\"This research focuses on studying the thermal and mechanical properties of novel carbide materials at room and elevated temperatures. The novel carbide materials investigated include zeta phase tantalum carbide (ζ-Ta4C3-x) and a high entropy (Ta,Hf,Nb,Zr)C carbide. The electrical resistivity and thermal conductivity of zeta phase tantalum carbide (~96 wt.%) were measured as 160 ± 4.2 μΩ-cm and 9.6 W/m•K. These are higher and lower (respectively) than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta4C3-x crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any of its carbide constituents with values ranging from 10.7 W/m•K at room temperature to 39.9 W/m•K at 2000°C. The electrical resistivity was higher than any of the carbide constituents ranging from 80.9 μΩ•cm at room temperature to 114.1 μΩ•cm at 800 °C. The electron contribution to thermal conductivity increased with temperature, and the phonon contribution was unaffected by temperature. The strength and fracture toughness of tantalum carbide ceramics (~75 wt.% ζ-Ta4C3-x) were 710 ± 36.5 MPa and 10.2 ± 0.4 MPa· m1/2 at room temperature and decreased to 180 ± 19.7 MPa and 4.7 ± 0.1 MPa· m1/2 at 1600°C. The high aspect ratio grains (along the long axis) appeared to be the critical flaw. A brittle to ductile transition was observed between 1400°C and 1600°C. The ductility was attributed to deformation via kinking and delamination observed in the microstructure at room temperature. ζ-Ta4C3-x was observed to be machinable with traditional tools such as a hacksaw, drill bit, and end mill. The machinability is attributed to cleaving of grains along weakly bonded planes and prevention of crack propagation into the bulk ceramic\"--Abstract, p. iv
","abstract_html":"<p>"This research focuses on studying the thermal and mechanical properties of novel carbide materials at room and elevated temperatures. The novel carbide materials investigated include zeta phase tantalum carbide (ζ-Ta<sub>4</sub>C<sub>3-x</sub>) and a high entropy (Ta,Hf,Nb,Zr)C carbide. The electrical resistivity and thermal conductivity of zeta phase tantalum carbide (~96 wt.%) were measured as 160 ± 4.2 μΩ-cm and 9.6 W/m•K. These are higher and lower (respectively) than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta<sub>4</sub>C<sub>3-x</sub> crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any of its carbide constituents with values ranging from 10.7 W/m•K at room temperature to 39.9 W/m•K at 2000°C. The electrical resistivity was higher than any of the carbide constituents ranging from 80.9 μΩ•cm at room temperature to 114.1 μΩ•cm at 800 °C. The electron contribution to thermal conductivity increased with temperature, and the phonon contribution was unaffected by temperature. The strength and fracture toughness of tantalum carbide ceramics (~75 wt.% ζ-Ta<sub>4</sub>C<sub>3-x</sub>) were 710 ± 36.5 MPa and 10.2 ± 0.4 MPa· m1/2 at room temperature and decreased to 180 ± 19.7 MPa and 4.7 ± 0.1 MPa· m1/2 at 1600°C. The high aspect ratio grains (along the long axis) appeared to be the critical flaw. A brittle to ductile transition was observed between 1400°C and 1600°C. The ductility was attributed to deformation via kinking and delamination observed in the microstructure at room temperature. ζ-Ta<sub>4</sub>C<sub>3-x</sub> was observed to be machinable with traditional tools such as a hacksaw, drill bit, and end mill. The machinability is attributed to cleaving of grains along weakly bonded planes and prevention of crack propagation into the bulk ceramic"--Abstract, p. iv</p>","abstract_has_math":false,"creators":["Schwind, Evan Charles"],"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":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T03:18:18Z","subjects":["High Entropy Carbide","Mechanical Properties","Tantalum Carbide","Thermal Properties","Ultra-High Temperature Ceramics","Zeta Phase","Ceramic Materials","Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/3185","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Schwind, Evan Charles"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"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":["High Entropy Carbide","Mechanical Properties","Tantalum Carbide","Thermal Properties","Ultra-High Temperature Ceramics","Zeta Phase","Ceramic Materials","Engineering"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/3185"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"This research focuses on studying the thermal and mechanical properties of novel carbide materials at room and elevated temperatures. The novel carbide materials investigated include zeta phase tantalum carbide (ζ-Ta4C3-x) and a high entropy (Ta,Hf,Nb,Zr)C carbide. The electrical resistivity and thermal conductivity of zeta phase tantalum carbide (~96 wt.%) were measured as 160 ± 4.2 μΩ-cm and 9.6 W/m•K. These are higher and lower (respectively) than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta4C3-x crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any of its carbide constituents with values ranging from 10.7 W/m•K at room temperature to 39.9 W/m•K at 2000°C. The electrical resistivity was higher than any of the carbide constituents ranging from 80.9 μΩ•cm at room temperature to 114.1 μΩ•cm at 800 °C. The electron contribution to thermal conductivity increased with temperature, and the phonon contribution was unaffected by temperature. The strength and fracture toughness of tantalum carbide ceramics (~75 wt.% ζ-Ta4C3-x) were 710 ± 36.5 MPa and 10.2 ± 0.4 MPa· m1/2 at room temperature and decreased to 180 ± 19.7 MPa and 4.7 ± 0.1 MPa· m1/2 at 1600°C. The high aspect ratio grains (along the long axis) appeared to be the critical flaw. A brittle to ductile transition was observed between 1400°C and 1600°C. The ductility was attributed to deformation via kinking and delamination observed in the microstructure at room temperature. ζ-Ta4C3-x was observed to be machinable with traditional tools such as a hacksaw, drill bit, and end mill. The machinability is attributed to cleaving of grains along weakly bonded planes and prevention of crack propagation into the bulk ceramic\"--Abstract, p. iv
"]},{"key":"dc:title","label":"Title","values":["THERMAL AND MECHANICAL PROPERTIES OF NOVEL CARBIDE MATERIALS"]}]}],"canonical_facts":{"dc:creator":["Schwind, Evan Charles"],"dc:description.abstract":["\"This research focuses on studying the thermal and mechanical properties of novel carbide materials at room and elevated temperatures. The novel carbide materials investigated include zeta phase tantalum carbide (ζ-Ta4C3-x) and a high entropy (Ta,Hf,Nb,Zr)C carbide. The electrical resistivity and thermal conductivity of zeta phase tantalum carbide (~96 wt.%) were measured as 160 ± 4.2 μΩ-cm and 9.6 W/m•K. These are higher and lower (respectively) than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta4C3-x crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any of its carbide constituents with values ranging from 10.7 W/m•K at room temperature to 39.9 W/m•K at 2000°C. The electrical resistivity was higher than any of the carbide constituents ranging from 80.9 μΩ•cm at room temperature to 114.1 μΩ•cm at 800 °C. The electron contribution to thermal conductivity increased with temperature, and the phonon contribution was unaffected by temperature. The strength and fracture toughness of tantalum carbide ceramics (~75 wt.% ζ-Ta4C3-x) were 710 ± 36.5 MPa and 10.2 ± 0.4 MPa· m1/2 at room temperature and decreased to 180 ± 19.7 MPa and 4.7 ± 0.1 MPa· m1/2 at 1600°C. The high aspect ratio grains (along the long axis) appeared to be the critical flaw. A brittle to ductile transition was observed between 1400°C and 1600°C. The ductility was attributed to deformation via kinking and delamination observed in the microstructure at room temperature. ζ-Ta4C3-x was observed to be machinable with traditional tools such as a hacksaw, drill bit, and end mill. The machinability is attributed to cleaving of grains along weakly bonded planes and prevention of crack propagation into the bulk ceramic\"--Abstract, p. iv
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/3185"],"dc:subject":["High Entropy Carbide","Mechanical Properties","Tantalum Carbide","Thermal Properties","Ultra-High Temperature Ceramics","Zeta Phase","Ceramic Materials","Engineering"],"dc:title":["THERMAL AND MECHANICAL PROPERTIES OF NOVEL CARBIDE MATERIALS"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Ceramic Engineering"],"thesis:institution_name":["Missouri University of Science and Technology"]},"updated_at":"2026-07-24T03:18:18Z"}