{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/99261"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/99261","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Synthesis, characterization, and properties of carbide dispersion-strengthened tungsten alloys for use as a plasma-facing material in nuclear fusion reactors","abstract":"Tungsten is the material of choice for plasma-facing components in future plasma-burning fusion reactors because of its high melting point, high sputter threshold, and low hydrogenic species retention. However, tungsten is an intrinsically brittle material, displaying no room temperature ductility and only exhibiting non-brittle failure at temperatures above 400 C. In addition to its limited ductility, tungsten’s high melting point and low recrystallization temperature pose complications during fabrication. Traditional synthesis routes tend to result in non-fully dense samples with coarse-grained microstructures. As a consequence, there is a desire for a fine-grained, fully-dense tungsten material that exhibits enhanced ductility. Tungsten is embrittled by impurity oxygen atoms residing at grain boundaries. It is theorized that by microalloying tungsten with transition metal carbides that capture the oxygen atoms, the impurity distribution can be altered to beneficially impact the mechanical properties. Through the advent of advanced powder processing techniques such as Spark plasma sintering, dense, fine-grained tungsten samples can be developed with these microalloyed microstructures. Spark plasma sintering is a powder compaction technique that provides high pressure and heating rates, allowing for a lower final temperature and hold time for compaction. In SPS, a strong electrical current is fed through the powder and die to heat the powder. An applied uniaxial force combines to compress the powder to a solid compact, leading to fully dense materials at lower temperatures as compared to conventional sintering. In this work, spark plasma sintering is employed to develop tungsten materials alloyed with tantalum carbide, titanium carbide, or zirconium carbide. Samples are fabricated with varying compositions of added carbides (from 0.5-10 wt.%), and the sintering process results in >90% dense samples with grains <10 μm in size. Compositional studies indicate the formation of tungsten carbide and transition-metal-oxide phases after sintering. As the amount of added second phase powder increased, the hardness increased and grain size decreased. Finally, samples alloyed with 1.0 wt.% zirconium carbide may be able to resist recrystallization. Exposures to low fluence deuterium ion irradiation showed possible re-organization of the surface bonding, but limited surface structuring. Under high fluence helium and hydrogen irradiation, significant nanostructuring was observed in cracks and non-fully formed grains, an unexpected result given the temperature and fluence regimes studied, which may be attributed to slight surface chemistry changes. Finally, initial investigations indicate increased deuterium retention in alloyed samples as compared to pure tungsten. These results offer a first study of the behavior of various dispersion-strengthened tungsten alloys under ion irradiation that sufficiently motivate further investigation of these materials for plasma-facing environments.","abstract_html":"Tungsten is the material of choice for plasma-facing components in future plasma-burning fusion reactors because of its high melting point, high sputter threshold, and low hydrogenic species retention. However, tungsten is an intrinsically brittle material, displaying no room temperature ductility and only exhibiting non-brittle failure at temperatures above 400 C. In addition to its limited ductility, tungsten’s high melting point and low recrystallization temperature pose complications during fabrication. Traditional synthesis routes tend to result in non-fully dense samples with coarse-grained microstructures. As a consequence, there is a desire for a fine-grained, fully-dense tungsten material that exhibits enhanced ductility. Tungsten is embrittled by impurity oxygen atoms residing at grain boundaries. It is theorized that by microalloying tungsten with transition metal carbides that capture the oxygen atoms, the impurity distribution can be altered to beneficially impact the mechanical properties. Through the advent of advanced powder processing techniques such as Spark plasma sintering, dense, fine-grained tungsten samples can be developed with these microalloyed microstructures. Spark plasma sintering is a powder compaction technique that provides high pressure and heating rates, allowing for a lower final temperature and hold time for compaction. In SPS, a strong electrical current is fed through the powder and die to heat the powder. An applied uniaxial force combines to compress the powder to a solid compact, leading to fully dense materials at lower temperatures as compared to conventional sintering. In this work, spark plasma sintering is employed to develop tungsten materials alloyed with tantalum carbide, titanium carbide, or zirconium carbide. Samples are fabricated with varying compositions of added carbides (from 0.5-10 wt.%), and the sintering process results in &gt;90% dense samples with grains &lt;10 μm in size. Compositional studies indicate the formation of tungsten carbide and transition-metal-oxide phases after sintering. As the amount of added second phase powder increased, the hardness increased and grain size decreased. Finally, samples alloyed with 1.0 wt.% zirconium carbide may be able to resist recrystallization. Exposures to low fluence deuterium ion irradiation showed possible re-organization of the surface bonding, but limited surface structuring. Under high fluence helium and hydrogen irradiation, significant nanostructuring was observed in cracks and non-fully formed grains, an unexpected result given the temperature and fluence regimes studied, which may be attributed to slight surface chemistry changes. Finally, initial investigations indicate increased deuterium retention in alloyed samples as compared to pure tungsten. These results offer a first study of the behavior of various dispersion-strengthened tungsten alloys under ion irradiation that sufficiently motivate further investigation of these materials for plasma-facing environments.","abstract_has_math":false,"creators":["Lang, Eric Joseph"],"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":["Allain, Jean Paul","Krogstad, Jessica A."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-03-13T15:28:44Z","date_published":"2018-03-13T15:28:44Z","updated_at":"2026-07-22T22:24:37Z","subjects":["Tungsten","Spark Plasma Sintering"],"languages":["en"],"rights":["Copyright 2017 Eric Lang"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/99261","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Allain, Jean Paul","Krogstad, Jessica A."]},{"key":"dc:creator","label":"Author","values":["Lang, Eric Joseph"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-03-13T15:28:44Z","2020-03-14T09:15:31Z","2017-12-13","2017-12"]},{"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":["Tungsten","Spark Plasma Sintering"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2017 Eric Lang"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/99261"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Tungsten is the material of choice for plasma-facing components in future plasma-burning fusion reactors because of its high melting point, high sputter threshold, and low hydrogenic species retention. However, tungsten is an intrinsically brittle material, displaying no room temperature ductility and only exhibiting non-brittle failure at temperatures above 400 C. In addition to its limited ductility, tungsten’s high melting point and low recrystallization temperature pose complications during fabrication. Traditional synthesis routes tend to result in non-fully dense samples with coarse-grained microstructures. As a consequence, there is a desire for a fine-grained, fully-dense tungsten material that exhibits enhanced ductility. Tungsten is embrittled by impurity oxygen atoms residing at grain boundaries. It is theorized that by microalloying tungsten with transition metal carbides that capture the oxygen atoms, the impurity distribution can be altered to beneficially impact the mechanical properties. Through the advent of advanced powder processing techniques such as Spark plasma sintering, dense, fine-grained tungsten samples can be developed with these microalloyed microstructures. Spark plasma sintering is a powder compaction technique that provides high pressure and heating rates, allowing for a lower final temperature and hold time for compaction. In SPS, a strong electrical current is fed through the powder and die to heat the powder. An applied uniaxial force combines to compress the powder to a solid compact, leading to fully dense materials at lower temperatures as compared to conventional sintering. In this work, spark plasma sintering is employed to develop tungsten materials alloyed with tantalum carbide, titanium carbide, or zirconium carbide. Samples are fabricated with varying compositions of added carbides (from 0.5-10 wt.%), and the sintering process results in >90% dense samples with grains <10 μm in size. Compositional studies indicate the formation of tungsten carbide and transition-metal-oxide phases after sintering. As the amount of added second phase powder increased, the hardness increased and grain size decreased. Finally, samples alloyed with 1.0 wt.% zirconium carbide may be able to resist recrystallization. Exposures to low fluence deuterium ion irradiation showed possible re-organization of the surface bonding, but limited surface structuring. Under high fluence helium and hydrogen irradiation, significant nanostructuring was observed in cracks and non-fully formed grains, an unexpected result given the temperature and fluence regimes studied, which may be attributed to slight surface chemistry changes. Finally, initial investigations indicate increased deuterium retention in alloyed samples as compared to pure tungsten. These results offer a first study of the behavior of various dispersion-strengthened tungsten alloys under ion irradiation that sufficiently motivate further investigation of these materials for plasma-facing environments.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-12-01","The student, Eric Lang, accepted the attached license on 2017-12-13 at 10:24.","The student, Eric Lang, submitted this Thesis for approval on 2017-12-13 at 10:55.","This Thesis was approved for publication on 2017-12-13 at 15:45.","DSpace SAF Submission Ingestion Package generated from Vireo submission #11967 on 2018-03-13 at 09:57:51","Made available in DSpace on 2018-03-13T15:28:44Z (GMT). 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However, tungsten is an intrinsically brittle material, displaying no room temperature ductility and only exhibiting non-brittle failure at temperatures above 400 C. In addition to its limited ductility, tungsten’s high melting point and low recrystallization temperature pose complications during fabrication. Traditional synthesis routes tend to result in non-fully dense samples with coarse-grained microstructures. As a consequence, there is a desire for a fine-grained, fully-dense tungsten material that exhibits enhanced ductility. Tungsten is embrittled by impurity oxygen atoms residing at grain boundaries. It is theorized that by microalloying tungsten with transition metal carbides that capture the oxygen atoms, the impurity distribution can be altered to beneficially impact the mechanical properties. Through the advent of advanced powder processing techniques such as Spark plasma sintering, dense, fine-grained tungsten samples can be developed with these microalloyed microstructures. Spark plasma sintering is a powder compaction technique that provides high pressure and heating rates, allowing for a lower final temperature and hold time for compaction. In SPS, a strong electrical current is fed through the powder and die to heat the powder. An applied uniaxial force combines to compress the powder to a solid compact, leading to fully dense materials at lower temperatures as compared to conventional sintering. In this work, spark plasma sintering is employed to develop tungsten materials alloyed with tantalum carbide, titanium carbide, or zirconium carbide. Samples are fabricated with varying compositions of added carbides (from 0.5-10 wt.%), and the sintering process results in >90% dense samples with grains <10 μm in size. Compositional studies indicate the formation of tungsten carbide and transition-metal-oxide phases after sintering. As the amount of added second phase powder increased, the hardness increased and grain size decreased. Finally, samples alloyed with 1.0 wt.% zirconium carbide may be able to resist recrystallization. Exposures to low fluence deuterium ion irradiation showed possible re-organization of the surface bonding, but limited surface structuring. Under high fluence helium and hydrogen irradiation, significant nanostructuring was observed in cracks and non-fully formed grains, an unexpected result given the temperature and fluence regimes studied, which may be attributed to slight surface chemistry changes. Finally, initial investigations indicate increased deuterium retention in alloyed samples as compared to pure tungsten. These results offer a first study of the behavior of various dispersion-strengthened tungsten alloys under ion irradiation that sufficiently motivate further investigation of these materials for plasma-facing environments.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-12-01","The student, Eric Lang, accepted the attached license on 2017-12-13 at 10:24.","The student, Eric Lang, submitted this Thesis for approval on 2017-12-13 at 10:55.","This Thesis was approved for publication on 2017-12-13 at 15:45.","DSpace SAF Submission Ingestion Package generated from Vireo submission #11967 on 2018-03-13 at 09:57:51","Made available in DSpace on 2018-03-13T15:28:44Z (GMT). No. of bitstreams: 2 LANG-THESIS-2017.pdf: 45607678 bytes, checksum: 8e93fddfa9b932c42b2848643a14c7ce (MD5) LICENSE.txt: 4206 bytes, checksum: 8cc95c06cc1ea1ec61106241abbae578 (MD5) Previous issue date: 2017-12-13","Embargo set by: Seth Robbins for item 105225 Lift date: 2020-03-13T15:28:52Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only Restriction Lifted for Item 105225 on 2020-03-14T09:15:31Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/99261"],"dc:language":["en"],"dc:rights":["Copyright 2017 Eric Lang"],"dc:subject":["Tungsten","Spark Plasma Sintering"],"dc:title":["Synthesis, characterization, and properties of carbide dispersion-strengthened tungsten alloys for use as a plasma-facing material in nuclear fusion reactors"],"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":"2026-07-22T22:24:37Z"}