Multi‐step crystallization of self‐organized spiral eutectics

January 23, 2020

Saman Moniri (1), Hrishikesh Bale (2), Tobias Volkenandt (3), Yeqing Wang (4), Jianrong Gao (4), Tianxiang Lu (5), Kai Sun (5), Robert O. Ritchie (5), Ashwin J. Shahani (5)
Small, 16, Issue 8, January 2020. DOI: 10.1002/smll.201906146


spiral eutectics, self‐organization, crystallization, chirality, cracks


A method for the solidification of metallic alloys involving spiral self‐organization is presented as a new strategy for producing large‐area chiral patterns with emergent structural and optical properties, with attention to the underlying mechanism and dynamics. This study reports the discovery of a new growth mode for metastable, two‐phase spiral patterns from a liquid metal. Crystallization proceeds via a non‐classical, two‐step pathway consisting of the initial formation of a polytetrahedral seed crystal, followed by ordering of two solid phases that nucleate heterogeneously on the seed and grow in a strongly coupled fashion. Crystallographic defects within the seed provide a template for spiral self‐organization. These observations demonstrate the ubiquity of defect‐mediated growth in multi‐phase materials and establish a pathway toward bottom‐up synthesis of chiral materials with an inter‐phase spacing comparable to the wavelength of infrared light. Given that liquids often possess polytetrahedral short‐range order, our results are applicable to many systems undergoing multi‐step crystallization.

How Our Software Was Used

Dragonfly was used to render and analyze the 3D reconstructed slices of spiral eutectics.

Author Affiliation

(1) Department of Chemical Engineering University of Michigan Ann Arbor, MI 48109, USA.
(2) Carl Zeiss Microscopy Inc. Pleasanton, CA 94588, USA.
(3) Carl Zeiss Microscopy GmbH Oberkochen 73447, Germany.
(4) Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education) Northeastern University Shenyang 110819, China.
(5) Department of Materials Science & Engineering University of Michigan Ann Arbor, MI 48109, USA.
(6) Department of Materials Science and Engineering University of California Berkeley, CA 94720, USA.