Salt block unexpectedly stretches in new experiments

Jun 24, 2009
Sandia-developed interfacial force microscope tip unexpectedly creates a tendril from a block of salt as the tip retreats from the salt surface. The picture was taken by a transmission electron microscope at the Sandia/Los Alamos Center for Integrated Nanotechnologies. Credit: Jianyu Huang

To stretch a supply of salt generally means using it sparingly.

But researchers from Sandia National Laboratories and the University of Pittsburgh were startled when they found they had made the solid actually physically stretch.

"It's not supposed to do that," said Sandia principal investigator Jack Houston. "Unlike, say, gold, which is ductile and deforms under pressure, salt is brittle. Hit it with a hammer, it shatters like glass."

That a block of salt can stretch rather than remain inert might affect world desalination efforts, which involve choosing particular sizes of nanometer-diameter pores to strain salts from brackish water. Understanding unexpected salt also may lead to better understanding of sea salt aerosols, implicated in problems as broad as cloud nucleation, smog formation, ozone destruction and asthma triggers, the researchers write in their paper published in the May Nanoletters.

Sandia researchers Jack Houston (left) and Nathan Moore examine a tiny salt block while the screen behinds them shows the magnified tip of the Sandia-developed interfacial force microscope (device in the foreground) performing another materials interrogation. The device was developed by Houston. Credit: Sandia National Laboratories

The serendipitous discovery came about as researchers were examining the of salt in the absence of water. They found unexpectedly that the brittle substance appeared malleable enough to distort over surprisingly long distances by clinging to a special microscope's nanometer-sized tip as it left the surface of the salt.

More intense examination showed that surface salt molecules formed a kind of bubble — a ductile meniscus — with the exploratory tip as it withdrew from penetrating the cube. In this, it resembled the behavior of the surface of water when an object is withdrawn from it. But unlike water, the salt meniscus didn't break from its own weight as the tip was withdrawn. Instead it followed the tip along, slip-sliding away (so to speak) as it thinned and elongated from 580 (nm) to 2,191 nm in shapes that resembled nanowires.

A possible explanation for salt molecules peeling off the salt block, said Houston, is that "surface molecules don't have buddies." That is, because there's no atomic lattice above them, they're more mobile than the internal body of salt molecules forming the salt block.

Salt showing signs of surface mobility at room temperatures was "totally surprising," said Houston, who had initially intended to study more conventionally interesting characteristics of the one-fourth-inch square, one-eighth-inch-long block.

Source: Sandia National Laboratories (news : web)

Explore further: Thinnest feasible nano-membrane produced

add to favorites email to friend print save as pdf

Related Stories

Salt production started in ancient China

Aug 23, 2005

A Harvard University study reports large-scale salt production occurred in inland China more than 2,000 years ago, the earliest date yet uncovered.

Salt-tolerant gene found in simple plant nothing to sneeze at

Apr 07, 2008

Whether a plant withers unproductively or thrives in salty conditions may now be better understood by biologists. The cellular mechanism that controls salt tolerance has been found in the arabidopsis plant by a Texas AgriLife ...

Aussies need more iodine

Aug 19, 2006

Health experts say a serious deficiency of iodine is emerging among people living in Australia's eastern states.

Recommended for you

Thinnest feasible nano-membrane produced

Apr 17, 2014

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

Nik_2213
2.5 / 5 (2) Jun 24, 2009
Haven't they heard of Salt Domes ??
http://en.wikiped...alt_dome
YawningDog
2.3 / 5 (3) Jun 24, 2009
Methinks yon knave doeth make a cogent point about the wise and noble craft of alchemy.
NeilFarbstein
1 / 5 (2) Jun 24, 2009
what's a salt gnome?
midget wrestling/
CTYankee
not rated yet Jun 25, 2009
"There is no such thing as a solid." It's like the cosmologists definition or all ordinary matter in the universe: "Hydrogen, Helium, metals; period."

I think the key was that the salt was dry. Molecular water in ionic solids, just like carbon in steel hardens the matrix. Water is ubiquitous so we take it for granted.

P.S. Why are the pictures always of a seasoned old researcher and a wet-behind-the-ears grad student contemplating an apparatus? ;^)

More news stories

'Exotic' material is like a switch when super thin

(Phys.org) —Ever-shrinking electronic devices could get down to atomic dimensions with the help of transition metal oxides, a class of materials that seems to have it all: superconductivity, magnetoresistance ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...