WEB Engineering Far-From-Equilibrium Materials Using Electromagnetic FieldsWednesday (01.01.2020) 00:00 - 00:30 Part of:
Electromagnetic (EM) fields absorbed within a material can promote far-from-equilibrium chemical reactions and/or structural transformations. Here we define far-from-equilibrium as a type of dynamic equilibrium in which mass, charge transport, and resultant structure of a material at multiple length-scales is changing under EM excitation. Low temperature crystallization and sintering of materials such as ceramics, induced by both microwave radiation in the 0.3-300 GHz frequency range and lasers in the mid infrared range are two examples of such transformations. Other examples include field-assisted ionic diffusion, sintering, and phase transformations such as spinodal decomposition of solid solutions. What is common to these examples is the idea that the EM fields absorbed within a material may not be immediately converted to heat, but can instead result in field-driven “non-thermal” effects. In some cases, even new behavior evolves such as ceramics that are ductile and can be drawn into wires that survive high temperatures and other extreme environments that metals cannot. However, the underlying fundamental mechanisms behind these observations remain largely unknown.
This talk will describe my lab’s efforts to merge exploratory experiments and computation with data-driven methods to define new thermodynamic foundations that better explain the behavior of groups of atoms under externally applied fields. We used high-resolution synchrotron x-ray studies to demonstrate the first experimental evidence that 2.45 GHz microwave fields stabilize a different atomic structural arrangements or phase(s) in ceramics like TiO2, compared to conventional, high temperature furnace based synthesis. Through a combination of in-situ and ex-situ characterization, as well as molecular dynamics simulations, we show that externally applied fields can induce far-from-equilibrium phases in ceramics via a defect-mediated, field-driven, non-thermal effect. Our work thus lays the theoretical foundations for deploying electromagnetic fields as a new processing tool to access high temperature ceramic phases with minimal thermal input; allowing us to explore regions of phase space, microstructures, and properties not accessible via conventional synthesis.
The long-term impact of studying field-matter coupling can range widely from discovering materials with traditionally unattainable properties to technological development in areas like additive manufacturing of ceramics.