A Two-Step Microwave Annealing Process for PAN Pre-Oxidation through a TM-Mode Cavity

Area of Science:

• Materials Science
• Chemical Engineering
• Microwave Processing

Background:

• Traditional carbon fiber pre-oxidation is time-consuming.
• Optimizing pre-oxidation is crucial for high-performance carbon fibers.
• Existing methods often lack efficiency and uniformity.

Purpose of the Study:

• To develop a novel microwave annealing system for efficient carbon fiber pre-oxidation.
• To investigate the effects of microwave annealing on polyacrylonitrile (PAN) fiber structure and properties.
• To significantly reduce processing time for carbon fiber pre-oxidation.

Main Methods:

• A TM-mode resonant cavity microwave annealing system with a silicon carbide (SiC) susceptor was designed.
• A two-step microwave annealing process was applied to oxidize polyacrylonitrile (PAN) fiber.
• Characterization techniques included scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman spectroscopy.

Main Results:

• The microwave annealing system achieved a high aromatic index of 66.39% in just 13 minutes.
• This represents a 9-fold increase in speed compared to traditional methods.
• Raman spectra indicated a sheath-core factor closer to one for microwave-treated specimens, suggesting improved uniformity.

Conclusions:

• The novel microwave annealing system offers a significantly faster and efficient method for carbon fiber pre-oxidation.
• The system provides both nonthermal and thermal treatments, suitable for various dielectric properties.
• Microwave annealing promotes structural uniformity, crucial for advanced carbon fiber applications.