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Elastic Properties of Mullite Single Crystals up to 1400°C

Schreuer, Jürgen and Hildmann, Bernd and Schneider, Hartmut (2006) Elastic Properties of Mullite Single Crystals up to 1400°C. Journal of the American Ceramic Society, 89 (5), pp. 1624-1631. doi: 10.1111/j.1551-2916.2006.00921.x. ISSN 0002-7820.

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Elastic constants and their temperature derivatives of orthorhombic 2/1-mullite single crystals were determined using resonant ultrasound spectroscopy between ambient temperature and 14001C in air. The values at room temperature given in GPa were c11 = 279.5(4), c22 = 234.9(2), c33 = 360.6(3), c44 = 109.49(7), c55 = 74.94(4), c66 = 79.89(4), c12 = 103.1(2), c13 = 96.1(3), and c23 = 135.6(1). The high temperature ultrasound data sets were corrected for thermal expansion effects using the coefficients, which were measured in the range -170 to 1400°C by means of dilatometry. Up to about 1000°C, the temperature evolution of the elastic stiffnesses was linear and the corresponding thermoelastic constants Tij=d log cij/dT given in 10 exp-6 °C exp-1 were T11=-100(2), T22=-126(2), T33=-78.2(6), T44=-75.3(7), T55=-81.3(9), T66=-113(1), T12=-153(3), T13=-94(4), and T23=-47(2). While the temperature derivatives of the longitudinal stiffnesses and the transverse interaction coefficients remained linear, the shear resistances c44, c55, and c66 displayed an increased softening above about 1000°C, which was accompanied by a rapidly increasing ultrasound dissipation. In the same temperature region, small, but clearly recognizable discontinuities in the longitudinal and in the volume thermal expansion coefficients occurred. Taking into account the behavior of the heat capacity, the observed anomalies may indicate a glass-like transition of mullite above about 1000°C. An unexpected peak in the ultrasound dissipation at about 70°C was most likely caused by anelastic point defect relaxations.

Item URL in elib:https://elib.dlr.de/49958/
Document Type:Article
Title:Elastic Properties of Mullite Single Crystals up to 1400°C
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Schreuer, JürgenUniversität Frankfurt, Institut für Mineralogie/KristallographieUNSPECIFIEDUNSPECIFIED
Journal or Publication Title:Journal of the American Ceramic Society
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1624-1631
Keywords:elastic constants, mullite, single crystals
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Combustion Chamber Technologies (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Structural and Functional Ceramics
Deposited By: Mechnich, Dr.rer.nat. Peter
Deposited On:18 Jul 2007
Last Modified:27 Apr 2009 14:05

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