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Negative CTE materials

Negative CTE materials. Materials with negative coefficients of thermal expansion by Will Bray MEEN 3344 20 March 2006. Reasons. Most materials expand when heated, causing parts to change dimensions When two different materials heat up, ~~

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Negative CTE materials

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  1. Negative CTE materials Materials with negative coefficients of thermal expansion by Will Bray MEEN 3344 20 March 2006

  2. Reasons • Most materials expand when heated, causing parts to change dimensions • When two different materials heat up, ~~ • By combining materials with negative CTE into other materials, thermal expansion can be tailored to specific needs

  3. Examples • Fe-Ni alloys, microfabrication • Carbon nanotubes have negative CTE along axis

  4. The tetrahedra (red) and octahedra (green) that make up the crystal structure in zirconium tungstate. When heated, these figures squeeze together. Credit: Alison Kendall

  5. Simplified example of how increasing temperature can reduce size

  6. Applications • Electronics- allow components to expand together or reduce expansion • Carbon-fiber reinforced glass for Precision Mirrors (i.e. satellites) • Negative Axial CTE fibers in positive CTE matrix for aerospace composites

  7. Sources • http://www.ml.afrl.af.mil/news/MLL/asc_04_0161.html • http://www.cytec.com/business/EngineeredMaterials/CFInternet/cfperformancedesign.shtm • http://optics.nasa.gov/tech_days/tech_days_2003/docs/24AFRLCTETailoredMaterialsforMirrors.pdf • http://www.isis.rl.ac.uk/ISIS97/feature1.pdf • http://www.livescience.com/technology/041215_unusual_material.html

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