Nov. 15, 2019
When rapidly compressed to planetary-core pressures, lead — a soft metal — becomes 10 times stronger than high-grade steel.
Strength — the maximum stress a material can withstand before it fails or deforms — is a fundamental property of a material. Strength is typically measured under static conditions, but it can change significantly when a large stress is applied rapidly. Understanding this dynamic strength behavior would benefit applications ranging from the design of armory and bullet-proof vests to the development of fusion schemes based on the laser-driven compression of a fuel pellet.
Andrew Krygier of Lawrence Livermore National Laboratory and colleagues have performed dynamic strength measurements on lead (Pb) and on a series of Pb-based alloys at some of the highest pressures ever explored, about 400 GPa.
They found that the large pressure and rate of deformation, or strain, produce a remarkable “hardening” of Pb. This normally soft metal became 250 times stronger when compressed. This hardening is due to a mechanism that might be useful for tuning the properties of important industrial materials, like steel.
Lawrence Livermore chemist Dawn Shaughnessy knows a thing or two about heavy elements.
She’s been part of a team that discovered five heavy elements including element 116, Livermorium, which is named after the Laboratory.
In fact, she is pushing the limits of the periodic table. “Pushing these element discoveries is really pushing into the models of how matter is formed in the Big Bang,” she said. “How do we model matter and how do we model the formation of the universe?”
Studying the chemistry of these less-than-a-millisecond living elements could redefine how the periodic table is drawn out.
Lawrence Livermore scientists and collaborators have discovered that at thermodynamic conditions mimicking that of Earth’s core, argon can react with nickel, forming a stable Argon-Nickel (ArNi) compound.
Radioactive decay of 40potassium (K) present in the Earth’s core is one of the main sources of heat that is believed to be crucial for powering Earth’s geodynamo (a mechanism by which a celestial body such as Earth generates a magnetic field). However, the fate of argon produced during the decay of 40K is an open question. Noble gas elements (NGEs), such as argon, are considered the most chemically inert elements on the periodic table, showing very little reactivity with other elements at temperatures and pressures found on Earth’s surface. But in Earth’s core, the reaction of metals with NGEs turns out to be quite different.
“Although our recently published results highlight that a NGE, such as xenon, can react with metals at elevated thermodynamic conditions, previous theoretical studies suggested that argon is quite reluctant to react with metals, even at pressures above those found in Earth’s core,” said Elissaios Stavrou, a staff member in the Materials Science Division at LLNL.
To find out argon’s fate, the team decided to challenge previous theoretical predictions and studied the possible reactivity of nickel with argon. When a nickel-argon mixture was subjected to pressures greater than 1.5 million times Earth’s atmospheric (surface) pressure and temperatures above 2,000 Kelvin, X-ray diffraction measurements strongly indicated that a new compound was formed.
A special relationship between plants and fungi, which plays an important role in carbon storage in soil, has the potential to slow down climate change. However, the amount of carbon stored in soil is decreasing as a result of human activity.
Humans have altered 50 percent to 75 percent of the terrestrial ecosystems in the world, mostly transforming them into fields and pastures. This has drastically affected the distribution of the mycorrhiza symbiosis, a special symbiosis between fungi and plants. In this relationship, the fungi provide plants with nutrients, while the plants provide the fungi with carbon. Human influence also has greatly reduced vegetation featuring a particular variety of these fungi, ectomyccrhizal fungi. This special type of plant-fungal symbiosis is crucially important to the storage of carbon in the soil.
A Lawrence Livermore scientist in collaboration with researchers from the Leiden Institute of Environmental Sciences found that the loss of plants involved in this type of relationship has reduced the ability of human-transformed ecosystems to sequester carbon in soils.
Even if plant-fungi symbioses are lost, the study found that ecosystems including these types of vegetation still store 350 gigatons of carbon globally, compared to the just 29 gigatons stored in other types of vegetation.
SIGNAL is an interesting multiplayer game that tries to simulate decision-making in the high stakes scenario of nuclear war for research purposes.
The Project on Nuclear Gaming (PoNG) — helmed by a team of researchers from the University of California at Berkeley, Lawrence Livermore National Laboratory and Sandia National Laboratory — created an online multiplayer strategy game called SIGNAL, or Strategic Interaction Game between Nuclear Armed Lands.
SIGNAL is part video game, part experiment and part data collection tool. The hope is that, by observing people playing the game and collecting the data it generates, PoNG can learn about human decision-making during nuclear conflicts.