Biomedical Engineering Reference
In-Depth Information
rule. Cristobalite, an allotropic form of quartz (pure SiO
2
) is an example. They can,
however, be randomly stacked with some violation of the corner-to-corner rule by
smuggling small cations into the array. The crystalline structure vanishes in this
case and it becomes a
glass
endowed with very different properties. Outside its use
as base mineral in ceramics, kaolinite is used in pharmaceutical products as filler
and in the paper industry (glazed paper). Moreover, although unaware of the size of
the basic particles, ceramists were true nanotechnologists!
About oxidation/reduction.
Oxidation and reducing ...they did it without know-
ing that:
Fe
2
C
C 3
4
O
2
! 2
Fe
2
O
3
(9.1)
(reaction is not balanced and simplified by omission of anions and water) and
Fe
2
O
3
C
CO
! 2
FeO
C
CO
2
(9.2)
or
3
Fe
2
O
3
C
CO
! 2
Fe
3
O
4
C
CO
2
(9.3)
and then again oxidized to Fe
2
O
3
except for the glaze. Unless special effects are
pursued (the glaze), iron is in its highest oxidation states. Part of the glamor of
ceramics is their inertness, a consequence of the oxidation state of the elements
present.
Was this introductory circuitous way irrelevant for the subject of the topic? Pre-
sumably, the reader knows our answer: no. The ancient technological achievements
were considered a convenient heading to introduce a few fundamental concepts
helping to understand ceramics and...remaining is the fascinating high technical
proficiency and standardization by these ancient manufacturers. Be it clear that
ceramists or manufacturers of any other high quality product today need no less
than high technical proficiency profile.
Further reading: [
272
-
275
].
9.2
Ceramics, Impossible to Define?
The term
ceramics
is derived from the Greek word
,
keramos
or
kerameios
(of potter's earth or potter's clay) or
kerameıa
(potter's craft). There is
much uncertainty about its etymological root but a most attractive assumption is a
Germanic and Baltic etymon
qer-
meaning to burn, to heat [
276
]. Respecting the
etymological origin of the term an acceptable definition could be one according to
which
˛
(
)ø
&
ceramics are nonmetallic inorganic materials shaped and consolidated at high temperature.
As technology evolves as well with respect to compounds as to shaping technology
and modes of heat treatment, the term had to be accommodated to an increasingly
broader range of materials. We want, however, to keep consolidation by heat a basic
