{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/129494"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/129494","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Developing fully mixed oxidation-resistant hafnium aluminum diboride hard coatings deposited by low temperature CVD","abstract":"Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-05-01","abstract_html":"Submission published under a 24 month embargo labeled &#x27;U of I Access&#x27;, the embargo will last until 2027-05-01","abstract_has_math":false,"creators":["Shrivastav, Samyukta"],"institution":"University of Illinois Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Abelson, John R","Krogstad, Jessica A","Girolami, Gregory S","Bellon, Pascal","Shoemaker, Daniel P"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-02-21","date_published":"2025-02-21","updated_at":"2026-07-22T22:25:05Z","subjects":["Hafnium aluminum diboride","Ceramics thin films","Materials Characterization"],"languages":["en","eng"],"rights":["Copyright 2025 Samyukta Shrivastav"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/129494","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Abelson, John R","Krogstad, Jessica A","Girolami, Gregory S","Bellon, Pascal","Shoemaker, Daniel P"]},{"key":"dc:creator","label":"Author","values":["Shrivastav, Samyukta"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-02-21","2025-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"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 Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Hafnium aluminum diboride","Ceramics thin films","Materials Characterization"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en","eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2025 Samyukta Shrivastav"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/129494"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-05-01","The student, Samyukta Shrivastav, accepted the attached license on 2025-02-18 at 20:13.","The student, Samyukta Shrivastav, submitted this Dissertation for approval on 2025-02-18 at 20:31.","This Dissertation was approved for publication on 2025-02-21 at 16:13.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21646 on 2025-10-19 at 19:14:16","Hard protective coatings are often made from oxides, carbides, nitrides and borides. However, an all-rounder compound with ubiquitous applications usually does not exist. Alloying with other elements is often needed to improve properties such as oxidation resistance or fracture toughness. Thus, this dissertation explores the microstructure-property space of novel HfB2-AlB2 alloy coating system. Hf1-xAlxBy alloy thin films are deposited at ≤ 300°C by chemical vapor deposition from two volatile precursors, Hf(BH4)4 and AlH3N(CH3)3. This method allows for control over a wide range of Al content x, here 0.41 to 0.78, which controls the as-deposited microstructure. The as-deposited state is nanocrystalline with equiaxed grains of diameter ~ 5 nm, for 0.40 < x < 0.66. Al contents between 0.41-0.66 afford a solid solution with no resolvable segregation into regions of HfB2, AlB2, or Al. Excess Al (x > 0.66) generates an amorphous phase, and Al-rich domains are present in a film with x = 0.78. Different as-deposited microstructures exhibit different oxidation behaviors and mechanical response. After annealing at 600°C for 8 hours in air, unalloyed HfBy is consumed to form a porous oxide; by contrast, the Hf1-xAlxBy alloy forms a uniform and much thinner oxide. Upon annealing at 700°C for 1 hour in air, the grain size and phase are stable, and the alloy film does not crack or delaminate from the substrate. An AlOx layer, ~ 22-50 nm thick depending on the composition x, forms on the surface and slows the rate of further oxidation. Annealing coatings with excess aluminum (x > 0.66) at 700 °C results in the surface passivation being breached by the formation of aluminum borate, consistent with literature reports of borate formation at ≥ 700 °C. Hardness, Young’s modulus, plasticity index, and fracture toughness for films with x = 0 to 0.78 are determined using cube corner nanoindentation. A hardness of ~ 20 GPa and plasticity index of ~ 0.33 are maintained for aluminum contents x = 0 to 0.66; for larger values the hardness declines and the plasticity increases. The fracture toughness increases as a function of aluminum content, with no cracks detectable for x ≥ 0.66. For engineering applications that require a good combination of hardness, toughness, and high temperature oxidation resistance, coatings with 0.41 ≤ x ≤ 0.66 are expected to perform well. Therefore, Hf1-xAlxBy films are excellent candidates for applications that require a hard, chemically resistant coating at temperatures below 700°C."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Developing fully mixed oxidation-resistant hafnium aluminum diboride hard coatings deposited by low temperature CVD"]}]}],"canonical_facts":{"dc:contributor":["Abelson, John R","Krogstad, Jessica A","Girolami, Gregory S","Bellon, Pascal","Shoemaker, Daniel P"],"dc:creator":["Shrivastav, Samyukta"],"dc:date":["2025-02-21","2025-05"],"dc:description":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-05-01","The student, Samyukta Shrivastav, accepted the attached license on 2025-02-18 at 20:13.","The student, Samyukta Shrivastav, submitted this Dissertation for approval on 2025-02-18 at 20:31.","This Dissertation was approved for publication on 2025-02-21 at 16:13.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21646 on 2025-10-19 at 19:14:16","Hard protective coatings are often made from oxides, carbides, nitrides and borides. However, an all-rounder compound with ubiquitous applications usually does not exist. Alloying with other elements is often needed to improve properties such as oxidation resistance or fracture toughness. Thus, this dissertation explores the microstructure-property space of novel HfB2-AlB2 alloy coating system. Hf1-xAlxBy alloy thin films are deposited at ≤ 300°C by chemical vapor deposition from two volatile precursors, Hf(BH4)4 and AlH3N(CH3)3. This method allows for control over a wide range of Al content x, here 0.41 to 0.78, which controls the as-deposited microstructure. The as-deposited state is nanocrystalline with equiaxed grains of diameter ~ 5 nm, for 0.40 < x < 0.66. Al contents between 0.41-0.66 afford a solid solution with no resolvable segregation into regions of HfB2, AlB2, or Al. Excess Al (x > 0.66) generates an amorphous phase, and Al-rich domains are present in a film with x = 0.78. Different as-deposited microstructures exhibit different oxidation behaviors and mechanical response. After annealing at 600°C for 8 hours in air, unalloyed HfBy is consumed to form a porous oxide; by contrast, the Hf1-xAlxBy alloy forms a uniform and much thinner oxide. Upon annealing at 700°C for 1 hour in air, the grain size and phase are stable, and the alloy film does not crack or delaminate from the substrate. An AlOx layer, ~ 22-50 nm thick depending on the composition x, forms on the surface and slows the rate of further oxidation. Annealing coatings with excess aluminum (x > 0.66) at 700 °C results in the surface passivation being breached by the formation of aluminum borate, consistent with literature reports of borate formation at ≥ 700 °C. Hardness, Young’s modulus, plasticity index, and fracture toughness for films with x = 0 to 0.78 are determined using cube corner nanoindentation. A hardness of ~ 20 GPa and plasticity index of ~ 0.33 are maintained for aluminum contents x = 0 to 0.66; for larger values the hardness declines and the plasticity increases. The fracture toughness increases as a function of aluminum content, with no cracks detectable for x ≥ 0.66. For engineering applications that require a good combination of hardness, toughness, and high temperature oxidation resistance, coatings with 0.41 ≤ x ≤ 0.66 are expected to perform well. Therefore, Hf1-xAlxBy films are excellent candidates for applications that require a hard, chemically resistant coating at temperatures below 700°C."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/129494"],"dc:language":["en","eng"],"dc:rights":["Copyright 2025 Samyukta Shrivastav"],"dc:subject":["Hafnium aluminum diboride","Ceramics thin films","Materials Characterization"],"dc:title":["Developing fully mixed oxidation-resistant hafnium aluminum diboride hard coatings deposited by low temperature CVD"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Materials Science & Engr"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:05Z"}