far-from-equilibrium materials laboratory

We @J-Lab Engineer Far-From-Equilibrium Materials Using Electromagnetic Fields

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.

We @J-Lab 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 ZrO2,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 EM 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. [LINK]

J-Lab’s efforts pursue scientific challenges that remain to be addressed such as (a) Advancing measurements (e.g., local temperatures) and in-situ characterization tools that can follow the dynamics of the field-assisted processes and distinguish specific effects of the field itself from conventional thermal phenomena; [LINK] and (b) Devising multiscale computational models to understand and predict phase transformations and microstructural evolution occurring under externally applied fields.

The impact of studying field-matter coupling can range widely from discovering materials with traditionally unattainable properties [LINK] to technological development for new ceramic manufacturing processes that avoid high temperature and extreme polluting steps. [LINK]

Efforts currently underway at the Air Force Research Laboratory (AFRL) Center of Excellence at Carnegie Mellon University in particular focuses on combining in-situ synchrotron based characterization and atomistic simulations with closed-loop active machine learning. A long-term vision is to engineer a dynamic, real-time, data-controlled robotic platform that uses EM fields to precisely engineer materials with unique multifunctional properties. LINK

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