Production techniques of functionally graded SiAION ceramics

Functionally graded SiAION ceramics can be produced by lamination (powder and tape), powder bed, controlling the sintering conditions, infiltration, slip casting and so on. Some of these production techniques will be discussed in the following sections. 

Lamination of green compacts or sheets, which are produced through the tape casting method, is a very important technique for graded material production. For this purpose, layers with different a (f SiAION ratio are used to obtain graded structures. Further details regarding these production techniques are given below. 

Prelamination of green compacts is a simple and well-established technique for graded material production.48 In the powder lamination method, FGM fabrication stages include compositional design, compaction of different powders, and sintering at suitable conditions. 

In compositional design of functionally graded SiAION ceramics, selection of cations and a P phase ratios are very important parameters. Type of cations affects the densification and diffusion between the layers. They also control the thermomechanical properties of SiAION ceramics. 

In the compaction stage, two or more different powder compositions are stacked by sequential filling of the die and uniaxially pressed in an automatic press. Packing of powders and grain size are effective parameters in controlling the composition and thus the properties. After compaction, the laminates are sintered to obtain a gradual structure. 

---