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October 20, 2008

The Buckypaper Race to Market

1. Dr. Xiangwu Zhang, an Assistant Professor in the College of Textiles at North Carolina State University, hydroentangling treats the stack of unentangled fibers as a whole to produce strong fabrics or membranes, and hence it is an excellent method to assemble carbon nanotubes (CNTs), which are too small to be manipulated individually. The continuous hydroentangling process used in the textile industry is able to produce nonwovens at a speed up to 400 meters per minute. [H/T to reader Brock one of these links]

Zhang demonstrated that the tensile strength of hydroentangled CNT membrane with a thickness of 100 µm is 51 MPa, which is three times greater than that of filtration-produced CNT buckypaper.


2. Florida State institute has been able to produce buckypaper with half the strength of the best existing composite material, known as IM7. Ben Wang expects to close the gap quickly.

"By the end of next year we should have a buckypaper composite as strong as IM7, and it's 35 percent lighter," Wang said.

Buckypaper now is being made only in the laboratory, but Florida State is in the early stages of spinning out a company to make commercial buckypaper.

One challenge is that the tubes clump together at odd angles, limiting their strength in buckypaper. Wang and his fellow researchers found a solution: Exposing the tubes to high magnetism causes most of them to line up in the same direction, increasing their collective strength.


[H/T to commenter eternal carrot for figures on IM7 material

IM7/8551-7A composite beams: The corresponding longitudinal modulus and failure loading were found to be 124.96 GPa and 782 MPa, respectively.

The loading thickness was 1.29mm, 2.80 mm and 1.83 mm for three samples. [not 0.1 mm or 100 microns for the North Carolina material.]


This air force PDF on page 19 describes IM7 carbon fiber as having the tensile strength of about 5520 MPa with a modulus of about 276 GPa.






3. Nanocomp Technologies, a startup, has also produced large sheets of carbon nanotubes.

Nanocomp Technologies received a $1.5 million development contract from the U.S. Army Natick Soldier Center in Massachusetts in August 2008.

FURTHER READING
Florida states High performance Material Institute website

Xiangwu Zhang's site at the University of North Carolina

Making aluminum cheaper and more energy efficient can also be a way to reduced the weight of cars. Expensive cars like the Jaguar, Aston Martin and Audi A-8 have aluminum frames and bodies which reduce vehicle weight by about 500 pounds.

Oak Ridge National Laboratory has empirically developed a rule of thumb that a 10 percent reduction in vehicle weight improves fuel economy by 5 to 7 percent.


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