Shock Synthesis of Decagonal Quasicrystals

J Oppenheim,C Ma,P D Asimow,P J Steinhardt,L Bindi,J Hu

doi:10.1038/s41598-017-15229-4

Abstract

The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al71Ni24Fe5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber. Abundant decagonal quasicrystals of average composition Al73Ni19Fe4Cu2Mg0.6Mo0.4Mn0.3 with traces of Si and Cr were found along the recovered interface between the Al and permalloy. The experiment also synthesized AlNiFe alloy with the B2 (CsCl-type) structure and the metastable Al9Ni2 phase. We present chemical (scanning electron microscopy and electron microprobe) and structural (electron backscatter diffraction and transmission electron microscopy) characterization of the recovered phases and discuss the implications of this shock synthesis for the stability of quasicrystals during high-pressure shocks and for the interpretation of the phase assemblage found in Khatyrka.

Highlights

Unlike periodic crystals, which have 1, 2, 3, 4, or 6-fold rotational symmetries, quasicrystals are aperiodic structures[1,2] that can exhibit previously forbidden rotational symmetries such as 5, 8, 10, and 12-fold
The target was impacted by a Ta flyer at 1041 ± 1 m/s and the chamber was recovered intact, sawn open, polished, and examined by scanning electron microscopy (SEM) in imaging, energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD) modes; by wavelength-dispersive electron probe microanalysis (EPMA); and by transmission electron
Microscopy (TEM) on a section extracted by Focused Ion Beam (FIB) milling, in bright-field imaging, scanning, EDS, and selected-area electron diffraction (SAED) modes

Summary

Introduction

Unlike periodic crystals, which have 1-, 2-, 3-, 4-, or 6-fold rotational symmetries, quasicrystals are aperiodic structures[1,2] that can exhibit previously forbidden rotational symmetries such as 5-, 8-, 10-, and 12-fold. We have experimentally confirmed this idea in previous reports of successful laboratory shock synthesis of icosahedral quasicrystals analogous to icosahedrite but with higher Al contents and five significant components (Al, Cu, Fe, Cr, Ni)[9,10]. We used an experimental technique similar to Asimow et al.[9] to try to synthesize decagonal quasicrystals (d-QC) similar to decagonite[6] in order to further confirm the hypothesis that natural quasicrystals in the Khatyrka meteorite are explained by shock processing of unusual metallic alloys during collisions in the asteroid belt. The target was impacted by a Ta flyer at 1041 ± 1 m/s and the chamber was recovered intact, sawn open, polished, and examined by scanning electron microscopy (SEM) in imaging, energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD) modes; by wavelength-dispersive electron probe microanalysis (EPMA); and by transmission electron www.nature.com/scientificreports/. Microscopy (TEM) on a section extracted by Focused Ion Beam (FIB) milling, in bright-field imaging, scanning, EDS, and selected-area electron diffraction (SAED) modes

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