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Negative thermal expansion ALLVAR alloys for telescopes
Author(s): James A. Monroe; Jeremy S. McAllister; David S. Content; Jay Zgarba; Xavier Huerta; Ibrahim Karaman
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Paper Abstract

Most materials naturally expand when heated and contract when cooled; this is known as thermal expansion and is typically characterized by a Coefficient of Thermal Expansion (CTE). Competition between different materials, each with their own CTE, can push optic systems out of focus when the system’s temperature changes. The use of low CTE materials like Invar, carbon fiber composites, and silicon carbide help reduce these temperature effects. Unfortunately, they each have drawbacks such as the high density and low corrosion resistance of Invar, the polymer outgassing of carbon fiber composites, and the low fracture toughness of silicon carbide. In comparison, ALLVAR alloys shrink when heated, known as a negative thermal expansion (NTE), and have low density, high corrosion resistance, high ductility, and do not outgas. This NTE behavior, down to -16 x 10-6 °C-1 at room temperature, offers a new way to athermalize optic systems by combining NTE alloys with positive CTE materials. The NTE alloy can compensate for a positive CTE material to achieve a desired CTE. Here we evaluate ALLVAR alloys as a potential material for optics applications.

Paper Details

Date Published: 10 July 2018
PDF: 11 pages
Proc. SPIE 10706, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, 107060R (10 July 2018); doi: 10.1117/12.2314657
Show Author Affiliations
James A. Monroe, ALLVAR (United States)
Jeremy S. McAllister, ALLVAR (United States)
David S. Content, ALLVAR (United States)
Jay Zgarba, ALLVAR (United States)
Xavier Huerta, Texas A&M Univ. (United States)
Ibrahim Karaman, Texas A&M Univ. (United States)

Published in SPIE Proceedings Vol. 10706:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III
Ramón Navarro; Roland Geyl, Editor(s)

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