Biomedical Engineering Reference
In-Depth Information
13.2 Illustration of the discrepancy between the measured differential
heat of adsorption of Pb onto MgO(100) and the prediction based on
constant
model. Surface energy increases substantially as the radius
decrease below
γ
3 nm.
~
From another aspect, the surface energy is also a function of the crystal
orientations, which could affect the driving force of sintering of nano
particles. Groza
2
pointed out that because nanocrystals have significant
surface area, the problem of anisotropy becomes even more critical.
Although there are numerous studies reporting that nano particles have
anisotropic faceted morphology, direct correlation of their effect on surface
energy and sintering is not available in the literature and, understandably, is
very difficult to perform. One phenomenon that has been reported regarding
nanocrystals with faceted morphology is that they form an oriented-
attached assembly as shown in Fig. 13.3.
11
The oriented attachment of nano
