1.5.4 Competition between Densification and Coarsening
The various sintering mechanisms do not operate independently. Vapor transport and surface diffusion compete with the densifying mechanism. They lead to coarsening of the microstructure and a reduction of the driving force for sintering, so that a significant reduction in the densification rate can result.
1.5.5 Effects of Grain Boundaries
In the sintering of polycrystalline materials, part of the energy decrease due to elimination of internal surface area associated with the pores goes into creating new grain boundary area. The grains also have a tendency to grow, by migration of the boundaries, to reduce the energy associated with the grain boundaries, there by leading to an increase in the diffusion distance.
The presence of the grain boundaries also dictates the equilibrium shape of the pores at the intersection with the boundaries. At equilibrium, the chemical potential of the atoms in the pore surface must be the same everywhere, which is equivalent to saying that the curvature of the pore surface is the same everywhere.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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