Electronic Design

Process Perfected For Cost-Effectively Making Large Sheets Of Carbon Nanotubes

Commercial carbon-nanotube (CNT) technology has taken a major step forward, going from research in the lab to production in the factory. Nanocomp Technologies Inc. has successfully produced 3- by 6-ft sheets of single-walled CNTs, which is a significant production milestone (Fig. 1).

According to the firm, it has manufactured the largest cohesive sheets of CNT materials to date. Until now, CNTs with lengths of only about tens of micrometers have been produced, usually in powder form instead of sheets, due to the difficulty of mastering a cost-effective production process.

Short CNTs have limited industrial use. That’s because they are difficult to incorporate into existing manufacturing processes. Also, they lack the high-performance properties of longer CNTs. Nanocomp’s breakthrough opens up a wide range of applications in consumer, industrial, military, and OEM electronics markets.

CNTs are the holy grail of future high-performance materials. They feature a unique combination of higher strength-to-weight ratio, superior electrical and thermal conductivity, better flame resistance, and higher-performance electromagnetic interference (EMI) shielding than traditional electronic materials like copper.

Also, CNT materials are 100 times stronger than steel. They’re 30% lighter than aluminum. They can conduct electricity as efficiently as copper. And, they can conduct heat better than other materials, including copper.

“We’re using a regular Allen-Bradley process controller for manufacturing CNTs in a heat furnace. The key to our process is precise computer control that allows us to handle not only single-walled CNTs, but multi-walled ones as well,” explains Peter Antoinette, Nanocomp’s president and chief executive officer (Fig. 2).

“We feed in a catalyst in a very controlled manner, then bring in the gases also in a well-controlled fashion, and do so quickly and in large volumes tailored to whatever we want the process to produce,” Antoinette adds.

While other CNT production processes need post-processing steps, this process doesn’t require any. “The goal our manufacturing scale-up has been to produce ultra-pure material in increasing quantities, with consistency and reliability, utilizing a fully automated process that doesn’t require a PhD to operate,” says Mark Banash, Nanocomp’s vice president of engineering.

“Being able to turn out CNT materials into large volumes quickly is a critical part of our success,” Antionette notes.

These additional post-processing steps using conventional manufacturing steps are the result of significant amounts of impurities that are normally generated by these processes. These impurities must be removed during post-processing, making the cost of CNTs too expensive for commercial markets.

The Nanocomp development opens up a slew of applications. For example, CNTs are highly useful as electrical and thermal conductors, for composite materials, and in energy-storage applications. They can replace heavy metal conductors, creating highly efficient, ultra-light wires for antennas in wireless devices.

Additionally, CNTs can serve as conductors for electronic interconnects, power transfers, motors, transformers, and electro-storage devices. Furthermore, there is the potential to create new thermal-management systems that will more effectively reduce heat buildup in electronics.

Both single-walled and multi-walled CNTs consist of thousands of carbon atoms. Single-walled CNTs feature a single shell of a hexagonal arrangement of carbon material. Multi-walled CNTs offer multiple concentrically nested carbon tubes similar to the rings in a tree trunk.

Although multi-walled CNTs are easier to manufacture than single-walled CNTs, their properties aren’t as useful as the single-walled CNTs. That’s one reason why most work in developing CNTs is being conducted with single-walled nanotubes.

Nanocomp is actively developing novel methods to fabricate its nanotubes into structurally strong and electro-thermally conductive fibers, yarns, and felts. It believes these forms will create value-added intermediates for incorporation into final end-user products.

Nanocomp Technologies Inc.

www.nanocomptech.com

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