Cellule à enclumes de diamant

Résumé

right|300px|thumb|Schéma du principe d'une cellule à enclumes de diamant. La cellule à enclumes de diamant est un dispositif expérimental qui permet de soumettre un matériau à des pressions et températures très élevées et de réaliser de nombreuses mesures physiques dans ces conditions. Ses performances et sa relative facilité d'utilisation en ont fait un dispositif incontournable dans les études des comportements des matériaux sous hautes pressions. Elle est notamment très utilisée en géologie où les conditions existant dans le manteau terrestre peuvent être reproduites. Le terme se retrouve également écrit cellule à enclumes de diamants (en anglais : diamond anvil cell ou DAC) ou presse à enclumes de diamant également écrit presse à enclumes de diamants) Histoire du développement right|250px|thumb|Première cellule à enclumes de diamant exposée au musée du NIST de Gaithersburg. La DAC a été conçue aux États-Unis en 1958 et la technique de mesure de la pression par fl

Source officielle

https://fr.wikipedia.org/wiki/Cellule_%C3%A0_enclumes_de_diamant

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Strength and texture of Pt compressed to 63 GPa

Susannah McGregor Dorfman

Angle-and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63 GPa. Observed yield strength and texture depend on grain size. For samples with 70-300-nm particle size, the yield strength is 5-6 GPa at similar to 60 GPa. Coarse-grained (similar to 2-mu m particles) Pt has a much lower yield strength of 1-1.5 GPa at similar to 60 GPa. Face-centered cubic metals Pt and Au have lower strength to shear modulus ratio than body-centered cubic or hexagonal close-packed metals. While a 300-nm particle sample exhibits the < 110 > texture expected of face-centered-cubic metals under compression, smaller and larger particles show a weak mixed < 110 > and < 100 > texture under compression. Differences in texture development may also occur due to deviations from uniaxial stress under compression in the diamond anvil cell. (C) 2015 AIP Publishing LLC.

Amer Inst Physics2015

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Polycrystalline ruby (alpha-Al2O3:Cr3+), a widely used pressure calibrant in high-pressure experiments, was compressed to 68.1 GPa at room temperature under non-hydrostatic conditions in a diamond anvil cell. Angle-dispersive X-ray diffraction experiments in a radial geometry were conducted at beamline X17C of the National Synchrotron Light Source. The stress state of ruby at high pressure and room temperature was analyzed based on the measured lattice strain. The differential stress of ruby increases with pressure from similar to 3.4 % of the shear modulus at 18.5 GPa to similar to 6.5 % at 68.1 GPa. The polycrystalline ruby sample can support a maximum differential stress of similar to 16 GPa at 68.1 GPa under non-hydrostatic compression. The results of this study provide a better understanding of the mechanical properties of this important material for high-pressure science. From a synthesis of existing data for strong ceramic materials, we find that the high-pressure yield strength correlates well with the ambient pressure Vickers hardness.

Springer2014

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Natural and synthetic pyrope-almandine compositions from 38 to 100 mol% almandine (Alm38-Alm100) were studied by synchrotron X-ray diffraction in the laser-heated diamond anvil cell to 177 GPa. Single-phase orthorhombic GdFeO3-type perovskites were synthesized across the entire examined compositional range at deep lower mantle pressures, with higher Fe-contents requiring higher synthesis pressures. The formation of perovskite with Alm100 (Fe3Al2Si3O12) composition at 80 GPa marks the first observation of a silicate perovskite in a Fe end-member. Fe-enrichment broadens and lowers the pressure range of the post-perovskite transition for intermediate compositions such as Alm54, but the more Fe-rich Alm100-composition perovskite remains stable to pressures as high as 149 GPa. Volume compression data for the Alm54 and Alm100 compositions were fit to the Birch-Murnaghan equation of state. The compressibility of perovskites synthesized from compositions along the pyrope-almandine join is not strongly sensitive to Fe-content. The compression curves were smooth over the entire measured range, and no evidence for a volume anomaly associated with a spin transition was observed. (C) 2012 Elsevier B.V. All rights reserved.

Elsevier Science Bv2012

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