{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/106389"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/106389","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Positron annihilation spectroscopy to understand defect formation and evolution in neutron-irradiated Fe-Cr model alloys","abstract":"Positron annihilation spectroscopy (PAS) is a powerful, non-destructive technique used to characterize the defect properties of materials. There are two major types of PAS, positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). This work focused on the latter. DBS can be used to gain information on the various types of defects present in a material system and this technique is sensitive to both defect size and defect concentration. Several samples were irradiated at the Advanced Test Reactor at Idaho National Laboratory. These samples were irradiated at temperatures of 300, 450, and 550°C to doses of 0.01 and 0.1dpa (displacements per atom). DBS was used to develop a better understanding of defect formation in Fe-Cr base materials exposed to low doses. Specifically, the goal of this work is to develop a better fundamental understanding of the evolution of nanoscale and sub-nanoscale defect clusters in neutron irradiated Fe-Cr alloys. The results of this work were fairly complicated due to the fact that α’ precipitation could occur in several of these samples. It was found that in samples where early stages of α’ precipitation is possible, lower S-parameters were determined. The S-parameter is indicative of the number and size of vacancy-type defects in the samples, so a lower S-parameter suggests that chromium segregation reduces the vacancy clustering in these samples. Specific trends for each composition are detailed in the chapters 4 and 5. Overall, chromium content has a major effect on the void nucleation and growth seen in these Fe-Cr model alloys.","abstract_html":"Positron annihilation spectroscopy (PAS) is a powerful, non-destructive technique used to characterize the defect properties of materials. There are two major types of PAS, positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). This work focused on the latter. DBS can be used to gain information on the various types of defects present in a material system and this technique is sensitive to both defect size and defect concentration. Several samples were irradiated at the Advanced Test Reactor at Idaho National Laboratory. These samples were irradiated at temperatures of 300, 450, and 550°C to doses of 0.01 and 0.1dpa (displacements per atom). DBS was used to develop a better understanding of defect formation in Fe-Cr base materials exposed to low doses. Specifically, the goal of this work is to develop a better fundamental understanding of the evolution of nanoscale and sub-nanoscale defect clusters in neutron irradiated Fe-Cr alloys. The results of this work were fairly complicated due to the fact that α’ precipitation could occur in several of these samples. It was found that in samples where early stages of α’ precipitation is possible, lower S-parameters were determined. The S-parameter is indicative of the number and size of vacancy-type defects in the samples, so a lower S-parameter suggests that chromium segregation reduces the vacancy clustering in these samples. Specific trends for each composition are detailed in the chapters 4 and 5. Overall, chromium content has a major effect on the void nucleation and growth seen in these Fe-Cr model alloys.","abstract_has_math":false,"creators":["Romnes, Carly J."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Nuclear, Plasma, Radiolgc Engr","degree_department":null,"school":null,"contributors":["Stubbins, James F","Krogstad, Jessica A"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-03-02T22:15:17Z","date_published":"2020-03-02T22:15:17Z","updated_at":"2026-07-22T22:24:45Z","subjects":["Positron annihilation spectroscopy, iron, chromium, neutron irradiation"],"languages":["en"],"rights":["Copyright 2019 Carly Romnes"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/106389","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Stubbins, James F","Krogstad, Jessica A"]},{"key":"dc:creator","label":"Author","values":["Romnes, Carly J."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-03-02T22:15:17Z","2022-03-03T10:15:13Z","2019-12-10","2019-12"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Nuclear, Plasma, Radiolgc 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":["Positron annihilation spectroscopy, iron, chromium, neutron irradiation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2019 Carly Romnes"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/106389"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Positron annihilation spectroscopy (PAS) is a powerful, non-destructive technique used to characterize the defect properties of materials. There are two major types of PAS, positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). This work focused on the latter. DBS can be used to gain information on the various types of defects present in a material system and this technique is sensitive to both defect size and defect concentration. Several samples were irradiated at the Advanced Test Reactor at Idaho National Laboratory. These samples were irradiated at temperatures of 300, 450, and 550°C to doses of 0.01 and 0.1dpa (displacements per atom). DBS was used to develop a better understanding of defect formation in Fe-Cr base materials exposed to low doses. Specifically, the goal of this work is to develop a better fundamental understanding of the evolution of nanoscale and sub-nanoscale defect clusters in neutron irradiated Fe-Cr alloys. The results of this work were fairly complicated due to the fact that α’ precipitation could occur in several of these samples. It was found that in samples where early stages of α’ precipitation is possible, lower S-parameters were determined. The S-parameter is indicative of the number and size of vacancy-type defects in the samples, so a lower S-parameter suggests that chromium segregation reduces the vacancy clustering in these samples. Specific trends for each composition are detailed in the chapters 4 and 5. Overall, chromium content has a major effect on the void nucleation and growth seen in these Fe-Cr model alloys.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Carly Romnes, accepted the attached license on 2019-12-09 at 17:58.","The student, Carly Romnes, submitted this Thesis for approval on 2019-12-09 at 17:59.","This Thesis was approved for publication on 2019-12-10 at 08:28.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14768 on 2020-02-28 at 17:24:13","Made available in DSpace on 2020-03-02T22:15:17Z (GMT). No. of bitstreams: 2 ROMNES-THESIS-2019.pdf: 1794535 bytes, checksum: 4ea169f09378f8f91eedd0a65404bc16 (MD5) LICENSE.txt: 4209 bytes, checksum: c16d69ddf2828623deb7081e35b5d237 (MD5) Previous issue date: 2019-12-10","Embargo set by: Seth Robbins for item 113931 Lift date: 2022-03-02T22:15:21Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 113931 Lift date: 2022-03-02T22:18:25Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only Restriction Lifted for Item 113931 on 2022-03-03T10:15:13Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Positron annihilation spectroscopy to understand defect formation and evolution in neutron-irradiated Fe-Cr model alloys"]}]}],"canonical_facts":{"dc:contributor":["Stubbins, James F","Krogstad, Jessica A"],"dc:creator":["Romnes, Carly J."],"dc:date":["2020-03-02T22:15:17Z","2022-03-03T10:15:13Z","2019-12-10","2019-12"],"dc:description":["Positron annihilation spectroscopy (PAS) is a powerful, non-destructive technique used to characterize the defect properties of materials. There are two major types of PAS, positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). This work focused on the latter. DBS can be used to gain information on the various types of defects present in a material system and this technique is sensitive to both defect size and defect concentration. Several samples were irradiated at the Advanced Test Reactor at Idaho National Laboratory. These samples were irradiated at temperatures of 300, 450, and 550°C to doses of 0.01 and 0.1dpa (displacements per atom). DBS was used to develop a better understanding of defect formation in Fe-Cr base materials exposed to low doses. Specifically, the goal of this work is to develop a better fundamental understanding of the evolution of nanoscale and sub-nanoscale defect clusters in neutron irradiated Fe-Cr alloys. The results of this work were fairly complicated due to the fact that α’ precipitation could occur in several of these samples. It was found that in samples where early stages of α’ precipitation is possible, lower S-parameters were determined. The S-parameter is indicative of the number and size of vacancy-type defects in the samples, so a lower S-parameter suggests that chromium segregation reduces the vacancy clustering in these samples. Specific trends for each composition are detailed in the chapters 4 and 5. Overall, chromium content has a major effect on the void nucleation and growth seen in these Fe-Cr model alloys.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-12-01","The student, Carly Romnes, accepted the attached license on 2019-12-09 at 17:58.","The student, Carly Romnes, submitted this Thesis for approval on 2019-12-09 at 17:59.","This Thesis was approved for publication on 2019-12-10 at 08:28.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14768 on 2020-02-28 at 17:24:13","Made available in DSpace on 2020-03-02T22:15:17Z (GMT). No. of bitstreams: 2 ROMNES-THESIS-2019.pdf: 1794535 bytes, checksum: 4ea169f09378f8f91eedd0a65404bc16 (MD5) LICENSE.txt: 4209 bytes, checksum: c16d69ddf2828623deb7081e35b5d237 (MD5) Previous issue date: 2019-12-10","Embargo set by: Seth Robbins for item 113931 Lift date: 2022-03-02T22:15:21Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 113931 Lift date: 2022-03-02T22:18:25Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only Restriction Lifted for Item 113931 on 2022-03-03T10:15:13Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/106389"],"dc:language":["en"],"dc:rights":["Copyright 2019 Carly Romnes"],"dc:subject":["Positron annihilation spectroscopy, iron, chromium, neutron irradiation"],"dc:title":["Positron annihilation spectroscopy to understand defect formation and evolution in neutron-irradiated Fe-Cr model alloys"],"dc:type":["text"],"thesis:degree_discipline":["Nuclear, Plasma, Radiolgc Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:45Z"}