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Origin of Magnetism in Hydrothermally Aged 2-Line Ferrihydrite Suspensions

机译：水热老化两线铁水悬浮液的磁性起源

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摘要

As an iron oxyhydroxide, nanosized ferrihydrite (Fh) is important in Earth science, biology, and industrial applications. However, its basic structure and origin of its magnetism have long been debated. We integrate synchrotron-based techniques to explore the chemical structures of 2-line ferrihydrite and to determine the origin of its magnetism during hydrothermal aging in air. Our results demonstrate that both the magnetism and X-ray magnetic circular dichroism (XMCD) signal of 2-line ferrihydrite are enhanced with aging time, and that XMCD spectral patterns resemble that of maghemite (γ-Fe_20_3) rather than magnetite (Fe_30_4). Fe L-edge and K-edge X-ray absorption spectroscopy (XAS) further indicate formation of both maghemite and hematite (α-Fe_20_3) with increasing concentrations with longer hydrothermal aging time. Thus, magnetic enhancement with longer hydrothermal aging time is attributed to increasing maghemite concentration instead of a magnetically ordered ferrihydrite as previously reported. Moreover, L-edge and K-edge XAS spectra with different probing depths yield different ratios of these Fe oxides, which suggest the formation of a core (ferrihydrite-rich)-shell (with a mixture of both allotropes; α-Fe_20_3 and γ-Fe_20_3) structure during hydrothermal aging. Our results provide insights into the chemical evolution of 2-line ferrihydrite that reveal unambiguously the origin of its magnetism.
机译：作为羟基氧化铁，纳米亚铁酸盐（Fh）在地球科学，生物学和工业应用中很重要。但是，它的基本结构和磁性的起源早已受到争论。我们集成了基于同步加速器的技术，以探索2线亚铁水合物的化学结构，并确定其在空气中热液老化过程中的磁性起源。我们的结果表明，随着时间的推移，两线铁水铁矿的磁性和X射线磁性圆二色性（XMCD）信号均会增强，并且XMCD的光谱模式类似于磁铁矿（γ-Fe_20_3）而不是磁铁矿（Fe_30_4）。 Fe L边缘和K边缘X射线吸收光谱（XAS）进一步表明，随着水热老化时间的延长，磁赤铁矿和赤铁矿（α-Fe_20_3）的形成都随着浓度的增加而增加。因此，具有更长的水热老化时间的磁性增强归因于增加的磁赤铁矿浓度，而不是如先前报道的磁性有序的亚铁水合物。此外，具有不同探测深度的L边缘和K边缘XAS光谱产生的这些Fe氧化物的比率不同，这表明形成了核芯（富铁水铁矿）壳（两种同素异形体的混合物；α-Fe_20_3和γ -Fe_20_3）结构在水热老化过程中。我们的结果提供了对2线亚铁水合物化学演化的见解，清楚地揭示了其磁性的起源。

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  • 来源
    《Environmental Science & Technology》 |2017年第5期|2643-2651|共9页
  • 作者

    Liang Cao; Zhao-Xia Jiang; Yong-Hua Du; Xin-Mao Yin; Shi-Bo Xi; Wen Wen; Andrew P. Roberts; Andrew T. S. Wee; Yi-Min Xiong; Qing-Song Liu; Xing-Yu Gao;

  • 作者单位

    Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai, 201800, P. R. China ,High Magnetic Field Laboratory, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei, Anhui, 230031, P. R. China;

    State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beitucheng Western Road, Beijing, 100029, P. R. China;

    Institute of Chemical and Engineering Sciences, A*STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, 627833, Singapore;

    Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore ,SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China;

    Institute of Chemical and Engineering Sciences, A*STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, 627833, Singapore;

    Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai, 201800, P. R. China;

    Research School of Earth Sciences, The Australian National University, 142 Mills Road, Canberra, ACT 2601, Australia;

    Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore;

    High Magnetic Field Laboratory, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei, Anhui, 230031, P. R. China;

    Department of Marine Science and Engineering, Southern University of Science and Technology of China, Shenzhen, 518055, P. R. China ,Laboratory for Marine Geology, Qingdao National Oceanography Laboratory for Science and Technology, Qingdao, 266071, P. R. China;

    Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai, 201800, P. R. China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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