\"Oxidation behavior has restricted the development of ZrB₂-based ceramics for aerospace and hypersonic flight vehicles applications. The research presented in this dissertation focuses on the effect of transition metal (TM) additives on oxidation behavior of ZrB₂ ceramics. In the first stage of the research, the effect of Nb additions on the morphology of the oxide particles and stability of the protective B₂O₃ glassy layer, which formed on the top surface during oxidation, was investigated. Addition of Nb increased the thickness of the glassy layer and, as a result, improved the oxidation resistance of ZrB₂ after oxidation at 1500⁰C. Next, the oxidation behavior of nominally pure ZrB₂ and (Zr,W)B₂ after oxidation at temperatures ranging from 800 to 1600⁰C was studied. Two oxidation stages before and after significant evaporation of B₂O₃ at about 1100⁰C were recognized for nominally pure ZrB₂. Higher stability for the WO₃-B₂O₃ glassy layer compared to pure B₂O₃ resulted in a shift in the onset of the second oxidation regime toward higher temperatures for (Zr,W)₂ specimens and resulted in higher oxidation resistance for (Zr,W)B₂ compared to nominally pure ZrB₂. In the third stage of the research, the effects of TM-oxides such as WO₃, Nb₂O₅, or ZrO₂ on weight loss and structure of B₂O₃ glasses was studied. Thermogravimetric analysis performed on (TM-oxide)-B₂O₃ glasses indicated that TM-oxide additions reduced the evaporation of B₂O₃. Since no change in the structure of the glasses was detected, it was concluded that the increased stability of (TM-oxide)-B₂O₃ glasses compared to pure B₂O₃ was due to the lower activity of B₂O₃ in (TM-oxide)-B₂O₃glasses. Finally, comparison of the effects of W, Mo, or Nb on oxidation behavior of ZrB₂ at 1600⁰ showed that Mo and Nb were the most effective additives for improving the oxidation resistance of ZrB₂\"--Abstract, page iv.
","abstract_html":"<p>"Oxidation behavior has restricted the development of ZrB₂-based ceramics for aerospace and hypersonic flight vehicles applications. The research presented in this dissertation focuses on the effect of transition metal (TM) additives on oxidation behavior of ZrB₂ ceramics. In the first stage of the research, the effect of Nb additions on the morphology of the oxide particles and stability of the protective B₂O₃ glassy layer, which formed on the top surface during oxidation, was investigated. Addition of Nb increased the thickness of the glassy layer and, as a result, improved the oxidation resistance of ZrB₂ after oxidation at 1500⁰C. Next, the oxidation behavior of nominally pure ZrB₂ and (Zr,W)B₂ after oxidation at temperatures ranging from 800 to 1600⁰C was studied. Two oxidation stages before and after significant evaporation of B₂O₃ at about 1100⁰C were recognized for nominally pure ZrB₂. Higher stability for the WO₃-B₂O₃ glassy layer compared to pure B₂O₃ resulted in a shift in the onset of the second oxidation regime toward higher temperatures for (Zr,W)₂ specimens and resulted in higher oxidation resistance for (Zr,W)B₂ compared to nominally pure ZrB₂. In the third stage of the research, the effects of TM-oxides such as WO₃, Nb₂O₅, or ZrO₂ on weight loss and structure of B₂O₃ glasses was studied. Thermogravimetric analysis performed on (TM-oxide)-B₂O₃ glasses indicated that TM-oxide additions reduced the evaporation of B₂O₃. Since no change in the structure of the glasses was detected, it was concluded that the increased stability of (TM-oxide)-B₂O₃ glasses compared to pure B₂O₃ was due to the lower activity of B₂O₃ in (TM-oxide)-B₂O₃glasses. Finally, comparison of the effects of W, Mo, or Nb on oxidation behavior of ZrB₂ at 1600⁰ showed that Mo and Nb were the most effective additives for improving the oxidation resistance of ZrB₂"--Abstract, page iv.</p>","abstract_has_math":false,"creators":["Kazemzadeh Dehdashti, Maryam"],"institution":"Missouri University of Science and Technology","degree_name":"Ph. D. in Materials Science and Engineering","degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-02-10T08:00:00Z","date_published":"2016-02-10T08:00:00Z","updated_at":"2026-07-24T03:20:02Z","subjects":["Ultra-high Temperature Ceramics","Zirconium diboride","Materials Science and Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/2336","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Kazemzadeh Dehdashti, Maryam"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2016-02-10T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation - Open Access"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. D. in Materials Science and Engineering"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Missouri University of Science and Technology"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Ultra-high Temperature Ceramics","Zirconium diboride","Materials Science and Engineering"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/2336"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"Oxidation behavior has restricted the development of ZrB₂-based ceramics for aerospace and hypersonic flight vehicles applications. The research presented in this dissertation focuses on the effect of transition metal (TM) additives on oxidation behavior of ZrB₂ ceramics. In the first stage of the research, the effect of Nb additions on the morphology of the oxide particles and stability of the protective B₂O₃ glassy layer, which formed on the top surface during oxidation, was investigated. Addition of Nb increased the thickness of the glassy layer and, as a result, improved the oxidation resistance of ZrB₂ after oxidation at 1500⁰C. Next, the oxidation behavior of nominally pure ZrB₂ and (Zr,W)B₂ after oxidation at temperatures ranging from 800 to 1600⁰C was studied. Two oxidation stages before and after significant evaporation of B₂O₃ at about 1100⁰C were recognized for nominally pure ZrB₂. Higher stability for the WO₃-B₂O₃ glassy layer compared to pure B₂O₃ resulted in a shift in the onset of the second oxidation regime toward higher temperatures for (Zr,W)₂ specimens and resulted in higher oxidation resistance for (Zr,W)B₂ compared to nominally pure ZrB₂. In the third stage of the research, the effects of TM-oxides such as WO₃, Nb₂O₅, or ZrO₂ on weight loss and structure of B₂O₃ glasses was studied. Thermogravimetric analysis performed on (TM-oxide)-B₂O₃ glasses indicated that TM-oxide additions reduced the evaporation of B₂O₃. Since no change in the structure of the glasses was detected, it was concluded that the increased stability of (TM-oxide)-B₂O₃ glasses compared to pure B₂O₃ was due to the lower activity of B₂O₃ in (TM-oxide)-B₂O₃glasses. Finally, comparison of the effects of W, Mo, or Nb on oxidation behavior of ZrB₂ at 1600⁰ showed that Mo and Nb were the most effective additives for improving the oxidation resistance of ZrB₂\"--Abstract, page iv.
"]},{"key":"dc:title","label":"Title","values":["Improving the oxidation resistance of diboride-based ceramics"]}]}],"canonical_facts":{"dc:creator":["Kazemzadeh Dehdashti, Maryam"],"dc:date.available":["2016-02-10T08:00:00Z"],"dc:description.abstract":["\"Oxidation behavior has restricted the development of ZrB₂-based ceramics for aerospace and hypersonic flight vehicles applications. The research presented in this dissertation focuses on the effect of transition metal (TM) additives on oxidation behavior of ZrB₂ ceramics. In the first stage of the research, the effect of Nb additions on the morphology of the oxide particles and stability of the protective B₂O₃ glassy layer, which formed on the top surface during oxidation, was investigated. Addition of Nb increased the thickness of the glassy layer and, as a result, improved the oxidation resistance of ZrB₂ after oxidation at 1500⁰C. Next, the oxidation behavior of nominally pure ZrB₂ and (Zr,W)B₂ after oxidation at temperatures ranging from 800 to 1600⁰C was studied. Two oxidation stages before and after significant evaporation of B₂O₃ at about 1100⁰C were recognized for nominally pure ZrB₂. Higher stability for the WO₃-B₂O₃ glassy layer compared to pure B₂O₃ resulted in a shift in the onset of the second oxidation regime toward higher temperatures for (Zr,W)₂ specimens and resulted in higher oxidation resistance for (Zr,W)B₂ compared to nominally pure ZrB₂. In the third stage of the research, the effects of TM-oxides such as WO₃, Nb₂O₅, or ZrO₂ on weight loss and structure of B₂O₃ glasses was studied. Thermogravimetric analysis performed on (TM-oxide)-B₂O₃ glasses indicated that TM-oxide additions reduced the evaporation of B₂O₃. Since no change in the structure of the glasses was detected, it was concluded that the increased stability of (TM-oxide)-B₂O₃ glasses compared to pure B₂O₃ was due to the lower activity of B₂O₃ in (TM-oxide)-B₂O₃glasses. Finally, comparison of the effects of W, Mo, or Nb on oxidation behavior of ZrB₂ at 1600⁰ showed that Mo and Nb were the most effective additives for improving the oxidation resistance of ZrB₂\"--Abstract, page iv.
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/2336"],"dc:subject":["Ultra-high Temperature Ceramics","Zirconium diboride","Materials Science and Engineering"],"dc:title":["Improving the oxidation resistance of diboride-based ceramics"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Materials Science and Engineering"],"thesis:institution_name":["Missouri University of Science and Technology"]},"updated_at":"2026-07-24T03:20:02Z"}