Physical and Thermal Properties of Zirconium Tungstate Nanoparticles with Different Morphologies from Hydrothermal Synthesis

dc.contributor.advisor Michael R Kessler
dc.contributor.author Wu, Hongchao
dc.contributor.department Materials Science and Engineering
dc.date 2018-08-11T09:04:13.000
dc.date.accessioned 2020-06-30T02:43:17Z
dc.date.available 2020-06-30T02:43:17Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2012
dc.date.embargo 2014-10-31
dc.date.issued 2012-01-01
dc.description.abstract <p>Negative thermal expansion (NTE) materials belong to a group of solids that perform contractions in volume under heating conditions, instead of thermal expansion observed in most other solids. Due to this special negative thermal property, NTE materials are gradually drawing research interest for their potential application as fillers in composites used to control thermal stress' generating from mismatch of thermal expansivity and to govern the overall thermal expansion behavior.</p> <p>Zirconium tungstate (ZrW2O8) is a ceramic material that exhibits strong, isotropic NTE over a wide temperature range from 0.3 to 1050 K. The formation and transition of three phases ZrW2O8 can be achieved under certain temperatures and pressures. ZrW2O8 nanoparticles can be synthesized at lower temperatures by hydrothermal reaction followed by a subsequent heat treatment by converting the precursor ZrW2O7(OH)2*2H2O to ZrW2O8. However, nano-sized ZrW2O8 was reported to display a hydration phenomena when exposed to ambient external conditions. Through the careful selection of experimental parameters such as initial reactant types, acids types and concentrations, as well as reaction time and temperature, the effect of reaction conditions on morphologies and crystallite sizes of ZrW2O8 nanoparticles was characterized using scanning electron microscopy and powder X-ray diffraction. Three types of ZrW2O8 nanoparticles with distinct morphologies and crystallite size-scales were chosen for characterization and comparison. Thermal and physical properties, as well as the hydration problem, were compared using various techniques, including isothermal X-ray diffraction, Brunauer-Emmett-Teller (BET) surface area analyzer and thermogravimetric analysis. It was found that the synthesized ZrW2O8 nanoparticles present more negative CTE values than bulk-scaled in á-phase, and the CTE is dependent on the crystallite sizes of nanoparticles. All three types of nanoparticles underwent different extents of hydration problem originated from moisture adsorption, which is determined by pores structure formed by agglomeration of nanoparticles. It was observed that ZrW2O8 nanoparticles with smaller dimensional sizes tended to form large pores and suffered from most severe hydrations.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/12525/
dc.identifier.articleid 3532
dc.identifier.contextkey 3437895
dc.identifier.doi https://doi.org/10.31274/etd-180810-1048
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/12525
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/26714
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/12525/Wu_iastate_0097M_12626.pdf|||Fri Jan 14 19:23:49 UTC 2022
dc.subject.disciplines Engineering
dc.subject.keywords Hydrothermal Reaction
dc.subject.keywords Moisture adsorption
dc.subject.keywords Nanoparticles
dc.subject.keywords Negative Thermal Expansion
dc.subject.keywords Porosity
dc.subject.keywords Zirconium Tungstate
dc.title Physical and Thermal Properties of Zirconium Tungstate Nanoparticles with Different Morphologies from Hydrothermal Synthesis
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication bf9f7e3e-25bd-44d3-b49c-ed98372dee5e
thesis.degree.level thesis
thesis.degree.name Master of Science
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