Dr. Bradford Researches How Carbon Nanotubes Can Improve Textiles

bradford-lab

Written by: Caroline Ellington, ABM Textile Engineering Student

Dr. Philip Bradford, Assistant Professor in Textile Engineering, Chemistry, and Science (TECS), is no stranger to NC State or the Wilson College of Textiles. After graduating with his B.S. in Textile Engineering in 2005, Dr. Bradford went on to get Master of Science degrees in both Textile Engineering and Materials Science and Engineering in 2007. Three years later, in 2010, he earned his Ph.D. in Materials Science and Engineering. Dr. Bradford’s current research in carbon nanotubes spans these two disciplines.

Carbon nanotubes are nanofibers comprised only of carbon.  An analogy used to describe the chemical structure of a carbon nanotube is chicken wire fencing. The carbon bonds form a two dimensional sheet that is made up of a hexagonal pattern. A carbon nanotube’s structure looks very similar to the same chicken wire rolled up into a seamless tube.  Typically these fibers have lengths of only a fraction of the width of a human hair. In Dr. Bradford’s lab, carbon nanotubes are being produced with lengths on the order of millimeters instead of micrometers; creating a very large length-to-diameter ratio that allows for more possible processing routes and applications. Carbon nanotubes possess many properties which make them desirable for incorporating into textile applications such as composites; they are the strongest and stiffest known material structure and they are electrically and thermally conductive like metals. Dr. Bradford’s lab grows nanotubes in such a way that it is possible to draw them out into sheets and make them into a fabric, something that is relatively new to the research community.

The three major areas of research for Dr. Bradford’s research group are:  1) Air filtration utilizing carbon nanotube fabrics, 2) Carbon nanotube fabric lithium ion battery anodes, and 3) Carbon nanotube composites.

Air filtration utilizing carbon nanotube fabrics
Carbon nanotubes are a great candidate for fibers used in air filters. However, until now, processing them into a low density fabric has been a challenge. Dr. Bradford’s research group has produced carbon nanotube fabric air filters that could make for an exciting advancement in filtration technology, as they provide an excellent combination of high efficiency, low particle penetration and low pressure drop across the filter. The filtration properties are improved because the diameter of the carbon nanotubes in the carbon nanotube fabric is 5 to 25 times smaller than those fibers that are used in current textile nonwoven fabric air filters.

Carbon nanotube fabric lithium ion battery anodes
Dr. Bradford was awarded a grant from the American Chemical Society for his work on incorporating carbon nanotube fabrics into Lithium-Ion battery anodes; a project which he is working in conjunction with Dr. Xiangwu Zhang, also of the TECS department. Their goal is to create battery anodes with high capacity and good cycling stability. To do so, they coated the carbon nanotube fabrics with a nanoscale layer of silicon at high temperatures. The silicon helps add to the capacity of the anode and the carbon nanotubes act as an electrically conductive scaffold. Such anodes could have a positive impact on the functionality of current battery technologies.

Carbon nanotube composites
The Bradford group is also working on combining carbon nanotubes with other materials to produce high performance composites. These projects include: helping to strengthen and toughen traditional glass and carbon fiber composites; producing thermally conductive composites made of carbon nanotubes and copper; and composites made from carbon nanotubes and a carbon matrix. All of these projects aim to push the boundaries of traditional materials. The Air Force Office of Scientific Research sponsors Dr. Bradford’s research efforts in these areas.

Dr. Bradford’s extensive research in the world of carbon nanotubes, their fabrics and their composites makes his research group one of only a few of its kind in the world.

Learn more about Dr. Bradford’s research.