Shear modulated percolation in carbon nanotube composites

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Carbon nanotube (CNT) composites are widely studied for their electrical properties.
• Controlling the dispersion and alignment of CNTs is crucial for tailoring composite conductivity.
• Processing conditions significantly influence the microstructure and resulting properties of CNT composites.

Purpose of the Study:

• To investigate the effect of shear processing time on the electrical conductivity of CNT composites.
• To understand the underlying mechanisms responsible for observed changes in conductivity.
• To highlight the importance of processing conditions on CNT dispersion and alignment.

Main Methods:

• Fabrication of CNT composites with fixed filler loading.
• Application of shear processing for varying durations.
• Measurement of electrical conductivity.
• Microstructure characterization using techniques to observe CNT alignment.

Main Results:

• A novel time-dependent percolation transition was observed in sheared CNT composites.
• Electrical conductivity changed by up to 8 orders of magnitude with increased shear processing time.
• Microstructural analysis revealed CNTs aligned along the shear flow direction.
• This alignment led to a significant increase in the percolation threshold and a decrease in conductivity.

Conclusions:

• Shear processing time is a critical factor controlling the electrical conductivity of CNT composites.
• CNT alignment induced by shear flow dramatically impacts the percolation threshold.
• Understanding the response of CNT dispersion states to processing conditions is essential for designing functional CNT composites.