The application of clay minerals in ceramics

Abstract

Deriving in ancient Greece as keramikos, the term potters clay was only reconfirming the recognition of clay as man's earliest utilitarian raw material. Clay is no doubt man's first manufacturing and construction raw material and fortunately, through the miracle of fire, the first lasting chronicler of his own origin and early history. Oddly enough, millennia later, the material still occupies leading positions in the construction and manufacturing areas with each generic end-use accounting annually for about one billion dollars of salable product in the U.S. alone. Needless to say, clay ceramics are proven products. The longevity of clay in the ceramics industry stems in part from its variable and some times unique physical and chemical properties and in part to its ubiquitous occurrence and relatively inexpensive produced value. Clay properties of interest to the ceramics industry are plasticity and moldability, of course, but also chemistry, color, refractoriness, solubility and corrosion resistance, electrical properties and the many possible variations on these and other properties afforded by the essentially two-dimensional morphology of the individual clay platelets. In addition to construction (brick, tile, sewer pipe, cement, fiberglass, roof granules, paint, etc.) and manufacturing (refractories, kiln furniture, sanitary ware pottery and dinnerware) clays are used in the calcined form as fillers, carriers, extenders and grogs. Chemistry, because of its basic relationship to both the chemical and physical properties of clay, has been the subject of continuous studies over the past few decades and is responsible for most of advances in processing which have taken place. Color body removal and the elutriation of objectionable salts have led to more or less sophisticated slurrying and the beneficiation which this medium affords. In particular, the water washing, first initiated by the kaolin industry and now extended to ball clays, and high-energy magnetic filtration have noticeably improved the quality of clay and broadly expanded its market in the ceramics industry. At the present time, ceramics markets are under pressure in several areas. Refractories have followed the downturn in American steel production. Although stabilizing, this industry continues at reduced levels which threatens to become the new norm. Likewise, dinnerware and tile production in the U.S. have declined because of foreign competition.