The mechanical dynamics resulted from transformation reactions in solid state have an origin of the interface and volume change of grains down to atomic scale. Understanding how structural evolution and mechanics are related in this scale is of fundamental interest but they are often difficult to trace. In this work, we use <i>in-situ</i> transmission electron microscopy (TEM) to directly study the reduction transformation at AgCl-Ag nanoparticle interface. Three stages of AgCl lattice fluctuation: steady state, compression, and relaxation, are identified by Fourier Transform and are correlated to the structural evolution. A quasi-layered growth to both vertical and lateral directions is observed during steady state of AgCl lattices whereas their kinetics differ by two orders. Real-time imaging shows that nucleation and growth of silver at the interface happens simultaneously. We show that the development of planar defects is associated with lattice compression. Depletion of AgCl origins from the interfacial region and is associated with lattice relaxation of AgCl. Grain rotation and temperature effects on lattice fluctuation are found insignificant by TEM simulation and dynamic range analyses. To understand why positive strain and AgCl depletion does not commence in the first two stages, we trace the topography and structure of decomposing AgCl nanoparticles by <i>in-situ</i> scanning transmission electron microscopy (STEM). Silver species are suggested to originate from both surface and interior of the crystal, and then transport to the interface. Such mass transport may have enabled the steady state and compression of lattice in this volume-shrinking shear transformation.

Multi-stage transformation and lattice fluctuation at AgCl-Ag nanoparticle interface

253rd National Meeting (2017)

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