Silicon, carbon, and nitrogen were introduced into alumina polycrystals by in situ pyrolysis of a polysilazane precursor. These specimens were tested in compression creep from 1300° to 1400°C at stresses ranging from 60 to 120 MPa. The creep rates were comparable with those obtained by Thompson and colleagues. in nanocomposites, which had been fabricated by the powder route from alumina and silicon carbide. The convergence of these two data sets suggests that the retardation of creep rate in these composites is likely due to a chemical alteration of the grain boundaries in alumina, which either retards interfacial diffusion or creates an interface reaction barrier to diffusional creep, or both. A threshold stress and the absence of primary creep are unusual manifestations of the present experiments.
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Document Type: Research Article
Department of Engineering Mechanics, Center for Aircraft Structural Life Extension (CAStLE), United States Air Force Academy, USAF Academy, Colorado 80840
Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309 0427
Publication date: 2010-04-01