Traditional Versus Advanced Ceramics

Most people associate the word ceramics with pottery, sculpture, sanitary ware, tiles, etc. And whereas this view is not incorrect, it is incomplete because it considers only the traditional, or silicate-based, ceramics. Today the field of ceramic science or engineering encompasses much more than silicates and can be divided into traditional and modern ceramics. Before the distinction is made, however, it is worthwhile to trace the history of ceramics and people s association with them. 

It has long been appreciated by our ancestors that some muds, when wet, were easily moldable into shapes that upon heating became rigid. The formation of useful articles from fired mud must constitute one of the oldest and more fascinating of human endeavors. Fired-clay articles have been traced to the dawn of civilization. The usefulness of these new materials, however, was limited by the fact that when fired, they were porous and thus could not be used to carry liquids. Later the serendipitous discovery was made that when heated and slowly cooled, some sands tended to form a transparent, water-impervious solid, known today as glass. From that point on, it was simply a matter of time before glazes were developed that rendered clay objects not only watertight, but also quite beautiful. 

With the advent of the industrial revolution, structural clay products, such as bricks and heat-resistant refractory materials for the large-scale smelting of metals were developed. And with the discovery of electricity and the need to distribute it, a market was developed for electrically insulating silicate-based ceramics. 

Traditional ceramics are characterized by mostly silicate-based porous microstructures that are quite coarse, nonuniform, and multiphase. They are typically formed by mixing clays and feldspars, followed by forming either by slip casting or on a potter s wheel, firing in a flame kiln to sinter them, and finally glazing. 

In a much later stage of development, other ceramics that were not clay-or silicate-based depended on much more sophisticated raw materials, such as binary oxides, carbides, perovskites, and even completely synthetic materials for which there are no natural equivalents. The microstructures of these modern ceramics were at least an order of magnitude finer and more homogeneous and much less porous than those of their traditional counterparts. It is the latter — the modern or technical ceramics — with which this book is mainly concerned. 

---