\"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB2-MoSi2 ceramics hot pressed using fine, medium, or coarse ZrB2 starting powder with 5-70 vol.% MoSi2, referred to as FX, MX, and CX respectively where X is the nominal MoSi2 content. MoSi2 decomposed during sintering, resulting in microstructures with ZrB2 cores and (Zr1-xMox)B2 shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB2 grain size, and toughness (2.7-3.9 MPa·m1/2) did not trend with MoSi2 content. At 1500⁰C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500⁰C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.
Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500⁰C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500⁰C. The granule-matrix interface did not deflect cracks, and the toughness at 1500⁰C was 6.1-6.9 MPa·m1/2, similar to that of conventional ZrB2-MoSi2 ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs\"--Abstract, page iv.
","abstract_html":"<p>"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB<sub>2</sub>-MoSi<sub>2</sub> ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB<sub>2</sub>-MoSi<sub>2</sub> dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB<sub>2</sub>-MoSi<sub>2</sub> ceramics hot pressed using fine, medium, or coarse ZrB<sub>2</sub> starting powder with 5-70 vol.% MoSi<sub>2</sub>, referred to as FX, MX, and CX respectively where X is the nominal MoSi<sub>2</sub> content. MoSi<sub>2</sub> decomposed during sintering, resulting in microstructures with ZrB<sub>2</sub> cores and (Zr<sub>1-x</sub>Mo<sub>x</sub>)B<sub>2</sub> shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB<sub>2</sub> grain size, and toughness (2.7-3.9 MPa·m<sup>1/2</sup>) did not trend with MoSi<sub>2</sub> content. At 1500⁰C toughness increased with MoSi<sub>2</sub> content and ZrB<sub>2</sub> grain size, and strength of FX and MX was controlled by oxidation damage at 1500⁰C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.</p><p>Four ZrB<sub>2</sub>-MoSi<sub>2</sub> DCAs were fabricated by dispersing granules of selected ZrB<sub>2</sub>-MoSi<sub>2</sub> compositions in matrices of different ZrB<sub>2</sub>-MoSi<sub>2</sub> compositions. Strength limitation at 1500⁰C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500⁰C. The granule-matrix interface did not deflect cracks, and the toughness at 1500⁰C was 6.1-6.9 MPa·m<sup>1/2</sup>, similar to that of conventional ZrB<sub>2</sub>-MoSi<sub>2</sub> ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs"--Abstract, page iv.</p>","abstract_has_math":false,"creators":["Grohsmeyer, Ryan Joseph"],"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":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T03:18:26Z","subjects":["High-Temperature Ceramics","Mechanical Properties","Microstructure","Molybdenum Disilicide","Processing","Zirconium Diboride","Energy Systems","Materials Science and Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/2561","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Grohsmeyer, Ryan Joseph"]}]},{"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 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":["High-Temperature Ceramics","Mechanical Properties","Microstructure","Molybdenum Disilicide","Processing","Zirconium Diboride","Energy Systems","Materials Science and Engineering"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/2561"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB2-MoSi2 ceramics hot pressed using fine, medium, or coarse ZrB2 starting powder with 5-70 vol.% MoSi2, referred to as FX, MX, and CX respectively where X is the nominal MoSi2 content. MoSi2 decomposed during sintering, resulting in microstructures with ZrB2 cores and (Zr1-xMox)B2 shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB2 grain size, and toughness (2.7-3.9 MPa·m1/2) did not trend with MoSi2 content. At 1500⁰C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500⁰C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.
Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500⁰C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500⁰C. The granule-matrix interface did not deflect cracks, and the toughness at 1500⁰C was 6.1-6.9 MPa·m1/2, similar to that of conventional ZrB2-MoSi2 ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs\"--Abstract, page iv.
"]},{"key":"dc:title","label":"Title","values":["Processing, microstructure, and mechanical properties of zirconium diboride-molybdenum disilicide ceramics and dual composite architectures"]}]}],"canonical_facts":{"dc:creator":["Grohsmeyer, Ryan Joseph"],"dc:description.abstract":["\"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB2-MoSi2 ceramics hot pressed using fine, medium, or coarse ZrB2 starting powder with 5-70 vol.% MoSi2, referred to as FX, MX, and CX respectively where X is the nominal MoSi2 content. MoSi2 decomposed during sintering, resulting in microstructures with ZrB2 cores and (Zr1-xMox)B2 shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB2 grain size, and toughness (2.7-3.9 MPa·m1/2) did not trend with MoSi2 content. At 1500⁰C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500⁰C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.
Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500⁰C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500⁰C. The granule-matrix interface did not deflect cracks, and the toughness at 1500⁰C was 6.1-6.9 MPa·m1/2, similar to that of conventional ZrB2-MoSi2 ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs\"--Abstract, page iv.
"],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/2561"],"dc:subject":["High-Temperature Ceramics","Mechanical Properties","Microstructure","Molybdenum Disilicide","Processing","Zirconium Diboride","Energy Systems","Materials Science and Engineering"],"dc:title":["Processing, microstructure, and mechanical properties of zirconium diboride-molybdenum disilicide ceramics and dual composite architectures"],"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":"2026-07-24T03:18:26Z"}