Additives and Ceramic Forming

Various additives, generally with very low concentrations, have been used to control the characteristics of the feed materials, in order to achieve desired shapes and control the packing uniformity of the green body of ceramics. For some methods, such as tape casting and injection molding, the use of suitable additives is especially important. The additives can be either organic or inorganic materials. 

Organic additives are more widely used for such applications, because they can be removed more easily than inorganic ones. 

According to their functions, the additives in ceramic process can be classified into four main groups (i) solvents, (ii) dispersants, also known as deflocculants, (iii) binders, and (iv) plasticizers. Additives with other functions, such as lubricants and wetting agents, are also used in some occasions. Successful additives have often been found by trial-and-error approaches, although information is available on chemical principles and applications of additives [71, 72]. 

Liquids are used in ceramic processing have two major functions (i) providing fluidity for the powder to be processed during the forming and (ii) dissolving the additives to be introduced into the powder as solvents, so as to disperse the additives throughout the powder uniformly. 

The capability of a liquid to wet a solid by is defined in tenns of the contact angle, which is given by  

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