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- Dubrovinsky, L. S., et al.
(författare)
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Materials science - The hardest known oxide
- 2001
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 410:6829, s. 653-654
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Dubrovinsky, L., et al.
(författare)
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Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle
- 2003
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 422:6927, s. 58-61
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Tidskriftsartikel (refereegranskat)abstract
- The boundary between the Earth's metallic core and its silicate mantle is characterized by strong lateral heterogeneity and sharp changes in density, seismic wave velocities, electrical conductivity and chemical composition(1-7). To investigate the composition and properties of the lowermost mantle, an understanding of the chemical reactions that take place between liquid iron and the complex Mg-Fe-Si-Al-oxides of the Earth's lower mantle is first required(8-15). Here we present a study of the interaction between iron and silica (SiO2) in electrically and laser-heated diamond anvil cells. In a multianvil apparatus at pressures up to 140 GPa and temperatures over 3,800 K we simulate conditions down to the core-mantle boundary. At high temperature and pressures below 40 GPa, iron and silica react to form iron oxide and an iron-silicon alloy, with up to 5 wt% silicon. At pressures of 85-140 GPa, however, iron and SiO2 do not react and iron-silicon alloys dissociate into almost pure iron and a CsCl-structured (B2) FeSi compound. Our experiments suggest that a metallic silicon-rich B2 phase, produced at the core-mantle boundary (owing to reactions between iron and silicate(2,9,10,13)), could accumulate at the boundary between the mantle and core and explain the anomalously high electrical conductivity of this region(6).
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| 9. |
- Dubrovinsky, L, et al.
(författare)
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Pressure-induced invar effect in Fe-Ni alloys
- 2001
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Ingår i: PHYSICAL REVIEW LETTERS. - 0031-9007. ; 86:21, s. 4851-4854
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the pressure-volume (P-V) relations for cubic iron-nickel alloys for three different compositions: Fe0.64Ni0.36, Fe0.55Ni0.45, and Fe0.20Ni0.80. It is observed that for a certain pressure range the bulk modulus does not change or can even
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| 11. |
- Dubrovinsky, L, et al.
(författare)
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Stability of (Mg0.5Fe0.5)O and (Mg0.8Fe0.2)O magnesiowustites in the lower mantle
- 2001
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Ingår i: EUROPEAN JOURNAL OF MINERALOGY. - : E SCHWEIZERBARTSCHE VERLAGS. - 0935-1221. ; 13:5, s. 857-861
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Tidskriftsartikel (refereegranskat)abstract
- We have heated magnesiowtistites (Mg0.5Fe0.5)O and (Mg0.8Fe0.2)O to temperatures of over 1000 K at pressures of over 80 GPa simulating the stability of the solid solution at physical conditions relevant to the Earth's lower mantle. The X-ray study of the
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- Mattesini, M., et al.
(författare)
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Cubic TiO2 as a potential light absorber in solar-energy conversion
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:11
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Tidskriftsartikel (refereegranskat)abstract
- Materials are currently sought for use in the photo-induced decomposition of water on crystalline electrodes. Titanium dioxide is valuable in this respect. The electronic structural properties of cubic TiO2 polymorphs were investigated by means of first-principles methods. We demonstrate that both fluorite- and pyrite-type TiO2 have important optical absorptive transitions in the region of the visible light. A cubic TiO2 phase that can efficiently absorb the sunlight would be an important candidate material for the development of the solar cells. Also, we present results on the Ti L edges for the two different titania forms. We predict that a qualitative spectroscopic discrimination of the cubic polymorphs can be achieved by following the Ti 2p → 3d x-ray transitions.
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