of indium are placed within a close distance of each other. Within the electric field, at
the surface of the carbon nanotube, indium is transported by electro-migration from
one droplet to the next; hence, one droplet shrinks and the other grows, until the
moment when the two droplets touch each other and coagulate. During the
coagulation process, the material of both drops is concentrated into the larger
drop, which increases its size again. After coagulation, continuing material transport leads to reformation of the smaller second droplet, which is nucleated at a
discontinuity at the surface of the nanotube. Provided that the system is free of
Figure 3.19 Two sintering grains. The diagram indicates ranges with positive and negative
curvature, and material transport associated with the curvature-dependent vapor pressure.
Figure 3.20 Two sintering alumina particles.
The curvature-dependent vapor pressure causes
material to evaporate at the positively curved
surfaces of the particles, and to condense in the
wedge (or neck) between the two particles,
where the curvature is negative [16].
(Reproduced with permission by Springer.)
3.3 Some Technical Consequences of Surface Energy j39