Researchers in New Mexico are reporting the surprise discovery that common table salt - so brittle that it crushes easily between a thumb and forefinger - becomes a super plastic in the weird environs of the nanoworld. The super-elastic salt can stretch like taffy to twice its original length without breaking. The discovery could lead to new insights into the role of salt in a wide variety of situations ranging from helping clouds to form to triggering asthmatic attacks in people, they say. Their study is in the current issue of ACS' Nano Letters, a monthly journal.
Nano-sized particles of salt can be stretched like taffy, researchers report. The study could lead to new insights into the role of salt in various health and environmental processes, they say. Credit: The American Chemical Society
Nathan Moore and colleagues note in the new study that researchers have known for years that metals like gold, lead and aluminum can be pulled into nanowires 1/50,000th the width of a human hair. Like other materials of such tiny dimensions, their properties change. Materials that conduct electricity poorly, for instance, become good conductors and materials that break easily develop new strength. That's why nanomaterials may form the basis of futuristic technologies that spawn new industries. But until now, no one expected to create nanowires from crystals of common table salt, or sodium chloride, which crumbles so easily.
The scientists made the unusual discovery while studying how water coats salt crystals using a microscope specially designed to observe mechanical and adhesive forces. They detected an unusual attractive force between the diamond tip of the microscope and the salt surface. After a series of tests, the researchers showed that the force encountered may have been caused by the presence of salt nanowires. In a similar test, they were able to capture images of salt nanowires being formed and stretched. The finding is "a striking and unexpected example of how material properties can change when viewed at the nanoscale," the article states.