Metastable quasicrystal-induced nucleation in a bulk glass-forming liquid

Abstract

SignificanceA model alloy, Mg69Zn27Yb4, concurrently forms bulk metallic glass, metastable quasicrystals (QCs), and crystalline approximant phases from the melt. We demonstrate that a transient QC phase nucleates first from the melt and subsequently transforms into an equilibrium approximant phase. This nucleation path is likely to be a general mechanism in metastable QC-forming systems. We observed a metastable-to-stable phase transformation when we deployed fast differential scanning calorimetry using the experimental strategy of interrupted cooling after the onset of crystallization followed by heating at ultrafast rates to “up-quench” the previously frozen structure. This strategy can yield the discovery of hidden transient phases that are key to understanding the crystallization behavior in metallic systems, polymers, biological solutions, and pharmaceutical substances.

Multi‐Step Crystallization of Self‐Organized Spiral Eutectics

“…That is, the presence of such crystallographic defects causes the spiral growth form. While screw dislocation-driven growth has been reported in diverse areas of crystallization [37,[43][44][45][46] -and indeed extensions of the Burton-Cabrera-Frank [30] spiral growth model exist [47] our proposed mechanism on the role of "hidden" polytetrahedral phases in assisting heterogeneous nucleation supports and expands upon recent reports, [11,48] for instance, metastable quasicrystal-induced nucleation yielding grain-refined alloys, [49] among other two-step solidification pathways.…”

“…The centrality of crystallization phenomena in many scientific fields has spurred decades of research into this “secretive” process. By tuning the growth conditions, it is possible to steer the system down different kinetic pathways to produce transient or metastable states (e.g., polytetrahedral or disordered phases) on intermediate time–scales . In particular, non‐equilibrium routes to metastable states could unveil patterns not seen in equilibrium states.…”

“…By tuning the growth conditions, it is possible to steer the system down different kinetic pathways to produce transient or metastable states (e.g., polytetrahedral or disordered phases) on intermediate time-scales. [10,11] In particular, non-equilibrium routes to metastable states could unveil patterns not seen in equilibrium states. Thus, an understanding of crystallization phenomena is the key to lock into place materials with morphologies and/ or functionalities not present in equilibrium states.…”

Diffusion of Ellipsoids in Bacterial Suspensions

“…Particularly, such a method has been used to investigate unique features of active fluids-a novel class of nonequilibrium soft materials with examples across a wide range of biological and physical systems including flocking animals [2][3][4], vibrated granular beds [5], synthetic colloidal swimmers [6,7], and a self-propelled cytoskeleton [8,9]. The behavior of spherical tracers in active fluids is most clearly illustrated by the diffusion of colloidal spheres in suspensions of swimming microorganisms [10][11][12][13][14][15][16][17][18]. Because of the hydrodynamic and steric interactions [19][20][21][22][23], a colloidal particle immersed in a bath of microswimmers exhibits a super-diffusive behavior at short times and a dramatically enhanced translational diffusion at long times.…”

“…The enhanced diffusion of passive particles such as nutrient granules, dead bacterial bodies and extracellular products is of great biological importance, which maintains an active ecological balance [10], stimulates bio-mixing [17], and promotes intercellular signaling and metabolite transports [23]. However, few natural particles have the perfect spherical symmetry and usually possess more than translational degrees of freedom.…”