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Effect of Hydrothermal Synthesis Conditions on the Morphology and Negative Thermal Expansivity of Zirconium Tungstate Nanoparticles

Authors

  • Hongchao Wu,

    1. Department of Materials Science and Engineering, Iowa State University, Ames, Iowa
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  • Prashanth Badrinarayanan,

    1. Department of Materials Science and Engineering, Iowa State University, Ames, Iowa
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  • Michael R. Kessler

    Corresponding author
    1. Department of Mechanical Engineering, Iowa State University, Ames, Iowa
    2. Ames Laboratory, US Department of Energy, Ames, Iowa
    • Department of Materials Science and Engineering, Iowa State University, Ames, Iowa
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Author to whom correspondence should be addressed. e-mail: mkessler@iastate.edu

Abstract

Zirconium tungstate (ZrW2O8) is a unique ceramic material that exhibits isotropic negative thermal expansion behavior, which can be produced at relatively low temperatures using hydrothermal synthesis and subsequent heat treatment. In this work, the effect of reaction conditions on morphology and crystallite size of ZrW2O8 nanoparticles is characterized through careful selection of initial reactants, acid types and concentration, reaction time, and temperature. Three types of ZrW2O8 nanoparticles with distinct morphologies and crystallite size scales were chosen to characterize and compare thermal and physical properties. Nano-sized ZrW2O8 particles for two of the morphologies exhibit a negative coefficient of thermal expansion (CTE) that is about 30% larger than the CTE of bulk ZrW2O8 in the α-phase (ca. −11.4 vs.−8.8 ppm/°C). A dependence of CTE on crystallite size and crystalline structure is demonstrated. It is also found that the morphology of the zirconium tungstate has a significant effect on the pore structure and level of hydration in the nanoparticles.

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