NIST, NASA Release New Nanotube Measurement Report

The National Institute of Standards and Technology, in collaboration with NASA, has published detailed guidelines for making essential measurements on samples of single-walled carbon nanotubes (SWCNTs). NIST said the new guide, titled "Measurement Issues in Single Wall Carbon Nanotubes," constitutes the current best practices for characterizing one of the most promising and heavily studied of the new generation of nanoscale materials.

The nanotubes are essentially cylinders of carbon atoms with a wall only one atom thick and a diameter of a couple of nanometer--but lengths up to several million times their diameter, NIST said. Because of their unique electronic, thermal, optical, and mechanical properties they are being studied for a wide range of applications, including ultra strong fibers for nanocomposite materials, circuit elements in molecular electronics, hydrogen storage components for fuel cells, and light sources for compact, efficient flat-panel displays.

One basic problem is assuring the quality and purity of SWCNT materials, NIST added. All known techniques for producing these tiny tubes also produce large quantities of nanojunk--simple graphite and carbon soot.

NIST says accurate, reliable, and preferably rapid measurement techniques are needed to optimize production processes to create more product and less impurities. These will help to control cleaning and purifying processes and ultimately to improve the confidence of buyers and sellers of SWCNT materials.

In 2003, NIST and NASA researchers started addressing the problem by sponsoring a series of workshops devoted to nanotube measurements. The new guide grew out of the second workshop in 2005 and represents what industry, government, and academic researchers regard as the most useful and accurate measurement techniques for characterizing the purity of SWCNT samples.

The techniques discussed include thermogravimetric analysis; near-infrared spectroscopy; Raman spectroscopy; and optical, electron, and scanned probe microscopy. Researchers from the NASA Johnson Space Center, the University of California at Riverside, Boston University and the NASA Langley Research Center contributed to the guide.

Copies of this and other guides in the series are available at NIST's The "How To Measure" Book Series Web site at www.nist.gov/public_affairs/practiceguides/practiceguides.htm.

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