\"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated.
Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB₂. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB₂. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B₆.₅C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB₂, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 200⁰C suggested that the stoichiometry of the boron carbide additives did not significantly affect (kth) of HfB₂-BₓC composites. The improved sinterability and the high (kth) (~100 W/m-K at 300K and ~90 W/m-K at 1000⁰C) of HfB₂-BₓC ceramics make them excellent candidates for isotopically enriched reactor control materials\"--Abstract, page iv.
","abstract_html":"<p>"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated.</p> <p>Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB₂. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB₂. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B₆.₅C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB₂, respectively, which facilitate densification. Evaluation of the thermal conductivity (k<sub>th</sub>) between room temperature and 200⁰C suggested that the stoichiometry of the boron carbide additives did not significantly affect (k<sub>th</sub>) of HfB₂-BₓC composites. The improved sinterability and the high (k<sub>th</sub>) (~100 W/m-K at 300K and ~90 W/m-K at 1000⁰C) of HfB₂-BₓC ceramics make them excellent candidates for isotopically enriched reactor control materials"--Abstract, page iv.</p>","abstract_has_math":false,"creators":["Brown-Shaklee, Harlan J."],"institution":"Missouri University of Science and Technology","degree_name":"Ph. D. in Ceramic 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":"2026-07-24T03:19:30Z","subjects":["Band gap","Ceramic Materials"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/65","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Brown-Shaklee, Harlan J."]}]},{"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 Ceramic 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":["Band gap","Ceramic Materials"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/65"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated.
Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB₂. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB₂. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B₆.₅C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB₂, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 200⁰C suggested that the stoichiometry of the boron carbide additives did not significantly affect (kth) of HfB₂-BₓC composites. The improved sinterability and the high (kth) (~100 W/m-K at 300K and ~90 W/m-K at 1000⁰C) of HfB₂-BₓC ceramics make them excellent candidates for isotopically enriched reactor control materials\"--Abstract, page iv.
"]},{"key":"dc:title","label":"Title","values":["Processing and characterization of boron carbide-hafnium diboride ceramics"]}]}],"canonical_facts":{"dc:creator":["Brown-Shaklee, Harlan J."],"dc:date.available":["2016-02-10T08:00:00Z"],"dc:description.abstract":["\"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated.
Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB₂. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB₂. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B₆.₅C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB₂, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 200⁰C suggested that the stoichiometry of the boron carbide additives did not significantly affect (kth) of HfB₂-BₓC composites. The improved sinterability and the high (kth) (~100 W/m-K at 300K and ~90 W/m-K at 1000⁰C) of HfB₂-BₓC ceramics make them excellent candidates for isotopically enriched reactor control materials\"--Abstract, page iv.
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/65"],"dc:subject":["Band gap","Ceramic Materials"],"dc:title":["Processing and characterization of boron carbide-hafnium diboride ceramics"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Ceramic Engineering"],"thesis:institution_name":["Missouri University of Science and Technology"]},"updated_at":"2026-07-24T03:19:30Z"}