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Monday | Jan. 28 | 8:30 a.m. – Noon Engineering Ceramics Division Award Winners James I. Mueller Award almost always catastrophic (barring subcritical crack growth related issues). recipient: Anil V. Virkar however, under internal loading, failure is stable and not abrupt. the two Distinguished Professor, Department Chair, College different modes of failure will be compared and contrasted. of engineering, Department of Materials Science and engineering, University of Utah Failure of Ceramics under Externally Applied Loads and Internally Generated Pressures: Bridge Building Award Zirconia, a Unique Material recipient: Tatsuki Ohji Stabilized zirconia exists in two crystallographic forms: cubic and tetrago- Prime Senior research Scientist, national institute of nal. Zirconia has been extensively investigated for various applications Advanced industrial Science and technology (AiSt) that exploit its ionic transport properties, its refractory properties, and its and Designated Professor in the graduate School of excellent mechanical properties. Solid oxide fuel cells, sensors, electrolyzers, Science and engineering, Meijo University thermal barrier coatings, heating elements, ball bearings, medical implants, Microstructural Evolution and Mechanical etc., are some of the applications. tetragonal zirconia is known for its excel- Properties of Engineering Ceramics lent mechanical properties attributed to the t → m martensitic transforma- Ceramic materials are composed of a variety of structural elements, tion and ferroelasticity. excellent oxygen-ion conductivity of zirconia is the including defects, grains, particles, pores, fibers, layers, and interfaces at dif- reason for its use in fuel cells and electrolyzers. in many mechanical and ferent scale levels. in terms of size, the structural elements can be classified electrochemical applications, zirconia exhibits failure in service under some into four categories: (1) atomic and molecular scale (2) nanoscale (order of conditions. the commonly experienced failure is under externally applied 10-6 mm); (3) microscale (order of 10-3 mm); and (4) macroscale. it is possible loads. increases in fracture toughness and strength achieved through pro- to realize new or unique performance or markedly improve properties in cessing, microstructure control, etc., lead to greater reliability. this has been ceramics, by controlling systematically these structural elements. taking, as extensively investigated. however, cracking of zirconia also occurs under an instance, silicon nitride, which is one of the most widely used engineering electrochemical conditions. Such failures occur under internally generated ceramics, this paper intends to show that the mechanical properties includ- pressures. Although cracking occurs in both types of failures, the origin and ing strength, toughness, and creep resistance can be tremendously improved mechanisms can be very different in the two cases. Conventional approaches when the sizes, morphologies, orientation, distribution, etc., of grains and of increasing strength and toughness have little role in mitigating failures pores as well as grain-boundary structure are carefully controlled. examples that often occur in electrochemical systems. rather, ion and electron trans- are: (1) super strong silicon nitride with >2 gPa strength via refinement port properties determine whether failures can be mitigated. Additionally, and alignment control of grains; (2) porous silicon nitride with high strength even the mechanism of cracking is different from failures observed under (>1 gPa), and high toughness (300–500 J/m2— far higher than that of the externally applied loads. the two different modes of fracture will be com- dense) via morphology and alignment control of grains and pores; and (3) pared and contrasted. in external loading, one seeks solutions to fracture super-heat-resistant silicon nitride with strength retention up to 1500°C and mechanical problems by solving elasticity equations. in electrochemical toughness of approximately 800 J/m2 (double that of cast iron). the paper systems with internally generated pressures, a coupling exists between elec- also focuses on improved mechanical properties via microstructure control trochemical transport (e.g., solution to transport equations) and mechanics. for high thermal conductivity silicon nitride, which is expected to be applied this leads to different cracking patterns. Under external loading, failure is as substrate materials in future power devices. 2013 Plenary Speakers Do-Suck Han Bruce Dunn Director/CAe & Materials research, hyundai Motor nippon Sheet glass Professor of Materials Science Company, r&D Division and engineering, UCLA Nanocomposite Materials for the Next- Designing Ceramics for Electrochemical Energy Generation Vehicles Storage Devices there have been strong moves in recent years to the ability to design the chemistry and nanostruc- apply advanced materials based on the recent legislative ture of ceramics is having a profound effect on the and environmental pressures on the automotive industry performance of electrode materials for electrochemical to produce light-weight fuel-efficient vehicles with lower emissions. those energy storage. Some of the key advances in this field will be discussed in social pressures have led to a requirement for traditional components to be this presentation. in the lithium-ion battery field, improvements in energy replaced by advanced materials. nanocomposite materials are expected to and power densities are attributed to the development of nanoscale materi- be attractive materials that combine the elements of significant weight sav- als that exhibit shorter ion and electron diffusion lengths. the development ing, improved performance, and multifunctionality, such as low friction, high of carbon coatings and core–shell materials represents another significant heat resistance and anti-corrosion. the nanotechnology already has been advance in the design of electrode materials. this approach enables new introduced to the automotive components from material scale to structural families of poorly conducting oxides to be used as insertion electrodes. scale. this has led to a complete reanalysis of the design and manufacturing Mesoporous transition-metal oxides also are emerging as an important routes, with the emergence of advanced technologies as a viable process direction in the energy storage field. the mesoporous architecture provides for the production of high-volume, low-cost, high-integrity automotive com- electrolyte access to redox-active walls and enables higher energy densities ponents. in this lecture the development and application of nanocomposite to be attained. the energy storage field faces a number of future challenges materials and key technologies will be described and discussed in terms of and these items also will be discussed. vehicle performance and cost effectiveness. the research activities described illustrate the benefits of tailoring of design, processing and materials suitable for conventional vehicles as well as ev, hev and FCev. 40 www.ceramics.org | American Ceramic Society Bulletin, Vol. 92, No. 1


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