Powders and Particles

Abstract

Nearly all practical ceramics and some metal products are fabricated from powders. Typically, these powders are mixed with a few percent of various organic and inorganic additives, compacted to form a porous “green” body¹, and heated (or “fired”) to a high temperature. During the heating the porosity in the sample is reduced or eliminated. This phenomenon is called sintering. Care must be taken to distinguish this sintering phenomenon from the sintering process described in Chapter 1. The properties of the sintered ceramic body depend to a large extent on the chemical and microstructural imperfections that were not eliminated or that were produced as a result of the sintering. Many imperfections can be traced back to the structure of the green compact or to the nature of the starting powder; therefore, in this chapter we examine powders. Powders can have a complex structure. Sometimes in describing powders confusion may arise through the inconsistent use of terminology. The terminology proposed by Onoda and Hench (1978) has been adopted here.