Interconnected nanocrystal networks are emerging as a new form of matter with the ability to host metastable crystal phases at ambient conditions. Solids from a collection of atoms can adopt various structural phases with respective physical and chemical properties, providing a foundation for materials discovery. At ambient temperature and pressure, however, a given atomic collection has one thermodynamically stable phase, and the rest can obtain metastability as kinetically trapped phases with positive, free energy above the equilibrium state.
Phase transformations in bulk solids exhibit complex kinetics involving different microscopic pathways occurring in parallel at various locations. On the other hand, nanocrystals behave as single structural domains under high pressures, so their phase transition kinetics are simple and highly reproducible. Despite advances in materials research, practical nanocrystal systems capable of hosting metastable high-energy phases at ambient conditions are scarce.
Researchers at the University of Florida have recently made a fundamental breakthrough in identifying how interconnected nanocrystal networks are a form of matter that can adopt metastable crystal phases at the ambient condition and have developed a generalizable method for making these metastable materials through synthetic interparticle sintering. Interparticle sintering is applicable for engineering kinetic barriers in the phase transition, producing ambient metastable rock-salt in a controllable manner. The resulting interconnected-nanocrystal networks are a new class of structural systems for hosting metastable high-energy phases at ambient conditions. These findings illustrate the general rules’ usefulness in transformation-barrier engineering in designing next-generation technological materials, including semiconductors, superconductors, and quantum materials.
Produces a new class of high-energy metastable nanocrystals with applications for developing semiconductors, multiferroic materials, magnets, nanograined ceramics, nanograined metal, and their alloys, nanostructured super hard materials, superconductors, and quantum materials
This synthetic interparticle sintering method develops metastable high-energy and high-pressure materials by engineering kinetic barriers in nanocrystal phase transitions. The transition barriers are engineered between two crystal phases by the control of interparticle sintering, tailoring the reversibility of solid-solid phase transition. The correct ratio of nanoparticle to ligand surface coverage and high-pressure processing produces ambient metastable rock-salt structure nanocrystals in a controlled manner. The rock-salt nanocrystals form interconnected nanocrystal networks, a new class of structural systems hosting metastable high-energy phases at ambient conditions.