(Opening Keynote) Heterogeneous Functional Materials: Their Present Science and Engineering, and Their Role in the Future of Our Society
Authors: Reifsnider Kenneth 
Published: July 2022

Devices that convert and store energy are generally made from heterogeneous constituent materials that act and interact to selectively conduct, transport, and regulate mass, heat, and charge. Controlling these functional actions and interactions enables the technical breakthroughs that have made high efficiency fuel cells, batteries, and solid state membranes, for example, essential parts of our society and economy. In the biological sense, these materials are ‘vascular’ rather than primitive ‘cellular’ materials, so that the arrangements and configurations of the constituents play essential roles in their functional capabilities. Local interactions of the constituents create “emergent” properties and responses that are not part of the formal set of constituent characteristics, in much the same sense that society and culture is created by the group interactions of the people involved. The design of emergent properties is an open question in all formal science, but for energy materials the lack of this foundation science relegates development tasks to Edisonian trial and error, with anecdotal success and frequent costly failures. The present group has defined, for the first time, multi-scale heterogeneous functional materials with functional disordered and void phase regions as “HeteroFoaM,” and formed the first multidisciplinary research team (EFRC) to define and codify the foundation science of that material class. The primary goal of the HeteroFoaM Center was, and the continuing interest is, to create and establish the multi-scale fundamental knowledge and related methodology required for the rational and systematic multiphysics design of heterogeneous functional materials and their interfaces and surfaces for applications in energy transformation and storage. HeteroFoaM is a new atoms-to-systems paradigm that is intended to bring heterogeneous functional materials (for which the system is rarely simply the sum of the parts) into the modern age of computational materials to achieve the savings of time and cost associated with trial and error Edisonian design.

The promise of this pursuit is to construct a Multi-Scale/Multi-Physics (M2SP) Design Science for Heterogeneous Functional Materials that is codified in models and codes that enable the design of material systems to convert fuels directly into electricity, store energy in easily transported forms, and separate strategic materials including nuclear waste.

The HeteroFoaM paradigm is an approach that focuses on the “conformal science” that defines the local interactions that result from the arrangements and configurations of the constituents. The approach fully embraces the complexity of heterogeneous functional material systems including the uncertainty of predictions and observations, the creation of a formal structure for combining analysis, simulations, and experiments, and the creation of a science path to the prediction of emergent global response probabilities based on the local or meso-science of constituent interactions.

However, since this concept was originated almost 10 years ago, a technical revolution has happened in our world society that makes progress in this field even more imperative. There has been an historic shift in our society to hydrogen as a preferred fuel, with industrial and governmental promises that it will be nearly an exclusive choice for society and industry in the next ten years or so. Therefore, our discussion will begin with the historic foundations of this field and end with a short summary of the remarkable and historic changes in society that have elevated this subject to a central and critical science and engineering subject for our world society today.