Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,400,000 (Direct Cost: ¥1,400,000)
|
Research Abstract |
Thermal expansions of ordinary ceramics are generally lower than those of metals. So, in composite materials composed of ceramic and metal, a stree is developed by the thermal expansion mismatch, and then the composite sometimes breaks up. In order to avoid thisfailure, there is a new technique to use functionally gradient materials (FGM), which is characterized by the material having a continuously varying property from one surface to the other. Such a material is prepared by forming a pile of composite layrs composed of ceramic and metal having the pre-determined compositional distribution. In this study, a FGM was prepared by forming a series of solid solutions in a single ceramic body. First, a FGM with respect to thermal expansion was prepared from nepheline solid solutions (Na_<1-x>M_xAlSiO_4 : M=Li and K). By sintering green-compact layrs composed of NaAlSiO_4 powder and {(1-x)NaAlSiO_4 + xMAlSiO_4 (M=Li and K)} mixed powder, they bonded together to form a gradient solid solution, which compositon continuously varied with the distance from the interface. Nepheline solid solutions had high thermal expansion coefficients equal to those of metals. The thermal expansion coefficient decreased from 1.6x10^<-5>/゚C for x=0 to 1.2x10^<-5>/゚C for x=0.15 in Na_<1-x>Li_xAlSiO_4, and increased to 1.8x10^<-5>/゚C for x=0.43 in Na_<1-x>K_xAlSiO_4 with increasing x. Consequently, the thermal expansion coefficient of the gradient solid solutions should gradually vary with position according to the composition of solid solution. Second, a FGM with respect to electrical properties was investigated. A series of PbZr_xTi_<1-x>O_3 solid solutions was formed in a single ceramic body by sintering layred compacts of PZT (A) and PZT (B) in contact with each other, where Zr and Ti diffused each other. The dependence of dielectric constant on temperature decreased for the sample with gradient solid solution.
|