In the current online edition of Physical Review Letters, researchers from the Carnegie Institution's Geophysical Laboratory report changes in the melting temperature of solid nitrogen at pressures up to 120 gigapascals (more than a million atmospheres) and temperatures reaching 2,500° Kelvin (more than 4000° Fahrenheit).
These results, plus observed changes in the structure of solid nitrogen at high pressures, could lead to new high energy nitrogen- or hydrogen-based fuels in the future. Hypothesized nitrogen polymers could form materials with higher energy content than any known non-nuclear material.
Alexander Goncharov, Viktor Struzhkin, and Russell Hemley from Carnegie, with Jonathan Crowhurst from Lawrence Livermore National Laboratory, compressed liquid nitrogen in a device known as a diamond anvil cell, which generates ultrahigh pressures by squeezing a sample between two gem-quality diamonds. Because the diamonds are transparent to most wavelengths of light, the sample can be heated by a laser during the experiment. A technique called Raman spectroscopy uses light emitted by the heated sample to analyze changes in the sample's molecular structure as they occur.
"Until now, no one had made these kinds of in situ observations of nitrogen at such extreme temperatures and pressures," says Goncharov. "Our measurements of the melting line and the vibration properties of the fluid indicated by the Raman spectroscopy give us a very clear picture of how nitrogen and its molecular bonds respond under these conditions."
A chart of the temperatures and pressures at which a substance changes from one phase to another (from liquid to gas, from one crystal structure to another, and so on) is called a phase diagram. For nitrogen, as well as most other materials, the high temperature and pressure regions of the phase diagram are relatively unexplored territories. Researchers hope that these unexplored regions may harbor new materials with useful properties.
At room temperature and atmospheric pressure, nitrogen is a gas, but it can be cooled and compressed to form a liquid or a solid, depending on the temperature and pressure. Even as it changes phases, however, the nitrogen remains a two atom (diatomic) molecule, held together by a strong—and energy rich—triple bond.
"Nitrogen compounds tend to be high energy density materials," says Goncharov. "Pure nitrogen can be a powerful fuel or explosive if one can figure out how to associate nitrogen atoms in a material other than as a triple-bonded diatomic molecule. Recent experiments have shown that nitrogen transforms to nonmolecular single-bonded phases at very high pressure. These could serve as high energy density materials if preserved on a return to ambient pressure. Our results will help show the way to synthesize these materials at less extreme conditions."
Filling the gaps in nitrogen's phase diagram has implications for the study of other critical materials, say Goncharov. "Nitrogen is an archetypal diatomic molecule. Knowledge of its phase diagram and other properties gives a hint about the behavior of other diatomics, among which is hydrogen. Many key transformations and other phenomena occur in nitrogen at much lower pressures than in hydrogen," he says. "Hydrogen is a fuel for the future. It is theorized to have fascinating properties under high pressure, including transformation to metallic, superconducting and superfluid states. Whether the materials with such properties can be recovered and stabilized at ambient pressure remains an open question. But with nitrogen, we are moving ahead quickly. "
Alexander Goncharov | EurekAlert!
APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie
First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science
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