Cryothermal vacuum measurement of thermochromic variable-emittance coatings with heating/cooling hysteresis for spacecraft thermal management

Sydney Taylor, Neal Boman, Jeremy Chao, Liping Wang

Research output: Contribution to journalArticlepeer-review

Abstract

In this work, the dynamic heat rejection of a VO2-based nanophotonic variable-emittance coating is demonstrated in a cryothermal vacuum experiment that simulates a cold space environment. The fabricated coating displays a significant augmentation in radiated heat flux, from 136 W/m2 at the onset of the VO2 insulator-to-metal phase transition to 444 W/m2 at the end, which is in excellent agreement with theoretical modeling. Additionally, the temperature stability of both VO2 thin films and the fabricated nanophotonic emitter are assessed for cryogenic temperatures (down to −196 °C) and high temperatures (up to 450 °C). The VO2 thin film shows little change in transmittance from cryogenic temperatures up to temperatures of 200 °C. The variable-emittance coating likewise shows no change in behavior at cryogenic temperatures, while the emittance remains stable up to 200 °C. The partial heating/cooling hysteresis behavior is also investigated for VO2 thin films on silicon and the variable-emittance coating, where a theoretical model quantifying the hysteresis effect is developed for both. The substantial increase in heat rejection upon VO2 phase transition at higher temperatures indicates great promise for the nanophotonic variable-emittance coating to be used for spacecraft thermal control with excellent temperature stability and resistance to thermal cycling.

Original languageEnglish (US)
Article number117561
JournalApplied Thermal Engineering
Volume199
DOIs
StatePublished - Nov 25 2021

Keywords

  • Hysteresis
  • Radiative cooling
  • Vanadium dioxide
  • Variable emittance

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Industrial and Manufacturing Engineering

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