Ceramic oxides after sintering

Figure 7. Effect of sintering time and temperature on fired density of pellets made from typical ceramic-grade oxide. (After Ref. 3.)...

The sintering of pressed oxides to form dense ceramics occurs at much lower temperature than that in the case of oxides obtained by conventional methods, due to their small particle size and uniform distribution. At the same time, using nanosized oxide powders the ultrafine grain size is retained after sintering close to theoretical density, conveying superior properties to the obtained ceramics. 

Many kinds of artificial hip joints are available commercially, but they all consist of the same parts, i.e. a metal stem or shaft, usually made of a titanium alloy and a ceramic head of aluminium or zirconium oxide. The production of the ceramic head starts with a powder and ends with the sintering process. The heat treatment will cause the head to shrink. After production, the head is thoroughly tested, e.g. on its spherical shape and surface roughness. 

Gas-solid reactive sintering can also be used in the oxidation of most metals or, more important, mixtures of metals. After oxidation, solid state sintering takes place. With mixtures of metals, a mixed oxide is produced which can be sintered by either solid state or liquid phase sintering. One example of alloy oxidation to produce a ceramic is in the synthesis of the superconductor YBa2Cu3Q. ... 

FIG. 176. Migration of boundaries and grain growth in sintered oxide ceramics (planar representation), after J. E. Burke. 

---