Effect of Sample Geometry on Graphitization of Polyacrylonitrile

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Polyacrylonitrile (PAN) is a precursor for high-performance carbon fibers.
• Controlling the graphitization process is crucial for optimizing carbon material properties.
• Sample geometry can influence material transformation during thermal treatment.

Purpose of the Study:

• To investigate the effect of sample geometry (spheres, nanofibers, films) on PAN graphitization.
• To understand how molecular alignment affects the graphitization behavior across different geometries.
• To analyze chemical and structural changes during oxidation, carbonization, and graphitization stages.

Main Methods:

• Scanning Electron Microscopy (SEM) for surface morphology.
• In situ Thermogravimetric-Infrared (TGA-IR) analysis for chemical changes.
• Elemental analysis, Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) for composition and bonding.
• Synchrotron Wide-Angle X-ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM) for molecular alignment and structure.

Main Results:

• Different geometries exhibit distinct graphitization pathways.
• Molecular alignment, controlled by draw rate during spinning, significantly influences graphitization degree.
• SEM, TGA-IR, elemental analysis, Raman, XPS, WAXD, and TEM revealed geometry-dependent structural and chemical evolution.

Conclusions:

• Sample geometry is a critical factor in polyacrylonitrile graphitization.
• Optimizing molecular alignment through controlled spinning is essential for tailoring graphitic structures.
• This study provides insights into designing advanced carbon materials from PAN precursors.