Page 155 - Module DMV20173

8.0 POWDER PROCESSING

8.3.4 ADDITIVIES

The ground particles are then mixed with additives—the functions of which are one or
more of the following:

a) Binder : for holding ceramic particles together.
b) Lubricant : to reduce internal friction between particles during moulding
and to help remove the part from the mould.
c) Wetting agent : to improve mixing.

d) Plasticizer : to make the mix more plastic and formable.
e) Agents : to control foaming and sintering.

8.3.5 FORMING AND SHAPING

1. Forming and shape processes transform the ceramic powders into a green
product.
2. Both processes involve with controlled size, surface quality, density and

microstructure.
3. Some of the major manufacturing methods to produce ceramic parts are slip
casting, extrusion, jiggering, pressing and injection moulding.
4. Table 8.2 shows he advantages and limitations of each process.

I) SLIP CASTING

1. The basic process of slip casting involves the suspension of a powder

material in a solution.
2. The powder and solution mixture (slip) are then cast into a mould .
3. The liquid then removes from the powder by capillary action or drain, leaving
the powder in the form of the mould.

4. This powder shape (green part) can then be removed from the mould and
sintered in an oven to give it strength.
5. Figure 8.5 shows the sequence of operations in slip-casting a ceramic part.

EXERCISE 8.2

State the similarities and differences between slip casting and metal casting.

BPLK 187 DMV 20173