Density measurements of iron alloys at high pressure

• Project/Area Number: 26800274
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Ehime University
• Principal Investigator: Kuwayama Yasuhiro 愛媛大学, 地球深部ダイナミクス研究センター, 助教 (00554015)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000); Fiscal Year 2016: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2015: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2014: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
• Keywords: 核 / 密度 / 状態方程式 / 鉄 / 地球中心核 / 液体鉄 / X線非弾性散乱 / X線回折 / 放射光

Outline of Final Research Achievements

I performed in-situ x-ray diffraction studies, inelastic X-ray scattering measurements on solid and liquid iron and iron alloys at high pressure and high temperature using a laser heated diamond anvil cell high pressure apparatus to determine the structure, density and sound velocity of these alloys. I also performed electrical and thermal conductivity of iron at high pressure and high temperature. The results on density and sound velocity measurements indicate the core density deficit (cdd), which is the perceived difference between the seismically-determined density of the outer core and the density of pure iron at core conditions, is about 8%. The obtained electrical resistivity of iron at high pressure and high temperature is lower than the expected values, implying that the high thermal conductivity of Earth’s core, suggesting rapid core cooling and a young inner core less than 0.7 billion years old.

Research Products

• [Journal Article] Melting relations in the MgO-MgSiO3 system up to 70 GPa. (2017)
  • Author(s): Ohnishi, S., Kuwayama, Y., Inoue, T.
  • Journal Title: Phys. Chem. Minerals Volume: 印刷中 Issue: 6 Pages: 445-453
  • DOI: 10.1007/s00269-017-0871-8
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Experimental determination of the electrical resistivity of iron at Earth’s core conditions (2016)
  • Author(s): Kenji Ohta, Yasuhiro Kuwayama, Kei Hirose, Katsuya Shimizu, Yasuo Ohishi
  • Journal Title: Nature Volume: 印刷中 Issue: 7605 Pages: 95-98
  • DOI: 10.1038/nature17957
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Carbon-depleted outer core revealed by sound velocity measurements of liquid iron–carbon alloy (2015)
  • Author(s): Nakajima, Y., Imada, S., Hirose, K., Komabayashi, T., Ozawa, H., Tateno, S., Tsutsui, S., Kuwayama, Y. and Baron, A.
  • Journal Title: Nature Commun. Volume: 6 Issue: 1 Pages: 8942-8942
  • DOI: 10.1038/ncomms9942
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] The structure of Fe-Si alloy in Earth’s inner core (2015)
  • Author(s): Shigehiko Tateno, Yasuhiro Kuwayama, Kei Hirose, Yasuo Ohishi
  • Journal Title: Earth and Planetary Science Letters Volume: 418 Pages: 11-19
  • DOI: 10.1016/j.epsl.2015.02.008
  • Peer Reviewed
• [Journal Article] Highly conductive iron-rich (Mg,Fe)O magnesiowustite and its stability in the Earth's lower mantle (2014)
  • Author(s): Ohta, K., Fujino, K., Kuwayama, Y., Kondo, T., Shimizu, K., Ohishi, Y
  • Journal Title: Journal of Geophysical Research : Solid Earth Volume: 119-6 Issue: 6 Pages: 4656-4665
  • DOI: 10.1002/2014jb010972
  • Peer Reviewed
• [Presentation] Sound velocity of liquid fe-si alloy under high pressures (2016)
  • Author(s): Nakajima, Y., Imada, S., Hirose, K., Kuwayama, Y., Shinmyo, R., Tateno, S., Tsutsui, S., Ushiyama, H. and Baron, A.
  • Organizer: Goldschmidt 2016
  • Place of Presentation: パシフィコ横浜（神奈川県横浜市）
  • Year and Date: 2016-06-26
  • Int'l Joint Research
• [Presentation] Melting relations in the MgO-MgSiO3 system and the effect of other elements in the lower mantle (2016)
  • Author(s): Ohnishi, S., Kuwayama, Y. and Inoue, T.
  • Organizer: Goldschmidt 2016
  • Place of Presentation: パシフィコ横浜（神奈川県横浜市）
  • Year and Date: 2016-06-26
  • Int'l Joint Research
• [Presentation] High-P, T elasticity ofon and some alloys (2016)
  • Author(s): Tsuchiya, T., Kuwayama, Y., Kawai, K. and Ishii, M.
  • Organizer: Goldschmidt 2016
  • Place of Presentation: パシフィコ横浜（神奈川県横浜市）
  • Year and Date: 2016-06-26
  • Int'l Joint Research
• [Presentation] Melting relations in the MgO-MgSiO3 system under the lower mantle condition using a CO2 laser heated diamond anvil cell (2016)
  • Author(s): 大西里佳，桑山靖弘，井上徹
  • Organizer: 日本地球惑星科学連合2016年大会
  • Place of Presentation: 幕張メッセ国際会議場（千葉県千葉市）
  • Year and Date: 2016-05-22
  • Int'l Joint Research
• [Presentation] 鉄と鉄‐炭素合金の高温高圧弾性特性 (2016)
  • Author(s): 土屋卓久，桑山靖弘，石井水晶，河合研志
  • Organizer: 日本地球惑星科学連合2016年大会
  • Place of Presentation: 幕張メッセ国際会議場（千葉県千葉市）
  • Year and Date: 2016-05-22
  • Int'l Joint Research
• [Presentation] CO2レーザー両側直接加熱ダイヤモンドアンビルセルを用いたMgO-MgSiO3系の溶解関係 (2015)
  • Author(s): 大西里佳，桑山靖弘，井上徹
  • Organizer: 第56回高圧討論会
  • Place of Presentation: JMSアステールプラザ（広島県・広島市）
  • Year and Date: 2015-11-10
• [Presentation] 地球コア条件における鉄の電気伝導度 (2014)
  • Author(s): 太田健二，桑山靖弘，廣瀬敬，清水克哉，大石泰生
  • Organizer: 第55回高圧討論会
  • Place of Presentation: 徳島大学（徳島県・徳島市）
  • Year and Date: 2014-11-22
• [Presentation] CO2レーザー両側加熱ダイヤモンドアンビルセルを用いたMgO-MgSiO3系の溶融実験 (2014)
  • Author(s): 大西里佳，木村友亮，桑山靖弘
  • Organizer: 日本地球惑星科学連合
  • Place of Presentation: パシフィコ横浜（神奈川県・横浜市）
  • Year and Date: 2014-05-02
• [Presentation] 地球中心核条件における純鉄の電気抵抗率 (2014)
  • Author(s): 太田健二，桑山靖弘，廣瀬敬，大石泰生
  • Organizer: 日本地球惑星科学連合
  • Place of Presentation: パシフィコ横浜（神奈川県・横浜市）
  • Year and Date: 2014-04-29