method, combined with the radial distribution pattern of shear stress, enabled the formation of continuous carbon nanofibers with a diameter of ~20 nm and a tensile strength of 212 GPa, surpassing that of existing mainstream fibers.

Main Content and Innovative Results

The research focuses on developing a method for additive nanostructuring and carbonization of PAN jetting to produce superior-strong carbon nanofibers. The key steps include:

• Nanoforming of PAN Fibers: The study proposes a theoretical framework for the electrostatic jetting of PAN fibers, analyzing the electric stress on the droplet meniscus, shear stress within the fluid, and the minimum steady-state voltage required for continuous jetting. The results show that reducing the minimum steady-state voltage and increasing the spacing between the dispensing needle and collector can effectively decrease the fiber diameter to the nanoscale.

• Nanostructuring of Molecular Chains: By leveraging the radial distribution of shear stress, the researchers achieved a core-shell structure in PAN fibers, with zigzag conformation on the outside and helical conformation on the inside. The ability to control the molecular chain conformation through voltage manipulation enabled the formation of fibers with tunable diameters and enhanced mechanical properties.

• Additive Manufacturing of PAN Fibers: The study demonstrates the additive manufacturing of PAN fibers on various substrates, including silicon, carbon micro-scaffolds, and micro-pillars. The fibers were deposited in arrays with uniform spacing, showcasing the versatility of the method for fabricating nanostructures on different platforms.

• Carbonization and Performance Evaluation: The PAN fibers were stabilized and carbonized to produce continuous carbon nanofibers. Atomic force microscopy (AFM) was used to measure the mechanical properties of the resulting fibers, revealing a tensile strength of up to 212 GPa, which far exceeds that of existing carbonaceous fibers.

Conclusion  

The study successfully developed a method for additive nanostructuring and carbonization of PAN jetting fibers with electrospinning device, achieving continuous carbon nanofibers with superior mechanical properties. The combination of nanoforming, molecular chain nanostructuring, and carbonization enabled the production of fibers with ultra-high strength and tunable diameters. This method not only enhances the mechanical properties of carbon fibers but also introduces multifunctionality, such as superhydrophilicity, piezoelectric properties, and cycling stability. The findings open new opportunities for the application of carbon nanofibers in advanced energy storage devices, electrocatalysis, and other high-performance materials.

Electrospinning Nanofibers Article Source: 

https://doi.org/10.1038/s41378-024-00800-7