Scientists squeezed the iron to the shape we believe it takes deep within the Earth’s core using an anvil made from diamond.
It is called Hexaferrum, or epsilon iron (ϵ-Fe), and it’s only stable at extremely high pressures. Scientists believe that the majority of iron in Earth’s center takes this form. A detailed understanding of it could help us to understand why the very core of our planet appears to have directional properties. The texture of the skin can vary. – a property known as anisotropy.
This quest to understand Earth’s core has one major problem. Conditions in the core can be difficult to reproduce on the surface in an atmospheric pressure regime that is relatively low. We can, however, create high pressure conditions using diamond anvils.
“We report here the synthesis of ϵ-Fe single crystals in diamond anvil cells and subsequent measurement of single-crystal elastic constants of this phase up to 32 GPa at 300 Kelvin with inelastic X-ray scattering,” write a team led by physicist Agnès DewaeleUniversity of Paris-Saclay, France
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The challenge lay in the conversion of the atmospheric-pressure phase of iron, called Ferrit, or alpha-iron. When high pressures are applied to ferrite to try to crush it to hexaferrum the ferrite breaks into tiny crystals which make it impossible to analyse in depth. This frustrates attempts to study its elastic property.
Dewaele, along with her colleagues, approached the problem in a step-by-step manner. The crystals were placed in a diamond nip in a vacuum heating system. They increased the temperature and pressure to 800 Kelvin (or 527 degrees Celsius or 980 Fahrenheit) while increasing the pressure up to 7 gigapascals.
The iron produced in this process is called austeniteAustenite is a different material than ferrite. The austenite crystals the team made changed to hexaferrum much more easily at pressures ranging between 15 and 32 gigapascals, 300 Kelvin. Austenite is a different material than ferrite. The austenite crystals that the team produced changed to the hexaferrum stage much more easily at pressures ranging between 15 and 32 gigapascals and 300 Kelvin.
They then used a beamline synchrotron at the European Synchrotron Radiation Facility (ESRF) to probe and analyze the hexaferrum.
The seismic data we have collected has helped us to reconstruct a lot of what we think about Earth’s interior. The acoustic waves produced by planetary tremors travel differently in different materials. How we knowEarth’s core is The jawbreaker is layered.
To gain a better understanding of the core, we must know the actual material and its response to acoustic wave. Dewaele’s team demonstrated that hexaferrum is directionally-dependent in terms of its elasticity. Waves propagate faster along a particular axis.
The anisotropy of hexaferrum is also observed during pressure changes. This suggests that hexaferrum will behave in a similar way. Up to 360 gigapascalEnvironment of the inner core. This is in line with observations made by How seismic waves travel around the planet.
The team’s methods could prove to be a great tool for understanding extreme conditions Our world at the centre.
The research was published in Physical Review Letters.
