Synthesis and characterization of hydrated alkali thio-hydroxosilicogermanates of the form, Rb[subscript z](Ge[subscript x]Si₁[subscript x])S[subscript z](OH)₄[subscript z] ·yH₂O where 2[less than or equal to]z[less than or equal to]3 and 0.5[less than or equal to]x[less than or equal to]1.0

dc.contributor.author Nelson, Carly
dc.date 2019-12-13T03:29:09.000
dc.date.accessioned 2020-06-30T08:12:56Z
dc.date.available 2020-06-30T08:12:56Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2006
dc.date.issued 2006-01-01
dc.description.abstract <p>Research into fuel cell technology has increased dramatically recently due to the increasing gas prices and stricter pollution regulations. The need for a high proton conducting and thermally stable electrolyte for intermediate temperature (~100-300 °C) fuel cells has become a critical problem for proton exchange membrane (PEM) fuel cells in order to replace the present automobile internal combustion engines. Nafion is currently a very popular polymer electrolyte material with a proton conductivity of ~10⁻⁰̇·⁷⁷ ([Omega]cm)⁻¹ at 80 °C under heavily hydrated conditions. At temperatures above ~80 °C, Nafion dries out and its proton conductivity decreases to essentially zero. Research at ISU into alternative ceramic membranes for PEMs resulted in the development of alkali thio-hydroxogermanates (M[subscript x]GeS[subscript x](OH)₄[subscript x]·yH₂O where M=Na, K, Rb, Cs) with high proton conductivities of ~10⁻² ([Omega]cm)⁻¹ at 120 °C and thermal stabilities up to ~300 °C. In an effort to further increase the proton conductivity, especially at temperatures near room temperature and to increase the long term thermal stability, new ternary alkali thio-hydroxosilicogermanates where Si⁴ has been partially substituted for Ge⁴⁺ to form compositions of the form Rb[subscript z]Ge[subscript x]Si[subscript 1-x]S[subscript z](OH)[subscripr 4-z]·yH₂O, where z=2 and 3, and 0.5[less than or equal to]x[less than or equal to]1.0, have been prepared and characterized for the first time. It was found that the Ge-based phases were observed to have higher intermediate temperature proton conductivities than the Ge/Si phases. Studies were conducted on the proton conductivity as a function of the relative humidity and it was found that even low levels of hydration (~6% R.H.) greatly improved the proton conductivity at low temperatures indicating the important role of water in the proton conduction mechanism.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/rtd/19084/
dc.identifier.articleid 20084
dc.identifier.contextkey 15987043
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/19084
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/73055
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/rtd/19084/Nelson_ISU_2006_N45.pdf|||Fri Jan 14 21:52:11 UTC 2022
dc.subject.keywords Materials Science and Engineering
dc.title Synthesis and characterization of hydrated alkali thio-hydroxosilicogermanates of the form, Rb[subscript z](Ge[subscript x]Si₁[subscript x])S[subscript z](OH)₄[subscript z] ·yH₂O where 2[less than or equal to]z[less than or equal to]3 and 0.5[less than or equal to]x[less than or equal to]1.0
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
thesis.degree.discipline Materials Science and Engineering
thesis.degree.level thesis
thesis.degree.name Master of Science
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