Conductive multi-walled boron nitride nanotubes by catalytic etching using cobalt oxide

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Boron nitride nanotubes (BNNTs) exhibit exceptional thermal stability, resisting oxidation below 1000 °C.
• BNNTs are typically electrical insulators with a wide band gap of 5 eV.
• Low-temperature etching and electrical property modification of BNNTs present significant challenges.

Purpose of the Study:

• To demonstrate a low-temperature catalytic oxidation method for etching BNNTs.
• To convert the electrical properties of BNNTs from insulating to conductive.
• To investigate the structural and electrical changes in BNNTs after etching.

Main Methods:

• Multi-walled BNNTs (MWBNNTs) were impregnated with a Cobalt precursor (Co(NO₃)₂·6H₂O).
• The impregnated MWBNNTs were heated at 350 °C in an air atmosphere.
• Structural analysis and electrical property measurements were performed on the etched MWBNNTs.
• Theoretical calculations were employed to understand the conductivity mechanism.

Main Results:

• Catalytic oxidation at 350 °C effectively etched the surface of MWBNNTs, creating diverse structures like pits and thinned walls.
• The tubular structure and original crystallinity of the MWBNNTs were preserved post-etching.
• Etched MWBNNTs exhibited a transition from electrical insulation to electrical conductivity.
• Theoretical analysis revealed the formation of new energy states and a Fermi level shift as the cause of conductivity.

Conclusions:

• Low-temperature catalytic oxidation is an effective method for etching and modifying the electrical properties of BNNTs.
• The developed method allows for the conversion of BNNTs into conductive materials while maintaining their structural integrity.
• This research provides a pathway for utilizing BNNTs in applications requiring conductive nanomaterials.