technology are in continuous development. This leads to ever
more demanding and intelligent technology.
The demands made on modern materials are increasing with
the same dynamism. The features that are demanded include
greater strengths for material-saving constructions, lighter
components for energy saving, higher quality for more security
and longer service life. After all, cost-effectiveness plays
a crucial role.
Ceramic materials have in the past made an important contribution
to this process of innovation.
Requirements for the successful application of ceramics include
constructions that are appropriate to the materials and the
manufacturing processes, as well as appropriate applications.
The point is not that common materials can be displaced, but
rather that customised products allow completely new solutions.
The road to the ceramic component
In order to make intelligent and effective use of the properties
of ceramics, it is not sufficient simply to take an existing
structural component and to replace it in every detail with
a ceramic part. A drawing of the component used so far, however,
together with a great deal of supplementary information, can
show the way to the mass-produced ceramic component.
Thermal, electrical, mechanical loading and the chemical
environment must all be taken into account in this process.
Appropriate criteria relevant to each particular case mean
that one or more suitable materials out of the wide range
of available ceramics can be identified. The materials tables
and associated descriptions in the following chapters will
be helpful in this process.
The ceramic material for the new application must satisfy
the technical analysis of the particular problem, must also
offer an appropriate price/performance ratio throughout its
service life, and may have to offer additional benefits.
The drawing is then checked for feasibility of implementation,
and optimised for manufacture.
The tolerances required are often typical of those for metals,
i.e. relatively close for all surfaces. In order to optimise
costs it is necessary to distinguish between the general tolerances
typical for ceramics, and special tolerances that may be needed
for functional surfaces.
In a few cases it may also be necessary to consider the functional
principles, and therefore perhaps a new design for the assembly.
The user will be steered through the process described above
by the ceramics manufacturer.
After clarifying the technical details, the ceramics manufacturer
can choose the optimum production procedure, bearing in mind
the length of the production run, and can make a quotation.
Ceramics have already proven themselves in a wide variety
of applications, and are being considered for others where
high hardness, wear resistance, corrosion resistance and high
temperature stability, combined with low specific weight,
are necessary. The new high-tech materials achieve high levels
of strength. Their figures are comparable with those for metals,
and generally exceed those of any polymer.
The properties of the ceramic material are heavily influenced
by those of the particular microstructure. The mechanical
and physical properties can be influenced in different ways
through the deliberate creation of particular microstructures,
a process referred to as "microstructure design".
An important point always to bear in mind when applying ceramics
is this - ceramics are brittle! The ductility of metal construction
materials make them "good-tempered and well-behaved".
They are able to forgive small errors of construction (incorrect
tolerance), because they are able to disperse local stress
peaks through elastic and plastic deformation.
Other features typical of metals include good electrical
and thermal conductivity, and characteristics that are independent
Ceramic materials, on the other hand, are usually electrically
and thermally insulating, have high hardness figures, and
may have very low thermal expansion. Their shape is, furthermore,
extremely stable due to the absence of a capacity for plastic
deformation. Compression strengths ten times greater than
the bending or tensile strengths can be achieved. In comparison
with metals, ceramics are particularly suitable for application
at high temperatures, since the characteristics of ceramic
materials are altogether less strongly influenced by temperature
than metals and even then only at particularly high temperatures.
Ceramics offer equally high benefits in terms of corrosion
and abrasion resistance.
Because of these advantages, we find technical ceramics wherever
we go. Without ceramic insulators, many household devices
would not function. Likewise, without insulators and safety
devices made of technical ceramics, a reliable electricity
supply would be unthinkable. Ceramic substrates and parts
are the basis for components and modules in all areas of electronics,
while in machine and plant construction sliding and bearing
elements provide low wear, corrosion-free function. Ceramic
construction and insulation materials are indispensable to
the industrial furnaces used in high-temperature technology.
Even these few examples make clear that technical ceramics
have an important role to play in today's world.
Ceramic components are often, however, not visible at the
first glance. Nevertheless they play a crucial role, both
in conventional applications and in innovative products.
The potential of technical ceramics has not yet been exhausted.