For the first time, scientists have discovered that metal heals itself after fracture – an observation that could pave the way for creating self-repairing structures and robots.
But for those worried about Terminator Robot’s rise it’s a realistic don’t: This newly discovered mechanism only works on handfuls of minerals and on a very small scale—at least, for now.
“Certainly, there are many industries where product engineers are eager to translate these findings into a deliberate engineering approach to create self-healing metals automatically in our structural applications,” said the lead author. Brad BoyceA materials scientist at Sandia National Laboratory in Albuquerque, New Mexico, told Live Science. “Self-healing metals can be useful in a variety of applications from airplane wings to car suspension systems.”
Related: The real-life “Terminator 2” robot can melt to escape prison, then solidify on command
Scientists had previously assumed that metals could not repair themselves, but a new discovery, made by accident by scientists studying nanometer-sized pieces of platinum and copper, overturned that conclusion.
Metal is damaged by repeated pressure or motion, creating a growing network of microscopic cracks that can cause catastrophic failures in jet engines, bridges and other vital structures.
But not all materials break under repeated stress: even some modern polymer concrete from ancient Rome has been shown to repair microcracks over time.
In 2013, a team of researchers used computer models to show that minerals might also be able to perform healing tricks, but they couldn’t study minerals at the right scale and so they couldn’t get any concrete evidence.
In the new study, published July 19 in the journal Nature, using a device called a transmission electron microscope, scientists investigated how nano-sized pieces of metal respond to repeated pressure. The devices apply minuscule forces — equivalent to stepping on a mosquito’s toes — in the form of 200 tiny metal tugs every second.
in the two metals, copper and platinum, cracks appeared and grew throughout the material. But after 40 minutes, the metals fused together again, leaving no traces of cracks.
According to Boyce, the explanation for this miraculous self-repair lies in a process called “cold welding”.
“In short, at the nanoscale, local conditions around the edge of the crack cause the two sides of the crack to push against each other,” Boyce said. “Upon contact, the two sides are fused together in a process metallurgists call ‘cold welding’. This process does not appear to occur all the time, but only in cases where local conditions resulted in wing contact.”
The feasibility of the researchers’ new observations remains unknown. First, to observe the cold welding process, scientists isolate the metal in a vacuum so that no atomic atmosphere interferes with the equipment. That is, they do not yet know whether the process only works in a vacuum or not.
Similarly, the range of potential self-repairing metals is also unknown. Scientists have only observed cold welding on platinum and copper, but whether commonly used structural metals such as steel also do this is not clear.
There’s also the issue of size. The minerals used are small in size and very regular in structure; Nor is it known whether macrominerals can be coaxed into healing.
However, scientists are very optimistic that their discovery could lead to fundamental changes in the way we build and engineer metal structures for durability, and could have applications in space flight, where atmospheric particles are not an issue.
“In fact, we think this process may already be occurring to some extent even in the common metals and alloys we use in everyday life – at least for subsurface cracks that are not exposed to oxygen, and perhaps even for cracks on the surface,” said Boyce. “However, to get the most out of it, we can start thinking about the parts of the material and designing the microstructure.”
2023-07-21 18:54:29
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