Preparation of Fuctinally Graded Materials in high Energy Field of Plasma

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Functionally graded materials (FGM) are new concept of materials, and formed by the combination of metalceramics, metal-polymer and ceramics-polymer. General methods of the preperation of FGM has not been established, bacause the sintering temperature of ceramic, metal and polymer powders is different. A spark plasma sintering equipment (SPS) is a sort of a hot-press. Powders are put in a graphite die, and set in the SPS equipment. The graphite die is heated by direct pulse current. The pulse current generates plasma around powders in the graphite die. New die, New die, of which diameter is different between an upper part and a lower part, has been made. This die leads to graded temperatures and makes it possible to prepare various kinds of FGM.1.Polyimide/metal (Al and Cu) FGM : The polyimide is a excellent heat-resisting polymer. This polymer is used for an IC package and base. The combination of the polymer and metals (Al and Cu) offers the material of which one side is an insulator … More and other side is conductive. The dense polyimide/Al or Cu FGM can be obtained by spark plasma sintering. Residual stress is relaxd by the three graded layrs of the different ratio of polyimide and the metal.2.ZrO_2(3Y)/metals (Ni and stainless steel) FGM : Ceramic materials are brittle, heat-resisting and oxidation-resisting. Matals are ductile, but they melt and are oxidized at high temperatures. The combination of the ceramics and metals give a good heat-resisting material that can be used in air at high temperature. The dense ZrO_2 (3Y)/metals (Ni and stainless steel) were prepared using the spark plasma sintering equipment. The residual stress is relaxd by ten graded layrs of the different ratio of ZrO_2 (3Y) and the metal.3.Residual stress in FGM : The residual stress comes from the mismatch of the thermal expansion of the polymer, metal and the ceramics. The concept of FGM is the fact that the graded layrs of the different ratio of powders can relax the residual stress. The reasidual strss of the polyimide/metal FGM is relaxd by the plastic deformation of polymers and metals. The combination of ceramics and metals can not afford enough relaxation. That is why the ten layrs are needed between the ceramic and metal layrs.4. High voltage spark plasma sintering apparatus : Plasma is generated around powders in the graphite die. The energy of the spark plasma sintering equipment is low and not enough to create high performing FGM.The apparatus that could be used under the condition of high voltage was made to increase the energy of the plasma. This is effective for the FGM formation. Less