Cellulose-Based Carbon Fibers: Enhanced Orientability by Boric Acid During Carbonization

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Cellulose-based carbon fibers (CFs) offer a sustainable alternative to petroleum-based materials.
• Achieving high Young's moduli in CFs is crucial for advanced structural applications.
• Controlling precursor structure during carbonization is key to enhancing CF properties.

Purpose of the Study:

• To present a scalable, continuous process for producing high-modulus cellulose-based carbon fibers (CFs).
• To investigate the effect of boric acid (BA) doping on precursor orientability and CF properties.
• To elucidate the microstructural mechanism behind BA's influence on CF formation.

Main Methods:

• Developed a continuous carbonization process reaching up to 2000 °C.
• Utilized boric acid (BA)-doped viscose precursor yarns.
• Analyzed structural parameters (crystallite dimensions, lattice spacing, orientation) and electrical/mechanical properties of CFs.

Main Results:

• Achieved cellulose-based CFs with Young's moduli up to 230 GPa.
• BA doping significantly improved precursor orientability, leading to highly oriented CFs.
• BA promoted graphite-like structures and alignment, resulting in ~3x higher electrical conductivity and ~2x higher Young's modulus compared to undoped CFs.

Conclusions:

• Boric acid doping is an effective strategy for enhancing cellulose-based carbon fiber properties.
• The improved properties are attributed to enhanced structural ordering and graphite-like structure formation.
• A microstructural mechanism explaining BA's effectiveness during thermal conversion was proposed.