Mechanics and Physics of Nanomaterials

Investigation of Fundamental Mechanical Properties of Nano-sized Solids

Relevant Personnel: Adenike Giwa (Ph.D. student in Materials Science), Anthony Kwong (Ph.D. student in Materials Science), Mike Citrin (Ph.D. student in Materials Science), Max Lifson (Ph.D. student in Materials Science), Haolu (Jane) Zhang (Ph.D. student in Mechanical Civil Engineering), and Bryce Edwards (Ph.D. student in Materials Science).

In the last decade or so it was ubiquitously demonstrated that at the micron- and nano-scales, the sample size dramatically affects material strength, as revealed by room-temperature uniaxial compression and tension experiments, as well as atomistic and continuum simulations, on a wide range of single-crystalline metallic nano-pillars. These studies provide a powerful foundation for the fundamental deformation processes operating in materials with simple nanostructures (i.e. single crystalline metals); they are a far reach from representing real materials, whose microstructure is often complex, and contains boundaries and interfaces. Both homogeneous (grain boundaries, twin boundaries, etc.) and heterogeneous (i.e. phase boundaries, precipitate-matrix boundaries, free and passivated surfaces) interfaces in size-limited features are crucial elements in the structural reliability of most modern materials. Little work has been done on characterizing the combined effects of extrinsic (sample size) and intrinsic (microstructural features) dimensions on the mechanical response of materials.

Our research aims to identify and to quantify the particular roles that the characteristic intrinsic material length scale and the external critical dimensions play on the mechanical response of materials through in-situ uniaxial compression and tension experiments performed at different temperatures on a variety of complex materials: from metallic glasses to battery-relevant materials, high-entropy alloys (HEAs), shape memory materials, space-relevant materials, solid organics, and piezoelectric materials. We conduct nano-deformation experiments, either quasi-statically or dynamically, in-situ, using custom-built instruments comprised of a nanoindenter-like module inside of an SEM or a FIB chamber, which allow for simultaneous mechanical data collection and real-time observation of the deformation.

Specific projects include investigating mechanical response of nanomaterials at cryogenic temperatures (down to ~40K) and measuring strength, ductility, and damping in metallic glasses (MGs), high-entropy alloys (HEAs), and carbon-based organics at those temperatures; analyzing statistics of dislocation avalanches in nano- and micron-sized metals, determining storage and loss moduli in polymer resins, and conducting microstructural atomic-level analysis in the Transmission Electron Microscope (TEM).