Shock synthesis of quasicrystals with implications for their origin in asteroid collisions
Shock synthesis of quasicrystals with implications for their origin in asteroid collisions
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DOI：
10.1073/pnas.1600321113
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发表时间：
2016-06-28
影响因子：
11.1
通讯作者：
Steinhardt, Paul J.
中科院分区：
文献类型：
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作者：
Asimow, Paul D.;Lin, Chaney;Steinhardt, Paul J.
我们设计了板块冲击冲击恢复实验，以模拟与哈蒂尔卡陨石中唯一已知的天然准晶体相关的起始材料和冲击条件。在 CuAl5、(Mg0.75Fe0.252+)(2)SiO4 橄榄石和不锈钢室壁之间的边界处，回收的样品包含许多微米级的准晶相晶粒，表现出面心二十面体对称性和低相子应变。二十面体相的成分范围是 Al68-73Fe11-16Cu10-12Cr1-4Ni1-2，并且比报道的天然二十面体或任何先前已知的 Al-Cu-Fe 系统中的合成准晶体的 Al/(Cu+Fe) 和 Fe/Cu 比率更高。本实验中演示的冲击诱导合成强化了天然准晶体在冲击事件期间形成的证据，但仍存在这样的问题：该合成途径是否归因于高压下准晶相热力学稳定性范围的扩大，归因于冲击条件下存在的有利动力学途径，还是归因于热力学和动力学因素。
We designed a plate impact shock recovery experiment to simulate the starting materials and shock conditions associated with the only known natural quasicrystals, in the Khatyrka meteorite. At the boundaries among CuAl5, (Mg0.75Fe0.252+)(2)SiO4 olivine, and the stainless steel chamber walls, the recovered specimen contains numerous micron-scale grains of a quasicrystalline phase displaying face-centered icosahedral symmetry and low phason strain. The compositional range of the icosahedral phase is Al68-73Fe11-16Cu10-12Cr1-4Ni1-2 and extends toward higher Al/(Cu+Fe) and Fe/Cu ratios than those reported for natural icosahedrite or for any previously known synthetic quasicrystal in the Al-Cu-Fe system. The shock-induced synthesis demonstrated in this experiment reinforces the evidence that natural quasicrystals formed during a shock event but leaves open the question of whether this synthesis pathway is attributable to the expanded thermodynamic stability range of the quasicrystalline phase at high pressure, to a favorable kinetic pathway that exists under shock conditions, or to both thermodynamic and kinetic factors.