Phase transitions surround us--for instance, liquid water changes to ice when frozen and to steam when boiled. Now, researchers at the Carnegie Institution for Science* have discovered a new phenomenon of so-called metastability in a liquid phase. A metastable liquid is not quite stable. This state is common in supercooled liquids, which are liquids that cool below the freezing point without turning into a solid or a crystal. Now, scientists report the first experimental evidence of creating a metastable liquid directly by the opposite approach: melting a high-pressure solid crystal of the metal bismuth via a decompression process below its melting point.
The results, reported in the January 23, 2017, issue of Nature Communications, could be important for developing new materials and for understanding the dynamics of planetary interiors, such as earthquakes, because a metastable liquid could act as a lubricant strongly affecting the dynamics of the Earth's interior.
When a crystal structure of bismuth (right) is decompressed from 32,000 atmospheres (3.2 GPa) to 12,000 atmospheres (1.2 GPa) it melts into a liquid at about 23,000 atmospheres (2.3 GPa) (middle). It then recrystallizes at 12,000 atmospheres (left). The so-called metastable liquid produced by this decompression occurs in a pressure-temperature range similar to where the supercooled bismuth is produced. Supercooled liquids are cooled below the freezing point without turning into a solid or a crystal.
Credit: Chuanlong Lin and Guoyin Shen, Carnegie Institution
"Phase transitions come in two basic 'flavors,'" explained Carnegie co-author Guoyin Shen, director of the High-Pressure Collaborative Access Team at the Advanced Photon Source*. "In one type, the chemical bonds do not break as the material goes from one phase to another. But they do alter in orientation and length in an orderly manner.
The other, called reconstructive phase transition, is more chaotic, but the most prevalent in nature and the focus of this study. In these transitions, parts of the chemical bonds are broken and the structure changes significantly when it enters a new phase."
Pressure can be used to change the phase of a material in addition to heating and cooling. The scientists put a form of crystalline bismuth in a pressure-inducing diamond anvil cell, and subjected it to pressures and decompression ranging from 32,000 times atmospheric pressure (3.2 GPa) to 12,000 atmospheres (1.2 GPa) at a temperature of 420° F (489 K). Under decompression only, at about 23,000 atmospheres, bismuth melts into a liquid. Then at 12,000 atmospheres it recrystallizes.
"The richness in crystalline structure of bismuth is particularly useful for witnessing changes in the structure of a material," remarked lead author Chuanlong Lin.
The researchers imaged the changes using a technique called X-ray diffraction, which uses much higher energy X-rays than those we use for medical imaging and can therefore discern structure at the atomic level. They conducted five different compression/decompression rounds of experiments.
"The bismuth displayed a metastable liquid in the process of solid-solid phase transitions under decompression at about 23,000 to 15,000 atmospheres," Lin said.
The scientists also found that the metastable state can endure for hours below the melting point under static conditions. Interestingly, the metastable liquid produced by decompression occurred in a pressure-temperature range that is similar to where supercooled bismuth is produced.
"Because reconstructive phase transitions are the most fundamental type, this research provides a brand new way for understanding how different materials change," Shen said. "It's possible that other materials could display a similar metastable liquid when they undergo reconstructive transitions and that this phenomenon is more prevalent than we thought. The results will no doubt lead to countless surprises in both materials science and planetary science in the coming years."
*Authors on the paper are from Carnegie's Geophysical Laboratory, High-Pressure Collaborative Access Team at Argonne National Laboratory: Chuanlong Lin, Jesse Smith, Stanislav Sinogeikin, Yoshio Kono, Changyong Park, Curtis Kenney-Benson, and Guoyin Shen. The work was performed at the Carnegie Institution for Science and Argonne National Laboratory, and is supported by the DOE/BES X-ray Scattering Program. HPCAT operation is supported by DOE-NNSA. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Guoyin Shen | EurekAlert!
Electron tomography technique leads to 3-D reconstructions at the nanoscale
24.05.2018 | The Optical Society
These could revolutionize the world
24.05.2018 | Vanderbilt University
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences