Slip casting, ceramics

A common method to slip-cast ceramic membranes is to start with a colloidal suspension or polymeric solution as described in the previous section. This is called a slip . The porous support system is dipped in the slip and the dispersion medium (in most cases water or alcohol-water mixtures) is forced into the pores of the support by a pressure drop (APJ created by capillary action of the microporous support. At the interface the solid particles are retained and concentrated at the entrance of pores to form a gel layer as in the case of sol-gel processes. It is important that formation of the gel layer starts... 

Kovac M, Havrda J, Oujiri F (1993) A model of slip casting. Ceram-Silik 37 67-72... 

Slip casting of metal powders closely follows ceramic slip casting techniques (see Ceramics). SHp, which is a viscous Hquid containing finely divided metal particles in a stable suspension, is poured into a plaster-of-Paris mold of the shape desired. As the Hquid is absorbed by the mold, the metal particles are carried to the wall and deposited there. This occurs equally in all directions and equally for metal particles of all sizes which gives a uniformly thick layer of powder deposited at the mold wall. 

Slip Casting. SHp casting (38,40—42,45,59—62), the process in which a cast is formed from a slurry using a porous mold, is used to form sinks and other sanitary ware, figurines, refractory cmcibles, porous thermal insulation, fine china, and complex shape stmctural ceramics such as multivane rotors. 

Slip casting is common in the ceramics industry. The material to be cast is milled to a mean particle size of a few microns. A slip is made by mixing the finely divided material with a liquid suspending medium. The slip is then poured into a suitable mold (e.g., of plaster of pans). The liquid in the slip is drawn into the mold by capillary forces and the solids are deposited in a coherent form. For TiBj, ZrBj and CrBj a suspending medium of 5-7 wt% cyclopentadiene in xylene is recommended. A 3 wt% aqueous solution of carboxymethylcellulose is the best dispersing medium... 

Conventional ceramics initially take shape on a potter s wheel or by slip casting and are fired (sintered) in kilns advanced ceramics are formed and sintered in more complex processes such as hot isostatic pressing. 

A process for making hollow articles from latex. A heat-sensitised compounded latex is poured into a hollow non-porous mould which is then rotated about several axes until the latex has gelled on the surface of the mould. See Rotational Moulding. Similar to slip casting of ceramics. Ketones... 

Tiller, F. M. and Chum-Dar Tsai. 1986. Theory of filtration of ceramics I, Slip casting. J. Amer. Ceram. Soc. 69(12) 882-87. 

Figure 7.28 Schematic illustration of (a) drain and (b) solid types of slip-casting processes. Reprinted, by permission, from H. Yanagida, K. Koumoto, and M. Miyayama, The Chemistry of Ceramics, p. 160. Copyright 1996 by John Wiley Sons, Inc.

Figure 7.29 Schematic illustration of the formation of a slip-cast layer formed in the extraction of water by capillary action from a mold. From Introduction to Ceramics, by W. D. Kingery, H. K. Bowen and D. R. Uhlmann, Copyright 1976 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Functionally graded SiAION ceramics can be produced by lamination (powder and tape), powder bed, controlling the sintering conditions, infiltration, slip casting and so on. Some of these production techniques will be discussed in the following sections. 

A widely used technique for ceramic/ceramic gradient materials is sequential slip casting where slips of different compositions are cast one after and over another (Requenna et al., 1993). By using a premixing system, the casting composition can be tailored continuously (Chu et al., 1993). 

Requenna, J., Moya, J.S., Pena, P., (1993), Al2Ti03-Al203 functionally gradient materials obtained by sequential slip casting , in Holt, J.B., Koisumi, M., Hirai, T., Munir, Z.A., Functionally Gradient Materials, American Ceramic Society, Westerville, O.H., 203-210. 

Controlling the stability of suspended particles, and the filtration characteristics of cast suspensions, are very important in the ceramics industry. Here the casting suspensions may comprise clays, silica, oxides, carbides or nitrides [357,793], In slip casting, a suspension is pored into a porous mould and allowed to stand. Water dif-... 

In ceramics, a variation of slip-casting in which a stabilized colloidal dispersion of particles is poured into a mold for sintering. 

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