Researchers Recycle Carbon Nanotube Sheets without Compromising Properties

TAGS:  Polymer Reinforcement     Sustainability / Natural Solutions    

Researchers from IMDEA Materials Institute have published work demonstrating the ability to recycle high-performance carbon nanotube (CNT) sheets.

They recycled while preserving their shape, structural alignment, mechanical and electrical properties, and intrinsic flexibility.

Ability to Displace CO₂ Intensive Materials

It represents a significant advance in the field of sustainable nanostructured materials and in the viability of fibers, sheets, and textiles made of carbon nanotubes to play a key role in the future green energy transition.

“This research represents a crucial step towards manufacturing and usage of sustainable and recyclable CNT fibers and sheets,” explained Dr. Anastasiia Mikhalchan, senior research associate at IMDEA Materials and Co-PI of the project. “These will be able to displace widespread CO₂-intensive materials, such as conventional carbon fibers and some metals like copper, decreasing our future CO₂ emissions footprint”.

“Our work demonstrates that high-performance materials made from carbon nanotubes are recyclable and can be reused in the same application as structural reinforcement or electrical conductors. This is due to the fact that neither their continuity, alignment, and mechanical properties nor their conductivity is affected by recycling. This is the first attempt in this direction, addressing a critical need in society,” she added.

Enabling Usage as Reinforcement in Composite Laminates

The work utilizes carbon nanotubes that are rapidly grown and directly assembled into freestanding network materials by means of floating catalyst chemical vapor deposition (FCCVD) synthesis process.

These CNT fibers and sheets possess high structural toughness and flexibility as well as high mechanical, electrical and thermal properties. This enables their usage in structural reinforcement in composite laminates, as well as printable strain/stress sensors, electrical conductors, and flexible battery anodes, among other applications.

In addition to the demonstrated recyclability in the macroscopic sheet-format, the researchers envision the future possibility of next-level disintegration of the recycled sheets to their building blocks – CNTs – in liquid crystalline solutions, which could then be re-spun into a new high-quality fiber.

“This prospective is similar to breaking down a LEGO model into its individual bricks, and then re-building the original model with the same shape, robustness, and quality,” explained Dr. Mikhalchan. “This is never possible with conventional carbon fibers because their crystalline structure is formed by fused crystallites in the graphitization process, so they cannot be “broken down” into individual crystallites and re-graphitized again into a continuous fiber filament. In contrast, carbon nanotubes are capable of dissolution in superacid and can be re-spun into a fiber, which is a matter of future confirmation”.

Transforming Hydrocarbons into Nanocarbons

This pioneering work is supported by the Rice University-led Carbon Hub Initiative. IMDEA Materials’ Multifunctional Nanocomposite research group, led by Dr Juan J. Vilatela, is an active member of the initiative, alongside research institutions such as the University of Cambridge, Stanford University, Georgia Tech, and MIT.

Carbon Hub is targeting a zero-emission future, and together with the stakeholders from the oil & gas industry, pursue the new paradigm of sustainable co-production of clean hydrogen and advanced carbon nanostructured materials from natural gas and oil.

Instead of burning hydrocarbons to generate energy while releasing gigatons of CO₂ into the atmosphere, the Initiative proposes the innovative transformation of hydrocarbons into high-performance value added nanocarbons (such as CNT fibers and sheets) with cogenerating net clean energy as (turquoise) hydrogen.

Presently, the world’s CNT production capacity is in the order of 10 kt/year, a rate which is increasing at roughly 30% annually. However, this could accelerate to the megaton scale if the Carbon Hub efforts are successful and nanocarbons start displacing metals.

Making Extremely Tolerant to Defects

The work demonstrated by IMDEA Materials researchers is another milestone in this trajectory, confirming that value-added carbon nanotube materials are, by their nature, recyclable and can be re-used in the same application. Their network structure and inherent toughness, similar to ductile polymers, makes them extremely tolerant to defects and therefore suitable for re-use and re-processing as high added value materials.

“Even three years ago, there was little interest in recycling CNT-based materials, but now it is becoming a far more relevant topic”, Dr. Mikhalchan stated. “We believe our research will stimulate the scale-up of manufacturing high-performance CNT materials and their faster adoption by industry, knowing that such materials offer sustainability and recyclability and are capable of reducing component weight and industry’s CO₂ footprint”.

Source: IMDEA Material Institute