Detecting tiny defects

Citation

(2001), "Detecting tiny defects", Aircraft Engineering and Aerospace Technology, Vol. 73 No. 1. https://doi.org/10.1108/aeat.2001.12773aab.013

Detecting tiny defects

Detecting tiny defects

Keywords: Defects, Measurement

Small defects in the surface of common materials – from silicon to steel – determine the properties of a material and how it can be used. Many of the pores, called vacancies, are so tiny that they cannot accurately be measured.

In the past, measurement of vacancies has limited the development of new or improved materials such as the new generation of electronic and optical devices. This especially has been significant when the vacancies are in devices that are only a few nanometers (1 millionth of 1mm) in size.

An international team of researchers working at the US Department of Energy's Oak Ridge National Laboratory (ORNL) (Oak Ridge, Tennessee) successfully applied the use of positrons, or anti-electrons to defects. The team conducted an experiment using positrons to find clusters of four atomic vacancies at the surface of gold nanoparticles embedded in a magnesia matrix. These clusters of vacancies, report the researchers, explain changes in the optical properties when the materials are subjected to different fabrication processes.

The research team generate positrons by smashing gamma rays against a tungsten target at ORNL's electron linear accelerator. The gamma rays are divided into negatively charged electrons and their anti-matter positrons. The positrons then were injected into the gold nanoparticles, where researchers using advanced spectroscopy were able to determine the size, location and concentration of the vacancy clusters.

Possible future applications of this work include less brittle ceramic materials, improved fibre composite materials and the ability to manipulate properties of optical devices.