TABLE OF CONTENTS Suspensions or "dispersions" of particles in a liquid medium are ubiquitous. Blood, paint, ink, and cement are examples that hint at the diversity and technological importance of suspensions. Suspensions include drilling muds, foodstuffs, pharmaceuticals, ointments and cremes, and abrasive cleansers and are precursors of many manufactured goods, such as composites and ceramics. Control of the structure and flow properties of such suspensions is often vital to the commercial success of the product or of its manufacture. For example, in consumer products, such as toothpaste, the rheology of the suspension can often determine consumer satisfaction. In ceramic processing, dense suspensions are sometimes molded (Lange 1989) and then dried and sintered or fired into optical components, porcelin insulators, turbine blades, fuel cells, and bricks (Rice 1990; Simon 1993). Crucial to the success of the processing is the ability to transform a liquid, moldable suspension into a solid-like one that retains its shape when removed from the mold. These examples could be multiplied many times over.
Suspensions of small particles are often called "colloids," a term derived from the Greek word ?o ? ? ? for "glue." This name was coined by Thomas Graham (1805-1869), who defined colloids as substances that could not diffuse through a membrane. Already in the seventeenth century, however, alchemists had produced stable suspensions, or sols, of inorganic particles, such as gold.
