Biomedical Engineering Reference
In-Depth Information
5
The Structure of Bioactive
Glasses and Their Surfaces
Alastair N. Cormack
Kazuo Inamori School of Engineering, New York State College
of Ceramics, Alfred University, Alfred, USA
5.1 STRUCTURE OF GLASSES
The atomic structure is everything to a glass, in that it affects all its
properties, especially its bioactivity and degradation rate.
Glasses, including bioactive glasses, are non-crystalline, which means
that their atomic scale structure is characterized by an absence of the
translational periodicity associated with crystalline structures. This lack
of long-range order means that traditional crystal structure concepts
such as unit cells and lattice vectors cannot be used to discuss the
structures of glasses. It also means that standard experimental probes
of structure, such as X-ray or neutron diffraction, cannot be used to
measure, or determine, the atomic arrangements in glasses. Fortunately,
the majority of bioactive glasses contain a lot of silica, and so their
structures can be described in the same way as other silicate glasses, for
which quite a lot is known by analogy to crystalline silicates, whose
structures have been well characterized in terms of the arrangement of
