{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/29456"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/29456","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Thermal conductivity of UO2 and U3O8 epitaxial layers damaged by ion irradiation","abstract":"This thesis presents experimental results on thermal conductivity measurements on both irradiated and unirradiated uranium oxides between 90 K and 658 K. The irradiation doses range from 5x10^13 argon ions/cm² to 2x10^16 Ar+/cm² at 2 MeV and room temperature. The main focus lies on 360 – 500 nm single crystal UO2 and U3O8 thin films grown on YSZ substrates. The U3O8 samples are formed by heating the UO2 in air for 2.5 hours at 600°C and slow cooling. From a comparison between data measured by an optical pump-probe technique – time-domain thermoreflectance (TDTR) – and a heat transport model the thermal conductivity of the sample under study can be determined. For UO2, the thermal conductivity is found to be 10.2 W/m.K at 323 K and with increasing temperatures its behavior is inversely proportional to the temperature. At 648 K the thermal conductivity is 4.9 W/m.K. The thermal conductivity peaks between 200 and 250 K and decreases for decreasing temperatures. Upon irradiation the thermal conductivity at 323 K decreases to 8.6 W/m.K for a dose of 5x10^13 Ar+/cm² and to 4 W/m.K for 7x10^14 Ar+/cm² and 1x10^16 Ar+/cm². At 648 K the corresponding values are 5.2 W/m.K, 4.2 W/m.K and 2.5 W/m.K for the mentioned doses. A modified model by Klemens is used to predict the irradiation effect on the thermal conductivity for low and medium doses. For high doses non-linearities during the irradiation limit the further decrease in thermal conductivity and cannot be captured by the model. Due to self-annealing during the experiments, irradiated samples do not show a 1/T behavior. U3O8 is studied with irradiation doses of 0 Ar+/cm², 7x10^14 Ar+/cm², 2x10^15 Ar+/cm² and 2x10^16 Ar+/cm². Their thermal conductivities at 333 K are 1.67 W/m.K, 0.96 W/m.K, 1.2 W/m.K and 1.97 W/m.K, respectively. The self-annealing is found to be stronger than in UO2 so that the thermal conductivities at 658 K are 1.3 W/m.K, 1.18 W/m.K, 1.36 W/m.K and 1.86 W/m.K, respectively, for the above mentioned doses. For lower doses the thermal conductivity decreases with increasing dose but then starts increasing again for higher doses. This is probably caused by re-crystallization and the formation of a second phase of UO2+x in U3O8. In general, it is found that oxidation of UO2 has a stronger influence on the thermal conductivity than irradiation with argon ions.","abstract_html":"This thesis presents experimental results on thermal conductivity measurements on both irradiated and unirradiated uranium oxides between 90 K and 658 K. The irradiation doses range from 5x10^13 argon ions/cm² to 2x10^16 Ar+/cm² at 2 MeV and room temperature. The main focus lies on 360 – 500 nm single crystal UO2 and U3O8 thin films grown on YSZ substrates. The U3O8 samples are formed by heating the UO2 in air for 2.5 hours at 600°C and slow cooling. From a comparison between data measured by an optical pump-probe technique – time-domain thermoreflectance (TDTR) – and a heat transport model the thermal conductivity of the sample under study can be determined. For UO2, the thermal conductivity is found to be 10.2 W/m.K at 323 K and with increasing temperatures its behavior is inversely proportional to the temperature. At 648 K the thermal conductivity is 4.9 W/m.K. The thermal conductivity peaks between 200 and 250 K and decreases for decreasing temperatures. Upon irradiation the thermal conductivity at 323 K decreases to 8.6 W/m.K for a dose of 5x10^13 Ar+/cm² and to 4 W/m.K for 7x10^14 Ar+/cm² and 1x10^16 Ar+/cm². At 648 K the corresponding values are 5.2 W/m.K, 4.2 W/m.K and 2.5 W/m.K for the mentioned doses. A modified model by Klemens is used to predict the irradiation effect on the thermal conductivity for low and medium doses. For high doses non-linearities during the irradiation limit the further decrease in thermal conductivity and cannot be captured by the model. Due to self-annealing during the experiments, irradiated samples do not show a 1/T behavior. U3O8 is studied with irradiation doses of 0 Ar+/cm², 7x10^14 Ar+/cm², 2x10^15 Ar+/cm² and 2x10^16 Ar+/cm². Their thermal conductivities at 333 K are 1.67 W/m.K, 0.96 W/m.K, 1.2 W/m.K and 1.97 W/m.K, respectively. The self-annealing is found to be stronger than in UO2 so that the thermal conductivities at 658 K are 1.3 W/m.K, 1.18 W/m.K, 1.36 W/m.K and 1.86 W/m.K, respectively, for the above mentioned doses. For lower doses the thermal conductivity decreases with increasing dose but then starts increasing again for higher doses. This is probably caused by re-crystallization and the formation of a second phase of UO2+x in U3O8. In general, it is found that oxidation of UO2 has a stronger influence on the thermal conductivity than irradiation with argon ions.","abstract_has_math":false,"creators":["Weisensee, Patricia"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Cahill, David G."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-02-01T00:47:05Z","date_published":"2012-02-01T00:47:05Z","updated_at":"2026-07-22T22:25:27Z","subjects":["Thermal Conductivity","Uranium Dioxide","UO2","U3O8","Ion (Ar) Irradiation Damage","Thin Film"],"languages":["en"],"rights":["© 2011 Patricia B. Weisensee"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/29456","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Cahill, David G."]},{"key":"dc:creator","label":"Author","values":["Weisensee, Patricia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2012-02-01T00:47:05Z","2014-02-01T11:00:28Z","2011-12"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation / Thesis","text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Thermal Conductivity","Uranium Dioxide","UO2","U3O8","Ion (Ar) Irradiation Damage","Thin Film"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["© 2011 Patricia B. Weisensee"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/29456"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This thesis presents experimental results on thermal conductivity measurements on both irradiated and unirradiated uranium oxides between 90 K and 658 K. The irradiation doses range from 5x10^13 argon ions/cm² to 2x10^16 Ar+/cm² at 2 MeV and room temperature. The main focus lies on 360 – 500 nm single crystal UO2 and U3O8 thin films grown on YSZ substrates. The U3O8 samples are formed by heating the UO2 in air for 2.5 hours at 600°C and slow cooling. From a comparison between data measured by an optical pump-probe technique – time-domain thermoreflectance (TDTR) – and a heat transport model the thermal conductivity of the sample under study can be determined. For UO2, the thermal conductivity is found to be 10.2 W/m.K at 323 K and with increasing temperatures its behavior is inversely proportional to the temperature. At 648 K the thermal conductivity is 4.9 W/m.K. The thermal conductivity peaks between 200 and 250 K and decreases for decreasing temperatures. Upon irradiation the thermal conductivity at 323 K decreases to 8.6 W/m.K for a dose of 5x10^13 Ar+/cm² and to 4 W/m.K for 7x10^14 Ar+/cm² and 1x10^16 Ar+/cm². At 648 K the corresponding values are 5.2 W/m.K, 4.2 W/m.K and 2.5 W/m.K for the mentioned doses. A modified model by Klemens is used to predict the irradiation effect on the thermal conductivity for low and medium doses. For high doses non-linearities during the irradiation limit the further decrease in thermal conductivity and cannot be captured by the model. Due to self-annealing during the experiments, irradiated samples do not show a 1/T behavior. U3O8 is studied with irradiation doses of 0 Ar+/cm², 7x10^14 Ar+/cm², 2x10^15 Ar+/cm² and 2x10^16 Ar+/cm². Their thermal conductivities at 333 K are 1.67 W/m.K, 0.96 W/m.K, 1.2 W/m.K and 1.97 W/m.K, respectively. The self-annealing is found to be stronger than in UO2 so that the thermal conductivities at 658 K are 1.3 W/m.K, 1.18 W/m.K, 1.36 W/m.K and 1.86 W/m.K, respectively, for the above mentioned doses. For lower doses the thermal conductivity decreases with increasing dose but then starts increasing again for higher doses. This is probably caused by re-crystallization and the formation of a second phase of UO2+x in U3O8. In general, it is found that oxidation of UO2 has a stronger influence on the thermal conductivity than irradiation with argon ions.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-12-05T21:56:45Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Weisensee_Patricia.doc: 6940672 bytes, checksum: a5c0957a5b794fd21390031cfa52c7e0 (MD5) Weisensee_Patricia.pdf: 3804373 bytes, checksum: 5572e2c8cee49ecb61aa28209a92f4b2 (MD5)","Made available in DSpace on 2012-02-01T00:47:05Z (GMT). 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The irradiation doses range from 5x10^13 argon ions/cm² to 2x10^16 Ar+/cm² at 2 MeV and room temperature. The main focus lies on 360 – 500 nm single crystal UO2 and U3O8 thin films grown on YSZ substrates. The U3O8 samples are formed by heating the UO2 in air for 2.5 hours at 600°C and slow cooling. From a comparison between data measured by an optical pump-probe technique – time-domain thermoreflectance (TDTR) – and a heat transport model the thermal conductivity of the sample under study can be determined. For UO2, the thermal conductivity is found to be 10.2 W/m.K at 323 K and with increasing temperatures its behavior is inversely proportional to the temperature. At 648 K the thermal conductivity is 4.9 W/m.K. The thermal conductivity peaks between 200 and 250 K and decreases for decreasing temperatures. Upon irradiation the thermal conductivity at 323 K decreases to 8.6 W/m.K for a dose of 5x10^13 Ar+/cm² and to 4 W/m.K for 7x10^14 Ar+/cm² and 1x10^16 Ar+/cm². At 648 K the corresponding values are 5.2 W/m.K, 4.2 W/m.K and 2.5 W/m.K for the mentioned doses. A modified model by Klemens is used to predict the irradiation effect on the thermal conductivity for low and medium doses. For high doses non-linearities during the irradiation limit the further decrease in thermal conductivity and cannot be captured by the model. Due to self-annealing during the experiments, irradiated samples do not show a 1/T behavior. U3O8 is studied with irradiation doses of 0 Ar+/cm², 7x10^14 Ar+/cm², 2x10^15 Ar+/cm² and 2x10^16 Ar+/cm². Their thermal conductivities at 333 K are 1.67 W/m.K, 0.96 W/m.K, 1.2 W/m.K and 1.97 W/m.K, respectively. The self-annealing is found to be stronger than in UO2 so that the thermal conductivities at 658 K are 1.3 W/m.K, 1.18 W/m.K, 1.36 W/m.K and 1.86 W/m.K, respectively, for the above mentioned doses. For lower doses the thermal conductivity decreases with increasing dose but then starts increasing again for higher doses. This is probably caused by re-crystallization and the formation of a second phase of UO2+x in U3O8. In general, it is found that oxidation of UO2 has a stronger influence on the thermal conductivity than irradiation with argon ions.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-12-05T21:56:45Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Weisensee_Patricia.doc: 6940672 bytes, checksum: a5c0957a5b794fd21390031cfa52c7e0 (MD5) Weisensee_Patricia.pdf: 3804373 bytes, checksum: 5572e2c8cee49ecb61aa28209a92f4b2 (MD5)","Made available in DSpace on 2012-02-01T00:47:05Z (GMT). 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Weisensee"],"dc:subject":["Thermal Conductivity","Uranium Dioxide","UO2","U3O8","Ion (Ar) Irradiation Damage","Thin Film"],"dc:title":["Thermal conductivity of UO2 and U3O8 epitaxial layers damaged by ion irradiation"],"dc:type":["Dissertation / Thesis","text"],"thesis:degree_discipline":["Materials Science & Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:27Z"}