Scientists at the Swiss Federal Laboratories for Materials Science and Technology in Zurich, Switzerland, have built a functional X-ray tube using carbon nanotubes as electron sources. Carbon nanotube electron field-emission is well known effect and has been studied since the mid 1990s. Since then, several X-ray sources have been described in the scientific and technical literature.
This work is unique in that a commercial X-ray tube was modified to accommodate a carbon nanotube cathode instead of a classical thermionic emitter, and this, with limited modification to the tube design and production method. The nanotube cathodes were fabricated by screen-printing on molybdenum a carbon-silicate composite paste which contains multiwall carbon nanotubes. Moreover, the cathodes are temperature-resistant and survive downstream fabrication steps such as high temperature brazing of the X-ray tube body. Full details on this technology and the paste material can be found in the Journal of Materials Chemistry C of the Royal Society of Chemistry (RSC).