November 8-12, 2015
Particle-filled-glass composites (FGCs) are being developed as new materials with structure and properties engineered for materials joining (e.g., for solid oxide fuel cells). Relative to conventional sealing glasses used to make hermetic glass-to-metal (GtM) seals, FGCs with tailored properties offer significant potential as more crack resistant hermetic seals with better performance and reliability. Additionally, compared to process sensitive crystallizable glasses, FGCs offer broader processing latitude and robustness, and afford greater control of seal microstructure and properties. FGCs are being developed using a combination of fundamental materials science and materials engineering, employing: 1) experimentally-validated molecular modeling to better understand and control bulk and interface glass chemistry-structure-property relations to improve seal performance and reliability; and 2) composite property and process modeling to facilitate FGC design, and to optimize FGC manufacturability and properties.
The modeling and characterization of glass chemistry-structure relations will be presented and discussed, including the classical force field model and glass characterization tools and techniques employed in this study. Initially, 3-component glasses containing 50-75 mole% SiO2 in the 25 BaO - x Al2O3 – (75-x) SiO2 system were melted, characterized, and simulated. Pedone’s multicomponent force field was adapted to and used within the LAMMPS molecular dynamics (MD) simulation code on Sandia’s Redsky supercomputer to complete the MD simulations. Analyses were completed to investigate and understand the effects of glass network forming (e.g. Si) and network modifying (e.g., Ba) ions on bulk and interface glass structure. Post processing analysis of the glass simulations yielded radial distribution function (RDF), atom-atom distance, coordination number (CN), bond angle, ring size, and Qn distribution data to compare with structural information obtained from magic angle spinning nuclear magnetic resonance (MAS NMR) and x-ray.
Finally, the design, processing, and properties of the advance FGCs being developed will be presented and discussed. Composite mixing and processing models have been used to design processable, 5-40 volume% filler loaded FGC composites with a coefficient of thermal expansion (CTE) that can be tuned from 12.5 – 19 μm/μm/°C to match the CTE of a variety of different metals.
Kevin Ewsuk, "Characterization and modeling to design and develop tailored-property filled glass composites" in "Composites at Lake Louise (CALL 2015)", Dr. Jim Smay, Oklahoma State University, USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/composites_all/51