Properties of casting slips

Rheological properties of casting slips are controlled by small additions of suitable electrolytes which promote deflocculation of aggregates and thus cause a decrease in yield point and increase in fluidity, which is desirable with respect to reduction of the required water content (refer to the section on slip casting). The stability of the suspension is also improved, i.e. the sedimentation of the solids is suppressed. 

Elementary Ideas of Flow Properties Flow Properties of Casting-slips Measurement of Flow Properties Dilatancy Rheopexy... 

Table 5. Adjustment of Flow Properties of Casting-slips...

Aqueous casting slips of satisfactory properties can be prepared from non-plas1 substances (e.g. oxides, nitrides) by controlling their pH Fig. 160 shows the effe of pH on viscosity of a—AI2O3 suspension of 5 pm particle size. In this case, a suitab fluidity is achieved in an acid or strongly alkaline medium. Substances that a hydrolyzed by water (e.g. MgO) can be shaped by casting a suspension in alcohol... 

To alter any one flow property alone, leaving the others constant, it is clearly necessary to combine two of the three additions suggested in Table 5. For example, to increase the thixotropy of a casting-slip without altering the fluidity appreciably, it may be necessary to add untreated clay or body, and water. The addition of clay increases the thixotropy but at the expense of fluidity the addition of water restores the fluidity to its original value, without unduly affecting the thixotropy. The most suitable values of fluidity and thixotropy vary from one slip to another and can only be found by trial and error. 

Lehman L (1958) Plaster Molds and the Influence of their Properties on the Formation of a Slip Casting. Berichte der DKG 35 273-277... 

The idea of slip, and the even vaguer one of microscopic viscosity, are frequently invoked when deviations from Stokes law occur. Before concepts of this kind can become useful they must be cast into a more quantitative mould and related to measurable properties of solute and... 

Carter CB, Norton MG (2007) Ceramics materials science and engineering. Springer, Berlin Tsetsekou A, Agrafiotis C, Milias A (2001) Optimization of the rheological properties of alumina slurries for ceramic processing appUcations—Part I slip casting. J Eur Ceram Soc 21 363-373... 

Sommer F, Kern F, El-Maghraby HF, Abou El-Ezz M, Awaad M, Gadow R et al (2012) Effect of preparation route on the properties of slip-casted AI2O3/YAG composites. Ceram... 

Ramavath P, Biswas P, Rajeswari K, Suresh MB, Johnson R, Padmanabham G et al (2014) Optical and mechanical properties of compaction and slip cast processed transparent polycrystalline spinel ceramics. Ceram Int 40 5575-5581... 

The mechanical as well as the high temperature properties of this material, have been studied in some detail. Bars fabricated using the slip-casting technique have shown good density. Young s modulus values and flexural strength, which corroborate the values reported in literature. Cyclic thermal shock quench tests have been performed on the bars, to study the effect on mechanical properties. These observations have been supported by microstructural analysis. 

TOO Richter, H., Kleer, G., Heider, W, and Rottenbacher, R. (1985) Comparative study of the strength properties of slip-cast and of extruded silicon-infiltrated SiC. Mater Sci. Eng., 71, 203-208. 

Another rheological property often displayed by tape casting slips is thixotropy. Thixotropy describes the tendency of a slip to increase in viscosity over time under no shear. With no shear applied to a tape... 

PFW. Lead iron tungstate (from the chemical symbols Pb, Fe, W). pH. Symbol for the acidity or alkalinity of a solution it is a number equivalent to the logarithm, to the base 10, of the reciprocal of the concentration of hydrogen ions in an aqueous solution. The point of neutrality is pH7 a solution with a pH below 7 is acid, above 7 is alkaline. The pH of a casting slip is of practical importance in determining its rheological properties. 

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