{"id":{"repo_id":"ottawa-retro","oai_identifier":"oai:ruor.uottawa.ca:10393/7548"},"canonical_url":"https://search.dev.ndltd.org/etd/ottawa-retro/oai:ruor.uottawa.ca:10393/7548","repository":{"repo_id":"ottawa-retro","name":"University of Ottawa","base_url":"https://ruor.uottawa.ca/server/oai/request"},"display":{"title":"A iron-57 Moessbauer study on the thermal oxidation of iron in biotite mica.","abstract":"We have studied the oxidation in air of a well characterized biotite sample. Large single crystal wafers were annealed at various temperatures up to 875$\\sp\\circ$C and for various times up to 94 hours. The oxidation proceeds primarily via the oxyannite reaction: $\\rm (Fe\\sp{2+} + OH\\sp-)\\sb{mica} \\to (Fe\\sp{3+} + O\\sp{2-})\\sb{mica} + H$ and was therefore conveniently followed by $\\sp{57}$Fe Mossbauer spectroscopy, which resolves the 2+ and 3+ valence states of iron. The main features of the annealing time and temperature dependencies of the $\\rm Fe\\sp{3+}/Fe\\sp{2+}$ amounts are understood in terms of a simple model in which: (i) the overall oxidation reaction proceeds homogeneously via a time-wise bottleneck step that follows a classic thermal activation law and (ii) a certain fraction of the original Fe$\\sp{2+}$ is inaccessible to the oxidation reaction. The resulting barrier energy, $\\rm E\\sb{b} = 2.36\\sbsp{-.02}{+.01}$ eV is in the range of measured barrier energies for dehydroxylation of layer silicates. This suggests that the bottleneck step may be local dehydroxylation: $\\rm (OH\\sp-\\ \\to O\\sp{2-}\\ + H\\sp+).$ The persistent Fe$\\sp{2+}$ can be understood from local crystal-chemical considerations. (Abstract shortened by UMI.)","abstract_html":"We have studied the oxidation in air of a well characterized biotite sample. Large single crystal wafers were annealed at various temperatures up to 875$\\sp\\circ$C and for various times up to 94 hours. The oxidation proceeds primarily via the oxyannite reaction: $\\rm (Fe\\sp{2+} + OH\\sp-)\\sb{mica} \\to (Fe\\sp{3+} + O\\sp{2-})\\sb{mica} + H$ and was therefore conveniently followed by $\\sp{57}$Fe Mossbauer spectroscopy, which resolves the 2+ and 3+ valence states of iron. The main features of the annealing time and temperature dependencies of the $\\rm Fe\\sp{3+}/Fe\\sp{2+}$ amounts are understood in terms of a simple model in which: (i) the overall oxidation reaction proceeds homogeneously via a time-wise bottleneck step that follows a classic thermal activation law and (ii) a certain fraction of the original Fe$\\sp{2+}$ is inaccessible to the oxidation reaction. The resulting barrier energy, $\\rm E\\sb{b} = 2.36\\sbsp{-.02}{+.01}$ eV is in the range of measured barrier energies for dehydroxylation of layer silicates. This suggests that the bottleneck step may be local dehydroxylation: <span class=\"etd-inline-math\">\\rm (OH\\sp- \\to O\\sp{2-} + H\\sp+).</span> The persistent Fe$\\sp{2+}$ can be understood from local crystal-chemical considerations. (Abstract shortened by UMI.)","abstract_has_math":true,"creators":["Tume, Pamela."],"institution":"University of Ottawa (Canada)","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2009,"date_issued":"2009-03-23T15:59:33Z","date_published":"2009-03-23T15:59:33Z","updated_at":"2026-07-24T03:39:18Z","subjects":["Physics, Condensed Matter."],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["Source: Masters Abstracts International, Volume: 32-01, page: 0268.","9780315800168","http://dx.doi.org/10.20381/ruor-15396"],"render_values":[{"text":"Source: Masters Abstracts International, Volume: 32-01, page: 0268.","href":null,"code":true},{"text":"9780315800168","href":null,"code":true},{"text":"http://dx.doi.org/10.20381/ruor-15396","href":"http://dx.doi.org/10.20381/ruor-15396","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10393/7548","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Tume, Pamela."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2009-03-23T15:59:33Z","1992"]},{"key":"dc:publisher","label":"Institution","values":["University of Ottawa (Canada)"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics, Condensed Matter."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["Source: Masters Abstracts International, Volume: 32-01, page: 0268.","9780315800168","http://hdl.handle.net/10393/7548","http://dx.doi.org/10.20381/ruor-15396"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["We have studied the oxidation in air of a well characterized biotite sample. Large single crystal wafers were annealed at various temperatures up to 875$\\sp\\circ$C and for various times up to 94 hours. The oxidation proceeds primarily via the oxyannite reaction: $\\rm (Fe\\sp{2+} + OH\\sp-)\\sb{mica} \\to (Fe\\sp{3+} + O\\sp{2-})\\sb{mica} + H$ and was therefore conveniently followed by $\\sp{57}$Fe Mossbauer spectroscopy, which resolves the 2+ and 3+ valence states of iron. The main features of the annealing time and temperature dependencies of the $\\rm Fe\\sp{3+}/Fe\\sp{2+}$ amounts are understood in terms of a simple model in which: (i) the overall oxidation reaction proceeds homogeneously via a time-wise bottleneck step that follows a classic thermal activation law and (ii) a certain fraction of the original Fe$\\sp{2+}$ is inaccessible to the oxidation reaction. The resulting barrier energy, $\\rm E\\sb{b} = 2.36\\sbsp{-.02}{+.01}$ eV is in the range of measured barrier energies for dehydroxylation of layer silicates. This suggests that the bottleneck step may be local dehydroxylation: $\\rm (OH\\sp-\\ \\to O\\sp{2-}\\ + H\\sp+).$ The persistent Fe$\\sp{2+}$ can be understood from local crystal-chemical considerations. (Abstract shortened by UMI.)"]},{"key":"dc:format","label":"Dc Format","values":["131 p.","application/pdf"]},{"key":"dc:title","label":"Title","values":["A iron-57 Moessbauer study on the thermal oxidation of iron in biotite mica."]}]}],"canonical_facts":{"dc:creator":["Tume, Pamela."],"dc:date":["2009-03-23T15:59:33Z","1992"],"dc:description":["We have studied the oxidation in air of a well characterized biotite sample. Large single crystal wafers were annealed at various temperatures up to 875$\\sp\\circ$C and for various times up to 94 hours. The oxidation proceeds primarily via the oxyannite reaction: $\\rm (Fe\\sp{2+} + OH\\sp-)\\sb{mica} \\to (Fe\\sp{3+} + O\\sp{2-})\\sb{mica} + H$ and was therefore conveniently followed by $\\sp{57}$Fe Mossbauer spectroscopy, which resolves the 2+ and 3+ valence states of iron. The main features of the annealing time and temperature dependencies of the $\\rm Fe\\sp{3+}/Fe\\sp{2+}$ amounts are understood in terms of a simple model in which: (i) the overall oxidation reaction proceeds homogeneously via a time-wise bottleneck step that follows a classic thermal activation law and (ii) a certain fraction of the original Fe$\\sp{2+}$ is inaccessible to the oxidation reaction. The resulting barrier energy, $\\rm E\\sb{b} = 2.36\\sbsp{-.02}{+.01}$ eV is in the range of measured barrier energies for dehydroxylation of layer silicates. This suggests that the bottleneck step may be local dehydroxylation: $\\rm (OH\\sp-\\ \\to O\\sp{2-}\\ + H\\sp+).$ The persistent Fe$\\sp{2+}$ can be understood from local crystal-chemical considerations. (Abstract shortened by UMI.)"],"dc:format":["131 p.","application/pdf"],"dc:identifier":["Source: Masters Abstracts International, Volume: 32-01, page: 0268.","9780315800168","http://hdl.handle.net/10393/7548","http://dx.doi.org/10.20381/ruor-15396"],"dc:publisher":["University of Ottawa (Canada)"],"dc:subject":["Physics, Condensed Matter."],"dc:title":["A iron-57 Moessbauer study on the thermal oxidation of iron in biotite mica."],"dc:type":["Thesis"]},"updated_at":"2026-07-24T03:39:18Z"}