Comparative Study of Metal Substrates for Improved Carbonization of Electrospun PAN Nanofibers.

Martin Wortmann,Christian Hellert,Bennet Brockhagen,Jan Lukas Storck,Natalie Frese,Andrea Ehrmann,Timo Grothe,Elise Diestelhorst

doi:10.3390/polym14040721

Martin Wortmann, Christian Hellert + Show 6 more

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https://doi.org/10.3390/polym14040721

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Journal: Polymers	Publication Date: Feb 13, 2022
Citations: 8	License type: CC BY 4.0

Affiliation: Bielefeld University, Hochschule Bielefeld

Abstract

Carbon nanofibers are used for a broad range of applications, from nano-composites to energy storage devices. They are typically produced from electrospun poly(acrylonitrile) nanofibers by thermal stabilization and carbonization. The nanofiber mats are usually placed freely movable in an oven, which leads to relaxation of internal stress within the nanofibers, making them thicker and shorter. To preserve their pristine morphology they can be mechanically fixated, which may cause the nanofibers to break. In a previous study, we demonstrated that sandwiching the nanofiber mats between metal sheets retained their morphology during stabilization and incipient carbonization at 500 °C. Here, we present a comparative study of stainless steel, titanium, copper and silicon substrate sandwiches at carbonization temperatures of 500 °C, 800 °C and 1200 °C. Helium ion microscopy revealed that all metals mostly eliminated nanofiber deformation, whereas silicone achieved the best results in this regard. The highest temperatures for which the metals were shown to be applicable were 500 °C for silicon, 800 °C for stainless steel and copper, and 1200 °C for titanium. Fourier transform infrared and Raman spectroscopy revealed a higher degree of carbonization and increased crystallinity for higher temperatures, which was shown to depend on the substrate material.

Highlights

Poly(acrylonitrile) (PAN) nanofibers are typically produced either by needle-based or by needleless electrospinning methods and are a common precursor for carbon nanofibers (CNF) [1,2]
In our most recent study, we showed that stabilization and incipient carbonization could be improved by sandwiching the PAN nanofiber mats between aluminum or stainless steel sheets [23]
The highest nanofiber integrity was found for the Si substrate after carbonization at 500 ◦C, which was not sufficient to reach a high degree of carbonization, while such nanofibers may be well suitable for producing nano-composites with enhanced mechanical properties, as compared to the pure polymer

Summary

Introduction

Poly(acrylonitrile) (PAN) nanofibers are typically produced either by needle-based or by needleless electrospinning methods (cf. Figure 1A) and are a common precursor for carbon nanofibers (CNF) [1,2]. Due to their outstanding electrical and mechanical properties, CNF are promising for nano composites [3,4,5]. Much research has focused on the optimization of process parameters such as heating rate and terminal temperature [9,10,11]. The heating rate, especially during stabilization, plays a crucial role in retaining the original nanofiber morphology [2,12,13]

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