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Composites with tailorable isotropic near-zero thermal expansion
|Heinrich Kern , Christian Georgi
Institute of Materials Technology, Technical University of Ilmenau, Gebäude "Werkstoffe 1", Ilmenau 98693, Germany
The satisfactory operation of various high technology systems is limited by the thermal expansion of individual components. Such components must be made of materials with zero thermal expansion or thermal expansion characteristics that match the attached components for optimum performance. Moreover, a variety of performance demands are additionally being placed on these systems. Com-posite materials are ideally suited to combine features of different materials, thus forming a material with desired properties. For example, commercial glass-ceramic materials with zero thermal expansion characteristics are composites of a crystalline phase with negative thermal expansion (NTE) and a glass phase with positive thermal expansion. However, glass-ceramic materials show some disadvan-tages due to low strength, low young’s modulus, their brittleness and low thermal conductivity. More-over, glass ceramics are in situ composites, i.e. their compositions are limited to certain glass-forming systems.
Research on NTE materials has broadened considerably since the 1990s and was mainly intended to facilitate the development of new high-performance composite materials with tuneable thermal proper-ties. As for most applications isotropic thermal expansion behaviour is preferred, the main goal has been to find cubic materials that would exhibit isotropic NTE. Zirconium tungstate ZrW2O8 exhibits a cubic framework structure and NTE of large magnitude over its entire stability range. These unique properties have made it the most promising candidate material for new composites with controllable thermal expansion.
This paper is intended to summarize the results of research on the design, preparation and properties of composites with tailorable thermal expansion using ZrW2O8 and related framework oxides. It intro-duces some of the issues surrounding these NTE materials and their application in composites.
Presentation: invited oral at E-MRS Fall Meeting 2005, Symposium H, by Heinrich Kern
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-27 09:31 Revised: 2009-06-07 00:44