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Surface and Environmental Effects on Ceramic Materials

P. GibbsG. S. BakerBertram Gale Dick (Jr.)E. K. BeauchampM. H. MilesW. G. Rogers

出版	Aeronautical Systems Division, Air Force Systems Command, United States Air Force, 1961
URL	http://books.google.com.hk/books?id=kD79uFpGHagC&hl=&source=gbs_api

註釋Polycrystalline sintered compacts of doped Alucer MC Al2O3 were deformed in 3 point beam loading from 1000 to 1350 C. The steady state creep rate of specimens doped wit MgO or Mn(CO3)2 from 50 to 5000 ppm by weight were fit to the expression A exp ( -E/kT). The activation energy E was 130 kcal/mol independent of added impurity. The constant A was independent of Mn(CO3)2, but decreased by a factor of 3-5 on the addition of MgO. Polycrystalline creep apparently is controlled by diffusion of vacancies in the steady state. Creep behavior of Linde corundum 0.1-in.-diam rods (1000-1250 C) is described. At the lowest temperatures and stresses studied, measureable creep (.1 micron/hr beam deflection) began after about an hour's time delay, and increased at an accelerating rate. One run was successfully continued to reach a steady state (7500 micron deflection). Activation energies increased as creep proceeded (71-135 kcal/mol).