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Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures./
Author:	Grohsmeyer, Ryan Joseph.
Description:	1 online resource (281 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 78-12(E), Section: B.
Subject:	Materials science. -
Online resource:	click for full text (PQDT)
ISBN:	9780355089837

Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures.
Grohsmeyer, Ryan Joseph.

Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures. - 1 online resource (281 pages)

Source: Dissertation Abstracts International, Volume: 78-12(E), Section: B.

Thesis (Ph.D.)--Missouri University of Science and Technology, 2017.

Includes bibliographical references

This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500°C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500°C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500°C 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•m ½) did not trend with MoSi2 content. At 1500°C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500°C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355089837Subjects--Topical Terms:

557839
Materials science.
Index Terms--Genre/Form:

554714
Electronic books.

Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures.
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245 1 0 $a Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Molybdenum Disilicide Ceramics and Dual Composite Architectures.
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500 $a Source: Dissertation Abstracts International, Volume: 78-12(E), Section: B.
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502 $a Thesis (Ph.D.)--Missouri University of Science and Technology, 2017.
504 $a Includes bibliographical references
520 $a This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500°C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500°C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500°C 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•m ½) did not trend with MoSi2 content. At 1500°C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500°C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa.
520 $a Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500°C 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 1500°C. The granule-matrix interface did not deflect cracks, and the toughness at 1500°C was 6.1--6.9 MPa•m½, similar to that of conventional ZrB 2-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.
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