{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/71711"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/71711","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Investigation of the Lanthanide Sesquioxides as High Temperature Transformation Toughening Agents","abstract":"The lanthanide sesquioxides were investigated as possible high temperature transformation toughening agents. Specifically, the monoclinic to cubic (B $\\Rightarrow$ C) transformation in Gd$\\sb2$O$\\sb3$ and Tb$\\sb2$O$\\sb3$ was examined. This transformation involves an 8-10% volume expansion and a shape change ($\\Delta\\beta$) of $\\sim$10$\\sp\\circ$. Techniques used in the investigation of the transformation behavior included: grinding, cooling in liquid nitrogen, DTA, dilatometry, ambient and high temperature Vickers indentation, and notched-beam three point flexure.","abstract_html":"The lanthanide sesquioxides were investigated as possible high temperature transformation toughening agents. Specifically, the monoclinic to cubic (B $\\Rightarrow$ C) transformation in Gd$\\sb2$O$\\sb3$ and Tb$\\sb2$O$\\sb3$ was examined. This transformation involves an 8-10% volume expansion and a shape change (<span class=\"etd-inline-math\">\\Delta&beta;</span>) of $\\sim$10$\\sp\\circ$. Techniques used in the investigation of the transformation behavior included: grinding, cooling in liquid nitrogen, DTA, dilatometry, ambient and high temperature Vickers indentation, and notched-beam three point flexure.","abstract_has_math":true,"creators":["Jero, Paul Daniel"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Ceramics Engineering","degree_department":null,"school":null,"contributors":["Kriven, W.M.,"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-16T19:16:59Z","date_published":"2014-12-16T19:16:59Z","updated_at":"2026-07-22T22:26:05Z","subjects":["Engineering, Materials Science"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8823158"],"render_values":[{"text":"(UMI)AAI8823158","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/71711","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Kriven, W.M.,"]},{"key":"dc:creator","label":"Author","values":["Jero, Paul Daniel"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-16T19:16:59Z","10000-01-01","1988"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Ceramics Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"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":["Engineering, Materials Science"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/71711","(UMI)AAI8823158"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The lanthanide sesquioxides were investigated as possible high temperature transformation toughening agents. Specifically, the monoclinic to cubic (B $\\Rightarrow$ C) transformation in Gd$\\sb2$O$\\sb3$ and Tb$\\sb2$O$\\sb3$ was examined. This transformation involves an 8-10% volume expansion and a shape change ($\\Delta\\beta$) of $\\sim$10$\\sp\\circ$. Techniques used in the investigation of the transformation behavior included: grinding, cooling in liquid nitrogen, DTA, dilatometry, ambient and high temperature Vickers indentation, and notched-beam three point flexure.","A distinct change in B $\\Leftrightarrow$ C transformation kinetics occurred on moving from Gd$\\sb2$O$\\sb3$ to Tb$\\sb2$O$\\sb3$. Tb$\\sb2$O$\\sb3$ exhibited a rapid B $\\Rightarrow$ C transformation, whereas Gd$\\sb2$O$\\sb3$ remained in the B phase after high temperature processing. This difference is believed to result from the operation of different transformation mechanisms in these materials. Specifically, the occurrence of a rapid B $\\Rightarrow$ C transformation in Tb$\\sb2$O$\\sb3$ at temperatures as low as 200$\\sp\\circ$C indicates that it can transform by a diffusionless mechanism.","The B $\\Rightarrow$ C transformation in Gd$\\sb2$O$\\sb3$ was not observed, except in a thin surface layer on Gd$\\sb2$O$\\sb3$ specimens which were ground and subsequently annealed at temperatures $\\geq$700$\\sp\\circ$C for extended periods of time. Specimens of pure Tb$\\sb2$O$\\sb3$ fired above 1700$\\sp\\circ$C shattered on cooling through the B $\\Rightarrow$ C transformation. Laser melting and roller quenching, however, resulted in thin flakes which were primarily B phase. Incorporation of the Tb$\\sb2$O$\\sb3$ into a matrix of MgO or 2Tb$\\sb2$O$\\sb2\\cdot$Al$\\sb2$O$\\sb3$ allowed preparation of bulk specimens. Extremely rapid cooling was required in order to retain the Tb$\\sb2$O$\\sb3$ in the high temperature B form. Cooling rate was observed to be the dominant factor in retention of the high temperature form.","The B $\\Rightarrow$ C transformation could not be induced in Tb$\\sb2$O$\\sb3$-MgO specimens at room temperature. Elevated temperatures were required in order to overcome the nucleation barrier to transformation. The B $\\Rightarrow$ C transformation was observed on the fracture surfaces of specimens broken at $\\geq$1075$\\sp\\circ$C. Spontaneous transformation was observed on roughly ground surfaces at 1300$\\sp\\circ$C, and in the bulk at 1400$\\sp\\circ$C. In Tb$\\sb2$O$\\sb3$-Al$\\sb2$O$\\sb3$ specimens, transformation on fracture surfaces was observed at 1150$\\sp\\circ$C and spontaneous surface and bulk transformation at 1300$\\sp\\circ$C. High temperature mechanical testing showed an increase in toughness with temperature in these specimens.","Made available in DSpace on 2014-12-16T19:16:59Z (GMT). No. of bitstreams: 1 8823158.pdf: 9648299 bytes, checksum: 701bf6d32392e0ac357b753594e8728b (MD5) Previous issue date: 1988","Embargo set by: Seth Robbins for item 71877 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","241 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988."]},{"key":"dc:title","label":"Title","values":["Investigation of the Lanthanide Sesquioxides as High Temperature Transformation Toughening Agents"]}]}],"canonical_facts":{"dc:contributor":["Kriven, W.M.,"],"dc:creator":["Jero, Paul Daniel"],"dc:date":["2014-12-16T19:16:59Z","10000-01-01","1988"],"dc:description":["The lanthanide sesquioxides were investigated as possible high temperature transformation toughening agents. Specifically, the monoclinic to cubic (B $\\Rightarrow$ C) transformation in Gd$\\sb2$O$\\sb3$ and Tb$\\sb2$O$\\sb3$ was examined. This transformation involves an 8-10% volume expansion and a shape change ($\\Delta\\beta$) of $\\sim$10$\\sp\\circ$. Techniques used in the investigation of the transformation behavior included: grinding, cooling in liquid nitrogen, DTA, dilatometry, ambient and high temperature Vickers indentation, and notched-beam three point flexure.","A distinct change in B $\\Leftrightarrow$ C transformation kinetics occurred on moving from Gd$\\sb2$O$\\sb3$ to Tb$\\sb2$O$\\sb3$. Tb$\\sb2$O$\\sb3$ exhibited a rapid B $\\Rightarrow$ C transformation, whereas Gd$\\sb2$O$\\sb3$ remained in the B phase after high temperature processing. This difference is believed to result from the operation of different transformation mechanisms in these materials. Specifically, the occurrence of a rapid B $\\Rightarrow$ C transformation in Tb$\\sb2$O$\\sb3$ at temperatures as low as 200$\\sp\\circ$C indicates that it can transform by a diffusionless mechanism.","The B $\\Rightarrow$ C transformation in Gd$\\sb2$O$\\sb3$ was not observed, except in a thin surface layer on Gd$\\sb2$O$\\sb3$ specimens which were ground and subsequently annealed at temperatures $\\geq$700$\\sp\\circ$C for extended periods of time. Specimens of pure Tb$\\sb2$O$\\sb3$ fired above 1700$\\sp\\circ$C shattered on cooling through the B $\\Rightarrow$ C transformation. Laser melting and roller quenching, however, resulted in thin flakes which were primarily B phase. Incorporation of the Tb$\\sb2$O$\\sb3$ into a matrix of MgO or 2Tb$\\sb2$O$\\sb2\\cdot$Al$\\sb2$O$\\sb3$ allowed preparation of bulk specimens. Extremely rapid cooling was required in order to retain the Tb$\\sb2$O$\\sb3$ in the high temperature B form. Cooling rate was observed to be the dominant factor in retention of the high temperature form.","The B $\\Rightarrow$ C transformation could not be induced in Tb$\\sb2$O$\\sb3$-MgO specimens at room temperature. Elevated temperatures were required in order to overcome the nucleation barrier to transformation. The B $\\Rightarrow$ C transformation was observed on the fracture surfaces of specimens broken at $\\geq$1075$\\sp\\circ$C. Spontaneous transformation was observed on roughly ground surfaces at 1300$\\sp\\circ$C, and in the bulk at 1400$\\sp\\circ$C. In Tb$\\sb2$O$\\sb3$-Al$\\sb2$O$\\sb3$ specimens, transformation on fracture surfaces was observed at 1150$\\sp\\circ$C and spontaneous surface and bulk transformation at 1300$\\sp\\circ$C. High temperature mechanical testing showed an increase in toughness with temperature in these specimens.","Made available in DSpace on 2014-12-16T19:16:59Z (GMT). No. of bitstreams: 1 8823158.pdf: 9648299 bytes, checksum: 701bf6d32392e0ac357b753594e8728b (MD5) Previous issue date: 1988","Embargo set by: Seth Robbins for item 71877 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","241 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988."],"dc:identifier":["http://hdl.handle.net/2142/71711","(UMI)AAI8823158"],"dc:subject":["Engineering, Materials Science"],"dc:title":["Investigation of the Lanthanide Sesquioxides as High Temperature Transformation Toughening Agents"],"dc:type":["text"],"thesis:degree_discipline":["Ceramics Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:05Z"}