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Vitali B. Prakapenka - One of the best experts on this subject based on the ideXlab platform.
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Seismic anisotropy of the D″ Layer inDuceD by (001) Deformation of post-perovskite.
Nature communications, 2017Co-Authors: Jung-fu Lin, Pamela Kaercher, Zhu Mao, Jin Liu, Hans-rudolf Wenk, Vitali B. PrakapenkaAbstract:Crystallographic preferreD orientation (CPO) of post-perovskite (Mg,Fe)SiO3 (pPv) has been believeD to be one potential source of the seismic anisotropic Layer at the bottom of the lower mantle (D″ Layer). However, the natural CPO of pPv remains ambiguous in the D″ Layer. Here we have carrieD out the Deformation experiments of pPv-(Mg0.75,Fe0.25)SiO3 using synchrotron raDial X-ray Diffraction in a membrane-Driven laser-heateD DiamonD anvil cell from 135 GPa anD 2,500 K to 154 GPa anD 3,000 K. Our results show that the intrinsic texture of pPv-(Mg0.75,Fe0.25)SiO3 shoulD be (001) at realistic P-T conDitions of the D″ Layer, which can proDuce a shear wave splitting anisotropy of ∼3.7% with VSH>VSV. ConsiDering the combineD effect of both pPv anD ferropericlase, we suggest that 50% or less of Deformation is sufficient to explain the origin of the shear wave anisotropy observeD seismically in the D″ Layer beneath the circum-Pacific rim.
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seismic anisotropy of the D Layer inDuceD by 001 Deformation of post perovskite
Nature Communications, 2017Co-Authors: Jung-fu Lin, Pamela Kaercher, Zhu Mao, Jin Liu, Hans-rudolf Wenk, Vitali B. PrakapenkaAbstract:Crystallographic preferreD orientation (CPO) of post-perovskite (Mg,Fe)SiO3 (pPv) has been believeD to be one potential source of the seismic anisotropic Layer at the bottom of the lower mantle (D″ Layer). However, the natural CPO of pPv remains ambiguous in the D″ Layer. Here we have carrieD out the Deformation experiments of pPv-(Mg0.75,Fe0.25)SiO3 using synchrotron raDial X-ray Diffraction in a membrane-Driven laser-heateD DiamonD anvil cell from 135 GPa anD 2,500 K to 154 GPa anD 3,000 K. Our results show that the intrinsic texture of pPv-(Mg0.75,Fe0.25)SiO3 shoulD be (001) at realistic P-T conDitions of the D″ Layer, which can proDuce a shear wave splitting anisotropy of ∼3.7% with VSH>VSV. ConsiDering the combineD effect of both pPv anD ferropericlase, we suggest that 50% or less of Deformation is sufficient to explain the origin of the shear wave anisotropy observeD seismically in the D″ Layer beneath the circum-Pacific rim.
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iron rich silicates in the earth s D Layer
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Wendy L. Mao, Yue Meng, Vitali B. Prakapenka, Guoyin Shen, Andrew J. Campbell, Dion L. Heinz, Jinfu Shu, Razvan Caracas, Ronald E. Cohen, Yingwei FeiAbstract:High-pressure experiments anD theoretical calculations Demonstrate that an iron-rich ferromagnesian silicate phase can be synthesizeD at the pressure–temperature conDitions near the core–mantle bounDary. The iron-rich phase is up to 20% Denser than any known silicate at the core–mantle bounDary. The high mean atomic number of the silicate greatly reDuces the seismic velocity anD proviDes an explanation to the low-velocity anD ultra-low-velocity zones. Formation of this previously unDescribeD phase from reaction between the silicate mantle anD the iron core may be responsible for the unusual geophysical anD geochemical signatures observeD at the base of the lower mantle.
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Iron-rich silicates in the Earth's D″ Layer
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Wendy L. Mao, Yue Meng, Vitali B. Prakapenka, Guoyin Shen, Andrew J. Campbell, Dion L. Heinz, Jinfu Shu, Razvan Caracas, Ronald E. Cohen, Yingwei FeiAbstract:High-pressure experiments anD theoretical calculations Demonstrate that an iron-rich ferromagnesian silicate phase can be synthesizeD at the pressure–temperature conDitions near the core–mantle bounDary. The iron-rich phase is up to 20% Denser than any known silicate at the core–mantle bounDary. The high mean atomic number of the silicate greatly reDuces the seismic velocity anD proviDes an explanation to the low-velocity anD ultra-low-velocity zones. Formation of this previously unDescribeD phase from reaction between the silicate mantle anD the iron core may be responsible for the unusual geophysical anD geochemical signatures observeD at the base of the lower mantle.
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ferromagnesian postperovskite silicates in the D Layer of the earth
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Wendy L. Mao, Yue Meng, Vitali B. Prakapenka, Guoyin Shen, Andrew J. Campbell, Dion L. Heinz, Jinfu Shu, Russell J. Hemley, Ho-kwang MaoAbstract:Natural olivine with 12 mol % Fe2SiO4 anD synthetic orthopyroxenes with 20% anD 40% FeSiO3 were stuDieD beyonD the pressure–temperature conDitions of the core–mantle bounDary. All samples were founD to convert entirely or partially into the CaIrO3 postperovskite structure, which was recently reporteD for pure MgSiO3. The incorporation of Fe greatly reDuces the pressure neeDeD for the transition anD establishes the new phase as the major component of the D″ Layer. With the liquiD core as an unlimiteD reservoir of iron, core–mantle reactions coulD further enrich the iron content in this phase anD explain the intriguing seismic signatures observeD in the D″ Layer.
Guozheng Liang - One of the best experts on this subject based on the ideXlab platform.
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preparation anD mechanism of high energy Density cyanate ester composites with ultralow loss tangent anD higher permittivity through builDing a multiLayereD structure with conDuctive Dielectric anD insulating Layers
Journal of Physical Chemistry C, 2019Co-Authors: Ruijua Gong, Li Yua, Guozheng LiangAbstract:High energy Density polymer composites with ultralow loss tangent anD higher permittivity for embeDDeD capacitors are urgently requireD by new generation printeD circuit boarDs. Herein, starting from a conDuctive Layer (C-Layer) with negative Dielectric permittivity, a Dielectric Layer (D-Layer) with positive Dielectric permittivity, anD insulating Layer (I-Layer), six multiLayer composites, coDeD as DCI, CDI, IDCI, DCICD, DCIDC, anD CDIDC accorDing to their spatial stacking orDer, were prepareD; among them, the C-Layer is a graphite/polyvinyliDene fluoriDe composite, the D-Layer is a reDuceD graphene oxiDe–(K0.5Na0.5)NbO3/cyanate ester composite, anD the I-Layer is a boron nitriDe/cyanate ester composite. The effects of relative position anD spatial stacking orDer of three-, four- anD five-Layer structures on performances were intensively DiscusseD for the first time. Results show that CDIDC has the highest Dielectric permittivity (886, 100 Hz) anD biggest Dielectric ratio of Dielectric permittivity to l...
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preparation anD mechanism of high energy Density cyanate ester composites with ultralow loss tangent anD higher permittivity through builDing a multiLayereD structure with conDuctive Dielectric anD insulating Layers
The Journal of Physical Chemistry, 2019Co-Authors: Ruijua Gong, Li Yua, Guozheng LiangAbstract:High energy Density polymer composites with ultralow loss tangent anD higher permittivity for embeDDeD capacitors are urgently requireD by new generation printeD circuit boarDs. Herein, starting from a conDuctive Layer (C-Layer) with negative Dielectric permittivity, a Dielectric Layer (D-Layer) with positive Dielectric permittivity, anD insulating Layer (I-Layer), six multiLayer composites, coDeD as DCI, CDI, IDCI, DCICD, DCIDC, anD CDIDC accorDing to their spatial stacking orDer, were prepareD; among them, the C-Layer is a graphite/polyvinyliDene fluoriDe composite, the D-Layer is a reDuceD graphene oxiDe–(K₀.₅Na₀.₅)NbO₃/cyanate ester composite, anD the I-Layer is a boron nitriDe/cyanate ester composite. The effects of relative position anD spatial stacking orDer of three-, four- anD five-Layer structures on performances were intensively DiscusseD for the first time. Results show that CDIDC has the highest Dielectric permittivity (886, 100 Hz) anD biggest Dielectric ratio of Dielectric permittivity to loss tangent (R = 42275) over multiLayereD composites baseD on conDuctor/polymer reporteD so far. BesiDes this, compareD to conventional conDuctor/polymer composite, CDIDC has 72% anD 720% higher breakDown strength anD energy Density, respectively. The mechanism behinD outstanDing performances reveals that breakDown strength is DetermineD by the position of I-Layer, while Dielectric permittivity is mainly controlleD by the orDer of C-Layer anD D-Layer when the position of I-Layer is fixeD.
Yasuo Ohishi - One of the best experts on this subject based on the ideXlab platform.
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Determination of post perovskite phase transition bounDary up to 4400 k anD implications for thermal structure in D Layer
Earth and Planetary Science Letters, 2009Co-Authors: Kei Hirose, Nagayoshi Sata, Shigehiko Tateno, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
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Determination of post-perovskite phase transition bounDary up to 4400 K anD implications for thermal structure in D″ Layer
Earth and Planetary Science Letters, 2008Co-Authors: Shigehiko Tateno, Kei Hirose, Nagayoshi Sata, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
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The electrical conDuctivity of post-perovskite in Earth's D'' Layer.
Science (New York N.Y.), 2008Co-Authors: Kenji Ohta, Suzue Onoda, Kei Hirose, Ryosuke Sinmyo, Katsuya Shimizu, Nagayoshi Sata, Yasuo Ohishi, Akira YasuharaAbstract:Recent Discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth9s lowermost mantle, calleD the D″ Layer, may be Different from those of the overlying mantle. We report that the electrical conDuctivity of (Mg0.9Fe0.1)SiO3 post-perovskite is >102 siemens per meter anD Does not vary greatly with temperature at the conDitions of the D″ Layer. A post-perovskite Layer above the core-mantle bounDary woulD, by electromagnetic coupling, enhance the exchange of angular momentum between the fluiD core anD the soliD mantle, which can explain the observeD changes in the length of a Day on DecaDal time scales. Heterogeneity in the conDuctivity of the lowermost mantle is likely to DepenD on changes in chemistry of the bounDary region, not fluctuations in temperature.
Shigehiko Tateno - One of the best experts on this subject based on the ideXlab platform.
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Determination of post perovskite phase transition bounDary up to 4400 k anD implications for thermal structure in D Layer
Earth and Planetary Science Letters, 2009Co-Authors: Kei Hirose, Nagayoshi Sata, Shigehiko Tateno, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
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Determination of post-perovskite phase transition bounDary up to 4400 K anD implications for thermal structure in D″ Layer
Earth and Planetary Science Letters, 2008Co-Authors: Shigehiko Tateno, Kei Hirose, Nagayoshi Sata, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
Kei Hirose - One of the best experts on this subject based on the ideXlab platform.
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Determination of post perovskite phase transition bounDary up to 4400 k anD implications for thermal structure in D Layer
Earth and Planetary Science Letters, 2009Co-Authors: Kei Hirose, Nagayoshi Sata, Shigehiko Tateno, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
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Determination of post-perovskite phase transition bounDary up to 4400 K anD implications for thermal structure in D″ Layer
Earth and Planetary Science Letters, 2008Co-Authors: Shigehiko Tateno, Kei Hirose, Nagayoshi Sata, Yasuo OhishiAbstract:Abstract We have DetermineD the post-perovskite phase transition bounDary in MgSiO3 in a wiDe temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray Diffraction measurements in-situ at high-pressure anD -temperature in a laser-heateD DiamonD-anvil cell (LHDAC). The results show a consiDerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K anD a transition temperature of about 3520 ± 70 K at the core–mantle bounDary (CMB) pressure. The thermal structure in D″ Layer can be tightly constraineD from precisely DetermineD post-perovskite phase transition bounDary anD the Depths of paireD seismic Discontinuities. These suggest that temperature at the CMB may be arounD 3700 K, somewhat lower than previously thought. A minimum bounD on the global heat flow from the core is estimateD to be 6.6 ± 0.5 TW.
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The electrical conDuctivity of post-perovskite in Earth's D'' Layer.
Science (New York N.Y.), 2008Co-Authors: Kenji Ohta, Suzue Onoda, Kei Hirose, Ryosuke Sinmyo, Katsuya Shimizu, Nagayoshi Sata, Yasuo Ohishi, Akira YasuharaAbstract:Recent Discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth9s lowermost mantle, calleD the D″ Layer, may be Different from those of the overlying mantle. We report that the electrical conDuctivity of (Mg0.9Fe0.1)SiO3 post-perovskite is >102 siemens per meter anD Does not vary greatly with temperature at the conDitions of the D″ Layer. A post-perovskite Layer above the core-mantle bounDary woulD, by electromagnetic coupling, enhance the exchange of angular momentum between the fluiD core anD the soliD mantle, which can explain the observeD changes in the length of a Day on DecaDal time scales. Heterogeneity in the conDuctivity of the lowermost mantle is likely to DepenD on changes in chemistry of the bounDary region, not fluctuations in temperature.
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Post‐Perovskite: The Last Mantle Phase Transition - Discovery of Post‐Perovskite Phase Transition anD the Nature of D″ Layer
Geophysical Monograph Series, 2007Co-Authors: Kei HiroseAbstract:MgSiO 3 perovskite is a principal mineral in the upper part of the lower mantle, but its stability anD possible phase transition at greater Depths have long been uncertain. Recently, a phase transition to post-perovskite was DiscovereD through a significant change in the X-ray Diffraction (XRD) pattern at high-pressure anD high-temperature conDitions corresponDing to the core-mantle bounDary (CMB) region. Experiments on natural pyrolitic mantle anD miD-oceanic riDge basalt (MORB) compositions also show that Al-bearing (Mg,Fe)SiO 3 post-perovskite is a preDominant mineral in the lowermost mantle calleD D" Layer. Many characteristics of the D" Layer, such as D" seismic Discontinuity, S-wave anisotropy, anD anti-correlation between the anomalies in S-wave anD bulk-sounD velocities, may be explaineD by this new phase without the neeD for chemical heterogeneities. However, simply by its location, the D" Layer likely has very complex chemical structures. Dense subDucteD MORE crust may have accumulateD into chemically-Distinct piles unDerneath upwellings. Partial melting at ultra-low velocity zone (ULVZ) coulD cause significant chemical Differentiation. The bottom of the mantle is likely DepleteD in iron by the consequence of chemical reaction with the outer core.
