Sintering example

This represents a threefold decrease in area, the same decrease as in the vacuum sintering example above. However, in this case of steam sintering, the pore volume does not change and, consequently, there is a threefold increase in pore width. 

Slip-cast A suspension of particles (the slip) that is formed into a shape, such as a plate or a ribbon, before solidification. The solidified slip is then fired to drive off volatile materials and bond the particles together by fusion and/or sintering. Example Slip-cast alumina. 

VoIa.tiIes. Manganese may contain some chemically bonded water or carbon dioxide both of which can be removed by calcining or sintering. The Mexican Molango ore (Table 4) is an example of a low grade ore that is upgraded by calcination in a rotary kiln. 

Friction Materials. Sintered friction materials are classified as metal— nonmetal combinations (49,50). These are best manufactured by the P/M process. Clutch plates, brake bands, brake blocks, and packing compositions are examples of friction materials (see Brake linings and clutch facings). 

Nuclear Applications. Powder metallurgy is used in the fabrication of fuel elements as well as control, shielding, moderator, and other components of nuclear-power reactors (63) (see Nuclearreactors). The materials for fuel, moderator, and control parts of a reactor are thermodynamically unstable if heated to melting temperatures. These same materials are stable under P/M process conditions. It is possible, for example, to incorporate uranium or ceramic compounds in a metallic matrix, or to produce parts that are similar in the size and shape desired without effecting drastic changes in either the stmcture or surface conditions. OnlyHttle post-sintering treatment is necessary. 

In another example, Ti02 can be deposited on a siHca support body in order to obtain a stable high surface titania. This is necessary because Ti02 sinters badly on heating in the bulk oxide and loses surface area. The Ti02 Si02 combination is useful as a catalyst for the oxidation of o-xylene to phthaHc anhydride. 

In soHd-state sintering (29,68,78—81) densification occurs by soHd-state diffusion-controUed material support. Examples of two technologically important ceramics that density by soHd-state sintering are MgO-doped AI2O2 and Y202-stabili2ed Zr02-... 

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