First synthesis of a unique icosahedral phase from the Khatyrka meteorite by shock-recovery experiment
First synthesis of a unique icosahedral phase from the Khatyrka meteorite by shock-recovery experiment
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DOI：
10.1107/s2052252520002729
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发表时间：
2020-05-01
期刊：
影响因子：
3.9
通讯作者：
Bindi, Luca
中科院分区：
文献类型：
--
作者：
Hu, Jinping;Asimow, Paul D.;Bindi, Luca
铝 - 铜 - 铁体系中的二十面体准晶（i相）因其完美的准晶结构以及在哈提尔卡陨石中的自然存在而备受关注。成分为Al62Cu31Fe7的天然准晶，被称为i相II，是独特的，因为它显著偏离i相的稳定区域，并且迄今为止尚未在实验室环境中合成。在冲击恢复实验中形成的合成i相为探索新准晶成分的稳定性提供了一种新策略，并证明了天然准晶的撞击起源。在这项研究中，一个铝 - 铜 - 钨梯度密度撞击器（GDI，最初制造为产生斜坡的撞击器，但在这里用作目标）圆盘受到冲击，以在含铁的304不锈钢靶室中对全范围的铝/铜起始比例进行取样。在回收样品的一个强烈变形区域，GDI和钢之间的反应产生了共存的Al61.5Cu30.3Fe6.8Cr1.4 i相II + 斯托珀矿（β，AlCu）+ 哈提尔矿（θ，Al2Cu）的组合，与陨石中的天然i相II组合完全匹配。在第二个实验中，GDI和钢之间的连续界面形成了另一种含铁更丰富的五元i相（Al68.6Fe14.5Cu11.2Cr4Ni1.8），以及斯托珀矿和霍利斯特矿（λ，Al13Fe4），这是相平衡时预期的组合。这项研究是首次在实验室中重现具有其天然组合的i相II。它表明，在20 GPa以上的冲击压力下，热力学稳定的二十面体石（Al63Cu24Fe13）的区域可能会分成两个不相连的区域，导致像哈提尔卡的情况那样，富铁和贫铁的i相共存。有鉴于此，冲击恢复实验确实提供了一种有效的方法来确定含准晶陨石所记录的撞击条件，并探索导致准晶形成的条件和机制。
Icosahedral quasicrystals (i-phases) in the Al-Cu-Fe system are of great interest because of their perfect quasicrystalline structure and natural occurrences in the Khatyrka meteorite. The natural quasicrystal of composition Al62Cu31Fe7, referred to as i-phase II, is unique because it deviates significantly from the stability field of i-phase and has not been synthesized in a laboratory setting to date. Synthetic i-phases formed in shock-recovery experiments present a novel strategy for exploring the stability of new quasicrystal compositions and prove the impact origin of natural quasicrystals. In this study, an Al-Cu-W graded density impactor (GDI, originally manufactured as a ramp-generating impactor but here used as a target) disk was shocked to sample a full range of Al/Cu starting ratios in an Fe-bearing 304 stainless-steel target chamber. In a strongly deformed region of the recovered sample, reactions between the GDI and the steel produced an assemblage of co-existing Al61.5Cu30.3Fe6.8Cr1.4 i-phase II + stolperite (beta, AlCu) + khatyrkite (theta, Al2Cu), an exact match to the natural i-phase II assemblage in the meteorite. In a second experiment, the continuous interface between the GDI and steel formed another more Fe-rich quinary i-phase (Al68.6Fe14.5Cu11.2Cr4Ni1.8), together with stolperite and hollisterite (lambda, Al13Fe4), which is the expected assemblage at phase equilibrium. This study is the first laboratory reproduction of i-phase II with its natural assemblage. It suggests that the field of thermodynamically stable icosahedrite (Al63Cu24Fe13) could separate into two disconnected fields under shock pressure above 20 GPa, leading to the co-existence of Fe-rich and Fe-poor i-phases like the case in Khatyrka. In light of this, shock-recovery experiments do indeed offer an efficient method of constraining the impact conditions recorded by quasicrystalbearing meteorite, and exploring formation conditions and mechanisms leading to quasicrystals.