Almost all engineering applications of metals involve their use
in polycrystalline form. Recently the emphasis in the study of mechanical properties
has moved away from the processes which occur inside the individual grains to those
which are governed by the boundaries between the grains. Diverse phenomena such as
high temperature creep, superplasticity, recrystallization, yielding and embrittlement
all depend strongly on effects at grain boundaries. Grain boundaries are also important
for diffusion phenomena as they provide pathways for diffusions into or within a material
that are orders of magnitude faster than through crystalline regions. Interactions of
grain boundaries and defects are also a topic of current research. Recent studies
emphasize the role of grain boundaries for premelting of a crystal. Despite the important
role of grain boundaries in material properties our knowledge at the microscopic level is
limited. The direct observation of grain boundary structure is limited by the lack of
resolution of experimental techniques such as high resolution transmission electron microscopy.
Thus colloidal crystals can serve as a model system to study grain boundary characteristics
as they are much larger and show a much slower dynamics which makes them accesible to
experimental techniques like confocal microscopy.
Investigated System
In our experiments we grow colloidal crystals on a template that contains the particular grain
boundary of interest. A crystal of Silica
particles with radius of 1.5 µm is grown on this template The structure and the general
properties of these grain boundary can be studied by confocal based video microscopy.So far we have investigated three different types of grain boundaries:
a &Sigma 5 grain boundary, a &Sigma 17 grain boundary and a &Sigma 3 grain boundary which differ in orientation and excess volume.
Figure 1 shows the templates for the three grain boundaries.
Figure 1: Templates for the different types of grain boundaries.
