Superstrong silver may herald new era for metals

Studies of the nanoscale behaviour of silver led to the creation of a type of the metal 42 per cent stronger than any previously recorded, but which retained all of the electrical conductivity of softer types of silver which, according to project coleader Frederic Sansoz, a materials scientist and mechanical engineer from the University of Vermont, could lead to advances in applications from aerospace to energy.

The key to the discovery, a collaboration between Vermont and the Lawrence Livermore National Laboratory, was the defects which naturally occur in every metal, caused by imperfect formation of the geometrical lattice of atoms that form the material. Sometimes these defects lead to unwanted properties, such as brittleness or softening. Sansoz and Lawrence Livermore lead scientist Morris Wang were attempting to solve a problem which has dogged material scientists: whenever an alloy is made to overcome one of these unwanted properties, the electrical conductivity drops.

In a paper in Nature Materials, Sansoz and Wang describe how they doped silver with a small percentage of copper to control the behaviour of defects in the silver lattice. Only a trace amount of copper was required – less than one per cent by weight – but this produced a marked improvement in conductivity. The copper impurity turned two types of inherent nanoscale defect in the silver into a much stronger internal structure, the team explained.