Expanding the frontier - Grand challenges in ceramic science

aug13

Expanding the frontier—Grand challenges in ceramic science By Gregory S. Rohrer (Credit: ACerS.) Lou Mattos from The Coca-Cola Company describes challenges to achieving maximum glass strength. A little over one year ago, a group of ceramics researchers from academia, government labs, and industry (Table 1) met at a workshop near Washington D.C. to identify and articulate the emerging scientific grand challenges facing the ceramics research community. Following the workshop, the group coauthored a report that was published in the Journal of the American Ceramic Society.1 There have been forward-looking sessions at the biannual International Congress on Ceramics, but these have had a distinct technology, rather than science, focus.2 Since the previous workshop in 1997 on future directions for ceramics,3 there have been some truly transformational changes in our field. In the area of characterization, atomic force microscopy, aberration-corrected transmission electron microscopy, high-speed electron backscatter diffraction mapping, three-dimensional atom probe microscopy, and dual-beam focused ion beam scanning electron microscopy have transitioned from laboratory curiosities to nearly standard methods enabling new discoveries. In the area of synthesis and processing, thin-film growth by pulsed laser deposition and molecular beam epitaxy, current-activated pressure-assisted densification, and templated grain growth are important methods for controlling the structure and composition of ceramics. Also, new phenomena have been identified and exploited, including colossal magnetoresistance, two-dimensional electron gasses, and interface complexions, to name a few. Nanoscale phenomena, just emerging 15 years ago, now permeate the field. Finally, the ability to simulate ceramics from electronic structure calculations, kinetic Monte Carlo simulations, mesoscale simulations, and finite-element models have kept pace with Moore’s law and now permit the exploration of more practical length and time scales. In other words, the landscape for ceramics research has changed dramatically in the past 15 years, and this is an appropriate time The landscape for ceramics research has changed dramatically in the past 15 years. to consider challenges for the future. Other broad trends in materials research, for example, issues of sustainability, have to be considered, too. The workshop participants considered separately oxide ceramics, composites, glasses, and other nonoxide and carbon-based ceramic materials with the goal of identifying a set of scientific grand challenges for the ceramics research community with a scope that will require five to ten years of effort by multiple research groups to be addressed adequately. They reached consensus on eight grand challenges for ceramic science, but they do not consider this list to be exhaustive. A very brief synopsis of the eight challenges (excerpted from the JACerS paper) follows. No priority is implied by the order, but they represent the output of the subgroups who considered composites (1–3), oxides (4, 5), non-oxides (6, 7), and glasses (8). (Editor’s note: The JACerS article is open access and available free online at www.onlinelibrary.wiley.com. See the article for extensive bibliographic citations.) 1. Understanding rare events in ceramic microstructures The lifetimes of ceramics in many structural and functional applications are particularly sensitive to rare events. These include brittle failure during mechanical or thermal loading, pitting by corrosion, dielectric breakdown, and fatigue crack initiation. The challenge is to understand the causes and mechanisms by which rare events lead to failure. Previous attempts to understand these processes engineered experiments to eliminate their statistical nature. In fracture experiments, for example, precracks or notches are placed in specimens to provide focus for the experiment. Although affording useful information in assessing the steady-state phenomena of crack growth, these experiments mask information regarding the nucleation or initiation event. Of even greater concern from a technological perspective is that lifetime predictions based on continuum or fracture mechanics treatments for artificial American Ceramic Society Bulletin, Vol. 92, No. 6 | www.ceramics.org 29


aug13
To see the actual publication please follow the link above