Creep alumina-based ceramics

Pysher, D.J., and R.E. Tressler. 1992a. Creep rupture studies of two alumina-based ceramic fibers. Journal of Materials Science 27 423—428. ... 

Pysher, D. J., and Tressler, R. E., "Creep rupture studies of two alumina-based ceramic fibres." Journal of materials science 27.2 (1992) 423-428. 

Pysher, D.J., and R. E. Tressler. 1992b. Tensile creep rupture behavior of alumina-based polycrystalline oxide fibers. Ceramic Engineering and Science Proceedings 13(7-8) 218-226... 

The asymmetry between tensile and compressive creep is a typical feature of other systems, such as SiC-based and Al203-based ceramics. In fact, this is common in ceramic systems in which an easily deformable glassy phase located at the grain boundaries is present. In contrast, single-phase ceramics such as pure alumina polycrystals and YTZP are reported to be symmetric under both tension and compression. 

Alumina based fibers are subject to creep, even at low temperatures, This phenomenon is exacerbated by the fine grain size of the fibers [20] [54] [67] [70] [73] [79-80]. At 1200°C and with an applied stress of 70 MPa, the strain rate for the fine-grained Nextel 610 a-alumina fiber is higher than that of Fiber FP with a coarser microstructure. Both strain rates are about one order of magnitude higher than that for a bulk alumina ceramic with a grain size of 1.2 jm. The aeep of Nextel 610 is already measurable at a temperature as low as 900 C under an applied stress of 200-500 MPa [70]. 

Remarkable characteristics of nanocomposites observed by many researchers are summarized " Drastic change of fracture mode is observed from intergranular fracture of monolithic ceramics to transgranular fracture of nanocomposites, especially in alumina-based nanocomposites. Several mechanical properties were also improved, such as fracture strength, " " fracture toughness, " thermal shock resistance, creep resistance, " hardness, " and wear resistance." ... 

Hackemann, S., Flucht, F., and Braue, W., "Creep investigations of alumina-based all-oxide ceramic matrix composites." Composites Part A Appiied Science and Manufacturing41.12 (2010) 1768-1776. 

Many layered oxide coatings show promise as crack deflecting interfaces for oxide-oxide composites. Although the jl-aluminas have been shown to be unstable with Nextel 720 fibers, they are still candidate fiber coatings (especially the less volatile RbAlnOiy) for ceramic composites if other creep-resistant oxide fibers become available. Research into an improved creep-resistant Nextel 610 fiber that incorporates additions of rare-earth oxides or garnet-based fibers, may make the (5-... 

All-oxide CMCs based on alumina fibers and matrices are favorable materials for use at high temperature in oxidizing atmospheres. One possibility for CMCs is the application as combustion liner. As a major drawback oxide fibers show the lowest creep resistance of all ceramic fibers due to their predominant ionic bonds. Therefore, the knowledge of the creep behavior becomes important for construction and dimensioning of components undergoing creep deformation over the life time. 

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