Manufacturing Bits

By Mark Lapedus for Semiengineering

The Masdar Institute of Science and Technology has developed a process that will transform carbon nanotube powder into so-called buckypaper.

Buckypaper is a thin sheet made from carbon nanotubes. They are sometimes known as multi-walled carbon nanotube sheets. Meanwhile, carbon nanotubes are tube-shaped materials, which are 100,000 times smaller than the diameter of human hair. These structures have good electrical, chemical, thermal and mechanical properties.

Typically, carbon nanotubes come in dust-like materials. Using an old process, carbon nanotube dust can be turned into large sheets or buckypapers.

The problem? The buckypaper fabrication process is difficult to scale and expensive.

In a typical flow, the carbon nanotube dust must be purified. Then, the materials are suspended in deionized water. They are poured into a filtration unit and then settle on the surface of the filtration unit. At that point, they dry and turn into nanotube sheets.

Researchers from Masdar Institute has developed a different approach. They used a surface-engineered tape-casting (SETC) technique to develop buckypapers. In this process, a carbon nanotube film is coated on a substrate. Then, the process is repeated, where one film resides on top of the other.

“Common buckypaper fabrication methods used today are membrane filtration and chemical vapor deposition. However both methods have severe limitations, with membrane filtration restricting the size of the produced buckypaper to the size of the membrane and apparatus used, and chemical vapor deposition being exceedingly expensive,” said Rahmat Susantyoko, a researcher at the Masdar Institute, based in Masdar City in Abu Dhabi, United Arab Emirates.

“Our technique utilizes tape-casting with a special type of substrate, which we engineered in the lab, that allows us to easily peel off the buckypaper from the supporting substrate, resulting in a free-standing buckypaper film,” Susantyoko said. “This new technique could boost the development of market-ready applications, including high-power lithium-ion batteries and low-cost vanadium-redox-flow batteries.”

The technology will give researchers insights into catalysts, which are used in chemical reactions. Catalysts are used to break or make bonds in chemical reactions.

To watch reactions in real time, NIST devised an electron microscope and a high-resolution camera. Researchers tracked the chemical reactions of cobalt nanoparticles. These materials act as catalysts for growing single-walled carbon nanotubes.

For years, researchers assumed that carbon nanotubes were formed a certain way. In the formation of carbon nanotubes, catalysts attract gas molecules. The reactions take place on the surface.

NIST had a different finding, however. For cobalt nanoparticle catalysts, the surface reaction is not the only factor. The entire particle is involved in the process.

The research provides new insights into catalysts. “If you want to make a good catalyst, you want to know why it works and why it doesn’t work, and it often changes in the atomic structure of the particle that hold the key to that understanding,” said NIST researcher Renu Sharma.

These businesses are developing a range of products. For example, X-wave Innovations is developing a 3D, non-destructive testing technology to detect defects in parts produced by advanced manufacturing.

Another business, called Low Thermal Electronics, is developing a voltage source to provide precise high-voltage and high-resistance measurements in an instrument. In addition, Quantum Diamond Technologies is developing a benchtop analysis system for quantifying the magnetic properties of single nanoparticles.

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