Brevier Technical Ceramics






The use of ceramics can be traced back to the early history of mankind. Reliable archaeological research has shown that the first ceramic figures were formed from malleable ceramic material and hardened by fire more than 24,000 years ago. Almost 10,000 years later, as our ancestors developed settled communities, tiles were first manufactured in Mesopotamia and India. The first useful vessels were then produced in Central Europe between 7,000 and 8,000 years ago.

Until the end of the Middle Ages, the smelting and process furnaces of the early metal industry were constructed using natural sandstone bonded with kaolinite or siliceous material. The development of synthetic refractory materials (Agricola, Freiberg around 1550) was one of the foundation stones of the industrial revolution, and created the necessary conditions for melting metals and glass on an industrial scale, and for the manufacture of coke, cement and ceramics.

The ceramics industry was an important partner to the chemical industry. Acid-resistant stoneware and porcelain were for a long time the most important materials available for corrosion protection. Nowadays they have largely been replaced by acid-resistant steels and enamels, but also by ceramics based on oxides, nitrides and carbides.

Beginning in the second half of the 19th century, electro-ceramics provided the momentum for industrial development. During this time, basic solutions for electrical insulation based on porcelain were developed.

It is difficult to determine the precise beginning of modern, high-performance ceramic materials. Until the turn of the 20th century, the development of ceramic materials had a primarily empirical character. Scientific methods were first applied to ceramics in the course of the 20th century.

The development of manufacturing technologies using quartz-enriched porcelain achieved bending strengths of more than 100 MPa for the first time. It was only in the 1960s, with the systematic development of alumina porcelain, that marked increases in strength, especially in large insulators for voltages over 220 kV, resulted in considerable weight reductions.

Figure 1: Manufacture of insulators around 1920.

The growth of broadcast radio in the 1920s led to the need for special ceramic insulation materials that did not heat up under the influence of high-frequency electromagnetic fields. This led to the development of steatite and forsterite, both of which are still in use today. Research on oxide magnetic materials began in the 1940s (hard ferrites, soft ferrites). At this time, capacitor materials based on titanium oxide were also developed, and research began on the ferroelectric and piezoelectric properties of perovskite (BaTiO3). This made a wide palette of materials available – some even with semiconducting properties – for sensors, frequency selective components (filters) and capacitors with high storage capacity. Theoretical considerations are derived from basic research by Heisenberg, Dirac, Heitler, Londas, Hartre and Fock, among others.

A further important milestone was the introduction of sparkplugs made of sintered alumina (Siemens, 1929). The development of micro-electronics increased the demand for aluminium oxide materials, for example, as a material for substrates and housings. An important property of this material, in addition to high electrical resistance, low dielectric losses, high thermal conductivity, high mechanical strength and thermal shock resistance, is the vacuum tightness offered by these new types of material.

While the thermal properties were sufficiently well explained by the theories of Debye, it was necessary to develop a theory of fracture mechanics in order to explain mechanical properties. Whereas initially aluminium oxide and later zirconium oxide, were first used as ceramic construction materials, the outstanding properties of covalently bonded materials based on silicon (silicon carbide, silicon nitride, SIALONe etc.) were recognised and exploited at the end of the 1960s. Research into all these materials continues today. In addition to the approaches of fracture mechanics, new mathematical methods and computer simulations have been developed in order to understand the relationship between microstructure and properties through modelling. In parallel with the theoretical developments, process technologies have been optimised, extending as far as the introduction of completely new process sequences and sintering methods.

Known materials continue to be improved, new materials are being developed, and new applications are being found. The materials of today can no longer be compared with those that were on the market ten or twenty years ago. Scientific research is increasing our understanding of materials. New and improved manufacturing technologies have brought progress in the areas of quality, reproducibility and operating safety.


<< back   home   next >>