June 13, 2013
New Technique Defies Laws of Physics, Causing Material To Expand Under Pressure
Rebekah Eliason for redOrbit.com - Your Universe Online
What happens when you squeeze something? It usually gets smaller, but not if you are at Argonne National Laboratory.
“It´s like squeezing a stone and forming a giant sponge,” said Karena Chapman, a chemist at the US Department of Energy laboratory. “Materials are supposed to become denser and more compact under pressure. We are seeing the exact opposite. The pressure-treated material has half the density of the original state. This is counterintuitive to the laws of physics.”
This behavior seemed so unlikely that Chapman and her colleagues repeated the experiment for several years with each experiment producing the same results. Finally, the sheer data essentially forced them to believe what seemed unbelievable and accept the somewhat confusing results.
“The bonds in the material completely rearrange,” Chapman said. “This just blows my mind.”
This new material will not only change physics textbooks, it will also double the amount of porous materials used for manufacturing, health care and environmental sustainability.
Porous materials have sponge-like holes that can be tailored to trap, filter and store specific types of molecules. Selecting for specific molecules allows scientists to design porous materials for use as water filters, chemical sensors and compressible storage for carbon dioxide sequestration of hydrogen fuel cells.
Adjusting the release rate of chemicals in porous materials allows for possible applications in drug release therapy and instigates chemical reactions used in producing anything from foods to plastics.
“This could not only open up new materials to being porous, but it could also give us access to new structures for selectability and new release rates,” said Peter Chupas, an Argonne chemist who helped discover the new materials.
Details of their research were published in the May 22 issue of the Journal of the American Chemical Society.
To produce these fascinating materials, scientists placed zinc cyanide in a Diamond Anvil Cell, a device that can simulate pressures almost as great as those at the center of the earth. Pressures of 0.9 to 1.8 gigapascals were applied, which are about 9,000 to 18,000 times greater than the atmospheric pressure at sea level. The amount of high pressure used for the experiments is within an economically reproducible range by manufacturers for bulk storage systems.
Different fluids were used around the material to create five new phases of material, two of which retained their properties at normal pressure. Unique porous properties were determined based on the type of fluid used. Hydrostatic pressure has never before been used to convert dense materials into novel porous materials.
“By applying pressure, we were able to transform a normally dense, nonporous material into a range of new porous materials that can hold twice as much stuff,” Chapman said. “This counterintuitive discovery will likely double the amount of available porous framework materials, which will greatly expand their use in pharmaceutical delivery, sequestration, material separation and catalysis.”
Similar research using this new technique continues with alternative materials.