It is difficult to imagine modem technology without small particles, 1-1000 nm in size, because virtually every industry depends in some way on the use of such materials. Catalysts, printing inks, paper, dyes and pigments, many medicinal products, adsorbents, thickening agents, some adhesives, clays, and hundreds of other diverse products are based on or involve small particles in a very fundamental way. In some cases finely divided materials occur naturally or are merely a convenient form for using a material. In most cases small particles play a special role in technology because in effect...