UNC Scientists' Research Promises Improved X-Ray Machines Using Carbon Nanotubes

Experiments the team conducted have shown they can cause carbon nanotubes, a new form of carbon discovered about a decade ago, to generate intense electron beams that bombard a metal "target" to produce X-rays. Researchers say they have demonstrated that their cold-cathode device can generate sufficient X-ray flux to create images of extremities such as the human hand.

The advantage of using carbon nanotubes is that machines incorporating them can work at room temperature rather than the 1500 or so degrees Celsius that conventional X-ray machines now require and produce.

"If this works as well as we think it will, we can make such machines a lot smaller and cooler and be able to turn them on and off much faster," said Dr. Otto Z. Zhou, associate professor of physics and materials sciences. "Other advantages are that they should be cheaper, be safer in terms of the lower heat generated, last longer, use less electricity and produce higher resolution images.

"We believe we have made a major breakthrough in X-ray technology, and we are extremely excited about it."

A report on their experiments appears in the July 8 issue of Applied Physics Letters, a science and technology journal. Patents on the UNC work are pending.

Besides Zhou, authors are Dr. Guo Z. Yue, a former UNC faculty member now with United Solar Systems; Qi Oiu and Drs. Bo Gao and Hideo Shimoda of Applied Nanotechnologies Inc., students Yuan Cheng and Jian Zhang, and Dr. Jian Ping Lu, associate professor of physics and astronomy and applied and materials sciences. Dr. Sha Chang, associate professor of radiation oncology at the UNC School of Medicine, also participated in the project.

"Scientists and others, including the popular press, have shown a lot of interest in carbon nanotubes because of numerous potential applications," Zhou said. "They are very strong tubular structures formed from a single layer of carbon atoms and are only about a billionth of a meter in diameter."

In the past, UNC scientists and others have used carbon nanotubes to produce electrons, he said. What's new is that until now, no one could generate enough electrons to create distinct images like conventional X-rays do. Nanotubes replace traditional metal filaments that must be heated to high temperatures before being subjected to an electric field. The tubes shed electrons easily because, being so small, they ar