Introduction

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 today

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 of orientation.

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.