Artwork: Radiation damage-induced Materials Modification (courtesy of Jie Lian)

1. Radiation Manipulation of Materials Structure Jie Lian, Rensselaer Polytechnic Institute, DMR 0906349 Outcome: Researchers at Rensselaer Polytechnic Institute have developed an radiation approach to manipulate materials structure and control phase stability. Impact: The extreme radiation creates a new dimension to materials synthesis and processing under highly non-equilibrium conditions, opening up a new pathway to new materials or structures with designed functionality and improved performance. Explanation:The materials phase stability is governed by the thermodynamics under equilibrium conditions based on the energy minimization principle. Zirconia has three different polymorphs of monoclinic, tetragonal and cubic phases, in which the phase stability can be controlled by temperature or chemical substitutions. Utilizing ion beam techniques, the thermodynamically meta-stable tetragonal phase can be fabricated and stabilized at room temperature. The radiation approach represents a simple way to manipulate materials phase stability, and has a great potential for tailoring toughness of thin films, surface coating and nanocomposites by controlling the tetragonality of the zirconia unit cell. Professor Jie Lian, of Rensselaer’s Mechanical, Aerospace & Nuclear Engineering, led the research team developing radiation approaches in manipulating materials phase stability and structures to improve materials performance. Artwork: Radiation damage-induced Materials Modification (courtesy of Jie Lian)

2. Tailoring Phase Stability by Temperature and RadiationJie Lian, Rensselaer Polytechnic Institute, DMR 0906349 Under equilibrium conditions, thermal annealing-induced phase transformations occur in nano-sized zirconia following the sequence from amorphous-to-tetragonal and to monoclinic polymorphs, accompanying with a grain coarsening process. This phase transformation sequence is consistent with the energy cross-over of zirconia at different size regimes. Specifically, the tetragonal zirconia is stable with the length scale below a critical value (e.g., 30 nm). Further increasing the grain size, the monoclinic phase is thermodynamically favored. Under a highly non-equilibrium condition of intensive beam irradiations, the thermodynamically-metastable tetragonal phase with enhanced thermo-mechanical properties can be stabilized as a result of radiation-induced accumulation of oxygen vacancies. An important correlation among materials’ phase stability, microstructure and length scale, thermodynamics and defect behavior was identified. Correlation of the phase stability, grain size, and thermodynamics upon thermal annealing and intense beam irradiations. (courtesy of Jie Lian)