Slurry tape casting

Slurry Tape Casting In this method, a slurry or catalyst layer ink similar to that used in the spray deposition technique is spread onto the DM or directly onto the electrolyte via a doctor blade (Figure 6.4). This method produces high dimensional tolerance but is slower than physical spray deposition and less suitable for mass production. 

The thickness of the tape is controUed by the sHp characteristics, the height of the doctor blade, the casting rate, and the pressure head of the sHp reservoir behind the doctor blade. SHp viscosities in the range of 1 5 Pa-s (10—50 P) are used to cast tapes at 5—100 cm/s. To achieve the desired strength and flexibUity in the green tape, tape casting slurries contain more binder than those used in sHp casting, as weU as a plasticizer to ensure flexibUity. 

As mentioned in the previous paragraph, binder and plasticizer concentrations for tape casting are much higher than for slip casting and for most other types of slurry... 

Table 7.9 Composition of Some Nonaqueous Tape Casting Slurries...

It is also possible to retain the hydrothermally produced barium titanate particles in aqueous suspension to form the basis of a tape-casting slurry capable of producing < 3 /mi dielectric layers. This route avoids the risk of the formation of hard agglomerates on drying the precipitates. 

As an example the electrolyte may be tape-cast or calendered. Flat and dense plates of YSZ having thickness down to 150 /mi are readily fabricated. The anode and cathode materials can then be applied (by a slurry) to the faces of the electrolyte and fired on. Alternatively the anode, electrolyte and cathode layers... 

The conventional way to obtain ceramic microstructures is to prepare a feedstock or a slurry, fluid or plastic molding, injection molding or casting (CIM, HPIM and tape casting), demolding, debinding and sintering. Most ceramic materials will... 

Although tape casting is in many ways similar to slip casting, there are a few important differences. Since the goal is to produce thin—in some cases, extremely thin—sheets, the particulate or powder used to make up the slurry is typically finer than you would see in most slip-casting operations. Second, tape-casting processes typically utilize a nonporous substrate. This necessitates... 

A major difference between the two methods is the process by which the liquid is removed from the slurry. In slip casting, the liquid is removed by capillary suction provided by a porous mold. In contrast, the liquid is removed by evaporation in tape casting. In most tape casting processes, the liquid is nonaqueous because the higher volatility allows faster evaporation. 

Fig. 6 Schematic of a tape casting process used to form thin sheets of ceramic material. The slurry of ceramic particles and carrier fluid flows beneath the doctor blade onto a moving carrier film. As the tape moves down the bed, it dries and is then spooled on a take up reel.

---