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The creep behaviour and microstructure of two silicon nitride ceramics have been investigated. Compressive creep tests were performed at temperatures between 1450 and 1700°C at stresses between 6 and 90?MPa in an Ar atmosphere. The creep behaviour was characterized by a stress exponent lower than one for both materials, with an average value n?≈?0.6 over the whole range of stresses and temperatures, and with apparent activation energies between 470 and 530?kJ?mol?1. The study of the microstructural evolution revealed the absence of dynamic grain growth and, in some cases, evidence of grain rearrangement. Partial coalescence of cavities was observed only at the highest stress, but this did not result in accelerated creep. 相似文献
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M. Jim nez-Melendo A. Domí nguez-Rodrí guez J. L. Routbort 《Physica C: Superconductivity and its Applications》1999,320(3-4):189-196
Rapid changes of oxygen partial pressure (PO2) between 103 and 2.1×104 Pa have been carried out during steady-state plastic deformation of polycrystalline YBa2Cu3O7−x (YBCO) at temperatures between 825 and 900°C. Transient creep was observed after such PO2 changes. The analysis of these creep transients allowed the determination of the chemical diffusion coefficient for reequilibration, which is identical to that found from thermogravimetry and electrical conductivity experiments for oxygen vacancies. 相似文献
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